CN111108290A

CN111108290A - Hybrid power generation system and associated method

Info

Publication number: CN111108290A
Application number: CN201880063148.6A
Authority: CN
Inventors: Y.Y.科尔哈特卡; A.K.蒂瓦里; J.L.博伦贝克; R.N.拉朱; R.K.布拉; G.贾尼雷迪
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 2017-07-28
Filing date: 2018-07-18
Publication date: 2020-05-05
Also published as: EP3658769A4; WO2019023023A1; EP3658769A1

Abstract

A hybrid power generation system is presented. The system includes a first power generation subsystem comprising: a prime mover driving a generator including a rotor and a stator; one or more first conversion units coupled to at least one of the rotor and the stator; a first Direct Current (DC) link; and one or more second conversion units coupled to the corresponding one or more first conversion units via the first DC link. The system includes one or more second power generating subsystems coupled to the first power generating subsystem and one or more power converting subunits, the one or more power converting subunits including one or more first bridge circuits coupled to corresponding one or more second bridge circuits via one or more transformers, wherein at least one of the first power generating subsystem and the one or more second power generating subsystems includes one or more power converting subunits.

Description

Hybrid power generation system and associated method

Cross Reference to Related Applications

This application is a continuation-in-the-U.S. patent section entitled "POWER CONVERTER FOR DOUBLY-FED INDUCTION GENERATOR WIND turbine system" filed 2017, month 01, 05, assigned attorney docket No. 314312-1, serial No. 15/399,049, the contents of which are hereby incorporated by reference.

Technical Field

Embodiments of the present disclosure relate generally to the integration of wind power generation subsystems and auxiliary power generation subsystems (using Direct Current (DC) sources), and in particular to the integration of wind power generation subsystems with other power generation subsystems, such as solar power generation subsystems, energy storage device-based power generation subsystems, or both.

Background

The demand for renewable electrical energy continues to increase. In some power generation systems, renewable energy (such as solar and wind) based power generation subsystems are used along with non-renewable energy based power generation subsystems. While renewable energy sources are widely available and environmentally friendly, in some cases such sources are unreliable with respect to power production. Reliability may be increased by using two or more renewable energy based power generation subsystems.

One such hybrid power generation system includes a wind power generation subsystem integrated into any DC source based power generation subsystem. Typically, in a hybrid power generation system, only one circuit element may be grounded. Grounding more than one circuit element of the hybrid power generation system may cause leakage currents to flow in the hybrid power generation system. In such cases, it may be desirable to use a high capacity transformer for isolating different portions of a hybrid power generation system having corresponding grounded circuit elements. The use of high capacity transformers increases the footprint and cost of the hybrid power generation system.

Disclosure of Invention

According to an aspect of the present specification, a hybrid power generation system is presented. The hybrid power generation system includes a first power generation subsystem. The first power generation subsystem includes: a prime mover driving a generator including a rotor and a stator; one or more first conversion units coupled to at least one of the rotor and the stator; a first Direct Current (DC) link; and one or more second conversion units coupled to the corresponding one or more first conversion units via the first DC link. Further, the hybrid power generation system includes one or more second power generation subsystems coupled to the first power generation subsystem. Also, the hybrid power generation system includes one or more power conversion sub-units including one or more first bridge circuits coupled to corresponding one or more second bridge circuits via one or more transformers, wherein at least one of the first power generation sub-system and the one or more second power generation sub-systems includes one or more power conversion sub-units.

According to another aspect of the present description, a power system is presented. The power system includes a power grid. Further, the power system includes a wind-based power generation subsystem coupled to the electrical grid. The wind-based power generation subsystem includes a wind-driven doubly-fed induction generator having a rotor and a stator. Further, the wind-based power generation subsystem includes: one or more first conversion units coupled to the rotor; a first Direct Current (DC) link; and one or more second conversion units coupled to the corresponding one or more first conversion units via the first DC link. Further, the power system includes one or more DC source-based power generation subsystems coupled to the wind-based power generation subsystem. Moreover, the power system includes one or more power conversion sub-units including one or more first bridge circuits coupled to corresponding one or more second bridge circuits via one or more transformers, wherein at least one of the wind-based power generation subsystem and the one or more DC-source based power generation subsystems includes one or more power conversion sub-units.

