Permanent magnet synchronous motor driver bus capacitor ripple current suppression method based on virtual admittance remodeling

Abstract

The invention discloses a virtual admittance remodeling-based bus capacitor ripple current suppression method for a permanent magnet synchronous motor driver, and belongs to the technical field of permanent magnet synchronous motor control. The method aims at solving the problem that after the bus capacitance of the permanent magnet synchronous motor driver is reduced, the capacitance ripple current endurance capacity is reduced. Comprising the following steps: determining a target suppression ratio of a capacitor power grid frequency doubling ripple current based on a heating invariant principle; establishing a system admittance model after the bus capacitance is reduced, and designing the amplitude and phase parameters of virtual admittance in combination with the target suppression ratio; determining a direct current component and a power grid frequency doubling component of the bus voltage, and calculating corresponding motor side injection power by combining the amplitude and the phase parameter of the virtual admittance; d-axis and q-axis admittance voltage vectors are calculated and superposed on the d-axis and q-axis reference voltage vectors, and alpha-axis and beta-axis voltage reference vectors are obtained through calculation; and a control signal of the inverter is obtained through an SVPWM link. The method is used for suppressing the double-frequency ripple current of the bus capacitor power grid.

Description

Technical Field

[0001] The present invention relates to a method for suppressing the ripple current of the bus capacitor of a permanent magnet synchronous motor drive based on virtual admittance reshaping, and belongs to the technical field of permanent magnet synchronous motor control. Background Art

[0002] Due to many advantages such as simple structure, high power density, wide speed regulation range, and good speed regulation performance, permanent magnet synchronous motors are widely used in the field of air conditioner compressors. To reduce the adverse effects on the power grid during air conditioner operation, an air conditioner compressor drive usually consists of a rectifier, a power factor correction (PFC) converter, and an inverter. The PFC converter can improve the power factor on the grid side and reduce the harmonic content of the grid side input current. Between the PFC converter and the inverter, a bus electrolytic capacitor is usually set, and its main function is to stabilize the bus voltage and absorb 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 a small electrolytic capacitor is larger, and its tolerance to ripple current is worse, which will reduce the reliability and stability of the drive system. Therefore, further research is needed on the suppression of the ripple current of the bus capacitor of a permanent magnet synchronous motor drive.

[0003] At present, the methods for suppressing the ripple current of the bus capacitor of a permanent magnet synchronous motor drive are mainly divided into three types: the compensation unit parallel method, the rectifier harmonic injection method, and the inverter harmonic injection method. The compensation unit parallel method realizes energy buffering and suppresses the ripple current of the bus capacitor by paralleling a hardware compensation unit on the bus. This method requires adding additional hardware, and the implementation cost is relatively high. The rectifier harmonic injection method injects harmonics on 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 on the grid side, and the ripple current suppression effect is limited. The inverter harmonic injection method injects harmonics into the motor current loop to increase the output power fluctuation, thereby suppressing the ripple current of the bus capacitor. Since it is difficult for the PI controller to track the harmonic injection amount without static error, there is a large gap between the ripple current suppression rate and the design value. Therefore, for a permanent magnet synchronous motor drive system, it is of great significance to study a capacitor ripple current suppression method with low cost and obvious suppression effect. Summary of the Invention

[0004] Aiming at the problem that the tolerance of the ripple current of the bus capacitor decreases after the bus capacitor of the permanent magnet synchronous motor drive is reduced, the present invention provides a method for suppressing the ripple current of the bus capacitor of the permanent magnet synchronous motor drive based on virtual admittance reshaping.

[0005] A method for suppressing the ripple current of the bus capacitor of a permanent magnet synchronous motor drive based on virtual admittance reshaping according to the present invention includes

[0006] Step 1: Taking the non - increase of the heating caused by the double - frequency ripple current of the capacitor grid before and after the reduction of the bus capacitor as the suppression standard, determine the target suppression rate of the double - frequency ripple current of the capacitor grid according to the change of the equivalent series resistance of the bus capacitor;

[0007] Step 2: Establish a system admittance model after the reduction of the bus capacitor, and design the amplitude and phase parameters of the virtual admittance in combination with the target suppression rate;

[0008] Step 3: Determine the DC component and the double - frequency component of the grid of the bus voltage, and calculate the corresponding injected power on the motor side in combination with the amplitude and phase parameters of the virtual admittance;

[0009] Step 4: Calculate the d - axis and q - axis admittance voltage vectors according to 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 on the d - axis and q - axis reference voltage vectors, and then perform the inverse Park transformation to obtain the α - axis and β - axis voltage reference vectors; obtain the control signal of the inverter through the SVPWM link based on the α - axis and β - axis voltage reference vectors to achieve the suppression of the double - frequency ripple current of the capacitor grid.

