Method and device for suppressing torque ripple of permanent magnet synchronous motor without electrolytic capacitor based on current harmonic injection

Abstract

The application discloses a current harmonic injection-based torque ripple suppression method and device for a permanent magnet synchronous motor without an electrolytic capacitor, and belongs to the field of permanent magnet synchronous motor control. q0 Harmonic injection is performed to obtain a q-axis current reference value d0 Harmonic injection is performed to obtain a d-axis current reference value PI control is performed on the difference between the d-axis and q-axis current reference values and the d-axis and q-axis feedback currents respectively, and then the d-axis and q-axis voltage reference values are obtained by adding the d-axis and q-axis feedforward structure voltages, the d-axis and q-axis voltage reference values are converted into alpha-axis and beta-axis voltage reference values, and PWM signals for controlling each switch tube in the inverter are generated. The application can effectively reduce the torque ripple of the output torque without increasing the cost of additional hardware, and simultaneously realizes a high input power factor.

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 capacitors based on current harmonic injection. Background Art

[0002] Interior permanent magnet synchronous motors (IPMS) are widely used in industries such as automotive and aerospace due to their high power density, low energy consumption, and simple structure. Traditional PMS drive systems use large electrolytic capacitors with capacitances of hundreds or thousands of microfarads to stabilize the DC link voltage and power the inverter. However, the bulk of these capacitors limits the lifespan of the inverter circuit. Furthermore, to improve power factor and reduce grid-side harmonic pollution, power factor correction (PFC) circuits must be added, which increases power losses and adds weight and cost to the motor drive system.

[0003] To address these issues, researchers have developed an electrolytic capacitor-free motor drive system. This topology uses thin-film capacitors of a few microfarads instead of large-capacity electrolytic capacitors as busbar capacitors, significantly reducing the size of the motor drive system. Furthermore, by eliminating the PFC circuit, the efficiency and reliability of the drive system are improved. Furthermore, since the busbar capacitor capacity is significantly reduced, the busbar voltage fluctuates with the grid voltage. Due to the enhanced coupling between the grid input and the inverter output, properly controlling the inverter output power can improve the grid-side current performance.

[0004] However, due to the sharp fluctuations in bus voltage, the q-axis current will also fluctuate sharply, resulting in severe output torque pulsation. Torque pulsation can cause mechanical vibration, increased noise, increased speed fluctuations, and reduced efficiency in the motor. To address the torque pulsation problem in electrolytic capacitor-free motor drive systems, the main current approach is to change the topology. The paper "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 systems. The DSC is connected in parallel to the DC link as an energy buffer, providing an additional voltage source for the system. This measure effectively reduces bus voltage fluctuations and motor torque pulsation, while also improving efficiency. The paper "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 is used to suppress load power pulsation. This system can achieve significant torque pulsation suppression.

[0005] The existing method of achieving torque pulsation suppression by changing the topology can effectively improve the torque pulsation problem of the permanent magnet synchronous motor without electrolytic capacitors. However, due to the use of additional hardware circuits, the size and cost of the system will increase. Summary of the Invention

[0006] In response to the defects of the existing technology 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 capacitors based on current harmonic injection. The purpose is to effectively reduce the torque pulsation of the output torque of the electrolytic capacitor-free 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 q-axis current reference value I 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 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 maximum;

[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 into the d-axis feedback current i d and q-axis feedback current i q ;

[0012] S5: Reference value of 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 of q-axis current and 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 Converted to 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] Furthermore, 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 ripple suppression device for a permanent magnet synchronous motor without electrolytic capacitors based on current harmonic injection, comprising: a speed controller, a 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 q-axis current reference value I 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 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 give a reference value I to 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 β-axis feedback current i β, and the α-axis feedback current i α and the β-axis feedback current i β are converted into the d-axis feedback current i d and the q-axis feedback current i q .

[0035] a current loop controller, a first input end of the current loop controller being connected with an output end of the dq-axis current reference generation module, a second input end of the current loop controller being connected with an output end of the current sampling module, and a third input end of the current loop controller being used for receiving the motor d-axis feedforward decoupling voltage and the motor q-axis feedforward decoupling voltage , and the difference between the d-axis current reference value and the d-axis feedback current i d is subjected to PI control, and then the d-axis voltage reference value is obtained by adding the motor d-axis feedforward decoupling voltage , and the difference between the q-axis current reference value and the q-axis feedback current i q is subjected to PI control, and then the q-axis voltage reference value is obtained by adding the motor q-axis feedforward decoupling voltage .

[0036] a voltage transformation module, an input end of the voltage transformation module being connected with an output end of the current loop controller, and the voltage transformation module being used for transforming the d-axis voltage reference value and the q-axis voltage reference value into the α-axis voltage reference value and the β-axis voltage reference value .

