CN107196575A - A kind of switched reluctance motor current transformer and its control method - Google Patents

Abstract

A kind of switched reluctance motor current transformer and its control method, current transformer is combined by two inductance, six diodes, five switching tubes, three capacitors, three-phase windings, the wide scope regulation of power supply voltage is realized in the switch control of first switch pipe and second switch pipe, first capacitor can effectively accelerate phase winding switch off current speed, whole system is simple in construction vdiverse in function, only by a switching tube it is PWM control modes during the following operating mode of ultrahigh speed, reduces switching loss；The current transformer of the present invention is very suitable for applying in the high motor speed governing system of wide velocity interval, high efficiency demand, cost performance.

Description

A switched reluctance motor converter and its control method

technical field

The invention relates to the field of switched reluctance motors, in particular to a switched reluctance motor converter capable of quickly shutting off current through wide-range adjustment of power supply voltage and a simple converter circuit through a hardware circuit, and a simple control mode thereof.

Background technique

The switched reluctance motor has a simple and firm structure, no winding and no permanent magnet on the rotor, low cost, and has broad application prospects.

The switched reluctance motor cannot start and run automatically, and the converter is the center of its starting and running.

The traditional asymmetrical half-bridge converter has a large number of switching tubes and a complex structure.

The operation of the switched reluctance motor is based on the real-time position information of the rotor relative to the stator, and each winding is powered separately, so as to ensure the generation of positive torque, and it must be shut down quickly when it is turned off to prevent reverse torque, that is, braking torque. , but since the phase winding is equivalent to an inductive element, when it is turned off, the stored magnetic energy should be given a release path, so it is often necessary to turn off the switch tube connected to the phase winding in advance to facilitate the release of energy storage, otherwise the energy storage will be released When the current will produce braking torque.

The control methods of switched reluctance motors mainly include current PWM, voltage PWM, and switching angle control. The first two types greatly increase the switching loss of the switching tube, and the latter increases the complexity of the control system. Very long computing time, especially in the case of ultra-high-speed operation, places high demands on the controller.

The switched reluctance motor itself is more suitable for high-speed operation. In order to adapt to different speed requirements, a wider speed regulation range is expected by the industry in the requirements of the speed regulation system.

Contents of the invention

According to the above background technology, the present invention proposes a switched reluctance motor converter with simple converter circuit structure, fast shut-off of phase current, low switching loss and wide-range regulation of power supply voltage for wide-range speed regulation and its control. method.

Technical scheme of the present invention is:

A switched reluctance motor converter, which is composed of two inductors, six diodes, five switch tubes, three capacitors, and three-phase windings. Its technical feature is that one end of the first inductor is connected to the first two The cathode of the pole tube is connected and used as the positive pole of the converter input DC power supply, the other end of the first inductor is connected to the anode of the first switch tube and the anode of the second diode, and the cathode of the second diode is connected to the second diode The anode of the capacitor is connected to the anode of the second switch tube, the cathode of the second switch tube is connected to one end of the second inductor and the cathode of the third diode, and the anode of the third diode is connected to the negative pole of the third capacitor and the cathode of the first switch tube. The cathode of the three switching tubes, the cathode of the fourth switching tube, the cathode of the fifth switching tube, the anode of the third switching tube is connected to one end of the first phase winding and the anode of the fourth diode, and the anode of the fourth switching tube is connected to One end of the second phase winding is connected to the anode of the fifth diode, the anode of the fifth switching tube is connected to one end of the third phase winding and the anode of the sixth diode, and the anode of the first diode is connected to the anode of the sixth diode. A positive pole of a capacitor, a cathode of a fourth diode, a cathode of a fifth diode, and a cathode of a sixth diode; The positive pole, the other end of the first-phase winding, the other end of the second-phase winding, the other end of the third-phase winding, and serves as the negative pole of the converter input DC power supply.

A control method for a switched reluctance motor converter, characterized in that it refers to a method for controlling the switching of five switching tubes; wherein the switching control of the first switching tube and the second switching tube is specifically divided into four operating modes:

(1) The first switching tube is in an off state, the second switching tube is controlled by chopping PWM and the duty cycle is less than 1/2;

(2) The first switching tube is in an off state, the second switching tube is in a chopping PWM control mode and the duty cycle is equal to 1/2;

(3) The first switching tube is in an off state, the second switching tube is controlled by chopping PWM and the duty cycle is greater than 1/2;

(4) The first switching tube chopping PWM control mode, the second switching tube chopping PWM control mode and the duty cycle is greater than 1/2;

The third switching tube, the fourth switching tube, and the fifth switching tube are single-pulse control methods, that is, according to the position information of the switched reluctance motor rotor, when it is judged which phase winding needs power supply, the switching tube connected in series with it is closed and turned on, and the According to the rotor position information, the switch tube is disconnected after the power supply of the phase winding is completed.

