Electrolytic capacitor-free permanent magnet synchronous motor torque ripple suppression method and device based on current harmonic injection

Abstract

The invention discloses a non-electrolytic capacitor permanent magnet synchronous motor torque ripple suppression method and device based on current harmonic injection, and belongs to the field of permanent magnet synchronous motor control, and the method comprises the steps: enabling the power of an inverter to be equal to the ideal network side input power as a target, carrying out the harmonic injection of a q-axis current given reference value Iq0, and obtaining a reference value Iq0; and performing harmonic injection on a d-axis current given reference value Id0 to obtain a d-axis current reference value # imgabs1 #, performing PI control on differences between the d-axis current reference value and the q-axis feedback current and between the d-axis current reference value and the q-axis current reference value and between the d-axis current reference value and the q-axis feedback current after PI control is performed on the d-axis current reference value and the q-axis current reference value, adding the d-axis current reference value and the q-axis current reference value to d-axis feed-forward structure voltage and q-axis feed-forward structure voltage of the motor to obtain a d-axis current reference value # imgabs0 # and a q-axis current reference value # imgabs1 #. And 4, obtaining d and q axis voltage reference values # imgabs2 #, converting # imgabs3 # into alpha and beta axis voltage reference values, and generating PWM (Pulse Width Modulation) signals for controlling each switching tube in the inverter. According to the invention, on the premise of not increasing extra hardware cost, the torque ripple of the output torque is effectively reduced, and meanwhile, a high input power factor is realized.

Description

Technical Field

[0001] The present invention belongs to the field of permanent magnet synchronous motor control, and more specifically, relates to a method and device for suppressing torque pulsation of a permanent magnet synchronous motor without electrolytic capacitor based on current harmonic injection. Background Art

[0002] Built-in permanent magnet synchronous motors are widely used in automotive, aerospace and other industrial fields due to their high power density, low energy consumption and simple structure. Traditional permanent magnet synchronous motor drive systems use large-capacity electrolytic capacitors of hundreds or thousands of microfarads to stabilize the DC link voltage and power the inverter. However, the electrolytic capacitors are bulky, which limits the service life of the inverter circuit. At the same time, in order to improve the power factor and reduce grid-side harmonic pollution, a power factor correction (PFC) circuit must be added, which will cause more power loss and increase the weight and cost of the motor drive system.

[0003] To solve these problems, researchers have developed an electrolytic capacitor-free motor drive system. This topology uses a few microfarad film capacitors instead of large-capacity electrolytic capacitors as bus capacitors, which greatly reduces the size of the motor drive system. In addition, since the PFC circuit is omitted, the efficiency and reliability of the drive system are improved. In addition, since the capacity of the bus capacitor is significantly reduced, the bus voltage will fluctuate with the grid voltage. Since the coupling between the grid input side and the inverter output side is strengthened, proper control of the inverter output power can improve the performance of the grid-side current.

[0004] However, due to the violent fluctuation of bus voltage, q-axis current will also fluctuate violently, so the output torque pulsation is serious. The torque pulsation will cause mechanical vibration of the motor, increased noise, increased speed fluctuation and reduced efficiency. In order to solve the problem of torque pulsation in electrolytic capacitor-free motor drive system, the current main method is to change the topology structure. The document "Single-Phase Grid-Connected Motor Drive System With DC-Link Shunt Compensator and Small DC-Link Capacitor" proposes a DC shunt compensator (DSC) suitable for electrolytic capacitor-free motor drive system. The DSC is connected in parallel to the DC link as an energy buffer to provide an additional voltage source for the system. This measure effectively reduces the bus voltage fluctuation and the torque pulsation of the motor, while improving efficiency. The document “Single-Phase to Three-Phase Electrolytic Capacitor-Less Dual Inverter-FedIPMSM for Suppress Torque Pulsation” proposes an electrolytic capacitor-free system consisting of a main inverter, a floating inverter and an open-winding permanent magnet synchronous motor. One inverter is used to drive the motor and the other inverter is used to suppress load power pulsation. The system can achieve significant torque pulsation suppression effect.

[0005] The existing method of achieving torque pulsation suppression by changing the topology can effectively improve the torque pulsation problem of the electrolytic capacitor-free permanent magnet synchronous motor. However, due to the use of additional hardware circuits, the size and cost of the system will increase. Summary of the invention

[0006] In view of the defects of the prior art and the need for improvement, the present invention provides a method and device for suppressing torque pulsation of a permanent magnet synchronous motor without electrolytic capacitor based on current harmonic injection. The purpose is to effectively reduce the torque pulsation of the output torque of the electrolytic content motor system without increasing additional hardware costs, while achieving a high input power factor.

