A flux linkage effect modulation method for specific harmonic current closed-loop control of an electrically excited doubly salient motor

Abstract

The application discloses a flux superposition effect modulation method for specific harmonic current closed-loop control of an electrically excited doubly salient motor, and belongs to the field of motor drive control technology. In a multiplex excitation winding current source type electrically excited doubly salient motor drive control system, a specific order rotating coordinate system is set to extract harmonic current, a harmonic current closed-loop control loop is constructed, the flux superposition effect of the current source type inverter is modulated, specific order current harmonic current is generated, the inherent torque ripple of the electrically excited doubly salient motor under the sinusoidal wave driving mode is offset, and the output characteristics of the electrically excited doubly salient motor drive system are improved. The application can set the flux superposition time distribution of the current source type inverter in a closed loop, realize specific order current harmonic injection, eliminate the output torque ripple of the motor drive system, and avoid the influence caused by the flux superposition effect in the traditional current source type converter.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of motor control, and particularly relates to a flux linkage effect modulation method for specific harmonic current closed-loop control of an electrically excited doubly salient motor. BACKGROUND

[0002] With the vigorous development of new energy industry, higher requirements are put forward for the operation efficiency, control performance and reliability of the electric power transmission system taking the motor as the control object. Meanwhile, it is also important to reduce the cost of the driving motor while maintaining good motor performance. The electrically excited doubly salient motor has controllable excitation current, simple speed regulation advantage, and can be de-excited in time in case of failure, thus improving the reliability. Moreover, as it is an electrically excited motor, no permanent magnet is needed, thus greatly reducing the cost. In addition, the use of current source type inverter can multiplex the excitation winding of the electrically excited doubly salient motor as the energy storage inductance on the DC side of the current source type inverter, thus reducing the cost and improving the system power density. Therefore, the driving system of the electrically excited doubly salient motor based on the current source type inverter has broad application prospects. However, in the operation process of the electrically excited doubly salient motor, due to the structural design of the motor, even if the current source type inverter sinusoidal wave drive is used, the inherent torque ripple of the motor still exists, which brings about great vibration and noise. Therefore, it is of great significance to suppress the torque ripple by injecting harmonic current.

[0003] At present, the research on the suppression of torque ripple by harmonic injection mainly falls into two categories: 1) calculating the harmonic current according to the torque model, and injecting the harmonic from the outside; 2) generating the harmonic current according to the closed-loop control of the torque ripple, without the need to calculate the external injection of the harmonic. In most harmonic injection applications, the first method is usually adopted, that is, the given value of the external injection of the harmonic is calculated according to the relationship that the inherent torque ripple and the additional torque ripple generated by the harmonic current offset each other, and the harmonic injection is completed by adjusting the duty cycle in the control of the switching tube. This kind of method needs to observe the motor flux and back electromotive force in advance, so as to obtain the calculation model of the inherent torque ripple. In view of this problem, some scholars have proposed the second method. According to the proportional relationship between the speed ripple amplitude and the torque ripple amplitude, the given value of the injected harmonic is automatically generated by constructing the closed-loop control of the speed ripple.

[0004] However, in the driving system based on the current source type inverter, the flux linkage time needs to be set for the current source type inverter, and the error current generated by the flux linkage effect will affect the harmonic injection. When the external harmonic is injected, if the influence of the additional torque ripple introduced by the flux linkage effect is considered, then the given value of the injected harmonic current needs to be obtained according to the mutual offset of the three parts of the torque ripple, and the calculation process will be very complex.

[0005] Therefore, for the suppression of torque ripple of the electrically excited doubly salient motor driving system based on the current source type inverter, a harmonic injection method considering the reactance effect is urgently needed. SUMMARY

[0006] The application provides a reactance effect modulation method for specific harmonic current closed-loop control of an electrically excited doubly salient motor, realizes harmonic injection of the electrically excited doubly salient motor driving system, and eliminates inherent output torque ripple.

[0007] The application provides a reactance effect modulation method for specific harmonic current closed-loop control of an electrically excited doubly salient motor, realizes harmonic injection of the electrically excited doubly salient motor driving system, and eliminates inherent output torque ripple.

