THREE-PHASE SWITCHED RELUCTANCE MOTOR TORQUE RIPPLE TWO-LEVEL SUPPRESSION METHOD

Abstract

A three-phase switched reluctance motor torque ripple two-level suppression method is disclosed. A first set of torque thresholds is set in rotor position interval [0°, θ.sub.r/3]. A second set of torque thresholds is set in rotor position interval [θ.sub.r/3, θ.sub.r/2]. Power is supplied to adjacent phase A and phase B for excitation. The power supplied for excitation to phase A leads the power supplied for excitation to phase B by θ.sub.r/3. Phase A is turned off while phase B is turned on. An entire commutation process from phase A to phase B is divided into two intervals. In rotor position interval [0°, θ.sub.1], phase A uses the second set of torque thresholds while phase B uses the first set of torque thresholds. Critical position θ.sub.1 automatically appears in the commutation process, thus obviating the need for additional calculations. Total torque is controlled between [T.sub.e+th2.sub.low and T.sub.e+th2.sub.up]. In rotor position interval [θ.sub.1, θ.sub.r/3], phase A continues to use the second set of torque thresholds, phase B continues to use the first set of torque thresholds, and the total torque is controlled between [T.sub.e+th1.sub.low and T.sub.e+th1.sub.up]. This suppresses torque ripples of a three-phase switched reluctance motor.

Claims

1. A method for two-level suppression of torque ripple of three-phase switched reluctance motor, wherein, the method comprises the following steps: a. setting the first group of torque thresholds (th1.sub.low, th1.sub.up) in rotor position interval [0°, θ.sub.r/3], and the second group of torque thresholds (th2.sub.low, th2.sub.up) in rotor position interval [θ.sub.r/3, θ.sub.r/2], wherein these four torque thresholds meet the following conditions:
th1.sub.up>th2.sub.up>0   (1)
th2.sub.low<th1.sub.low<0   (2)
|th1.sub.up|=|th2.sub.low|  (3)
|th2.sub.up|=|th1.sub.low|  (4) wherein, rotor position 0° is minimum phase inductance position, rotor position θ.sub.r is angular pitch, i.e., one rotor cycle, and a half rotor cycle is θ.sub.r/2; b. setting excited state S.sub.A as excited state of phase A power supply, wherein excited state S.sub.A=1 means the exciting voltage of phase A power supply is positive and excited state S.sub.A=−1 means the exciting voltage of phase A power supply is negative; setting excited state S.sub.B as excited state of phase B power supply, wherein excited state S.sub.B=1 means the exciting voltage of phase B power supply is positive and excited state S.sub.B=−1 means the exciting voltage of phase B power supply is negative, and the expected total smooth torque is T.sub.e; c. for adjacent phase A and phase B power supply excitations, phase A power supply excitation is θ.sub.r/3 ahead of phase B power supply excitation; at this moment, phase A is turn off, phase B is turn on, and two-level suppression of torque ripple of three-phase switched reluctance motor is realized by a two-interval commutation process from phase A to phase B.