[0007] To achieve the above object, according to one aspect of the present invention, a method for suppressing torque ripple of a permanent magnet synchronous motor without electrolytic capacitor based on current harmonic injection is provided, comprising the following steps:

[0008] S1: In the current cycle, the motor is given a speed and the actual motor speed ω m The difference between them is PI regulated to obtain the given reference value I of the q-axis current q0 , and the stator voltage vector u given in the previous cycleS and the inverter output voltage limit u max The difference between them is averaged and then PI adjustment is performed to obtain the d-axis current reference value I d0 ;

[0009] S2: so that the inverter power p inv Equal to the ideal grid-side input power p in As the target, the reference value I is given for the q-axis current q0 Perform harmonic injection to obtain the q-axis current reference value Ideal grid-side input power p in The grid-side input power when the grid-side power factor is the largest;

[0010] S3: To minimize the torque ripple of the motor output torque, a reference value I is given to the d-axis current. d0 Perform harmonic injection to obtain the d-axis current reference value

[0011] S4: Collect the three-phase current of the motor and convert it to obtain the d-axis feedback current i d and q-axis feedback current i q ;

[0012] S5: Reference value for d-axis current and the d-axis feedback current i d After PI control, the motor d-axis feedforward decoupling voltage Add together to get the d-axis voltage reference value Reference value for q-axis current With the q-axis feedback current i q After PI control, the motor q-axis feedforward decoupling voltage Add together to get the q-axis voltage reference value

[0013] S6: Set the d-axis voltage reference value and q-axis voltage reference value Transformed into α-axis voltage reference value and β-axis voltage reference value According to the α-axis voltage reference value and β-axis voltage reference value Generate PWM signals for controlling each switch in the inverter to complete the control of the current cycle.

[0014] Further,

[0015]

[0016] Among them, θ g Indicates the phase angle of the grid voltage.

[0017] Further,

[0018]

[0019] Among them, I d0 Indicates the d-axis current reference value The DC component, I d2 Indicates the amplitude of the 100Hz cosine component in the current harmonics, I d4 Indicates the amplitude of the 200Hz cosine component in the current harmonics.

[0020] Further,

[0021] I d2 =σI d0

[0022]

[0023] in, n p is the number of motor pole pairs, L d is the motor d-axis inductance, L q is the motor q-axis inductance, is the permanent magnet flux of the motor; σ and τ are proportional coefficients, and they satisfy 0<σ<1, -1<τ<0.

[0024] Further, in step S6, according to the α-axis voltage reference value and β-axis voltage reference value Generate PWM signals for each switch in the inverter, including:

[0025] Calculate the ideal grid-side input power p in The difference between the actual inverter power and the feedforward compensation power p cmp ;

[0026] according to Calculate the α-axis feedforward compensation voltage Δu α_ff and β-axis feedforward compensation voltage Δu β_ff ;

[0027] The α-axis voltage reference value and β-axis voltage reference value Respectively with the α-axis feedforward compensation voltage Δu α_ff and β-axis feedforward compensation voltage Δu β_ff Add together to get the actual α-axis voltage reference value and the actual β-axis voltage reference value

[0028] The actual α-axis voltage reference value and the actual β-axis voltage reference value Perform SVPWM modulation to obtain the PWM signal of each switch tube in the inverter;

[0029] Among them, i α is the α-axis feedback current, i β is the β-axis feedback current.

[0030] According to another aspect of the present invention, there is provided a torque pulsation suppression device for a permanent magnet synchronous motor without electrolytic capacitor based on current harmonic injection, comprising: a speed controller, a magnetic field weakening controller, a dq axis current reference generation module, a current sampling module, a current loop controller, a voltage conversion module and a modulation module;

[0031] The speed controller has a first input terminal for inputting the motor's given speed. Its second input terminal is used to input the actual motor speed ω m , which is used to set the motor speed in the current cycle and the actual motor speed ω m The difference between them is PI regulated to obtain the given reference value I of the q-axis current q0 ;

[0032] The first input of the weak magnetic controller is used to input the stator voltage vector u given in the previous cycle. S The second input terminal is used to input the inverter output voltage limit u max , which is used to convert the stator voltage vector u given in the previous cycle into S and the inverter output voltage limit u max The difference between them is averaged and then PI adjustment is performed to obtain the d-axis current reference value I d0 ;

[0033] The dq axis current reference generation module has a first input terminal connected to the output terminal of the speed controller, and a second input terminal connected to the output terminal of the weak magnetic controller, which is used to make the inverter power p inv Equal to the ideal grid-side input power p in As the target, the reference value I is given for the q-axis current q0 Perform harmonic injection to obtain the q-axis current reference value The dq axis current reference generation module is also used to set a reference value I for the d axis current with the goal of minimizing the torque ripple of the motor output torque. d0 Perform harmonic injection to obtain the d-axis current reference value

[0034] The current sampling module is connected to the motor to collect the three-phase current of the motor and convert the three-phase current into the α-axis feedback current i through Clark transformation. α and the β-axis feedback current i βThen, the α-axis feedback current i is converted into α and the β-axis feedback current i β Converted to d-axis feedback current i d and q-axis feedback current i q ;