Drawings

These and other features, aspects, and advantages of the present disclosure 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:

fig. 1 is an overview diagram (diagrammational representation) of a hybrid power generation system in accordance with aspects of the present description;

FIG. 2 is an overview of one embodiment of a hybrid power generation system in accordance with aspects of the present description;

FIG. 3 is an overview of yet another embodiment of a hybrid power generation system in accordance with aspects of the present description;

fig. 4 is an overview of an embodiment of a hybrid power generation system with a modular first conversion unit, in accordance with aspects of the present description; and

fig. 5 is an overview of an embodiment of a hybrid power generation system having a distributed DC source based power generation subsystem, in accordance with aspects of the present description.

Detailed Description

Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terms "first," "second," and the like, as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Furthermore, the terms "a" and "an" do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. The term "or" is intended to be inclusive and mean one, some, or all of the listed items. The use of "including," "comprising," or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms "connected" and "coupled" are not restricted to physical or mechanical connections or couplings, and can include electrical connections or couplings, whether direct or indirect. Furthermore, the terms "circuit" and "line" and "controller" may include a single component or multiple components that are active and/or passive and connected or otherwise coupled together to provide the described functionality.

As will be described in detail below, various embodiments of a hybrid power generation system and methods of hybrid power generation are presented. According to aspects of the present description, a hybrid power generation system includes a first power generation subsystem coupled to a second power generation subsystem. Advantageously, in the hybrid power generating system, the first power generating subsystem and the second power generating subsystem may be selectively electrically isolated to prevent leakage current from flowing in the hybrid power generating system. According to certain aspects of the present description, the coupling of the second power generating subsystem and the first power generating subsystem is accomplished without the use of a common mode filter. It may be noted that the use of a common mode filter typically increases the footprint of the hybrid power generation system.

Turning now to the drawings, FIG. 1 shows an overview 100 of an exemplary hybrid power generation system. The hybrid power generating system 100 includes a first power generating subsystem coupled to a second power generating subsystem. The first power generation subsystem includes a wind-based power generation subsystem 102. Further, the second power generation subsystem includes a DC source based power generation subsystem 104. The DC source based power generation subsystem 104 includes a solar based power generation subsystem, an energy storage based power generation subsystem, or any other energy based power generation subsystem. In one embodiment, the energy storage device based power generation subsystem is a battery pack based power generation subsystem. In one embodiment, any other energy-based power generation subsystem includes a thermal-based power generation subsystem, a hydro-electric-based power generation subsystem, and the like.

In one embodiment, wind-based power generation subsystem 102 includes a generator 106, a first conversion unit 108, and a second conversion unit 110. The first conversion unit 108 is coupled to the second conversion unit 110 via a first DC link 112. The first conversion unit 108 may be referred to as a rotor-side converter, and the second conversion unit 110 may be referred to as a line-side converter. The first conversion unit 108 is an Alternating Current (AC) to DC converter. Further, the second conversion unit 110 is a DC-to-AC converter. In one embodiment, the first conversion unit 108 and the second conversion unit 110 may be bidirectional converters. In one embodiment, each of the first conversion unit 108 and the second conversion unit 110 may be a single-stage converter. In another embodiment, each of the first and

second conversion units

108 and 110 may include a plurality of bridge circuits coupled in parallel.

The generator 106 may be driven by a prime mover. In one embodiment, generator 106 is a doubly fed induction generator. In particular, the doubly-fed induction generator may be a wind-driven doubly-fed induction generator. Generator 106 includes a stator 114 and a rotor 116.

The first conversion unit 108 is coupled to the rotor 116. Further, the stator 114 and the second conversion unit 110 are coupled to the first transformer 118. Further, the stator 114 is coupled to a grid 120 via a first transformer 118. The grid 120 may alternatively be referred to as a power grid. In one embodiment, the first transformer 118 is a star-grounded transformer.

During operation of the hybrid power generating system 100, power generated at the generator 106 by rotating the rotor 116 is provided to the grid 120 via dual paths. The dual paths are referred to as a stator bus 114a and a rotor bus 116 a. Sinusoidal multiphase (e.g., three-phase) AC power is provided to first conversion unit 108 via rotor bus 116 a. In one embodiment, the sinusoidal multiphase AC power may be Low Voltage (LV) AC power. First conversion unit 108 converts the LV AC power provided from rotor bus 116a to DC power and provides the DC power to DC link 112. The DC power provided to the DC link 112 may be LV DC power.

Also, the second conversion unit 110 converts LV DC power on the DC link 112 to Low Voltage (LV) AC power suitable for the grid 120. Moreover, stator 114 is configured to provide MV AC power on stator bus 114a of wind-based power generation subsystem 102. The MV AC power from the second conversion unit 110 is combined with MV AC power from the stator 114 of the generator 106 and multi-phase MV power having a certain frequency (e.g., 50Hz/60Hz) is provided to the grid 120.

