阅读说明：本技术 用于为功率转换器生成高频开关信号的系统和方法 (System and method for generating high frequency switching signals for power converters ) 是由 K·贾 O·雷 于 2019-08-21 设计创作，主要内容包括：一种控制装置(110)包括第一复用单元(202),其被配置成：将具有第一开关频率的第一PWM信号分离成具有第二开关频率的第二PWM信号和具有第三开关频率的第三PWM信号。此外,控制装置(110)包括积分器单元(204),其被配置成：基于第二PWM信号和第三PWM信号来生成第一积分信号和第二积分信号；以及调制器单元(206),其被配置成：接收第一积分信号和第二积分信号,并且基于第一积分信号和第二积分信号来生成调制信号。此外,控制装置(110)包括生成器单元(208),其被配置成：接收调制信号,并且基于所述调制信号来生成具有不同于第一开关频率的第四开关频率的第四PWM信号。(A control device (110) comprises a first multiplexing unit (202) configured to: the first PWM signal having the first switching frequency is separated into a second PWM signal having the second switching frequency and a third PWM signal having the third switching frequency. Furthermore, the control device (110) comprises an integrator unit (204) configured to: generating a first integrated signal and a second integrated signal based on the second PWM signal and the third PWM signal; and a modulator unit (206) configured to: a first integrated signal and a second integrated signal are received and a modulation signal is generated based on the first integrated signal and the second integrated signal. Furthermore, the control device (110) comprises a generator unit (208) configured to: a modulation signal is received and a fourth PWM signal having a fourth switching frequency different from the first switching frequency is generated based on the modulation signal.)

1. A control device (110) comprising:

a first multiplexing unit (202) configured to: receiving a first Pulse Width Modulation (PWM) signal having a first switching frequency and separating the first PWM signal into a second PWM signal having a second switching frequency and a third PWM signal having a third switching frequency, wherein the second and third switching frequencies are less than the first switching frequency;

an integrator unit (204) coupled to the first multiplexing unit (202) and configured to: receiving the second and third PWM signals and generating first and second integrated signals based on the second and third PWM signals;

a modulator unit (206) coupled to the integrator unit (204) and configured to: receiving the first and second integrated signals and generating a modulation signal based on the first and second integrated signals; and

a generator unit (208) coupled to the modulator unit (206) and configured to: the modulation signal is received and a fourth PWM signal having a fourth switching frequency different from the first switching frequency is generated based on the modulation signal.

2. The control device (110) of claim 1, further comprising a controller (210), the controller (210) configured to receive the first PWM signal having the first switching frequency and to generate a first selector signal, a first reset signal, and a second reset signal based on the first PWM signal.

3. The control device (110) according to claim 2, wherein the first multiplexing unit (202) is coupled to the controller (210) and configured to:

receiving the first selector signal and the first PWM signal having the first switching frequency from the controller (210); and

separating the first PWM signal into the second PWM signal and the third PWM signal based on the first selector signal.

4. The control device (110) according to claim 3, wherein the integrator unit (204) comprises a first integrator (228), the first integrator (228) being configured to receive the second PWM signal having the second switching frequency and to integrate the second PWM signal during a predefined time period to generate the first integrated signal.

5. The control device (110) according to claim 4, wherein the integrator unit (204) further comprises a second integrator (230), the second integrator (230) being configured to receive the third PWM signal having the third switching frequency and to integrate the third PWM signal during the predefined time period to generate the second integrated signal.

6. The control device (110) according to claim 5, wherein the modulator unit (206) comprises a logic circuit (234), the logic circuit (234) being coupled to the controller (210) and configured to:

receive the first reset signal and the second reset signal from the controller (210); and

generating a second selector signal based on the first reset signal and the second reset signal.

7. The control device (110) according to claim 6, wherein the modulator unit (206) further comprises a second multiplexing unit (236), the second multiplexing unit (236) being configured to:

receiving the second selector signal from the logic circuit (234);

-receive the first and second integrated signals from the integrator unit (204); and

combining peak amplitudes of the first and second integrated signals based on the second selector signal to generate the modulated signal.

8. The control device (110) according to claim 7, wherein the generator unit (208) is configured to modulate a triangular carrier based on the modulation signal to generate the fourth PWM signal having the fourth switching frequency.

9. The control device (110) according to claim 8, wherein the fourth switching frequency is larger than the first switching frequency if the frequency of the triangular carrier is larger than the first switching frequency.

10. The control device (110) according to claim 8, wherein the fourth switching frequency is smaller than the first switching frequency if the frequency of the triangular carrier is smaller than the first switching frequency.

11. The control device (110) according to claim 8, wherein the generator unit (208) is configured to transmit the fourth PWM signal having the fourth switching frequency to a power converter (106) for converting a first voltage signal into a second voltage signal.

