INVERTER SYSTEM ENABLING SELF-CONFIGURATION
BACKGROUND
Many micropower generation systems, such as those in the home, typically include one or more
of a number of solar cells, wind turbines, combined heat and power systems and other similar systems.
The micropower generation systems generate electricity. The generated electricity is converted into
useable voltage and current suitable for local consumption, for example 240V at 50Hz or 110V at 60Hz.
However, these micropower generation systems often generate more power than is actually needed for
local consumption. If the micropower generation systems were connected to the alternating current (AC)
gird, from which power is normally drawn, this surplus power could be sent back to the AC grid.
Micropower generation systems often include inverters that are used to generate an AC output
from a direct current (DC) input. The inverters are generally located within the proximity of the power
source (solar cells, wind turbine, etc.) and connected to the AC grid mains remotely. Among various
inverters, a solar inverter converts the variable DC output of a photovoltaic (PV) solar panel into a utility
frequency AC that can be fed into a commercial electrical grid or used by a local, off-grid electrical
network.
In recent years there has been a re-emergence of interest in module-integrated electronics. The
solar micro-inverter in particular has been noted as a product that has a number of benefits over the
existing conventional solutions. A solar micro-inverter converts DC electricity from a single solar panel
to AC. The electric power from several micro-inverters is combined and fed into an existing electrical
grid. Unlike conventional string inverter devices, each micro-inverter is connected to a single solar panel
rather than multiple solar panels.
The benefits of an energy harvesting system based on micro-inverters include: improved energy
harvest over the life of the installation, particularly in scenarios of shading or other causes of mismatch in
solar PV installations; and low voltage DC (less than 80V from a single panel), which is safer and
significantly reduces arcing faults. Additional benefits of an energy harvesting system based on microinverters
also include the ability to pinpoint failures or problems with solar panels (or solar modules), and
the scalability by adding panels to an installation. The installation process itself is also extremely easy and
can be considered as a plug and play method. Solar micro-inverters enable true plug and play installation
of solar PV modules. The ease with which these can be installed is a major selling point for the solar
industry. In the discussion that follows, the term "inverter" is used to describe all electrical power
converters that change DC to AC, including string inverters and micro-inverters.
Because the inverters are fed into an existing electrical grid, they have to conform to the grid
connection standard used by the local electrical grid. For example, the inverters must synchronize with
the frequency of the electrical grid, the AC current produced by the inverters must be within the required
voltage range of the grid, and so on. Different countries have different utility requirements. As a result,
inverters manufactured for different countries must be configured differently in order to function properly.
Currently, the inverters are configured in the factory, where they are manufactured and labeled.
This adds an extra step in the manufacturing process. Moreover, once the inverters are manufactured and
configured, they have to be managed separately for different countries or different grid connection
standards. The manufactured inverters usually do not go immediately from the factory to the end
customer. They are usually stored in several warehouses in different regions around the world, waiting to
be ordered and distributed. Figure 1 conceptually illustrates the current approach of manufacturing and
distributing inverters to different countries by configuring inverters at the factory. As shown in the figure,
a factory 105 manufactures and configures different inverters based on different grid connection standards
for different countries. The configured inverters are stored in two warehouses 110 and 115, and
distributed to five different countries, i.e., country 1-5.
The factory 105 produces and configures the inverters 1-5, each of which is configured to comply
with a particular grid connection standard of a particular country. For example, the inverter 1 is
configured to comply with the grid connection standard of country 1, the inverter 2 is configured to
comply with the grid connection standard of country 2, and so on. Once the inverters are produced and
configured in the factory 105, they are stored in warehouses 110 and 115. A warehouse stores several
different kinds of inverters. Each kind of inverter is configured for the grid connection standard of a
particular country. For example, warehouse 110 stores three different kinds of inverters, i.e., inverter 1-3
for country 1-3. The warehouse 115 stores three different kinds of inverters, i.e., inverter 3-5 for country
3-5. Inverters with the same configuration may be stored in different warehouses. For instance, inverter 3
is stored in both warehouses 110 and 115. The different kinds of inverters are distributed to their
corresponding countries when ordered by customers. For example, inverter 1 is distributed to country 1;
inverter 2 is distributed to country 2, and so on. Because the same kind of inverters may be stored in
different warehouses, a country may receive inverters configured to comply with its grid connection
standard from multiple warehouses. For instance, country 3 receives inverter 3 from both warehouses 110
and 115.
As illustrated in Figure 1, in order to ensure sufficient supply for each country and each grid
connection standard, the warehouses must carry a lot of different stocks and treat different inverters
differently based on demand forecasting and many other factors. When the manufacturer needs to supply
inverters to many different countries or different grid connection standards, the management of the
inventory and distribution of different inverters become very complicated.
SUMMARY
Some embodiments of the invention provide a method of configuring an installed energy
harvesting device to comply with a local grid connection standard. The method identifies a local grid
connection standard for an energy harvesting device that has been installed in a physical installation. The
method then configures the energy harvesting device to apply the identified grid connection standard.
To identify the local gird connection standard, the method of some embodiments determines a
physical location for the installation of the energy harvesting device. The method then identifies the local
grid connection standard based on the determined physical location.
To determine the physical location of an installed energy harvesting device, the method of some
embodiments utilizes a global positioning system (GPS) receiver equipped on the energy harvesting
device. In some embodiments, the physical location for the installed energy harvesting device is
determined by receiving a user input. In some embodiments, the method determines the physical location
of the installed energy harvesting device by receiving the physical location from a communication
gateway. Other embodiments determine the physical location of the installed energy harvesting device by
receiving the physical location from a handheld installation device located near the physical installation.
In some embodiments, the handheld installation device determines the physical location of the
installed energy harvesting device by using a GPS receiver equipped on the handheld device to identify
the physical location of the handheld device. The physical location of the handheld installation device is
then treated as the physical location of the installed energy harvesting device because they are located
physically near each other. In some embodiments, the handheld installation device identifies the physical
location of the installation by receiving a user input.
Instead of receiving a physical location of the installation, the method of some embodiments
receives a local grid connection standard from a handheld installation device located near the physical
installation of the energy harvesting device. The handheld installation device identifies the local grid
connection standard based on the physical location of the installation. In some embodiments, the physical
location of the installation is determined by receiving a user input on the handheld device. In other
embodiments, the installation location is determined by receiving a GPS coordinate through a GPS
receiver equipped on the handheld device.
The method of some embodiments receives the local grid connection standard from a
communication gateway that connects the installed energy harvesting devices to a communication
network. The communication gateway of some embodiments identifies the local grid connection standard
based on a physical location of the communication gateway determined by a set of networking parameters
of the communication network. The communication gateway then sends the identified grid connection
standard to the installed energy harvesting device. In some embodiments, the set of networking
parameters includes the Internet Protocol (IP) address of the communication gateway. The set of
networking parameters of some embodiments includes the location of the nearest Wi-Fi access point or
the location of the nearest cellular tower. In some embodiments, the local grid connection standard
identified by the communication gateway is confirmed by a user input before being sent to the installed
energy harvesting device.
In some embodiments, each energy-harvesting device includes an inverter for converting energy
from photovoltaic modules into AC output. The energy harvesting device of some embodiments includes
a power converter for convertering DC power from a photovoltaic device to AC electricity and a
controller for configuring the power converter based on a local grid connection standard after the energy
harvesting device has been installed. The controller of some embodiments includes at least one processor.
In some embodiments, the energy-harvesting device further incldues a GPS receiver for determining the
physical loaction of the installation. The controller then identifies the local grid connection standard based
on the physical location determined by the GPS receiver.
In some embodiments, the controller of the energy harvesting device identifies the local grid
connection standard through searching a data structure that contains information regarding all grid
connection standards. Different embodiments store the data structure differently. In some embodiments,
the data structure is stored on the energy harvesting device. In other embodiments, the data structure is
stored on another device and is accessable to the controller through a communication network. The data
structure of some embodiments is a grid connection standards lookup table. The grid connection standards
lookup table contains all the grid connection standards and the corresponding geographic regions for each
grid connection standard. In some embodiments, instead of identifying the grid connection standard by
itself, the controller of the energy harvesting device receives the appropriate grid connection standard
from a device outside of the energy harvesting device.
