Method for suppressing bus capacitor ripple current of permanent magnet synchronous motor driver based on virtual admittance reshaping

Abstract

The application discloses a bus capacitor ripple current suppression method for a permanent magnet synchronous motor driver based on virtual admittance remodeling, and belongs to the technical field of permanent magnet synchronous motor control. The application aims at the problem that the tolerance of capacitor ripple current is reduced after the bus capacitor of the permanent magnet synchronous motor driver is reduced. The application comprises the following steps: based on the principle of constant heat generation, a target suppression rate of a capacitor power grid double-frequency ripple current is determined; a system admittance model after the bus capacitor is reduced is established, and the amplitude and phase parameters of a virtual admittance are designed in combination with the target suppression rate; a direct current component and a power grid double-frequency component of a bus voltage are determined, and corresponding motor-side injected power is calculated in combination with the amplitude and phase parameters of the virtual admittance; d-axis and q-axis admittance voltage vectors are superposed on d-axis and q-axis reference voltage vectors, and alpha-axis and beta-axis voltage reference vectors are calculated; and control signals of an inverter are obtained through an SVPWM link. The application is used for suppressing the bus capacitor power grid double-frequency ripple current.

Description

TECHNICAL FIELD

[0001] The application relates to a bus capacitor ripple current suppression method for a permanent magnet synchronous motor driver based on virtual admittance remodeling and belongs to the technical field of permanent magnet synchronous motor control. BACKGROUND

[0002] The permanent magnet synchronous motor is widely applied to the air conditioner compressor field due to its simple structure, large power density, wide speed regulation range, good speed regulation performance and many other advantages. In order to reduce the adverse effects on the power grid during air conditioner operation, the air conditioner compressor driver is usually composed of a rectifier, a power factor correction (PFC) converter and an inverter. The PFC converter can improve the power factor at the grid side and reduce the harmonic content of the input current at the grid side. A bus electrolytic capacitor is usually arranged between the PFC converter and the inverter, and the main function of the bus electrolytic capacitor is to stabilize the bus voltage and absorb the current ripple. By reducing the bus electrolytic capacitor, the system cost can be significantly reduced and the power density can be improved. However, the equivalent series resistance (ESR) of the small electrolytic capacitor is larger, and the tolerance to the ripple current is poorer, which reduces the reliability and stability of the driving system. Therefore, the suppression of the bus capacitor ripple current of the permanent magnet synchronous motor driver needs further research.

[0003] At present, the bus capacitor ripple current suppression method for the permanent magnet synchronous motor driver mainly includes three methods, namely, the compensation unit parallel connection method, the rectifier harmonic injection method and the inverter harmonic injection method. The compensation unit parallel connection method realizes energy buffering and suppresses the ripple current of the bus capacitor by connecting a hardware compensation unit in parallel with the bus. This method needs to increase additional hardware, and the implementation cost is high. The rectifier harmonic injection method injects harmonics at the grid side to reduce the input power fluctuation, thereby suppressing the ripple current of the bus capacitor. This method needs to sacrifice the power quality at the grid side, and the ripple current suppression effect is limited. The inverter harmonic injection method injects harmonics in the motor current loop to increase the output power fluctuation, thereby suppressing the ripple current of the bus capacitor. Due to the difficulty of the PI controller in tracking the harmonic injection amount without static error, there is a large gap between the ripple current suppression rate and the design value. Therefore, for the permanent magnet synchronous motor driving system, it is of great significance to study a low-cost capacitor ripple current suppression method with obvious suppression effect. SUMMARY

[0004] In view of the problem that the tolerance of the capacitor ripple current is reduced after the bus capacitor of the permanent magnet synchronous motor driver is reduced, the application provides a bus capacitor ripple current suppression method for a permanent magnet synchronous motor driver based on virtual admittance remodeling.

[0005] The bus capacitor ripple current suppression method for a permanent magnet synchronous motor driver based on virtual admittance remodeling provided by the application comprises the following steps.

