Claims:WE CLAIM
1. A power generation system (100, 200, 300, 400, 500, 600), comprising:
a doubly-fed induction generator (DFIG) (104) comprising a rotor winding (132) and a stator winding (130), wherein the DFIG (104) is configured to generate an electrical power;
a power electronics unit (105) coupled to the DFIG (104), wherein the power electronics unit (105) comprises a rotor-side converter (106) connected to the rotor winding (132), and a line-side converter (108) connected to the rotor-side converter (106) via a direct current (DC)-link (110), and the line-side converter (108) is connected to the stator winding (130);
at least one of an auxiliary power source (112, 502) and/or a primary energy storage device (114) coupled to the power electronics unit (105); and
a back-up power sub-system (116, 204, 302, 402, 512, 604) coupled to the DFIG (104), the power electronics unit (105), the auxiliary power source (112, 502), the primary energy storage device (114), or combinations thereof, the back-up power sub-system (116, 204, 302, 402, 512, 604) comprising:
a back-up power converter (144);
a plurality of switches (148) connected to at least one of the rotor winding (132), the back-up power converter (144), the rotor-side converter (106), the line-side converter (108), the auxiliary power source (112, 502), and the primary energy storage device (114); and
a back-up controller (150) operatively coupled to the plurality of switches (148) and configured to disconnect the rotor-side converter (106) from the rotor winding (132) and connect the back-up power converter (144) to the to the rotor winding (132) via one or more first switches (152a, 152b, 152c) of the plurality of switches (148) in an event of a fault condition associated with one or more of the power electronics unit (105), the primary energy storage device (114), or a power distribution network to supply a DC excitation power to the rotor winding (132) of the DFIG (104) from the back-up power converter (144) to enable the DFIG (104) to generate the electrical power in the event of the fault condition.

2. The power generation system (100, 200, 300, 400, 500, 600) as claimed in claim 1, wherein the at least one of the auxiliary power source (112, 502) and the primary energy storage device (114) is coupled to the DC-link (110) between the rotor-side converter (106) and the line-side converter (108).

3. The power generation system (100, 200, 300, 400, 500, 600) as claimed in claim 1, wherein the fault condition comprises a failure, a malfunction, an over-current flow, a thermal overload, or combinations thereof, associated with one or more of the rotor-side converter (106), the line-side converter (108), the primary energy storage device (114), or the power distribution network.

4. The power generation system (100, 200, 300, 400, 500, 600) as claimed in claim 1, wherein the back-up controller (150) is configured to determine if the fault condition exists for one or more of the rotor-side converter (106), the line-side converter (108), and the primary energy storage device (114).

5. The power generation system (100, 200, 300, 400, 500, 600) as claimed in claim 1, wherein the plurality of switches (148) comprises one or more second switches (154a, 154b, 154c) connected between the line-side converter (108) and the stator winding (130), wherein the back-up controller (150) is further configured to:
determine if the fault condition exists for the line-side converter (108); and
disconnect, in response to determining that the fault condition exists for the line-side converter (108), the line-side converter (108) from the stator winding (130) by controlling switching of the one or more second switches (154a, 154b, 154c).

6. The power generation system (100, 200, 300, 400, 500, 600) as claimed in claim 1, wherein the plurality of switches (148) comprises one or more second switches (154a, 154b, 154c) connected between the line-side converter (108) and the stator winding (130), wherein the back-up controller (150) is further configured to:
determine if the fault condition exists in the power distribution network; and
disconnect, in response to determining that the fault condition exists in the power distribution network, the line-side converter (108) from the stator winding (130) by controlling switching of the one or more second switches (154a, 154b, 154c).

7. The power generation system (200) as claimed in claim 1, wherein the back-up power sub-system (204) further comprises a back-up energy storage device (206) connected to the back-up power converter (144) to supply a DC power to the back-up energy storage device (206), and wherein the back-up power converter (144) is configured to generate the DC excitation power using the DC power received from the back-up energy storage device (206).

8. The power generation system (300) as claimed in claim 1, wherein the plurality of switches (148) comprises one or more third switches (304a, 304b) connected between the primary energy storage device (114) and the back-up power converter (144), wherein, in the event of the fault condition, the back-up controller (150) is further configured to control switching of the one or more third switches (304a, 304b) to connect the primary energy storage device (114) to the back-up power converter (144), and wherein the back-up power converter (144) is configured to generate the DC excitation power using a DC power received from the primary energy storage device (114).

9. The power generation system (400) as claimed in claim 1, wherein the plurality of switches (148) comprises one or more fourth switches (404a, 404b)connected between the auxiliary power source (112, 502) and the back-up power converter (144), wherein, in the event of the fault condition, the back-up controller (150) is further configured to control switching of the one or more fourth switches (404a, 404b) to connect the auxiliary power source (112, 502) to the back-up power converter (144), and wherein the back-up power converter (144) is configured to generate the DC excitation power using electrical power received from the auxiliary power source (112, 502).

10. The power generation system (500) as claimed in claim 1, wherein the auxiliary power source (502) comprises one or more photovoltaic modules (504, 506), wherein each photovoltaic module of the one or more photovoltaic modules (504, 506) comprises a set of photovoltaic panels, and wherein each photovoltaic module of the one or more photovoltaic modules (504, 506) is coupled to the DC-link (110) via a DC-DC converter.

11. The power generation system (500) as claimed in claim 10, wherein the plurality of switches (148) comprises one or more fifth switches (514a, 514b) connected between at least one photovoltaic module of the one or more photovoltaic modules (504, 506) and the back-up power converter (144), wherein, in the event of the fault condition, the back-up controller (150) is further configured to control switching of the one or more fifth switches (514a, 514b) to connect the at least one photovoltaic module (504, 506) to the back-up power converter (144), and wherein the back-up power converter (144) is configured to generate the DC excitation power using a DC power received from the at least one photovoltaic module (504, 506).

12. The power generation system (600) as claimed in claim 1, further comprising a prime mover coupled to the DFIG (104).

13. The power generation system (600) as claimed in claim 12, wherein the prime mover comprises an engine (202) and an energy storage device (602) connected to the engine (202).

14. The power generation system (600) as claimed in claim 12, wherein the plurality of switches (148) comprises one or more sixth switches (606a, 606b) connected between the energy storage device (602) and the back-up power converter (144), wherein, in the event of the fault condition, the back-up controller (150) is further configured to control switching of the one or more sixth switches (606a, 606b) to connect the energy storage device (602) to the back-up power converter (144), and wherein the back-up power converter (144) is configured to generate the DC excitation power using a DC power received from the energy storage device (602).

15. A method for operating a power generation system (100, 200, 300, 400, 500, 600) comprising a doubly-fed induction generator (DFIG) (104), a power electronics unit (105) coupled to the DFIG (104), at least one of an auxiliary power source (112, 502) and/or a primary energy storage device (114), wherein the power electronics unit (105) comprises a rotor-side converter (106) and a line-side converter (108) connected to each other via a direct current (DC) link (110), the method comprising:
determining if a fault condition exists for with one or more of the power electronics unit (105), the primary energy storage device (114), or a power distribution network;
disconnecting the rotor-side converter (106) from a rotor winding (132) and connecting a back-up power converter (144) to the to the rotor winding (132) of the DFIG (104) by controlling switching of one or more first switches (152a, 152b, 152c) of a plurality of switches (148) if the fault condition exists, wherein the plurality of switches (148) is connected to at least one of the rotor winding (132), the back-up power converter (144), the rotor-side converter (106) and the line-side converter (108), the auxiliary power source (112, 502), and the primary energy storage device (114); and
supplying a DC excitation power to the rotor winding (132) of the DFIG (104) from the back-up power converter (144) to enable the DFIG (104) to generate electrical power in an event of the fault condition.

