Lamination effect modulation method for closed-loop control of specific subharmonic current of doubly salient electro-magnetic motor

Abstract

The invention discloses a superposition effect modulation method for closed-loop control of specific-order harmonic current of an electro-magnetic doubly salient motor, and the method comprises the steps: setting a specific-order rotating coordinate system to extract harmonic current in a current source type electro-magnetic doubly salient motor drive control system of a multiplex excitation winding, constructing a harmonic current closed-loop control loop, and carrying out the modulation of the specific-order harmonic current in the current source type electro-magnetic doubly salient motor. According to the method, the current source inverter is used for modulating the current superposition effect of the current source inverter, specific-order current harmonic current is generated, inherent torque pulsation of the doubly salient electro-magnetic motor in a sine wave driving mode is counteracted, and the output characteristic of the doubly salient electro-magnetic motor driving system is improved. According to the method, the cascade time distribution of the current source type inverter can be set in a closed-loop manner, and specific current harmonic injection is realized, so that the output torque ripple of a motor driving system is eliminated, and the influence generated by the cascade effect in a traditional current source type inverter is avoided.

Description

Technical Field

[0001] The present invention relates to the field of motor control technology, and in particular to a stacking current effect modulation method for closed-loop control of specific subharmonic current of an electrically excited double-pole motor. Background Art

[0002] With the vigorous development of the new energy industry, higher requirements are put forward for the operating efficiency, control performance and reliability of the electric drive system with motors as the control object. At the same time, it is also crucial to reduce the cost of the drive motor while maintaining good motor performance. The excitation current of the electrically excited double-pole motor is controllable, which has the advantages of simple speed regulation, and can be demagnetized in time when a fault occurs, which improves reliability. Moreover, since it is an electrically excited motor, no permanent magnet is required, which greatly reduces the cost. In addition, the use of a current source inverter can reuse the excitation winding of the electrically excited double-pole motor as the energy storage inductor on the DC side of the current source inverter, which reduces the cost and improves the system power density. Therefore, the drive system of the electrically excited double-pole motor based on the current source inverter has broad application prospects. In the operation process of the electrically excited double-pole motor, due to the structural design of the motor, even if the current source inverter sinusoidal wave drive has greatly reduced the torque pulsation, it still has its inherent torque pulsation, which brings greater vibration and noise. Therefore, it is of great significance to suppress the torque pulsation by injecting harmonic current.

[0003] At present, the research on suppressing torque pulsation by harmonic injection is mainly divided into two categories: 1) calculating the harmonic current according to the torque model and injecting harmonics from the outside; 2) generating harmonic current according to the closed-loop control of torque pulsation, without calculating the external injected harmonics. The first method is usually used in most harmonic injection applications. The given value of the external injected harmonic is calculated by the relationship between the inherent torque pulsation and the additional torque pulsation generated by the harmonic current to offset each other, and the injection of harmonics is completed by adjusting the duty cycle in the control of the switch tube. This method requires observing the motor flux and back electromotive force in advance to obtain the calculation model of the inherent torque pulsation. In response to this problem, some scholars have proposed the second method. According to the positive proportional relationship between the speed pulsation amplitude and the torque pulsation amplitude, a closed-loop control of the speed pulsation is constructed to automatically generate a given value for the injected harmonic.

[0004] However, in a drive system based on a current source inverter, since the overlap time needs to be set for the current source inverter, the error current generated by the overlap effect will affect the harmonic injection. When injecting harmonics externally, if the impact of the additional torque pulsation introduced by the overlap effect is considered, then it is necessary to obtain the given value of the injected harmonic current based on the mutual cancellation of the three parts of the torque pulsation, and the calculation process will be very complicated.

[0005] Therefore, in order to suppress the torque ripple of the electrically excited doubly salient motor drive system based on a current source inverter, a harmonic injection method that can take into account the overlapped current effect is urgently needed. Summary of the invention

[0006] Purpose of the invention: The present invention provides a method for modulating the folded current effect of a closed-loop control of a specific subharmonic current of an electrically excited double-pole motor, thereby realizing harmonic injection into an electrically excited double-pole motor drive system and eliminating inherent output torque pulsation.

