CN114465548A - Low-cost self-boosting power converter for switched reluctance motor and control strategy thereof - Google Patents

Abstract

The invention relates to the technical field of motors, and provides a low-cost self-boosting power converter for a switched reluctance motor and a control strategy thereof, wherein the power converter comprises a direct-current power supply unit, an energy storage capacitor, 8 controllable switching tubes, 6 diodes and 2 current sensors; the power converter has 5 working modes, such as a high-voltage excitation mode, a low-voltage excitation mode, an upper zero-voltage follow current mode, a lower zero-voltage follow current mode, a negative high-voltage follow current mode and the like; the control strategy of the power converter adopts two current sensors to realize the detection of four-phase current, and effectively adjusts 5 working modes according to a conduction interval, the voltage of an energy storage capacitor and the node temperature of a device, thereby realizing the orderly normal operation of the power converter; meanwhile, the high-voltage excitation mode and the low-voltage excitation mode exist simultaneously, so that the fault-tolerant capability can be effectively improved, and the method has good engineering application value.

Description

A low-cost self-boost power converter for switched reluctance motor and its control strategy

technical field

The invention relates to the technical field of motors, in particular to a low-cost self-boost power converter for switched reluctance motors and a control strategy thereof.

Background technique

With the gradual popularization of switched reluctance motor in the application of new energy vehicles, its own problems of large torque ripple and low system efficiency have become the decisive factors restricting its own development. In order to solve the problems of large torque ripple and low system efficiency, domestic and foreign scholars have achieved good application results by designing new motor structures, new power converter topologies and new control algorithms. Among them, the combination of the new power converter and the new control algorithm does not need to change the motor topology, and has a good application prospect. However, new power converters and control strategies have gradually become a challenge to improve the performance of switched reluctance motors due to the highly nonlinear characteristics and pulsed power supply mode of switched reluctance motors. Although domestic and foreign scholars have shown that increasing the bus voltage can improve the operating efficiency of the switched reluctance motor system, increase the flexibility of control, and reduce torque ripple. However, the existing boost-type power converters all need to add additional power devices and passive devices, which increases the operating cost of the system. Therefore, how to reduce the number and cost of system components while pumping up the bus voltage of the power converter is a problem worthy of study.

SUMMARY OF THE INVENTION

The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

Therefore, an object of the present invention is to propose a low-cost self-boost power converter for switched reluctance motor and its control strategy, so as to reduce the number of components used and system cost, and improve the response speed, long-distance efficiency and power density .

In order to achieve the above purpose, an embodiment of the present invention proposes a low-cost self-boost power converter for a switched reluctance motor and a control strategy thereof, including: a DC power supply unit, an energy storage capacitor, 8 controllable switch tubes, It consists of 6 diodes and 2 Hall current sensors; the DC power supply unit can be connected to a battery or a switching power supply; the cathode of the energy storage capacitor is connected to the anode of the DC power supply, the drains of the controllable switches S1 and S2, and the source of S1 is connected to The cathode of diode D1, the source of S7 and the positive poles of the A-phase and C-phase windings are connected, the source of S2 is connected to the cathode of diode D2, the source of S8 and the positive poles of the B-phase and D-phase windings, and the anode of the energy storage capacitor is connected to the diode The cathodes of D3, D4, D5 and D6 and the drains of the controllable switches S7 and S8 are connected together. The cathode of the power supply is connected to the anode of the diode D1, the anode of D2, the source of the controllable switch S3, the source of S4, the source of S5 and the source of S6. The drain of the controllable switch tube S3 is connected to the anode of the diode D3 and the negative pole of the phase A winding, the drain of the controllable switch tube S4 is connected to the anode of the diode D4 and the negative pole of the phase C winding, the drain of the controllable switch tube S5 is connected to the anode of the diode D5 It is connected to the negative pole of the B-phase winding, and the drain of the controllable switch tube S6 is connected to the anode of the diode D6 and the negative pole of the D-phase winding; the Hall current sensor L1 is used to measure the A-phase and C-phase current, and the Hall current sensor L2 is used to measure the B-phase. and D-phase current; the controllable switch tube is a commonly used MOSFET or IGBT.

Description of working principle: The proposed converter has five working modes: high-voltage excitation mode, low-voltage excitation mode, upper-tube zero-voltage freewheeling mode, lower-tube zero-voltage freewheeling mode and negative high-voltage freewheeling mode. Taking phase A as an example, the details are as follows. When the A-phase high voltage is excited, the A-phase current is increased rapidly by opening S7 and S3 to excite the A-phase. When the A-phase low-voltage excitation is performed, S7 is turned off, and the A-phase is excited by opening S1 and S3. When the A-phase upper tube has zero-voltage freewheeling, by turning on S7 and turning on D3, the A-phase current is reduced by the zero-voltage freewheeling. When the A-phase lower tube has zero-voltage freewheeling, by turning on S3 and conducting D1, the A-phase current is reduced by the zero-voltage freewheeling. When the A-phase negative high-voltage freewheeling current, the A-phase current quickly takes effect to zero by turning on D1 and D3.