16. The method as claimed in claim 15, further comprising:
determining if the fault condition exists for the line-side converter (108); and
disconnecting the line-side converter (108) from a stator winding (130) of the DFIG (104) by controlling switching of one or more second switches (154a, 154b, 154c) of the plurality of switches (148) in response to determining that the fault condition exists for the line-side converter (108), wherein the one or more second switches (154a, 154b, 154c) are connected between the line-side converter (108) and the stator winding (130).
17. The method as claimed in claim 15, further comprising generating the DC excitation power by the back-up power converter (144) using a DC power received from a back-up energy storage device (206), wherein the back-up energy storage device (206) is connected to the back-up power converter (144).

18. The method as claimed in claim 15, further comprising:
connecting the primary energy storage device (114) to the back-up power converter (144) by controlling switching of one or more third switches (304a, 304b); and
generating the DC excitation power by the back-up power converter (144) using a DC power received from the primary energy storage device (114).

19. The method as claimed in claim 15, further comprising:
connecting the auxiliary power source (112, 502) to the back-up power converter (144) by controlling switching of one or more fourth switches (404a, 404b); and
generating the DC excitation power by the back-up power converter (144) using electrical power received from the auxiliary power source (112, 502).

20. The method as claimed in claim 15, wherein the auxiliary power source (502) comprises one or more photovoltaic modules (504, 506), wherein the method further comprises:
connecting at least one photovoltaic module (504, 506) of the one or more photovoltaic modules (504, 506) to the back-up power converter (144) by controlling switching of one or more fifth switches (514a, 514b); and
generating the DC excitation power by the back-up power converter (144) using electrical power received from the at least one photovoltaic module (504, 506).