[0006] Step one: taking the bus capacitor reduction before and after the capacitor power grid two times frequency ripple current heating does not increase as the suppression standard, according to the change of bus capacitor equivalent series resistance to determine the target suppression rate of capacitor power grid two times frequency ripple current;

[0007] Step two: establish the bus capacitor reduction system admittance model, combined with the target suppression rate design virtual admittance amplitude and phase parameters;

[0008] Step three: determine the bus voltage DC component and power grid two times frequency component, combined with the virtual admittance amplitude and phase parameters to calculate the corresponding motor side injection power;

[0009] Step four: according to the motor side injection power and stator d, q axis current vector to calculate d, q axis admittance voltage vector;The d, q axis admittance voltage vector is superimposed on the d, q axis reference voltage vector, and then the inverse Park transformation is carried out to obtain the α, β axis voltage reference vector;According to the α, β axis voltage reference vector through the SVPWM link to obtain the control signal of the inverter, realize the suppression of capacitor power grid two times frequency ripple current.

[0010] According to the permanent magnet synchronous motor drive bus capacitor ripple current suppression method based on virtual admittance remodeling of the application, in step one, the target suppression rate of capacitor power grid two times frequency ripple current is expressed as A T :

[0011]

[0012] In the formula, R C0 Is the equivalent series resistance of the original electrolytic capacitor before the bus capacitor is reduced, and R C Is the equivalent series resistance of the small electrolytic capacitor after the bus capacitor is reduced.

[0013] According to the permanent magnet synchronous motor drive bus capacitor ripple current suppression method based on virtual admittance remodeling of the application, in step two, the amplitude and phase parameters of the virtual admittance are designed as follows:

[0014] Establish the system admittance model including the motor side and the small electrolytic capacitor;

[0015] Based on the system admittance model, the transfer function of the diode current to the small electrolytic capacitor current in the drive before and after the suppression method is established, and the expression of the capacitor ripple current suppression rate is obtained;

[0016] Design virtual admittance, combine the target suppression rate and the capacitor ripple current suppression rate, and determine the amplitude and phase parameters of the virtual admittance when the virtual admittance amplitude is minimum;

[0017] The driver comprises a rectifier, a boost power factor correction circuit, a small electrolytic capacitor C and an inverter; the boost power factor correction circuit comprises a boost inductor L, a switch tube S and a diode D,

[0018] The positive output end of the rectifier is connected to one end of the boost inductor L, the other end of the boost inductor L is connected to the collector of the switch tube S, and the emitter of the switch tube S is connected to the negative output end of the rectifier; the other end of the boost inductor L is also connected to the anode of the diode D, the cathode of the diode D is connected to the positive electrode of the small electrolytic capacitor C, and the negative electrode of the small electrolytic capacitor C is connected to the negative output end of the rectifier; the inverter is connected in parallel with the small electrolytic capacitor C.

[0019] According to the bus capacitor ripple current suppression method for the permanent magnet synchronous motor driver based on the virtual admittance remodeling provided by the application, the system admittance model in step two comprises a motor side input admittance model and a small electrolytic capacitor admittance model:

[0020]

[0021] Y (s) = 1 / (R + sL), wherein Y m (s) is the motor side input admittance, s is a frequency domain operator, I inv is the inverter input current DC component, U dc is the bus voltage DC component, T s is the inverter switching period, U dc_e is the equivalent sampling bus voltage DC component, R s is the motor stator resistance, L d is the motor d-axis inductance, U dref is the motor d-axis reference voltage DC component, G d is the transfer function of the motor d-axis current regulator, ω e is the rotor electric angular velocity, L q is the motor q-axis inductance, U qref is the motor q-axis reference voltage DC component, G q is the transfer function of the motor q-axis current regulator, I d is the motor d-axis current DC component, U d is the motor d-axis voltage DC component, I q is the motor q-axis current DC component, U q is the motor q-axis voltage DC component;

[0022]

[0023] Y (s) = 1 / (R + sL), wherein Y C (s) is the small electrolytic capacitor admittance.