12. A method, comprising:

receiving, by a first multiplexing unit (202), a first Pulse Width Modulation (PWM) signal having a first switching frequency;

separating, by the first multiplexing unit (202), the first PWM signal into a second PWM signal having a second switching frequency and a third PWM signal having a third switching frequency, wherein the second and third switching frequencies are smaller than the first switching frequency;

generating, by an integrator unit (204), a first integrated signal and a second integrated signal based on the second PWM signal and the third PWM signal;

generating, by a modulator unit (206), a modulation signal based on the first integrated signal and the second integrated signal; and

generating, by a generator unit (208), a fourth PWM signal having a fourth switching frequency based on the modulation signal, wherein the fourth switching frequency is different from the first switching frequency.

13. The method of claim 12, further comprising:

receiving, by a controller (210), the first PWM signal having the first switching frequency; and

generating, by the controller (210), a first selector signal, a first reset signal, and a second reset signal based on the first PWM signal.

14. The method of claim 13, wherein separating the first PWM signal comprises: separating the first PWM signal into the second PWM signal and the third PWM signal based on the first selector signal received from the controller (210).

15. The method of claim 14, wherein generating the first and second integrated signals comprises:

integrating, by a first integrator (228) of the integrator unit (204), the second PWM signal during a predefined time period to generate the first integrated signal; and

integrating, by a second integrator (230) of the integrator unit (204), the third PWM signal during the predefined time period to generate the second integrated signal.

16. The method of claim 15, wherein generating the modulation signal comprises:

receiving, by a logic circuit (234) of the modulation unit (206), the first reset signal and the second reset signal from the controller (210);

generating, by the logic circuit (234), a second selector signal based on the first reset signal and the second reset signal; and

receiving, by a second multiplexing unit (236) of the modulator unit (206), the first integrated signal and the second integrated signal from the logic circuit (234); and

combining, by the second multiplexing unit (236), a peak amplitude of the first integrated signal and a peak amplitude of the second integrated signal based on the second selector signal to generate the modulated signal.

17. The method of claim 16, wherein generating the fourth PWM signal comprises:

receiving, by the generator unit (208), the modulated signal from the second multiplexing unit (236); and

modulating, by the generator unit (208), a triangular carrier based on the modulation signal to generate the fourth PWM signal having the fourth switching frequency.

18. The method of claim 17, wherein the fourth switching frequency is greater than the first switching frequency if the frequency of the triangular carrier is greater than the first switching frequency.

19. The method of claim 17, wherein the fourth switching frequency is less than the first switching frequency if the frequency of the triangular carrier is less than the first switching frequency.

20. The method of claim 12, further comprising:

providing, by a doubly-fed induction generator (DFIG) (102) coupled to a wind turbine (120), a first voltage signal to a power converter (106); and

transmitting, by the generator unit (208), the fourth PWM signal having the fourth switching frequency to the power converter (106) for converting the first voltage signal into a second voltage signal.

21. An electrical power generation system (100), comprising:

a power converter (106) configured to receive a first voltage signal; and

a control device (110) coupled to the power converter (106), wherein the control device (110) comprises:

a first multiplexing unit (202) configured to: receiving a first Pulse Width Modulation (PWM) signal having a first switching frequency and separating the first PWM signal into a second PWM signal having a second switching frequency and a third PWM signal having a third switching frequency, wherein the second and third switching frequencies are less than the first switching frequency;

an integrator unit (204) coupled to the first multiplexing unit (202) and configured to: receiving the second and third PWM signals and generating first and second integrated signals based on the second and third PWM signals;

a modulator unit (206) coupled to the integrator unit (204) and configured to: receiving the first and second integrated signals and generating a modulation signal based on the first and second integrated signals; and

a generator unit (208) coupled to the modulator unit (206) and configured to: the modulation signal is received and a fourth PWM signal having a fourth switching frequency different from the first switching frequency is generated based on the modulation signal.

22. The power generation system (100) of claim 21, further comprising:

a wind turbine (120); and

a doubly-fed induction generator (DFIG) (102) operably coupled to the wind turbine (120) and configured to provide the first voltage signal to the power converter (106).

23. The power generation system (100) of claim 21, wherein the generator unit (208) is configured to: transmitting the fourth PWM signal having the fourth switching frequency to the power converter (106) to convert the first voltage signal to a second voltage signal.

Technical Field

One or more embodiments of the present description relate to power converters, and more particularly, to systems and methods for generating high frequency switching (switching) signals for power converters.

Background

Generally, a power generation system includes a generator (power generator), a power conversion unit coupled to the generator, and a three-winding converter coupled to the power conversion unit and a stator of the generator. The power conversion unit includes a rotor-side converter and a line-side converter connected back-to-back via a Direct Current (DC) link. The main function of the power conversion unit is to regulate the active and reactive power received from the rotor of the generator. Furthermore, the three-winding converter is configured to combine power received from the power conversion unit with power received from the stator and to provide the combined power to the grid.

