ENERGY MANAGEMENT AND BACK UP UNIT
BACKGROUND OF THE INVENTION
Field of Invention
The invention described in this document relates to more efficient power management particularly for telecommunication purposes.
Description of the Problem
Mobile phones are common throughout the world and the number of subscribers to mobile services is growing quickly particularly in the developing countries.
Mobile networks need base transceiver station(s) (BTS(s)). BTS is a piece of equipment that facilitates wireless communication between user equipment (UE) and a network. UEs are devices like mobile phones, computers with wireless internet connectivity and other functionality.
The BTS needs uninterrupted electrical power for its operation. The BTS also needs to operate within a specified temperature range.
BTS comprise batteries operable in float mode. These batteries ensure that power supply to the BTS is not disrupted in case mains power fails temporarily.
BTS are of two broad categories:
i) Indoor type: this type of BTS is housed in a shelter (BTS Shelter). The BTS Shelter comprises BTS and one or more air conditioners and/or heaters as peripherals. The air conditioners and/or heaters ensure that the BTS operates within the temperature within the specified temperature range.
ii) Outdoor type: this type of BTS does not need to be housed in a shelter. The BTS can operate in the temperature range prevalent at the location;
In many locations power failures are common and the outages can be for extended periods. The batteries operable in float mode are ill suited to providing power back-up periodically and/or for extended periods of time.
The batteries operable in float mode are designed for quick response time in case of power failure. In case batteries operable in float mode are deep discharged (a condition which is likely in case these batteries are used to provide power for extended periods) and then recharged, the batteries tend to lose life after a few cycles of deep discharge and subsequent charging. Further the batteries operable in float mode cannot provide power to air conditioners since air-conditioners need very high inrush currents.
A solution for meeting the extended power outage requirements and for running air conditioners is to provide for a diesel generator (DG) at each BTS site. If there is a power outage, the DG is switched on to provide power to the BTS and the peripherals. The batteries in float mode ensure that power supply to the BTS is not interrupted for the time needed to start the DG.
The use of DGs however creates problems. Firstly the DGs are costly to operate. The cost of electricity from a generator is far more than the cost of electricity supplied at the mains by utilities since diesel as a fuel is costlier than the fuels normally used by utilities. Secondly the DGs have a large number of moving parts and need a large inventory of spares and regular maintenance. Thirdly the logistics of supplying diesel and spares to all BTS sites is costly and complex and the inability to maintain the supply chain constrains expansion of mobile networks. Fourthly exhaust from DGs adds significantly to environmental pollution particularly in urban areas. Fifthly DGs are noisy and there is resistance to their use particularly in urban areas.
There is thus need to reduce DG usage and to make the DG usage more efficient.
Independently it is found that the quality of AC power at the mains in many situations tends to be poor. The quality of power is affected by many factors some of which are voltage fluctuations, spikes and frequency fluctuation. Further, often, all three phases of the AC power are not of the same quality and/or magnitude. As a result the BTS and the peripherals tend to malfunction and even breakdown.
There is thus also need for apparatus such that the power supplied from the mains can be conditioned. There is also need for apparatus and method such that the two best phases of the three phases of AC power at Mains can be selected and the power from two selected best phases transformed into single phase power.
Before proceeding to describe the present invention it would be necessary to introduce certain background information.
DIESEL GENERATOR
It is found that the DG capacity, particularly installed at BTS Shelters, is far in excess of the steady state power requirement. The reason is that the air conditioners have very high initial or inrush power requirements. DG capacity is selected considering the peak power requirement of the BTS and all peripherals.
A DG however operates most efficiently when supplying power to a pre-determined load. In case DG supplies power to a load which is lesser than the pre-determined load, the efficiency of power generation is less than optimal. It is thus advisable that the DG supply power to a load which is approximately the same as the pre-determined load. The pre-determined load will hereinafter be referred to as the "DG Set Point". The DG Set Point can be either the load at which the DG operates most efficiently or another load selected in accordance with the specific requirements of the operating environment.
BATTERY
Each battery has a particular designed ampere-hour capacity for a pre-determined discharge current. The ampere-hour capacity is the time taken to fully discharge a fully charged battery for the above pre-determined discharge current. The ampere-hour capacity thus varies with the discharge current.
The ampere-hour capacity determines the power available from a battery.
The depth of discharge (hereinafter referred to as "discharge of a battery") is defined as that percentage of the designed ampere-hour capacity of a battery that has been discharged during use of the battery.