Technical effect of the present invention mainly contains:

(1) Compared with the traditional asymmetrical half-bridge converter, the present invention simplifies the structure and saves the cost;

(2) The voltage at both ends of the first capacitor accelerates the current drop rate when the phase winding is turned off, avoiding entering the braking zone, so that the turn-off time can be relatively delayed, the output of the motor is increased, and the efficiency of the motor system is also increased;

(3) When the voltage at both ends of the first capacitor exceeds the input power supply voltage, energy can be fed back to it, which improves the effective utilization rate of electric energy of the system;

(4) The converter of the present invention does not need an isolation link, thereby saving costs, simplifying the structure, and reducing weight;

(5) In the process of assisting the first capacitor to quickly reduce the current, no switching tube control is required, which reduces the complexity of control, improves reliability, and saves costs;

(6) The switching mode of the first switching tube and the second switching tube can adapt to a wider range of speed adjustment of the switched reluctance motor, and can fully utilize the advantages of the high-speed operation of the switched reluctance motor, and has a wide range of applications;

(7) The third switching tube, the fourth switching tube, and the fifth switching tube connected in series with the phase winding do not need chopping or PWM control methods, and adopt single pulse mode, and only the second switching tube is used when the ultra-high speed is below. The switching tube is controlled in PWM mode, which greatly reduces the switching loss of the whole system, and the more phase windings, the more obvious the advantage;

(8) In the converter and its control mode of the present invention, the switching angle can be fixed, and there is no need to adopt a switching angle control mode during high speed, which simplifies the complexity of control and improves reliability.

Description of drawings

Fig. 1 shows the circuit structure diagram of the switched reluctance motor converter of the present invention.

detailed description

A switched reluctance motor converter, as shown in Figure 1, consists of two inductors, six diodes, five switch tubes, three capacitors, and three-phase windings. One end of the first inductor L1 is connected to the first two-pole The cathode of the tube D1 is connected and used as the positive pole of the DC power input of the converter. The other end of the first inductor L1 is connected to the anode of the first switching tube V1 and the anode of the second diode D2, and the cathode of the second diode D2 is connected to the second capacitor C2 The positive pole and the anode of the second switch tube V2, the cathode of the second switch tube V2 is connected to one end of the second inductor L2 and the cathode of the third diode D3, the anode of the third diode D3 is connected to the negative pole of the third capacitor C3, and the cathode of the third switch tube V3 , the cathode of the fourth switching tube V4, the cathode of the fifth switching tube V5, the anode of the third switching tube V3 is connected to one end of the first phase winding A and the anode of the fourth diode D4, and the anode of the fourth switching tube V4 is connected to one end of the second phase winding B and the anode of the fifth diode D5, the anode of the fifth switching tube V5 is connected to one end of the third phase winding C and the anode of the sixth diode D6, the anode of the first diode D1 is connected to the anode of the first capacitor C1, the fourth diode The cathode of D4, the cathode of the fifth diode D5, the cathode of the sixth diode D6, the cathode of the first capacitor C1 is connected to the cathode of the first switching tube V1, the cathode of the second capacitor C2, the other end of the second inductor L2, and the anode of the third capacitor C3 , the other end of the first phase winding A, the other end of the second phase winding B, the other end of the third phase winding C, and serve as the negative pole of the converter input DC power supply.

In accompanying drawing 1, U1 is the DC power supply voltage of the switched reluctance motor.

A control method for a switched reluctance motor converter, which refers to a method for controlling the switching of five switching tubes, wherein the switching control of the first switching tube V1 and the second switching tube V2 is specifically divided into four operating modes:

(1) The first switching tube V1 is in the off state, the second switching tube V2 is in the chopper PWM control mode and the duty cycle is less than half; in this mode, the duty cycle of the first switching tube V1 is zero, according to The relationship between the voltage UC3 at both ends of the third capacitor C3 and the voltage at the input terminal U1:

In formula (1), α _v1 and α _v2 are the duty ratios of the first switching tube V1 and the second switching tube V2 respectively;

In (1) working mode, the actual power supply voltage UC3 will be less than U1, and the switched reluctance motor is located in the low-speed operating area;

(2) The first switching tube V1 is in the off state, the second switching tube V2 is in the chopping PWM control mode and α _v2 =1/2; the first switching tube V1 is off, that is, α _v1 =0, according to formula (1), it can be seen that In this mode, UC3=U1, the switched reluctance motor is at the base speed operating condition;