[0037] a modulation module, an input end of the modulation module being connected with an output end of the voltage transformation module, and the modulation module being used for generating PWM signals for controlling each switch tube in the inverter according to the α-axis voltage reference value and the β-axis voltage reference value , so as to complete the control in a current period.

[0038] wherein the ideal grid-side input power p in is the grid-side input power when the grid-side power factor is maximum.

[0039] Further, the electrolytic capacitor-free permanent magnet synchronous motor torque ripple suppression device based on current harmonic injection provided by the present application further comprises a feedforward power correction module arranged between the voltage transformation module and the modulation module.

[0040] a first input end of the feedforward power correction module being used for receiving the ideal grid-side input power p ina second input end for receiving an actual inverter power, a third input end connected with an output end of the voltage conversion module, and an output end connected with an input end of the modulation module, and used for calculating an ideal grid-side input power p in a difference between the actual inverter power and the ideal grid-side input power, to obtain a feedforward compensation power p cmp , according to an α-axis feedforward compensation voltage Δu α_ff and a β-axis feedforward compensation voltage Δu β_ff , and adding the α-axis voltage reference value and the β-axis voltage reference value to the α-axis feedforward compensation voltage Δu α_ff and the β-axis feedforward compensation voltage Δu β_ff respectively, to obtain an actual α-axis voltage reference value and an actual β-axis voltage reference value

[0041] and the modulation module is used for performing SVPWM modulation on the actual α-axis voltage reference value and the actual β-axis voltage reference value to obtain PWM signals of each switch tube in the inverter.

[0042] According to still another aspect of the present application, there is provided a non-electrolytic capacitor permanent magnet synchronous motor system, comprising: a non-electrolytic capacitor permanent magnet synchronous motor, and the above-mentioned non-electrolytic capacitor permanent magnet synchronous motor torque ripple suppression device based on current harmonic injection provided by the present application.

[0043] Overall, the above technical solutions conceived by the present application can achieve the following beneficial effects:

[0044] (1) The present application performs current harmonic injection on the 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 the given reference value of the d-axis current, so that the torque ripple in the motor output torque is minimized, without the need to increase additional hardware, thereby effectively suppressing the torque ripple and improving the power factor.

[0045] (2) The present application further introduces feedforward power correction on the basis of current harmonic injection, and compensates 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 DRAWINGS

[0046] Figure 1 is a topological structure diagram of an existing non-electrolytic capacitor 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 capacitors based on current harmonic injection provided by an embodiment of the present invention;

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

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

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

[0051] Figure 6 After adopting the torque ripple 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, as well as the grid-side input power factor diagram. DETAILED DESCRIPTION

[0052] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining 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 may 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 and are not necessarily used to describe a specific order or sequence.

[0054] Electrolytic capacitor-free 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 The system consists of a single-phase uncontrolled rectifier bridge, an inverter, and a permanent magnet synchronous motor. The voltage source provides power for the entire system; the grid-side inductor filters the grid-side current; the uncontrolled rectifier bridge rectifies the grid-side AC voltage source into rectified power; thin-film capacitors absorb harmonics and power the inverter; and the inverter receives pulse signals from the control system to convert DC power into AC power, providing three-phase power for the permanent magnet synchronous motor.

[0055] To overcome the deficiency of existing methods for suppressing torque pulsation in electrolytic capacitor-free motor systems, which require additional hardware circuits, the present invention provides a method and device for suppressing torque pulsation in electrolytic capacitor-free permanent magnet synchronous motors based on current harmonic injection. The overall concept is as follows: Based on the operating characteristics of electrolytic capacitor-free permanent magnet synchronous motors, the relationship between the pulsation amount in the motor output torque and the dq axis current is derived and analyzed, and the q axis current expression that optimizes the power factor and the optimal d axis current expression for suppressing torque pulsation are obtained. Therefore, based on appropriate current harmonic injection, effective suppression of the motor output torque pulsation can be achieved without adding any additional hardware circuits. On this basis, the grid-side current quality is improved through power correction, further improving the power factor.

[0056] The following are examples.

[0057] Example 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 q-axis current reference value I 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 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 maximum;

[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 into the d-axis feedback current i d and q-axis feedback current i q ;

[0063] S5: Reference value of 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 of q-axis current and 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 Converted to 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 sensor, 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 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] Under ideal conditions, 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 as approximately equal, that is, p in =p inv Therefore, in order to obtain a high grid-side input power factor, the reference value of the q-axis current after harmonic injection 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, we can know that the reference value I is given for 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. Moreover, due to insufficient bus voltage margin and dq axis current distortion, the actual output torque pulsation is even 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 to:

[0081]

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

[0083]

[0084] Where, 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 To facilitate the characterization of the degree of torque pulsation, in this embodiment, the degree of torque pulsation is defined as the ratio 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 rate can be obtained f The 100Hz cosine component amplitude I in the d-axis current harmonics d2 and the 200Hz cosine component amplitude I d4 Determine the torque ripple rate f The 100Hz cosine component amplitude I in the d-axis current harmonics 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 of torque pulsation can be realized.