[0007] Technical solution: The stacking effect modulation method of a specific subharmonic current closed-loop control of an electrically excited double-pole motor described in the present invention comprises the following steps:

[0008] Step 1: Analyze the inherent torque pulsation based on the harmonic characteristics of the back electromotive force of the electrically excited doubly salient pole motor and calculate the harmonic current given value i required to suppress the torque pulsation. d5th_ref 、i q5th_ref 、i d7th_ref 、i q7th_ref ;

[0009] Step 2: Sample the motor three-phase current i a 、i b 、i c , respectively, after five and seven synchronous rotation coordinate transformations, the signal i is obtained d5 、i q5 、i d7 、i q7 , and then the high-frequency term is filtered out by a low-pass filter to extract its DC component, and the feedback value i of the harmonic current control loop is obtained d5th 、i q5th 、i d7th 、i q7th ;

[0010] Step 3: Set 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 Through the PI controller of the harmonic current control loop, the output value is Clark transformed to obtain the injected harmonic current i in the α-β coordinate system. α5th 、i β5th 、i α7th 、i β7th , calculate and obtain the harmonic vector action time d1, d2;

[0011] Step 4: Determine the voltage of the three-phase capacitor. When the current vector is in sectors II, IV, and VI, when the current commutates from a phase with low capacitor voltage to a phase with high capacitor voltage, extend the conduction time of the switch tube corresponding to the low voltage phase by d1; when the current commutates from a phase with high capacitor voltage to a phase with low capacitor voltage, extend the conduction time of the switch tube corresponding to the high voltage phase by d1. When the current vector is located in sectors Ⅰ, Ⅲ, and Ⅴ, when the current commutates from a phase with a high capacitor voltage to a phase with a low capacitor voltage, the conduction time of the switch tube corresponding to the high voltage phase is extended by d2; when the current commutates from a phase with a low capacitor voltage to a phase with a high capacitor voltage, the conduction time of the switch tube corresponding to the low voltage phase is extended by

[0012]

[0013] Step 5: According to the setting of extending the switch on time in step 4, the switch switching time T is obtained according to the modulation method of the seven-segment SVPWM. cm1 , T cm2 , T cm3 , T cm4 , T cm5 , T cm6 , and further obtain the switch tube driving signals S1~S6 through PWM.

[0014] Furthermore, in step 2, the motor three-phase current i is sampled. a 、i b 、i c , respectively, after five and seven synchronous rotation coordinate transformations, the signal i is obtained d5 、i q5 、i d7 、i q7 , the electric excitation doubly salient phase current i a satisfy When i d5 、i q5 、i d7 、i q7 They are:

[0015]

[0016] The first two items are high-frequency components with frequencies of 6ωt and 12ωt respectively, and the third item is a DC component containing specific subharmonic amplitude information. The high-frequency component is directly filtered out by a low-pass filter, and what remains is the DC feedback signal i of the harmonic current control loop. d5th 、i q5th 、i d7th 、i q7th .

[0017] Furthermore, in step 3, the harmonic vector action times d1 and d2 are calculated in different sectors by referring to the calculation method of the non-zero vector action time. Taking the original current vector in sector I and the current vector after harmonic injection in sector VI as an example, the harmonic vector action times d1 and d2 are:

[0018]

[0019] Where T s is the switching cycle, I dc is the DC side current of the current source inverter.

[0020] Furthermore, in step 4, when the current commutates from a phase with a high capacitor voltage to a phase with a low capacitor voltage, the conduction time of the switch tube corresponding to the high voltage phase is extended. When the current commutates from the phase with low capacitor voltage to the phase with high capacitor voltage, the conduction time of the switch tube corresponding to the low voltage phase is extended. Among them, T1 and T2 are the non-zero vector action times in SVPWM modulation.

[0021] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: the present invention makes full use of the characteristics of the current source inverter drive system and utilizes its folding current effect to generate the required harmonic current, thereby solving the problem of complex calculation caused by the original external harmonic injection method due to the need to consider the folding current effect to generate additional harmonic currents; the folding 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 improves the adaptability and robustness of the control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the method flow of the present invention.