The energy harvesting device of some embodiments includes a communication module. In some
embodiments, the controller of the energy harvesting device uses the communication module to
communicate with other devices in a communication network. The energy harvesting device of some
embodiments is equipped with communications devices such as wireless transceivers as part of the
communication module. In some embodiments, instead of or in conjuction with using wireless
communication, the communication module uses the power line to communicate with other devices in the
communication network.
The preceding Summary is intended to serve as a brief introduction to some embodiments of the
invention. It is not meant to be an introduction or overview of all inventive subject matter disclosed in this
document. The Detailed Description that follows and the Drawings that are referred to in the Detailed
Description will further describe the embodiments described in the Summary as well as other
embodiments. Accordingly, to understand all the embodiments described by this document, a full review
of the Summary, Detailed Description and the Drawings is needed. Moreover, the claimed subject matters
are not to be limited by the illustrative details in the Summary, Detailed Description and the Drawing, but
rather are to be defined by the appended claims, because the claimed subject matters can be embodied in
other specific forms without departing from the spirit of the subject matters.
BRIEF DESCRIPTION OF THE DRAWINGS
The novel features of the invention are set forth in the appended claims. However, for purpose of
explanation, several embodiments of the invention are set forth in the following figures.
Figure 1 conceptually illustrates the current approach of manufacturing and distributing inverters
to different countries by configuring inverters at the factory.
Figure 2 conceptually illustrates a new approach of manufacturing and distributing inverters in
different countries by configuring the inverters after installation in some embodiments of the invention.
Figure 3 conceptually illustrates a typical installation for an array of inverters.
Figure 4 illustrates a block diagram of an inverter that can be used to implement the array of
inverters of Figure 3 .
Figure 5 conceptually illustrates an inverter configuration module of some embodiments.
Figure 6 conceptually illustrates a process performed by some embodiments to configure an
inverter to comply with an appropriate grid connection standard based on the installation location of the
inverter.
Figure 7 conceptually illustrates a process performed by some embodiments to configure a set of
installed inverters through a communication gateway.
Figure 8 conceptually illustrates an installation for an array of inverters that use equipped GPS
receivers to configure themselves in some embodiments of the invention.
Figure 9 conceptually illustrates using a handheld device to configure a set of installed inverters.
Figure 10 conceptually illustrates using a handheld device equipped with a GPS receiver to
configure a set of installed inverters.
Figure 11 conceptually illustrates a process performed by some embodiments to configure a set
of installed inverters by a handheld device to comply with an appropriate grid connection standard.
Figure 12 illustrates an example of a set of parameters included in a grid connection standard.
Figure 13 conceptually illustrates an electronic system with which some embodiments of the
invention are implemented.
DETAILED DESCRIPTION
In the following description, numerous details are set forth for the purpose of explanation.
However, one of ordinary skill in the art will realize that the invention may be practiced without the use
of these specific details. In other instances, well-known structures and devices are shown in block
diagram form in order not to obscure the description of the invention with unnecessary detail.
Some embodiments of the invention provide a method of configuring an installed energy
harvesting device to comply with a local grid connection standard. The method identifies a local grid
connection standard for an energy harvesting device that has been installed in a physical installation. The
method then configures the energy harvesting device to apply the identified grid connection standard.
To identify the local gird connection standard, some embodiments determine a physical location
for the installation of the energy harvesting device. These embodiments then identify the local grid
connection standard based on the determined physical location.
Figure 2 conceptually illustrates a new approach of manufacturing and distributing inverters to
different countries by configuring the inverters after installation in some embodiments of the invention.
As shown in the figure, because the inverters are configured at the field after installation, a factory 105
manufactures the same generic inverter 205 for all countries. The generic inverters 205 are stored in two
warehouses 110 and 115, and distributed to five different countries, i.e., country 1-5.
The factory 105 produces the generic inverter 205, each of which can be configured after
installation to comply with any grid connection standard of any country. Once the inverters are produced
in the factory 105, they are stored in warehouses 110 and 115. Each of the warehouses 110 and 115 stores
the same generic inverter 205. The same generic inverters 205 are distributed to different countries, e.g.,
country 1-5, when ordered by customers. Because the generic inverters 205 may be stored in different
warehouses, a country may receive inverters from multiple warehouses. For instance, countries 1-4
receive the generic inverter 205 from both warehouses 110 and 115.
The generic inverters 205 are distributed to different countries and installed at different locations.
Once installed at a particular location, the inverter is configured to comply with the local grid connection
standard in order to feed converted AC into the local power grid. As illustrated in Figure 2, because the
inverters are configured at the field after installation, it is possible to manufacture and distribute a generic
inverter that greatly simplifies the inventory and distribution management of the inverters.
Several more detailed embodiments of the generic inverter that is capable of being configured
after installation are described in the sections below. Section I describes a typical instllation of inverters.
Next, Section II describes configuring inverters after they have been installed. Section III describes
several examples of inverter configuration. Next, Section IV describes an example of grid connection
standard. Finally, Section V describes an electronic system that implements some embodiments of the
invention.
I. INSTALLATIONOF INVERTERS
Figure 3 conceptually illustrates a typical installation for an array of inverters. As shown in the
figure, an energy harvesting system 300 harvests solar power from photovoltaic cells in solar panels. The
harvested solar energy is converted into electricity via an array 330 of inverters 331-336, which are
coupled to the solar panels 341-346 and are installed on a roof of a building 305. The inverters in the
energy harvesting system 300 are also in a communication system 340 that includes a communication
gateway 310, which gathers information from the installed array of inverters 330. The information
gathered by the communication gateway 310 is then sent to a server 320 via a network such as the
Internet 315. In some embodiments, the communications gateway 310 gathers information from the
server 320 and/or the Internet 315 and sends the information to the installed array of inverters 330.
The communication system 340 communicatively couples the inverters in the array 330 with the
communication gateway 310 and allows information to be exchanged between devices in the
communication system 340. In some embodiments, the communication system 340 is a wireless
communication system. The communication system 340 can be implemented in any one of a number of
wireless communication systems such as ZigBee, Wi-Fi, Bluetooth, Wireless MBus, etc. Though not
illustrated, instead of or in addition to wireless systems, some embodiments use power line
communication, in which a data signal is modulated over a lower frequency carrier signal that is typical of
mains voltage.
The communication gateway 310 is the hub of the communication system 340. This is the case
whether the communication system 340 is a wireless system or a power line based system. The
communication gateway 310 is also referred to as the installation coordinator in some embodiments. The
communication gateway 310 receives communication from some or all of the installed inverters in the
system. In some embodiments, it also receives communications from anchor nodes (not illustrated).
Anchor nodes are inverters or installation devices with known positions that can be used to ascertain the
exact location of inverters. The communication gateway 310 also sends information to the array of
installed inverters 330. In some embodiments, the communication gateway 310 is equipped with
computing components capable of analyzing information gathered from the inverters and/or the anchor
nodes. The results of the analysis are then sent to the server 320. In some embodiments, the
communication gateway 310 is capable of analyzing information gathered from the server 320 and/or the
Internet 315. The results of the analysis are then sent to the array of installed inverters 330.
Because the communication gateway 310 is usually in close vicinity of the array of installed
inverters 330, some embodiments use the communication gateway 310 to determine the physical location
for the array of installed inverters 330. The communication gateway 310 can connect to the Internet 315
through many different communication systems. For example, the communication gateway 310 can
connect to the Internet 315 through an Ethernet, a Wi-Fi network, a GSM network, or some other
communication systems. The communication gateway 310 is able to determine its physical location
through a set of parameters from the communication system that connects it to the Internet 315. For
instance, the communication gateway 310 is able to determine its physical location by the Internet
Protocol (IP) address associated with it in some embodiments. The communication gateway 3 10 of some
embodiments determines its physical location through locating the nearest Wi-Fi access point or the
nearest cellular tower, depending on the type of communication system that connects it to the Internet 315.
