Extended variable observation method for voltage and current of permanent magnet motor

Abstract

A permanent magnet motor voltage and current extended variable observation method belongs to the field of motor control. Aiming at the problem that a permanent magnet synchronous motor with an LC filter is difficult to directly sample voltage and current on a motor side, the invention provides an extended variable observation method, the voltage and the current on the motor side are reconstructed by sampling current on an inverter side, and the reconstructed current on the motor side is used for feedback control of a current loop, so that the control performance of a system is improved. According to the method, observation errors caused by non-linear factors of the inverter are considered, the motor side voltage and the motor side current can be reconstructed with higher precision, only the inverter side current needs to be sampled, and hardware cost does not need to be increased.

Description

Technical Field

[0001] The invention relates to an extended variable observation method for voltage and current of a permanent magnet motor, and belongs to the field of motor control. Background Art

[0002] The stator of a permanent magnet synchronous motor (PMSM) driven by a voltage source inverter contains a large amount of current harmonics, which will generate large vibrations and noise. Currently, a common and effective method is to insert an LC filter in series between the inverter and the PMSM to filter out the current harmonics. Usually, the current sensor of the PMSM system is installed inside the controller, but due to the large size of the LC filter, it is difficult to integrate and install it inside the controller, making it difficult to sample the voltage and current on the motor side.

[0003] Many discussions have been conducted at home and abroad on the problem of current sampling position in PMSM systems. Among them, the method of reconstructing the motor side current by using the inverter side current with the help of an observer is simple and reliable, and does not require additional sensors. Many achievements have been made in the control of PMSM systems with LC filters. "Active Damping for LC-Filtered PMSM Based on Low-Pass Filter Capacitor Current Feedback and Extended State Observer" (see "IEEE Transactions on Transportation Electrification", 2024) realizes motor side current feedback control by establishing an extended state observer for the PMSM system with LC filter; "Current Control of Grid-Connected Inverter With LCL Filter Based on Extended-State Observer Estimations Using Single Sensor and Achieving Improved Robust Observation Dynamics" (see "IEEE Transactions on Industrial Electronics", 2017) completes the reconstruction of the grid side current by establishing an extended state observer for the grid system with LCL filter using the inverter side current. Summary of the invention

[0004] Aiming at the problem that it is difficult for a PMSM system with an LC filter to directly sample the voltage and current on the motor side, the present invention proposes an extended variable observation method for the voltage and current of a permanent magnet motor.

[0005] To implement the above method, the present invention adopts Figure 1 and 2 The control system shown in the figure is implemented, which includes an inverter, an LC filter, a permanent magnet synchronous motor, an abc-αβ module for three-phase static-two-phase static coordinate transformation, a back electromotive force calculation module, a motor voltage and current observation module, an αβ-dq module for two-phase static-two-phase rotating coordinate transformation, a current controller module, a dq-αβ module for two-phase rotating-two-phase static coordinate transformation, and a PWM module.

[0006] The system is divided into a power circuit and a control circuit. In the power circuit, the inverter outputs three-phase AC power, which is filtered by an LC filter and then fed to the permanent magnet synchronous motor. In the control circuit, the current output by the inverter is transformed by the abc-αβ module to obtain the inverter side current signal i of the α-axis and β-axis. invα,β The rotor position θ of the permanent magnet synchronous motor is given to the back electromotive force calculation module, which outputs the motor back electromotive force e of the α-axis and β-axis sα,β The inverter side current signal i of the α-axis and β-axis invα,β , α-axis and β-axis motor back electromotive force e sα,β The reference voltage u of the α-axis and β-axis output by the dq-αβ module α,βref As the input of the motor voltage and current observation module, the estimated motor side voltage of the α-axis and β-axis is output and motor side current The estimated α-axis and β-axis motor side currents output by the motor voltage and current observation module The estimated motor side currents of the d-axis and q-axis are obtained through coordinate transformation of the αβ-dq module The estimated d-axis and q-axis motor side currents The reference current i of the d-axis and q-axis d,qref The difference is calculated and the result is given to the current controller module to output the motor reference voltage u of the d-axis and q-axis d,qref ; The motor reference voltage u of the d-axis and q-axis d,qref The reference voltage u of the α-axis and β-axis is obtained by coordinate transformation of the dq-αβ module α,βref ; The reference voltage u of the α-axis and β-axis α,βref It is given to the PWM module, which outputs 6 PWM channels to control the on and off of the 6 switching tubes in the inverter.