It is known to persons skilled in the art that battery life deteriorates rapidly in case full discharge of a battery is repeatedly permitted. Hence for ensuring life of a battery it is necessary to limit the discharge of a battery to a particular value hereinafter referred to as "Battery Set Point". The Battery Set Point is determined by averaging the likely discharge currents of the battery for a particular application.
During actual operation of a battery the discharge of a battery is calculated by measuring the actual discharge current of the battery against the corresponding time and calculating the ampere-hour discharged by the battery integrating the discharge current values for the above time.
During charging, a battery needs to be charges at different voltages depending upon the discharge of the battery. The battery is initially charged at a higher voltage, known as bulk charging voltage, and later at a lower voltage, known as trickle charging voltage. The voltage profile against the charging time determines the charge accumulated in a battery.
In order to determine the discharge of a battery during its operation, it is important to know the discharge current and charging voltage as a function of time. This can be done by measuring the current and voltage during operation of the battery in a manner known to the art.
POWER AVAILABILITY
It is observed that while in many locations AC power at the mains is often not available around the clock, power is available at certain times which may either be fixed or may vary from day to day. At certain locations power may not be available for periods that may extend beyond a calendar day. Power is however available at other times. At those it is however possible that the power in one or more phases may be affected by factors such as voltage fluctuations, spikes, frequency fluctuations and sustained low or high voltages.
SUMMARY OF THE INVENTION
The invention of this Application in one aspect relates to an apparatus and method for reducing the operational cost of DG operation. In another aspect the invention relates to increasing the efficiency of DG operation. In yet another aspect the invention relates to an apparatus and method where the power supplied from the mains can be conditioned. Still further the invention relates to an apparatus and method where the two phases of the three phases can be selected and the power from two selected best phases is transformed into single phase power.
The invention of this Application will be described by means of embodiments given hereinafter. It will be noted that the embodiments are given only by way of example and are not meant to limit in any way the generality of the invention. The invention, as would be evident to a person skilled in the arts can be embodied in many other ways.
The first embodiment of this invention, relates to an apparatus suitable for use with outdoor BTSs, comprises:
a) Mains at which AC power is supplied;
b) DG;
c) BTS;
d) Inverter for converting DC power from Batteries (Inverter Batteries) into AC power. The Inverter Batteries are electrically connected to the Inverter;
e) Peripherals, which Peripherals do not include an air conditioner or a heater;
f) Voltage & Current Sensors for measuring discharge of the Inverter Batteries;
g) Controller in communication with the Mains, the DG, the Inverter, and Voltage & Current Sensors.
In this embodiment the DG operates when there is no AC power supply by the Mains and discharge of the Inverter Batteries is below the Battery Set Point.
When AC power is unavailable at the Mains, Controller determines if discharge of Inverter Batteries is greater than the Battery Set Point.
In case the discharge of the Inverter Batteries is greater than the Battery Set Point then power is supplied from the Inverter to the BTS and Peripherals.
The Inverter is so selected that it can supply the required power to the BTS and Peripherals. The ampere-hour capacity of the Inverter Batteries is selected with reference to the likely time that the Inverter will supply power to the BTS and Peripherals. The likely time can be selected on the basis of available historic data regarding availability of power at the site.
Once the discharge of the Inverter Batteries falls below the Battery Set Point, the DG is switched on. The DG supplies power to the BTS and Peripherals. In case the DG is operating at a load below the DG Set Point, the DG supplies balance power to Inverter Batteries so as to charge them till the Inverter Battery charge reaches a pre¬determined value.
Once the Inverter Battery charge reaches the above pre-determined value the DG is switched off and power to BTS and Peripherals provided as hereinbefore by the Inverter.
Once power from the Mains is available, the DG if still operating, is switched off and power from the Mains is used to charge the Inverter Batteries if needed.
It would be noted that the present invention reduces DG usage with savings in operational costs. Further the DG usage is as close the DG Set Point as practicable so that the DG operates efficiently.
The second embodiment of this invention relates to an apparatus suitable for use with indoor BTSs and comprises:
a) Mains at which AC power is supplied;
b) DG;
c) Inverter Batteries, the Inverter Batteries being electrically connected to Inverter;
d) BTS Shelter comprising BTS and Peripherals;
e) Temperature Sensor to measure temperature inside the BTS Shelter;
f) Voltage & Current Sensor for measuring discharge of the Inverter Batteries.
g) Controller in communication with the Mains, the DG, the Inverter, the Temperature Sensor and Voltage & Current Sensor.