Further, DC source-based power generation subsystem 104 is coupled to wind-based power generation subsystem 102 at DC link 112. The DC source based power generation subsystem 104 includes a solar array/battery pack 124, a DC to DC converter 126, and a power conversion subunit 128. It is contemplated that any other energy storage device is used instead of the battery pack 124. It should be noted herein that the terms "solar array" and "battery pack" are used interchangeably with reference numeral 124. As used herein, the term "solar array" refers to a combination of a plurality of photovoltaic modules. In one example, the solar array may be a solar panel. Also, as used herein, the term "battery pack" refers to a combination of a plurality of battery modules or batteries. This specification describes in great detail the DC source based power generation subsystem 104 with the solar array 124.

In one embodiment, solar array 124 is coupled to DC link 112 via a DC-to-DC converter 126 and a power conversion subunit 128. The power conversion subunit 128 includes a first bridge circuit 130 coupled to a second bridge circuit 132 via a second transformer 134. In particular, the first bridge circuit 130 is coupled to a first winding 136 of the second transformer 134, and the second bridge circuit 132 is coupled to a second winding 138 of the second transformer 134. In one embodiment, the first winding 136 is a primary winding and the second winding 138 is a secondary winding. The second transformer 134 is an isolation transformer. The second transformer 134 may be configured to operate as a step-up transformer or a step-down transformer depending on the flow direction of power through the power conversion subunit 128. In one embodiment, the first bridge circuit 130 is a DC-to-AC converter and the second bridge circuit 132 is an AC-to-DC converter. The second bridge circuit 132 is coupled to the DC-to-DC converter 126 via a corresponding DC link 140.

Although both the first bridge circuit 130 and the second bridge circuit 132 include a single converter in the embodiment of fig. 1, the first bridge circuit 130 and the second bridge circuit 132 may include a plurality of converters coupled in series in another embodiment. Also, depending on the type of application, it is contemplated to use a plurality of first and second bridge circuits instead of a single first and

second bridge circuit

130, 132. Further, it is contemplated to use a multi-winding transformer rather than the two-winding transformer 134.

The first conversion unit 108, the second conversion unit 110, the power conversion sub-unit 128, and the DC-to-DC converter 126 include a plurality of switches. In particular, in one embodiment, each of the first and

second conversion units

108 and 110 may include at least one pair of switches of a plurality of switches coupled in series with each other. In one embodiment, the first conversion unit 108, the second conversion unit 110, the power conversion sub-unit 128, and the DC-to-DC converter may be controlled using gate control signals provided to corresponding switches to provide a desired output to the grid 120.

The plurality of switches may include semiconductor switches. In one embodiment, the semiconductor switch includes an insulated gate bipolar transistor, a metal oxide semiconductor field effect transistor, a field effect transistor, an injection enhanced gate transistor, an integrated gate commutated thyristor, or the like. In another embodiment, the semiconductor switches comprise gallium nitride based switches, silicon carbide based switches, gallium arsenide based switches, and the like.

In certain embodiments, the solar array 124 is coupled to the ground terminal 122. In particular, the positive, negative, or mid-point terminal of the solar array 124 may be coupled to the ground terminal 122. In one embodiment, the midpoint terminal has a potential of about half the value of the potential at the positive and negative terminals of the solar array 124. In addition to the solar array 124, the first transformer 118 is coupled to a ground terminal 122.

In some embodiments, a power conversion subunit 128 is disposed between the solar array 124 and the wind-based power generation subsystem 102. The power conversion subunit 128 facilitates isolating the solar array 124 from the wind-based power generation subsystem 102. Thus, although both the solar array 124 and the first transformer 118 are coupled to the ground terminal 122, any leakage current between the solar array 124 and the first transformer 118 is prevented. In one embodiment, since the power conversion subunit 128 helps isolate the solar array 124 from the wind-based power generation subsystem 102, the use of a common mode filter is prevented for minimizing leakage current. Thus, the footprint and cost of the hybrid power generation system 100 is lower than the footprint and cost of a hybrid power generation system using a common-mode filter.

Although only the first transformer 118 is shown coupled to the ground terminal 122 in this embodiment, any circuit elements of the wind-based power generation subsystem 102 may be connected to the ground terminal 122. Further, while the hybrid power generating system 100 of fig. 1 is a three-phase system, it is contemplated to use a hybrid power generating system having any number of phases.