Typically, three-winding converters are bulky (bulk) and take up more space in the power generation system. Bulky converters may in turn increase the size of the power generation system. Furthermore, it may not be feasible to install such oversized power generation systems at locations with space limitations.

In conventional power generation systems, a PWM generator (generator) is used to provide a switching signal to a line-side converter to convert a DC voltage received from a rotor-side converter to an AC voltage. However, the PWM generator may only provide a low frequency switching signal to the line-side converter, which in turn limits the line-side converter to generate a high voltage equal to the voltage provided by the stator.

Accordingly, there is a need for improved systems and methods for generating and providing high frequency switching signals to power conversion units in order to generate high voltages.

Disclosure of Invention

According to an aspect of the present specification, there is provided a control apparatus. The control device comprises a first multiplexing unit configured to: a method of operating a digital television receiver includes receiving a first Pulse Width Modulation (PWM) signal having a first switching frequency and separating the first PWM signal into a second PWM signal having a second switching frequency and a third PWM signal having a third switching frequency, wherein the second and third switching frequencies are less than the first switching frequency. Furthermore, the control device comprises an integrator unit coupled to the first multiplexing unit and configured to: receiving the second and third PWM signals and generating first and second integrated signals based on the second and third PWM signals. Furthermore, the control device comprises a modulator unit coupled to the integrator unit and configured to: the first and second integrated signals are received and a modulation signal is generated based on the first and second integrated signals. Furthermore, the control device comprises a generator unit coupled to the modulator unit and configured to: the modulation signal is received and a fourth PWM signal having a fourth switching frequency different from the first switching frequency is generated based on the modulation signal.

According to another aspect of the present specification, there is provided a method for varying a switching frequency of a PWM signal. The method comprises the following steps: a first PWM signal having a first switching frequency is received by a first multiplexing unit. Further, the method comprises: separating, by the first multiplexing unit, the first PWM signal into a second PWM signal having a second switching frequency and a third PWM signal having a third switching frequency, wherein the second and third switching frequencies are less than the first switching frequency. Further, the method comprises: generating, by an integrator unit, a first integrated signal and a second integrated signal based on the second PWM signal and the third PWM signal. Further, the method comprises: generating, by a modulator unit, a modulated signal based on the first integrated signal and the second integrated signal. Further, the method comprises: generating, by a generator unit, a fourth PWM signal having a fourth switching frequency based on the modulation signal, wherein the fourth switching frequency is different from the first switching frequency.

In accordance with yet another aspect of the present description, a power generation system is provided. The power generation system includes a power converter configured to receive a first voltage signal. Furthermore, the power generation system comprises a control device coupled to the power converter, wherein the control device comprises a first multiplexing unit configured to: receiving a first Pulse Width Modulation (PWM) signal having a first switching frequency and separating the first PWM signal into a second PWM signal having a second switching frequency and a third PWM signal having a third switching frequency, wherein the second and third switching frequencies are less than the first switching frequency. Furthermore, the control device comprises an integrator unit coupled to the first multiplexing unit and configured to: receiving the second and third PWM signals and generating first and second integrated signals based on the second and third PWM signals. Furthermore, the control device comprises a modulator unit coupled to the integrator unit and configured to: the first and second integrated signals are received and a modulation signal is generated based on the first and second integrated signals. Furthermore, the control device comprises a generator unit coupled to the modulator unit and configured to: the modulation signal is received and a fourth PWM signal having a fourth switching frequency different from the first switching frequency is generated based on the modulation signal.

Drawings

These and other features, aspects, and advantages of the present invention 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 a block diagram of a power generation system according to aspects of the present description;

FIG. 2 is a block diagram of a control device used in the power generation system of FIG. 1 in accordance with aspects of the present description;

FIG. 3 is a graphical representation of a Pulse Width Modulation (PWM) signal generated at the control device of FIG. 2 in accordance with aspects of the present description; and

fig. 4 is a schematic diagram of a power generation system in accordance with aspects of the present description.

Detailed Description

As will be described in detail below, various embodiments of systems and methods for generating high frequency switching signals are provided. The system disclosed herein comprises a control device capable of operating a power converter, e.g. a line-side converter, of a power generation system at a higher switching frequency in order to generate a high voltage at an output of the power converter. This operation enables the power link of the power converter to be directly coupled to the stator side power link, thereby eliminating the need for a three-winding converter in the power generation system. By eliminating the need for a three-winding converter, the size and cost of the power generation system can be significantly reduced. Such a power generation system can be easily installed at a location having space restrictions.

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. Also, 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 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 may include direct or indirect electrical connections or couplings. Further, the terms "circuit" and "circuitry" and "controller" may include a single component or multiple components that are active and/or passive and are connected or otherwise coupled together to provide the described functionality.

