A motor current reconstruction method based on inverter-side current sampling using an extended state observer

Abstract

A motor current reconstruction method based on inverter-side current sampling using an extended state observer belongs to the field of motor control. For permanent magnet synchronous motor systems with LC filters, it is difficult to directly sample the current input to the motor due to problems such as the current sensor usually being integrated and installed inside the controller and the difficulty in installing the current sensor inside the LC filter. In response to this, the present invention proposes a method for sampling the inverter-side current and reconstructing and feeding back the motor-side current through an extended state observer, which is equivalent to directly sampling the motor-side current. This reconstruction method takes into account both the ease of operation of inverter-side current sampling and the system performance of motor-side current sampling, and does not increase the hardware cost of the control system.

Description

Technical Field

[0001] The invention relates to a motor current reconstruction method based on inverter-side current sampling of an extended state observer, and belongs to the field of motor control. Background Art

[0002] Permanent Magnet Synchronous Machine (PMSM) has long been widely used in various fields due to its advantages such as high power density and high efficiency. PMSM is usually driven by a voltage source inverter, which generates large electromagnetic noise and current harmonics. Currently, the most commonly used and effective method for suppressing current harmonics is to connect an LC low-pass filter in series between the inverter and the PMSM to filter out high-frequency current harmonics. However, the current sensor of the PMSM system is usually integrated into the motor controller. After adding the LC filter, it is difficult to directly sample the current signal of the input motor. The current on the inverter side contains a large amount of harmonics and has a certain phase difference with the current on the motor side after adding the LC filter. Therefore, directly sampling the current on the inverter side will significantly reduce the performance of the PMSM system and may even cause system instability.

[0003] The issue of current sampling locations in PMSM systems has been the subject of numerous studies, both domestically and internationally. Among these, the method of reconstructing the motor-side current using the inverter-side current via an observer has achieved significant success in controlling PMSM systems with LC filters due to its simplicity, reliability, and lack of additional controller hardware cost. In "Sensorless Control for PMSM Connected with LC Filter Based on Extended State Observer" (21st International Conference on Electrical Machines and Systems, 2018), an extended state observer was established for a PMSM system with an LC filter, achieving sensorless control. In "Current Control of Grid-Connected Inverter With LCL Filter Based on Extended-State Observer Estimations Using Single Sensor and Achieving Improved Robust Observation Dynamics" (IEEE Transactions on Industrial Electronics, 2017), an extended state observer was established for a grid system with an LCL filter, reconstructing the grid-side current using the inverter-side current. Summary of the Invention

[0004] Aiming at the problem that it is difficult to directly sample the motor side current in a PMSM system with an LC filter under traditional PI double closed-loop control, the present invention proposes a motor current reconstruction method based on inverter side current sampling using an extended state observer.

[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 eleven parts: three-phase inverter, LC filter, permanent magnet synchronous motor, signal sampling module, motor current reconstruction module, three-phase static-two-phase rotating coordinate transformation module, speed calculation module, speed loop PI controller module, current loop PI controller module, two-phase rotating-two-phase static coordinate transformation module, and SVPWM module.

[0006] The inverter side current signal i of the three-phase inverter invx (x=a, b, c) and the permanent magnet synchronous motor rotor position θ are given to the signal sampling module, and the A-phase inverter side current sampling signal i is output through sampling. inva, B-phase inverter side current sampling signal i invb , C-phase inverter side current sampling signal i invc and the rotor position θ;

[0007] The current sampling signal i of the three-phase inverter A phase inverter side output by the signal sampling module inva , B-phase inverter side current sampling signal i invb , C-phase inverter side current sampling signal i invc The current is reconstructed by the motor current reconstruction module, which includes the following reconstruction steps:

[0008] Step 1: Ignoring the parasitic resistance of the LC filter itself, the state space description of the LCL system consisting of the LC filter, motor stator inductance, and resistance in the three-phase coordinate system is shown in Equation (1):

[0009]

[0010] where i invx ,u invx is the inverter side phase current and inverter side voltage; i sx ,u sx , R sx , L sx They are respectively the motor side phase current, motor side voltage, motor stator resistance and inductance; C f ,u C is the filter capacitance and capacitor voltage; L f is the filter inductor.

[0011] Step 2: Rewrite Equation (1) into the state space equation shown in Equation (2):

[0012]

[0013] Among them, x1, x2, x3 are the state variables of the state space equation, x1=i invx , x2=u c , x3=i sx ; Respectively represent the derivatives of x1, x2, and x3; k1, k2, k3, and k4 are system parameters, and k1 = R sx / L sx , k2=1 / L sx , k3=1 / C f , k4=1 / L f .