[0024] According to the bus capacitor ripple current suppression method of the permanent magnet synchronous motor driver based on virtual admittance remodeling of the application, ignoring the inverter loss, at the grid double frequency, the transfer function G(jω2) from the front diode current to the small electrolytic capacitor current enabled by the suppression method is:

[0025]

[0026] In the formula, j is the imaginary unit, and ω2 is the double grid angular frequency;

[0027] Ignoring the inverter loss, at the grid double frequency, the transfer function G(jω2) from the back diode current to the small electrolytic capacitor current enabled by the suppression method is: v

[0028]

[0029] In the formula, Y v is the virtual admittance in parallel with the motor and the small electrolytic capacitor.

[0030] According to the bus capacitor ripple current suppression method of the permanent magnet synchronous motor driver based on virtual admittance remodeling of the application, the expression of the virtual admittance Y v is:

[0031] Y v (jω2)=|Y v |cosθ v +j|Y v |sinθ v ,

[0032] In the formula, |Y v | represents the amplitude of the virtual admittance, and θ v represents the phase of the virtual admittance.

[0033] According to the bus capacitor ripple current suppression method of the permanent magnet synchronous motor driver based on virtual admittance remodeling of the application, the capacitor ripple current suppression rate is represented as A:

[0034]

[0035] A and A T are equal, |Y v | and θ v are determined.

[0036] According to the bus capacitor ripple current suppression method of the permanent magnet synchronous motor driver based on virtual admittance remodeling of the application, in step three, the motor side injected power p v is:

[0037] p v =Y v (jω2)u dc2 U​dc ,

[0038] wherein u dc2 is the grid double frequency component of bus voltage.

[0039] In the step four, the calculation method of the d, q axis admittance voltage vector in the bus capacitor ripple current suppression method for permanent magnet synchronous motor driver based on virtual admittance remodeling according to the application is:

[0040]

[0041] wherein u v_dref is the d axis admittance voltage vector, u v_qref is the q axis admittance voltage vector, i d is the motor d axis current vector, and i q is the motor q axis current vector.

[0042] In the bus capacitor ripple current suppression method for permanent magnet synchronous motor driver based on virtual admittance remodeling according to the application, the grid double frequency component u dc2 of the bus voltage is obtained through a second-order band-pass filter, and the transfer function H(s) of the second-order band-pass filter is:

[0043]

[0044] wherein ω n represents the center angular frequency, is set as 200π rad / s, and ξ represents the damping ratio, is set as 0.05, and the corresponding bandwidth is 10 Hz.

[0045] The bus capacitor ripple current suppression method for permanent magnet synchronous motor driver based on virtual admittance remodeling according to the application has the following beneficial effects: the method relates to the bus capacitor ripple current suppression of the permanent magnet synchronous motor driver, and can improve the problem that the electrolytic capacitor ripple current tolerance is reduced when the bus capacitor is reduced. Based on the principle that the heat does not change, the target suppression rate of the secondary ripple current is determined according to the change of the ESR after the bus capacitor is reduced, and the virtual admittance parameter is designed on this basis. The motor side injection power is calculated according to the bus voltage and the virtual admittance parameter, and the corresponding d, q axis admittance voltage vector is obtained in combination with the d, q axis current vector. The d, q axis admittance voltage vector is superimposed on the original d, q axis reference voltage vector for control, a high admittance path of the diode secondary ripple current to the motor side is constructed, and the effective suppression of the capacitor ripple current is realized.