Turning now to the drawings and referring to FIG. 1, a block diagram of a power generation system 100 is depicted in accordance with aspects of the present specification. The power generation system 100 includes a generator 102 and a power conversion subsystem 109 coupled to the generator 102. In the illustrated embodiment, the generator 102 is a doubly-fed induction generator (DFIG) 102. It may be noted that the terms "generator" and "DFIG" may be used interchangeably herein.

As depicted in fig. 1, the DFIG 102 includes a stator 101 and a rotor 103 magnetically or inductively coupled to each other. The stator 101 has output terminals and is configured to provide a high Alternating Current (AC) voltage at the output terminals. In one example, the high AC voltage may be in a range from about 1kV to about 15 kV. Similarly, the rotor 103 has output terminals and is configured to provide a low AC voltage at the output terminals. In one example, the low AC voltage may range from about 300V to about 800V. It may be noted that DFIG 102 may be used in one or more applications, for example, for a wind turbine to generate electrical power. In one example, the generated electrical power may be in a range from about 1 MW to about 5 MW. For ease of illustration, DFIG 102 may be operably coupled to wind turbine 120 via gear subsystem 122, as depicted in FIG. 1. In one embodiment, the wind turbine 120 and the gear subsystem 122 may be part of a power generation system 100, which may be referred to as a wind turbine system.

In one embodiment, wind turbine 120 includes a tower 124 and a plurality of blades 126. Furthermore, wind turbine 120 is configured to convert wind energy into mechanical or rotational energy. For example, the kinetic energy of the wind 128 passing through the blades 126 of the wind turbine 120 is converted into mechanical energy. This converted mechanical energy is used to rotate a shaft coupled between the gear wheel system 122 and the DFIG 102 to generate electrical energy or power through the DFIG 102.

Further, power conversion subsystem 109 includes rotor-side conversion unit 104 and line-side conversion unit 106 connected back-to-back via Direct Current (DC) link 108. Each of rotor-side conversion unit 104 and line-side conversion unit 106 includes an AC-DC converter, a DC-AC converter, a DC-DC converter, or a combination thereof. It may be noted that the line-side conversion unit 106 may comprise one or more power converters. In one embodiment, the DC link 108 includes at least one capacitor. Rotor-side conversion unit 104 is coupled to an output terminal of rotor 103 of DFIG 102. The rotor-side conversion unit 104 receives the low AC voltage from the stator 101 and converts the low AC voltage into a low DC voltage. In one example, the low DC voltage may be in a range from about 300V to about 1 kV. Furthermore, line-side conversion unit 106 is coupled to DC link 108 to receive the low DC voltage from rotor-side conversion unit 104 and convert the low AC voltage to a high AC voltage. In one example, the high AC voltage may be in a range from about 1kV to about 20 kV.

Further, each of the rotor-side conversion unit 104 and the line-side conversion unit 106 includes a plurality of semiconductor switches (not shown). In one example, the semiconductor switch includes a gallium nitride switch, a silicon carbide switch, a gallium arsenide switch, a silicon switch, or the like. The semiconductor switches are operated at a desired frequency to generate corresponding voltages at the output terminals of each of the rotor-side conversion unit 104 and the line-side conversion unit 106. In particular, each of the semiconductor switches is activated or deactivated by a switching signal applied to a terminal of the corresponding switch. The switching signal may be referred to as a Pulse Width Modulation (PWM) signal having a plurality of switching pulses. It may be noted that the terms "switching signal" and "PWM signal" may be used interchangeably herein.

In conventional power generation systems, a signal generator, such as a PWM generator, is used to provide switching signals to switches in a line-side converter to convert DC voltage received from a rotor-side converter to AC voltage. However, the PWM generator can only generate low frequency switching signals, which in turn limits the line side converter from generating a high voltage equal to the voltage provided by the stator. Therefore, a three-winding inverter is required to combine the low AC voltage received from the line-side converter with the high AC voltage received from the stator, resulting in an increase in the size and cost of the conventional power generation system.

To overcome the above-described disadvantages/problems associated with conventional power generation systems, the exemplary power generation system 100 includes an exemplary control device 110 coupled to the PWM generator 116 and the rotor-side conversion unit 104 and the line-side conversion unit 106. In particular, the control device 110 receives the low frequency switching signal from the PWM generator 116 and converts the low frequency switching signal to a high frequency switching signal. The control device 110 transmits the high frequency switching signal to the line side conversion unit 106, which in turn generates a high AC voltage. In one example, the PWM generator 116 may be a sinusoidal triangular PWM generator. In one example, the low frequency switching signal is in a range from about 100Hz to about 10kHz, and the high frequency switching signal is in a range from about 500kHz to about 10 MHz. It may be noted that the terms "line-side conversion unit" and "power converter" may be used interchangeably herein. Furthermore, it may be noted that the terms "low frequency switching signal" and "first PWM signal having a first switching frequency" may be used interchangeably herein. Similarly, the terms "high frequency switching signal" and "second PWM signal having a second switching frequency" may be used interchangeably herein. The aspect of converting the first PWM signal to the second PWM signal is explained in more detail with reference to fig. 2.