[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 the Rate f Minimum,Rate dc Maximum. Consider I d4 =0, let Rate dc to I d2 Taking the derivative we get:

[0092]

[0093] Where 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 monotonically decreases, in order to make Rate dc Maximum, I d2 As small as possible.

[0094] Then, let Rate dc to I d4 Taking the derivative we get:

[0095]

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

[0097]

[0098] In summary, considering the current limitation of the motor, in order to minimize the motor torque ripple, the design of 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 Clark transformation can be performed to convert the three-phase current into the α-axis feedback current i α and β-axis feedback current i β ; for i α and i β Perform park transformation to convert the α-axis feedback current i α and 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, 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 summary, this embodiment injects current harmonics into the q-axis current reference value to ensure that the inverter power is equal to the ideal grid-side input power. It also injects current harmonics into the d-axis current reference value to minimize torque ripple in the motor output torque. This effectively suppresses torque ripple and improves the power factor without adding additional hardware. Furthermore, feedforward power correction can further improve grid-side current quality and enhance the power factor.

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

[0115] Figure 5 The figure is a comparison of the transformation of the motor output torque when the traditional control method is switched to the torque pulsation suppression method provided by this embodiment. It can be seen that when switching to the control method proposed by the present invention, the torque pulsation rate is reduced. f It dropped from 0.62587 to 0.58411, and the output torque pulsation of the motor was significantly suppressed.

[0116] Figure 6 This figure compares the Fourier analysis of the grid-side current when using the torque ripple suppression method provided by this embodiment with the IEC-61000-3-2 harmonic current limit standard. It can be seen that using the method provided by this embodiment, the grid-side current harmonics can meet the IEC-61000-3-2 harmonic standard, and the grid-side input power factor can reach above 0.98. This demonstrates that this embodiment can effectively improve the grid-side current quality and power factor.

[0117] Example 2:

[0118] A torque ripple suppression device for a permanent magnet synchronous motor without electrolytic capacitors 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 q-axis current reference value I 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 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 give a reference value I to 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 β-axis feedback current i β Then, the α-axis feedback current u is converted to 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 to set 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 and 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 terminal connected to the output terminal of the current loop controller, which is used to convert the d-axis voltage reference value and q-axis voltage reference value Converted to α-axis voltage reference value and β-axis voltage reference value

[0125] The modulation module, whose input end is connected to the output end of the voltage conversion module, 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 the switches 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 ripple suppression device for a permanent magnet synchronous motor without electrolytic capacitors based on current harmonic injection provided by this embodiment further includes: a feedforward power correction module provided 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 alpha-axis voltage reference value and the beta-axis voltage reference

[0129] value respectively added with the alpha-axis feed-forward compensation voltage Δu α_ff and the beta-axis feed-forward compensation voltage Δu β_ff , to obtain the actual alpha-axis voltage reference value and the actual beta-axis voltage reference value

[0130] And, a modulation module is configured to perform SVPWM modulation on the actual alpha-axis voltage reference value and the actual beta-axis voltage reference value to obtain PWM signals of each switch tube in the inverter.

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

[0132] Embodiment 3

[0133] A system of electrolytic capacitor-free permanent magnet synchronous motor, comprising: an electrolytic capacitor-free permanent magnet synchronous motor, and the electrolytic capacitor-free permanent magnet synchronous motor torque ripple suppression device based on current harmonic injection provided in the above-described embodiment 2.

[0134] In the embodiment, the connection relationship between the electrolytic capacitor-free permanent magnet synchronous motor and the electrolytic capacitor-free permanent magnet synchronous motor torque ripple suppression device based on current harmonic injection is specifically as shown in Figure 2 .

[0135] Those skilled in the art can easily understand that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

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 q-axis current reference value I 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 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 maximum; 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 into the d-axis feedback current i d and q-axis feedback current i q ; S5: Reference value of d-axis current and 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 of q-axis current and 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 Converted to 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 according to 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 according to 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 according to 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 ripple suppression device for a permanent magnet synchronous motor without electrolytic capacitors 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 q-axis current reference value I q0 ; The first input terminal of the magnetic field weakening 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 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 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 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 β-axis feedback current i β Then, the α-axis feedback current i is converted to α and 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 to set the d-axis current reference value and 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 and 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 Converted to 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 the switches 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 ripple suppression device for a permanent magnet synchronous motor without electrolytic capacitors based on current harmonic injection according to claim 6, characterized in that: Also includes: A feedforward power correction module provided 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 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 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 capacitors, and a torque pulsation suppression device for a permanent magnet synchronous motor without electrolytic capacitors based on current harmonic injection as described in claim 6 or 7.

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