阅读说明：本技术 一种开关磁阻风力发电机半自励功率变换器 (Semi-self-excitation power converter of switched reluctance wind driven generator ) 是由 闫荣格 李红玉 于 2021-03-22 设计创作，主要内容包括：本发明为一种开关磁阻风力发电机半自励功率变换器。该转换器的组成包括：由直流电源、开关磁阻发电机的三相绕组、三相上功率开关器件、三相下功率开关器件、与各相绕组组成续流回路的三个二极管和三个功率开关器件、滤波电容C-1、储能电容C-2组成。各相绕组所在功率变换支路可以独立工作,互不干扰。本发明所提出的开关磁阻风力发电机半自励功率变换器中,在励磁阶段,通过增加励磁电压,从而增加最后的励磁电流和磁场储能的大小,使开关磁阻发电机输出功率得到提升；在发电阶段,开关磁阻发电机绕组两端的电压小于励磁电压,利于低风速时开关磁阻发电机的有效发电,而且使得控制策略更加的灵活。(The invention relates to a semi-self-excitation power converter of a switched reluctance wind driven generator. The converter comprises the following components: the three-phase power supply, three-phase windings of the switched reluctance generator, three-phase upper power switch devices, three-phase lower power switch devices, three diodes and three power switch devices which form a follow current loop with the windings of each phase, and a filter capacitor C 1 And an energy storage capacitor C 2 And (4) forming. The power conversion branches where the windings of each phase are located can work independently and do not interfere with each other. In the semi-self-excitation power converter of the switched reluctance wind driven generator, the output power of the switched reluctance wind driven generator is improved by increasing the excitation voltage in the excitation stage so as to increase the final excitation current and the magnitude of magnetic field energy storage; in the power generation stage, the voltage at two ends of the winding of the switched reluctance generator is smaller than the excitation voltage, so that the effective power generation of the switched reluctance generator at low wind speed is facilitated, and the control strategy is more flexible.)

1. A semi-self-excited power converter of a switched reluctance wind generator is characterized in that the converter comprises:

positive pole of DC power supply V and diode D₁Is connected with the anode, the cathode and the filter capacitor C₁The negative electrodes are connected; diode D₁Respectively with one end of a resistor R and a filter capacitor C₁The positive electrodes of the two electrodes are connected; filter capacitor C₁And the anode of the capacitor C₂The negative electrodes are connected; energy storage capacitor C₂Anode and diode D₂Is connected to the anode of a diode D₂The cathode of the resistor is connected with the other end of the resistor R; filter capacitor C₁And the negative pole of the power switch device Q_ALPower switch device Q_BLPower switch device Q_CLThe emitting electrodes are connected; energy storage capacitor C₂And the positive electrode of the power switch device Q_AHPower switch device Q_BHPower switch device Q_CHThe collector electrodes are connected; energy storage capacitor C₂And the negative pole of the power switch device Q_APower switch device Q_BPower switch device Q_CThe collector electrodes are connected; power switch device Q_APower switch device Q_BPower switch device Q_CEmitter correspondence and power switching device Q_AHPower switch device Q_BHPower switch device Q_CHThe emitting electrodes are connected; power switch device Q_AHPower switch device Q_BHPower switch device Q_CHThe emitting electrodes are also correspondingly connected with the upper ends of the winding A, the winding B and the winding C respectively; the lower ends of the winding A, the winding B and the winding C are respectively connected with a power switch device Q_ALPower switch device Q_BLPower switch device Q_CLThe collector electrodes are connected; the lower ends of the winding A, the winding B and the winding C are respectively connected with a diode D_AHDiode D_BHDiode D_CHOf the anode of diode D_AHDiode D_BHDiode D_CHAnd a power switching device Q_AHPower switch device Q_ALPower switch device Q_BHTo the collector of (a).

2. A switched reluctance wind generator system is characterized by comprising a wind turbine, a switched reluctance motor, a direct current power supply, a semi-self-excitation power converter of the switched reluctance wind generator as claimed in claim 1, a position sensor, a controller, an energy storage unit and a load; the wind turbine, the switched reluctance wind driven generator semi-self-excitation power converter and the position sensor are respectively connected with the switched reluctance generator; the semi-self-excitation power converter of the switched reluctance wind driven generator is also connected with a direct-current power supply, a controller and an energy storage unit; the position sensor is also connected with the controller; the energy storage unit and the switch reluctance wind driven generator semi-self-excitation power converter are also respectively connected with a load.

