A brushless double-fed power generation system based on dual frequency conversion structure and its control method

Abstract

The present invention discloses a brushless double-fed power generation system based on a dual-frequency conversion structure and a control method thereof, which belongs to the field of motor power generation. In the brushless double-fed power generation system, a controller on the control winding side uses a load voltage U L , DC bus voltage U dc And the speed signal n of the prime mover r Calculate U c ' and f c '; The power winding side controller will U dc Converted into amplitude and frequency f L 'Constant load voltage U L ' and output; the AC-DC-AC inverter sets the target value of the DC bus voltage and c ' and f c 'The control winding outputs a voltage with a suitable amplitude and frequency to adjust the amplitude and frequency of the output voltage of the power winding; the uncontrolled rectifier module makes the DC bus voltage reach and maintain the target value; the inverter module maintains the output of the fixed amplitude and frequency U L The present invention can realize stable control of DC bus voltage and load voltage, save R&D cost and time, and improve the stability of DC bus voltage and the dynamic response of the system.

Description

Technical Field

[0001] The present invention belongs to the field of motor power generation, and more specifically, relates to a brushless double-fed power generation system based on a dual-frequency conversion structure and a control method thereof. Background Art

[0002] With the development of human society and the improvement of material level, the problem of energy shortage has become increasingly prominent. Therefore, the development and utilization of clean renewable energy and the improvement of energy conversion equipment to improve energy utilization have become research hotspots in recent years. Brushless doubly-fed motors have broad application prospects in variable speed power generation fields such as wind power, hydropower, and ship shaft belts due to their reliable structure and flexible excitation regulation, and have attracted much attention in recent years.

[0003] At present, the brushless doubly-fed power generation system usually has the power winding directly connected to the load or the power grid, and the control winding connected to the bidirectional inverter. The voltage and frequency of the control winding are changed by the inverter to keep the voltage and frequency of the power winding constant, thereby realizing variable speed constant frequency power generation of the motor.

[0004] However, due to the complexity of the mathematical model of the brushless doubly-fed motor and the low accuracy of parameter identification, the existing brushless doubly-fed power generation system still has problems such as poor dynamic response and poor DC bus voltage stability, which can easily cause shutdown and collapse of the entire power generation system; at the same time, the complex control strategy also brings difficulties to the development and debugging of the power generation system, hindering the popularization and promotion of brushless doubly-fed power generation technology. Summary of the invention

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides a brushless doubly-fed power generation system based on a dual frequency conversion structure and a control method thereof, the purpose of which is to use an AC-DC-AC inverter to achieve stable control of the DC bus voltage, thereby solving the technical problems of complex regulation, slow dynamic response, poor DC bus voltage stability, low motor efficiency and poor overload capacity existing in the current brushless doubly-fed motor power generation system.

[0006] To achieve the above object, according to one aspect of the present invention, a brushless doubly-fed power generation system based on a dual frequency conversion structure is provided, comprising:

[0007] A brushless double-fed generator comprises: a rotor structure and a stator structure, wherein the stator structure comprises: an iron core, a power winding and a control winding;

[0008] The control winding side controller is connected to the brushless double-fed generator and is used to utilize the load voltage U L , DC bus voltage U dc And the speed signal n of the prime mover r Calculate the given voltage U c ' and given frequency f c ';

[0009] The power winding side controller is used to convert the DC bus voltage U dc Converted into amplitude and frequency f L 'Constant load voltage U L ' and output;

[0010] The AC-DC-AC inverter is connected to the control winding side controller and the control winding, and is used to establish the DC bus voltage and set its target value, and to generate a DC bus voltage at the given voltage U c ' and the given frequency f c 'Control the control winding to output a voltage of suitable amplitude and frequency, so as to adjust the amplitude and frequency of the output voltage of the power winding;

[0011] an uncontrolled rectifier module, connected to the power winding, and configured to enable the DC bus voltage to reach and maintain the target value when the DC bus voltage is determined by the output voltage of the power winding;

[0012] The inverter module is connected to the uncontrolled rectifier module and the power winding side controller, and is used to maintain the output of a load voltage U with a fixed amplitude and frequency when the DC bus voltage reaches the target value. L , to supply power to the connected loads or to connect to the grid for grid-connected power supply.

[0013] In one embodiment, the brushless doubly-fed power generation system based on the dual frequency conversion structure further includes:

[0014] A speed sensor is connected to the prime mover and the control winding side controller, and is used to collect the speed signal n of the prime mover. r and transmit it to the control winding side controller;

[0015] A voltage sensor is connected to the control winding side controller and the power winding side controller to collect the DC bus voltage U dc and load voltage U L And transmit it to the control winding side controller, and also collect the DC bus voltage U dc Transmitted to the power winding side controller.