For each determined physical location, there is a corresponding grid connection standard that
needs to be complied with by the inverters in order to feed the generated AC into the local power grid. In
some embodiments, the communication gateway 310 retrieves the appropriate grid connection standard
based on the determined physical location and sends the grid connection standard to the array of installed
inverters 330. In some other embodiments, the communication gateway 310 sends the determined
physical location to the array of inverters 330 and lets each inverter to figure out applicable grid
connection standard.
The server 320 receives data gathered or generated by the communication gateway 310. The
server 320 also receives data request from the communication gateway 3 10 and sends the requested data
to the communication gateway. Figure 3 illustrates the server 320 as being accessible by the
communication gateway 310 via the Internet 315. In some other embodiments (not illustrated), the server
is accessible to the communication gateway 310 by other means. For example, the server 320 can be
connected to the communication gateway via local area network, via wired or wireless network. The
server 320 and the communication gateway 310 can also reside on the same computing device that
performs the functions of both the server 320 and the communication gateway 3 10. In some embodiments,
the database storage 325 resides on the server 320. In other embodiments, the database storage 325
resides on a computing device separate from the server 320. The database storage 325 stores the data
collected from individual inverters, as well as other relevant data, e.g., a grid connection standards lookup
table. In some embodiments, the server 320 is part of a device (e.g., a computing device with display
capabilities) that allows the viewing of the data collected from the inverters at the server 320. In some
embodiments, the collected data is pushed up to a website or another server, which allows end users to
view the data.
The inverters in the array 330 such as inverters 331-336 receive DC voltage generated by the
solar photovoltaic panels and converts the received DC voltage into AC electricity. Descriptions of
inverters can be found in U.S. Patent Application No. 13/244,155, now published as U.S. Publication No.
2012/0057388, and U.S. Patent Application No. 13/244,161, and now published as U.S. Publication No.
2012/0063177. U.S. Publication No. 2012/0057388 and U.S. Publication No. 2012/0063177 are hereby
incorporated by reference. In addition to the components necessary for converting DC voltage from solar
panels to AC electricity, the inverters also include the components necessary for communications within
the communication network 340. In some embodiments, the communication components residing within
the inverters (e.g., 331-336) are radio frequency (RF) circuitry for wireless communications with the
communication gateway 310. In some embodiments, components for other means of communications
(e.g., power line communications) are included.
In addition to using the wireless/RF system for communications, some embodiments also use the
RF circuitry of the inverters for ascertaining the location, or positioning of the inverters. In addition to
sending information of its own position, an inverter in some embodiments also sends a unique
identification (e.g., a serial number) to the server 320 via the communication gateway 310. In some
embodiments, each inverter of the array 330 receives a grid connection standard from the communication
gateway 310 or a handheld device (not illustrated) and configures itself according to the grid connection
standard in order to feed generated AC power into the local power grid. In some embodiments, each
inverter receives a physical location from the communication gateway 310 or a handheld device (not
illustrated) and find out the applicable grid connection standard based on the physical location by itself. In
some embodiments, each inverter of the array 330 contains a global positioning system (GPS) receiver
and determines its physical location based on a GPS coordinate obtained by the GPS receiver. The
inverter then identifies applicable grid connection standard and configure itself accordingly. An example
inverter will be described below by reference to Figure 4 .
The GPS is a global navigation satellite system (GNSS) that provides reliable location and time
information in all conditions at all times and from anywhere on Earth. In some embodiments, each anchor
node includes a GPS chip. In some embodiments, each inverter includes a GPS chip as well. The exact
positions of the installed inverters can be exactly ascertained based on coordinates provided by the GPS
chips in the inverters.
The server 320 includes the storage 325, which is used to store data collected from individual
inverters and anchor nodes, as well as other relevant data, e.g., a grid connection standards lookup table.
A computing device having access to the storage 325 can use the collected data to evaluate status of the
inverters and perform other analysis or operations. For example, a computing device having access to the
storage 325 can search for an appropriate grid connection standard for a particular location. In some
embodiments, such a computing device is part of the server 320. In some embodiments, another computer
separate from the server 320 performs the analysis. Such a computer can be a computer in real-time
communication with the communications system 340 (e.g., being in a same network) such that the
computer can perform the analysis in real-time. Alternatively, such a computer can receive the
information from the storage 325 at a later time via storage mediums such as flash drives. In addition to
collecting information about inverters, some embodiments gather information about other components
such as power optimizers in the solar modules. The information of these other components is also
included in the analysis performed by the server 320 or other computers.
II. CONFIGURING INVERTERS AFTER INSTALLATION
Figure 4 illustrates a block diagram of an inverter 400 that can be used to implement the array of
inverters 330 of Figure 3 (i.e., each of the inverters 331-336 can be implemented based on the inverter
400). The inverter 400 converts DC voltage generated by photovoltaic cells 460 into AC electricity for
power grid 470. The inverter 400 also includes components necessary for configuring itself to comply
with a local grid connection standard and/or for communications within a communication network. The
inverter 400 includes a processor 410, a transceiver(s) 415, an antenna 490, a signal strength sensor 417, a
read-only memory (ROM) 412, a random-access memory (RAM) 413, a serial number 420, a real-time
clock 430, a GPS receiver 440, and a power converter 450.
The power converter 450 converts the DC voltage received from the photovoltaic cell 460 to AC
electricity for the power grid 470. In some embodiments, power converters are also referred to as power
conditioning units. Descriptions of power converters or power conditioning units can be found in U.S.
Patent Application No. 13/244,155, now published as U.S. Publication No. 2012/0057388, U.S. Patent
Application No. 13/244,161, now published as U.S. Publication No. 2012/0063177, and U.S. Patent
Application 13/310,691, now published as U.S. Publication No. 2012-0098346. In some embodiments,
various components in the inverter 400 (e.g., the processor 410 and the RF transceiver 415) are powered
by energy from the photovoltaic cell 460. In some of these embodiments, the solar power is provided via
the power converter 450.
Some of the operations performed by the power converter 450 are monitored and controlled by
the processor 410. In some embodiments, the power converter 450 includes its own micro-controller(s)
(not illustrated) for controlling the transfer of power from the PV cell 460 to the power grid 470 (e.g., by
controlling the transistor drivers in the power converter 450), and the processor 410 monitors and controls
the power converter 450 by communicating with the micro-controller(s) in the power converter 450. In
some other embodiments, the transfer of power in the power converter 450 is controlled by a micro
controller (or processor) that also controls the communications of the micro-inverter 400.
In some embodiments, the processor 410 controls the operations performed by the power
converter 450 based on a set of parameters stored in the ROM 412. The set of parameters determines how
the power converter 450 should behave in converting power from DC to AC. The power converter 450
performs different operations under the control of the processor 410 when the set of parameters stored in
the ROM 412 are different. For example, the power converter 450 complies with different grid connection
standards when the set of parameters are set at different values. This enables the inverter 400 to be
configured after installation by changing the set of parameters stored in the ROM 412. In some
embodiments, the micro-controller(s) (not illustrated) in the power converter 450 accesses the set of
parameters stored in the ROM 412 in order to control the operations performed by the power converter
450. For example, the micro-controller(s) use the set of parameters to control the transistor drivers in the
power converter 450 differently in order to comply with local grid connection standard. In some
embodiments, the ROM 412 is part of the power converter 450.
In some embodiments, the processor 410 controls the operations performed by the power
converter 450 by executing a set of instructions stored in the ROM 412. The set of instructions determines
how the power converter 450 should behave in converting power from DC to AC. The power converter
450 performs different operations under the control of the processor 410 when the set of instructions
stored in the ROM 412 are different. For example, the power converter 450 complies with different grid
connection standards when the set of instructions stored in the ROM 412 are different. This enables the
inverter 400 to be configured after installation by changing the set of instructions stored in the ROM 412.
In some embodiments, the micro-controller(s) (not illustrated) in the power converter 450 executes the set
of instructions stored in the ROM 412 in order to control the operations performed by the power converter
450. For example, the micro-controller(s) execute the set of instructions to control the transistor drivers in
the power converter 450 in order to comply with local grid connection standard. The RAM 413 allows the
processor 410 to access certain frequent used data quickly in any random order.