21. The method as claimed in claim 15, wherein the power generation system (600) comprises an engine (202) and an energy storage device (602) connected to the engine (202), wherein the method further comprises:
connecting the energy storage device (602) to the back-up power converter (144) by controlling switching of one or more sixth switches (606a, 606b); and
generating the DC excitation power by the back-up power converter (144) using electrical power received from the energy storage device (602).
, Description:TECHNICAL FIELD
[0001] Embodiments of the present specification generally relate to a power generation system and in particular, to the power generation system having a back-up power sub-system for facilitating generation of electricity by the power generation system in an event of a certain fault conditions.
BACKGROUND
[0002] Some traditional hybrid power generation systems employ a doubly-fed induction generator (DFIG), a prime mover and an auxiliary power source (e.g., photovoltaic (PV) power source). Further, the DFIG is also coupled to electric grid and/or one or more electrical loads via a rotor-side converter and a line-side converter. During operation of the power generation system, electrical power may be generated by one or both of the DFIG and the auxiliary power source. The electrical power thus generated may be supplied to the electrical loads and/or the electric grid coupled to the power generation system.
[0003] Typically, in certain instances, at least some portion of the electrical power supplied to the electrical loads and/or the electric grid flows through one or both of the rotor-side converter and the line-side converter. Therefore, when a fault occurs with the rotor-side converter, the line-side converter, or a controller associated with the rotor-side converter and/or the line-side converter during operation of such traditional hybrid power generation system, the traditional hybrid system is typically configured to be shut down or disconnected from the electrical loads. Consequently, the supply of electrical power to the electrical loads and/or to the electrical grid is interrupted. Further, when the traditional hybrid power generation system is disconnected or has to shut down due to such fault, the electrical power generated by the auxiliary power source is also wasted once a battery connected in the traditional hybrid power generation system is charged. Moreover, when such traditional hybrid systems are installed in remote locations and such fault occurs, replacing faulty components or addressing the fault remains challenging and time-consuming task.
BRIEF DESCRIPTION
[0004] In accordance with one embodiment of the present specification, a power generation system is presented. The power generation system includes a doubly-fed induction generator (DFIG) having a rotor winding and a stator winding, wherein the DFIG is configured to generate an electrical power. The power generation system further includes a power electronics unit coupled to the DFIG, wherein the power electronics unit includes a rotor-side converter connected to the rotor winding, and a line-side converter connected to the rotor-side converter via a direct current (DC)-link, and the line-side converter is connected to the stator winding. Furthermore, the power generation system includes at least one of an auxiliary power source and/or a primary energy storage device coupled to the power electronics unit. Moreover, the power generation system includes a back-up power sub-system coupled to the DFIG, the power electronics unit, the auxiliary power source, the primary energy storage device, or combinations thereof. The back-up power sub-system includes a back-up power converter. The back-up power sub-system further includes a plurality of switches connected to at least one of the rotor winding, the back-up power converter, the rotor-side converter, the line-side converter, the auxiliary power source, and the primary energy storage device. The back-up power sub-system also includes a back-up controller operatively coupled to the plurality of switches and configured to disconnect the rotor-side converter from the rotor winding and connect the back-up power converter to the to the rotor winding via one or more first switches of the plurality of switches in an event of a fault condition associated with one or more of the power electronics unit, the primary energy storage device, or a power distribution network to supply a DC excitation power to the rotor winding of the DFIG from the back-up power converter to enable the DFIG to generate the electrical power in the event of the fault condition.
[0005] In accordance with one embodiment of the present specification, a method for operating a power generation system is presented. The power generation system includes a DFIG, a power electronics unit coupled to the DFIG, at least one of an auxiliary power source and/or a primary energy storage device, wherein the power electronics unit includes a rotor-side converter and a line-side converter connected to each other via a DC-link. The method includes determining if a fault condition exists for with one or more of the power electronics unit, the primary energy storage device, or a power distribution network. The method further includes disconnecting the rotor-side converter from a rotor winding and connecting a back-up power converter to the to the rotor winding of the DFIG by controlling switching of one or more first switches of a plurality of switches if the fault condition exists, wherein the plurality of switches is connected to at least one of the rotor winding, the back-up power converter, the rotor-side converter and the line-side converter, the auxiliary power source, and the primary energy storage device. Moreover, the method includes supplying a DC excitation power to the rotor winding of the DFIG from the back-up power converter to enable the DFIG to generate electrical power in the event of the fault condition.
DRAWINGS
[0006] These and other features, aspects, and advantages of the present specification will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
[0007] FIG. 1 is a block diagram representation of a power generation system, in accordance with one embodiment of the present specification;
[0008] FIG. 2 is a block diagram representation of a power generation system, in accordance with one embodiment of the present specification;
[0009] FIG. 3 is a block diagram representation of a power generation system, in accordance with one embodiment of the present specification;
[0010] FIG. 4 is a block diagram representation of a power generation system, in accordance with one embodiment of the present specification;
[0011] FIG. 5 is a block diagram representation of a power generation system, in accordance with one embodiment of the present specification;
[0012] FIG. 6 is a block diagram representation of a power generation system, in accordance with one embodiment of the present specification; and
[0013] FIG. 7 is a flow diagram of a method for operating the power generation system of any of the FIGs. 1-6, in accordance with one embodiment of the present specification.
DETAILED DESCRIPTION
[0014] In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made to achieve the developer’s specific goals such as compliance with system-related and business-related constraints.
[0015] When describing elements of the various embodiments of the present specification, the articles “a”, “an”, and “the” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
[0016] As used herein, the terms “may” and “may be” indicate a possibility of an occurrence within a set of circumstances; a possession of a specified property, characteristic or function; and/or qualify another verb by expressing one or more of an ability, capability, or possibility associated with the qualified verb. Accordingly, usage of “may” and “may be” indicates that a modified term is apparently appropriate, capable, or suitable for an indicated capacity, function, or usage, while taking into account that in some circumstances, the modified term may sometimes not be appropriate, capable, or suitable.
[0017] In accordance with one embodiment of the present specification, a power generation system is presented. The power generation system includes a DFIG having a rotor winding and a stator winding, wherein the DFIG is configured to generate an electrical power. The power generation system further includes a power electronics unit coupled to the DFIG, wherein the power electronics unit includes a rotor-side converter connected to the rotor winding, and a line-side converter connected to the rotor-side converter via a DC-link, and the line-side converter is connected to the stator winding. Furthermore, the power generation system includes at least one of an auxiliary power source and/or a primary energy storage device coupled to the power electronics unit. Moreover, the power generation system includes a back-up power sub-system coupled to the DFIG, the power electronics unit, the auxiliary power source, the primary energy storage device, or combinations thereof.
[0018] The back-up power sub-system includes a back-up power converter. The back-up power sub-system further includes a plurality of switches connected to at least one of the rotor winding, the back-up power converter, the rotor-side converter, the line-side converter, the auxiliary power source, and the primary energy storage device. The back-up power sub-system also includes a back-up controller operatively coupled to the plurality of switches and configured to disconnect the rotor-side converter from the rotor winding and connect the back-up power converter to the to the rotor winding via one or more first switches of the plurality of switches in an event of a fault condition associated with one or both of the power electronics unit and the primary energy storage device to supply a DC excitation power to the rotor winding of the DFIG from the back-up power converter to enable the DFIG to generate the electrical power in the event of the fault condition.
[0019] FIG. 1 is a block diagram representation of a power generation system 100, in accordance with one embodiment of the present specification. The power generation system 100 may include a prime mover 102, a DFIG 104, a power electronics unit 105 having a rotor-side converter 106 a line-side converter 108, and a DC-link 110, a supervisory controller 111, one or both of an auxiliary power source 112 or a primary energy storage device 114, and a back-up power sub-system 116. The power generation system 100 may be configured to generate an alternating current (AC) electrical power which may be accessible from an output power port 118 of the power generation system 100.
[0020] In some embodiments, the output power port 118 of the power generation system 100 may be connected to a power distribution network (not shown). In some embodiments, the power distribution network may include an electric grid (not shown). The power generation system 100 when connected to the electric grid is also referred to as a grid connected power generation system. The electric grid may be representative of an interconnected network of electrical power sources, electrical power processing systems, and an electrical power distribution system for delivering a grid power (e.g., electricity) from one or more power generation stations to consumers through high/medium voltage transmission lines. By way of example, the electric grid may be a utility power grid and/or a micro grid.