[0016] In one of the embodiments, the DC bus of the AC-DC-AC inverter is connected in parallel with the DC bus of the uncontrolled rectifier module, so as to be finally connected to a load or a power grid through the inverter module to realize external power generation.

[0017] In one of the embodiments, the rotor structure includes at least one of a winding, a squirrel cage, and a magnetic resistance.

[0018] In one embodiment, the excitation mode of the brushless doubly-fed power generation system is a DC excitation mode or an AC excitation mode.

[0019] In one of the embodiments, when the excitation mode of the brushless doubly-fed power generation system is a DC excitation mode, the brushless doubly-fed power generation system also includes a battery, and the battery is connected across the DC bus of the AC-DC-AC inverter and the DC bus of the uncontrolled rectifier module; the brushless doubly-fed power generation system is powered by the battery.

[0020] In one embodiment, when the brushless doubly-fed power generation system is excited by an AC excitation method, the power grid is connected to the AC-DC-AC converter via a transformer, and the brushless doubly-fed power generation system is powered by the power grid.

[0021] According to another aspect of the present invention, a control method for a brushless doubly-fed power generation system based on a dual-frequency conversion structure is provided, comprising:

[0022] S1: When receiving the start command, the grid or battery provides initial excitation to enable the AC-DC-AC inverter to establish the DC bus voltage;

[0023] S2: Control winding side controller using load voltage U L , DC bus voltage U dc And the speed signal n of the prime mover r Calculate the given voltage U c ' and given frequency f c ';

[0024] S3: The AC-DC-AC inverter sets the target value of the DC bus voltage and sets the given voltage U c ' and the given frequency f c 'Under the action of the control winding, the control winding outputs a voltage of suitable amplitude and frequency, so as to adjust the amplitude and frequency corresponding to the output voltage of the power winding;

[0025] S4: When the DC bus voltage is determined by the output voltage of the power winding, the rectifier module is not controlled to make the DC bus voltage reach and maintain the target value; the inverter module is controlled to output a load voltage U with a fixed amplitude and frequency. L , to supply power to the connected loads or to connect to the grid for grid-connected power supply.

[0026] In one embodiment, the S4 includes:

[0027] S41: When the DC bus voltage is determined by the output voltage of the power winding, disconnect the grid switch or the battery switch, and close the main circuit breaker or the grid-connected switch; adjust the inverter module and the AC-DC-AC converter so that the inverter module outputs a load voltage U with a fixed amplitude and frequency.L ;

[0028] S42: When the DC bus voltage is not determined by the output voltage of the power winding, repeat S3.

[0029] In one embodiment, the control method before S2 further includes:

[0030] The speed sensor is used to collect the speed signal n of the prime mover. r and transmit it to the control winding side controller;

[0031] Use voltage sensor to collect DC bus voltage U dc and load voltage U L , and transmit it to the control winding side controller, and also collect the DC bus voltage U dc Transmitted to the power winding side controller.

[0032] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0033] 1. The present invention provides a brushless doubly-fed power generation system based on a dual-frequency conversion structure, which realizes the interactive flow of energy by using an AC-DC-AC inverter in parallel with a DC bus, and always keeps the DC bus voltage of the AC-DC-AC inverter stable. The brushless doubly-fed motor is independently controlled by an AC-DC-AC inverter with V / F separation to control the winding voltage and frequency to ensure the output voltage value on the power winding side, and then maintains the DC voltage stability through an uncontrolled rectifier module, and finally realizes the stability of the voltage and frequency at the load end. The power generation system proposed by the present invention has good dynamic response and high robustness, and the hardware can use mature modular products, which has the advantages of strong practicality and short development cycle.

[0034] 2. The brushless doubly-fed power generation system based on the dual-frequency conversion structure and its control method provided by the present invention can realize the stable control of the DC bus voltage and load voltage of the system by using a conventional commercial frequency converter through innovative power electronic topology and control method, eliminating the need for detailed derivation of the motor mathematical model and development of the control algorithm, which can significantly save R&D costs and time, and improve the stability of the DC bus voltage and the dynamic response of the power generation system. At the same time, in the proposed new power generation system, the power winding frequency of the brushless doubly-fed motor does not need to be fixed at a specific frequency. According to the specific working conditions, the frequency can be reduced when overloaded to improve the overload capacity, and the frequency can be increased when lightly loaded to reduce the saturation of the core, thereby effectively improving the performance of the power generation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of a brushless double-fed power generation system based on a dual frequency conversion structure provided by an embodiment of the present invention;