[0010] According to the method for suppressing the bus capacitor ripple current of a permanent - magnet synchronous motor drive based on virtual - admittance reshaping of the present invention, in Step 1, the target suppression rate of the double - frequency ripple current of the capacitor grid is expressed as A T :

[0011]

[0012] where R C0 is the equivalent series resistance of the original electrolytic capacitor before the reduction of the bus capacitor, and R C is the equivalent series resistance of the small electrolytic capacitor after the reduction of the bus capacitor.

[0013] According to the method for suppressing the bus capacitor ripple current of a permanent - magnet synchronous motor drive based on virtual - admittance reshaping of the present invention, in Step 2, the design method of the amplitude and phase parameters of the virtual admittance is as follows:

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

[0015] Based on the system admittance model, establish the transfer function from the diode current to the small - electrolytic - capacitor current in the drive before and after enabling the suppression method respectively, and obtain the expression of the capacitor ripple current suppression rate;

[0016] Design the virtual admittance, and in combination with the target suppression rate and the capacitor ripple current suppression rate, determine the amplitude and phase parameters of the virtual admittance when the amplitude of the virtual admittance is the smallest;

[0017] The driver includes a rectifier, a boost power factor correction circuit, a small electrolytic capacitor C, and an inverter; the boost power factor correction circuit includes a boost inductor L, a switching transistor S, and a diode D.

[0018] The positive output terminal 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 switching transistor S, and the emitter of the switching transistor S is connected to the negative output terminal 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 terminal of the rectifier; the inverter is connected in parallel with the small electrolytic capacitor C.

[0019] According to the method for suppressing the bus capacitor ripple current of the permanent magnet synchronous motor driver based on virtual admittance reshaping of the present invention, in step two, the system admittance model includes a motor-side input admittance model and a small electrolytic capacitor admittance model:

[0020]

[0021] Where Y m (s) is the motor-side input admittance, s is the frequency-domain operator, I inv is the DC component of the inverter input current, U dc is the DC component of the bus voltage, T s is the inverter switching period, U dc_e is the equivalent sampled DC component of the bus voltage, R s is the motor stator resistance, L d is the motor d-axis inductance, U dref is the DC component of the motor d-axis reference voltage, 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 DC component of the motor q-axis reference voltage, G q is the transfer function of the motor q-axis current regulator, I d is the DC component of the motor d-axis current, U d is the DC component of the motor d-axis voltage, I q is the DC component of the motor q-axis current, U q is the DC component of the motor q-axis voltage;

[0022]

[0023] Where Y C (s) is the small electrolytic capacitor admittance.

[0024] According to the method for suppressing the bus capacitor ripple current of a permanent magnet synchronous motor drive based on virtual admittance reshaping of the present invention, ignoring the inverter loss, at the second harmonic frequency of the power grid, the transfer function G(jω2) from the diode current to the small electrolytic capacitor current before enabling the suppression method is:

[0025]

[0026] where j is the imaginary unit and ω2 is the second harmonic angular frequency of the power grid;

[0027] Ignoring the inverter loss, at the second harmonic frequency of the power grid, the transfer function G v (jω2) from the diode current to the small electrolytic capacitor current after enabling the suppression method is:

[0028]

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

[0030] According to the method for suppressing the bus capacitor ripple current of a permanent magnet synchronous motor drive based on virtual admittance reshaping of the present invention, the expression of the virtual admittance Y v is:

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

[0032] where |Y v | represents the magnitude of the virtual admittance and θ v represents the phase of the virtual admittance.

[0033] According to the method for suppressing the bus capacitor ripple current of a permanent magnet synchronous motor drive based on virtual admittance reshaping of the present invention, the capacitor ripple current suppression rate is expressed as A:

[0034]

[0035] Making A and A T equal to determine |Y v | and θ v .