The RF transceiver 415 transmits and receives RF signals to and from one or more other RF
capable devices via the antenna 490. In the example of Figure 3, the RF transceivers in the inverters 331-
336 transmit and receive RF signals to and from the communications gateway 310. In some embodiments,
the RF transceivers in the micro-inverters 331-336 transmit and receive RF signals to and from other
micro-inverters in the array 330 in a mesh-like manner. In some embodiments, the RF transceivers 415
transmit and receive RF signals to and from anchor nodes for ascertaining the position of the microinverter
400. In some embodiments, the RF transceiver 415 includes multiple RF transceivers for
transmitting and receiving RF signals to and from multiple RF capable devices simultaneously.
In some embodiments, the RF transceiver 415 is used to communicate and exchange data with
other devices in a RF communications network (e.g., the communication network 340) via the RF signals
being received. In some of these embodiments, the inverters 331-336 communicate with the
communication gateway 310 and/or other inverters in the array 330. In some other embodiments, the RF
receiver 415 is only used for determining the position of the inverter 400 but not for communications. In
some of these embodiments, the inverter 400 includes one or more communications components (such as
for performing power line communications) for sending and receiving data.
The signal strength sensor 417 measures the strength of the RF signal received by the RF
transceiver 415. The signal strengths detected by the signal strength sensors in individual inverters are
used by some embodiments to determine the position of the inverters. In some embodiments, the inverter
400 performs received signal strength indicator (RSSI) and/or link quality indicator (LQI) measurement
based on the RF signal received. In some of these embodiments, the signal strength sensor 400 provides
raw measurements to the processor 410 to compute RSSI or LQI values. In some other embodiments, the
inverter 400 does not include the signal strength sensor 417, and the processor 410 computes the RSSI or
LQI readings directly based on the data received by the RF transceiver 415.
The processor 410 controls the communication between the inverter 400 and other devices. The
processor 410 receives demodulated data from the RF transceiver 415. The processor 410 also produces
data to be modulated and transmitted by the RF transceiver 415. In addition to processing data being
transmitted or received by the RF transceiver 415, the processor 410 also receives readings provided by
the signal strength sensor 417, the real-time clock 430, the GPS receiver 440, and the serial number 420.
The content of the real-time clock 430 in some embodiments can be updated by the processor 410 based
on the communications with other devices. The processor 410 produces the transmit data for the RF
transceiver 415 based on some or all of these readings. In some embodiments that do not use the RF
transceiver for data communications, the processor 410 goes through another communications component
(e.g., a module for power line communications, not illustrated) for transmitting and receiving data.
In some embodiments, the processor 410 is a microprocessor that executes a set of instructions
for producing the transmit data for the RF transceiver 415. For example, in some embodiments, the
processor 410 composes data packets to be transmitted by the RF transceiver 415 based on previously
received data, the real-time clock (430), the serial number (420), the GPS coordinates (440), and the
signal strength sensor reading (417). By receiving and transmitting these data, the inverter 400 enables the
energy harvesting system that includes the inverter to automatically determine its location and identify an
appropriate grid connection standard to configure the inverter.
In some embodiments, the processor 410 also controls and monitors the power converter 450. The
processor 410 communicates with the power converter 450 and relays its status to other devices (e.g., the
communication gateway 310) via the RF transceiver 415. In some other embodiments, the power transfer
operation and the communication operation are performed by a single micro-controller or microprocessor.
One of ordinary skill in the art will recognize that the diagram in Figure 4 is a conceptual
representation of the components of an inverter. The components in a specific inverter may not be exactly
the same as illustrated in this figure. For example, an inverter may not be equipped with the GPS receiver
440 and the processor 410 could be an integrated part of the power converter 450.
Figure 5 conceptually illustrates an inverter configuration module 500 of some embodiments.
Specifically, the figure illustrates an example of configuring an inverter to comply with a grid connection
standard based on the installation location of the inverter. In some embodiments, the inverter
configuration module 500 is a stand-alone software application, while in other embodiments the inverter
configuration module 500 is part of an inverter operation control application. As shown, this figure
illustrates a location identifier 510, a grid connection standard identifier 520, a grid connection standards
lookup table 525, and a configuration manager 530.
The location identifier 510 determines the installation location of the inverter and sends the
location information 515 to the grid connection standard identifier 520. In some embodiments, the
location identifier 510 receives the installation location through a user interface 511. The user interface
511 receives the installation location through user input and sends the location to the location identifier
510. In some embodiments, the location identifier 510 validates the user input and/or converts the user
input to a standard form before sending the location information 515 to the grid connection standard
identifier 520. In some embodiments, the location identifier 5 10 receives the installation location through
a GPS receiver 512. The GPS receiver 512 receives a GPS signal that identifies the installation location
and forwards the location to the location identifier 510. In some embodiments, the location identifier 510
receives the installation location through a network interface 513. The network interface 513 connects the
location identifier 510 to a communication network, e.g., the commutation network 340 described above
by reference to Figure 3 . As a result, the location identifier 510 is able to obtain the installation location
from other devices in the communication network, e.g., the communication gateway 310 described above
by reference to Figure 3, or a handheld installation device located nearby.
The communication gateway is able to determine its location through its connection to the
Internet. Since the communication gateway is always in close vicinity of the installed array of inverters,
the location of the communication gateway can be treated as the location of the installed inverters. In
some embodiments, a handheld installation device is connected to each inverter in the array of installed
inverters through a wired connection or a short-range wireless connection. A user may input the
installation location through the handheld installation device. That installation location is then transmitted
to each installed inverter. The handheld installation device of some embodiments is equipped with a GPS
receiver and can determine the current location of the handheld device through the GPS receiver. That
location is then transmitted to each installed inverter as the installation location of the inverter since the
handheld device is in close vicinity of the installed inverters.
In some embodiments, the location identifier 510 uses a combination of two or more approaches
to identify the installation location. For example, the location identifier 510 may receive an installation
location identified by the communication gateway through the network interface 513 and confirm the
location with user input received from the user interface 511.
The grid connection standard identifier 520 receives the location information 515 from the
location identifier 510 and sends a grid connection standard 522 to the configuration manager 530. The
grid connection standard identifier 520 identifies the grid connection standard 522 based on the received
location information 515. In some embodiments, the grid connection standard identifier 520 queries the
grid connection standards lookup table 525 in order to find the applicable grid connection standard for a
particular location. The grid connection standards lookup table 525 contains all the grid connection
standards and the corresponding geographic regions for each grid connection standard. In some
embodiments, the grid connection standards lookup table 525 is located within the inverter. In other
embodiments, the grid connection standards lookup table 525 is on a device separated from the inverter
and the grid connection standard identifier 520 uses a communication network to communicate with that
device in order to query the grid connection standards lookup table 525.
The configuration manager 530 receives the grid connection standard 522 and configures the
inverter accordingly. In some embodiments, the configuration manager 530 stores the grid connection
standard 522 as a set of parameters in a non-volatile memory (e.g., the ROM 412 as described above by
reference to Figure 4) of the inverter and a controller (e.g., the processor 410 as described above by
reference to Figure 4) configures the power converting component (e.g., the power converter 450 as
described above by reference to Figure 4) based on that set of parameters. In some embodiments, the
configuration manager 530 loads a unique set of instructions for each different grid connection standard
for executing by the controller or processor of the inverter.
An example operation of the inverter configuration module 500 will now be described by
reference to Figure 6 . Figure 6 conceptually illustrates a process 600 performed by some embodiments to
configure an inverter to comply with an appropriate grid connection standard based on the installation
location of the inverter. In some embodiments, the process 600 starts automatically when the inverter is
installed and connected to a power line. In some embodiments, the process 600 starts when the inverter
receives a command to start configuration.