[0035] The current loop controller has a first input terminal connected to the output terminal of the dq axis current reference generation module, a second input terminal connected to the output terminal of the current sampling module, and a third input terminal for receiving the motor d axis feedforward decoupling voltage and the motor q-axis feedforward decoupling voltage It is used for the d-axis current reference value and the d-axis feedback current i d After PI control, the motor d-axis feedforward decoupling voltage Add together to get the d-axis voltage reference value And the reference value of q-axis current With the q-axis feedback current i q After PI control, the motor q-axis feedforward decoupling voltage Add together to get the q-axis voltage reference value

[0036] The voltage conversion module has an input end connected to the output end of the current loop controller, which is used to convert the d-axis voltage reference value and q-axis voltage reference value Transformed into α-axis voltage reference value and β-axis voltage reference value

[0037] The modulation module has an input end connected to the output end of the voltage conversion module, which is used to modulate the voltage according to the α-axis voltage reference value. and β-axis voltage reference value Generate PWM signals for controlling each switch in the inverter to complete the control of the current cycle;

[0038] Among them, the ideal grid-side input power p in It is the grid-side input power when the grid-side power factor is maximum.

[0039] Furthermore, the torque pulsation suppression device for a permanent magnet synchronous motor without electrolytic capacitor based on current harmonic injection provided by the present invention further includes: a feedforward power correction module arranged between the voltage conversion module and the modulation module;

[0040] The feedforward power correction module has a first input terminal for receiving the ideal grid-side input power p inIts second input terminal is used to receive the actual inverter power, its third input terminal is connected to the output terminal of the voltage conversion module, and its output terminal is connected to the input terminal of the modulation module, which is used to calculate the ideal grid-side input power p in The difference between the actual inverter power and the feedforward compensation power p cmp ,according to Calculate the α-axis feedforward compensation voltage Δu α_ff and β-axis feedforward compensation voltage Δu β_ff , and the α-axis voltage reference value and β-axis voltage reference value Respectively with the α-axis feedforward compensation voltage Δu α_ff and β-axis feedforward compensation voltage Δu β_ff Add together to get the actual α-axis voltage reference value and the actual β-axis voltage reference value

[0041] Furthermore, the modulation module is used to adjust the actual α-axis voltage reference value and the actual β-axis voltage reference value Perform SVPWM modulation to obtain the PWM signal of each switch tube in the inverter.

[0042] According to another aspect of the present invention, a permanent magnet synchronous motor system without electrolytic capacitor is provided, comprising: a permanent magnet synchronous motor without electrolytic capacitor, and the above-mentioned permanent magnet synchronous motor torque pulsation suppression device without electrolytic capacitor based on current harmonic injection provided by the present invention.

[0043] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0044] (1) The present invention performs current harmonic injection on a given reference value of the q-axis current so that the inverter power is equal to the ideal grid-side input power, and performs current harmonic injection on a given reference value of the d-axis current so that the torque pulsation in the motor output torque is minimized. The torque pulsation can be effectively suppressed and the power factor can be improved without adding additional hardware.

[0045] (2) Based on the current harmonic injection, the present invention further introduces feedforward power correction to compensate the voltage reference value based on the error of the actual inverter power relative to the ideal grid-side input power, thereby further improving the quality of the grid-side current and improving the input power factor of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a topological structure diagram of the existing electrolytic capacitor-free permanent magnet synchronous motor drive system;

[0047] Figure 2A block diagram of a method for suppressing torque ripple of a permanent magnet synchronous motor without electrolytic capacitor based on current harmonic injection provided by an embodiment of the present invention;

[0048] Figure 3 A schematic diagram of torque pulsation of output torque in a permanent magnet synchronous motor system without electrolytic capacitor provided in an embodiment of the present invention;

[0049] Figure 4 A surface diagram showing the relationship between the torque pulsation degree and the amplitude of injected harmonics of different frequencies provided in an embodiment of the present invention;

[0050] Figure 5 A schematic diagram of the change of torque pulsation when switching from a traditional control method to a torque pulsation suppression method for a permanent magnet synchronous motor without electrolytic capacitor based on current harmonic injection provided by an embodiment of the present invention;

[0051] Figure 6 After adopting the torque pulsation suppression method of a permanent magnet synchronous motor without electrolytic capacitor based on current harmonic injection provided by an embodiment of the present invention, the grid-side current Fourier analysis is compared with the IEC-61000-3-2 harmonic current limit standard and the grid-side input power factor diagram. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0053] In the present invention, the terms "first", "second", etc. (if any) in the present invention and the accompanying drawings are used to distinguish similar objects but not necessarily to describe a specific order or sequence.