[0036] According to the method for suppressing the bus capacitor ripple current of a permanent magnet synchronous motor drive based on virtual admittance reshaping of the present invention, in step three, the injected power p v on the motor side is:

[0037] p v = Y v (jω2)u dc2 Udc ,

[0038] where \(u\) dc2 is the double - frequency component of the grid voltage of the busbar.

[0039] According to the method for suppressing the bus - bar capacitor ripple current of a permanent - magnet synchronous motor drive based on virtual admittance reshaping of the present invention, the calculation method of the d - axis and q - axis admittance voltage vectors in step four is as follows:

[0040]

[0041] 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 d - axis current vector of the motor, \(i\) q is the q - axis current vector of the motor.

[0042] According to the method for suppressing the bus - bar capacitor ripple current of a permanent - magnet synchronous motor drive based on virtual admittance reshaping of the present invention, the double - frequency component \(u\) dc2 of the bus - bar voltage is obtained through a second - order band - pass filter. The transfer function \(H(s)\) of the second - order band - pass filter is:

[0043]

[0044] where \(\omega\) n represents the center angular frequency, which is set to \(200\pi\ rad / s\), and \(\xi\) represents the damping ratio, which is set to \(0.05\), corresponding to a bandwidth of \(10\ Hz\).

[0045] Advantages of the present invention: The method of the present invention relates to suppressing the ripple current of the bus - bar capacitor of a permanent - magnet synchronous motor drive, and can improve the problem that the ripple - current tolerance of the electrolytic capacitor decreases when the bus - bar capacitor decreases. Based on the principle of constant heat generation, the target suppression rate of the secondary ripple current is determined according to the change of the ESR after the bus - bar capacitor decreases, and the virtual admittance parameters are designed on this basis. The injected power on the motor side is calculated according to the bus - bar voltage and the virtual admittance parameters, and then combined with the d - axis and q - axis current vectors, the corresponding d - axis and q - axis admittance voltage vectors are obtained. By superimposing the d - axis and q - axis admittance voltage vectors on the original d - axis and q - axis reference voltage vectors for control, a high - admittance path from the diode secondary ripple current to the motor side is constructed to effectively suppress the capacitor ripple current.

[0046] The present invention applies the virtual impedance technology to suppress the ripple current of the bus - bar capacitor, which can solve the problem that the ripple suppression effect of the traditional strategy is limited by the controller bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1is the overall block diagram of controlling the motor driver by using the method for suppressing the bus capacitor ripple current of the permanent magnet synchronous motor driver based on virtual admittance reshaping described in the present invention; in the figure, D1, D2, D3, and D4 are respectively the 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 respectively the a-phase current and the b-phase current, PMSM is the permanent magnet synchronous motor; BPF is the second-order band-pass filter, i v is the virtual admittance current, LPF is the low-pass filter, ω eref is the reference value of the electrical angular velocity of the motor rotor, u αref and u βref are respectively the α-axis and β-axis reference voltages, i α and i β are respectively the α-axis current and the β-axis current, i dref and i qref are respectively the d-axis and q-axis reference currents, θ e is the motor rotor position angle, PI is the proportional-integral controller, u dref , u qref are respectively the d-axis and q-axis reference voltages, S abc is the control signal of the inverter,

[0048] Figure 2 is the capacitor ripple current suppression rate under different virtual admittance amplitude and phase parameter conditions, in the figure, k θv represents the per-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, in the figure, i C2 represents the secondary ripple current of the small electrolytic capacitor;

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

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

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

[0053] Figure 7 is the experimental waveform diagram after enabling the method when varying within the range of 0.3 - 0.5 times the rated power;

[0054] Figure 8 is the comparison result diagram of the amplitude of the second - order ripple current of the capacitor before and after enabling the method under different power conditions. Specific implementation manner

[0055] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0056] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0057] The present invention will be further described below in conjunction with the accompanying drawings, but it is not a limitation of the present invention.