Fig. 2 is an overview 200 of one embodiment of a hybrid power generation system in accordance with aspects of the present description. In particular, the embodiment of fig. 2 represents a hybrid power generation system using a modular second conversion unit. Thus, the hybrid power generating system 200 is shown with one or more second conversion units 202. The hybrid power generation system 200 includes a wind-based power generation subsystem 102 coupled to a DC source-based power generation subsystem 104. Wind-based power generation subsystem 102 includes a generator 106, a first conversion unit 108, and one or more second conversion units 202. The first conversion unit 108 and the one or more second conversion units 202 are coupled to each other via a first DC link 112.

Further, generator 106 includes a stator 114 and a rotor 116. The first conversion unit 108 is coupled to the rotor 116. Stator 114 is coupled to one or more second conversion units 202, and further, stator 114 is coupled to a mesh (not shown in fig. 2).

In one embodiment, three

second conversion units

202a, 202b, 202c correspond to respective single phases. Although the present embodiment represents three phases, it may be noted that the number of phases may vary depending on the type of application. Each of the

second conversion units

202a, 202b, 202c comprises a plurality of power conversion sub-units 128. Each of the plurality of power conversion subunits 128 includes a first bridge circuit 130 coupled to a second bridge circuit 132 via a second transformer 134. In particular, the first bridge circuit 130 is coupled to a first winding 136 of the second transformer 134, and the second bridge circuit 132 is coupled to a second winding 138 of the second transformer 134. In addition, the first bridge circuits 130 of each of the plurality of power conversion sub-units 128 corresponding to each of the

second conversion units

202a, 202b, 202c are coupled to each other and also to the first DC link 112.

Further, each of the

second conversion units

202a, 202b, 202c comprises a plurality of second DC-to-AC converters 203 and a plurality of second DC links 204. In each of the

second conversion units

202a, 202b, 202c, each of the power conversion sub-units 128 is coupled to a corresponding second DC-to-AC converter 203 via a corresponding second DC link 204.

Further, a plurality of second DC-to-AC converters 203 are coupled to each other in a series connection to form an AC phase terminal 206 and a neutral terminal 208 corresponding to each of the

second conversion units

202a, 202b, 202 c. Thus, each of the

second conversion units

202a, 202b, 202c comprises a corresponding AC phase terminal 206. Furthermore, each of the

second conversion units

202a, 202b, 202c comprises a corresponding neutral terminal 208. The AC phase terminal 206 of each of the

second switching units

202a, 202b, 202c is coupled to a corresponding phase of the stator bus 114 a.

The DC source based power generation subsystem 104 includes a DC to DC converter 126, a differential mode filter 210, and a solar array 124. The solar array 124 is coupled to the DC-to-DC converter 126 via a differential mode filter 210. Further, a DC-to-DC converter 126 is coupled to the first DC link 112. Thus, the DC source based power generation subsystem 104 is coupled to the first DC link 112.

Since each of the

second conversion units

202a, 202b, 202c comprises a plurality of power conversion sub-units 128, a portion on the first winding side of the second transformer 134 is galvanically isolated from the second winding side of the second transformer 134. Thus, a first path 212 and a second path 214 of the hybrid power generating system 200 may be defined. Thus, a portion of the hybrid power generating system 200 along the first path 212 is isolated from a portion of the hybrid power generating system 200 along the second path 214.

In one embodiment, the first DC link 112 is a circuit element of the first path 212 and is coupled to the ground terminal 122. Additionally, in one embodiment, a first transformer (not shown in fig. 2), which is a circuit element of second path 214, is coupled to ground terminal 122. Since the first DC link 112 is a circuit element of the first path 212 and the first transformer is a circuit element of the second path 214, the grounded first DC link 112 is galvanically isolated from the grounded first transformer. Accordingly, the leakage current is prevented from flowing in the hybrid power generating system 200 without using the common mode filter.

In another embodiment, the solar array 124 may be coupled to the ground terminal 122 instead of grounding the first DC link 112. In yet another embodiment, the first DC link 112 and the solar array 124 may not be grounded, and thus the hybrid power generation system 200 may be a floating system. In such embodiments, the flow of leakage current may be prevented.

Referring now to fig. 3, an overview 300 of another embodiment of a hybrid power generation system is depicted. The hybrid power generation system 300 includes a wind-based power generation subsystem 102 coupled to a DC source-based power generation subsystem 104 at a first DC link 112. Wind-based power generation subsystem 102 includes a generator 106, a first conversion unit 108, and three second conversion units 202. The first conversion unit 108 is coupled to three second conversion units 202 via a first DC link 112.