[0046] The virtual impedance technology is applied to the bus capacitor ripple current suppression, and the problem that the ripple suppression effect of the traditional strategy is limited by the controller bandwidth can be solved. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1is the overall block diagram of the motor driver controlled by the bus capacitor ripple current suppression method for permanent magnet synchronous motor driver based on virtual admittance remodeling according to the application; D1, D2, D3 and D4 in the figure are four diodes in the rectifier, u g is the grid-side input voltage, u r is the rectifier output voltage, i L is the boost inductor current, i D is the diode current, u dc is the bus voltage, i C is the small electrolytic capacitor current, i inv is the inverter current, i a , i b are a-phase current and b-phase current respectively, and PMSM is a permanent magnet synchronous motor; BPF is a second-order band-pass filter, i v is a virtual admittance current, and LPF is a low-pass filter, ω eref is a motor rotor electric angular velocity reference value, u αref and u βref are α-axis reference voltage and β-axis reference voltage respectively, i α and i β are α-axis current and β-axis current respectively, i dref and i qref are d-axis reference current and q-axis reference current respectively, θ e is a motor rotor position angle, and PI is a proportional integral controller, u dref , u qref are d-axis reference voltage and q-axis reference voltage respectively, S abc is a control signal of the inverter,

[0048] Figure 2 is the capacitor ripple current suppression rate under different virtual admittance amplitude and phase parameters, and k θv represents the unit value of the virtual admittance phase, and the base value is 2π;

[0049] Figure 3 is the experimental comparison waveform diagram before and after enabling the method under the rated power condition, and i C2 represents the secondary ripple current of the small electrolytic capacitor;

[0050] Figure 4 is Figure 3 the amplification experimental comparison waveform diagram before and after enabling the method;

[0051] Figure 5 is Figure 4 the FFT analysis comparison result diagram of the small electrolytic capacitor current before and after enabling the method;

[0052] Figure 6 is the experimental waveform diagram before enabling the method when the rated power changes in the range of 0.3-0.5 times, and Pg Represents the DC component of grid-side power;

[0053] Figure 7 The waveform diagram is an experimental waveform diagram after enabling the method when the power varies within the range of 0.3-0.5 times the rated power.

[0054] Figure 8 This is a comparison chart of the amplitude of the capacitor's secondary ripple current before and after enabling the method under different power conditions. Detailed Implementation

[0055] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0057] The present invention will be further described below with reference to the accompanying drawings, but this should not be construed as limiting the invention.

[0058] Combination Figure 1 As shown, this invention provides a method for suppressing bus capacitor ripple current in a permanent magnet synchronous motor driver based on virtual admittance reshaping, comprising:

[0059] Step 1: Using the fact that the heating of the second harmonic ripple current in the capacitor grid does not increase before and after the bus capacitance is reduced as the suppression standard, determine the target suppression rate of the second harmonic ripple current in the capacitor grid based on the change in the equivalent series resistance of the bus capacitance.

[0060] Step 2: Establish a system admittance model after reducing the bus capacitance, and design the amplitude and phase parameters of the virtual admittance based on the target suppression rate;

[0061] Step 3: Determine the DC component and the second harmonic component of the bus voltage, and calculate the corresponding motor-side injected power by combining the amplitude and phase parameters of the virtual admittance;

[0062] Step 4: Calculate the d-axis and q-axis admittance voltage vectors based on the injected power on the motor side and the stator d-axis and q-axis current vectors; superimpose the d-axis and q-axis admittance voltage vectors onto the d-axis and q-axis reference voltage vectors, and then perform an inverse Park transformation to obtain the α-axis and β-axis voltage reference vectors; based on the α-axis and β-axis voltage reference vectors, obtain the inverter control signal through the SVPWM stage to suppress the second-harmonic ripple current of the capacitor grid.

[0063] The embodiment is based on the principle of constant heat generation, determines the target suppression rate of the capacitor ripple current according to the change of the equivalent series resistance (ESR) after the bus capacitor is reduced, and then designs the virtual admittance parameter according to the target suppression rate of the capacitor ripple current. On the basis of the virtual admittance parameter, the motor-side injected power is solved in combination with the bus voltage; finally, the control signal of the inverter is obtained, and the suppression of the capacitor ripple current is realized.