In addition, control device 110 controls the operation of power conversion subsystem 109. In particular, control device 110 controls the switching of the semiconductor switches of rotor-side conversion unit 104 and line-side conversion unit 106 to regulate the real and reactive power received from rotor 103 of DFIG 102.

Furthermore, since the line-side conversion unit 106 is capable of generating a high voltage, the output terminal 107 of the line-side conversion unit 106 is directly coupled to the output terminal 109 of the stator 101, as depicted in fig. 1. The output terminals 107, 109 are coupled to an output device 114 via a two-winding transformer 112. The two-winding transformer 112 is used to transfer the combined voltage of the stator 101 and the line-side conversion unit 106 to an output device 114. In one example, the output device 114 may be a load such as a power consumption device. In another example, the output device 114 may be a power grid representing an interconnected network of power generation stations, high voltage transmission lines, demand centers, and distribution lines for delivering power from suppliers to consumers. In another embodiment, output terminal 109 of stator 101 and output terminal 107 of line-side conversion unit 106, respectively, may be coupled directly to output device 114 without the use of inverter 112. In such an embodiment, the size of the power generation system may be further reduced compared to embodiments of the power generation system 110 having the dual winding converter 112, since the use of the converter 112 is avoided.

Thus, using the example control device 110 and the two-winding converter 112 instead of a conventional three-winding converter facilitates reducing the size and cost of the power generation system 100. Furthermore, the control device 110 is used with the line-side conversion unit 106 having semiconductor switches, contributing to an increase in the efficiency of the power generation system 100.

Fig. 2 is a block diagram of the control device 110 of fig. 1 in accordance with aspects of the present description. The control device 110 comprises a first multiplexing unit 202, an integrator unit 204, a modulator unit 206, a generator unit 208 and a controller 210. The first multiplexing unit 202 is operatively coupled to an integrator unit 204. Furthermore, the integrator unit 204 is operatively coupled to a modulator unit 206, which is in turn coupled to a generator unit 208. The controller 210 is operatively coupled to the first multiplexing unit 202, the integrator unit 204 and the modulator unit 206.

The controller 210 is coupled to the PWM generator 116 (see fig. 1) and is configured to receive a first PWM signal 212 having a first switching frequency. It may be noted that the first PWM signal 212 having the first switching frequency represents a low frequency switching signal. In one example, the first switching frequency may be in a range from about 100Hz to about 10 kHz. The controller 210 generates a first selector signal (S1)214, a first reset signal (R1)216, and a second reset signal (R2)218 based on the first PWM signal 212. In particular, the controller 210 generates a first selector signal (S1)214, a first reset signal (R1)216, and a second reset signal (R2)218 based on the switching frequency and the pulse width duration of the first PWM signal 212. In one embodiment, the controller 210 may include: processors, microcontrollers, microcomputers, Programmable Logic Controllers (PLCs), specification specific integrated circuits, specification specific processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), and Field Programmable Gate Arrays (FPGAs), integrated circuits such as those employed in computers, and/or any other programmable circuits. In one embodiment, the controller 210 may be preprogrammed to generate the first selector signal (S1)214, the first reset signal (R1)216, and the second reset signal (R2)218 based on the first switching frequency of the first PWM signal 212. Further, the controller 210 transmits the first selector signal (S1)214 to the first multiplexing unit 202. In addition, the controller 210 transmits the first reset signal (R1)216 and the second reset signal (R2)218 to the integrator unit 204 and the modulator unit 206, respectively.

In the illustrated embodiment, the first multiplexing unit 202 is also operatively coupled to the PWM generator 116 to receive a first PWM signal 212 having a first switching frequency. Furthermore, the first multiplexing unit 202 is configured to separate the first PWM signal 212 into a second PWM signal 222 having a second switching frequency and a third PWM signal 220 having a third switching frequency. In one example, each of the second switching frequency and the third switching frequency may be half of the first switching frequency. If the first switching frequency is about 200Hz, each of the second and third switching frequencies may be about 100 Hz. As previously described, the first multiplexing unit 202 receives the first selector signal (S1)214 from the controller 210. In one example, the first selector signal (S1)214 may include a plurality of switching pulses having a predetermined duty cycle. It may be noted that the predetermined duty cycle of the first selector signal (S1)214 is used to determine the second switching frequency of the second PWM signal 220 and the third switching frequency of the third PWM signal 222. Further, if the switching pulse of the first selector signal (S1)214 is high or "1", the first multiplexing unit 202 generates the second PWM signal 220. Similarly, if the switching pulse of the first selector signal (S1)214 is low or "0", the first multiplexing unit 202 generates the third PWM signal 222. In one embodiment, the switching pulses of the first PWM signal 212 are filtered based on the first selector signal (S1)214 to generate the second PWM signal 220 and the third PWM signal 222.