Each of the

second conversion units

202a, 202b, 202c comprises a plurality of power conversion sub-units 128. Each of the plurality of power conversion subunits 128 includes a first bridge circuit 130 coupled to a second bridge circuit 132 via a second transformer 134. In each of the

second conversion units

The DC source based power generation subsystem 104 includes a power conversion subunit 128, a DC to DC converter 126, and a solar array 124. The solar array 124 is coupled to the first DC link 112 via a DC-to-DC converter 126 and a power conversion subunit 128. As previously noted, the power conversion subunit 128 includes a first bridge circuit 130 coupled to a second bridge circuit 132 via a second transformer 134.

Since each of the second converting

units

202a, 202b, 202c comprises a power converting subunit 128, a portion on the first winding side of the second transformer 134 is galvanically isolated from the second winding side of the second transformer 134. Similarly, since the DC source based power generation subsystem 104 includes the power conversion subunit 128, a portion on the first winding side of the second transformer 134 is galvanically isolated from the second winding side of the second transformer 134. Due to the isolation of the first winding side and the second winding side of the second transformer 134 of each of the

second conversion units

202a, 202b, 202c and the isolation of the first winding side and the second winding side of the second transformer 134 of the DC source based power generation subsystem 104, a first path 302, a second path 304 and a third path 306 may be defined.

The first path 302 comprises a portion (not shown in fig. 3) from the second winding side of the second transformer 134 towards the grid side of each of the

second conversion units

202a, 202b, 202 c. In particular, the first path 302 includes a plurality of second DC-to-AC converters 203 and the second bridge circuit 132 of each of the

second conversion units

202a, 202b, 202 c. The second path 304 includes the first bridge circuit 130 of the DC source based power generation subsystem 104, the first bridge circuit 130 of each of the

second conversion units

202a, 202b, 202c, the first DC link 112, and the generator 106. The third path 306 includes the second bridge circuit 132, the DC-to-DC converter 126, and the solar array 124 of the DC source-based power generation subsystem 104.

The portion of the hybrid power generation system 300 along the first path 302 is isolated from the portion of the hybrid power generation system 300 along the second path 304 and the portion of the hybrid power generation system 300 along the third path 306. Accordingly, any circuit element in the first path 302 may be grounded along with any circuit element of the second path 304 and the third path 306 to prevent the flow of any leakage current. Thus, the use of a common mode filter may not be required.

In the embodiment of fig. 3, a midpoint of the first DC link 112 is coupled to a ground terminal 122. Additionally, a solar array 124 is coupled to the ground terminal 122. Further, a first transformer (not shown in fig. 3) may be coupled to the ground terminal. The first DC link 112, the solar array 124, and the first transformer are circuit elements corresponding to the first path 302, the second path 304, and the third path 306, respectively. Thus, preventing the flow of any leakage current and the use of a common mode filter prevents leakage current from flowing in the hybrid power generating system 300.

Fig. 4 is an overview 400 of an embodiment of a hybrid power generation system with a modular first conversion unit. Thus, the embodiment of fig. 4 represents a hybrid power generation system 400 having a plurality of first conversion units 108. In particular, fig. 4 shows a part of fig. 3. Moreover, the embodiment of fig. 4 represents an embodiment of a hybrid power generation system having a distributed DC source based power generation subsystem. The hybrid power generation system 400 includes a wind-based power generation subsystem 102 and a plurality of DC source-based power generation subsystems 104.

In one embodiment, wind-based power generation subsystem 102 includes a plurality of first conversion units 108 and second conversion units 202 a. The plurality of first conversion units 108 are coupled to each other and are also coupled to the rotor 116 via a rotor bus 116a corresponding to one of the plurality of AC phases. In particular, each of the plurality of first conversion units 108 is coupled to a rotor (not shown in fig. 4) via an inductor 404. Further, each of the plurality of first conversion units 108 is coupled to the neutral terminal 402.

The second converting unit 202a includes a plurality of power converting sub-units 128 and a plurality of second DC-to-AC converters 203. In one embodiment, each of the first conversion units 108 is also coupled to a corresponding power conversion sub-unit 128 via a corresponding first DC link 112.

Also, the second conversion unit 202a includes a plurality of second DC links 204. Each of the power conversion sub-units 128 is coupled to a corresponding second DC-to-AC converter 203 via a second DC link 204. A plurality of second DC-to-AC converters 203 are coupled to each other in a series connection to form an AC phase terminal 206 and a neutral terminal 208. Thus, the second conversion unit 202a includes an AC phase terminal 206 and a neutral terminal 208.