As shown in the figure, the process determines (at 610) a location for the installed inverter. As
described above by reference to Figure 5, the installation location can be determined by receiving a user
inputted location through a user interface, by receiving a GPS signal that indicates the location of the
inverter through a GPS receiver within the inverter, or by receiving a location through a network interface
of a communication network. The location received through the network interface comes from another
device in the communication network, e.g., the communication gateway 310 described above by reference
to Figure 3, or a handheld installation device located nearby. The communication gateway is able to
determine its location through its connection to the Internet. Since the communication gateway is always
in close vicinity of the installed inverter, the location of the communication gateway can be treated as the
location of the inverter.
In some embodiments, the handheld installation device is connected to the inverter through a
wired connection or a short-range wireless connection. A user may input the installation location through
the handheld installation device. The handheld installation device of some embodiments is equipped with
a GPS receiver and can determine the current location of the handheld device through the GPS receiver.
That location is then transmitted to the inverter as the installation location of the inverter.
After determining the installation location for the inverter, the process 600 then identifies (at 615)
a grid connection standard based on the determined location. In some embodiments, the process 600
queries a grid connection standards lookup table in order to find the applicable grid connection standard
for the determined location. The grid connection standards lookup table contains all the grid connection
standards and the corresponding geographic regions for each grid connection standard. In some
embodiments, the grid connection standards lookup table is located within the inverter. In other
embodiments, the grid connection standards lookup table is on a device separated from the inverter and
the process 600 query the grid connection standards lookup table through a communication network.
Next, the process 600 configures (at 620) the inverter based on the identified grid connection
standard. In some embodiments, the process 600 stores the identified grid connection standard as a set of
parameters in a non-volatile memory (e.g., the ROM 412 as described above by reference to Figure 4) of
the inverter to enable a processer or controller of the inverter to configure the power converting
component (e.g., the power converter 450 as described above by reference to Figure 4) based on the set
of parameters. In some embodiments, the process 600 loads a unique set of instructions for the identified
grid connection standard for executing by the controller or processer of the inverter. The process 600 then
terminates.
One of ordinary skill in the art will recognize that the process 600 is a conceptual representation
of the operations used to configure an inverter to comply with an appropriate grid connection standard
based on the installation location of the inverter. The specific operations may not be performed in one
continuous series of operations, and different specific operations may be performed in different
embodiments. Furthermore, the process could be implemented using several sub-processes, or as part of a
larger macro process. For instance, in some embodiments, the process 600 is performed by one or more
software applications that execute on one or more devices.
III. INVERTER CONFIGURATION EXAMPLES
Different embodiments use different approaches to configure an inverter after installation. For
example, some embodiments configure an array of inverters installed in the same installation based on a
grid connection standard identified by a communication gateway of the installation. In some embodiments,
an installer configures an array of installed inverters by pushing configuration data to each inverter using
a handheld device connected to the inverter through a wired connection or a short-range wireless
connection. In some of these embodiments, the configuration data includes location information. In other
embodiments, the configuration data includes a grid connection standard. The location information is
provided by the installer's manual input or by a GPS receiver within the handheld device in some
embodiments. In some other embodiments, the configuration data includes a grid connection standard.
Several detailed examples of inverter configuration will be described below by reference to Figures 7-11.
A. Configuring Inverters Through A Communication Gateway
Figure 7 conceptually illustrates a process 700 performed by some embodiments to configure a
set of installed inverters through a communication gateway. Details of a communication gateway are
described above by reference to Figure 3 . In some embodiments, the process 700 starts automatically
when the set of installed inverter is connected to a communication gateway. In some embodiments, the
process 700 starts when the communication gateway receives a command to start configuration. As
shown in Figure 7, the process 700 determines (at 705) a location of installation for a set of installed
inverters based on a set of network connection parameters. In some embodiments, the set of network
connection parameters is determined by the physical location of the communication gateway, because the
communication gateway is physically close to the installed inverters and its location can be used as the
installation location of the installed inverters.
The communication gateway can connect to the Internet through many different communication
systems. For example, the communication gateway can connect to the Internet through an Ethernet, a Wi-
Fi network, a GSM network, or some other communication systems. In some embodiments, the
communication gateway determines its physical location through a set of parameters associated with the
communication system that connects it to the Internet. For instance, the communication gateway in some
embodiments determines its own physical location by its assigned IP address in the Internet. In some
embodiments, the communication gateway determines its own physical location based on the location of
the nearest Wi-Fi access point or the nearest cellular tower.
The process 700 then identifies (at 710) a grid connection standard for the determined physical
location. In some embodiments, the process 700 queries a grid connection standards lookup table in order
to find the applicable grid connection standard for the determined location. The grid connection standards
lookup table contains all the grid connection standards and the corresponding geographic regions that
utilize each grid connection standard. In some embodiments, the grid connection standards lookup table is
located within the communication gateway. In some other embodiments, the grid connection standards
lookup table is stored in a device separated from the communication gateway and the process 700 query
the grid connection standards lookup table through a communication network.
Next, the process 700 selects (at 715) an inverter from the set of inverters. The process 700 then
sends (at 720) the identified grid connection standard to the selected inverter in order to configure the
inverter based on the grid connection standard. In some embodiments, the inverter stores the grid
connection standard as a set of parameters in a non-volatile memory of the inverter and a controller
configures the power converting component of the inverter based on that stored set of parameters. In
some embodiments, the inverter loads a unique set of instructions for the grid connection standard for
execution by a controller or processor of the inverter.
The process 700 then determines (at 725) whether there are more inverters that need to be
configured. When there is at least one more inverter that needs to be configured, the process 700 loops
back to 715 and selects another inverter from the set of inverters. When the process 700 determines (at
725) that there is no more inverter that needs to be configured, the process terminates.
One of ordinary skill in the art will recognize that the process 700 is a conceptual representation
of the operations used to configure installed inverters through a communication gateway. The specific
operations of the process 700 may not be performed in the exact order shown and described. The specific
operations may not be performed in one continuous series of operations, and different specific operations
may be performed in different embodiments. Furthermore, the process could be implemented using
several sub-processes, or as part of a larger macro process. For instance, in some embodiments, the
process 700 is performed by one or more software applications that execute on one or more computers. In
some embodiments, the communication gateway sends the identified grid connection standard to multiple
inverters at the same time rather than sending it one by one. The process of some embodiments sends the
determined location of the communication gateway to the inverters and let each inverter to figure out the
applicable grid connection standard.
B. Configuring Inverter Through Equipped GPS Receiver
In some embodiments, the communication gateway has no Internet connection and an installed
inverter has to configure itself by using its own equipped GPS receiver.
Figure 8 conceptually illustrates an installation for an array of inverters that use equipped GPS
receivers to configure themselves in some embodiments of the invention. As shown in the figure, an
energy harvesting system 800 harvests solar power from photovoltaic cells in solar panels. The harvested
solar energy is converted into electricity via an array 830 of inverters, which are coupled to the solar
panels and are installed on a roof of a building 805.
The inverters in the array 330 such as inverters 331-336 receive DC voltage generated by the
solar photovoltaic panels and convert the received DC voltage into AC electricity. Descriptions of
inverters can be found in the above mentioned U.S. Patent Application No. 13/244,155, now published as
U.S. Publication No. 2012/0057388, and U.S. Patent Application No. 13/244,161, and now published as
U.S. Publication No. 2012/0063177.
For each determined physical location, there is a corresponding grid connection standard that
needs to be complied with by the inverters in order to feed the generated AC into the local power grid. In
some embodiments, each inverter of the array 330 is equipped with a global positioning system (GPS)
receiver (such as GPS receivers 85 1-856) and determines its physical location based on a GPS coordinate
obtained by the GPS receiver. The inverter then identifies applicable grid connection standard based on
the physical location obtained through the GPS receiver. The inverter then configures itself according to
the identified local grid connection standard.
C. Manual Configuration
In some embodiments, the communication gateway is not connected to the Internet and the
inverters are not equipped with GPS receivers. In some of these embodiments, an installer manually
configures a set of installed inverters by pushing configuration data to each inverter using a handheld
device. The handheld device connects to each inverter through a wired connection or a short-range
wireless connection. Figure 9 conceptually illustrates using a handheld device to configure a set of
installed inverters. Specifically, this figure illustrates an installer 901 carrying a handheld device (e.g., a
mobile device) 920 that is used as an installation or monitoring device for the inverters. As shown, the
figure illustrates an array 930 of inverters is installed on the building 905 and an installer 901 carrying a
handheld device 920 is configuring the array of inverters. The array of inverters 930 includes six inverters
931-936.