[0007] The rotor position signal θ of the permanent magnet synchronous motor is given to the back electromotive force calculation module, and after calculation, the motor back electromotive force e of the α-axis and β-axis is outputsα,β ;

[0008] The current signal of the inverter i invx It is given to the abc-αβ module, and after calculation, the inverter side current signal i of the α-axis and β-axis is output invα,β ; Where x = a, b, c;

[0009] The inverter side current signal i of the α-axis and β-axis output by the abc-αβ module invα,β , the reference voltage u of the α-axis and β-axis output by the dq-αβ module α,βref , the motor back electromotive force e of the α-axis and β-axis output by the back electromotive force calculation module sα,β Provide the motor voltage and current observation module to reconstruct the motor side voltage and current;

[0010] The output of the motor voltage and current observation module is the estimated motor side voltage of the α-axis and β-axis and motor side current

[0011] The estimated α-axis and β-axis motor side currents output by the motor voltage and current observation module The motor rotor position θ is given to the αβ-dq module, and the estimated d-axis and q-axis motor side currents are output after calculation.

[0012] The current reference i of the d-axis and q-axis d,qref Subtract the estimated d-axis and q-axis motor side currents output by the αβ-dq module The calculation result is given to the current controller module, and the motor voltage reference u of the d-axis and q-axis is output after calculation d,qref ;

[0013] The motor voltage reference u of the d-axis and q-axis output by the current controller module d,qref The motor rotor position θ is given to the dq-αβ module, and the reference voltage u of the α-axis and β-axis is output after calculation. α,βref ;

[0014] The reference voltage u of the α-axis and β-axis output by the dq-αβ module α,βref It is given to the PWM module, and after calculation, 6 PWMs are output to control the on and off of the 6 switching tubes in the inverter.

[0015] The observation method in the motor voltage and current observation module is as follows:

[0016] In the two-phase stationary coordinate system, the state space equation with x4 as the extended state variable is:

[0017]

[0018] Among them: x1, x2, x3, x4 are the state variables of the state space equation, x1=i invα,β ,x2=u sα,β ,x3=i sα,β ,x4=Δu / L f ,and u sα,β 、i sα,β is the motor voltage and current; Δu is the voltage error caused by the nonlinear factor of the inverter; L f , C f , L s , R s They are the inductance of the LC filter, the capacitance of the LC filter, the motor inductance, and the motor resistance;

[0019] Create an extended variable observer as follows:

[0020]

[0021] in: Observe x1, x2, x3, and x4 respectively; For n Make observations; n =[u α,βref e sα,β ] T ; C = [1 0 0 0]; y n =x1=i invα,β ; L = [L1 L2 L3 L4] T , is the output error feedback matrix of the extended variable observer, L1, L2, L3, L4 are error feedback coefficients;

[0022]

[0023] The error feedback coefficients L1, L2, L3, L4 of the extended variable observer can be determined according to the pole placement theory:

[0024] All poles of the extended variable observer are placed at the origin, that is, |zI-A+LC|=(z-0) 4 , z is the intermediate variable. According to the equality of the corresponding coefficients, we can obtain L1, L2, L3, and L4;

[0025] The extended variable observer can observe the motor side voltage and current simultaneously, or can observe the motor side voltage or the motor side current separately;

[0026] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments: BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1This is a system structure diagram of the extended variable observation method for permanent magnet motor voltage and current described in the present invention.

[0028] Figure 2 This is a diagram of the internal structure of the motor voltage and current observation module described in the present invention. DETAILED DESCRIPTION

[0029] The present invention provides an extended variable observation method for voltage and current of a permanent magnet motor, and the method is further described in detail in conjunction with the accompanying drawings.

[0030] To implement the above method, the present invention adopts Figure 1 and 2 The control system shown in the figure is implemented, which includes an inverter, an LC filter, a permanent magnet synchronous motor, an abc-αβ module for three-phase static-two-phase static coordinate transformation, a back electromotive force calculation module, a motor voltage and current observation module, an αβ-dq module for two-phase static-two-phase rotating coordinate transformation, a current controller module, a dq-αβ module for two-phase rotating-two-phase static coordinate transformation, and a PWM module.

[0031] The system is divided into a power circuit and a control circuit. In the power circuit, the inverter outputs three-phase AC power, which is filtered by an LC filter and then fed to the permanent magnet synchronous motor. In the control circuit, the current output by the inverter is transformed by the abc-αβ module to obtain the inverter side current signal i of the α-axis and β-axis. invα,β The rotor position θ of the permanent magnet synchronous motor is given to the back electromotive force calculation module, which outputs the motor back electromotive force e of the α-axis and β-axis sα,β The inverter side current signal i of the α-axis and β-axis invα,β , α-axis and β-axis motor back electromotive force e sα,β The reference voltage u of the α-axis and β-axis output by the dq-αβ module α,βref As the input of the motor voltage and current observation module, the estimated motor side voltage of the α-axis and β-axis is output and motor side current The estimated α-axis and β-axis motor side currents output by the motor voltage and current observation module The estimated motor side currents of the d-axis and q-axis are obtained through coordinate transformation of the αβ-dq module The estimated d-axis and q-axis motor side currents The reference current i of the d-axis and q-axis d,qref The difference is calculated and the result is given to the current controller module to output the motor reference voltage u of the d-axis and q-axis d,qref ; The motor reference voltage u of the d-axis and q-axis d,qref The reference voltage u of the α-axis and β-axis is obtained by coordinate transformation of the dq-αβ module α,βref ; The reference voltage u of the α-axis and β-axisα,βref It is given to the PWM module, which outputs 6 PWM channels to control the on and off of the 6 switching tubes in the inverter.