In the embodiment of fig. 4, each of the DC source based power generation subsystems 104 includes a solar array 124, the solar array 124 coupled to a corresponding first DC link 112 via a corresponding DC-to-DC converter 126, a corresponding differential mode filter 210, and a corresponding common mode filter 406. Thus, multiple power generation strings 408, 410, 412 may be formed. Each of the plurality of power generation strings 408, 410, 412 includes one DC source based power generation subsystem 104, a corresponding first conversion unit 108, a corresponding power conversion subunit 128, and a corresponding second DC-to-AC converter 203.

Each of the solar arrays 124 includes a plurality of photovoltaic modules/cell modules. The various photovoltaic modules/battery modules used in the hybrid power generation system 400 are distributed among the solar arrays/battery banks 124 corresponding to each of the plurality of DC source-based power generation subsystems 104. For example, if there are 100 photovoltaic modules, the solar arrays 124 corresponding to each of the plurality of DC source-based power generation subsystems 104 may each include 25 photovoltaic modules. Thus, the total number of photovoltaic modules is distributed among the plurality of DC source based power generation subsystems 104.

As noted above with respect to the preceding figures, each of the plurality of power conversion subunits 128 includes a first bridge circuit 130 coupled to a second bridge circuit 132 via a second transformer 134. Thus, a portion on the first winding side of the second transformer 134 is galvanically isolated from the second winding side of the second transformer 134. Since the portion on the first winding side of the second transformer 134 is isolated from the second winding side of the second transformer 134, a first path 414 and a second path 416 for each of the power generation strings 408, 410, 412 are defined.

The first path 414 of each of the power generation strings 408, 410, 412 includes the first conversion unit 108, the corresponding first DC link 112, the corresponding DC source-based power generation subsystem 104, and the corresponding first bridge circuit 130. Additionally, the first path 414 includes a generator (not shown in FIG. 4), the rotor bus 116 a. Further, the second path 416 of each of the power generation strings 408, 410, 412 includes the second bridge circuit 132 and the second DC-to-AC converter 203.

A portion of the hybrid power generation system 400 along the first path 414 is isolated from a portion of the hybrid power generation system 400 along the second path 416. Thus, for each of the power generating strings 408, 410, 412, any circuit element in the first path 414 may be grounded together with any circuit element of the second path 416 of the corresponding power generating string without causing a flow of leakage current. Thus, the use of a common mode filter is avoided.

In one embodiment, the neutral terminal 402 is coupled to the ground terminal 122 and the solar array 124 is coupled to the ground terminal 122. Both the neutral terminal 402 and the solar array 124 form circuit elements of the first path 414 and are therefore not isolated from each other. Thus, a common mode filter 406 is used in the DC source based power generation subsystem 104 to isolate the grounded neutral terminal 402 from the grounded solar array 124.

In another embodiment, if the power conversion subunit 128 is used in each of the DC source based power generation subsystems 104, the neutral terminal 402 is galvanically isolated from the solar array 124. In this embodiment, even if both the neutral terminal 402 and the solar array 124 are grounded, the flow of leakage current is prevented. Thus, the use of the common-mode filter 406 in each of the DC source based power generation subsystems 104 is avoided. In yet another embodiment, if the neutral terminal is not grounded and is a floating ground system, the use of the common-mode filter 406 in each of the DC source based power generation subsystems 104 may be avoided.

Moreover, in yet another embodiment, each of the plurality of first conversion units 108 is coupled to both the rotor bus 116a and the neutral terminal 402 via a corresponding inductor. The use of inductors helps prevent current from circulating in the hybrid power generation system 400. In this embodiment, the solar array 124 may be grounded along with the grounded neutral terminal 402 without using a common-mode filter and power conversion subunit (such as power conversion subunit 128) in the corresponding DC source-based power generation subsystem 104. Further, in one embodiment, the inductance value of the inductor may be varied based on the operation mode of the first conversion unit 108. The operation mode of the first conversion unit 108 may include an interleaving operation mode or a non-interleaving operation mode. As used herein, the term "interleaved mode of operation" refers to a mode of operation in which the carrier signals for each of the first conversion units have the same frequency and amplitude but the carrier signals are phase shifted with respect to each other over the carrier signal period. In one example, the carrier signals of one first conversion unit may be spaced apart by 360/n degrees relative to the carrier signals of another first conversion unit, where n is the number of first conversion units.