[0058] Combined with Figure 1 as shown, the present invention provides a method for suppressing the ripple current of the bus capacitor of a permanent - magnet synchronous motor drive based on virtual admittance reshaping, including,

[0059] Step 1: Taking the non - increase of the heating of the double - frequency ripple current of the capacitor grid before and after the reduction of the bus capacitor as the suppression standard, determine the target suppression rate of the double - frequency ripple current of the capacitor grid according to the change of the equivalent series resistance of the bus capacitor;

[0060] Step 2: Establish a system admittance model after the reduction of the bus capacitor, and design the amplitude and phase parameters of the virtual admittance in combination with the target suppression rate;

[0061] Step 3: Determine the DC component and the double - frequency component of the grid of the bus voltage, and calculate the corresponding injected power on the motor side in combination with the amplitude and phase parameters of the virtual admittance;

[0062] Step 4: Calculate the d - axis and q - axis admittance voltage vectors according to 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 on the d - axis and q - axis reference voltage vectors, and then perform the inverse Park transformation to obtain the α - axis and β - axis voltage reference vectors; according to the α - axis and β - axis voltage reference vectors, obtain the control signals of the inverter through the SVPWM link to achieve the suppression of the double - frequency ripple current of the capacitor grid.

[0063] Based on the principle of constant heat generation, this embodiment 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; then designs the virtual admittance parameters according to the target suppression rate of the capacitor ripple current. On the basis of the virtual admittance parameters, the injected power on the motor side is solved in combination with the bus voltage; finally, the control signal of the inverter is obtained to achieve the suppression of the ripple current of the bus capacitor.

[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. The target suppression rate of the double-frequency ripple current of the capacitor power grid is expressed 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 design method of the amplitude and phase parameters of the virtual admittance is as follows:

[0068] Establish a system admittance model including the motor side and the small electrolytic capacitor;

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

[0070] Design the virtual admittance, and combine the target suppression rate and the capacitor ripple current suppression rate to determine the amplitude and phase parameters of the virtual admittance when the amplitude of the virtual admittance is the smallest;

[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 switching tube S, and a diode D.

[0072] The positive output terminal 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 switching tube S, and the emitter of the switching tube S is connected to the negative output terminal 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 terminal of the rectifier; the inverter is connected in parallel with the small electrolytic capacitor C.

[0073] The system admittance model in step two of this embodiment includes a motor side input admittance model and a small electrolytic capacitor admittance model:

[0074]

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

[0076]

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

[0078] Neglecting the inverter losses, at the second harmonic of the power grid, the transfer function G(jω2) from the diode current to the small electrolytic capacitor current before enabling the suppression method is:

[0079]

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

[0081] Neglecting the inverter losses, at the second harmonic of the power grid, the transfer function G v (jω2) from the diode current to the small electrolytic capacitor current after enabling the suppression method is:

[0082]

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

[0084] Furthermore, 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 magnitude of the virtual admittance, and θ v represents the phase of the virtual admittance.

[0087] The capacitance ripple current suppression rate is expressed as A:

[0088]

[0089] Make A and A T equal to determine |Y v | and θ v .

[0090] Furthermore, as shown in Figure 2 , the virtual admittance magnitude and phase parameters corresponding to the minimum virtual admittance magnitude can be obtained according to the capacitance ripple current suppression rate and the target suppression rate.

[0091] In step three, the injected power p on the motor side 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, to reduce the burden on the d- and q-axis current controllers, the admittance voltage vector is made to be in the same direction as the motor stator current vector. The calculation methods for the d- and q-axis admittance voltage vectors are:

[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 of the bus voltage dc2 is obtained through a second-order band-pass filter. The transfer function H(s) of the second-order band-pass filter is:

[0098]

[0099] where ω n represents the center angular frequency, set to 200π rad / s, ξ represents the damping ratio, set to 0.05, and the corresponding bandwidth is 10 Hz.

[0100] For the motor vector control part, combined with Figure 1 as shown, a double closed-loop control method with a speed loop outer loop and a current loop inner loop is adopted. The speed controller and the current controller are both PI controllers. The motor speed ω e and the rotor position angle θ e are obtained through a position observer. Through Clark transformation and Park transformation, the d-axis current i d and the q-axis current i q are obtained. Subtract the speed reference value ω eref from the speed feedback value ω e . The difference is passed through a speed PI regulator to generate the q-axis current reference value i qref of the current loop. Subtract the q-axis current reference value i qref from the q-axis current feedback value i q , and pass it through a current PI regulator to generate the q-axis voltage given value u qref ; similarly, subtract the d-axis current reference value i dref from the d-axis current feedback value i d , and pass it through a current PI regulator to generate the d-axis voltage given value u dref . Superimpose the d-axis and q-axis admittance voltage vectors u v_dref and u v_qref onto the original d-axis and q-axis reference voltage vectors u dref and u qref respectively, and then obtain the corresponding α-axis and β-axis voltage reference vectors u αref and u βref through inverse Park transformation, and then generate the drive signal S abc of the inverter through SVPWM, and finally achieve the suppression of the bus capacitor ripple current.