[0064] Further, in step one, the target suppression rate of the capacitor ripple current is calculated according to the change of the ESR before and after the bus capacitor is reduced, and the target suppression rate of the capacitor grid double-frequency ripple current is represented as A T :

[0065]

[0066] In the formula, R C0 is the equivalent series resistance of the original electrolytic capacitor before the bus capacitor is reduced, and R C is the equivalent series resistance of the small electrolytic capacitor after the bus capacitor is reduced.

[0067] In step two, the amplitude and phase parameter design method of the virtual admittance is:

[0068] The system admittance model including the motor side and the small electrolytic capacitor is established;

[0069] Based on the system admittance model, the transfer functions of the diode current to the small electrolytic capacitor current in the driver before and after the suppression method is enabled are established respectively, and the expression of the capacitor ripple current suppression rate is obtained;

[0070] The virtual admittance is designed, the amplitude and phase parameters of the virtual admittance when the amplitude of the virtual admittance is the smallest are determined in combination with the target suppression rate and the capacitor ripple current suppression rate;

[0071] The driver includes a rectifier, a boost power factor correction (PFC) circuit, a small electrolytic capacitor C and an inverter; the boost power factor correction circuit includes a boost inductor L, a switch tube S and a diode D,

[0072] The positive output end of the rectifier is connected to one end of the boost inductor L, the other end of the boost inductor L is connected to the collector of the switch tube S, and the emitter of the switch tube S is connected to the negative output end of the rectifier; the other end of the boost inductor L is also connected to the anode of the diode D, the cathode of the diode D is connected to the positive electrode of the small electrolytic capacitor C, and the negative electrode of the small electrolytic capacitor C is connected to the negative output end of the rectifier; the inverter is connected in parallel with the small electrolytic capacitor C.

[0073] In step two of the embodiment, the system admittance model includes a motor-side input admittance model and a small electrolytic capacitor admittance model:

[0074]

[0075] where Y m (s) is the motor-side input admittance, s is the frequency domain operator, I inv is the inverter input current DC component, U dc is the bus voltage DC component, T s is the inverter switching period, U dc_e is the equivalent sampled bus voltage DC component, R s is the motor stator resistance, L d is the motor d-axis inductance, U dref is the motor d-axis reference voltage DC component, G d is the transfer function of the motor d-axis current regulator, ω e is the rotor electrical angular speed, L q motor q-axis inductance, U qref is the motor q-axis reference voltage DC component, G q is the transfer function of the motor q-axis current regulator, I d is the motor d-axis current DC component, U d is the motor d-axis voltage DC component, I q is the motor q-axis current DC component, U q is the motor q-axis voltage DC component;

[0076]

[0077] where Y C (s) is the small electrolytic capacitor admittance.

[0078] Neglecting inverter losses, the suppression method enables the transfer function G(jω2) from the pre-diode current to the small electrolytic capacitor current at the grid double frequency to be:

[0079]

[0080] where j is the imaginary unit and ω2 is the double grid angular frequency;

[0081] Neglecting inverter losses, the suppression method enables the transfer function G v (jω2) from the post-diode current to the small electrolytic capacitor current at the grid double frequency to be:

[0082]

[0083] where Y v is the virtual admittance in parallel with the motor and the small electrolytic capacitor.

[0084] Further, the expression of the virtual admittance Y v is:

[0085] Y v (jω2) = |Y v |cosθ v +j|Y v |sinθ v ,

[0086] where |Y v | represents the amplitude of the virtual admittance, θ v represents the phase of the virtual admittance.

[0087] The capacitor ripple current suppression rate is represented as A:

[0088]

[0089] A and A T are made equal, |Y v | and θ v are determined.