[0008] Step 1, according to the analysis of inherent torque ripple generated by the back electromotive force harmonic characteristics of the electrically excited doubly salient motor, the harmonic current given value i required for suppressing torque ripple is calculated d5th_ref , q5th_ref , d7th_ref , q7th_ref ;

[0009] Step 2, sampling the three-phase current i of the motor a , b , c , through five and seven times of synchronous rotating coordinate transformation, the signals i d5 , q5 , d7 , q7 are obtained, and then the low-pass filter is used to filter out the high-frequency items to extract the DC components, so as to obtain the feedback value i of the harmonic current control loop d5th , q5th , d7th , q7th ;

[0010] Step 3, the feedback value i d5th , q5th , d7th , q7th and the given value i d5th_ref , q5th_ref , d7th_ref , q7th_ref are input into the PI controller of the harmonic current control loop, and the output value is subjected to Clark transformation to obtain the injected harmonic current i in the alpha-beta coordinate system α5th , β5th , α7th , β7th , and the harmonic vector action time d1 and d2 are calculated.

[0011] Step 4, judging the three-phase capacitor voltage size, when the current vector is in sector II, IV, VI, the current commutation from the capacitor voltage low phase commutation to the capacitor voltage high phase, the low voltage phase corresponding switch tube conduction time is extended d1; the current commutation from the capacitor voltage high phase commutation to the capacitor voltage low phase, the high voltage phase corresponding switch tube conduction time is extended d2 When the current vector is in sector I, III, V, the current commutation from the capacitor voltage high phase commutation to the capacitor voltage low phase, the high voltage phase corresponding switch tube conduction time is extended d2; the current commutation from the capacitor voltage low phase commutation to the capacitor voltage high phase, the low voltage phase corresponding switch tube conduction time is extended d1

[0012]

[0013] Step 5, according to the switch tube conduction time extension setting in step 4, the switch tube switching time T is obtained according to the seven segment SVPWM modulation method cm1 cm2 cm3 cm4 cm5 cm6 , further through PWM to obtain switch tube drive signal S1-S6.

[0014] Further, in step 2, the motor three-phase current i a b c , after five, seven times of synchronous rotation coordinate transformation, the signals i d5 q5 d7 q7 , the electrically excited doubly salient phase current i a satisfy , i d5 q5 d7 q7 respectively:

[0015]

[0016] Wherein the first two terms are high frequency components with frequency of 6ωt, 12ωt respectively, the third term is a direct current component containing specific harmonic amplitude information, through a low-pass filter to filter out high frequency components, the remaining is the direct current feedback signal i d5th q5th d7th q7th of the harmonic current control loop.

[0017] ​​​​​​​​​​​​​​​​Further, in step 3, the harmonic vector acting time d1, d2 is calculated by referring to the calculation method of the non-zero vector acting time, and is calculated in different sectors, taking the original current vector located in sector I and the current vector after injection of the harmonic located in sector VI as an example, the harmonic vector acting time d1, d2 is:

[0018]

[0019] Wherein T s is the switching period, I dc is the DC side current of the current source type inverter.

[0020] Further, in step 4, when the current commutation is from a phase with high capacitor voltage to a phase with low capacitor voltage, the on time of the corresponding switch tube of the high voltage phase is prolonged When the current commutation is from a phase with low capacitor voltage to a phase with high capacitor voltage, the on time of the corresponding switch tube of the low voltage phase is prolonged Wherein T1, T2 are the non-zero vector acting time in SVPWM modulation.

[0021] Advantages: Compared with the prior art, the present application has the following remarkable advantages: the present application makes full use of the characteristics of the current source type inverter driving system, utilizes the superimposed current effect to generate the required harmonic current, solves the problem of complex calculation caused by the need to consider the superimposed current effect in the original external harmonic injection method; the superimposed current effect is modulated through a specific harmonic current closed loop to automatically generate the required harmonic current, so that the harmonic injection has higher accuracy, and the adaptability and robustness of the control system are improved. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a method flowchart of the present application.

[0023] Fig. 2(a) is a current vector synthesis diagram of the present application before and after injection of the harmonic.

[0024] Fig. 2(b) is a current vector synthesis diagram of the present application before and after injection of the harmonic.

[0025] Figure 3 It is a switching signal switching diagram in the case of sector I and u a > u b > u c in the present application.

[0026] Figure 4 It is a switching signal diagram of each sector in the present application.

[0027] Fig. 5(a) is a phase current waveform diagram before injection of the harmonic of the present application.

[0028] Figure 5(b) shows the Fourier analysis results of the phase current before the injection of harmonics in this invention.

[0029] Figure 6(a) shows the phase current waveform after the harmonics are injected according to the present invention.

[0030] Figure 6(b) shows the Fourier analysis results of the phase current after the injection of harmonics according to the present invention.

[0031] Figure 7(a) is a schematic diagram of the torque pulsation waveform before the injection of harmonics in this invention.