In this embodiment the DG operates when there is no AC power supply by the Mains and discharge of Inverter Batteries is below the Battery Set Point.
In case AC power is unavailable at the Mains, Controller determines if:
a) Temperature inside the BTS Shelter is within a pre-determined range;
b) Discharge of Inverter Batteries is greater than the Battery Set Point.
When the temperature inside the BTS Shelter is within the pre-determined range and discharge of the Inverter Batteries is greater than the Battery Set Point then power is supplied from Inverter to the BTS and Peripherals other than air conditioner or heater.
In case the temperature inside the BTS Shelter deviates from the pre-determined range but the discharge of Inverter Batteries continues to be greater than the Battery Set Point then power is supplied from Inverter to the air conditioner or heater till the temperature again is within the pre-determined range and the discharge of the Inverter Batteries continues to be above the Battery Set Point.
The Inverter is so selected that it can supply the required power to the BTS and Peripherals. The ampere-hour capacity of the Batteries is selected with reference to the likely time that the Inverter will supply power to the BTS and Peripherals. The likely time can be selected on the basis of available historic data regarding availability of power at the site.
Once the discharge of the Batteries falls below the Battery Set Point, the DG is switched on. The DG supplies power to the BTS and Peripherals. Power to the air conditioner or heater is supplied in case the temperature inside the BTS Shelter deviates from the pre-determined range and the heater or air-conditioner need to be operated. Power is supplied to the air conditioner or heater till the temperature again reaches a pre-determined value in the specified range.
In case the DG is operating at a load below the DG Set Point, the DG supplies balance power to the Inverter Batteries so as to charge them till the Inverter Battery charge reaches a pre-determined value.
Once the Inverter Battery charge reaches the pre-determined value the DG is switched off and power to BTS and Peripherals provided as hereinbefore.
Once power from the Mains is available, the DG, if still operating, is switched off and power from the Mains is used to charge the Inverter Batteries if needed.
It would be noted that this embodiment of the present invention reduces DG usage with savings in operational costs. Further the DG usage is as close the DG Set Point as practicable so that the DG operates efficiently.
Yet another embodiment of the present invention comprises the previous embodiments and further comprises a line conditioner unit for conditioning the AC power available from the Mains.
Another embodiment of this invention comprises any of the previous embodiments and further comprises a phase selector for selecting the two best phases out of the three available from the Mains. The two selected phases are transformed into single phase for supply to the BTS and peripherals.
BRIEF DESCRIPTION OF THE DRAWING
Fig. 1 describes the block diagram of the first embodiment of the invention of this Application.
Fig. 2 describes the block diagram of the second embodiment of the invention of this Application.
Fig. 3 describes the block diagram of the third embodiment of the invention of this Application.
Fig. 4 describes the block diagram of the fourth embodiment of the invention of this Application.
DETAILED DESCRIPTION OF EMBODIMENTS
Embodiment 1
The first embodiment of this invention, relates to an apparatus suitable for use with outdoor BTSs is described in Fig. 1. Fig. 1 describes the block diagram of the embodiment of the invention. It may be noted that this embodiment can be implemented through more than one circuit as would be evident to a person skilled in the art. The invention of this embodiment comprises:
a) Mains 11 at which AC power is supplied;
b) DG21;
c) Inverter 31 for converting DC power from Inverter Batteries 301 into AC power;
d) Inverter Batteries 301, which Inverter Batteries are electrically connected to Inverter 31;
e) BTS401;
f) Peripherals 411, which Peripherals do not include either an air-conditioner or a heater;
g) Voltage Sensor 511 & Current Sensor 512 for measuring discharge of batteries 301;
h) Controller 51 in communication with Mains 11, DG 21, Inverter 31 and Voltage Sensor 511 & Current Sensor 512. The Controller 51 determines, according to logic hereinafter discussed, when power would be supplied by DG 21 or Inverter 31.
In case AC power is unavailable at the Mains 11, Controller 51 determines if discharge of Inverter Batteries 301 is greater than the Battery Set Point.
In case the discharge of Batteries 301 is greater than the Battery Set Point then power is supplied from the Inverter 31 to BTS 401 and Peripherals 411.
The Inverter 31 is so selected that it can supply the required power to the BTS 401 and Peripherals 411. The ampere-hour capacity of Batteries 301 is selected with reference to the likely time that the Inverter 31 will supply power to BTS 401 and Peripherals 411. The likely time can be selected on the basis of available historic data regarding availability of power at the site of BTS Shelter 41.