At the same time, the detection of four-phase current can be realized through two Hall current sensors L1 and L2. In order to effectively illustrate the phase current detection process, first, when the rotor position is between the turn-on angle and the turn-off angle, it is defined as the conduction interval; when the rotor position is outside the conduction interval and the phase current is not zero, it is defined as turn-off interval. The process of current detection is divided into two cases, the first is the single-phase working mode, only one phase has current at the same time; the second is the two-phase working mode, there are two phases with current at the synonymous moment. When it is a single-phase working mode, taking A-phase as an example, when the rotor position is in the A-phase on-interval and off-interval, the A-phase current (i _a ) is in the high-voltage excitation mode, low-voltage excitation mode, and zero-voltage continuous. In the current mode, the zero-voltage freewheeling mode and the negative high-voltage freewheeling mode, only L1 is passed, and the specific value is shown in formula (1).

i _a = i _L1 (1)

In the formula (1), i _L1 is the measured value of the Hall current sensor L1.

When it is in two-phase working mode, take the conduction when phase A and B are the same as an example. At this time, the current of phase A (i _a ) is in high voltage excitation mode, low voltage excitation mode, upper zero voltage freewheeling mode, and lower zero voltage freewheeling mode. Mode and negative high voltage freewheeling mode only pass through L1, B-phase current (i _b ) in high voltage excitation mode, low voltage excitation mode, upper zero voltage freewheeling mode, lower zero voltage freewheeling mode and negative high voltage freewheeling mode. Only through L2, so the specific values of i _a and i _b are shown in formula (2).

The proposed control strategy includes a speed control loop, a current control loop, and a capacitor-voltage control loop. Both the current control loop and the voltage control loop adopt hysteresis control, and the reference current is output through the speed control. The current input current hysteresis controller outputs the drive signal of each phase; the high-level signal of the drive signal of each phase selects high-voltage excitation and low-voltage excitation through the output of the voltage loop, and the high-voltage excitation mode is used to step down to prevent the capacitor voltage from overshooting. High and low voltage excitation can ensure that the capacitor voltage remains unchanged and achieve rapid demagnetization; the capacitor is charged by the demagnetization energy to achieve voltage pumping; when the drive signal of each phase is at a low level, use the three-dimensional thermal circuit model or the measured power of each power device. The upper zero voltage freewheeling mode or the lower zero voltage freewheeling mode is determined according to the temperature. If the temperature of S7 is greater than that of S3 and S4, the upper zero voltage freewheeling mode is selected, otherwise, the lower zero voltage freewheeling mode is selected, thereby improving the reliability of the system.

The proposed converter can improve the fault tolerance of the system. Since the proposed power converter has two working modes, high-voltage excitation and low-voltage excitation, the mutual conversion between low-voltage excitation and high-voltage excitation can ensure that each phase winding is in the controllable switch tube S1. , S2, S7 or S8 open circuit to ensure the normal operation of the system and improve the fault tolerance of the system. For example, when S1 is open, in order to ensure the excitation of A-phase, S7 can be opened to ensure the normal excitation of A-phase.

The beneficial effects of the present invention are: the low-cost self-boosting power converter topology proposed by the present invention can reduce the number of components used and the system cost, and improve the response speed, long-distance efficiency and reliability.

Description of drawings

FIG. 1 is a topology structure diagram of a low-cost self-boost power converter according to Embodiment 1 of the present invention.

FIG. 2 is a schematic diagram of a current path in a high-voltage excitation mode according to Embodiment 1 of the present invention.

3 is a schematic diagram of a current path in a low-voltage excitation mode according to Embodiment 1 of the present invention.

4 is a schematic diagram of a current path in a zero-voltage freewheeling mode of an upper tube according to Embodiment 1 of the present invention.

5 is a schematic diagram of a current path in a zero-voltage freewheeling mode of a lower tube according to Embodiment 1 of the present invention.

6 is a schematic diagram of a current path in a negative high-voltage freewheeling mode according to Embodiment 1 of the present invention.

Detailed ways

The following describes in detail the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary, and are intended to explain the present invention and should not be construed as limiting the present invention.

The following describes an enhanced Miller power converter for a switched reluctance motor according to an embodiment of the present invention with reference to the accompanying drawings.