[0036] Figure 2 is a flow chart of a control method for a brushless double-fed power generation system based on a dual frequency conversion structure provided by an embodiment of the present invention;

[0037] Figure 3 It is a flow chart of a control method of a brushless doubly-fed power generation system based on a dual frequency conversion structure provided by another embodiment of the present invention. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0039] The present invention provides a brushless double-fed power generation system based on a dual-frequency conversion structure, such as Figure 1 As shown, it includes: a brushless double-fed generator, a control winding side controller, a power winding side controller, an AC-DC-AC inverter, an uncontrolled rectifier module and an inverter module. The brushless double-fed generator includes: a rotor structure and a stator structure, and the stator structure includes: an iron core, a power winding and a control winding; the control winding side controller is connected to the brushless double-fed generator and is used to utilize the load voltage U L , DC bus voltage U dc And the speed signal n of the prime mover r Calculate the given voltage U c ' and given frequency f c '; Power winding side controller, used to convert the DC bus voltage U dc Converted into amplitude and frequency f L 'Constant load voltage U L ' and output; AC-DC-AC inverter, connected to the control winding side controller and the control winding, used to establish the DC bus voltage and set its target value, and at a given voltage U c ' and given frequency f c 'Under the action of the control winding, the control winding outputs a voltage of suitable amplitude and frequency to adjust the amplitude and frequency of the output voltage of the power winding; the uncontrolled rectifier module is connected to the power winding and is used to make the DC bus voltage reach and maintain the target value when the DC bus voltage is determined by the output voltage of the power winding; the inverter module is connected to the uncontrolled rectifier module and the power winding side controller and is used to maintain the output of the load voltage U with a fixed amplitude and frequency when the DC bus voltage reaches the target value L , to supply power to the connected loads or to connect to the grid for grid-connected power supply.

[0040] Specifically, the brushless double-fed power generation system provided by the present invention includes a brushless double-fed motor, an AC-DC-AC inverter, an uncontrolled rectifier module, an inverter module, a transformer, a speed sensor, a voltage sensor, a current sensor, and other hardware such as a switch, as well as a control winding side controller and a power winding side controller. In one embodiment, the rotor structure includes at least one of a winding, a squirrel cage, and a magnetic resistance.

[0041] Specifically, the brushless doubly-fed generator includes a stator and a rotor structure. The rotor structure is composed of specially designed windings, squirrel cages, magnetic resistance or hybrid structures. The stator structure includes an iron core and two sets of three-phase AC windings with different pole pairs, called power windings and control windings. The power winding is directly connected to the uncontrolled rectifier module to feed power into the DC bus, and the control winding is connected to the grid through an AC-DC-AC inverter.

[0042] In one of the embodiments, the DC bus of the AC-DC-AC inverter is connected in parallel with the DC bus of the uncontrolled rectifier module, so as to be finally connected to the load or the grid through the inverter module to realize external power generation.

[0043] Specifically, the DC bus of the AC-DC-AC inverter is connected in parallel with the DC bus of the uncontrolled rectifier module, and is finally connected to the load or the grid through the inverter module to realize external power generation. L , DC bus voltage U dc And the speed signal n of the speed sensor r , the required control winding given voltage U is obtained by calculation c And given frequency f c The inverter module on the power winding side detects the DC bus voltage U dc , output a fixed frequency f that meets the requirements of the load and power grid L , and maintain the load voltage U L Constant.

[0044] The present invention, through the innovation of power electronic topology and control method, can realize stable control of DC bus voltage and load voltage of the system by using conventional commercial inverters, eliminating the need for detailed derivation of motor mathematical models and development of control algorithms, thereby significantly saving R&D costs and time, and improving the stability of DC bus voltage and the dynamic response of the power generation system.

[0045] In addition, in the brushless doubly-fed power generation system based on the dual frequency conversion structure provided by the present invention, the power winding frequency of the brushless doubly-fed motor does not need to be fixed at a specific frequency. According to the specific working conditions, the frequency can be reduced when overloaded to improve the overload capacity, and the frequency can be increased when lightly loaded to reduce the core saturation degree, thereby effectively improving the performance of the power generation system.

[0046] In one embodiment, the brushless double-fed power generation system based on the dual frequency conversion structure further includes: a speed sensor connected to the prime mover and the control winding side controller for collecting the speed signal n of the prime mover r And transmit it to the control winding side controller; the voltage sensor is connected to the control winding side controller and the power winding side controller to collect the DC bus voltage U dc and load voltage U L And transmit it to the control winding side controller, and also collect the DC bus voltage U dc Transmitted to the power winding side controller.