Technical Field

The invention belongs to the technical field of drive control and power converter design of a switched reluctance wind driven generator, and particularly relates to a semi-self-excitation power converter of a switched reluctance wind driven generator.

Background

As global warming continues to grow in severity, clean, reliable, stable, and sustainable energy structures are becoming a major global focus of attention. In the traditional power generation mode, a large amount of pollution gas is discharged in the power generation process, and resources are wasted due to insufficient combustion, so that the traditional power generation mode is not in line with the theme of current green development. Compared with conventional fuels, wind energy is a very clean, environmentally friendly, green energy source and has great advantages due to its huge energy reserve. The operation of the device does not generate wastes polluting the environment and can be inexhaustible. Therefore, the popularization of wind power generation energy enables resources to become sustainable, and has irreplaceable practical significance for reducing environmental pollution.

As is well known, a wind power generator is the most central device in the whole wind power generation system, and can convert mechanical energy into electrical energy. The working condition of the wind driven generator has influence on the state of the whole system, including the efficiency and quality of the system power generation, and has great and direct influence on the performance and working condition of other links in the system. In the current wind power market, there are many types of wind power generators. The switched reluctance generator is used as a novel electromechanical energy conversion device, has the advantages of simple structure, strong fault-tolerant capability, wide rotating speed range, no permanent magnet, low manufacturing cost, high temperature resistance, higher efficiency than an asynchronous generator and the like, and is successfully applied to various occasions, particularly occasions with severe environment such as wind power generation and the like.

When the switched reluctance wind driven generator system adopts a traditional asymmetric half-bridge power converter, the voltage values at two ends of a phase winding in an excitation stage are in a direct proportion relation with the magnitude of phase current, the larger the excitation voltage is, the larger the final excitation current of the phase winding is, the more energy is stored in a motor magnetic field, and the more power generation is facilitated; however, in the power generation stage, if the wind speed is low, the rotation speed of the motor is also reduced, the generated voltage is greater than the moving electromotive force, the phase current cannot be increased continuously in the power generation stage, and the generator system cannot generate power effectively. Because the voltage values in the excitation stage and the power generation stage in the traditional asymmetric half-bridge power converter are the same, independent adjustment cannot be performed, and control and effective power generation of the switched reluctance wind driven generator are not facilitated, so that the electric energy generated by the switched reluctance wind driven generator is greatly reduced when the wind speed is low. Therefore, how to improve the power generation capacity and the power generation efficiency of the switched reluctance wind driven generator at low wind speed is a hot problem in the research and development of the current wind power field. The patent "a switched reluctance generator system for realizing fast excitation/demagnetization, CN 103475292A", the system comprises a switched reluctance motor body, a prime mover, a position sensor, a power converter, a dc power supply and a controller, by adopting a four-level power converter, as shown in fig. 1, fast excitation can be realized in the excitation stage, and fast demagnetization can be realized in the power generation stage when two voltage sources are adopted; however, when two voltage sources are selected in the power generation stage, if the power diode D1 fails, the generator cannot operate normally, and thus the fault tolerance is low. In addition, the power generation phase generally uses two voltage sources, and the power generation phase does not select the state-1 unless the system fails to charge the energy storage capacitor excessively. Therefore, under the normal and stable operation state of the system, the excitation voltage and the power generation voltage in the power generation stage are equal, and the problem of low power generation efficiency of the low-wind-speed switched reluctance wind driven generator still cannot be effectively solved.

Disclosure of Invention

The invention aims to provide a semi-self-excitation power converter of a switched reluctance wind driven generator, aiming at the defects in the prior art. The converter provides a new topological structure, and the output power and the generating efficiency of the switched reluctance wind driven generator at low wind speed are improved through the energy storage capacitor and the three power switch devices; the existence of the three power switching devices enables the excitation voltage and the generation voltage to have different voltage values, so that the control and the regulation are more convenient; the power conversion branches where the windings of each phase are located can work independently and do not interfere with each other, and if a power switch device corresponding to one winding fails, the other two phases can still run normally.