[0021] In some embodiments, the power distribution network may include one or more electrical loads connected to the output power port 118 of the power generation system 100. In such an application when the power generation system 100 is not connected to the electric grid and connected to the electrical loads, the power generation system 100 may be referred to as an islanded power generation system or an isolated power generation system. By way of example, the islanded power generation system may be deployed where connection to the electric grid is not desired or the electric grid is not available. In such a configuration, the output power port 118 of the power generation system 100 may be coupled to an electrical load (not shown). The electrical load may include one or more devices/equipment that consume electricity.
[0022] As depicted in FIG. 1, the DFIG 104 is mechanically coupled to the prime mover 102. The DFIG 104 is also electrically coupled to a point of common coupling PCC 120 via a link 122 and to the rotor-side converter 106 via a link 124. The line-side converter 108 may be electrically coupled to the PCC 120 via a link 126 which in turn connects the line-side converter 108 to a stator winding (described later) of the DFIG 104. In some embodiments, the line-side converter 108 is electrically coupled to the PCC 120 via the link 126 through a transformer (not shown). Each of the links 122, 124, and 126 may be a multi-phase link, for example, a three-phase electrical link as shown in FIG. 1. The PCC 120 may be connected to the output power port 118 of the power generation system 100. In some embodiments, the power generation system 100 may optionally include a transformer 128 connected between the PCC 120 and the output power port 118.
[0023] The prime mover 102 is coupled to the DFIG 104 and configured to operate the DFIG 104. In particular, the prime mover 102 may be configured to aid in imparting a rotational motion to a rotary element (e.g., a rotor) of the DFIG 104. The prime mover 102 may be an internal combustion engine or an external combustion engine. Non-limiting examples of the internal combustion engine that may be used as the prime mover 102 may include a reciprocating engine such as a diesel engine or a petrol engine, or a rotary engine such as a compressor or a gas turbine. Moreover, the prime mover 102 may be operated by combustion of various fuels including, but not limited to, diesel, natural gas, petrol, liquefied petroleum gas (LPG), liquefied natural gas (LNG), biogas, producer gas, and the like. The prime mover 102 may also be operated using waste heat cycle. In certain other embodiments, the prime mover 102 may be a wind-turbine. Another non-limiting example of the prime mover 102 may include a hydro turbine. It is to be noted that the scope of the present specification is not limited with respect to the types of fuel and the prime mover 102 employed in the power generation system 100.
[0024] The DFIG 104 includes a stator 134 and a rotor 136. The DFIG 104 is mechanically coupled to the prime mover 102 and is operable via the prime mover 102. For example, the rotor 136 of the DFIG 104 is mechanically coupled to a rotor (e.g., a crank shaft or a wind turbine rotor) of the prime mover 102 via a shaft 138 such that a rotation of the shaft 138 causes a rotation of the rotor 136 of the DFIG 104.
[0025] The DFIG 104 further includes a stator winding 130 that is wound on the stator 134 and a rotor winding 132 that is wound on the rotor 136. In some embodiments, both the stator winding 130 and the rotor winding 132 may be multi-phase windings such as a three-phase winding. By way of example, the stator winding 130 includes three phase windings and the rotor winding 132 also includes three phase windings (hereinafter referred to as rotor phase windings). The rotor phase windings are marked using reference numerals 132a, 132b, and 132c. By way of example, the rotor phase windings 132a, 132b, 132c may be connected in a star configuration where one terminal of each of the rotor phase windings 132a, 132b, 132c is connected to each other and the remaining one terminal of each rotor phase windings 132a, 132b, 132c is connected to a corresponding switch (described later).
[0026] During an operation of the power generation system 100, the rotor 136 of the DFIG 104 is operated at a rotational speed which may be a synchronous speed, a sub-synchronous speed, or a super-synchronous speed. The rotational speed of the rotor 136 is also hereinafter referred to as an operating speed (Nr) of the rotor 136 or the operating speed (Nr) of the DFIG 104. In one example, the synchronous speed may be defined using equation (1).
Equation (1)
[0027] In equation (1), represents the synchronous speed of the rotor 136, represents number poles in the rotor 136, and represents a frequency of a stator voltage (i.e., voltage at the stator winding 130). Accordingly, a sub-synchronous speed of the rotor 136 is defined as a speed that is lower than the synchronous speed of the rotor 136. Therefore, when the operating speed (Nr) of the rotor 136 is sub- synchronous speed, the DFIG 104 is considered to be operated in a sub-synchronous mode. Similarly, a super-synchronous speed of the rotor 136 is defined as a speed that is higher than the synchronous speed of the rotor 136. Accordingly, when the operating speed (Nr) of the rotor 136 is the super-synchronous speed, the DFIG 104 is considered to be operated in a super-synchronous mode.
[0028] The DFIG 104 is configured to generate an electrical power at the stator winding 130 depending on the operating speed (Nr) of the rotor 136. The electrical power that is generated at the stator winding 130 is hereinafter also referred to as a stator power (PStator). Further, the DFIG 104 is configured to generate or absorb electrical power at the rotor winding 132 depending on the operating speed (Nr) of the rotor 136. For example, the DFIG 104 is configured to generate an electrical power at the rotor winding 132 when the rotor 136 is operated at the super-synchronous speed. The DFIG 104 is configured to absorb the electrical power at the rotor winding 132 when the rotor 136 is operated at the sub-synchronous speed. The electrical power that is generated or absorbed at the rotor winding 132 is hereinafter also referred to as a slip power (PSlip) or a rotor power (PRotor). The magnitude of the rotor power (PRotor) is dependent on a slip value S of the DFIG 104. In one embodiment, the slip value S may be determined using equation (2).
Equation (2)
[0029] Moreover, the rotor power (PRotor) may be determined using equation (3).
PRotor=S * PStator Equation (3)
[0030] The rotor-side converter 106 is electrically coupled to the rotor winding 132 of the DFIG 104 via the link 124. The rotor-side converter 106 may be an AC-DC converter and configured to convert an AC power into a DC power and vice-versa. The line-side converter 108 may be a DC-AC converter and configured to convert the DC power into an AC power and vice-versa. In some embodiments, each of the rotor-side converter 106 and the line-side converter 108 may include one or more switches, for example, semiconductor switches, configured to facilitate power conversion from AC to DC or vice-versa. Further, the rotor-side converter 106 is electrically coupled to the line-side converter 108 via the DC-link 110. The DC-link 110 includes a plurality of electrical conductors/terminals and at least one DC-bus capacitor 113 electrically coupled between two conductors/terminals of the DC-link 110.
[0031] In some embodiments, the power generation system 100 may also include the auxiliary power source 112 coupled to the power electronics unit 105. The auxiliary power source 112 is capable of supplying a DC power to the DC-link 110. Non-limiting examples of the auxiliary power source 112 may include a photovoltaic (PV) power source, a battery, a fuel cell, a renewable energy based power generator, a non-renewable energy based power generator, or combinations thereof. The PV power source may include one or more PV modules. The PV modules may be arranged in a series connection, parallel connection, or a series-parallel connection. Each of the PV modules may include a plurality of PV panels arranged in a series connection, parallel connection, or a series-parallel connection. The PV power source having such PV modules may generate a DC power depending on solar insolation, weather conditions, and/or time of the day.
[0032] Further, in various embodiments described herein, the auxiliary power source 112 is shown as coupled to the DC-link 110. In some embodiments, the auxiliary power source 112 may be directly coupled to the DC-link 110. In certain embodiments, the auxiliary power source 112 may be coupled to the DC-link 110 via a DC-DC converter 140. The DC-DC converter 140 may be operated as a buck converter, a boost converter, or a buck-boost converter. Although not shown in FIG. 1, in some other embodiments, the auxiliary power source 112 may be coupled to power electronics unit 105 at locations other than the DC-link 110, directly or via an appropriate power converter, without limiting the scope of the present specification. By way of example, the auxiliary power source 112 may be coupled to the PCC 120, the output power port 118, or at any point between the PCC 120 and the output power port 118 directly or via appropriate power converter, for example, a DC-AC power converter.
[0033] Moreover, in certain embodiments, the primary energy storage device 114 may be coupled to the power electronics unit 105, for example, at the DC-link 110 via a DC-DC converter 142, as shown in FIG. 1. In some other embodiments, the primary energy storage device 114 may be directly coupled to the DC-link 110. Although not shown in FIG. 1, in some other embodiments, the primary energy storage device 114 may be coupled to power electronics unit 105 at locations other than the DC-link 110, directly or via an appropriate power converter, without limiting the scope of the present specification. By way of example, the primary energy storage device 114 may be coupled to the PCC 120, the output power port 118, or at any point between the PCC 120 and the output power port 118 directly or via appropriate power converter, for example, a DC-AC power converter. The primary energy storage device 114 may include one or more batteries, capacitors, or a combination thereof. The primary energy storage device 114 may be configured to supply a DC power to the DC-link 110 or absorb the DC-power from the DC-link 110. The DC-DC converter 142 may be operated as a buck converter, a boost converter, or a buck-boost converter.