FIG. 1 is a low-cost self-boost power converter for a four-phase switched reluctance motor according to an embodiment of the present invention. As shown in FIG. 1 , the low-cost self-boosting power converter for a four-phase switched reluctance motor according to an embodiment of the present invention includes: a DC power supply unit, an energy storage capacitor, 8 controllable switch tubes, 6 diodes and 2 It consists of two Hall current sensors; the DC power supply unit can be connected to a battery or a switching power supply; the cathode of the energy storage capacitor is connected to the anode of the DC power supply, the drains of the controllable switches S1 and S2, and the source of S1 is connected to the cathode of the diode D1, S7 The source of the capacitor is connected to the positive pole of the A-phase and C-phase windings, the source of S2 is connected to the cathode of the diode D2, the source of S8 and the positive pole of the B-phase and D-phase windings, and the anode of the energy storage capacitor is connected to the diodes D3, D4, D5 It is connected with the cathode of D6 and the drains of the controllable switches S7 and S8, and the cathode of the power supply is connected with the anode of the diode D1, the anode of D2, the source of the controllable switch S3, the source of S4, the source of S5 and the source of S6, and the controllable The drain of switch tube S3 is connected to the anode of diode D3 and the negative pole of phase A winding, the drain of controllable switch tube S4 is connected to the anode of diode D4 and the negative pole of phase C winding, the drain of controllable switch tube S5 is connected to the anode of diode D5 and the negative pole of phase B winding The drain of the controllable switch tube S6 is connected to the anode of the diode D6 and the negative electrode of the D-phase winding; the Hall current sensor L1 is used to measure the A-phase and C-phase currents, and the Hall current sensor L2 is used to measure the B-phase and D-phase currents; Among them, the controllable switch tube is a commonly used MOSFET or IGBT.

Description of working principle: The proposed converter has five working modes: high-voltage excitation mode, low-voltage excitation mode, upper-tube zero-voltage freewheeling mode, lower-tube zero-voltage freewheeling mode and negative high-voltage freewheeling mode. Taking phase A as an example, the details are as follows. When A-phase high-voltage excitation, by opening S7 and S3 to A-phase excitation, the A-phase current increases rapidly, as shown in Figure 2. When A-phase low-voltage excitation, turn off S7, and activate the A-phase by opening S1 and S3, as shown in Figure 3. When the A-phase upper tube has zero-voltage freewheeling, turn on S7 and turn on D3 to reduce the A-phase current through the zero-voltage freewheeling, as shown in Figure 4. When the A-phase lower tube has zero-voltage freewheeling, by turning on S3 and turning on D1, the A-phase current is reduced by the zero-voltage freewheeling, as shown in Figure 5. When the A-phase negative high-voltage freewheeling current, the A-phase current quickly takes effect to zero by turning on D1 and D3, as shown in Figure 6.

At the same time, the detection of four-phase current can be realized through two Hall current sensors L1 and L2. In order to effectively illustrate the phase current detection process, first, when the rotor position is between the turn-on angle and the turn-off angle, it is defined as the conduction interval; when the rotor position is outside the conduction interval and the phase current is not zero, it is defined as turn-off interval. The process of current detection is divided into two situations, the first is single-phase working mode, only one phase has current at the same time; the second is two-phase working mode, two phases have current at synonymous moment. When it is a single-phase working mode, taking A-phase as an example, when the rotor position is in the A-phase conduction interval and the turn-off interval, the A-phase phase current (i _a ) is in the high-voltage excitation mode, the low-voltage excitation mode, and the zero-voltage continuous In the current mode, the zero-voltage freewheeling mode and the negative high-voltage freewheeling mode, only L1 is passed, and the specific value is shown in formula (1).

i _a = i _L1 (1)

In the formula (1), i _L1 is the measured value of the Hall current sensor L1.

When it is in two-phase working mode, take the conduction when phase A and B are the same as an example. At this time, the current of phase A (i _a ) is in high voltage excitation mode, low voltage excitation mode, upper zero voltage freewheeling mode, and lower zero voltage freewheeling mode. Mode and negative high voltage freewheeling mode only pass through L1, B-phase current (i _b ) in high voltage excitation mode, low voltage excitation mode, upper zero voltage freewheeling mode, lower zero voltage freewheeling mode and negative high voltage freewheeling mode. Only through L2, so the specific values of i _a and i _b are shown in formula (2).