The technical scheme of the invention is as follows:

a semi-self-excited power converter of a switched reluctance wind generator comprises the following components:

positive pole and two of DC power supply VPolar tube D₁Is connected with the anode, the cathode and the filter capacitor C₁The negative electrodes are connected; diode D₁Respectively with one end of a resistor R and a filter capacitor C₁The positive electrodes of the two electrodes are connected; filter capacitor C₁And the anode of the capacitor C₂The negative electrodes are connected; energy storage capacitor C₂Anode and diode D₂Is connected to the anode of a diode D₂The cathode of the resistor is connected with the other end of the resistor R; filter capacitor C₁And the negative pole of the power switch device Q_ALPower switch device Q_BLPower switch device Q_CLThe emitting electrodes are connected; energy storage capacitor C₂And the positive electrode of the power switch device Q_AHPower switch device Q_BHPower switch device Q_CHThe collector electrodes are connected; energy storage capacitor C₂And the negative pole of the power switch device Q_APower switch device Q_BPower switch device Q_CThe collector electrodes are connected; power switch device Q_APower switch device Q_BPower switch device Q_CEmitter correspondence and power switching device Q_AHPower switch device Q_BHPower switch device Q_CHThe emitting electrodes are connected; power switch device Q_AHPower switch device Q_BHPower switch device Q_CHThe emitting electrodes are also correspondingly connected with the upper ends of the winding A, the winding B and the winding C respectively; the lower ends of the winding A, the winding B and the winding C are respectively connected with a power switch device Q_ALPower switch device Q_BLPower switch device Q_CLThe collector electrodes are connected; the lower ends of the winding A, the winding B and the winding C are respectively connected with a diode D_AHDiode D_BHDiode D_CHOf the anode of diode D_AHDiode D_BHDiode D_CHAnd a power switching device Q_AHPower switch device Q_BHPower switch device Q_CHTo the collector of (a).

A switched reluctance wind driven generator system comprises a wind turbine, a switched reluctance motor, a direct current power supply, a switched reluctance wind driven generator semi-self-excitation power converter, a position sensor, a controller, an energy storage unit and a load; the wind turbine, the switched reluctance wind driven generator semi-self-excitation power converter and the position sensor are respectively connected with the switched reluctance generator; the semi-self-excitation power converter of the switched reluctance wind driven generator is also connected with a direct-current power supply, a controller and an energy storage unit; the position sensor is also connected with the controller; the energy storage unit and the switch reluctance wind driven generator semi-self-excitation power converter are also respectively connected with a load.

The invention has the substantive characteristics that:

in the prior art, the switch reluctance wind driven generator has low output power when running under the condition of low external wind speed, and cannot generate electricity effectively. The invention provides a topological structure of a novel power converter by improving a traditional asymmetric half-bridge power converter on the basis of the operation principle of a switched reluctance generator. The added energy storage capacitor and the three power switch devices improve the output power and the power generation efficiency of the switched reluctance wind driven generator at low wind speed; the existence of the three power switching devices enables the excitation voltage and the generation voltage to have different voltage values, so that the control and the regulation are more convenient; the power conversion branches where the windings of each phase are located can work independently and do not interfere with each other, and if a power switch device corresponding to one winding fails, the other two phases can still run normally.

The invention has the beneficial effects that:

(1) in the semi-self-excitation power converter of the switched reluctance wind driven generator, the power conversion branches where the windings of all phases are located can work independently and do not interfere with each other, so that the semi-self-excitation power converter is suitable for occasions where the power conversion branches where the windings of two phases work simultaneously, and has strong expandability.

(2) The semi-self-excitation power converter of the switched reluctance wind driven generator, which is provided by the invention, particularly aims at the problems that the electric energy generated by the low-wind-speed switched reluctance wind driven generator is greatly reduced and the low-wind-speed switched reluctance wind driven generator cannot effectively generate power, and can effectively improve the power generation capacity and the power generation efficiency of the switched reluctance wind driven generator at low wind speed. Compared with the conventional asymmetric half-bridge power converter shown in fig. 2, under the condition that the on angle, the off angle, the external direct-current power supply and other related parameters are the same, the output power of the switched reluctance wind driven generator under the semi-self-excited power converter is greatly increased, and the output power is improved by about 2840W in the embodiment as shown in a comparison graph of fig. 9. Compared with the four-level power converter shown in fig. 1, the semi-self-excited power converter of the switched reluctance wind turbine generator has higher power generation efficiency, and the output power of the semi-self-excited power converter is higher than that of the semi-self-excited power converter shown in fig. 10 by about 2800W.