The installer 901 carries the handheld device 920 near the inverters in the array 930. The
handheld device 920 connects to each inverter in the array 930 through a short-range wireless connection
(e.g., Wi-Fi or Bluetooth) or a wired connection. In some embodiments, the installer 901 manually input a
location into the handheld device 920. The handheld device 920 then identifies a corresponding grid
connection standard for the location and sends the grid connection standard to each inverter in the array
930. Each inverter in the array 930 configures itself to comply with the grid connection standard in order
to feed its generated power into the local power grid. In some embodiments, the handheld device 920
simply sends the inputted location to each inverter in the array 930 and let each inverter to figure out the
appropriate grid connection standard by itself. Each inverter in the array 930 then configures itself to
comply with the grid connection standard in order to feed generated power into the local power grid.
Figure 10 conceptually illustrates using a handheld device equipped with a GPS receiver to
configure a set of installed inverters. Specifically, this figure illustrates an installer 901 carrying a
handheld device 920 equipped with a GPS receiver 1010 to configure the inverters. As shown, the figure
illustrates an array of inverters 930 installed on the building 905. An installer 901 is carrying a handheld
device 920 and configuring the array of inverters 930. The array of inverters 930 includes inverters 931-
936. The handheld device 920 includes a GPS receiver 1010.
The installer 901 carries the handheld device 920 near each of the inverter in the array 930. The
handheld device 920 connects to each inverter in the array 930 through a short-range wireless connection
(e.g., Wi-Fi or Bluetooth) or a wired connection. Instead of manually inputting a location into the
handheld device 920, the GPS reading of the GPS receiver 1010 determines the location of the handhold
device 920. The handheld device 920 is physically close enough to the array of inverters 930 such that the
location of the handheld device 920 represents the location of the array of inverters 930.
In some embodiments, the handheld device 920 identifies a corresponding grid connection
standard for the determined location and sends the grid connection standard to each inverter in the array
930. Each inverter in the array 930 then configures itself to comply with the grid connection standard in
order to feed its generated power into the local power grid. In some embodiments, the handheld device
920 simply sends the location detected by the GPS receiver 1010 to each inverter in the array 930 and let
each inverter to figure out the appropriate grid connection standard by itself. Each inverter in the array
930 then configures itself to comply with the grid connection standard in order to feed generated power
into the local power grid.
The handheld device 920 is equipped with GPS and can be carried to be physically near any
object. Such handheld device can be a Smart phone, a PDA, a GPS device, etc. When placed near an
installed inverter, the GPS reading of the handheld device 920 can be transmitted to the installed inverter
as the location of the inverter.
For some embodiments, Figure 11 conceptually illustrates a process 1100 performed by some
embodiments to configure a set of installed inverters by a handheld device to comply with an appropriate
grid connection standard. In some embodiments, the process 1100 starts automatically when the handheld
device is communicatively connected to the set of installed inverters. In some embodiments, the process
600 starts when the handheld device receives a command to start configuration.
The process 1100 begins by determining (at 1105) a location of installation for the set of installed
inverters based on a user input or a GPS coordinate. In some embodiments, a user will tell the handheld
device where the set of inverters are located (e.g., by manually input). In other embodiments, a GPS
receiver equipped on the handheld device will provide a GPS coordinate of the handheld device. Since the
handheld device is presumed to be in close proximity of the installed inverters during this operation, the
GPS coordinate of the handheld device can also be treated as the location of the set of installed inverters.
The process 1100 then identifies (at 1110) a grid connection standard for the determined location.
In some embodiments, the process 1100 queries a grid connection standards lookup table in order to find
the applicable grid connection standard for the determined location. The grid connection standards lookup
table contains all the grid connection standards and the corresponding geographic regions that utilize each
grid connection standard. In some embodiments, the grid connection standards lookup table is located
within the handheld device. In other embodiments, the grid connection standards lookup table is stored on
a device separated from the handheld device and the process 1100 queries the grid connection standards
lookup table through a communication network.
Next, the process 1100 selects (at 1115) an inverter from the set of installed inverters. The
process 1100 then sends (at 11 0) the identified grid connection standard to the selected inverter in order
to configure the inverter based on the grid connection standard. In some embodiments, the inverter stores
the grid connection standard as a set of parameters in a non-volatile memory of the inverter and a
controller configures the power converting component of the inverter based on that set of parameters. In
some embodiments, the inverter loads a unique set of instructions for the grid connection standard for
executing by a controller or processor of the inverter.
The process 1100 then determines (at 1125) whether there are more inverters need to be
configured. When there are more inverters need to be configured, the process 1100 loops back to 1115
and selects another inverter from the set of inverters. When the process 1100 determines (at 1125) that
there is no more inverter for configuration, the process 1100 terminates.
One of ordinary skill in the art will recognize that the process 1100 is a conceptual representation
of the operations used to configure installed inverters through a handheld device. The specific operations
of the process 1100 may not be performed in the exact order shown and described. The specific
operations may not be performed in one continuous series of operations, and different specific operations
may be performed in different embodiments. Furthermore, the process could be implemented using
several sub-processes, or as part of a larger macro process. For instance, in some embodiments, the
process 1100 is performed by one or more software applications that execute on one or more computers.
In some embodiments, the handheld device sends the identified grid connection standard to multiple
inverters at the same time rather than sending it one by one. The process of some embodiments sends the
determined location from the handheld device to the inverters and let each inverter to figure out the
applicable grid connection standard.
IV. GRID CONNECTION STANDARD
A grid connection standard includes a set of parameters that defines the regular behavior of a
power grid and provides a guideline on the quality of power in the power grid. Figure 12 illustrates an
example of a set of parameters included in a grid connection standard. As illustrated in the figure, a grid
connection standard 1200 includes parameters such as voltage 1205, voltage limits 1210, voltage
unbalance 1215, voltage swell 1220, voltage sag 1225, voltage fluctuation 1230, transient overvoltage
1235, harmonics 1240, inter-harmonics 1245, high-order harmonic component 1250, frequency 1255,
frequency fluctuation 1260, electrical noise 1265, interruption 1270, inrush current 1275, DC current
injection 1280, disconnection time 1285, reconnection time 1290, power factor 1291, and power factor
correction 1292.
A steady voltage 1205 is the voltage a customer can expect to receive under normal operating
conditions. Since the loads on a power grid are constantly changing, it is impossible to maintain a
completely constant voltage. Thus the voltage limits 1210 define a range, e.g., +5% and -8%, within
which the deviation from the normal voltage 1205 should be in.
Voltage unbalance 1215 is generated by the increase or decrease of load connected to each phase,
partial running equipment, voltage/current waveform distortion, voltage drop, or reverse phase voltage,
etc. The phenomenon may cause revolution faults, an increase in noise, and less torque in a motor. Thus
the voltage unbalance 1215 should be limited to, e.g., 3% or less.
Voltage swell 1220 is the instantaneous voltage increase caused by lightning strikes, opening or
closing of a power supply circuit, high capacitor bank switching, ground short circuit, or cutting a heavy
load, etc. It may also occur due to the grid connection of a new energy source (solar power, etc.). A
sudden increase in voltage may damage or reset the power supply of equipment. Voltage sag 1225 is an
instantaneous voltage drop caused by the cutting off of the power supply circuit due to a short circuit to
the ground or high inrush current generation when starting a large motor, etc. The voltage sag 1225 may
cause a stop or reset of equipment, turning off lighting, speed change or stop of motor, and
synchronization error of synchronous motors or generators. Thus fast acting voltage regulators or power
conditioners may be needed to protect sensitive equipment from the voltage swell 1220 and the voltage
sag 1225.
Voltage fluctuation (flicker) 1230 is a periodically repeated voltage fluctuation caused by a
furnace, arc welding or thyristor controlled load. It may cause lights to flicker and equipment to
malfunction. Thus a limit may be placed to limit the frequency of occurrence for voltage fluctuation 1230.