[0014] Step 3: Define the state space equation as Equation (3) based on Equation (2) and transform it into the third-order integral series form as Equation (4):

[0015]

[0016]

[0017] in, is the integral series state variable; Respectively express Perform derivation; Indicates u invx Derivative; is the internal disturbance of the system and satisfies formula (5):

[0018]

[0019] Among them, l1, l2, l3 are the disturbance coefficients composed of system parameters, Indicates u invx Find the second derivative.

[0020] Step 4: Using the formula (4) As an extended state variable, the overall disturbance of the system d all It can be expressed as formula (6):

[0021]

[0022] Therefore, a fourth-order extended state observer can be established, as shown in formula (7):

[0023]

[0024] Where e is the observation error; z1, z2, z3, z4 are the observed variables, respectively. and the overall disturbance of the system d all Make observations, They represent the derivatives of z1, z2, z3, and z4 respectively; b1, b2, b3, and b4 are feedback coefficients, and their values are shown in formula (8) with reference to the Fibonacci sequence method.

[0025]

[0026] Where t is the sampling time T of the control system s .

[0027] Step 5: Solve equation (3) to get equation (9):

[0028]

[0029] Referring to the observation results of the extended state observer, we can get formula (10):

[0030]

[0031] in, Reconstruct current for the inverter side; To reconstruct the capacitor voltage; Reconstruct the current for the motor side.

[0032] The motor current reconstruction module finally outputs the reconstructed current of the permanent magnet synchronous motor phase A motor side B-phase motor side reconstruction current C-phase motor side reconstruction current

[0033] The reconstructed current of the permanent magnet synchronous motor phase A motor side output by the motor current reconstruction module B-phase motor side reconstruction current C-phase motor side reconstruction current The permanent magnet synchronous motor rotor position θ output by the signal sampling module is given to the three-phase static-two-phase rotating coordinate transformation module, and the permanent magnet synchronous motor d-axis motor side reconstruction current is output after calculation q-axis motor side reconstruction current

[0034] The permanent magnet synchronous motor rotor position θ output by the signal sampling module is given to the speed calculation module, and the actual speed ω of the permanent magnet synchronous motor is output after calculation. e ;

[0035] Reference speed ω ref Subtract the actual speed of the permanent magnet synchronous motor output by the speed calculation module ω e , and give its calculation result to the speed loop PI controller module, and output the permanent magnet synchronous motor q axis reference current i after calculation qref ;

[0036] The permanent magnet synchronous motor q-axis reference current i output by the speed loop PI controller module qref Subtract the q-axis motor side reconstruction current output by the three-phase static-two-phase rotating coordinate transformation module Permanent magnet synchronous motor d-axis reference current i dref Subtract the reconstructed current of the permanent magnet synchronous motor D-axis motor side output by the three-phase static-two-phase rotating coordinate transformation module They are respectively given to the current loop PI controller module, and after calculation, the permanent magnet synchronous motor d-axis reference voltage u is output dref , q-axis reference voltage u qref ;

[0037] The permanent magnet synchronous motor d-axis reference voltage u output by the current loop PI controller module dref , q-axis reference voltage u qref The permanent magnet synchronous motor rotor position θ output by the signal sampling module is given to the two-phase rotation-two-phase stationary coordinate transformation module, and the permanent magnet synchronous motor α-axis reference voltage u is output after calculation. αref, β-axis reference voltage u βref ;

[0038] The reference voltage u of the permanent magnet synchronous motor α axis output by the two-phase rotating-two-phase stationary coordinate transformation module αref , β-axis reference voltage u βref The output signal of the SVPWM module is 6-channel PWM, which is used as the input of the inverter to control the on and off of the 6 switching tubes in the inverter. The output signal of the SVPWM module is 6-channel PWM, which is used as the input of the inverter to control the on and off of the 6 switching tubes in the inverter.

[0039] The motor current reconstruction module includes: a fourth-order extended state observer module and a motor side current reconstruction function module. First, the three-phase inverter inverter side current i output by the signal sampling module is converted to invx The state variables Z1, Z2, Z3 and Z4 are obtained after observation. The state variables Z1 and Z3 are given to the motor side current reconstruction function module (5-2). After calculation, the motor side reconstruction current of the permanent magnet synchronous motor (3) is output.

[0040] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a system structure diagram of the motor current reconstruction method based on inverter-side current sampling using an extended state observer according to the present invention.

[0042] Figure 2 This is a diagram of the internal structure of the motor current reconstruction module described in the present invention. DETAILED DESCRIPTION

[0043] The present invention provides a motor current reconstruction method based on inverter-side current sampling using an extended state observer, which is further described in detail with reference to the accompanying drawings.