(3) In the semi-self-excitation power converter of the switched reluctance wind driven generator, the voltages at two ends of the winding have different voltage values in the excitation stage and the power generation stage, so that the control strategy is more flexible, and the effective power generation of the switched reluctance wind driven generator is facilitated.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without inventive labor.

Fig. 1 is a schematic diagram of a four-level power converter topology.

Fig. 2 is a schematic diagram of a conventional asymmetric half-bridge power converter topology.

Fig. 3 is a block diagram of a switched reluctance wind turbine system.

FIG. 4 is a schematic diagram of a switched reluctance wind turbine semi-self-excited power converter topology according to the present invention.

FIG. 5 is a schematic diagram of an excitation current path of an initial excitation mode in an operating mode of a switched reluctance wind turbine semi-self-excited power converter of the present invention;

FIG. 6 is a schematic current path diagram of the switched reluctance wind turbine in a freewheeling mode of the operating mode of the semi-self-excited power converter of the present invention;

fig. 7 is a schematic output current path diagram of the switched reluctance wind turbine in the power generation mode in the semi-self-excited power converter operation mode of the invention.

Fig. 8 is a simulation diagram of a switched reluctance wind turbine system under the semi-self-excited power converter of the present invention.

Fig. 9 is a comparison graph of output power of the switched reluctance wind generator system under the condition that the semi-self-excitation power converter of the invention and the traditional asymmetric half-bridge power converter are compared.

FIG. 10 is a graph comparing the output power of the switched reluctance wind turbine system with a semi-self-excited power converter and a four-level power converter according to the present invention.

Detailed Description

The following detailed description of embodiments of the invention is provided in connection with the accompanying drawings.

In this embodiment, the whole switched reluctance wind turbine generator system is shown in fig. 3, and includes a wind turbine, a switched reluctance motor, a dc power supply, a power converter, a position sensor, a controller, an energy storage unit, and a load; the wind turbine, the power converter and the position sensor are respectively connected with the switched reluctance generator; the power converter is also connected with a direct current power supply, the controller and the energy storage unit; the position sensor is also connected with the controller; the energy storage unit and the power converter are also respectively connected with a load.

The switched reluctance generator is the electromechanical energy conversion core of the whole power generation system, converts mechanical energy into electric energy, and operates according to the minimum reluctance principle; the power converter is an energy input and output channel of the system, and adopts a semi-self-excitation power converter; the position encoder is used for providing position information of the motor rotor; the controller is a control center of the whole system, and is used for carrying out centralized processing on signals acquired by the current sensor, the voltage sensor and the position sensor, controlling the working state of a main switching device in the power converter and realizing the control of the running state of the switched reluctance generator.

(1) Semi-self-excitation power converter topological structure of switched reluctance wind driven generator

The switched reluctance wind driven generator semi-self-excitation power converter is shown in fig. 4 and comprises a direct current power supply, a three-phase winding of a switched reluctance wind driven generator, a three-phase upper power switch device, a three-phase lower power switch device, three diodes and three power switch devices, wherein the three diodes and the three power switch devices form a follow current loop with each phase winding, and a filter capacitor C₁And an energy storage capacitor C₂And (4) forming. The power conversion branches where the windings of each phase are located can work independently and do not interfere with each other.