Furthermore, the first multiplexing unit 202 transmits the second PWM signal 220 and the third PWM signal 222 to the integrator unit 204. The integrator unit 204 is configured to receive the second PWM signal 220 and the third PWM signal 222 and to generate a first integration signal 224 and a second integration signal 226 based on the second PWM signal 220 and the third PWM signal 222.

The integrator unit 204 comprises a first integrator 228 and a second integrator 230. The first integrator 228 is configured to receive the second PWM signal 220 having the second switching frequency from the first multiplexing unit 202. The first integrator 228 also receives a first reset signal (R1)216 from the controller 210. Further, the first integrator 228 is configured to integrate the second PWM signal 220 during the predefined time period to generate the first integrated signal 224. In one example, the predefined time period is determined based on a first reset signal (R1)216 received from the controller 210. In one example, the first integrator 228 is reset every predefined time period based on the first reset signal (R1) 216. Further, the first integrator 228 may repeatedly integrate the amplitude of the second PWM signal 220 every predefined time period to generate the first integrated signal 224. It may be noted that the predefined time period is selected in such a way that the first integrator 228 integrates the amplitude of the second PWM signal 220 when the amplitude of the second PWM signal 220 is increasing or at a peak value. Further, if the amplitude of the second PWM signal 220 is decreasing, the first integrator 228 maintains the amplitude of the second PWM signal 220 at a peak value until the first integrator 228 is reset to repeat the integration of the amplitude of the second PWM signal 220 for a subsequent predefined period of time.

The second integrator 230 is configured to receive the third PWM signal 222 having the third switching frequency from the first multiplexing unit 202. The second integrator 230 also receives a second reset signal (R2)218 from the controller 210. In one example, the second integrator 230 is reset every predefined time period based on the second reset signal (R2) 218. In one example, the time period is predefined based on a second reset signal (R2)218 received from the controller 210. Further, the second integrator 230 may repeatedly integrate the amplitude of the second PWM signal 222 every predefined time period to generate the second integrated signal 226. It may be noted that the predefined time period is selected in such a way that the second integrator 230 integrates the amplitude of the third PWM signal 222 when the amplitude of the third PWM signal 222 is increasing or at a peak value. Further, if the amplitude of the third PWM signal 222 is decreasing, the second integrator 230 maintains the amplitude of the third PWM signal 222 at a peak value until the second integrator 230 is reset to repeat the integration of the amplitude of the third PWM signal 222 for a subsequent predefined period of time.

The integrator unit 204 transmits a first integrated signal 224 and a second integrated signal 226 to the modulator unit 206. The modulator unit 206 is configured to receive the first integrated signal 224 and the second integrated signal 226 and to generate a modulation signal 232 based on the first integrated signal 224 and the second integrated signal 226. In the illustrated embodiment, the modulator unit 206 includes a logic circuit 234 and a second multiplexing unit 236. The logic circuit 234 is operably coupled to the controller 210 to receive the first reset signal (R1)216 and the second reset signal (R2) 218. Further, the logic circuit 234 is configured to generate the second selector signal (S2)240 based on the first reset signal 216 and the second reset signal 218. In one example, if the first reset signal (R1)216 is received, the logic circuit 234 generates a high switching pulse "1" of the second selector signal (S2) 240. Similarly, if the second reset signal (R2)218 is received, the logic circuit 234 generates a low switching pulse "0" of the second selector signal (S2) 240. It may be noted that the pulse width duration of the switching pulse of the second selector signal (S2)240 is selected 240 in such a way that only the peak amplitudes of the first integrated signal 224 and the second integrated signal 226 are combined.

Further, the second multiplexing unit 236 is operatively coupled to the logic circuit 234 and configured to receive the second selector signal from the logic circuit 234 (S2). The second multiplexing unit 236 is further configured to receive the first integrated signal 224 and the second integrated signal 226 from the integrator unit 204. The second multiplexing unit 236 combines the peak amplitude of the first integrated signal 224 and the peak amplitude of the second integrated signal 226 based on the second selector signal (S2)240 to generate the modulated signal 232. If the second selector signal (S2)240 is having a high switching pulse "1", the second multiplexing unit 236 determines the peak amplitude of the first integrated signal 224. In a similar manner, if the second selector signal (S2)240 is having a low switching pulse "0", the second multiplexing unit 236 determines the peak amplitude of the second integrated signal 226. Further, the second multiplexing unit 236 combines the peak amplitude of the first integrated signal 224 and the peak amplitude of the second integrated signal 226 to generate the modulated signal 232.