[0101] Example:

[0102] Next, verify the effectiveness of the method for suppressing the bus capacitor ripple current of the permanent magnet synchronous motor driver based on virtual admittance reshaping proposed by the present invention on the experimental platform of the permanent magnet compressor drive system using a boost PFC converter.

[0103] The parameters of the experimental platform are set as follows: grid voltage 220 Vrms, grid frequency 50 Hz, bus voltage 350 V, stator resistance 0.78 Ω, direct-axis inductance 5.4 mH, quadrature-axis inductance 8.4 mH, rotor flux 0.11 Wb, number of pole pairs 3, moment of inertia 0.0003 kg·m2 With a rated power of 1200W and a controller bandwidth of 200Hz. A smaller bus capacitor (379.32μF, 303.51mΩ) is used instead of the original bus capacitor (1259.42μF, 56.31mΩ). The control algorithm is executed by the R5F562T7DDF microcontroller of the Renesas RX62T series, and the inverter switching frequency is 10kHz.

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

[0105] To verify the effectiveness of the suppression method of the present invention under dynamic variable load conditions, the experimental comparison results when the motor operates at 0.3 - 0.5 times the rated power (360W - 600W) are as Figure 6 and Figure 7 shown. From Figure 6 , it can be seen that before enabling the suppression method, the capacitor current and the bus voltage fluctuation increase with the increase of the grid-side power. From Figure 7 , it can be seen that after enabling the suppression method, the capacitor current and the bus voltage fluctuation are significantly reduced. Therefore, under dynamic variable load conditions, the method of the present invention 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 present invention under different power conditions, experiments are carried out at 0.1 - 1 times the rated power (120W - 1200W) with a step of 120W. The FFT analysis of the capacitor current for ten cycles is performed, and the experimental results of the capacitor current secondary ripple component and the ripple suppression rate are as Figure 8 shown. From Figure 8 , it can be seen that under different grid-side power conditions, the method of the present invention can achieve good second-harmonic suppression effects.

[0107] Although the present invention has been described herein with reference to particular embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that numerous modifications may be made to the exemplary embodiments, and other arrangements may be devised, without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the different dependent claims and the features described herein may be combined in ways different from those described in the original claims. It should also be understood that the features described in connection with separate embodiments may be used in other described embodiments.

Claims

1. A method for suppressing bus capacitor ripple current of a permanent magnet synchronous motor drive based on virtual admittance reconstruction, characterized in that include, Step 1: Taking the fact that the heating of the capacitor grid double frequency ripple current does not increase before and after the bus capacitance is reduced as the suppression standard, determine the target suppression rate of the capacitor grid double frequency ripple current according to the change of the bus capacitance equivalent series resistance; Step 2: Establish a system admittance model after the bus capacitance is reduced, and design the amplitude and phase parameters of the virtual admittance in combination with the target suppression rate; Step 3: Determine the DC component of the bus voltage and the double frequency component of the power grid, and calculate the corresponding motor-side injection power in combination with the amplitude and phase parameters of the virtual admittance; Step 4: Calculate the d-axis and q-axis admittance voltage vectors based on the motor-side injected power and the stator d-axis and q-axis current vectors; The d and q axis admittance voltage vectors are superimposed on the d and q axis reference voltage vectors, and then the α and β axis voltage reference vectors are obtained by inverse Park transformation. The control signal of the inverter is obtained through the SVPWM link according to the α and β axis voltage reference vectors to achieve the suppression of the double frequency ripple current of the capacitor power grid.