[0090] Further, in combination with the schematic shown in Figure 2 , according to the capacitor ripple current suppression rate and the target suppression rate, the virtual admittance amplitude corresponding to the minimum virtual admittance amplitude and the phase parameter can be obtained.

[0091] In step three, the motor-side injected power p v is:

[0092] p v =Y v (jω2)u dc2 U dc ,

[0093] where u dc2 is the grid double-frequency component of the bus voltage.

[0094] In step four, in order to reduce the burden of the d, q-axis current controllers, the admittance voltage vector is made to be in the same direction as the motor stator current vector, and the calculation method of the d, q-axis admittance voltage vector is:

[0095]

[0096] where u v_dref is the d-axis admittance voltage vector, u v_qref is the q-axis admittance voltage vector, i d is the motor d-axis current vector, and i q is the motor q-axis current vector.

[0097] In this embodiment, the grid double-frequency component u dc2 of the bus voltage is obtained through a second-order band-pass filter, and the transfer function H(s) of the second-order band-pass filter is:

[0098]

[0099] In the formula ω n The center angular frequency is represented by 200π rad / s, and ξ represents the damping ratio, which is set to 0.05, corresponding to a bandwidth of 10 Hz.

[0100] For the motor vector control section, combined with Figure 1 As shown, a dual closed-loop control method is adopted, consisting of an outer speed loop and an inner current loop. Both the speed controller and the current controller are PI controllers. The motor speed ω is obtained through a position observer. e and rotor position angle θ e The d-axis current i is obtained through Clark transformation and Park transformation. d and q-axis current i q The reference value of rotational speed ω eref With the speed feedback value ω e The difference is subtracted, and the result is used by the speed PI regulator to generate the q-axis current reference value i in the current loop. qref Set the q-axis current reference value i qref With q-axis current feedback value i q Subtraction is performed, and the q-axis voltage setpoint u is generated by the current PI regulator. qref Similarly, the d-axis current reference value i dref With d-axis current feedback value i d Subtraction is performed, and the d-axis voltage setpoint u is generated by the current PI regulator. dref The d-axis and q-axis admittance voltage vector u v_dref and u v_qref They are respectively superimposed onto the original d-axis and q-axis reference voltage vectors u dref and u qref Then, after inverse Park transformation, the corresponding α and β axis voltage reference vectors u are obtained. αref and u βref Then, the inverter drive signal S is generated through SVPWM. abc Ultimately, this achieves the suppression of bus capacitor ripple current.

[0101] Example:

[0102] The effectiveness of the proposed method for suppressing bus capacitor ripple current of a permanent magnet synchronous motor driver based on virtual admittance reshaping is verified on an experimental platform of a permanent magnet compressor drive system using a boost PFC converter.

[0103] The experimental platform was configured with the following parameters: mains voltage 220Vrms, mains frequency 50Hz, bus voltage 350V, stator resistance 0.78Ω, direct-axis inductance 5.4mH, quadrature-axis inductance 8.4mH, rotor flux linkage 0.11Wb, number of pole pairs 3, and moment of inertia 0.0003kg·m.2 , rated power 1200W, controller bandwidth 200Hz. The original bus capacitor (1259.42 μF, 56.31 mΩ) was replaced by a smaller one (379.32 μF, 303.51 mΩ). The control algorithm was implemented by a R5F562T7DDF microcontroller of RENESAS RX62T series, and the inverter switching frequency was 10 kHz.

[0104] To verify the effectiveness of the suppression method of the application, the experimental comparison results of the motor running at rated power 1200W are shown in Figure 3 , Figure 4 and Figure 5 . It can be seen from Figure 3 and Figure 4 that the capacitor current and bus voltage fluctuation are significantly reduced after enabling the suppression method. It can be seen from Figure 5 that the amplitude of the capacitor secondary ripple current is 3.313A before enabling the suppression method, and the amplitude of the capacitor secondary ripple current is reduced to 1.398A after enabling the suppression strategy, and the suppression rate of the capacitor secondary ripple current is 0.578, which proves the effectiveness and feasibility of the method of the application.