[0032] The rotor position signal θ of the permanent magnet synchronous motor is given to the back electromotive force calculation module, and after calculation, the motor back electromotive force e of the α-axis and β-axis is output sα,β ;

[0033] The current signal of the inverter i invx It is given to the abc-αβ module, and after calculation, the inverter side current signal i of the α-axis and β-axis is output invα,β ; Where x = a, b, c;

[0034] The inverter side current signal i of the α-axis and β-axis output by the abc-αβ module invα,β , the reference voltage u of the α-axis and β-axis output by the dq-αβ module α,βref , the motor back electromotive force e of the α-axis and β-axis output by the back electromotive force calculation module sα,β Provide the motor voltage and current observation module to reconstruct the motor side voltage and current;

[0035] The output of the motor voltage and current observation module is the estimated motor side voltage of the α-axis and β-axis and motor side current

[0036] The estimated α-axis and β-axis motor side currents output by the motor voltage and current observation module The motor rotor position θ is given to the αβ-dq module, and the estimated d-axis and q-axis motor side currents are output after calculation.

[0037] The current reference i of the d-axis and q-axis d,qref Subtract the estimated d-axis and q-axis motor side currents output by the αβ-dq module The calculation result is given to the current controller module, and the motor voltage reference u of the d-axis and q-axis is output after calculation d,qref ;

[0038] The motor voltage reference u of the d-axis and q-axis output by the current controller module d,qref The motor rotor position θ is given to the dq-αβ module, and the reference voltage u of the α-axis and β-axis is output after calculation. α,βref ;

[0039] The reference voltage u of the α-axis and β-axis output by the dq-αβ module α,βref It is given to the PWM module, and after calculation, 6 PWMs are output to control the on and off of the 6 switching tubes in the inverter.

[0040] The observation method in the motor voltage and current observation module is as follows:

[0041] In the two-phase stationary coordinate system, the state space equation with x4 as the extended state variable is:

[0042]

[0043] Among them: x1, x2, x3, x4 are the state variables of the state space equation, x1=i invα,β ,x2=u sα,β ,x3=i sα,β ,x4=Δu / L f ,and u sα,β 、i sα,β is the motor voltage and current; Δu is the voltage error caused by the nonlinear factor of the inverter; L f , C f , L s , R s They are the inductance of the LC filter, the capacitance of the LC filter, the motor inductance, and the motor resistance;

[0044] Create an extended variable observer as follows:

[0045]

[0046] in: Observe x1, x2, x3, and x4 respectively; For n Make observations; n =[u α,βref e sα,β ] T ; C = [1 0 0 0]; y n =x1=i invα,β ; L = [L1 L2 L3 L4] T , is the output error feedback matrix of the extended variable observer, L1, L2, L3, L4 are error feedback coefficients;

[0047]

[0048] The error feedback coefficients L1, L2, L3, L4 of the extended variable observer can be determined according to the pole placement theory:

[0049] All poles of the extended variable observer are placed at the origin, that is, |zI-A+LC|=(z-0) 4 , z is the intermediate variable. According to the equality of the corresponding coefficients, we can obtain L1, L2, L3, and L4;

[0050] The extended variable observer can observe the motor side voltage and current simultaneously, or can observe the motor side voltage or the motor side current separately;

[0051] The state variables in the extended variable observer That is, the reconstructed motor side voltage of the α-axis and β-axis and motor side current