[0032] Figure 7(b) is a schematic diagram of the torque pulsation waveform after the injection of harmonics according to the present invention.

[0033] Figure 8(a) shows the torque pulsation waveform during the acceleration from 200 rpm to 400 rpm according to the present invention.

[0034] Figure 8(b) shows the torque pulsation waveform at 400 rpm according to the present invention. Detailed Implementation

[0035] like Figure 1 As shown, a method for modulating the superimposed current effect in closed-loop control of specific subharmonic currents of an electrically excited doubly salient pole motor includes the following steps:

[0036] S1: Based on the harmonic characteristics of the back EMF of an electrically excited doubly salient pole motor, the inherent torque ripple is analyzed, and the required harmonic current setpoint i to suppress the torque ripple is calculated. d5th_ref i q5th_ref i d7th_ref i q7th_ref .

[0037] S2: Sample motor three-phase current i a i b i c The signal i was obtained after five and seven synchronous rotational coordinate transformations, respectively. d5 i q5 i d7 i q7 The high-frequency terms are then filtered out by a low-pass filter to extract the DC component, yielding the feedback value i of the harmonic current control loop. d5th i q5th i d7th i q7th .

[0038] S3: Transfer the feedback value i d5th i q5th i d7th i q7th and given value i d5th_ref i q5th_ref i d7th_ref i q7th_refThe output value of the PI controller of the harmonic current control loop is Clark transformed to obtain the injected harmonic current i α5th β5th α7th β7th The harmonic vector acting time d1, d2 is calculated.

[0039] S4: judging the three-phase capacitor voltage size, when the current vector is located in sector II, IV, VI, the current commutation is from the low capacitor voltage phase to the high capacitor voltage phase, the corresponding switch tube conduction time of the low voltage phase is prolonged d1; when the current commutation is from the high capacitor voltage phase to the low capacitor voltage phase, the corresponding switch tube conduction time of the high voltage phase is prolonged When the current vector is located in sector I, III, V, the current commutation is from the low capacitor voltage phase to the high capacitor voltage phase, the corresponding switch tube conduction time of the low voltage phase is prolonged d2; when the current commutation is from the high capacitor voltage phase to the low capacitor voltage phase, the corresponding switch tube conduction time of the high voltage phase is prolonged

[0040] S5: according to the setting of the switch tube conduction time prolongation in step S4, the switch tube switching time T is obtained according to the modulation method of seven-segment SVPWM cm1 cm2 cm3 cm4 cm5 cm6 Further, the switch tube driving signals S1-S6 are obtained through PWM.

[0041] In step S2, the three-phase current i a b c

[0042]

[0043] The five and seven times synchronous rotating coordinate transformation matrix is:

[0044]

[0045] The signal i d5 q5 d7 q7

[0046]

[0047] The harmonic current control loop feedback signal i obtained through the low-pass filter​​​​​​​​​​​​​​​d5th i q5th i d7th i q7th for:

[0048]

[0049] As shown in Figure 2(a), when the actual current vector after harmonic injection is located in the same sector as the original current vector, in step S3, the output value of the harmonic current control loop is subjected to Clark transformation to obtain the injected harmonic current i in the α-β coordinate system. α5th i β5th i α7th i β7th The harmonic current vector it introduces is:

[0050]

[0051] Transforming it to the α-β coordinate system, we get:

[0052]

[0053] Therefore, the harmonic vector action times d1 and d2 under this condition are:

[0054]

[0055] As shown in Figure 2(b), when the actual current vector after harmonic injection is located in a different sector from the original current vector, the output value of the harmonic current control loop is subjected to Clark transformation in step S3 to obtain the injected harmonic current i in the α-β coordinate system. α5th i β5th i α7th i β7th The harmonic current vector it introduces is:

[0056]

[0057] Transforming it to the α-β coordinate system, we get:

[0058]

[0059] Therefore, the harmonic vector action times d1 and d2 under this condition are:

[0060]

[0061] Therefore, based on the actual current vector for sector determination, the harmonic vector action times d1 and d2 of each sector are shown in Table 1:

[0062] Table 1. Duration of Harmonic Vector Action in Each Sector

[0063]

[0064] wherein,

[0065] As Figure 3 shown, according to the setting of the extension of the switch tube conduction time in step S4, the harmonic current vector will make the corresponding current vector action time extend d1, d2, respectively, and then the conduction time of S4 is shortened by d1+d2. In the first half of the switching period, S4 needs to be turned off in advance and turned on in delay . Correspondingly, S6 needs to be turned on in advance d1 in the first half of the switching period, and S2 needs to be turned off in delay d2; then when S6 switches to S2, S2 needs to be turned on in advance . The second half of the switching period is set symmetrically accordingly.