Positive pole of DC power supply V and diode D₁Is connected with the anode, the cathode and the filter capacitor C₁The negative electrodes are connected; diode D₁Respectively with one end of a resistor R and a filter capacitor C₁The positive electrodes of the two electrodes are connected; filter capacitor C₁And a filter capacitor C₂The negative electrodes are connected; filter capacitor C₂Anode and diode D₂Is connected to the anode of a diode D₂The cathode of the resistor is connected with the other end of the resistor R; filter capacitor C₁And the negative pole of the power switch device Q_ALPower switch device Q_BLPower switch device Q_CLThe emitting electrodes are connected; filter capacitor C₂And the positive electrode of the power switch device Q_AHPower switch device Q_BHPower switch device Q_CHThe collector electrodes are connected; filter capacitor C₂And the negative pole of the power switch device Q_APower switch device Q_BPower switch device Q_CThe collector electrodes are connected; power switch device Q_APower switch device Q_BPower switch device Q_CEmitter correspondence and power switching device Q_AHPower switch device Q_BHPower switch device Q_CHThe emitting electrodes are connected; power switch device Q_AHPower switch device Q_BHPower switch device Q_CHThe emitting electrodes are respectively connected with the upper ends of the winding A, the winding B and the winding C correspondingly, and the lower ends of the winding A, the winding B and the winding C are respectively connected with the power switch device Q_ALPower switch device Q_BLPower switch device Q_CLThe emitting electrodes are connected; the lower ends of the winding A, the winding B and the winding C are respectively connected with the diode D_AHDiode D_BHDiode D_CHOf the anode of diode D_AHDiode D_BHDiode D_CHAnd a power switching device Q_AHPower switch device Q_ALPower switch device Q_BHThe collector of (2) is connected;

the power switch device Q_AH、Q_AL、Q_BH、Q_BL、Q_CH、Q_CL、Q_A、Q_B、Q_CAll the devices are fast full-control power electronic devices, and IGBT or MOSFET can be adopted.

The diode D₁、D₂Is a common diode, diode D_AH、D_BH、D_CHAre freewheeling diodes.

The voltage of the direct-current power supply is 50V.

(2) Mode of operation

The semi-self-excitation power converter of the switched reluctance wind driven generator has different excitation voltage and generation voltage and has three working modes: an excitation mode, a freewheel mode, and a generation mode. The working mode of the semi-self-excitation power converter of the switched reluctance wind driven generator is described by taking the A-phase winding as an example.

Fig. 5 is a schematic diagram of an excitation mode of the switched reluctance wind turbine, and electric energy and mechanical energy provided by the wind turbine are converted into magnetic energy in an excitation stage and stored in a winding. The excitation stage is a power switch device Q_AH、Q_ALClosed, Q_AOff and the capacitance C₁、C₂Voltage U across_m＝U_o+U₁Then the excitation voltage is U_o+U₁The excitation phase is equivalent to providing excitation to the stator winding a from two voltage sources.

Fig. 6 is a schematic diagram of a freewheeling mode of a semi-self-excited power converter of a switched reluctance wind turbine, in which magnetic energy stored in a winding is converted into electric energy in a freewheeling stage, and freewheeling is performed in a freewheeling circuit. Freewheeling mode being power switching device Q_AHClosed, Q_AL、Q_ADisconnected when the A-phase winding passes through the freewheeling diode D_AHAnd a power switching device Q_AHForm a closed loop to carry out follow current, and the phase winding is in a follow current state.

Fig. 7 is a schematic diagram of a power generation mode of a semi-self-excitation power converter of a switched reluctance wind driven generator, and during a power generation stage, electric energy is transmitted to a load and an energy storage capacitor through a closed loop to supply power to the load and the energy storage capacitor. Power switch device Q in power generation stage_AH、Q_ALAre all off, Q_AClosed through a freewheeling diode D_AHPower switch device Q_AEnergy is delivered to a load R and an energy storage capacitor C₂The generated voltage is U_o。

And the winding B and the winding C are the same as the winding A, and the power switching device for controlling each phase of winding is subjected to switching control according to the rotor position information to carry out excitation and power generation respectively.

In the excitation stage, the phase current is in direct proportion to the voltage at two ends of the phase winding, and the larger the excitation voltage is, the larger the phase current is, the larger the magnetic field energy storage is, and the larger the output power is. Compared with the traditional asymmetric half-bridge power converter, under the condition of the same parameters and in the angle position control mode, the semi-self-excitation power converter of the switched reluctance wind driven generator provided by the invention excites the winding by utilizing two voltage sources, and the voltage at two ends of the phase winding, namely the excitation voltage is U_m＝U_o+U₁The final exciting current is increased, that is, the current entering the power generation area is increased, so that an ideal current waveform is easily obtained, and the magnetic field energy storage is increased, so that the output power of the switched reluctance wind driven generator is increased; under the condition that the voltage at the direct-current bus end, the turn-on angle, the turn-off angle and the reference current are the same, when a current chopping control mode is adopted, the excitation time when the phase current in the switched reluctance wind driven generator power converter reaches the reference current is reduced, namely the length of an excitation area is reduced, so that the power generation area is increased, the power generation time is prolonged, the power generation amount is increased, and the output power of the switched reluctance wind driven generator at low wind speed is improved.