The proposed control strategy includes a speed control loop, a current control loop, and a capacitor-voltage control loop. Both the current control loop and the voltage control loop adopt hysteresis control, and the reference current is output through the speed control. The current input current hysteresis controller outputs the drive signal of each phase; the high-level signal of the drive signal of each phase selects high-voltage excitation and low-voltage excitation through the output of the voltage loop, and the high-voltage excitation mode is used to step down to prevent the capacitor voltage from overshooting. High and low voltage excitation can ensure that the capacitor voltage remains unchanged and achieve rapid demagnetization; the capacitor is charged by the demagnetization energy to achieve voltage pumping; when the drive signal of each phase is at a low level, use the three-dimensional thermal circuit model or the measured power of each power device. The upper zero voltage freewheeling mode or the lower zero voltage freewheeling mode is determined according to the temperature. If the temperature of S7 is greater than that of S3 and S4, the upper zero voltage freewheeling mode is selected, otherwise, the lower zero voltage freewheeling mode is selected, thereby improving the reliability of the system.

The proposed converter can improve the fault tolerance of the system. Since the proposed power converter has two working modes, high-voltage excitation and low-voltage excitation, the mutual conversion between low-voltage excitation and high-voltage excitation can ensure that each phase winding is in the controllable switch tube S1. , S2, S7 or S8 open circuit to ensure the normal operation of the system and improve the fault tolerance of the system. For example, when S1 is open, in order to ensure the excitation of A-phase, S7 can be opened to ensure the normal excitation of A-phase.

Although the embodiments of the present invention have been shown and described above, it should be understood that the above-mentioned embodiments are exemplary and should not be construed as limiting the present invention. Embodiments are subject to variations, modifications, substitutions and variations.

Claims (4)

1. A low-cost self-boosting power converter for a switched reluctance motor and a control strategy thereof are characterized in that: the low-cost self-boosting power converter consists of a direct-current power supply unit, an energy storage capacitor, 8 controllable switching tubes, 6 diodes and 2 Hall current sensors; the direct-current power supply unit can be connected with a storage battery or a switching power supply; the cathode of the energy storage capacitor is connected with the anode of a direct current power supply and the drains of controllable switch tubes S1 and S2, the source of S1 is connected with the cathode of a diode D1 and the source of S7 and the anodes of A-phase and C-phase windings, the source of S2 is connected with the cathode of a diode D2 and the source of S8 and the anodes of B-phase and D-phase windings, the anode of the energy storage capacitor is connected with the cathodes of diodes D3, D4, D5 and D6 and the drains of controllable switch tubes S7 and S8, the cathode of the power supply is connected with the anode of a diode D1 and the anode of D2, the source of the controllable switch tube S3 and the source of S4, the source of S5 and the source of S6, the drain electrode of the controllable switch tube S3 is connected with the anode of the diode D3 and the cathode of the A-phase winding, the drain electrode of the controllable switch tube S4 is connected with the anode of the diode D4 and the cathode of the C-phase winding, the drain electrode of the controllable switch tube S5 is connected with the anode of the diode D5 and the cathode of the phase B winding, and the drain electrode of the controllable switch tube S6 is connected with the anode of the diode D6 and the cathode of the phase D winding; a hall current sensor L1 for measuring a-phase and C-phase currents, and a hall current sensor L2 for measuring a B-phase and D-phase currents; the controllable switch tube is a common MOSFET or IGBT.

2. The converter has five working modes, namely a high-voltage excitation mode, a low-voltage excitation mode, an upper tube zero-voltage follow current mode, a lower tube zero-voltage follow current mode and a negative high-voltage follow current mode, can realize real-time monitoring of four-phase current through the two Hall current sensors, and effectively reduces the using number of the current sensors.

3. The provided control strategy comprises a rotating speed control loop, a current control loop and a capacitance voltage control loop, wherein the current control loop and the voltage control loop are controlled by hysteresis loops, reference current is output by rotating speed control, and the reference current and current of each phase measured by two current sensors are input into a current hysteresis controller to output driving signals of each phase; high-level signals of driving signals of all phases select high-voltage excitation and low-voltage excitation through the output of a voltage ring, the high-voltage excitation mode is used for reducing voltage, the voltage of a capacitor is prevented from being overhigh, the low-voltage excitation can ensure that the voltage of the capacitor is unchanged, and the rapid demagnetization is realized; the capacitor is charged by demagnetized energy, so that pumping of voltage is realized; when each phase of driving signals are at a low level, the three-dimensional thermal circuit model or the actually measured temperature of each power device is used for determining the upper zero voltage follow current mode or the lower zero voltage follow current mode, if the temperature of S7 is greater than S3 and S4, the upper zero voltage follow current mode is selected, and if not, the lower zero voltage follow current mode is selected, so that the reliability of the system is improved.

4. The converter can improve the fault-tolerant capability of the system, and the power converter has two working modes of high-voltage excitation and low-voltage excitation, so that the normal operation of each phase winding when the controllable switching tubes S1, S2, S7 or S8 are open-circuited can be ensured through the mutual conversion of the low-voltage excitation and the high-voltage excitation, and the fault-tolerant capability of the system is improved.

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