[0105] To verify the effectiveness of the suppression method of the application under dynamic variable load conditions, the experimental comparison results of the motor running at 0.3-0.5 times rated power (360W-600W) are shown in Figure 6 and Figure 7 . It can be seen from Figure 6 that the capacitor current and bus voltage fluctuation increase with the increase of the grid-side power before enabling the suppression method. It can be seen from Figure 7 that the capacitor current and bus voltage fluctuation are significantly reduced after enabling the suppression method. Therefore, under dynamic variable load conditions, the method of the application can still effectively suppress the secondary ripple component of the capacitor current, and has good adaptability.

[0106] To further verify the effectiveness of the method of the application under different power conditions, experiments were carried out under the condition of 0.1-1 times rated power (120W-1200W) with a step of 120W. The capacitor current of ten cycles was analyzed by FFT, and the experimental results of the capacitor current secondary ripple component and the ripple suppression rate are shown in Figure 8 . It can be seen from Figure 8 that under different grid-side power conditions, the method of the application can achieve good secondary harmonic suppression effect.

[0107] While the application has been described with reference to particular embodiments thereof, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present application. It will be apparent to those skilled in the art that numerous modifications can be made within the scope of the present application as defined by the appended claims. It is intended that all such modification fall within the spirit and scope of the present application. It will be understood that the features described in connection with one embodiment can be used in connection with another embodiment.

Claims

1. A method for bus capacitor ripple current suppression of a permanent magnet synchronous motor drive based on virtual admittance reshaping, characterized in that Comprising, Step one: taking the bus capacitance reduction before and after the capacitor power grid two frequency ripple current heating does not increase as the inhibition standard, according to the bus capacitance equivalent series resistance of the change to determine the target inhibition rate of capacitor power grid two frequency ripple current; Step two: establish the bus capacitance reduction after the system admittance model, combined with the target inhibition rate design virtual admittance amplitude and phase parameters; Step three: determine the bus voltage DC component and power grid two frequency component, combined with the virtual admittance amplitude and phase parameters calculated to get the corresponding motor side injection power; Step four: according to the motor side injection power and stator d, q axis current vector calculation obtained d, q axis admittance voltage vector; The d, q axis admittance voltage vector is superimposed on the d, q axis reference voltage vector, and then the inverse Park transformation is carried out to obtain the α, β axis voltage reference vector; According to the α, β axis voltage reference vector through the SVPWM link to get the control signal of inverter, realize the inhibition of capacitor power grid two frequency ripple current.

2. The virtual admittance remodeling based bus capacitance ripple current suppression method of permanent magnet synchronous motor drive according to claim 1, characterized in that, In step one, the target suppression rate of the capacitor power grid double-frequency ripple current is represented as A T : where R C0 is the original electrolytic capacitor equivalent series resistance before bus capacitance reduction, R C is the small electrolytic capacitor equivalent series resistance after bus capacitance reduction.

3. The virtual admittance remodeling based bus capacitance ripple current suppression method of permanent magnet synchronous motor drive according to claim 2, characterized in that, In step two, the amplitude and phase parameter design method of virtual admittance is: Establish the system admittance model including the motor side and small electrolytic capacitor; Based on the system admittance model, the transfer function of diode current to small electrolytic capacitor current before and after the inhibition method is enabled is established respectively, and the expression of capacitor ripple current suppression rate is obtained; Design virtual admittance, combined with the target inhibition rate and the capacitor ripple current suppression rate, determine the amplitude and phase parameters of virtual admittance when the virtual admittance amplitude is minimum; The drive includes rectifier, boost power factor correction circuit, small electrolytic capacitor C and inverter; Boost power factor correction circuit includes boost inductor L, switch tube S and diode D, The positive output end of the rectifier is connected with one end of the boost inductor L, the other end of the boost inductor L is connected with the collector of the switch tube S, and the emitter of the switch tube S is connected with the negative output end of the rectifier; The other end of the boost inductor L is also connected with the anode of the diode D, the cathode of the diode D is connected with the positive electrode of the small electrolytic capacitor C, and the negative electrode of the small electrolytic capacitor C is connected with the negative output end of the rectifier; The inverter is connected with the small electrolytic capacitor C in parallel.