Once the discharge of Batteries 301 falls below the Battery Set Point, the DG 21 is switched on. The DG supplies power to BTS 401 and Peripherals 411. In case the DG 21 is operating at a load below the DG Set Point, the DG 21 supplies balance power to Inverter Batteries 301 so as to charge them till the charge of the Inverter Batteries 301 reaches a pre-determined value.
Once the charge of the Inverter Batteries 301 reaches the above pre-determined value the DG 21 is switched off and power to BTS 401 and Peripherals 411 provided as hereinbefore.
Once power from Mains 11 is available the DG 21, if still operating, is switched off and power from the Mains 11 is used to charge the batteries 301 if needed.
The Inverter 31 of this embodiment is based on any of the following topologies:
a) Full /Half bridge PWM Inverter topology;
b) Push-Pull Inverter topology;
c) Resonant Inverter topology; or
d) Any other topology evident to a person skilled in the art.
The Inverter Batteries 301 of this embodiment are different from batteries operable in float mode. The Inverter Batteries are designed for repeated cycles of deep discharge and recharging and are readily available in the market. The Inverter Batteries 301 can be of any of the following types:
a) VRLA type;
b) Tubular type;
c) Ni-Cd Type; or
d) Any other type evident to a person skilled in the art.
The Voltage Sensor 511 of this embodiment can be of any of the following types:
a) Isolated voltage sensor;
b) Non-Isolated voltage sensor; or
c) Any other type evident to a person skilled in the art.
The Current Sensor 512 of this embodiment can be of any of the following types:
a) Isolated current sensor;
b) Non-Isolated current sensor; or
c) Any other type evident to a person skilled in the art.
The Controller 51 of this embodiment can be of any of the following types:
a) Microcontroller based;
b) Digital Signal Processor (DSP) based; or
c) Any other type evident to a person skilled in the art.
Embodiment 2
The second embodiment of this invention is described in Fig. 2 and comprises an indoor BTS. Fig. 2 describes the block diagram of the embodiment of the invention. It may be noted that this embodiment can be implemented through more than one circuit evident to a person skilled in the art. The invention of this embodiment comprises:
a) Mains 11 at which AC power is supplied;
b) DG21;
c) Inverter 31 for converting DC power from Inverter Batteries 301 into AC power;
d) Inverter Batteries 301, which Inverter Batteries are electrically connected to Inverter 31;
e) BTS Shelter 41 comprising BTS 401 and Peripherals 411. These Peripherals may include either an air-conditioner or heater or both;
f) Temperature Sensor 501 to measure temperature inside BTS Shelter 41;
g) Voltage Sensor 511 & Current Sensor 512 for measuring discharge of Inverter Batteries 301;
h) Controller 51 in communication with Mains 11, DG 21, Inverter 31, Temperature Sensor 501 and Voltage Sensor 511 & Current Sensor 512. The Controller 51 determines, according to logic hereinafter discussed, when power would be supplied by DG 21 or Inverter 31.
In case AC power is unavailable at the Mains 11, Controller 51 determines if:
a) temperature inside BTS Shelter 41 is within a pre-determined range;
b) discharge of Batteries 301 is greater than the Battery Set Point.
In case the temperature inside BTS Shelter 41 is within the pre-determined range and discharge of Inverter Batteries 301 is greater than the Battery Set Point then power is supplied from Inverter to BTS 401 and Peripherals 411 other than air conditioner or heater.
In case the temperature inside BTS Shelter 41 deviates from the pre-determined range but the discharge of the Inverter Batteries 301 continues to be greater than the Battery Set Point then power is supplied from Inverter to the air conditioner or heater, while the discharge of Battery 301 continues to be greater than the Battery Set Point, till the temperature again is within the pre-determined range.
The Inverter 31 is so selected that it can supply the required power to the BTS 401 and Peripherals 411. The ampere-hour capacity of Batteries 301 is selected with reference to the likely time that the Inverter 31 will supply power to BTS 401 and Peripherals 411. The likely time can be selected on the basis of available historic date regarding availability of power at the site of BTS Shelter 41.
Once the discharge of Batteries 301 falls below the Battery Set Point, the DG is switched on. The DG supplies power to BTS 401 and Peripherals 411. Power to the air conditioner or heater is supplied in case the temperature inside BTS Shelter 41 deviates from the pre-determined range and the heater or air-conditioner need to be operated. Power is supplied to the air conditioner or heater till the temperature again reaches a pre-determined value in the specified range.