Fig. 5 is a diagrammatic view 500 of an embodiment of a hybrid power generation system with a distributed DC source based power generation subsystem. In particular, the hybrid power generation system 500 includes one or more DC source-based power generation subsystems coupled to corresponding DC links of one or more second conversion units. More particularly, fig. 5 is another embodiment of the hybrid power generating system 400 of fig. 4.

The hybrid power generation system 500 includes a wind-based power generation subsystem 102 and a plurality of DC source-based power generation subsystems 104. In one embodiment, wind-based power generation subsystem 102 includes a plurality of first conversion units 108 and second conversion units 202 a. The second converting unit 202a includes a plurality of power converting sub-units 128 and a plurality of second DC-to-AC converters 203. Each of the first conversion units 108 is coupled to a corresponding power conversion sub-unit 128 of the second conversion unit 202a via a corresponding first DC link 112. Each of the plurality of power conversion sub-units 128 is coupled to a corresponding second DC-to-AC converter 203 via a second DC link 204.

Further, each of the DC source-based power generation subsystems 104 includes a solar array 124 coupled to a corresponding second DC link 204 via a corresponding DC-to-DC converter 126 and a corresponding power conversion subunit 128. As each of the DC source-based power generation subsystems 104 is coupled to a corresponding second DC link 204, a plurality of power generation strings 502, 504, 506 may be formed. In one embodiment, each of the plurality of power generation strings 502, 504, 506 may include a DC source based power generation subsystem 104, a corresponding first conversion unit 108, a corresponding power conversion sub-unit 128 of the second conversion unit 202a, and a corresponding second DC-to-AC converter 203 of the second conversion unit 202 a.

As noted above with respect to the preceding figures, each of the plurality of power conversion subunits 128 includes a first bridge circuit 130 coupled to a second bridge circuit 132 via a second transformer 134. Due to the use of the power conversion subunit 128, a portion on the first winding side of the second transformer 134 is galvanically isolated from the second winding side of the second transformer 134. Accordingly, a first path 508, a second path 510, and a third path 512 of the hybrid power generation system 500 may be defined. The first, second, and

third paths

508, 510, 512 are isolated from one another.

The first path 508 of each of the plurality of power generation strings 502, 504, 506 includes one first conversion unit 108, a corresponding first DC link 112, and a corresponding first bridge circuit 130 of the second conversion unit 202 a. The second path 510 of each of the plurality of power generation strings 502, 504, 506 comprises the second bridge circuit 132 of the second conversion unit 202a, the corresponding second DC-to-AC converter 203, and the corresponding second bridge circuit 132 of the DC source-based power generation subsystem 104. The third path 512 of each of the plurality of power generation strings 502, 504, 506 includes one solar array 124, a corresponding DC-to-DC converter 126, and a corresponding first bridge circuit 130 of the DC source-based power generation subsystem 104.

For each of the power generation strings 502, 504, 506, a portion of the hybrid power generation system 500 along the first path 508 is isolated from a portion of the hybrid power generation system 500 along the second path 510 and the third path 512. Thus, for each of the power generation strings 502, 504, 506, any circuit element in the first path 508 may be grounded along with any other circuit element of the second and

third paths

510, 512 of the corresponding power generation string without the use of a common mode filter.

In one embodiment, the neutral terminal 402 is coupled to the ground terminal 122, and the solar array 124 is also coupled to the ground terminal 122. The neutral terminal 402 is a circuit element of the first path 508 and the solar array 124 is a circuit element of the third path 512 and is isolated from each other to prevent leakage current from flowing in the hybrid power generating system 500. Thus, in the hybrid power generation system 500 and in particular in the DC source based power generation subsystem 104, there is no need to use a common mode filter. Although the examples of fig. 4 and 5 represent a single-phase hybrid power generation system, the number of phases of the hybrid power generation system may vary based on the type of application.

Advantageously, the use of the power conversion subunit 128 helps to isolate the two parts of the hybrid power generation system in accordance with aspects of the present description. For example, a DC source based power generation subsystem is isolated from a wind based power generation subsystem. Also, the use of the power conversion subunit 128 helps prevent leakage current from flowing in the hybrid power generating system. Thus, in an embodiment, the use of a common mode filter is avoided. Any power generation system that does not use a common-mode filter has a better footprint, higher reliability, and cost savings when compared to a hybrid power generation system that uses a common-mode filter. Moreover, the presence of multiple DC links in a hybrid power generation system facilitates the distribution of energy sources (such as photovoltaic modules and battery modules). The distribution of energy sources in a hybrid power generation system facilitates enhanced maximum power point tracking in the case of photovoltaic modules and state of charge management in the case of battery modules.

