Claims:We claim:
1. A unidirectional power flow based grid tied system comprises of: a
unidirectional DC-DC converter (101) wherein input port of the said
converter connected to the DC power source(s)(102); a capacitor(103)
coupled to the output of the said DC-DC converter(101); a VSC(104)
interlinked the capacitor(103) & input of the filter(105); a relay(106)
coupled to the output of the filter(105) to establish connection between
grid(107) & filter(105); a VSC(108) coupled to DC energy source routed
prior to DC-DC converter(101); a motor(109) having input port coupled
to output port of VSC(108); a control card(110) connected to VSC(104),
VSC(108) & DC-DC converter (101) to control power distribution.
2. A unidirectional power flow based grid tied system comprises of: a
unidirectional DC-DC converter(101) wherein input port of the said
converter connected to the DC power source(s)(102); a capacitor(103)
coupled to the output of the said DC-DC converter(101); a VSC(104)
interlinked the capacitor(103) & input of the filter(105); a relay(106)
coupled to the output of the filter(105) to establish connection between
grid(107) & filter(105); a VSC(108) coupled to DC energy source routed
prior to VSC(104); a motor(109) having input port coupled to output port
of VSC(108); a control card(110) connected to VSC(104), VSC(108) &
DC-DC converter(101) to control power distribution.
3. The unidirectional power flow based grid tied system as claimed in claim
1& 2, wherein said VSC(108) serves as a variable frequency drive.
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4. The unidirectional power flow based grid tied system as claimed in claim
1& 2, wherein said VSC(108) can only be run from available DC energy
source(s)(102).
5. The unidirectional power flow based grid tied system as claimed in claim
1& 2, wherein said VSC(104) export energy to grid.
6. The unidirectional power flow based grid tied system as claimed in claim
1& 2, wherein said VSC(104) does not draw energy from grid(107) to run
local load.
7. The unidirectional power flow based grid tied system as claimed in claim
1& 2, wherein said unidirectional DC-DC converter (101) further
comprises of Inductor(s), Capacitor(s), Switch(es) & Diode(s).
8. The unidirectional power flow based grid tied system as claimed in claim
1& 2, wherein said VSC(104), VSC(108) & DC-DC converter(101)
communicate to each other via control card(s)(110) for managing power
flow.
9. The unidirectional power flow based grid tied system as claimed in claim
1& 2, substantially described with reference to the accompanying
drawing. , Description:Field of the invention
The present invention relates to a grid tied inverter, more particularly it relates
to a development of unidirectional grid tied power controller. However it
restricts the power flow from grid to load point.
Background of the invention
The conventional solar water pumping based system use a VFD which
converters solar energy suitable for motor pumping application which makes it
an stand alone system.
US patent no. US8081494B2 Describe a grid-tie inverter, the DC input is phase
and pulse-width modulated to define multiple phase shifted voltage pulses with
the width of each pulse being modulated according to the grid AC amplitude for
the corresponding portion of the AC phase.
However, the pumps are not used for 100% of the time in the year. The same
solar panels can be used for feeding the solar energy into the grid. However, in
this type of system unidirectional power flow is not guaranteed and the water
pumps can be run from grid also i.e. bidirectional power flow is possible with
the grid. Thus this feature does not promote the utilization of solar energy.
Moreover pumping puts an extra intermittent load on the grid, therefore
unidirectional power flow based controller are better choice.
A need remains for a system which promotes the utilization of solar energy &
utilise 100% of the available energy at solar panel.

Objects of the Invention
It is an object of the present invention is to provide a unidirectional grid tied
power control system.
It is another object of the present invention is to provide a control system which
feed access energy available at solar panel to grid (while pump is sharing/Not
working) therefore cost pay back is fast.
It is still another object of the present invention is to provide a power control
system which restrict the power flow from grid to pump set.
It is further object of the present invention is to provide a power control system
to cover all types of motor i.e. Induction, PMSM & BLDC.
Summary of the Invention
The present invention deals with a grid tied solar pumping system, wherein the
proposed system not only serves the function of pumping but also sends the
extra generated solar power to the grid.
In the present invention various standard terms has been used described here,
‘Direct Current’ here after referred as ‘DC’ and ‘Voltage Source Converter’
hereafter referred as VSC in all forward descriptions and claims.
The proposed system has a unique feature that the pump can only be run from
any renewable energy source(s) or any DC energy source(s), a unidirectional
power flow feature does not allow system to withdraw the power from the grid
to the load point.
A unidirectional power flow based grid tied system comprises of: a
unidirectional DC-DC converter (101) wherein input port of the said converter
connected to the DC power source(s) (102); a capacitor (103) coupled to the