[0054] Non-electrolytic capacitor permanent magnet synchronous motor drive system Figure 1 As shown, the 220V / 50Hz single-phase AC voltage source u g , grid-side inductance L g , grid side equivalent resistance R g 、Film capacitor C dc , single-phase uncontrolled rectifier bridge, inverter and permanent magnet synchronous motor. The voltage source supplies power to the whole system; the grid-side inductor filters the grid-side current; the uncontrolled rectifier bridge rectifies the grid-side AC voltage source into rectified power; the film capacitor is used to absorb harmonics and supply power to the inverter; the inverter receives the pulse signal generated by the control system to invert DC power into AC power, providing three-phase power for the permanent magnet synchronous motor.

[0055] In order to overcome the deficiency of the existing method for suppressing torque pulsation of electrolytic capacitor-free motor system that requires additional hardware circuits, the present invention provides a method and device for suppressing torque pulsation of electrolytic capacitor-free permanent magnet synchronous motor based on current harmonic injection. The overall concept is: based on the working characteristics of electrolytic capacitor-free permanent magnet synchronous motor, the relationship between the pulsation amount and the dq axis current in the motor output torque is derived and analyzed, and the q axis current expression that makes the power factor optimal and the optimal d axis current expression for suppressing torque pulsation are obtained, so that the motor output torque pulsation can be effectively suppressed based on appropriate current harmonic injection without adding any additional hardware circuits. On this basis, the grid-side current quality is improved by power correction to further improve the power factor.

[0056] The following are examples.

[0057] Embodiment 1:

[0058] A method for suppressing torque ripple of permanent magnet synchronous motor without electrolytic capacitor based on current harmonic injection, such as Figure 2 As shown, the following steps are included:

[0059] S1: In the current cycle, the motor is given a speed and the actual motor speed ω m The difference between them is PI regulated to obtain the given reference value I of the q-axis current q0 , and the stator voltage vector u given in the previous cycle S and the inverter output voltage limit u max The difference between them is averaged and then PI adjustment is performed to obtain the d-axis current reference value I d0 ;

[0060] S2: so that the inverter power p inv Equal to the ideal grid-side input power p in As the target, the reference value I is given for the q-axis current q0 Perform harmonic injection to obtain the q-axis current reference value Ideal grid-side input power p in The grid-side input power when the grid-side power factor is the largest;

[0061] S3: To minimize the torque ripple of the motor output torque, a reference value I is given to the d-axis current. d0 Perform harmonic injection to obtain the d-axis current reference value

[0062] S4: Collect the three-phase current of the motor and convert it to obtain the d-axis feedback current i d and q-axis feedback current i q ;

[0063] S5: Reference value for d-axis current and the d-axis feedback current i d After PI control, the motor d-axis feedforward decoupling voltage Add together to get the d-axis voltage reference value Reference value for q-axis current With the q-axis feedback current i q After PI control, the motor q-axis feedforward decoupling voltage Add together to get the q-axis voltage reference value

[0064] S6: Set the d-axis voltage reference value and q-axis voltage reference value Transformed into α-axis voltage reference value and β-axis voltage reference value According to the α-axis voltage reference value and β-axis voltage reference value Generate PWM signals for controlling each switch in the inverter to complete the control of the current cycle.

[0065] The specific implementation of each step is further explained below.

[0066] Through the corresponding sensors, the grid voltage u can be collected g , grid current i g , bus voltage u dc 、Motor speedω m , phase current and rotor position information.

[0067] Since this embodiment adopts the SVPWM modulation method to modulate the bus voltage, in step S1, the voltage limit u max for:

[0068]

[0069] Among them, u dc This is the bus voltage.

[0070] In an ideal state, the maximum grid-side power factor is 1. At this time, the grid-side input power, that is, the ideal grid-side input power p in It can be expressed as:

[0071]

[0072] Among them, U g is the sampling grid voltage u g Amplitude, is the sampling grid-side current i g Fundamental wave amplitude; θ g Indicates the grid voltage u gThe phase angle can be obtained through a phase-locked loop (PLL).

[0073] Inverter power p inv The expression is:

[0074]

[0075] Among them, ω e is the motor electrical angular velocity, L d is the motor d-axis inductance, L q is the motor q-axis inductance, is the permanent magnet flux of the motor.

[0076] According to the expression of ideal grid-side input power and inverter power, ignoring the busbar film capacitor power, the ideal grid-side input power p in and inverter power p inv can be considered to be approximately equal, that is, p in =p inv Therefore, in order to obtain the high grid-side input power factor, the reference value of the q-axis current after the harmonic is injected in step S2 of this embodiment is It can be expressed as:

[0077]

[0078] Among them, 2θ g Indicates that the frequency is 100Hz. Based on the above expression, it can be seen that the reference value I given to the q-axis current q0 Q-axis current reference value after harmonic injection Contains DC and 100Hz components.