2. The method for two-level suppression of torque ripple of three-phase switched reluctance motor according to claim 1, wherein the two-interval commutation process from phase A to phase B is as follows: (1) in rotor position interval [0°, θ.sub.1], phase A uses the second group of torque thresholds (th2.sub.low, th2.sub.up), phase B uses the first group of torque thresholds (th1.sub.low, th1.sub.up), critical position θ.sub.1 appears automatically in the commutation process, and no extra calculation is needed; (1.1) Phase B conduction cycle is entered in rotor position 0°, initial excited state S.sub.B=1 is set, and phase B current and torque increase from 0; excited state S.sub.A maintains original state S.sub.A=−1, and phase A current and torque decrease; as the inductance change rate and current of phase B in this position are relatively small, the increase rate of phase B torque is smaller than the decrease rate of phase A torque and total torque decreases along with phase A; (1.2) when total torque first reaches torque value T.sub.e+th1.sub.low, phase A and phase B state transfer conditions are not met, excited states S.sub.A and S.sub.B maintain original states and total torque continues to decrease; (1.3) when total torque decreases to torque value T.sub.e+th2.sub.low, phase A state transfer conditions are met, excited state S.sub.A is switched from −1 to 1 and phase A torque increases; phase B maintains original state and phase B torque continues to increase, thereby total torque increases; (1.4) when total torque increases to torque value T.sub.e+th1.sub.low, phase A and phase B state transfer conditions are not met, excited states S.sub.A and S.sub.B maintain original states and total torque continues to increase; (1.5) when total torque increases to torque value T.sub.e+th2.sub.up, phase A state transfer conditions are met, excited state S.sub.A is switched from 1 to −1 and phase A torque decreases; but phase B state transfer conditions are not met, excited state S.sub.B maintains original state and total torque begins to decrease; (1.6) steps (1.2)˜(1.5) are repeated, excited state S.sub.B maintains state 1 all the time, i.e., phase B is excited by positive voltage, and the current and torque of phase B increase at a maximum rate; excited state S.sub.A is switched between −1 and 1 and total torque is controlled in [T.sub.e+th2.sub.low, T.sub.e+th2.sub.up] all the time, thereby inhibiting ripple of three-phase switched reluctance motor torque in rotor position interval [0°, θ.sub.1]; (2) in rotor position interval [θ.sub.1, θ.sub.r/3], phase A continues to use the second group of torque thresholds (th2.sub.low, th2.sub.up) and phase B continues to use the first group of torque thresholds (th1.sub.low, th1.sub.up); (2.1) in rotor position θ.sub.1, the inductance change rate and phase current of phase B have reached a certain level; when excited state S.sub.B=1 and excited state S.sub.A=−1, the increase rate of phase B torque is no longer smaller than the decrease rate of phase A torque, the change trend of total torque is decided by phase B and total torque increases; (2.2) when total torque increases to torque value T.sub.e+th1.sub.up, phase B state transfer conditions are met, excited state S.sub.B is converted from 1 to −1 and phase B torque decreases; excited state S.sub.A maintains state −1 and total torque decreases; (2.3) when total torque first decreases to torque value T.sub.e+th2.sub.up, phase A and phase B state transfer conditions are not met, excited states S.sub.A and S.sub.B maintain original states and total torque continues to decrease; (2.4) when total torque decreases to torque value T.sub.e+th1.sub.low, phase B state transfer conditions are met, excited state S.sub.B is converted from −1 to 1 and phase B torque increases; excited state S.sub.A maintains state −1 and total torque increases along with phase B torque; (2.5) when total torque increases to torque value T.sub.e+th2.sub.up, phase A and phase B state transfer conditions are not met, excited states S.sub.A and S.sub.B maintain original states and total torque continues to increase; (2.6) when total torque increases to torque value T.sub.e+th1.sub.up, steps (2.2)˜(2.5) are repeated, excited state S.sub.A maintains state −1, excited state S.sub.B is switched between −1 and 1 and total torque is controlled in [T.sub.e+th1.sub.low, T.sub.e+th1.sub.up], thereby inhibiting ripple of three-phase switched reluctance motor torque in rotor position interval [θ.sub.1, θ.sub.r/3].