When the motor enters a power generation area, the magnitude of the phase current reflects the strength of the winding excitation and the magnitude of the energy stored in the magnetic field of the motor. In order to enable the current to continue to increase in the power generation region regardless of the winding resistance, and to achieve efficient power generation, the following equation needs to be satisfied at the beginning of the power generation region:

in the formula (1), L_kIs the winding inductance (unit: H); i.e. i_kIs the k-th phase winding current (unit: A); u shape_kIs the kth phase winding generated voltage (unit: V); θ is the rotor angular position (unit: rad); omega is the angular speed (unit: rad/s) of the rotating machine of the motor; im is the current at the end of the excitation phase (unit: a), i.e. the final excitation current.

The formula (1) is the condition that the switch reluctance generator can effectively generate power, and the power generation stage is in an inductance reduction region, namelyHerein, therefore whenWhen the power generation is carried out, namely the running electromotive force is larger than the power generation voltage, the increment of the current is positive, the phase current continues to rise in the power generation stage, and the switched reluctance generator outputs electric energy to realize the power generation operation. If the generated voltage is too large, and the moving electromotive force is smaller than the generated voltage, the phase current cannot be continuously increased in the power generation stage, and thus an ideal current waveform cannot be obtained. Because omega is smaller and the motion electromotive force is smaller when the wind speed is lower, when the motion electromotive force is smaller than the power generation voltage, the phase winding current cannot be increased at the moment of turn-off of the power switch tube, and the utilization rate and the efficiency of the switched reluctance wind driven generator are reduced. Therefore, when the rotating speed is constant, the condition of effectively generating power by the switched reluctance generator can be met by increasing the final exciting current or reducing the generated voltage or simultaneously increasing the final exciting current and the generated voltage.

Since in a semi-self-excited power converter, the generated voltage is less than the excitation voltage. If the excitation voltage of the semi-self-excited power converter is equal to that of the traditional asymmetric half-bridge power converter, in the semi-self-excited power converter, because the generated voltage is smaller than the excitation voltage, the formula (1) is more easily satisfied at low wind speed, and an ideal current waveform is more easily obtained, so that the switched reluctance wind driven generator can relatively easily realize effective power generation, and the output power of the switched reluctance wind driven generator is increased. In addition, the voltages at the two ends of the winding have different voltage values in the excitation stage and the power generation stage, so that the control strategy is more flexible, and the effective power generation of the switched reluctance generator is facilitated.

In addition, the voltage across the stator winding is U during the excitation phase_o+U₁The voltage across the stator winding is U during the generation phase_oAnd different voltage values are provided, so that the control strategy is more flexible.

(3) Control strategy

During the working period of the switched reluctance wind driven generator of the semi-self-excitation power converter in the embodiment, the operation principle of the switched reluctance wind driven generator needs to be combined, each phase winding is put into operation successively according to real-time rotor position information and is performed in a time-sharing manner, and each phase winding is divided into an excitation stage, a follow current stage and a power generation stage during the working period.

In the excitation stage, according to the operation principle of the switched reluctance generator and in combination with the position information of the rotor, when the winding A needs to be put into operation, the power switch device Q_AH、Q_ALIs closed, and Q_AThe power switch is disconnected (namely, a signal is transmitted to the controller through the position sensor, and the controller detects the signal and then controls the full-control type power switch device to be switched on and off), because of the energy storage capacitor C₂Is charged with electric power, then the capacitor C₁、C₂Voltage at both ends is U_m＝U_o+U₁Wherein U is_oIs the voltage across the energy storage capacitor, U₁Is the voltage supplied by the DC power supply, i.e. the filter capacitor C₁The voltage across the terminals. The excitation phase is equivalent to the excitation of the stator winding by two voltage sources, and the loop is: c₁—C₂—Q_AH—A—Q_AL。

A follow current stage according to the rotorPosition information and the turn-off time requirement of the control system on the turn-off angle, the power switching device Q at the end of the excitation phase_AHClosed, Q_AL、Q_ADisconnected when the A-phase winding passes through the freewheeling diode D_AHAnd a power switching device Q_AHA closed loop is formed: a to D_AH—Q_AHThen, the current continues, and the phase winding is in the current continuing state.