[0079] When using the reference value after q-axis current injection harmonics and d-axis current given reference value I d0 When the system is controlled, the output torque of the motor becomes a pulsating quantity with an amplitude twice that of the load torque and a frequency twice that of the grid frequency. In addition, due to insufficient bus voltage margin and dq axis current distortion, the actual output torque pulsation is more serious. Figure 3 shown.

[0080] In order to suppress torque pulsation, in step S3 of this embodiment, the reference value after the d-axis current is injected with harmonics is Designed for:

[0081]

[0082] In the formula, I d0 Indicates the d-axis current reference value The DC component, I d2 and I d4are the 100Hz cosine component amplitude and 200Hz cosine component amplitude in the current harmonic respectively. Then the motor output torque T out It can be expressed as:

[0083]

[0084] In the formula, n p is the number of motor pole pairs. g , 4θ g and 6θ g Corresponding to 100Hz, 200Hz and 300Hz respectively, it can be seen that the output torque contains DC component, 100Hz component, 200Hz component and 300Hz component, and the effective value of each component T edc , T e1 , T e2 and T e3 The expressions are:

[0085]

[0086] In the above output torque expression, T e1 , T e2 and t e3 In order to conveniently describe the degree of torque pulsation, in this embodiment, the degree of torque pulsation is defined as the proportion of the effective value of the pulsation amount in the output torque to the effective value of the total component of the output torque, that is:

[0087]

[0088] Among them, Rate f Indicates the degree of torque pulsation. Based on the above expression, the torque pulsation degree Rate can be obtained f The 100Hz cosine component amplitude I in the d-axis current harmonic d2 and the 200Hz cosine component amplitude I d4 Determine the torque pulsation rate f The 100Hz cosine component amplitude I in the d-axis current harmonic d2 and the 200Hz cosine component amplitude I d4 The surface relationship diagram of Figure 4 As shown. Figure 4 It can be seen that through I d2 and I d4 The control can realize the control of torque pulsation degree.

[0089] Based on the expression of torque pulsation degree, this embodiment further defines the proportion of DC component Rate dc for:

[0090]

[0091] In order to minimize the output torque pulsation, it is necessary to make Rate f Minimum,Rate dc Maximum. Consider I d4 =0, let Rate dc to I d2 The derivative is:

[0092]

[0093] In the formula, C = B + AI d0 For built-in permanent magnet synchronous motors, A<0, in order to meet the requirements of field weakening control, I d0 <0, C=B+AI d0 >0. At the same time, due to the maximum current limit, is also less than 0. Therefore, Rate dc to I d2 The derivative of is always less than 0, that is, Rate dc With I d2 The increase of is monotonically decreasing. In order to make Rate dc Maximum, I d2 As small as possible.

[0094] Then, let Rate dc to I d4 The derivative is:

[0095]

[0096] In the formula, The corresponding torque DC component should be greater than 0, and the Rate can be derived dc There is a maximum value, at which I d4 The values ​​are:

[0097]

[0098] In summary, considering the current limitation of the motor, in order to minimize the motor torque pulsation, I d2 and I d4 The values ​​are:

[0099] I d2 =σI d0

[0100]

[0101] Where σ and τ are proportional coefficients and satisfy 0<σ<1, -1<τ<0.

[0102] After the current harmonic injection is determined based on the above method, the q-axis current reference value and d-axis current reference value The expression can achieve a high power factor while effectively suppressing the motor output torque pulsation.

[0103] In step S4 of this embodiment, for the collected three-phase current i a 、i b 、i c By performing Clark transformation, the three-phase current can be converted into the α-axis feedback current i α and β-axis feedback current i β ; for i α and i β By performing park transformation, the α-axis feedback current i α and the β-axis feedback current i β Converted to d-axis feedback current i d and q-axis feedback current i q .

[0104] In step S5 of this embodiment, the motor d-axis feedforward decoupling voltage and the motor q-axis feedforward decoupling voltage It can be obtained by decoupling the d and q axes of the motor voltage equation. Specifically, It is expressed as:

[0105]

[0106]

[0107] Among them, i d is the motor d-axis feedback current, i q is the motor q-axis feedback current, ω e is the motor electrical angular velocity.

[0108] In order to further improve the grid-side current quality and the power factor of the motor, this embodiment further introduces feedforward power correction to compensate for the difference between the actual inverter power and the ideal grid-side input power. Specifically, in step S6 of this embodiment, according to the α-axis voltage reference value and β-axis voltage reference value Generate PWM signals for each switch in the inverter, including:

[0109] Calculate the ideal grid-side input power p in The difference between the actual inverter power and the feedforward compensation power p cmp ;The actual inverter power is: is the d-axis reference voltage, is the q-axis reference voltage, and accordingly, the feedforward compensation power is

[0110] according to Calculate the α-axis feedforward compensation voltage Δu α_ff and β-axis feedforward compensation voltage Δu β_ff ;

[0111] The α-axis voltage reference value and β-axis voltage reference value Respectively with the α-axis feedforward compensation voltage Δu α_ff and β-axis feedforward compensation voltage Δu β_ff Add together to get the actual α-axis voltage reference value and the actual β-axis voltage reference value

[0112] The actual α-axis voltage reference value and the actual β-axis voltage reference value Perform SVPWM modulation to obtain the PWM signal of each switch tube in the inverter.