3. A method for two-level suppression of torque ripple of a three-phase switched reluctance motor, the method comprising: setting a first group of torque thresholds (th1.sub.low, th1.sub.up) in rotor position interval [0°, θ.sub.r/3], and setting a second group of torque thresholds (th2.sub.low, th2.sub.up) in rotor position interval [θ.sub.r/3, θ.sub.r/2], wherein the four torque thresholds are:
th1.sub.up>th2.sub.up>0   (1)
th2.sub.low<th1.sub.low<0   (2)
|th1.sub.up|=|th2.sub.low|  (3)
|th2.sub.up|=|th1.sub.low|  (4) wherein, rotor position 0° is minimum phase inductance position, rotor position θ.sub.r is angular pitch, and a half rotor cycle is θ.sub.r/2; setting excited state S.sub.A as the excited state of phase A power supply, wherein excited state S.sub.A=1 is when the exciting voltage of phase A power supply is positive and excited state S.sub.A=−1 is when the exciting voltage of phase A power supply is negative; setting excited state S.sub.B as the excited state of phase B power supply, wherein excited state S.sub.B=1 is when the exciting voltage of phase B power supply is positive and excited state S.sub.B=−1 is when the exciting voltage of phase B power supply is negative, and the expected total smooth torque is T.sub.e; and for adjacent phase A and phase B power supply excitations, phase A power supply excitation is θ.sub.r/3 ahead of phase B power supply excitation; at this moment, turning on phase A, turning on phase B, wherein two-level suppression of torque ripple of the three-phase switched reluctance motor is realized by a two-interval commutation process from phase A to phase B.

4. The method according to claim 3, wherein the two-interval commutation process from phase A to phase B, wherein: (1) in rotor position interval [0°, θ.sub.1], phase A utilizes the second group of torque thresholds (th2.sub.low, th2.sub.up), phase B utilizes the first group of torque thresholds (th1.sub.low, th1.sub.up), critical position θ.sub.1 appears automatically in the commutation process, and no extra calculation is needed; (1.1) Phase B conduction cycle is entered in rotor position 0°, initial excited state S.sub.B=1 is set, and phase B current and torque increase from 0; excited state S.sub.A maintains original state S.sub.A=−1, and phase A current and torque decrease; as the inductance change rate and current of phase B in this position are relatively small, the increase rate of phase B torque is smaller than the decrease rate of phase A torque and total torque decreases along with phase A; (1.2) when total torque first reaches torque value T.sub.e+th1.sub.low, phase A and phase B state transfer conditions are not met, excited states S.sub.A and S.sub.B maintain original states and total torque continues to decrease; (1.3) when total torque decreases to torque value T.sub.e+th2.sub.low, phase A state transfer conditions are met, excited state S.sub.A is switched from −1 to 1 and phase A torque increases; phase B maintains original state and phase B torque continues to increase, thereby total torque increases; (1.4) when total torque increases to torque value T.sub.e+th1.sub.low, phase A and phase B state transfer conditions are not met, excited states S.sub.A and S.sub.B maintain original states and total torque continues to increase; (1.5) when total torque increases to torque value T.sub.e+th2.sub.up, phase A state transfer conditions are met, excited state S.sub.A is switched from 1 to −1 and phase A torque decreases; but phase B state transfer conditions are not met, excited state S.sub.B maintains original state and total torque begins to decrease; (1.6) repeating steps (1.2)˜(1.5), excited state S.sub.B maintains state 1 all of the time, and the current and torque of phase B increase at a maximum rate; excited state S.sub.A is switched between −1 and 1 and total torque is controlled in [T.sub.e+th2.sub.low, T.sub.e+th2.sub.up] all of the time, thereby inhibiting ripple of three-phase switched reluctance motor torque in rotor position interval [0°, θ.sub.1]; (2) in rotor position interval [θ.sub.1, θ.sub.r/3], phase A continues to utilize the second group of torque thresholds (th2.sub.low, th2.sub.up) and phase B continues to utilize the first group of torque thresholds (th1.sub.low, th1.sub.up); (2.1) in rotor position θ.sub.1, the inductance change rate and phase current of phase B reach a certain level; when excited state S.sub.B=1 and excited state S.sub.A=−1, the increase rate of phase B torque is no longer less than the decrease rate of phase A torque, the change trend of total torque is determined by phase B and total torque increases; (2.2) when total torque increases to torque value T.sub.e+th1.sub.up, phase B state transfer conditions are met, excited state S.sub.B is converted from 1 to −1 and phase B torque decreases; excited state S.sub.A maintains state −1 and total torque decreases; (2.3) when total torque first decreases to torque value T.sub.e+th2.sub.up, phase A and phase B state transfer conditions are not met, excited states S.sub.A and S.sub.B maintain original states and total torque continues to decrease; (2.4) when total torque decreases to torque value T.sub.e+th1.sub.low, phase B state transfer conditions are met, excited state S.sub.B is converted from −1 to 1 and phase B torque increases; excited state S.sub.A maintains state −1 and total torque increases along with phase B torque; (2.5) when total torque increases to torque value T.sub.e+th2.sub.up, phase A and phase B state transfer conditions are not met, excited states S.sub.A and S.sub.B maintain original states and total torque continues to increase; and (2.6) when total torque increases to torque value T.sub.e+th1.sub.up, steps (2.2)˜(2.5) are repeated, excited state S.sub.A maintains state −1, excited state S.sub.B is switched between −1 and 1 and total torque is controlled in [T.sub.e+th1.sub.low, T.sub.e+th1.sub.up], thereby inhibiting ripple of the three-phase switched reluctance motor torque in rotor position interval [θ.sub.1, θ.sub.r/3].