[0034] The power generation system 100 further includes the supervisory controller 111 configured to control operation of the power generation system 100. The supervisory controller 111 may include a specially programmed general-purpose computer, an electronic processor such as a microprocessor, a digital signal processor, and/or a microcontroller. Further, the supervisory controller 111 may include input/output ports, and a storage medium, such as an electronic memory. Various examples of the microprocessor include, but are not limited to, a reduced instruction set computing (RISC) architecture type microprocessor or a complex instruction set computing (CISC) architecture type microprocessor. Further, the microprocessor may be a single-core type or multi-core type. Alternatively, the supervisory controller 111 may be implemented as hardware elements such as circuit boards with processors or as software running on a processor such as a personal computer (PC), or a microcontroller.
[0035] The supervisory controller 111 may be operatively coupled to one or more of the prime mover 102, the rotor-side converter 106, the line-side converter 108, the DC-DC converter 140, and the DC-DC converter 142 via wired control lines (depicted via dashed lines in FIG. 1) and/or via wireless communication link(s) to control operations thereof. The wireless communication link(s) may be effected by wireless communication techniques based on Bluetooth®, Wi-Fi® (IEEE 802.11), WiMAX® (IEEE 802.16), Wi-Bro®, cellular communication techniques, such as, but not limited to global system for mobile (GSM) communications or code division multiple access (CDMA), data communication techniques, including, but not limited to, broadband, 2G, 3G, 4G, or 5G.
[0036] Moreover, the power generation system 100 includes the back-up power sub-system 116 coupled to the DFIG 104, the power electronics unit 105, the auxiliary power source 112, the primary energy storage device 114, or combinations thereof. In some embodiments, the back-up power sub-system 116 may include a back-up power converter 144, a back-up power source 146, a plurality of switches 148, and a back-up controller 150.
[0037] The back-up power source 146 may be any suitable power source capable of supplying electrical power to the back-up power converter 144, receiving electrical power from the back-up power converter 144, or both. In some embodiments, the back-up power source 146 may be a back-up energy storage device (see FIG. 2) different from the primary energy storage device 114. In some other embodiments, the back-up power source 146 may be representative of the primary energy storage device 114 (see FIG. 3). In some other embodiments, the back-up power source 146 may be representative of the auxiliary power source 112 (see FIG. 4). In some other embodiments, the back-up power source 146 may be representative of at least one PV module of the auxiliary power source 112 (see FIG. 5). In certain embodiments, the back-up power source 146 may be representative of an energy storage device connected to the prime mover 102 (e.g., an engine, see FIG. 6).
[0038] In some embodiments, the back-up power converter 144 may be capable of supplying a DC excitation power (e.g., voltage and current) to the rotor winding 132. If the back-up power source 146 for supplying electrical power to the back-up power converter 144 is a DC power source, a DC-DC power converter may be used as the back-up power converter 144. The DC-DC power converter used as the back-up power converter 144 converts the DC power received from the back-up power source 146 to the DC excitation power suitable to be supplied to the rotor winding 132. By way of example, the DC-DC converter may be a boost converter, a buck converter, or a buck-boost converter. However, if the back-up power source 146 for supplying the electrical power to the back-up power converter 144 is an AC power source, an AC-DC power converter may be used as the back-up power converter 144. The AC-DC power converter used as the back-up power converter 144 converts an AC power received from the back-up power source 146 to the DC excitation power suitable to be supplied to the rotor winding 132.
[0039] In some embodiments the plurality of switches 148 may be connected to at least one of the rotor winding 132, the back-up power converter 144, the rotor-side converter 106, the line-side converter 108, the auxiliary power source 112 (see FIGs. 4-5), and the primary energy storage device 114 (see FIG. 3). Non-limiting examples of the switches 148 include metal-oxide-semiconductor field-effect transistors (MOSFETs), gate commutated thyristors, field effect transistors, insulated gate bipolar transistors (IGBT), gate turn-off thyristors, static induction transistors, static induction thyristors, or combinations thereof. Furthermore, materials used to form the switches 148 may include, but are not limited to, silicon (Si), germanium (Ge), SiC, gallium nitride (GaN), or combinations thereof.
[0040] As depicted in FIG. 1, the plurality of switches 148 may include one or more first switches 152a, 152b, 152c (hereinafter collectively referred to as first switches 152a-c) and/or one or more second switches 154a, 154b, 154c (hereinafter collectively referred to as second switches 154a-c). The first switches 152a-c are connected to the rotor winding 132, the back-up power converter 144, and the rotor-side converter 106. By way of example, as shown in FIG. 1, the first switches 152a-c are single-pole double-throw (SPDT) type switches. The first switches 152a-c may be operated in any of the two positions - a first position and a second position. When operated in the first position as shown in FIG. 1, the first switches 152a-c connect the rotor winding 132 with the rotor-side converter 106. When operated in the second position (shown using dashed lines for reference), the first switches 152a and 152b respectively connect two rotor phase windings 132a, 132b of the rotor winding 132 with the back-up power converter 144. Further, the first switch 152c, when operated in the second position (shown using dashed line for reference), connects the rotor phase winding 132c in parallel with the rotor phase winding 132b as the rotor phase windings 132a, 132b, 132c are connected in start configuration. In certain embodiments, the first switch 152c may be a single-pole single-throw (SPST) type switch which when operated in an ON state connects the rotor phase winding 132c with the rotor-side converter 106 and when operated in an OFF state disconnects the rotor phase winding 132c from the rotor-side converter 106.
[0041] In the embodiment of FIG. 1 the first switches 152a-c are arranged to connect the rotor phase windings 132a, 132b with the back-up power converter 144. In certain other embodiments, the first switches 152a-c may be arranged such that any two of the rotor phase windings 132a, 132b, 132c are connected to the back-up power converter 144 and the remaining rotor phase winding may either be connected to any one of the rotor phase windings connected to the back-up power converter 144 or left disconnected from the rotor-side converter 106.
[0042] Further, the second switches 154a-c are connected between the line-side converter 108 and the stator winding 130. More particularly, the second switches 154a-c are connected between the PCC 120 and the line-side converter 108. By way of example, the second switches 154a-c may be single-pole single-throw (SPST) type switches. In certain embodiments, the second switches 154a-c may be implemented in the form of a circuit breaker. The second switches 154a-c when operated in ON states (as shown in FIG. 1) connects the line-side converter 108 with the stator winding 130 via the PCC 120. However, the second switches 154a-c when operated in OFF states disconnects the line-side converter 108 from the stator winding 130.
[0043] The back-up controller 150 may be operatively coupled to the plurality of switches 148 via wired control lines and/or via wireless communication link(s). In particular, the back-up controller 150 may be operatively coupled to control terminals (e.g., gate terminal or any suitable terminal) of the switches 148 to control switching of the switches 148. The back-up controller 150 may include a specially programmed general-purpose computer, an electronic processor such as a microprocessor, a digital signal processor, and/or a microcontroller. Further, the back-up controller 150 may include input/output ports, and a storage medium, such as an electronic memory. Various examples of the microprocessor include, but are not limited to, a reduced instruction set computing (RISC) architecture type microprocessor or a complex instruction set computing (CISC) architecture type microprocessor. Further, the microprocessor may be a single-core type or multi-core type. Alternatively, the back-up controller 150 may be implemented as hardware elements such as circuit boards with processors or as software running on a processor such as a personal computer (PC), or a microcontroller.
[0044] During a normal operation of the power generation system 100, as noted earlier, the DFIG 104 may be configured to generate the stator power at the stator winding 130 and either generate or absorb the slip power at the rotor winding 132. In particular, when the DFIG 104 is operated at the super-synchronous speed, the slip power may be generated at the rotor winding 132 and can be supplied to the PCC 120 via the line-side converter 108. It is to be noted that during the normal operation of the power generation system 100, the first switches 152a-c are operated in the first position and the second switches 154a-c are operated in ON state (as shown in FIG. 1).
[0045] In certain situations, one or more components of the power generation system 100 may experience a fault condition. For example, in certain fault conditions, such power flow via the rotor-side converter 106 and/or the line-side converter 108 may no longer be supported. Non-limiting examples of such fault conditions may include a failure, a malfunction, an over-current flow, a thermal overload, or combinations thereof, associated with one or more of the rotor-side converter 106, the line-side converter 108, and the primary energy storage device 114. In some embodiments, the fault conditions may include a failure, a malfunction, an over-current flow, a thermal overload, or combinations thereof, associated with the supervisory controller 111. The failure may include a complete failure or a partial failure of the one or more of the rotor-side converter 106, the line-side converter 108, the supervisory controller 111, and the primary energy storage device 114. The malfunction may include an operation that deviates from respective normal operating behaviors of the of one or more of the rotor-side converter 106, the line-side converter 108, the supervisory controller 111, and the primary energy storage device 114. In certain embodiments, the fault condition may include any other fault such as a failure, a malfunction, an over-current flow, a thermal overload in the power distribution network outside the power generation system 100, for example, in the electric grid or one or more electrical loads connected to the power generation system 100.
[0046] The back-up power sub-system 116, in accordance with various embodiments of the present specification, facilitates continued generation of electrical power by the power generation system 100 even in the event of the such fault conditions. The back-up controller 150 is configured to determine if the fault condition exists for one or more of the rotor-side converter 106, the line-side converter 108, the supervisory controller 111, and the primary energy storage device 114.