(3) The first switching tube V1 is in the disconnected state, that is, α _v1 = 0, the second switching tube V2 is in the chopper PWM control mode and α _v2 >1/2; according to formula (1), it can be seen that UC3 > U1 in this mode, the switching magnetic The resistance motor is located in the high-speed operation area;

(4) The chopping PWM control mode of the first switching tube V1, the chopping PWM control mode of the second switching tube V2 and α _v2 >1/2; in this mode, UC3>>U1, the switched reluctance motor is located in the ultra-high speed area;

According to the rotor position information of the switched reluctance motor, when it is detected that the first phase winding A needs to be energized, the third switch tube V3 is closed and turned on, forming a power supply circuit of C3-A-V3-C3, and the corresponding second phase winding B is energized Then the fourth switching tube V4 is closed and conducting, and the fifth switching tube V5 is closed and conducting when the third phase winding C is energized; the third switching tube V3, the fourth switching tube V4, and the fifth switching tube V5 are all single-pulse control methods , that is, according to the rotor position information of the switched reluctance motor, when it is judged which phase winding needs power supply, the switch tube connected in series with it is turned on and turned on, and the switch tube is disconnected after the power supply of the phase winding is completed according to the rotor position information; the switch tube is disconnected. After the switching tube, the magnetic energy of the phase winding in series with it is transferred to the first capacitor C1, and at this time due to the effect of the terminal voltage of the first capacitor C1, the current of the phase winding will quickly drop to zero after the switching tube is turned off, avoiding entering the brake area.

Regarding the work of the converter part between UC3 and U1, when the first switch tube V1 remains in the off state, the second switch tube V2 is turned on and the second inductor L2 is charged, and when the second switch tube V2 is turned off The electric energy of the second inductor L2 is released to the third capacitor C3 and the energized phase winding; when the first switch tube V1 is switched and controlled by PWM mode, when it is closed and turned on, U1 charges the first inductor L1 through the first switch tube V1, which When it is turned off, U1 and the energy storage of the first inductor L1 supply power through the second switch tube V2.

Claims (2)

1. A switched reluctance motor converter, consisting of two inductors, six diodes, five switch tubes, three capacitors, and three-phase windings, its technical feature is that one end of the first inductor is connected to the second The cathode of a diode is connected as the anode of the DC power input of the converter, the other end of the first inductance is connected to the anode of the first switching tube and the anode of the second diode, and the cathode of the second diode is connected to the anode of the second diode The anode of the second capacitor is connected to the anode of the second switch tube, the cathode of the second switch tube is connected to one end of the second inductor and the cathode of the third diode, and the anode of the third diode is connected to the cathode of the third capacitor and the anode of the second switch tube. The cathode of the third switching tube, the cathode of the fourth switching tube, the cathode of the fifth switching tube, the anode of the third switching tube is connected to one end of the first phase winding and the anode of the fourth diode, and the fourth switching tube The anode is connected to one end of the second phase winding and the anode of the fifth diode, the anode of the fifth switching tube is connected to one end of the third phase winding and the anode of the sixth diode, and the anode of the first diode is connected to the anode of the sixth diode. The positive pole of the first capacitor, the cathode of the fourth diode, the cathode of the fifth diode, and the cathode of the sixth diode, the negative pole of the first capacitor is connected to the cathode of the first switching tube, the negative pole of the second capacitor, the other end of the second inductor, the cathode of the sixth diode The positive pole of the three capacitors, the other end of the first phase winding, the other end of the second phase winding, and the other end of the third phase winding are used as the negative pole of the converter input DC power supply. 2. A control method for a switched reluctance motor converter, characterized in that it refers to the switch control method of five switch tubes; Among them, the switching control of the first switching tube and the second switching tube is specifically divided into four working modes: (1) The first switching tube is in an off state, the second switching tube is controlled by chopping PWM and the duty cycle is less than 1/2; (2) The first switching tube is in an off state, the second switching tube is in a chopping PWM control mode and the duty cycle is equal to 1/2; (3) The first switching tube is in an off state, the second switching tube is controlled by chopping PWM and the duty cycle is greater than 1/2; (4) The first switching tube chopping PWM control mode, the second switching tube chopping PWM control mode and the duty cycle is greater than 1/2; The third switching tube, the fourth switching tube, and the fifth switching tube are single-pulse control methods, that is, according to the position information of the switched reluctance motor rotor, when it is judged which phase winding needs power supply, the switching tube connected in series with it is closed and turned on, and the According to the rotor position information, the switch tube is disconnected after the power supply of the phase winding is completed.