[0023] FIG. 2( a ) is a composite diagram of current vectors located in the same sector before and after harmonic injection according to the present invention.

[0024] FIG. 2( b ) is a composite diagram of current vectors located in different sectors before and after harmonic injection according to the present invention.

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

[0026] Figure 4 It is a diagram of the switch switching and driving signals of each sector in the present invention.

[0027] FIG5( a ) is a schematic diagram of the phase current waveform before harmonic injection according to the present invention.

[0028] FIG5( b ) is a diagram showing the Fourier analysis results of the phase current before harmonic injection according to the present invention.

[0029] FIG6( a ) is a phase current waveform after harmonic injection according to the present invention.

[0030] FIG6( b ) is a diagram showing the Fourier analysis results of the phase current after harmonic injection according to the present invention.

[0031] FIG. 7( a ) is a schematic diagram of the torque pulsation waveform before harmonic injection according to the present invention.

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

[0033] FIG8( a ) is a torque pulsation waveform diagram during the process of increasing the speed from 200 rpm to 400 rpm according to the present invention.

[0034] FIG8( b ) is a torque pulsation waveform diagram of the present invention at 400 rpm. DETAILED DESCRIPTION

[0035] like Figure 1 As shown, a method for modulating the stacking effect of a closed-loop control of a specific subharmonic current of an electrically excited double-pole motor comprises the following steps:

[0036] S1: Based on the harmonic characteristics of the back electromotive force of the electrically excited doubly salient pole motor, the inherent torque pulsation analysis is generated, and the harmonic current given value i required to suppress the torque pulsation is calculated. d5th_ref 、i q5th_ref 、i d7th_ref 、i q7th_ref .

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

[0038] S3: Feedback value i d5th 、i q5th 、i d7th 、i q7th And given value i d5th_ref 、i q5th_ref 、i d7th_ref 、i q7th_refThrough the PI controller of the harmonic current control loop, the output value is Clark transformed to obtain the injected harmonic current i in the α-β coordinate system. α5th 、i β5th 、i α7th 、i β7th , and the harmonic vector action times d1 and d2 are calculated.

[0039] S4: Determine the voltage of the three-phase capacitor. When the current vector is in sectors II, IV, and VI, when the current commutates from a phase with low capacitor voltage to a phase with high capacitor voltage, the conduction time of the switch tube corresponding to the low voltage phase is extended by d1; when the current commutates from a phase with high capacitor voltage to a phase with low capacitor voltage, the conduction time of the switch tube corresponding to the high voltage phase is extended by d1. When the current vector is located in sectors Ⅰ, Ⅲ, and Ⅴ, when the current commutates from a phase with a high capacitor voltage to a phase with a low capacitor voltage, the conduction time of the switch tube corresponding to the high voltage phase is extended by d2; when the current commutates from a phase with a low capacitor voltage to a phase with a high capacitor voltage, the conduction time of the switch tube corresponding to the low voltage phase is extended by

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

[0041] In step S2, the three-phase current i containing harmonic components is acquired. a 、i b 、i c for:

[0042]

[0043] The five- and seven-time synchronous rotation coordinate transformation matrices are:

[0044]

[0045] The signal i obtained after the rotation coordinate transformation d5 、i q5 、i d7 、i q7 for:

[0046]

[0047] The harmonic current control loop feedback signal i obtained by the low-pass filter isd5th 、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, the output value of the harmonic current control loop is Clark transformed 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 introduced is:

[0050]

[0051] Transform it to the α-β coordinate system and get:

[0052]

[0053] Therefore, the harmonic vector action time d1 and d2 in this case are obtained as follows:

[0054]

[0055] As shown in Figure 2(b), when the actual current vector after harmonic injection is located in different sectors from the original current vector, the output value of the harmonic current control loop is Clark transformed 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 introduced is:

[0056]

[0057] Transform it to the α-β coordinate system and get:

[0058]

[0059] Therefore, the harmonic vector action time d1 and d2 in this case are obtained as follows:

[0060]

[0061] Therefore, the actual current vector is used to judge the sector, and the harmonic vector action time d1 and d2 of each sector are shown in Table 1:

[0062] Table 1 Harmonic vector action time of each sector

[0063]

[0064] in,

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

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

[0067] Table 2 Current sector I switch switching point settings

[0068]

[0069] Table 3 Current sector II switch point settings

[0070]

[0071]

[0072] Table 4 Current sector III switch point settings

[0073]

[0074] Table 5 Current sector IV switch point settings

[0075]

[0076]

[0077] Table 6 Current sector V switch point settings

[0078]

[0079]

[0080] Table 7 Current sector VI switch point settings

[0081]

[0082] Among them, T a , T b , T c It is the switching point in the seven-segment SVPWM modulation.

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

[0084] Compared with the existing harmonic injection method, the above-mentioned method for modulating the folding current effect of the specific harmonic current closed loop of the electrically excited double-pole motor makes full use of the characteristics of the current source inverter drive system, generates the required harmonic current through its folding current effect, and solves the problem of the original external harmonic injection method that needs to consider the folding current effect; and the folding 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, thereby improving the adaptability and robustness of the control system.

[0085] The design principle of the present invention is: in a current source type electrically excited double-pole motor drive control system with a multiplexed excitation winding, a specific order rotating coordinate system is set to extract harmonic currents, a closed-loop control loop of harmonic currents is constructed, and the stacking effect of the current source inverter is modulated to achieve harmonic injection into the electrically excited double-pole motor drive system and eliminate inherent output torque pulsation.

[0086] Based on the above scheme, in order to verify the above-mentioned double-pole motor specific subharmonic current closed-loop modulation method of the double-pole motor, a mathematical model of the double-pole motor was constructed, and a current source type double-pole motor drive control system with multiple excitation windings was constructed. The power part includes the double-pole motor, the DC / DC converter and the current source inverter with multiple excitation windings. The control part is the vector control of the speed and current double closed loop. On this basis, the control part built a harmonic current extraction module, a harmonic current control module, and a double-pole current effect modulation module for simulation verification. The main parameter settings during the test are shown in the following table:

[0087] Table 8 Simulation setting parameters

[0088]

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

[0090] like Figure 5(a) and 5(b)The following figure shows the A-phase current waveform before harmonic injection and its Fourier analysis result. Under the sine wave drive of the current source inverter, the phase current of the electrically excited doubly salient motor has a good sinusoidal degree, and its THD is 0.54%.

[0091] Figure 6(a) shows the current waveform of phase A after harmonic injection, and Figure 6(b) shows the Fourier analysis result. After harmonic injection, the current is distorted and the THD increases to 4.11%. The main component is the 5th harmonic, accounting for 4%, and there are also a small amount of higher harmonics generated by the overlapping current effect.

[0092] Figure 7(a) is the torque pulsation waveform before harmonic injection, and Figure 7(b) is the torque pulsation waveform after harmonic injection. It can be seen from the waveform that before harmonic injection, sinusoidal wave drive is used, and the peak-to-peak value of the torque pulsation is about 0.4N·m; after harmonic injection, the torque pulsation amplitude is about 0.2N·m, and the torque pulsation amplitude is reduced by about 50%. It can be seen that the lapped current effect modulation method of the specific subharmonic current closed loop of the electrically excited double-pole motor adopted in the present invention has good effect, high harmonic injection accuracy, and more significant torque pulsation suppression effect.

[0093] Figure 8(a) is the torque pulsation waveform when the speed changes from 200rpm to 400rpm, and Figure 8(b) is the torque pulsation waveform at 400rpm. During the speed change, the system can still operate stably and always has a certain torque pulsation suppression effect; when the speed reaches 400rpm, the peak-to-peak value of the torque pulsation is about 0.2N·m, which shows that the system still has a good torque pulsation suppression effect. Therefore, the system has strong adaptability and robustness.