[0047] In some embodiments, to detect the fault condition, the back-up power sub-system 116 includes one or more sensors (not shown) connected to one or more of the rotor-side converter 106, the line-side converter 108, the supervisory controller 111, and the primary energy storage device 114. Non-limiting examples of the sensors may include temperature sensors, current sensors, voltage sensors, or combinations thereof. The sensors are configured to generate electrical signals indicative of temperature, current, and/or voltage corresponding to one or more of the rotor-side converter 106, the line-side converter 108, the supervisory controller 111, and the primary energy storage device 114. Further, the back-up controller 150 is operatively connected to the sensors and receives the electrical signals generated by the sensors. The back-up controller 150 then compares one or more parameters (e.g., voltage, current, phase, etc.) of the electrical signals with predetermined values and/or ranges to determine occurrence of the fault condition(s).
[0048] In certain embodiments, instead of the back-up controller 150, the supervisory controller 111 is configured to determine the occurrence of the fault condition. If the fault condition has occurred, the supervisory controller 111 is configured to communicate a fault condition indicating signal to the back-up controller 150. Upon the receipt of fault condition indicating signal from the supervisory controller 111, the back-up controller 150 may determine that there exists the fault condition.
[0049] Further, in the event of the fault condition associated with one or more of the power electronics unit 105, the primary energy storage device 114, or the supervisory controller 111, the back-up controller 150 may be configured to disconnect the rotor-side converter 106 from the rotor winding 132 and connect the back-up power converter 144 to the to the rotor winding 132 to supply a DC excitation power to the rotor winding 132 of the DFIG 104 from the back-up power converter 144 by controlling switching of the one or more first switches 152a-c. In particular, the back-up controller 150 may be configured to operate the first switches 152a-c in the second position to enable the supply of the DC excitation power to the rotor winding 132 from the back-up power converter 144. By facilitating supply of the DC excitation power to the rotor winding 132, the DFIG 104 is operated as a synchronous generator to enable the DFIG 104 to generate the electrical power in the event of the fault condition.
[0050] Moreover, the back-up controller 150 is configured to determine if the fault condition exists for the line-side converter 108. In response to determining that the fault condition exists for the line-side converter 108, the back-up controller 150 is also configured to disconnect the line-side converter 108 from the stator winding 130 by controlling switching of the one or more second switches 154a-c. By way of example, the back-up controller 150 operates the second switches 154a-c in OFF state to disconnect the line-side converter 108 from the PCC 120 and the stator winding 130.
[0051] In certain situations, while the rotor-side converter 106 has encountered the fault condition, the line-side converter 108 may still be operating in a healthy condition (i.e., without facing the fault condition). In such situation, the line-side converter may still be utilized to facilitate power transfer therethrough. For example, electrical power may be supplied from the DC-link 110 to the PCC 120. Also, if required, the primary energy storage device 114 may also be charged via the line-side converter 108. Additional details of the operations performed by the back-up controller 150 are described in conjunction with FIG. 7.
[0052] FIGs. 2-6 depict block diagram representations of power generation systems, in accordance with various embodiments of the present invention. Power generation systems shown in FIGs. 2-6 are representative of various embodiments of the power generation system 100 of FIG. 1 and include certain components that are similar to the components used in FIG. 1. In FIGs. 2-6, these components have been marked using same reference numerals as used in FIG. 1 and description of such components is not repeated.
[0053] Referring now to FIG. 2, a block diagram representation of a power generation system 200 is presented, in accordance with one embodiment of the present invention. In the embodiment of FIG. 2, an engine 202 is used as a non-limiting example of the prime mover 102. Also, in the description going forward and in remaining power generation system drawings, the engine 202 is used to represent the prime mover 102, for illustrative purpose. However, any other type of prime mover that can impart a rotary motion to the rotor 136 of the DFIG 104 may be used without limiting the scope of the present specification.
[0054] In some embodiments, the engine 202 may be a variable speed engine that can be operated at different speeds to generate any particular power level at the stator winding 130. In certain embodiments, the engine 202 may be a fixed speed engine. The engine 202 may be configured to aid in imparting a rotational motion to the rotor 136 of the DFIG 104. The engine 202 may be an internal combustion engine or an external combustion engine. Non-limiting examples of the internal combustion engine may include a reciprocating engine such as a diesel engine or a petrol engine, or a rotary engine such as a compressor or a gas turbine. Moreover, the engine 202 may be operated by combustion of various fuels including, but not limited to, diesel, natural gas, petrol, liquefied petroleum gas (LPG), liquefied natural gas (LNG), biogas, producer gas, and the like. The engine 202 may also be operated using waste heat cycle. It is to be noted that the scope of the present specification is not limited with respect to the types of fuel and the engine 202 employed in the power generation system 200.
[0055] Further, the power generation system 200 includes a back-up power sub-system 204 that is representative of one embodiment of the back-up power sub-system 116 of FIG. 1. The back-up power sub-system 204 also includes certain components that are similar to the components used in the back-up power sub-system 116 of FIG. 1. For example, the back-up power sub-system 204 may also include the back-up power converter 144, the plurality of switches 148, and the back-up controller 150. In addition, the back-up power sub-system 204 also includes a back-up energy storage device 206 connected to the back-up power converter 144. The back-up energy storage device 206 may be representative of one embodiment of the back-up power source 146. The back-up energy storage device 206 may include one or more batteries, capacitors, or a combination thereof. The back-up energy storage device 206 may supply a DC power to the back-up power converter 144 or receive DC-power from the back-up power converter 144.
[0056] During operation of the power generation system 200, in a similar fashion as previously noted with reference to FIG. 1, in the event of the fault condition associated with one or more of the power electronics unit 105, the primary energy storage device 114, or the supervisory controller 111, the back-up controller 150 may be configured to disconnect the rotor-side converter 106 from the rotor winding 132 and connect the back-up power converter 144 to the to the rotor winding 132 to supply the DC excitation power to the rotor winding 132 of the DFIG 104 by controlling switching of the one or more first switches 152a-c. In the embodiment of FIG. 2, the back-up power converter 144 is configured to generate the DC excitation power using the DC power received from the back-up energy storage device 206. By facilitating supply of the DC excitation power to the rotor winding 132, the DFIG 104 is operated as a synchronous generator to enable the DFIG 104 to generate the electrical power in the event of the fault condition.
[0057] FIG. 3 is a block diagram representation of a power generation system 300, in accordance with one embodiment of the present invention. In the embodiment of FIG. 3, the engine 202 is used as a prime mover as shown in FIG. 2. The power generation system 300 includes a back-up power sub-system 302 that is representative of one embodiment of the back-up power sub-system 116 of FIG. 1. The back-up power sub-system 302 includes certain components that are similar to the components used in the back-up power sub-system 116 of FIG. 1 description of which is not repeated herein. In particular, in the embodiment of FIG. 3, the primary energy storage device 114 is configured to be used as the back-up power source such as the back-up power source. To enable such a use of the primary energy storage device 114 as the back-up power source, the switches 148 in the back-up power sub-system 302 may additionally include one or more third switches 304a, 304b. The third switches 304a, 304b may be similar to any of the second switches 154a-c. The third switches 304a, 304b are connected between the primary energy storage device 114 and the back-up power converter 144, as shown in FIG. 3. Also, the back-up controller 150 is operatively coupled to the third switches 304a, 304b to control the switching of the third switches 304a, 304b.
[0058] During operation of the power generation system 300, when no fault condition exists, the third switches 304a, 304b are operated in OFF states (position shown using dashed lines for reference). However, in the event of the fault condition, the back-up controller 150 is configured to control switching of the third switches 304a, 304b to connect the primary energy storage device 114 to the back-up power converter 144. In particular, the back-up controller 150 sends control signals to the third switches 304a, 304b such that the third switches 304a, 304b are operated in the ON states as shown in FIG. 3, thereby connecting the primary energy storage device 114 to the back-up power converter 144. In some embodiments, prior to connecting the primary energy storage device 114 to the back-up power converter 144 via the third switches 304a, 304b, the primary energy storage device 114 may be disconnected from the DC-link 110. By way of example, the primary energy storage device 114 may be disconnected from the DC-link 110 by stopping/discontinuing control signals to the DC-DC converter 142. In another example configurations, one or more switches (not shown) may be disposed between the primary energy storage device 114 and the DC-DC converter 142, between the DC-DC converter 142 and the DC-link 110, or between the primary energy storage device 114 and the DC-link 110 (if the primary energy storage device 114 is directly connected to the DC-link 110), where these switches are operated in OFF-states to disconnect the primary energy storage device 114 from the DC-link 110.
[0059] Moreover, in the event of the fault condition, the back-up controller 150 is configured to control switching of the one or more first switches 152a-c to disconnect the rotor-side converter 106 from the rotor winding 132 and to connect the back-up power converter 144 to the rotor winding 132 in a similar fashion as described in FIG. 1. Therefore, by operating the third switches 304a, 304b in the ON state and the first switches 152a-c the second position, electrical connection between the primary energy storage device 114 and the rotor winding 132 is established.