Claims

1. An extended variable observation method for voltage and current of a permanent magnet motor, characterized in that: The control system of the method comprises: an inverter (1), an LC filter (2), a permanent magnet synchronous motor (3), an abc-αβ module (4) for three-phase static-two-phase static coordinate transformation, a back electromotive force calculation module (5), a motor voltage and current observation module (6), an αβ-dq module (7) for two-phase static-two-phase rotating coordinate transformation, a current controller module (8), a dq-αβ module (9) for two-phase rotating-two-phase static coordinate transformation, and a PWM module (10); In the power circuit of the system, the inverter (1) outputs three-phase alternating current, which is filtered by the LC filter (2) and then supplied to the permanent magnet synchronous motor (3); In the control loop of the system, the current output by the inverter (1) is transformed by the coordinates of the abc-αβ module (4) to obtain the inverter side current signals i of the α-axis and the β-axis. invα,β The rotor position θ of the permanent magnet synchronous motor (3) is given to the back electromotive force calculation module (5), which outputs the motor back electromotive force e of the α-axis and β-axis sα,β The inverter side current signal i of the α-axis and β-axis invα,β , α-axis and β-axis motor back electromotive force e sα,β The reference voltage u of the α-axis and β-axis output by the dq-αβ module (9) α,βref As the input of the motor voltage and current observation module (6), the estimated motor side voltage of the α-axis and β-axis is output and motor side current The estimated motor side currents of the α-axis and β-axis output by the motor voltage and current observation module (6) The estimated motor side currents of the d-axis and q-axis are obtained through coordinate transformation of the αβ-dq module (7). The estimated d-axis and q-axis motor side currents The reference current i of the d-axis and q-axis d,qref The difference is calculated and the result is given to the current controller module (8), which outputs the motor reference voltage u of the d-axis and q-axis d,qref ; The motor reference voltage u of the d-axis and q-axis d,qref The reference voltage u of the α-axis and the β-axis is obtained by coordinate transformation of the dq-αβ module (9). α,βref ; The reference voltage u of the α-axis and β-axis α,βref The PWM module (9) outputs 6 PWMs to control the on and off of 6 switch tubes in the inverter (1); The rotor position signal θ of the permanent magnet synchronous motor (3) is given to the back electromotive force calculation module (5), and after calculation, the motor back electromotive force e of the α-axis and the β-axis is output. sα,β ; The current signal i of the inverter (1) invx It is given to the abc-αβ module (4), and after calculation, the inverter side current signal i of the α-axis and the β-axis is output invα,β ; Where x = a, b, c; The inverter side current signals i of the α-axis and β-axis output by the abc-αβ module (4) invα,β , the reference voltage u of the α-axis and β-axis output by the dq-αβ module (9) α,βref , the motor back electromotive force e of the α-axis and β-axis output by the back electromotive force calculation module (5) sα,β The data are sent to the motor voltage and current observation module (6) to reconstruct the voltage and current on the motor side; The output of the motor voltage and current observation module (6) is the estimated motor side voltage of the α-axis and β-axis and motor side current The estimated motor side currents of the α-axis and β-axis output by the motor voltage and current observation module (6) The motor rotor position θ is given to the αβ-dq module (7), and the estimated d-axis and q-axis motor side currents are output after calculation. The current reference i of the d-axis and q-axis d,qref Subtract the estimated d-axis and q-axis motor side currents output by the αβ-dq module (7) The calculation result is given to the current controller module (8), and after calculation, the motor voltage reference u of the d-axis and q-axis is output d,qref ; The motor voltage reference u of the d-axis and q-axis output by the current controller module (8) d,qref The motor rotor position θ is given to the dq-αβ module (9), and the reference voltage u of the α-axis and β-axis is output after calculation. α,βref ; The reference voltage u of the α-axis and β-axis output by the dq-αβ module (9) α,βref The PWM module (9) outputs 6 PWMs after calculation to control the on and off of 6 switch tubes in the inverter (1); The observation method in the motor voltage and current observation module (6) is as follows: In the two-phase stationary coordinate system, the state space equation with x4 as the extended state variable is: Among them: x1, x2, x3, x4 are the state variables of the state space equation, x1=i invα,β ,x2=u sα,β ,x3=i sα,β ,x4=Δu / L f ,and u sα,β 、i sα,β is the motor voltage and current; Δu is the voltage error caused by the nonlinear factor of the inverter; L f , C f , L s , R s They are the inductance of the LC filter, the capacitance of the LC filter, the motor inductance, and the motor resistance; Create an extended variable observer as follows: in: Observe x1, x2, x3, and x4 respectively; For n Make observations; n =[u α,βref e sα,β ] T ; C = [1 0 0 0]; y n =x1=i invα,β ; L = [L1 L2 L3 L4] T , is the output error feedback matrix of the extended variable observer, L1, L2, L3, L4 are error feedback coefficients; 2. The extended variable observation method of voltage and current of a permanent magnet motor according to claim 1, characterized in that: The error feedback coefficients L1, L2, L3, L4 of the extended variable observer are determined according to the pole placement theory: All poles of the extended variable observer are placed at the origin, that is, |zI-A+LC|=(z-0) 4 , z is the intermediate variable; based on the equality of corresponding coefficients, L1, L2, L3, and L4 are obtained.

3. The extended variable observation method of voltage and current of a permanent magnet motor according to claim 1, characterized in that: The extended variable observer can observe the motor side voltage and current simultaneously, or can observe the motor side voltage or the motor side current separately.

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