Claims

1. A method for modulating the overlapped current effect of a closed-loop control of a specific subharmonic current of an electrically excited doubly salient pole motor, characterized in that: The steps include: Step 1: Analyze the inherent torque pulsation based on the harmonic characteristics of the back electromotive force of the electrically excited doubly salient pole motor and calculate the harmonic current given value i required to suppress the torque pulsation. d5th_ref 、i q5th_ref 、i d7th_ref 、i q7th_ref ; Step 2: Sample the motor three-phase current i a 、i b 、i c , respectively, after five and seven synchronous rotation coordinate transformations, the signal i is obtained d5 、i q5 、i d7 、i q7 , and then the high-frequency term is filtered out by a low-pass filter to extract its DC component, and the feedback value i of the harmonic current control loop is obtained d5th 、i q5th 、i d7th 、i q7th ; Step 3: Set 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 Through the PI controller of the harmonic current control loop, the output value is Clark transformed to obtain the injected harmonic current i in the α-β coordinate system. α5th 、i β5th 、i α7th 、i β7th , calculate and obtain the harmonic vector action time d1, d2; Step 4: Determine the voltage of the three-phase capacitor and extend the conduction time of the switch tube; Step 5: According to the setting of extending the switch tube conduction time in step 4, the switch tube switching time T is obtained according to the modulation method of the seven-segment SVPWM. cm1 , T cm2 , T cm3 , T cm4 , T cm5 , T cm6 , and further obtain the switch tube driving signals S1~S6 through PWM.

2. The stacking effect modulation method for closed-loop control of specific subharmonic current of an electrically excited doubly salient pole motor according to claim 1, characterized in that: In step 2, the motor three-phase current i is sampled a 、i b 、i c , respectively, after five and seven synchronous rotation coordinate transformations, the signal i is obtained d5 、i q5 、i d7 、i q7 , the electric excitation doubly salient phase current i a satisfy When i d5 、i q5 、i d7 、i q7 They are: The first two items are high-frequency components with frequencies of 6ωt and 12ωt respectively, and the third item is a DC component containing specific subharmonic amplitude information. The high-frequency component is directly filtered out by a low-pass filter, and what remains is the DC feedback signal i of the harmonic current control loop. d5th 、i q5th 、i d7th 、i q7th .

3. The stacking effect modulation method for closed-loop control of specific subharmonic current of an electrically excited doubly salient pole motor according to claim 1, characterized in that: In step 3, the harmonic vector action times d1 and d2 are calculated in different sectors by referring to the calculation method of the non-zero vector action time. 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 is the switching cycle, I dc is the DC side current of the current source inverter.

4. The stacking effect modulation method for closed-loop control of specific subharmonic current of an electrically excited doubly salient pole motor according to claim 1, characterized in that: In step 4, when the current vector is located in sectors II, IV, and VI, when the current commutates from a phase with a low capacitor voltage to a phase with a high capacitor voltage, the conduction time of the switch tube corresponding to the low voltage phase is extended by d1; when the current commutates from a phase with a high capacitor voltage to a phase with a low capacitor voltage, the conduction time of the switch tube corresponding to the high voltage phase is extended by 5. The stacking effect modulation method for closed-loop control of specific subharmonic current of an electrically excited doubly salient pole motor according to claim 1, characterized in that: In step 4, when the current vector is located in sectors I, III, and V, when the current commutates from a phase with a high capacitor voltage to a phase with a low capacitor voltage, the conduction time of the switch tube corresponding to the high voltage phase is extended by d2; when the current commutates from a phase with a low capacitor voltage to a phase with a high capacitor voltage, the conduction time of the switch tube corresponding to the low voltage phase is extended by 6. The stacking effect modulation method for closed-loop control of specific subharmonic current of an electrically excited doubly salient pole motor according to claim 1, characterized in that: In step 4, when the current commutates from the phase with high capacitor voltage to the phase with low capacitor voltage, the conduction time of the switch tube corresponding to the high voltage phase is extended. When the current commutates from the phase with low capacitor voltage to the phase with high capacitor voltage, the conduction time of the switch tube corresponding to the low voltage phase is extended. Among them, T1 and T2 are the non-zero vector action times in the seven-segment SVPWM modulation.

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