4. The virtual admittance remodeling based bus capacitance ripple current suppression method of permanent magnet synchronous motor drive according to claim 3, characterized in that, The system admittance model in step two includes motor side input admittance model and small electrolytic capacitor admittance model: where Y m (s) is the motor-side input admittance, s is the frequency domain operator, I inv is the inverter input current DC component, U dc is the bus voltage DC component, T s is the inverter switching period, U dc_e is the equivalent sampled bus voltage DC component, R s is the motor stator resistance, L d is the motor d-axis inductance, U dref is the motor d-axis reference voltage DC component, G d is the transfer function of the motor d-axis current regulator, ω e is the rotor electrical angular velocity, L q motor q-axis inductance, U qref is the motor q-axis reference voltage DC component, G q is the transfer function of the motor q-axis current regulator, I d is the motor d-axis current DC component, U d is the motor d-axis voltage DC component, I q is the motor q-axis current DC component, U q is the motor q-axis voltage DC component; wherein Y C (s) is a small electrolytic capacitor admittance.

5. The virtual admittance remodeling based bus capacitance ripple current suppression method of permanent magnet synchronous motor drive according to claim 4, characterized in that, Ignoring the inverter loss, at the power grid two frequency, the transfer function G(jω2) of diode current to small electrolytic capacitor current before and after the inhibition method is enabled is: In the formula, j is the imaginary unit, and ω2 is the two frequency of power grid angle frequency; Neglecting the inverter losses, the suppression method enables a transfer function G from the diode current to the small electrolytic capacitor current at the grid double frequency v (jω2) is: where Y v is the virtual admittance in parallel with the motor and the small electrolytic capacitor.

6. The method of claim 5, wherein the bus capacitor ripple current suppression method based on virtual admittance reshaping of permanent magnet synchronous motor drives is characterized by, Virtual admittance Y v The expression for the virtual admittance Y is: Y v (jω2) = |Y v |cosθ v +j|Y v |sinθ v , where |Y v | represents the magnitude of the virtual admittance, θ v represents the phase of the virtual admittance.

7. The method of claim 6, wherein the bus capacitor ripple current suppression method based on virtual admittance reshaping of permanent magnet synchronous motor drives is characterized by, The capacitor ripple current suppression rate is expressed as A: A and A T are equal, determine |Y v and θ v .

8. The method of claim 7, wherein the bus capacitor ripple current suppression method based on virtual admittance reshaping of permanent magnet synchronous motor drives is characterized by, In step three, the motor side injects power p v is: p v = Y v (jω2)u dc2 U dc , where u dc2 is the grid double frequency component of the bus voltage.

9. The method of claim 8, wherein the bus capacitor ripple current suppression method based on virtual admittance reshaping of permanent magnet synchronous motor drives is characterized by, The calculation method of d, q-axis admittance voltage vector in step four is: where u v_dref is the d-axis admittance voltage vector, u v_qref is the q-axis admittance voltage vector, i d is the motor d-axis current vector, i q is the motor q-axis current vector.

10. The method of claim 9, wherein the bus capacitor ripple current suppression method based on virtual admittance reshaping of permanent magnet synchronous motor drives is characterized by, Grid double frequency component u of the bus voltage dc2 is obtained by a second order band pass filter whose transfer function H(s) is where ω n represents the center angular frequency, set to 200π rad / s, and ξ represents the damping ratio, set to 0.05, corresponding to a bandwidth of 10 Hz.

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