Transient overvoltage (impulse) 1235 is the voltage change generated by a lightning strike,
contact problem and closing of a circuit breaker/relay. It is often a rapid change and consists of high peak
voltage. Damage to an equipment's power supply or reset function often occurs near the generation point
due to its high voltage. Therefore, surge suppression equipment or other measures may need to be taken
to protect against damage and malfunction due to transient overvoltage 1235.
Harmonics 1240 are generated by semiconductor control devices in the power supply of
equipment as a result of distorted voltage and current waveforms. When the harmonic component is big, it
may cause serious accidents such as overheating or noise in motors or transformers, burn out reactors in
phase compensation capacitors, etc. Inter-harmonics 1245 are generated by a voltage/current waveform
distortion caused by an electronic frequency converter, cycle converter, Scherbius system, inductive
motor, welder or arc furnace, etc., and consists of non-integer orders of the fundamental frequency. Interharmonics
1245 may cause damage, malfunction or deterioration of equipment due to the zero-cross shift
of the voltage waveform. High-order harmonic component 1250 is a noise component higher than several
kHz generated by the semiconductor control device in the power supply of equipment, and may contain
various frequency components. High-order harmonic components 1250 may damage the power supply of
equipment, reset equipment or introduce abnormal noise in equipment such as TVs or radios. Thus
limitations, e.g., harmonic voltage limits and harmonic current distortion limits, may be imposed to
protect against damage and malfunction due to harmonics 1240, inter-harmonics 1245, and high-order
harmonic component 1250.
A power grid needs to maintain a normal frequency 1255 that should not vary more than a very
small range, e.g., 0.05 Hertz from 60 Hertz. Frequency fluctuation 1260 occurs due to a change of
effective power balance between supply and consumption, or an excessive increase or decrease of the
load. Measures need to be taken to prevent frequency fluctuation 1260 in order to maintain a steady
normal frequency 1255.
Electrical noise 1265 is unwanted electrical signals with broadband spectral content lower than
200 kHz superimposed upon the phase or neutral conductors or signal lines. Power electronic devices,
control circuits, arcing equipment, loads with solid-state rectifiers, and switching power supplies can
cause noise 1265 in power systems. Noise problems are often made worse by improper grounding. Thus
measures such as employing proper grounding techniques and installing filters, isolation transformers,
and line conditioners may need to be taken to mitigate the impact of electrical nose 1265.
Interruption 1270 is a power outage over an instantaneous, short or long period. It is caused by
accidents such as lightning strikes or tripping of the circuit breaker because of a short circuit. Inrush
current 1275 is an instantaneous high current flowing at the time equipment is powered on. Inrush current
1275 may cause relays to malfunction, circuit breakers to open, impact on the rectifier, unstable power
supply voltage, and/or equipment to malfunction or rest. A grid connection standard may require taking
remedial measures in dealing with interruption 1270 and inrush current 1275.
Single-phase voltage source inverters are used for connecting small-scale renewable energy
sources to the low voltage distribution network. They operate to supply the network with sinusoidal
current. If output transformers are not used, these inverters must prevent excessive DC current injection
1280, which may cause detrimental effects in the network. Therefore, a grid connection standard may
contain requirements regarding DC current injection 1280.
The disconnection time 1285 specifies how fast the grid connection of an energy source (e.g., an
inverter) needs to disconnect in the case of the grid going down in a number of milliseconds. The
reconnection time 1290 specifies how fast, e.g., within how many seconds, the grid connection of the
energy source needs to reconnect with the grid after disconnecting from the grid.
The power factor 1291 of an AC electrical power system is defined as the ratio of the real power
flowing to the load to the apparent power in the circuit, and is a dimensionless number between 0 and 1.
Real power is the capacity of the circuit for performing work in a particular time. Apparent power is the
product of the current and voltage of the circuit. Due to energy stored in the load and returned to the
source, or due to a non-linear load that distorts the wave shape of the current drawn from the source, the
apparent power will be greater than the real power.
Power factor correction 1292 brings the power factor of an AC power circuit closer to 1 by
supplying reactive power of opposite sign, adding capacitors or inductors that act to cancel the inductive
or capacitive effects of the load, respectively. The reactive elements can create voltage fluctuations and
harmonic noise when switched on or off. They will supply or sink reactive power regardless of whether
there is a corresponding load operating nearby, increasing the system's no-load losses. In the worst case,
reactive elements can interact with the system and with each other to create resonant conditions, resulting
in system instability and severe overvoltage fluctuations. As such, reactive elements cannot simply be
applied without engineering analysis.
V. ELECTRONIC SYSTEM
Many of the above-described features and applications are implemented as software processes
that are specified as a set of instructions recorded on a computer readable storage medium (also referred
to as computer readable medium). When these instructions are executed by one or more computational or
processing unit(s) (e.g., one or more processors, cores of processors, or other processing units), they cause
the processing unit(s) to perform the actions indicated in the instructions. Examples of computer readable
media include, but are not limited to, CD-ROMs, flash drives, random access memory (RAM) chips, hard
drives, erasable programmable read only memories (EPROMs), electrically erasable programmable read
only memories (EEPROMs), etc. The computer readable media does not include carrier waves and
electronic signals passing wirelessly or over wired connections.
In this specification, the term "software" is meant to include firmware residing in read-only
memory or applications stored in magnetic storage which can be read into memory for processing by a
processor. Also, in some embodiments, multiple software inventions can be implemented as sub-parts of a
larger program while remaining distinct software inventions. In some embodiments, multiple software
inventions can also be implemented as separate programs. Finally, any combination of separate programs
that together implement a software invention described here is within the scope of the invention. In some
embodiments, the software programs, when installed to operate on one or more electronic systems, define
one or more specific machine implementations that execute and perform the operations of the software
programs.
Figure 13 conceptually illustrates an electronic system 1300 with which some embodiments of
the invention are implemented. The electronic system 1300 may be a computer (e.g., a desktop computer,
personal computer, tablet computer, etc.), phone, PDA, or any other sort of electronic device. Such an
electronic system includes various types of computer readable media and interfaces for various other
types of computer readable media. Electronic system 1300 includes a bus 1305, processing unit(s) 1310, a
graphics processing unit (GPU) 1315, a system memory 1320, a network 1325, a read-only memory
(ROM) 1330, a permanent storage device 1335, input devices 1340, and output devices 1345.
The bus 1305 collectively represents all system, peripheral, and chipset buses that
communicatively connect the numerous internal devices of the electronic system 1300. For instance, the
bus 1305 communicatively connects the processing unit(s) 1310 with the read-only memory 1330, the
GPU 1315, the system memory 1320, and the permanent storage device 1335.
From these various memory units, the processing unit(s) 1310 retrieves instructions to execute
and data to process in order to execute the processes of the invention. The processing unit(s) may be a
single processor or a multi-core processor in different embodiments. Some instructions are passed to and
executed by the GPU 1315. The GPU 1315 can offload various computations or complement the image
processing provided by the processing unit(s) 1310. The read-only-memory ROM 1330 stores static data
and instructions that are needed by the processing unit(s) 1310 and other modules of the electronic
system. The permanent storage device 1335, on the other hand, is a read-and-write memory device. This
device is a non-volatile memory unit that stores instructions and data even when the electronic system
1300 is off. Some embodiments of the invention use a mass-storage device (such as a magnetic or optical
disk and its corresponding disk drive) as the permanent storage device 1335.
Other embodiments use a removable storage device (such as a floppy disk, flash memory device,
etc., and its corresponding disk drive) as the permanent storage device. Like the permanent storage device
1335, the system memory 1320 is a read-and-write memory device. However, unlike storage device 1335,
the system memory 1320 is a volatile read-and-write memory, such a random access memory. The system
memory 1320 stores some of the instructions and data that the processor needs at runtime. In some
embodiments, the invention's processes are stored in the system memory 1320, the permanent storage
device 1335, and/or the read-only memory 1330. For example, the various memory units include
instructions for processing multimedia clips in accordance with some embodiments. From these various
memory units, the processing unit(s) 1310 retrieves instructions to execute and data to process in order to
execute the processes of some embodiments.