[0060] As the primary energy storage device 114 is connected to the back-up power converter 144 via the third switches 304a, 304b, a DC power from the primary energy storage device 114 is supplied to the back-up power converter 144. The back-up power converter 144 is configured to generate the DC excitation power using a DC power received from the primary energy storage device 114 which may be supplied to the rotor winding 132. By facilitating supply of the DC excitation power to the rotor winding 132, the DFIG 104 is operated as a synchronous generator to enable the DFIG 104 to generate the electrical power in the event of the fault condition.
[0061] FIG. 4 is a block diagram representation of a power generation system 400, in accordance with one embodiment of the present invention. In the embodiment of FIG. 4, the engine 202 is used as a prime mover as shown in FIG. 2. The power generation system 400 includes a back-up power sub-system 402 that is representative of one embodiment of the back-up power sub-system 116 of FIG. 1. The back-up power sub-system 402 includes certain components that are similar to the components used in the back-up power sub-system 116 of FIG. 1 description of which is not repeated herein. In particular, in the embodiment of FIG. 4, the auxiliary power source 112 is configured to be used as the back-up power source such as the back-up power source 146. To enable such a use of the auxiliary power source 112 as the back-up power source, the switches 148 in the back-up power sub-system 402 may additionally include one or more fourth switches 404a, 404b. The fourth switches 404a, 404b may be similar to any of the second switches 154a-c. The fourth switches 404a, 404b are connected between the auxiliary power source 112 and the back-up power converter 144, as shown in FIG. 4. Also, the back-up controller 150 is operatively coupled to the fourth switches 404a, 404b to control the switching of the fourth switches 404a, 404b.
[0062] During operation of the power generation system 400, when no fault condition exists, the fourth switches 404a, 404b are operated in OFF states (position shown using dashed lines for reference). However, in the event of the fault condition, the back-up controller 150 is configured to control switching of the fourth switches 404a, 404b to connect the auxiliary power source 112 to the back-up power converter 144. In particular, the back-up controller 150 sends control signals to the fourth switches 404a, 404b such that the fourth switches 404a, 404b are operated in the ON states as shown in FIG. 4, thereby connecting the auxiliary power source 112 to the back-up power converter 144. In some embodiments, prior to connecting the auxiliary power source 112 to the back-up power converter 144 via the fourth switches 404a, 404b, the auxiliary power source 112 may be disconnected from the DC-link 110. By way of example, the auxiliary power source 112 may be disconnected from the DC-link 110 by stopping/discontinuing control signals to the DC-DC converter 140. In another example configurations, one or more switches (not shown) may be disposed between the auxiliary power source 112 and the DC-DC converter 140, between the DC-DC converter 140 and the DC-link 110, or between the auxiliary power source 112 and the DC-link 110 (if the auxiliary power source 112 is directly connected to the DC-link 110), where these switches are operated in OFF-states to disconnect the auxiliary power source 112 from the DC-link 110.
[0063] Moreover, in the event of the fault condition, the back-up controller 150 is configured to control switching of the one or more first switches 152a-c to disconnect the rotor-side converter 106 from the rotor winding 132 and to connect the back-up power converter 144 to the rotor winding 132 in a similar fashion as described in FIG. 1. Therefore, by operating the fourth switches 404a, 404b in the ON state and the first switches 152a-c the second position, electrical connection between the auxiliary power source 112 and the rotor winding 132 is established.
[0064] As the auxiliary power source 112 is connected to the back-up power converter 144 via the fourth switches 404a, 404b, a DC power from the auxiliary power source 112 is supplied to the back-up power converter 144. The back-up power converter 144 is configured to generate the DC excitation power using a DC power received from the auxiliary power source 112 which may be supplied to the rotor winding 132. By facilitating supply of the DC excitation power to the rotor winding 132, the DFIG 104 is operated as a synchronous generator to enable the DFIG 104 to generate the electrical power in the event of the fault condition.
[0065] FIG. 5 is a block diagram representation of a power generation system 500, in accordance with one embodiment of the present invention. In the embodiment of FIG. 5 also, the engine 202 is used as a prime mover as shown in FIG. 2. Further, an auxiliary power source 502 used in the power generation system 500 of FIG. 5 is representative of one embodiment of the auxiliary power source 112 of FIG. 1. In some embodiments, the auxiliary power source 502 may include one or more PV modules 504, 506. Each of the PV modules 504, 506 may include a set of PV panels (not shown). The PV panels in each of the PV modules 504, 506 may be connected in series with each other, in parallel with each other, or connected in series-parallel combinations with each other. For ease of illustration, the auxiliary power source 502 is shown to include two such PV modules 504, 506. However, use of the auxiliary power source 502 having one or more than two such PV modules is also envisioned within the purview of the present specification. Moreover, each of the PV modules 504, 506 may be coupled to the DC-link 110 via a respective DC-DC converter 508, 510. For example, the PV module 504 is connected to the DC-link 110 via the DC-DC converter 508 and the PV module 506 is connected to the DC-link 110 via the DC-DC converter 510. The DC-DC converters 508, 510 may be operated as a buck converter, a boost converter, or a buck-boost converter.
[0066] Furthermore, the power generation system 500 includes a back-up power sub-system 512 that is representative of one embodiment of the back-up power sub-system 116 of FIG. 1. The back-up power sub-system 512 includes certain components that are similar to the components used in the back-up power sub-system 116 of FIG. 1, description of which is not repeated herein. Additionally, one or both of the PV modules 504, 506 are configured to be used as the back-up power source such as the back-up power source 146. By way of a non-limiting example, in the embodiment of FIG. 5, the PV module 504 is configured to be used as the back-up power source.
[0067] To enable such a use of the PV module 504 as the back-up power source, the switches 148 in the back-up power sub-system 512 may additionally include one or more fifth switches 514a, 514b. The fifth switches 514a, 514b may be similar to any of the second switches 154a-c used in the back-up power sub-system 116 of FIG. 1. The fifth switches 514a, 514b are connected between the PV module 504 and the back-up power converter 144, as shown in FIG. 5. Also, the back-up controller 150 is operatively coupled to the fifth switches 514a, 514b to control the switching of the fifth switches 514a, 514b.
[0068] During operation of the power generation system 500, when no fault condition exists, the fifth switches 514a, 514b are operated in OFF states (position shown using dashed lines for reference). However, in the event of the fault condition, the back-up controller 150 is configured to control switching of the fifth switches 514a, 514b to connect the PV module 504 to the back-up power converter 144. In particular, the back-up controller 150 sends control signals to the fifth switches 514a, 514b such that the fifth switches 514a, 514b are operated in the ON states as shown in FIG. 5, thereby connecting the PV module 504 to the back-up power converter 144. In some embodiments, prior to connecting the PV module 504 to the back-up power converter 144 via the fifth switches 514a, 514b, the PV module 504 may be disconnected from the DC-link 110 using similar techniques as described in conjunction with FIG. 4. Moreover, in the event of the fault condition, the back-up controller 150 is configured to control switching of the one or more first switches 152a-c to disconnect the rotor-side converter 106 from the rotor winding 132 and to connect the back-up power converter 144 to the rotor winding 132 in a similar fashion as described in FIG. 1. Therefore, by operating the fifth switches 514a, 514b in the ON state and the first switches 152a-c the second position, electrical connection between the PV module 504 and the rotor winding 132 is established.
[0069] As the PV module 504 is connected to the back-up power converter 144 via the fifth switches 514a, 514b, a DC power from the PV module 504 is supplied to the back-up power converter 144. The back-up power converter 144 is configured to generate the DC excitation power using a DC power received from the PV module 504 which may be supplied to the rotor winding 132. By facilitating supply of the DC excitation power to the rotor winding 132, the DFIG 104 is operated as a synchronous generator to enable the DFIG 104 to generate the electrical power in the event of the fault condition.
[0070] FIG. 6 is a block diagram representation of a power generation system 600, in accordance with one embodiment of the present invention. In the embodiment of FIG. 6 also, the engine 202 is used as a prime mover as shown in FIG. 2. Moreover, the power generation system 600 includes an energy storage device 602 connected to the engine 202. The energy storage device 602 may be generally used to provide a start-up power to crank the engine 202.
[0071] Moreover, the power generation system 600 includes a back-up power sub-system 604 that is representative of one embodiment of the back-up power sub-system 116 of FIG. 1. The back-up power sub-system 604 includes certain components that are similar to the components used in the back-up power sub-system 116 of FIG. 1 description of which is not repeated herein. In particular, in the embodiment of FIG. 6, the energy storage device 602 is configured to be used as the back-up power source such as the back-up power source 146. To enable such a use of the energy storage device 602 as the back-up power source, the switches 148 in the back-up power sub-system 402 may additionally include one or more sixth switches 606a, 606b. The sixth switches 606a, 606b may be similar to any of the second switches 154a-c. The sixth switches 606a, 606b are connected between the energy storage device 602 and the back-up power converter 144, as shown in FIG. 6. Also, the back-up controller 150 is operatively coupled to the sixth switches 606a, 606b to control the switching of the sixth switches 606a, 606b.