Further, the generator unit 208 is coupled to the modulator unit 206 and is configured to receive the modulation signal 232 and to generate a fourth PWM signal 242 having a fourth switching frequency based on the modulation signal 232. The fourth switching frequency is different from the first switching frequency. In one example, the fourth switching frequency is in a range from about 500kHz to about 10 MHz. It may be noted that the fourth switching frequency may be selected based on a voltage generated by the line-side conversion unit 106 (see fig. 1) to match the voltage of the stator 101 (see fig. 1). In one embodiment, the generator unit 208 is configured to modulate the triangular carrier 235 based on the modulation signal 232 to generate a fourth PWM signal 242 having a fourth switching frequency. If the frequency of triangular carrier 235 is greater than the first switching frequency, the fourth switching frequency is greater than the first switching frequency. Similarly, if the frequency of triangular carrier 235 is less than the first switching frequency, then the fourth switching frequency is less than the first switching frequency. In one example, the generator unit 208 comprises a sinusoidal triangular PWM generator. For ease of understanding of the embodiments of the present invention, the fourth switching frequency is considered to be greater than the first switching frequency. It may be noted that the generator unit 208 may comprise any type of generator and is not limited to a sinusoidal triangular PWM generator. Thereafter, the generator unit 208 transmits a fourth PWM signal 242 having a fourth switching frequency to the line-side conversion unit 106 of the power conversion subsystem 109 to convert the low DC voltage to a high AC voltage. It may be noted that the low DC voltage received by the line-side conversion unit 106 may also be referred to as a first voltage signal having a first amplitude. Similarly, the high AC voltage generated by the line-side conversion unit 106 may be referred to as a second voltage signal having a second amplitude. It is noted herein that the second amplitude is greater than the first amplitude.

Thus, by employing the example control apparatus 110, the low frequency switching signal or first PWM signal 212 is converted to a high frequency switching signal or fourth PWM signal 242. Specifically, the high-frequency switching signal 242 operates the line-side conversion unit 106 at a high switching frequency so as to generate the same high voltage as the voltage supplied from the stator 101. Therefore, a bulky three-winding converter is not required.

Fig. 3 depicts a graphical representation of the different PWM signals plotted, wherein the Y-axis 302 represents the amplitude of the different PWM signals and the X-axis 304 represents time. Reference numeral 212 denotes a first PWM signal. Reference numeral 220 denotes a second PWM signal, and reference numeral 222 denotes a third PWM signal. Reference numeral 224 denotes the first integrated signal, and reference numeral 226 denotes the second integrated signal. Reference numeral 232 denotes a modulation signal. Reference numeral 242 denotes a fourth PWM signal having a fourth switching frequency.

Referring to fig. 4, a schematic diagram of a power generation system 400 is depicted in accordance with aspects of the present description. The power generation system 400 includes a DFIG 402 and a power conversion subsystem 404 coupled to the DFIG 402. It may be noted that the DFIG 402 may be similar to the DFIG 102 of FIG. 1. DFIG 402 includes a rotor 403 and a stator 401 magnetically coupled to each other. Further, rotor 403 includes rotor windings configured to provide a low AC voltage to power conversion subsystem 404. In one example, the low AC voltage may be in a range from about 300V to about 800V. Similarly, the stator 401 includes stator windings configured to provide a high AC voltage to an output device 407, such as a grid or load. In one example, the high AC voltage may be in a range from about 1kV to about 20 kV.

In the illustrated embodiment, the power conversion subsystem 404 includes a rotor-side conversion unit 406 and a plurality of line-side conversion units 408, 410, 412. A plurality of line-side conversion units 408, 410, 412 are coupled to rotor-side conversion unit 406 via DC link 409. The rotor-side conversion unit 406 is operatively coupled to the rotor windings of the rotor 403. In one example, the rotor-side conversion unit 406 may be an AC-DC converter configured to convert a low AC voltage received from a rotor winding of the rotor 403 into a DC voltage. In one example, the low DC voltage may be in a range from about 300V to about 1 kV. Furthermore, the line side switching units 408, 410, 412 are operatively coupled to the stator windings of the stator 401. Further, the line-side conversion units 408, 410, 412 and the stator 401 of the DFIG 402 are operatively coupled to the output device 407.

Furthermore, the line side conversion units 408, 410, 412 are coupled to each other in series to form a modular arrangement. In one example, the line-side conversion units 408, 410, 412 are arranged in a stacked configuration. Although only 3 line-side conversion units 408, 410, 412 are shown in the embodiment of fig. 4, in alternative embodiments more than 4 line-side conversion units may be used to boost the output voltage generated by the combination of line-side conversion units.

Each of the line-side conversion units 408, 410, 412 is a modular unit that may be removed or replaced with another modular unit in the power conversion subsystem 404. Advantageously, the use of multiple line-side conversion units 408 and 412 in the power conversion subsystem 404 enables the output voltage of the power conversion subsystem 404 to be increased.