[0066] As Figure 4 shown, in step S5, the switching time T cm1 , T cm2 , T cm3 , T cm4 , T cm5 , T cm6 of the switch obtained according to the modulation method of seven-segment SVPWM is as follows:

[0067] Table 2 Switching point setting of current sector I

[0068]

[0069] Table 3 Switching point setting of current sector II

[0070]

[0071]

[0072] Table 4 Switching point setting of current sector III

[0073]

[0074] Table 5 Switching point setting of current sector IV

[0075]

[0076]

[0077] Table 6 Switching point setting of current sector V

[0078]

[0079]

[0080] Table 7 Current sector VI switch switching point setting

[0081]

[0082] Wherein, T a , T b , T c Switching points in seven segment SVPWM modulation.

[0083] Finally, the driving signals S1-S6 of the switch tubes are obtained through PWM.

[0084] Compared with the existing harmonic injection method, the flux superposition effect modulation method of the specific harmonic current closed loop of the above-mentioned electrically excited doubly salient motor fully utilizes the characteristics of the current source type inverter driving system, generates the required harmonic current through the flux superposition effect, solves the problem that the original external harmonic injection method needs to consider the flux superposition effect, and automatically generates the required harmonic current by modulating the flux superposition effect through the specific harmonic current closed loop, so that the harmonic injection has higher accuracy, and the adaptability and robustness of the control system are improved.

[0085] The design principle of the application is that in the current source type electrically excited doubly salient motor driving control system with multiplexed field winding, the harmonic current is extracted through the setting of a specific rotating coordinate system, a closed loop control circuit of the harmonic current is constructed, the flux superposition effect of the current source inverter is modulated, the harmonic injection of the electrically excited doubly salient motor driving system is realized, and the inherent output torque ripple is eliminated.

[0086] Based on the above scheme, in order to verify the flux superposition effect modulation method of the specific harmonic current closed loop of the electrically excited doubly salient motor, a mathematical model of the electrically excited doubly salient motor is constructed, a current source type electrically excited doubly salient motor driving control system with multiplexed field winding is constructed, the power part includes the electrically excited doubly salient motor, a DC / DC converter and a current source type inverter with multiplexed field winding, and the control part is a speed current double closed loop vector control. On this basis, the harmonic current extraction module, the harmonic current control module and the flux superposition effect modulation module are built in the control part to carry out simulation verification. The main parameters in the test process are shown in the following table:

[0087] Table 8 Simulation setting parameters

[0088]

[0089] The specific simulation results and analysis are as follows:

[0090] As Figure 5(a) and 5(b)The A-phase current waveform before injecting the harmonic and its Fourier analysis result are shown. Under the sinusoidal wave drive of the current source inverter, the phase current of the doubly salient electro-magnetic motor has good sinusoidal degree, and the THD is 0.54%.

[0091] Fig. 6(a) is the A-phase current waveform after injecting the harmonic, and Fig. 6(b) is its Fourier analysis result. After injecting the harmonic, the current is distorted, and the THD increases to 4.11%. The main harmonic component is the 5th harmonic, which accounts for 4%; and there are also a small amount of high-order harmonics generated due to the flux-adding effect.

[0092] Fig. 7(a) is the torque ripple waveform before injecting the harmonic, and Fig. 7(b) is the torque ripple waveform after injecting the harmonic. As can be seen from the waveforms, before injecting the harmonic, the sinusoidal wave drive is adopted, and the peak-to-peak value of the torque ripple is about 0.4 N·m; and after injecting the harmonic, the amplitude of the torque ripple is about 0.2 N·m, and the amplitude of the torque ripple is reduced by about 50%. It can be seen that the flux-adding effect modulation method of the specific harmonic current closed loop of the doubly salient electro-magnetic motor adopted in the present application has good effect, the injected harmonic has high precision, and the torque ripple suppression effect is more remarkable.

[0093] Fig. 8(a) is the torque ripple waveform during the change of the speed from 200 rpm to 400 rpm, and Fig. 8(b) is the torque ripple waveform at 400 rpm. During the change of the speed, the system can still operate stably and has always certain torque ripple suppression effect; when the speed reaches 400 rpm, the peak-to-peak value of the torque ripple is about 0.2 N·m, and it can be seen that the system still has good torque ripple suppression effect. Therefore, the adaptability and robustness of the system are stronger.