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 is a schematic diagram for setting of two-level torque thresholds of switched reluctance motor provided by this disclosure;

[0027] FIG. 2A is a schematic diagram for conversion of excited state of phase B power supply of switched reluctance motor provided by this disclosure;

[0028] FIG. 2B is a schematic diagram for conversion of excited state of phase A power supply of switched reluctance motor provided by this disclosure; and

[0029] FIG. 3 is torque waveform of switched reluctance motor provided by this disclosure.

DETAILED DESCRIPTION

[0030] This disclosure is further described below in connection with the examples shown in the accompanying drawings:

[0031] a. As shown in FIG. 1, for one three-phase switched reluctance motor, setting the first group of torque thresholds (th1.sub.low, th1.sub.up) in rotor position interval [0°, θ.sub.r/3], and the second group of torque thresholds (th2.sub.low, th2.sub.up) in rotor position interval [θ.sub.r/3, θ.sub.r/2], wherein these four torque thresholds meet the following conditions:

th1.sub.up>th2.sub.up>0   (1)

th2.sub.low<th1.sub.low<0   (2)

|th1.sub.up|=|th2.sub.low|  (3)

|th2.sub.up|=|th1.sub.low|  (4)

wherein, rotor position 0° is minimum phase inductance position, rotor position θ.sub.r is angular pitch, i.e., one rotor cycle, and a half rotor cycle is θ.sub.r/2;

[0032] b. As shown in FIGS. 2A and 2B, setting excited state S.sub.A as excited state of phase A power supply, wherein excited state S.sub.A=1 means the exciting voltage of phase A power supply is positive and excited state S.sub.A=−1 means the exciting voltage of phase A power supply is negative; setting excited state S.sub.B as excited state of phase B power supply, wherein excited state S.sub.B=1 means the exciting voltage of phase B power supply is positive and excited state S.sub.B=−1 means the exciting voltage of phase B power supply is negative, and the expected total smooth torque is T.sub.e;