As depicted in FIG. 4, each of the line-side conversion units 408 and 412 includes a plurality of converters 414, 416 and a plurality of inverters 420, 422, 424 operatively coupled to each other. Converter 414 and 416 are coupled in parallel with DC link 409. Each of the converters 414 and 416 may be a DC-DC converter configured to ramp up or increase the DC voltage received from the rotor-side conversion unit 406 via the DC link 409. In addition, each converter 414-416 transmits a ramped or high DC voltage to a corresponding inverter 420-424. In one example, the high DC voltage may be in a range from about 1kV to 20 kV. In addition, the converter 414-416 may be used to isolate the DC voltage associated with the rotor-side conversion unit 406 from the inverter 420-424.

Each of the inverters 420-424 is coupled to a corresponding converter 414-418 and is configured to convert the high DC voltage received from the converter 414-418 to a high AC voltage. The high AC voltage may be equal to the AC voltage provided by the stator windings of the stator 401. In one example, the high AC voltage may be in a range from about 1kV to about 20 kV.

Further, power generation system 400 includes a control device 430, which control device 430 is operatively coupled to power conversion subsystem 404 to control the operation of power conversion subsystem 404. Control device 430 may be similar to control device 110 of fig. 2. In particular, the control device 430 is configured to control the operating frequency or switching frequency of the rotor-side conversion unit 406 and the switches 432 of the line-side conversion unit 408 and 412. More specifically, during operation of the power generation system 400, the control device 430 operates the switches 432 of the rotor-side conversion unit 406 and the line-side conversion unit 408 and 412 between an ON (ON) and an OFF (OFF) state to generate a desired output voltage. The term "active state" or "on state" refers to the condition when the switch is in a conducting state. The term "deactivated state" or "open state" refers to the condition when the switch is in a non-conductive state.

In one embodiment, the control device 430 is configured to synchronize the switching of the switches 432 of the converters 414 and 418 of one line side conversion unit 408 with the switching of the corresponding switches 432 of the converters 414 and 418 of the other line side unit 410. Furthermore, the control device 430 is configured to synchronize the switches of the switches 432 of the inverters 420-424 of one line-side conversion unit 408 with the switches of the corresponding switches 432 of the inverters 420-424 of the other line-side conversion unit 410.

Furthermore, the exemplary control device 430 is configured to operate the switches 432 of the line-side conversion unit 408 and 412 to boost (step-up) or increase the voltage provided by the rotor windings of the rotor 403. Specifically, the control device 430 is operatively coupled to the PWM generator 440 and is configured to receive the first PWM signal 436 having the first switching frequency from the PWM generator 440. Furthermore, the control device 430 is configured to convert the first PWM signal 436 having the first switching frequency into the second PWM signal 438 having a second switching frequency different from the first switching frequency. Furthermore, the control device 430 is configured to transmit a second PWM signal 438 having a second switching frequency to the switch 432 of the line-side conversion unit 408 and 412 to operate the switch 432 at the second switching frequency. By operating the switches at the second switching frequency, the low DC voltage received from the rotor-side conversion unit 406 is converted into a high AC voltage equal to the voltage generated by the stator 401. The high AC voltage is combined with the voltage supplied by the stator 401 and the combined voltage is thereafter supplied to the output device 407. In one embodiment, the control device 430 may also send a second PWM signal 438 having a second switching frequency to the rotor-side conversion unit 406 to convert and increase the low AC voltage received from the rotor windings of the rotor 403 to a DC voltage. In addition, the rotor-side conversion unit 406 provides a corresponding increased DC voltage to the line-side conversion unit 408 and 412.

Thus, by employing the exemplary control apparatus, the low frequency switching signal or the first PWM signal is converted to the high frequency switching signal or the fourth PWM signal. The high frequency switching signal may be used to operate the line side conversion unit at a high switching frequency in order to generate the same high voltage as the voltage provided by the stator.

Furthermore, the foregoing examples, descriptions, and process steps, such as those that may be performed by a system, may be implemented by appropriate code on a processor-based system (e.g., a general-purpose computer or a special-purpose computer). It should also be noted that different implementations of the present technology may perform some or all of the steps described herein in different orders or substantially simultaneously (i.e., in parallel). Further, the functionality may be implemented using a variety of programming languages, including but not limited to C + + or Java. Such code may be stored or adapted for storage on one or more tangible machine readable media, such as on a data repository chip, a local or remote hard disk, optical disk (i.e., CD or DVD), memory, or other medium accessible by a processor-based system to execute the stored code. Note that the tangible medium may comprise paper or another suitable medium upon which the instructions are printed. For example, the instructions may be electronically captured via optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner if necessary, and then stored in a data store or memory device.

Various embodiments of systems and methods for generating high frequency switching signals are disclosed. The systems and methods disclosed herein employ an exemplary control arrangement that facilitates operating a power converter at a high switching frequency to generate a high voltage at the output of a line side conversion unit. Such an arrangement facilitates coupling the power link of the line-side conversion unit directly to the stator of the DFIG, thereby eliminating the use of bulky three-winding converters in the power generation system. Such a power generation system can be easily installed at a location having space restrictions.

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.