2. The method for suppressing bus capacitor ripple current of a permanent magnet synchronous motor driver based on virtual admittance reconstruction according to claim 1 is characterized in that: In step 1, the target suppression rate of the capacitor grid double frequency ripple current is expressed as A T : Where R C0 is the equivalent series resistance of the original electrolytic capacitor before the busbar capacitance is reduced, R C It is the equivalent series resistance of the small electrolytic capacitor after the bus capacitance is reduced.

3. The method for suppressing bus capacitor ripple current of a permanent magnet synchronous motor driver based on virtual admittance reconstruction according to claim 2 is characterized in that: In step 2, the amplitude and phase parameter design method of the virtual admittance is: Establish a system admittance model including the motor side and small electrolytic capacitors; Based on the system admittance model, the transfer functions from the diode current to the small electrolytic capacitor current in the driver before and after the suppression method is enabled are established, and the expression of the capacitor ripple current suppression rate is obtained; Design a virtual admittance, and determine the amplitude and phase parameters of the virtual admittance when the amplitude of the virtual admittance is minimum by combining the target suppression rate and the capacitor ripple current suppression rate; The driver includes a rectifier, a boost power factor correction 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. 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.

4. The method for suppressing bus capacitor ripple current of a permanent magnet synchronous motor driver based on virtual admittance reconstruction according to claim 3 is characterized in that: The system admittance model in step 2 includes the motor side input admittance model and the small electrolytic capacitor admittance model: Where Y m (s) is the input admittance of the motor side, s is the frequency domain operator, I inv is the DC component of the inverter input current, U dc is the DC component of the bus voltage, T s is the inverter switching cycle, U dc_e is the DC component of the equivalent sampled bus voltage, R s is the motor stator resistance, L d is the motor d-axis inductance, U dref is the DC component of the motor d-axis reference voltage, 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 DC component of the motor q-axis reference voltage, G q is the transfer function of the motor q-axis current regulator, I d is the DC component of the motor d-axis current, U d is the DC component of the motor d-axis voltage, I q is the DC component of the motor q-axis current, U q is the DC component of the motor q-axis voltage; Where Y C (s) is the admittance of a small electrolytic capacitor.

5. The method for suppressing bus capacitor ripple current of a permanent magnet synchronous motor driver based on virtual admittance reconstruction according to claim 4 is characterized in that: Ignoring the inverter loss, at the grid double frequency, the transfer function G(jω2) from the diode current to the small electrolytic capacitor current before the suppression method is enabled is: Where j is an imaginary unit, ω2 is twice the grid angular frequency; Ignoring the inverter loss, at the grid double frequency, the transfer function G from the diode current to the small electrolytic capacitor current after the suppression method is enabled is v (jω2) is: Where Y v is a virtual admittance in parallel with the motor and the small electrolytic capacitor.

6. The method for suppressing bus capacitor ripple current of a permanent magnet synchronous motor driver based on virtual admittance reconstruction according to claim 5 is characterized in that: Virtual admittance Y v The expression is: AND v (jω2)=|Y v |cosθ v +j|Y v |sinθ v , Where |Y v | represents the magnitude of virtual admittance, θ v Represents the phase of the virtual admittance.

7. The method for suppressing bus capacitor ripple current of a permanent magnet synchronous motor driver based on virtual admittance reconstruction according to claim 6 is characterized in that: The capacitor ripple current suppression rate is expressed as A: Make A and A T Equal, OK |Y v | and θ v .

8. The method for suppressing bus capacitor ripple current of a permanent magnet synchronous motor driver based on virtual admittance reconstruction according to claim 7 is characterized in that: In step 3, the motor side injects power p v for: p v =Y v (jω2)u dc2 U dc , Where u dc2 It is the grid double frequency component of the bus voltage.

9. The method for suppressing bus capacitor ripple current of a permanent magnet synchronous motor driver based on virtual admittance reconstruction according to claim 8 is characterized in that: The calculation method of the d and q axis admittance voltage vectors in step 4 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 for suppressing bus capacitor ripple current of a permanent magnet synchronous motor driver based on virtual admittance reconstruction according to claim 9 is characterized in that: The grid double frequency component u of the bus voltage dc2 Obtained through a second-order bandpass filter, the transfer function H(s) of the second-order bandpass filter is: Where ω n represents the central angular frequency, which is set to 200πrad / s; ξ represents the damping ratio, which is set to 0.05, corresponding to a bandwidth of 10 Hz.

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