[0047] In one embodiment, the excitation mode of the brushless double-fed power generation system is a DC excitation mode or an AC excitation mode.

[0048] In one of the embodiments, when the excitation mode of the brushless doubly fed power generation system is a DC excitation mode, the brushless doubly fed power generation system also includes a battery, which is connected across the DC bus of the AC-DC-AC inverter and the DC bus of the uncontrolled rectifier module; the battery is used to power the brushless doubly fed power generation system.

[0049] In one embodiment, when the brushless double-fed power generation system is excited by an AC excitation method, the power grid is connected to the AC-DC-AC converter via a transformer, and the brushless double-fed power generation system is powered by the power grid.

[0050] like Figure 2 As shown, the present invention also provides a control method for a brushless double-fed power generation system based on a dual frequency conversion structure, comprising:

[0051] S1: When receiving the start command, the grid or battery provides initial excitation to enable the AC-DC-AC inverter to establish the DC bus voltage;

[0052] S2: Control winding side controller using load voltage U L , DC bus voltage U dc And the speed signal n of the prime mover r Calculate the given voltage U c ' and given frequency f c ';

[0053] S3: The AC-DC-AC inverter sets the target value of the DC bus voltage and sets the voltage U c ' and given frequency f c 'Under the action of the control winding, the control winding outputs a voltage of suitable amplitude and frequency, so as to adjust the amplitude and frequency corresponding to the output voltage of the power winding;

[0054] S4: When the DC bus voltage is determined by the output voltage of the power winding, the rectifier module is not controlled to make the DC bus voltage reach and maintain the target value; the inverter module is controlled to output a load voltage U with a fixed amplitude and frequency.L , to supply power to the connected loads or to connect to the grid for grid-connected power supply.

[0055] Specifically, first close the independent switch or battery switch to provide initial excitation for the power generation system and establish the DC bus voltage so that the AC-DC-AC inverter can work normally; then, give the DC bus voltage target value U dc * , combined with the signal n measured by the speed sensor r And the signal U measured by the voltage sensor dc , by outputting a suitable control winding voltage amplitude U c , frequency f c , to achieve the brushless double-fed motor power winding voltage U p and frequency f p The DC bus voltage U dc Reach the target value; then, by detecting the size of the grid or battery loop current, determine whether the DC bus voltage is determined by the motor power winding voltage. If not, return to step 2 to continue adjusting the DC bus voltage given value U dc * If yes, go to the next step; then, disconnect the independent switch or battery switch, the power generation system can automatically enter the double-fed self-generated self-excitation mode of the power winding, and feed back to the control winding through the DC bus, without external excitation; then, adjust the inverter module to achieve a fixed output voltage amplitude U L and frequency f L ; Then, close the main circuit breaker, put the load into operation, and according to the load voltage U L According to the change of load voltage U, the inverter output of the AC / DC converter and the voltage output of the inverter module are adjusted to maintain the load voltage U L Stable; further, when the brushless doubly-fed motor operates in an overload condition, the frequency of the control winding input voltage can be adjusted by the AC-DC-AC inverter, thereby reducing the frequency of the motor power winding side, enhancing the magnetic field strength, and improving the motor overload capacity; finally, according to the actual working conditions, the output voltage amplitude, frequency, and phase can be adjusted by the inverter module to synchronize with the power grid and achieve grid-connected operation.

[0056] In one embodiment, if Figure 3 As shown, S4 includes: S41: when the DC bus voltage is determined by the output voltage of the power winding, disconnect the grid switch or the battery switch, close the main circuit breaker or the grid-connected switch; adjust the inverter module and the AC-DC-AC inverter so that the inverter module outputs a load voltage U with a fixed amplitude and frequency L ; S42: When the DC bus voltage is not determined by the output voltage of the power winding, repeat S3.

[0057] In one embodiment, the control method before S2 further includes: using a speed sensor to collect a speed signal n of the prime mover r And transmit it to the control winding side controller; use the voltage sensor to collect the DC bus voltage U dc and load voltage U L , and transmit it to the control winding side controller, and also collect the DC bus voltage U dc Transmitted to the power winding side controller.