The hybrid power generation system of the present disclosure may find application in wind-solar hybrid power generation systems and any other system that uses a wind-based power generation subsystem. Moreover, the wind-based power generation subsystem may be a doubly-fed induction generator-based or a full-power conversion-based wind turbine.

While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof.

Claims

1. A hybrid power generation system, the hybrid power generation system comprising:

a first power generation subsystem, the first power generation subsystem comprising:

a prime mover driving a generator including a rotor and a stator;

one or more first conversion units coupled to at least one of the rotor and the stator;

a first Direct Current (DC) link;

one or more second conversion units coupled to corresponding one or more first conversion units via the first DC link;

one or more second power generating subsystems coupled to the first power generating subsystem; and

one or more power conversion subunits comprising one or more first bridge circuits coupled to corresponding one or more second bridge circuits via one or more transformers, wherein at least one of the first power generation subsystem and the one or more second power generation subsystems comprises the one or more power conversion subunits.

2. The hybrid power generating system of claim 1, wherein the first power generating subsystem comprises a wind-based power generating subsystem.

3. The hybrid power generation system of claim 2, wherein the one or more second power generation subsystems comprise one or more DC source-based power generation subsystems.

4. The hybrid power generating system of claim 3, wherein the one or more DC source-based power generating subsystems are coupled to a ground terminal.

5. The hybrid power generating system of claim 4, wherein the wind-based power generating subsystem is coupled to the ground terminal.

6. The hybrid power generation system of claim 5, wherein the one or more power conversion subunits are configured to galvanically isolate the one or more DC source-based power generation subsystems from the wind-based power generation subsystem.

7. The hybrid power generation system of claim 3, wherein the DC source-based power generation subsystem comprises at least one of one or more photovoltaic panels, one or more energy storage devices, and one or more other energy sources.

8. The hybrid power generation system of claim 1, wherein the generator comprises a wind driven doubly fed induction generator.

9. The hybrid power generation system of claim 1, wherein the one or more first bridge circuits comprise a first DC-to-Alternating Current (AC) converter and the one or more second bridge circuits comprise a first AC-to-DC converter.

10. The hybrid power generating system of claim 9, wherein each of the one or more second conversion units further comprises one or more second DC-to-AC converters coupled to each other in a series connection.

11. The hybrid power generating system of claim 10, wherein one of the one or more second DC-to-AC converters corresponding to each of the one or more second converting units comprises a single AC phase terminal.

12. The hybrid power generating system of claim 10, wherein another second DC-to-AC converter of the one or more second DC-to-AC converters corresponding to each of the one or more second converting units comprises a neutral terminal.

13. The hybrid power generating system of claim 10, wherein each of the one or more second DC-to-AC converters is coupled to a corresponding one or more power conversion sub-units via a second DC link.

14. The hybrid power generating system of claim 13, wherein the one or more second power generating subsystems are coupled to the second DC link.

15. The hybrid power generating system of claim 9, wherein the one or more power conversion sub-units and the one or more second conversion units corresponding to the one or more second power generating subsystems are coupled to the first DC link.

16. The hybrid power generating system of claim 9, wherein each of the one or more first conversion units comprises one or more second AC-to-DC converters.

17. The hybrid power generating system of claim 16, wherein the one or more second AC-to-DC converters correspond to one or more alternating current phases.

18. The hybrid power generating system of claim 17, wherein the one or more second converting units are coupled to each other, and wherein each of the one or more second converting units corresponds to at least one of the one or more alternating current phases.

19. The hybrid power generating system of claim 1, wherein each of the one or more first converting units, the one or more second converting units, and the one or more second power generating subsystems comprises one or more silicon carbide (SiC) switches.

20. The hybrid power generation system of claim 1, wherein the one or more second power generation subsystems comprise a DC-to-DC converter.

21. A power system, the power system comprising:

a power grid;

a wind-based power generation subsystem coupled to the electrical grid, wherein the wind-based power generation subsystem comprises:

a wind driven doubly fed induction generator comprising a rotor and a stator;

one or more first conversion units coupled to the rotor;

a first Direct Current (DC) link;

one or more DC source-based power generation subsystems coupled to the wind-based power generation subsystem; and

one or more power conversion subunits comprising one or more first bridge circuits coupled to a corresponding one or more second bridge circuits via one or more transformers, wherein at least one of the wind-based power generation subsystem and the one or more DC source-based power generation subsystems comprises the one or more power conversion subunits.