In case the DG 21 is operating at a load below the DG Set Point, the DG supplies balance power to Inverter Batteries 301 so as to charge them till the charge of the Inverter Batteries 301 reaches a pre-determined value.
Once the charge of the Inverter Batteries 301 reaches the above pre-determined value the DG 21 is switched off and power to BTS 401 and Peripherals 411 provided as hereinbefore.
Once power from Mains 11 is available the DG 21, if still operating, is switched off and power from the Mains 11 is used to charge the Inverter Batteries 301 if needed.
The DG 21, Inverter 31, Inverter Batteries 301 and Voltage Sensor 511 & Current Sensor 512, of this embodiment will be of the same type as for the previous embodiment.
The Temperature Sensor 501 of this embodiment can be of any of the following types:
a) Resistance Temperature Detector;
b) Thermistor Type;
c) Thermocouple Type; or
d) Any other type evident to a person skilled in the art.
Embodiment 3
The third embodiment of the present invention described in Fig. 3 comprises any of the previous embodiments and further comprises a line conditioner unit 71 for conditioning the AC power available at the Mains 11.
The conditioning would comprise eliminating voltage spikes and regulating the voltage to within pre-determined limits.
The line conditioner unit 71 of this embodiment can be of any of the following types:
a) Passive line conditioner with passive components;
b) Active line conditioner with discrete components; or
c) Any other type evident to a person skilled in the art.
It would be noted that Fig. 3 describes the block diagram of the embodiment of the invention for a BTS Shelter. The corresponding embodiment of this invention for a BTS will be evident to a person skilled in the art. It may be noted that this embodiment can be implemented through more than one circuit evident to a person skilled in the art.
Embodiment 4
The fourth embodiment of this invention is described in Fig. 4. The invention of this embodiment comprises any of the previous embodiments and further comprises phase selector 81 for selecting the two best phases out of the three available at the Mains 11 and transforming the selected phases into single phase AC supply.
The phase selector 81 of this embodiment can be of the following type:
a) Discrete type
b) Electromechanical type; or
c) Any other type evident to a person skilled in the art.
It would be noted that Fig. 4 describes the block diagram of the embodiment of the invention for a BTS Shelter. The corresponding embodiment of this invention for a BTS will be evident to a person skilled in the art. It may be noted that this embodiment can be implemented through more than one circuit evident to a person skilled in the art.

We claim:
1. An apparatus of Fig. 1 comprising:
a) Mains 11 at which AC power is supplied;
b) DG21;
c) Inverter 31;
d) Inverter Batteries 301 which Inverter Batteries 301 have a pre-determined Battery Set Point and which Inverter Batteries 301 are electrically connected to Inverter 31;
e) BTS401;
f) Peripherals 411 which Peripherals do not comprise air-conditioner or heater;
g) Voltage Sensor 511 & Current Sensor 512 for measuring discharge of Inverter Batteries 301;
h) Controller 51 in communication with Mains 11, DG 21, Inverter 31, Temperature Sensor 501 and Voltage Sensor 511;
such that the DG 21 operates when:
i. there is no AC power supply by Mains 11; and
ii. discharge of Inverter Batteries 301 is below the Battery Set Point.
2. An apparatus of Fig. 2 comprising:
a) Mains 11 at which AC power is supplied;
b) DG 21;
c) Inverter 31;
d) Inverter Batteries 301 which Inverter Batteries 301 have a pre-determined
Battery Set Point and which Inverter Batteries 301 are electrically connected to
Inverter 31;
e) BTS Shelter 41 comprising BTS 401 and Peripherals 411, which Peripherals 411
comprise air-conditioner or heater or both;
f) Temperature Sensor 501 to measure temperature inside BTS Shelter 41;
g) Voltage Sensor 511 & Current Sensor 512 for measuring discharge of Inverter
Batteries 301;
h) Controller 51 in communication with Mains 11, DG 21, Inverter 31, Temperature Sensor 501 and Voltage Sensor 511& Current Sensor 512;
such that the DG 21 operates when:
i. there is no AC power supply by Mains 11; and
ii. discharge of Batteries 301 is below the Battery Set Point.
3. An apparatus of any of the previous claims further comprising a line conditioner
unit 71.
5. An apparatus of any of the previous claims further comprising a phase
selector 81.