The bus 1305 also connects to the input and output devices 1340 and 1345. The input devices
1340 enable the user to communicate information and select commands to the electronic system. The
input devices 1340 include alphanumeric keyboards and pointing devices (also called "cursor control
devices"), cameras (e.g., webcams), microphones or similar devices for receiving voice commands, etc.
The output devices 1345 display images generated by the electronic system or otherwise output data. The
output devices 1345 include printers and display devices, such as cathode ray tubes (CRT) or liquid
crystal displays (LCD), as well as speakers or similar audio output devices. Some embodiments include
devices such as a touchscreen that function as both input and output devices.
Finally, as shown in Figure 13, bus 1305 also couples electronic system 1300 to a network 1325
through a network adapter (not shown). In this manner, the computer can be a part of a network of
computers (such as a local area network (LAN), a wide area network (WAN), or an Intranet, or a network
of networks, such as the Internet. Any or all components of electronic system 1300 may be used in
conjunction with the invention.
Some embodiments include electronic components, such as microprocessors, storage and memory
that store computer program instructions in a machine-readable or computer-readable medium
(alternatively referred to as computer-readable storage media, machine-readable media, or machinereadable
storage media). Some examples of such computer-readable media include RAM, ROM, read
only compact discs (CD-ROM), recordable compact discs (CD-R), rewritable compact discs (CD-RW),
read-only digital versatile discs (e.g., DVD-ROM, dual-layer DVD-ROM), a variety of
recordable/rewritable DVDs (e.g., DVD-RAM, DVD-RW, DVD+RW, etc.), flash memory (e.g., SD
cards, mini-SD cards, micro-SD cards, etc.), magnetic and/or solid state hard drives, read-only and
recordable Blu-Ray® discs, ultra density optical discs, any other optical or magnetic media, and floppy
disks. The computer-readable media may store a computer program that is executable by at least one
processing unit and includes sets of instructions for performing various operations. Examples of computer
programs or computer code include machine code, such as is produced by a compiler, and files including
higher-level code that are executed by a computer, an electronic component, or a microprocessor using an
interpreter.
While the above discussion primarily refers to microprocessor or multi-core processors that
execute software, some embodiments are performed by one or more integrated circuits, such as
application specific integrated circuits (ASICs) or field programmable gate arrays (FPGAs). In some
embodiments, such integrated circuits execute instructions that are stored on the circuit itself. In addition,
some embodiments execute software stored in programmable logic devices (PLDs), ROM, or RAM
devices.
As used in this specification and any claims of this application, the terms "computer", "server",
"processor", and "memory" all refer to electronic or other technological devices. These terms exclude
people or groups of people. For the purposes of the specification, the terms display or displaying means
displaying on an electronic device. As used in this specification and any claims of this application, the
terms "computer readable medium," "computer readable media," and "machine readable medium" are
entirely restricted to tangible, physical objects that store information in a form that is readable by a
computer. These terms exclude any wireless signals, wired download signals, and any other ephemeral
signals.
While the invention has been described with reference to numerous specific details, one of
ordinary skill in the art will recognize that the invention can be embodied in other specific forms without
departing from the spirit of the invention. In addition, a number of the figures (including Figures 6, 7,
and 11) conceptually illustrate processes. The specific operations of these processes may not be
performed in the exact order shown and described. The specific operations may not be performed in one
continuous series of operations, and different specific operations may be performed in different
embodiments. Furthermore, the process could be implemented using several sub-processes, or as part of a
larger macro process. Thus, one of ordinary skill in the art would understand that the invention is not to
be limited by the foregoing illustrative details, but rather is to be defined by the appended claims.
CLAIMS
1. A non-transitory machine readable medium storing a program executable by at least one
processor, the program comprising sets of instructions for:
identifying a grid connection standard for an energy-harvesting device that has been
installed in a physical installation; and
configuring the energy-harvesting device to apply the identified grid connection standard.
2 . The non-transitory machine readable medium of claim 1, wherein the program further
comprises a set of instructions for determining a physical location for the physical installation, wherein
the grid connection standard is identified based on the physical location.
3. The non-transitory machine readable medium of claim 2, wherein the set of instructions
for determining the physical location comprises a set of instructions for receiving the physical location
from a user input.
4 . The non-transitory machine readable medium of claim 2, wherein the set of instructions
for determining the physical location comprises a set of instructions for receiving the physical location
from a handheld device located near the physical installation, the handheld device equipped with a global
positioning system ("GPS") receiver, wherein the GPS receiver identifies the physical location.
5. The non-transitory machine readable medium of claim 2, wherein the set of instructions
for determining the physical location comprises a set of instructions for identifying the physical location
using a GPS receiver within the energy-harvesting device.
6. The non-transitory machine readable medium of any preceding claim, wherein the set of
instructions for identifying the grid connection standard comprises a set of instructions for receiving the
grid connection standard from a communication gateway connecting the energy-harvesting device to a
communication network.
7. The non-transitory machine readable medium of claim 6, wherein the communication
gateway identifies the grid connection standard based on a physical location determined by a set of
parameters of the communication network.
8. The non-transitory machine readable medium of any preceding claim, wherein the set of
instructions for identifying the grid connection standard comprises a set of instructions for receiving the
grid connection standard from a handheld device located near the physical installation.
9. The non-transitory machine readable medium of claim 8, wherein the handheld device
identifies the grid connection standard based on a physical location of the physical installation.
10. The non-transitory machine readable medium of claim 9, wherein the handheld device is
equipped with a global positioning system ("GPS") receiver, wherein the physical location is determined
by the GPS receiver.
11. The non-transitory machine readable medium of claim 9, wherein the physical location is
determined by a user input.
12. An energy harvesting device comprising:
a power converter for converting DC power from a photovoltaic device to AC electricity;
and
a controller for configuring, after the energy harvesting device has been installed at a
physical location, the power converter based on a grid connection standard.
13. The energy harvesting device of claim 12 further comprising a global positioning system
("GPS") receiver for determining the physical location, wherein the controller is further for identifying
the grid connection standard based on the physical location determined by the GPS receiver.
14. The energy harvesting device of claim 13, wherein the controller identifies the grid
connection standard through searching a data structure containing information relating to a plurality of
grid connection standards.
15. The energy harvesting device of claim 14, wherein the data structure is stored by the
energy harvesting device.
16. The energy harvesting device of claim 14, wherein the data structure is stored by a device
separate from the energy harvesting device.
17. The energy harvesting device of any one of claims 12 to 16, wherein the controller
receives the grid connection standard from a device separate from the energy harvesting device.
18. The energy harvesting device of any one of claims 12 to 17 further comprising a
communication module, wherein the controller uses the communication module for communicating with
other devices in a communication network.
19. The energy harvesting device of claim 18, wherein the communication module comprises
a wireless transceiver for transmitting and receiving wireless signals.
20. The energy harvesting device of claim 18 or 19, wherein the communication module is
configured to perform power line communication.
21. The energy harvesting device of any one of claims 12 to 20, wherein the controller
comprises at least one processing unit.
22. A method comprising:
identifying a grid connection standard for a plurality of energy-harvesting devices that
have been installed in a physical installation; and
applying the identified grid connection standard to the plurality of energy-harvesting
devices.
23. The method of claim 22 further comprising determining a physical location for the
physical installation, wherein the grid connection standard is identified based on the physical location.
24. The method of claim 23, wherein the physical location is determined based on a set of
network connection parameters.
25. The method of claim 23 or 24, wherein the physical location is determined through
receiving a user input.
26. The method of claim 23, 24 or 25 wherein the physical location is determined using a
global positioning system ("GPS") receiver.
27. The method of any one of claims 23 to 26, wherein the grid connection standard is
identified through searching a data structure based on the determined physical location, wherein the data
structure contains information relating to a plurality of grid connection standards.
28. The method of claim 27, wherein the data structure is a grid connection standards lookup
table.
29. The method of any one of claims 22 to 28 further comprising transmitting the grid
connection standard to the plurality of energy-harvesting devices.