A power generation stage, in which the power switch device Q is disconnected after the follow current stage is finished according to the rotor position information and the turn-off time requirement of the control system on the turn-off angle_AH、Q_ALClosing the power switch device Q_AEntering the power generation stage, specifically via a freewheeling diode D_AHPower switch device Q_AProviding a follow current path for the winding A to follow current outwards for generating power, i.e. to the energy storage capacitor C₂Charging and load power supply, the loop is: a to D_AH—C₂—Q_A。

And the winding B and the winding C are the same as the winding A, and the power switching device for controlling each phase of winding is subjected to switching control according to the rotor position information to carry out excitation and power generation respectively.

The invention designs a semi-self-excitation power converter of a switched reluctance wind driven generator, wherein a simulation diagram of a switched reluctance wind driven generator system is shown in fig. 8, a three-phase 6/4 pole is selected for a switched reluctance motor, the voltage of a direct-current power supply is set to be 50V, the load resistance is 50 omega, the rated rotating speed of the generator is set to be 1000r/min, the on-off angle is 1 degree, the off angle is 20 degrees, and the wind speed is 4 m/s. Compared with the traditional asymmetric half-bridge power converter and the four-level power converter, under the condition that the turn-on angle, the turn-off angle, the external direct-current power supply and other related parameters are the same, the output power of the switched reluctance wind driven generator under the semi-self-excited power converter is greatly increased, and a comparison graph of the output power of the switched reluctance wind driven generator with the traditional asymmetric half-bridge power converter is shown in a graph of fig. 9, and a comparison graph of the output power of the four-level power converter is shown in a graph of fig. 10. Due to the added energy storage capacitor and the special position of the energy storage capacitor, the excitation voltage of the semi-self-excitation power converter of the switched reluctance wind driven generator provided by the invention is greater than that of the traditional asymmetric half-bridge power converter. In the excitation stage, the phase current is in direct proportion to the voltage at two ends of the phase winding, so that the magnetic field energy storage is larger, and the output power of the switched reluctance wind driven generator can be effectively improved when the wind speed is lower. Because the generating voltage is less than the exciting voltage, an ideal current waveform is easier to obtain at low wind speed, so that the switched reluctance wind driven generator can relatively easily realize effective power generation, and the output power of the switched reluctance wind driven generator is increased. In addition, the voltage at the two ends of the winding has different voltage values in the excitation stage and the power generation stage, so that the control strategy is more flexible.

Compared with the prior art, the simulation of the figure 1 only makes the simulation of the power generation mode-2, namely the simulation under the normal working state. Due to the energy storage capacitor C in FIG. 1_dc1The system is always in a charging and discharging state, two voltage sources are generally adopted in the power generation stage, and the power generation stage can select the state-1 unless the system fails to excessively charge the energy storage capacitor. Therefore, under the normal and stable operation state of the system, the excitation voltage and the power generation voltage in the power generation stage are equal, and the problem that the low-wind-speed switched reluctance wind driven generator cannot effectively generate power cannot be solved. Compared with the four-level power converter shown in fig. 1, the semi-self-excited power converter of the switched reluctance wind turbine generator has higher power generation efficiency, and the output power of the semi-self-excited power converter is higher than that of the semi-self-excited power converter shown in fig. 10 by about 2800W.

From the above, it can be seen that, compared with the conventional asymmetric half-bridge power converter and the four-level power converter, the half-self-excited power converter of the switched reluctance wind turbine provided by the invention can enable the switched reluctance wind turbine to realize effective power generation relatively easily at low wind speed, and increase the output power of the switched reluctance wind turbine at low wind speed. In addition, in the invention, the excitation voltage and the generating voltage can take different voltage values, thereby being convenient for control and adjustment.

Although the present embodiment describes a three-phase switched reluctance wind turbine, it can be seen from the above description that the structure and control of the switched reluctance wind turbine for other phases are the same, and the problem of increasing or decreasing the power switches and diodes corresponding to the number of phases is still within the protection scope.

The invention is not the best known technology.