[0113] In general, this embodiment injects current harmonics into the given reference value of the q-axis current to make the inverter power equal to the ideal grid-side input power, and injects current harmonics into the given reference value of the d-axis current to minimize the torque pulsation in the motor output torque. Without adding additional hardware, the torque pulsation can be effectively suppressed and the power factor can be improved. On this basis, the quality of the grid-side current can be further improved and the power factor can be improved through feedforward power correction.

[0114] The beneficial effects that can be achieved by this embodiment are further explained below in conjunction with specific control examples.

[0115] Figure 5 This is a comparison diagram of the change in the motor output torque when the conventional control method is switched to the torque pulsation suppression method provided in this embodiment. It can be seen that when switching to the control method proposed in the present invention, the torque pulsation degree Rate f It dropped from 0.62587 to 0.58411, and the output torque pulsation of the motor was significantly suppressed.

[0116] Figure 6 The following is a comparison chart of the Fourier analysis of the grid-side current when the torque pulsation suppression method provided in this embodiment is used and the IEC-61000-3-2 harmonic current limit standard. It can be seen that by using the method provided in this embodiment, the harmonics of the grid-side current can meet the IEC-61000-3-2 harmonic standard, and the grid-side input power factor can reach above 0.98. This shows that this embodiment can effectively improve the quality of the grid-side current and improve the power factor.

[0117] Embodiment 2:

[0118] A torque pulsation suppression device for a permanent magnet synchronous motor without electrolytic capacitor based on current harmonic injection, such as Figure 2 As shown, it includes: a speed controller, a weak magnetic controller, a dq axis current reference generation module, a current sampling module, a current loop controller, a voltage conversion module and a modulation module;

[0119] The speed controller has a first input terminal for inputting the motor's given speed. Its second input terminal is used to input the actual motor speed ω m , which is used to set the motor speed in the current cycle and the actual motor speed ω m The difference between them is PI regulated to obtain the given reference value I of the q-axis current q0 ;

[0120] The first input of the weak magnetic controller is used to input the stator voltage vector u given in the previous cycle. S The second input terminal is used to input the inverter output voltage limit u max , which is used to convert the stator voltage vector u given in the previous cycle into S and the inverter output voltage limit u max The difference between them is averaged and then PI adjustment is performed to obtain the d-axis current reference value I d0 ;

[0121] The dq axis current reference generation module has a first input terminal connected to the output terminal of the speed controller, and a second input terminal connected to the output terminal of the weak magnetic controller, which is used to make the inverter power p inv Equal to the ideal grid-side input power p in As the target, the reference value I is given for the q-axis current q0 Perform harmonic injection to obtain the q-axis current reference value The dq axis current reference generation module is also used to set a reference value I for the d axis current with the goal of minimizing the torque ripple of the motor output torque. d0 Perform harmonic injection to obtain the d-axis current reference value

[0122] The current sampling module is connected to the motor to collect the three-phase current of the motor and convert the three-phase current into the α-axis feedback current i through Clark transformation. α and the β-axis feedback current i β Then, the α-axis feedback current u is converted into α and β-axis feedback current u β Converted to d-axis feedback current i d and q-axis feedback current i q ;

[0123] The current loop controller has a first input terminal connected to the output terminal of the dq axis current reference generation module, a second input terminal connected to the output terminal of the current sampling module, and a third input terminal for receiving the motor d axis feedforward decoupling voltage and the motor q-axis feedforward decoupling voltage It is used for the d-axis current reference value and the d-axis feedback current i d After PI control, the motor d-axis feedforward decoupling voltage Add together to get the d-axis voltage reference value And the q-axis current reference value With the q-axis feedback current i q After PI control, the motor q-axis feedforward decoupling voltage Add together to get the q-axis voltage reference value

[0124] The voltage conversion module has an input end connected to the output end of the current loop controller, which is used to convert the d-axis voltage reference value and q-axis voltage reference value Transformed into α-axis voltage reference value and β-axis voltage reference value

[0125] The modulation module has an input end connected to the output end of the voltage conversion module, which is used to modulate the voltage according to the α-axis voltage reference value. and β-axis voltage reference value Generate PWM signals for controlling each switch in the inverter to complete the control of the current cycle;

[0126] Among them, the ideal grid-side input power p in It is the grid-side input power when the grid-side power factor is maximum.