[0033] c. For adjacent phase A and phase B power supply excitations, phase A power supply excitation is θ.sub.r/3 ahead of phase B power supply excitation. At this moment, phase A is turn off and phase B is turn on. As shown in FIG. 1, the commutation process from phase A to phase B is divided into two intervals: [0034] (1) In rotor position interval [0°, θ.sub.1], phase A uses the second group of torque thresholds (th2.sub.low, th2.sub.up), phase B uses the first group of torque thresholds (th1.sub.low, th1.sub.up), critical position θ.sub.1 appears automatically in the commutation process, and no extra calculation is needed; [0035] (1.1) Phase B conduction cycle is entered in rotor position 0°, initial excited state S.sub.B=1 is set, and phase B current and torque increase from 0; excited state S.sub.A maintains original state S.sub.A=−1, and phase A current and torque decrease; as the inductance change rate and current of phase B in this position are relatively small, the increase rate of phase B torque is smaller than the decrease rate of phase A torque and total torque decreases along with phase A; [0036] (1.2) When total torque first reaches torque value T.sub.e+th1.sub.low, phase A and phase B state transfer conditions are not met, excited states S.sub.A and S.sub.B maintain original states and total torque continues to decrease; [0037] (1.3) When total torque decreases to torque value T.sub.e+th2.sub.low, phase A state transfer conditions are met, excited state S.sub.A is switched from −1 to 1 and phase A torque increases; phase B maintains original state and phase B torque continues to increase, thereby total torque increases; [0038] (1.4) When total torque increases to torque value T.sub.e+th1.sub.low, phase A and phase B state transfer conditions are not met, excited states S.sub.A and S.sub.B maintain original states and total torque continues to increase; [0039] (1.5) When total torque increases to torque value T.sub.e+th2.sub.up, phase A state transfer conditions are met, excited state S.sub.A is switched from 1 to −1 and phase A torque decreases; but phase B state transfer conditions are not met, excited state S.sub.B maintains original state and total torque begins to decrease; [0040] (1.6) Steps (1.2)˜(1.5) are repeated, excited state S.sub.B maintains state 1 all the time, i.e., phase B is excited by positive voltage, and the current and torque of phase B increase at a maximum rate; excited state S.sub.A is switched between −1 and 1 and total torque is controlled in [T.sub.e+th2.sub.low, T.sub.e+th2.sub.up] all the time, thereby inhibiting ripple of three-phase switched reluctance motor torque in rotor position interval [0°, θ.sub.1]; [0041] (2) In rotor position interval [θ.sub.1, θ.sub.r/3], phase A continues to use the second group of torque thresholds (th2.sub.low, th2.sub.up) and phase B continues to use the first group of torque thresholds (th1.sub.low, th1.sub.up); [0042] (2.1) In rotor position θ.sub.1, the inductance change rate and phase current of phase B have reached a certain level. When excited state S.sub.B=1 and excited state S.sub.A=−1, the increase rate of phase B torque is no longer smaller than the decrease rate of phase A torque, the change trend of total torque is decided by phase B and total torque increases; [0043] (2.2) When total torque increases to torque value T.sub.e+th1.sub.up, phase B state transfer conditions are met, excited state S.sub.B is converted from 1 to −1 and phase B torque decreases; excited state S.sub.A maintains state −1 and total torque decreases; [0044] (2.3) When total torque first decreases to torque value T.sub.e+th2.sub.up, phase A and phase B state transfer conditions are not met, excited states S.sub.A and S.sub.B maintain original states and total torque continues to decrease; [0045] (2.4) When total torque decreases to torque value T.sub.e+th1.sub.low, phase B state transfer conditions are met, excited state S.sub.B is converted from −1 to 1 and phase B torque increases; excited state S.sub.A maintains state −1 and total torque increases along with phase B torque; [0046] (2.5) When total torque increases to torque value T.sub.e+th2.sub.up, phase A and phase B state transfer conditions are not met, excited states S.sub.A and S.sub.B maintain original states and total torque continues to increase; [0047] (2.6) When total torque increases to torque value T.sub.e+th1.sub.up, Steps (2.2)˜(2.5) are repeated, excited state S.sub.A maintains state −1, excited state S.sub.B is switched between −1 and 1 and total torque is controlled in [T.sub.e+th1.sub.low, T.sub.e+th1.sub.up], thereby inhibiting ripple of three-phase switched reluctance motor torque in rotor position interval [θ.sub.1, θ.sub.r/3].

[0048] For adjacent phase B and phase C power supply excitations, when phase B power supply excitation is θ.sub.r/3 ahead of phase C power supply excitation, torque threshold setting, commutation process, and phase B and phase C excited state switching and transfer methods are similar to the foregoing circumstance. For adjacent phase C and phase A power supply excitations, when phase C power supply excitation is θ.sub.r/3 ahead of phase A power supply excitation, torque threshold setting, commutation process, and phase C and phase A excited state switching and transfer methods are similar to the foregoing circumstance. The acquired switched reluctance motor torque waveform is as shown in FIG. 3.