Claims

1. A method for modulating the superimposed current effect in closed-loop control of specific harmonic currents of an electrically excited doubly salient pole motor, characterized in that, Includes the following steps: Step 1: Based on the harmonic characteristics of the back EMF of the electrically excited doubly salient pole motor, analyze the inherent torque ripple and calculate the harmonic current setpoint i required to suppress the torque ripple. d5th_ref i q5th_ref i d7th_ref i q7th_ref ; Step 2: Sample the three-phase current i of the motor a i b i c The signal i was obtained after five and seven synchronous rotational coordinate transformations, respectively. d5 i q5 i d7 i q7 The high-frequency terms are then filtered out by a low-pass filter to extract the DC component, yielding the feedback value i of the harmonic current control loop. d5th i q5th i d7th i q7th ; Step 3: Transfer the feedback value i d5th i q5th i d7th i q7th and given value i d5th_ref i q5th_ref i d7th_ref i q7th_ref The harmonic current i injected in the α-β coordinate system is obtained by performing Clark transformation on the output value of the PI controller in the harmonic current control loop. α5th i β5th i α7th i β7th The harmonic vector action times d1 and d2 are calculated. Step 4: Determine the magnitude of the three-phase capacitor voltage and extend the conduction time of the switching transistor accordingly; Step 5: Based on the setting of extending the conduction time of the switching transistor in Step 4, obtain the switching time T of the switching transistor according to the seven-segment SVPWM modulation method. cm1 T cm2 T cm3 T cm4 T cm5 T cm6 Furthermore, the switching transistor drive signals S1 to S6 are obtained through PWM.

2. The method for modulation of superimposed current effect in closed-loop control of specific harmonic currents of an electrically excited doubly salient pole motor as described in claim 1, characterized in that, In step 2, the three-phase current i of the sampled motor is... a i b i c The signal i was obtained after five and seven synchronous rotational coordinate transformations, respectively. d5 i q5 i d7 i q7 The electrically excited bisalient phase current i a satisfy When, corresponding to i d5 i q5 i d7 i q7 They are respectively: The first two terms are high-frequency components with frequencies of 6ωt and 12ωt, respectively. The third term is a DC component containing specific harmonic amplitude information. The high-frequency component is directly filtered out by a low-pass filter, leaving the DC feedback signal i of the harmonic current control loop. d5th i q5th i d7th i q7th .

3. The method for modulation of superimposed current effect in closed-loop control of specific harmonic currents of an electrically excited doubly salient pole motor as described in claim 1, characterized in that, In step 3, the harmonic vector action times d1 and d2 are calculated for different sectors using the same method as for non-zero vector action times. The original current vector is located in sector I, and the current vector after harmonic injection is located in sector VI. The harmonic vector action times d1 and d2 are: Where T s For the switching cycle, I dc This refers to the DC-side current of a current-source inverter.

4. The method for modulation of superimposed current effect in closed-loop control of specific harmonic currents of an electrically excited doubly salient pole motor as described in claim 1, characterized in that, In step 4, when the current vector is located in sectors II, IV, and VI, when the current commutation changes from the phase with lower capacitor voltage to the phase with higher capacitor voltage, the on-time of the corresponding switch in the lower voltage phase is extended by d1; when the current commutation changes from the phase with higher capacitor voltage to the phase with lower capacitor voltage, the on-time of the corresponding switch in the higher voltage phase is extended.

5. The method for modulation of superimposed current effect in closed-loop control of specific harmonic currents of an electrically excited doubly salient pole motor as described in claim 1, characterized in that, In step 4, when the current vector is located in sectors I, III, and V, when the current commutation changes from the phase with higher capacitor voltage to the phase with lower capacitor voltage, the on-time of the corresponding switch in the higher voltage phase is extended by d2; when the current commutation changes from the phase with lower capacitor voltage to the phase with higher capacitor voltage, the on-time of the corresponding switch in the lower voltage phase is extended.

6. The method for modulation of superimposed current effect in closed-loop control of specific harmonic currents of an electrically excited doubly salient pole motor as described in claim 1, characterized in that, In step 4, when the current commutation changes from the phase with higher capacitor voltage to the phase with lower capacitor voltage, the on-time of the corresponding switch in the higher voltage phase is extended. When current commutation occurs from the phase with lower capacitor voltage to the phase with higher capacitor voltage, the on-time of the corresponding switch in the lower voltage phase is extended. Where T1 and T2 are the non-zero vector action times in the seven-segment SVPWM modulation.

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