[0058] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A brushless double-fed power generation system based on a dual frequency conversion structure, characterized in that: include: A brushless double-fed generator comprises: a rotor structure and a stator structure, wherein the stator structure comprises: an iron core, a power winding and a control winding; A control winding side controller is connected to the brushless double-fed generator to utilize the load voltage U L , DC bus voltage U dc And the speed signal of the prime mover n r Calculate the given voltage U c ' and given frequency f c '; The power winding side controller is used to convert the DC bus voltage U dc Convert to amplitude and frequency f L 'Constant load voltage U L ' and output; The AC-DC-AC inverter is connected to the control winding side controller and the control winding, and is used to establish the DC bus voltage and set its target value, and to generate a DC bus voltage at the given voltage. U c ' and the given frequency f c 'Control the control winding to output a voltage of suitable amplitude and frequency, so as to adjust the amplitude and frequency of the output voltage of the power winding; an uncontrolled rectifier module, connected to the power winding, and configured to enable the DC bus voltage to reach and maintain the target value when the DC bus voltage is determined by the output voltage of the power winding; An inverter module is connected to the uncontrolled rectifier module and the power winding side controller, and is used to maintain the output of a load voltage with a fixed amplitude and frequency when the DC bus voltage reaches the target value. U L , to supply power to the connected loads or to connect to the grid for grid-connected power supply.

2. The brushless double-fed power generation system based on the dual frequency conversion structure as claimed in claim 1, characterized in that: Also includes: A speed sensor is connected to the prime mover and the control winding side controller to collect the speed signal of the prime mover. n r and transmit it to the control winding side controller; A voltage sensor is connected to the control winding side controller and the power winding side controller to collect the DC bus voltage. U dc and load voltage U L and transmits it to the control winding side controller, and also collects the DC bus voltage U dc Transmitted to the power winding side controller.

3. The brushless double-fed power generation system based on the dual frequency conversion structure as claimed in claim 1, characterized in that: The DC bus of the AC-DC-AC inverter is connected in parallel with the DC bus of the uncontrolled rectifier module, so as to be finally connected to a load or a power grid through the inverter module to realize external power generation.

4. The brushless double-fed power generation system based on the dual frequency conversion structure as claimed in claim 1, characterized in that: The rotor structure includes at least one of windings, a squirrel cage, and a reluctance.

5. The brushless double-fed power generation system based on the dual frequency conversion structure as claimed in claim 1, characterized in that: The excitation mode of the brushless double-fed power generation system is a DC excitation mode or an AC excitation mode.

6. The brushless double-fed power generation system based on the dual frequency conversion structure as claimed in claim 5, characterized in that: When the excitation mode of the brushless doubly-fed power generation system is a DC excitation mode, the brushless doubly-fed power generation system further comprises a battery, which is connected across the DC bus of the AC-DC-AC inverter and the DC bus of the uncontrolled rectifier module; the battery supplies power to the brushless doubly-fed power generation system.

7. The brushless doubly-fed power generation system based on a dual frequency conversion structure as claimed in claim 5, characterized in that: When the excitation mode of the brushless double-fed power generation system is an AC excitation mode, the power grid is connected to the AC-DC-AC converter via a transformer, and the brushless double-fed power generation system is powered by the power grid.

8. A control method for a brushless doubly-fed power generation system based on a dual frequency conversion structure according to any one of claims 1 to 7, characterized in that: include: S1: When receiving the start command, the grid or battery provides initial excitation to enable the AC-DC-AC inverter to establish the DC bus voltage; S2: Control winding side controller using load voltage U L , DC bus voltage U dc And the speed signal of the prime mover n r Calculate the given voltage U c ' and given frequency f c '; S3: The AC-DC-AC inverter sets the target value of the DC bus voltage and U c ' and the given frequency f c 'Under the action of the control winding, the control winding outputs a voltage of suitable amplitude and frequency, so as to adjust the amplitude and frequency corresponding to the output voltage of the power winding; S4: When the DC bus voltage is determined by the output voltage of the power winding, the rectifier module is not controlled to make the DC bus voltage reach and maintain the target value; the inverter module is controlled to output a load voltage with a fixed amplitude and frequency. U L , to supply power to the connected loads or to connect to the grid for grid-connected power supply.

9. The control method of the brushless double-fed power generation system based on the dual frequency conversion structure as claimed in claim 8, characterized in that: The S4 includes: S41: When the DC bus voltage is determined by the output voltage of the power winding, disconnect the grid switch or the battery switch, and close the main circuit breaker or the grid-connected switch; adjust the inverter module and the AC-DC-AC converter so that the inverter module outputs a load voltage with a fixed amplitude and frequency. U L ; S42: When the DC bus voltage is not determined by the output voltage of the power winding, repeat S3.

10. The control method of the brushless doubly-fed power generation system based on the dual frequency conversion structure according to claim 8, characterized in that: The control method before S2 further includes: The speed sensor is used to collect the speed signal of the prime mover. n r and transmit it to the control winding side controller; Using voltage sensor to collect DC bus voltage U dc and load voltage U L , and transmit it to the control winding side controller, and also collect the DC bus voltage U dc Transmitted to the power winding side controller.

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