[0072] During operation of the power generation system 600, when no fault condition exists, the sixth switches 606a, 606b are operated in OFF states (position shown using dashed lines for reference). However, in the event of the fault condition, the back-up controller 150 is configured to control switching of the sixth switches 606a, 606b to connect the energy storage device 602 to the back-up power converter 144. In particular, the back-up controller 150 sends control signals to the sixth switches 606a, 606b such that the sixth switches 606a, 606b are operated in the ON states as shown in FIG. 6, thereby connecting the energy storage device 602 to the back-up power converter 144. Moreover, in the event of the fault condition, the back-up controller 150 is configured to control switching of the one or more first switches 152a-c to disconnect the rotor-side converter 106 from the rotor winding 132 and to connect the back-up power converter 144 to the rotor winding 132 in a similar fashion as described in FIG. 1. Therefore, by operating the sixth switches 606a, 606b in the ON state and the first switches 152a-c the second position, electrical connection between the energy storage device 602 and the rotor winding 132 is established.
[0073] As the energy storage device 602 is connected to the back-up power converter 144 via the sixth switches 606a, 606b, a DC power from the energy storage device 602 is supplied to the back-up power converter 144. The back-up power converter 144 is configured to generate the DC excitation power using a DC power received from the energy storage device 602 which may be supplied to the rotor winding 132. By facilitating supply of the DC excitation power to the rotor winding 132, the DFIG 104 is operated as a synchronous generator to enable the DFIG 104 to generate the electrical power in the event of the fault condition.
[0074] Referring now to FIG. 7, is flow diagram 700 of a method for operating the power generation system of any of the FIGs. 1-6 is presented, in accordance with one embodiment of the present specification. FIG. 7 is described in conjunction with FIGs. 1-6. At step 702, the method includes, determining if a fault condition exists for one or more of the power electronics unit 105, the primary energy storage device 114, or the power distribution network. In one embodiment, the back-up controller 150 determines the existence of the fault condition using one or more parameters (e.g., voltage, current, phase, etc.) of the electrical signals generated by one or more sensors and predetermined values and/or ranges corresponding to the one or more parameters. In some other embodiments, instead of the back-up controller 150, the supervisory controller 111 is configured to determine the occurrence of the fault condition. If the fault condition has occurred, the supervisory controller 111 is configured to communicate a fault condition indicating signal to the back-up controller 150. Upon the receipt of fault condition indicating signal from the supervisory controller 111, the back-up controller 150 may determine that there exists the fault condition.
[0075] At step 702 if it is determined that no fault condition exists, the control returns to step 702 and step 702 is executed again. However, at step 702 if it is determined that the fault condition exists, at step 704, the back-up controller 150 is configured to disconnect the rotor-side converter 106 from the rotor winding 132 and connect the back-up power converter 144 to the to the rotor winding132. The rotor-side converter 106 may be disconnected from the rotor winding 132 and the back-up power converter 144 may be connected to the rotor winding132 by operating the first switches 152a-c in the second position.
[0076] Further, at step 706, the back-up power converter 144 may be configured to generate a DC excitation power. The method of generating the DC excitation power includes executing one of sub-process blocks 708, 710, 712, 714, or 716 depending on configuration of power generation system. For example, the sub-process blocks 708, 710, 712, 714, 716 describe the method for generating the DC excitation power in the configurations of the power generation systems 200, 300, 400, 500, 600, respectively.
[0077] In the sub-process block 708, generating the DC excitation power includes receiving, by the back-up power converter 144, a DC power from the back-up energy storage device 206 (see FIG. 2), as indicated by sub-step 718. Further, at step 720, the back-up power converter 144 generates the DC excitation power using the DC power received from the back-up energy storage device 206.
[0078] In the sub-process block 710, generating the DC excitation power includes connecting the primary energy storage device 114 to the back-up power converter 144 by controlling switching of the one or more third switches 304a, 304b (see FIG. 3), as indicated by step 722. Further, at step 724, the back-up power converter 144 receives a DC power from the primary energy storage device 114. Moreover, at step 726, the back-up power converter 144 generates the DC excitation power using the DC power received from the primary energy storage device 114.
[0079] In the sub-process block 712, generating the DC excitation power includes connecting the auxiliary power source 112 to the back-up power converter 144 by controlling switching of the one or more fourth switches 404a, 404b (see FIG. 4), as indicated by step 728. Further, at step 730, the back-up power converter 144 receives a DC power from the auxiliary power source 112. Moreover, at step 732, the back-up power converter 144 generates the DC excitation power using the DC power received from the auxiliary power source 112.
[0080] In the sub-process block 714, generating the DC excitation power includes connecting at least one PV module (e.g., the PV module 504) of the one or more PV modules 504, 506 to the back-up power converter 144 by controlling switching of the one or more fifth switches 514a, 514b (see FIG. 5), as indicated by step 734. Further, at step 736, the back-up power converter 144 receives a DC power from the at least one PV module 504. Moreover, at step 738, the back-up power converter 144 generates the DC excitation power using the DC power received from the at least one PV module 504.
[0081] In the sub-process block 716, generating the DC excitation power includes connecting the energy storage device 602 coupled to the engine 202 to the back-up power converter 144 by controlling switching of the one or more sixth switches 606a, 606b (see FIG. 6), as indicated by step 740. Further, at step 742, the back-up power converter 144 receives a DC power from the energy storage device 602. Moreover, at step 744, the back-up power converter 144 generates the DC excitation power using the DC power received from the energy storage device 602.
[0082] Further, in certain embodiments, at step 746, the method includes performing a check to determine if the fault condition exists for the line-side converter 108. By way of example, a check is performed to determine if the line-side converter 108 has encountered the fault condition such as one or more of the failure, the malfunction, the over-current flow, the thermal overload, or combinations thereof. At step 746, if it is determined that the fault condition exists for the line-side converter 108, at step 748 the line-side converter 108 may be disconnected from the stator winding 130 of the DFIG 104 by controlling switching of the one or more second switches 154a-c of the plurality of switches 148. In particular, to disconnect the line-side converter 108 from the stator winding 130 the back-up controller 150 is configured to operate the second switches 154a-c in the OFF states. If, at step 746, if it is determined that the fault condition does not exist for the line-side converter 108, the control may be returned to step 702.
[0083] Furthermore, in some embodiments, the line-side converter 108 may also be disconnected from a stator winding 130 of the DFIG 104 if there exists a fault condition in the power distribution network and a current supplied via the line-side converter 108 limits the overall current from the power generation system 100 to the PCC 120, causing a failure to clear such fault condition in the power distribution network. In such a scenario, the back-up controller 150 may be configured to disconnect the line-side converter 108 from the stator winding 130 of the DFIG 104 by controlling switching of the one or more second switches 154a-c of the plurality of switches 148. Advantageously, as the line-side converter 108 is disconnected, the line-side converter 108 does not limit current output of the power generation system 100, more particularly, when the DFIG 104 is operated as a synchronous generator due to the DC excitation power supplied at the rotor winding 132.
[0084] Moreover, at step 750, the method includes supplying the DC excitation power to the rotor winding 132 of the DFIG 104 from the back-up power converter 144 to enable the DFIG 104 to generate electrical power in the event of the fault condition. By facilitating supply of the DC excitation power to the rotor winding 132, the DFIG 104 is operated as a synchronous generator to enable the DFIG 104 to generate the electrical power in the event of the fault condition.
[0085] In accordance with some aspects of the present specification, configurations of the power generation systems 100, 200, 300, 400, 500, 600 exhibit certain advantages over the traditional hybrid power generation systems. When any fault associated with one or more of the rotor-side converter 106, the line-side converter 108, the supervisory controller 111, or the primary energy storage device 114 is detected, the back-up controller 150 facilitates continued operation of the power generation system 100. In particular, the back-up controller 150 is configured to supply the DC excitation power to the rotor winding 132 via the back-up power controller 144, thereby operating the DFIG 104 as a synchronous generator. Therefore, even in these fault conditions, the DFIG 104 in the power generation systems 100, 200, 300, 400, 500, 600 is continued to be operated. Consequently, a supply of the electrical power to the electric grid and/or the electrical loads connected to the power generation systems 100, 200, 300, 400, 500, 600 may not be interrupted leading to improved and reliable power generation systems 100, 200, 300, 400, 500, 600.
[0086] Further, due to such continued operation of the power generation systems 100, 200, 300, 400, 500, 600, use of the electrical power generated by the auxiliary power source 112, 502 is increased in comparison to the traditional hybrid power generation systems. Moreover, due the enhanced utilization of the electrical power generated by the auxiliary power source 112, 502, a cost per unit of the electricity produced by the power generation systems 100, 200, 300, 400, 500, 600 is also reduced in comparison to the cost per unit of the electricity produced by the traditional hybrid power generation systems.
[0087] Any of the foregoing steps and/or system elements may be suitably replaced, reordered, or removed, and additional steps and/or system elements may be inserted, depending on the needs of a particular application.
[0088] This written description uses examples to disclose the invention, including the preferred embodiments, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. Aspects from the various embodiments described, as well as other known equivalents for each such aspects, can be mixed and matched by one of ordinary skill in the art to construct additional embodiments and techniques in accordance with principles of this application.