output of the said DC-DC converter (101); a VSC(104) interlinked the
capacitor(103) & input of the filter(105); a relay(106) coupled to the output of
the filter(105) to establish connection between grid(107) & filter(105); a
VSC(108) coupled to DC energy source(s)(102) routed prior to DC-DC
converter(101); a motor (109) having input port coupled to output port of
VSC(108); a control card(110) connected to VSC(104), VSC(108) & DC-DC
converter (101) to control power distribution.
Brief Description of Drawings
Figure 1 illustrates an exemplary block diagram of the device in accordance
with the present disclosure;
Figure 2 illustrates typical circuit diagram of the device in accordance
with the present disclosure;
Detailed Description of the invention
Hereinafter, various embodiments of the present disclosure will be described
with reference to the accompanying drawings. It should be noted that all of
these drawings and description are only presented as exemplary embodiments.
It is to note that based on the subsequent description, alternative embodiments
may be conceived that may have a structure and method as disclosed herein, and
such alternative embodiments may be used without departing from the principle
of the disclosure as claimed herein.
A unidirectional power flow based grid tied system comprises of: a
unidirectional DC-DC converter (101) wherein input port of the said converter
connected to the DC power source(s) (102); a capacitor(s) (103) coupled to the
output of the said DC-DC converter(101); a VSC (104) interlinked the capacitor
(103) & input of the filter (105); a relay (106) coupled to the output of the filter

(105) to establish connection between grid (107) & filter (105); a VSC (108)
coupled to DC energy source(s) (102) routed prior to DC-DC converter (101); a
motor (109) having input port coupled to output port of VSC (108); a control
card (110) connected to VSC (104), VSC (108) & DC-DC converter (101) to
control power distribution.
According to one of the embodiment of the invention a unidirectional power
flow based grid tied system comprises of: a unidirectional DC-DC converter
(101) wherein input port of the said converter connected to the DC power
source(s) (102); a capacitor (103) coupled to the output of the said DC-DC
converter(101); a VSC(104) interlinked the capacitor(103) & input of the
filter(105); a relay(106) coupled to the output of the filter(105) to establish
connection between grid(107) & filter(105); a VSC(108) coupled to DC energy
source(s) routed prior to VSC(104); a motor (109) having input port coupled to
output port of VSC(108) ; a control card(110) connected to VSC(104),
VSC(108) & DC-DC converter (101) to control power distribution.
Typically said VSC(108) serves as a variable frequency drive and only be run
from available DC energy sources and has the highest priority
Typically said VSC(104) export energy to grid & does not draw energy from
grid.
Typically said unidirectional DC-DC converter(101) further comprises of
Inductor(s), Capacitor(s), Switch(es) & Diode(s).
Typically said VSC(104), VSC(108) & DC-DC converter(101) communicate to
each other via control card(s) (110) for managing power flow.
The system is working as fallows.
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There are two VSCs serving the overall functionalities of motor running and
feeding the power into the grid, as well as the present invention incorporated
with unidirectional DC-DC converter(101), which ensures the unidirectional
power flow from renewable energy sources to grid side, it means pumping
operation is not possible by taking power from grid.
There are four modes of operation in the present invention. The Mode 1
corresponds to the variable frequency drive like operation of the VSC(108) as it
performs like standalone system. This mode activated by control card(110)
when the available power from DC power sources is less than required power at
motor side, then all available power is supplied to the motor(109). In this mode
VSC(108) runs at variable frequency to perform maximum power point tracking
(MPPT).
The Mode II is activated by control card(110), when motor(109) is off. In this
mode the VSC(104) acts as a grid tie inverter and feed the power into the
grid(107). A net meter or export meter is connected on the grid side to take care
the amount of energy exported.
Mode III is activated by control card(110) when available solar power is more
than motor’s (109) power requirement. In this mode the excess power is fed into
the grid(107). Moreover this characteristic of the system better utilise the
available energy from renewable sources, furthermore this system does not
involve the cost of battery as it directly supplies power to the grid.
Mode IV is activated by control card(110) when solar power is not available but
grid(107) is available. In this mode system disconnects itself from the grid(107)
and system shut down is carried out.