[0127] Furthermore, the torque pulsation suppression device for a permanent magnet synchronous motor without electrolytic capacitor based on current harmonic injection provided in this embodiment further includes: a feedforward power correction module arranged between the voltage conversion module and the modulation module;

[0128] The feedforward power correction module has a first input terminal for receiving the ideal grid-side input power p in Its second input terminal is used to receive the actual inverter power, its third input terminal is connected to the output terminal of the voltage conversion module, and its output terminal is connected to the input terminal of the modulation module, which is used to calculate the ideal grid-side input power p in The difference between the actual inverter power and the feedforward compensation power p cmp ,according to Calculate the α-axis feedforward compensation voltage Δu α_ff and β-axis feedforward compensation voltage Δuβ_ff , and the α-axis voltage reference value and the β-axis voltage reference

[0129] value Respectively with the α-axis feedforward compensation voltage Δu α_ff and β-axis feedforward compensation voltage Δu β_ff Add together to get the actual α-axis voltage reference value and the actual β-axis voltage reference value

[0130] Furthermore, the modulation module is used to adjust the actual α-axis voltage reference value and the actual β-axis voltage reference value Perform SVPWM modulation to obtain the PWM signal of each switch tube in the inverter.

[0131] In this embodiment, the specific implementation of each module can refer to the description in the above embodiment 1 and will not be repeated here.

[0132] Embodiment 3:

[0133] A permanent magnet synchronous motor system without an electrolytic capacitor includes: a permanent magnet synchronous motor without an electrolytic capacitor, and a torque pulsation suppression device for the permanent magnet synchronous motor without an electrolytic capacitor based on current harmonic injection provided in the above-mentioned embodiment 2.

[0134] In this embodiment, the connection relationship between the electrolytic capacitor-free permanent magnet synchronous motor and the current harmonic injection-based torque pulsation suppression device for the electrolytic capacitor-free permanent magnet synchronous motor is as follows: Figure 2 shown.

[0135] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for suppressing torque ripple of a permanent magnet synchronous motor without electrolytic capacitor based on current harmonic injection, characterized in that: The following steps are involved: S1: In the current cycle, the motor is given a speed and the actual motor speed ω m The difference between them is PI regulated to obtain the given reference value I of the q-axis current q0 , and the stator voltage vector u given in the previous cycle S and the inverter output voltage limit u max The difference between them is averaged and then PI adjustment is performed to obtain the d-axis current reference value I d0 ; S2: so that the inverter power p inv Equal to the ideal grid-side input power p in As the target, the reference value I is given for the q-axis current q0 Perform harmonic injection to obtain the q-axis current reference value The ideal grid-side input power p in The grid-side input power when the grid-side power factor is the largest; S3: To minimize the torque ripple of the motor output torque, a reference value I is given to the d-axis current. d0 Perform harmonic injection to obtain the d-axis current reference value S4: Collect the three-phase current of the motor and convert it to obtain the d-axis feedback current i d and q-axis feedback current i q ; S5: Reference value for d-axis current and the d-axis feedback current i d After PI control, the motor d-axis feedforward decoupling voltage Add together to get the d-axis voltage reference value Reference value for q-axis current With the q-axis feedback current i q After PI control, the motor q-axis feedforward decoupling voltage Add together to get the q-axis voltage reference value S6: Set the d-axis voltage reference value and q-axis voltage reference value Transformed into α-axis voltage reference value and β-axis voltage reference value According to the α-axis voltage reference value and β-axis voltage reference value Generate PWM signals for controlling each switch in the inverter to complete the control of the current cycle.

2. The method for suppressing torque ripple of a permanent magnet synchronous motor without electrolytic capacitor based on current harmonic injection as claimed in claim 1, characterized in that: Among them, θ g Indicates the phase angle of the grid voltage.

3. The method for suppressing torque ripple of a permanent magnet synchronous motor without electrolytic capacitor based on current harmonic injection as claimed in claim 2, characterized in that: Among them, I d0 Indicates the d-axis current reference value The DC component, I d2 Indicates the amplitude of the 100Hz cosine component in the current harmonics, I d4 Indicates the amplitude of the 200Hz cosine component in the current harmonics.

4. The method for suppressing torque ripple of a permanent magnet synchronous motor without electrolytic capacitor based on current harmonic injection as claimed in claim 3, characterized in that: I d2 =σI d0 in, n p is the number of motor pole pairs, L d is the motor d-axis inductance, L q is the motor q-axis inductance, is the permanent magnet flux of the motor; σ and τ are proportional coefficients, and they satisfy 0<σ<1, -1<τ<0.

5. The method for suppressing torque ripple of a permanent magnet synchronous motor without electrolytic capacitor based on current harmonic injection according to any one of claims 1 to 4, characterized in that: In step S6, according to the α-axis voltage reference value and β-axis voltage reference value Generate PWM signals for each switch in the inverter, including: Calculate the ideal grid-side input power p in The difference between the actual inverter power and the feedforward compensation power p cmp ; according to Calculate the α-axis feedforward compensation voltage Δu α_ff and β-axis feedforward compensation voltage Δu β_ff ; The α-axis voltage reference value and β-axis voltage reference value Respectively with the α-axis feedforward compensation voltage Δu α_ff and β-axis feedforward compensation voltage Δu β_ff Add together to get the actual α-axis voltage reference value and the actual β-axis voltage reference value The actual α-axis voltage reference value and the actual β-axis voltage reference value Perform SVPWM modulation to obtain the PWM signal of each switch tube in the inverter; Among them, i α is the α-axis feedback current, i β is the β-axis feedback current.

6. A torque pulsation suppression device for a permanent magnet synchronous motor without electrolytic capacitor based on current harmonic injection, characterized in that: include: Speed ​​controller, magnetic field weakening controller, dq axis current reference generation module, current sampling module, current loop controller, voltage conversion module and modulation module; The first input terminal of the speed controller is used to input the given speed of the motor. Its second input terminal is used to input the actual motor speed ω m , which is used to set the motor speed in the current cycle and the actual motor speed ω m The difference between them is PI regulated to obtain the given reference value I of the q-axis current q0 ; The first input terminal of the weak magnetic controller is used to input the stator voltage vector u given in the previous cycle. S The second input terminal is used to input the inverter output voltage limit u max , which is used to convert the stator voltage vector u given in the previous cycle into S and the inverter output voltage limit u max The difference between them is averaged and then PI adjustment is performed to obtain the d-axis current reference value I d0 ; The dq axis current reference generation module has a first input end connected to the output end of the speed controller, and a second input end connected to the output end of the weak magnetic controller, which is used to make the inverter power p inv Equal to the ideal grid-side input power p in As the target, the reference value I is given for the q-axis current q0 Perform harmonic injection to obtain the q-axis current reference value The dq axis current reference generation module is also used to set a reference value I for the d axis current with the goal of minimizing the torque ripple of the motor output torque. d0 Perform harmonic injection to obtain the d-axis current reference value The current sampling module is connected to the motor and is used to collect the three-phase current of the motor and convert the three-phase current into the α-axis feedback current i through Clark transformation. α and the β-axis feedback current i β Then, the α-axis feedback current i is converted into α and the β-axis feedback current i β Converted to d-axis feedback current i d and q-axis feedback current i q ; The current loop controller has a first input terminal connected to the output terminal of the dq axis current reference generation module, a second input terminal connected to the output terminal of the current sampling module, and a third input terminal for receiving the motor d axis feedforward decoupling voltage and the motor q-axis feedforward decoupling voltage It is used for the d-axis current reference value and the d-axis feedback current i d After PI control, the motor d-axis feedforward decoupling voltage Add together to get the d-axis voltage reference value And the reference value of q-axis current With the q-axis feedback current i q After PI control, the motor q-axis feedforward decoupling voltage Add together to get the q-axis voltage reference value The voltage conversion module, whose input end is connected to the output end of the current loop controller, is used to convert the d-axis voltage reference value and q-axis voltage reference value Transformed into α-axis voltage reference value and β-axis voltage reference value The modulation module, whose input end is connected to the output end of the voltage conversion module, is used to convert the voltage according to the α-axis voltage reference value. and β-axis voltage reference value Generate PWM signals for controlling each switch in the inverter to complete the control of the current cycle; Among them, the ideal grid-side input power p in It is the grid-side input power when the grid-side power factor is maximum.

7. The torque pulsation suppression device for a permanent magnet synchronous motor without electrolytic capacitor based on current harmonic injection as claimed in claim 6, characterized in that: Also includes: A feedforward power correction module disposed between the voltage conversion module and the modulation module; The feedforward power correction module has a first input terminal for receiving the ideal grid-side input power p in , whose second input end is used to receive the actual inverter power, whose third input end is connected to the output end of the voltage conversion module, whose output end is connected to the input end of the modulation module, and which is used to calculate the ideal grid-side input power p in The difference between the actual inverter power and the feedforward compensation power p cmp ,according to Calculate the α-axis feedforward compensation voltage Δu α_ff and β-axis feedforward compensation voltage Δu β_ff , and the α-axis voltage reference value and β-axis voltage reference value Respectively with the α-axis feedforward compensation voltage Δu α_ff and β-axis feedforward compensation voltage Δu β_ff Add together to get the actual α-axis voltage reference value and the actual β-axis voltage reference value Furthermore, the modulation module is used to adjust the actual α-axis voltage reference value and the actual β-axis voltage reference value Perform SVPWM modulation to obtain the PWM signal of each switch tube in the inverter.

8. A permanent magnet synchronous motor system without electrolytic capacitor, characterized in that: include: A permanent magnet synchronous motor without electrolytic capacitor, and a torque pulsation suppression device for a permanent magnet synchronous motor without electrolytic capacitor based on current harmonic injection as described in claim 6 or 7.

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