[0044] To implement the above method, the present invention adopts Figure 1 and 2 The control system shown in the figure is implemented, which includes eleven parts: three-phase inverter, LC filter, permanent magnet synchronous motor, signal sampling module, motor current reconstruction module, three-phase static-two-phase rotating coordinate transformation module, speed calculation module, speed loop PI controller module, current loop PI controller module, two-phase rotating-two-phase static coordinate transformation module, and SVPWM module.

[0045] The inverter side current signal i of the three-phase inverter invnThe permanent magnet synchronous motor rotor position θ is given to the signal sampling module, and the A-phase inverter side current sampling signal i is output through sampling. inva , B-phase inverter side current sampling signal i invb , C-phase inverter side current sampling signal i invc and the rotor position θ;

[0046] The current sampling signal i of the three-phase inverter A phase inverter side output by the signal sampling module inva , B-phase inverter side current sampling signal i invb , C-phase inverter side current sampling signal i invc The current is sent to the motor current reconstruction module, which calculates and outputs the reconstructed current of the permanent magnet synchronous motor phase A motor side. B-phase motor side reconstruction current C-phase motor side reconstruction current

[0047] The reconstructed current of the permanent magnet synchronous motor phase A motor side output by the motor current reconstruction module B-phase motor side reconstruction current C-phase motor side reconstruction current The permanent magnet synchronous motor rotor position θ output by the signal sampling module is given to the three-phase static-two-phase rotating coordinate transformation module, and the permanent magnet synchronous motor d-axis motor side reconstruction current is output after calculation q-axis motor side reconstruction current

[0048] The permanent magnet synchronous motor rotor position θ output by the signal sampling module is given to the speed calculation module, and the actual speed ω of the permanent magnet synchronous motor is output after calculation. e ;

[0049] Reference speed ω ref Subtract the actual speed of the permanent magnet synchronous motor output by the speed calculation module ω e , and give its calculation result to the speed loop PI controller module, and output the permanent magnet synchronous motor q axis reference current i after calculation qref ;

[0050] The permanent magnet synchronous motor q-axis reference current i output by the speed loop PI controller module qref Subtract the q-axis motor side reconstruction current output by the three-phase static-two-phase rotating coordinate transformation module Permanent magnet synchronous motor d-axis reference current i dref Subtract the reconstructed current of the permanent magnet synchronous motor D-axis motor side output by the three-phase static-two-phase rotating coordinate transformation module They are respectively given to the current loop PI controller module, and after calculation, the permanent magnet synchronous motor d-axis reference voltage u is output dref , q-axis reference voltage u qref ;

[0051] The permanent magnet synchronous motor d-axis reference voltage u output by the current loop PI controller module dref , q-axis reference voltage u qref The permanent magnet synchronous motor rotor position θ output by the signal sampling module is given to the two-phase rotation-two-phase stationary coordinate transformation module, and the permanent magnet synchronous motor α-axis reference voltage u is output after calculation. αref , β-axis reference voltage u βref ;

[0052] The reference voltage u of the permanent magnet synchronous motor α axis output by the two-phase rotating-two-phase stationary coordinate transformation module αref , β-axis reference voltage u βref The output signal of the SVPWM module is 6-channel PWM, which is used as the input of the inverter to control the on and off of the 6 switching tubes in the inverter. The output signal of the SVPWM module is 6-channel PWM, which is used as the input of the inverter to control the on and off of the 6 switching tubes in the inverter.

[0053] The specific contents of the motor current reconstruction algorithm are as follows:

[0054] Without considering the parasitic resistance of the LC filter itself, the state space description of the LCL system consisting of the LC filter, motor stator inductance and resistance in the three-phase coordinate system is shown in formula (1):

[0055] where i invx ,u invx (x=a, b, c) are the inverter side phase current and inverter side voltage; i sx ,u sx , R sx , L sx They are respectively the motor side phase current, motor side voltage, motor stator resistance and inductance; C f ,u C is the filter capacitance and capacitor voltage; L f is the filter inductor.

[0056]

[0057] The motor-side phase current reconstruction method mainly consists of two parts: an extended state observer (ESO) and a motor-side current reconstruction function. Taking the A, B, C, and C three-phase inverter-side currents as input, the ESO first observes the relevant state variables. Then, the system state variables are reorganized using transformation equations to obtain the reconstructed three-phase motor-side currents.

[0058] It can be seen from formula (1) that the mathematical model order of the LCL system composed of the LC filter and the motor stator inductance L is third-order. For the permanent magnet synchronous motor, the mathematical model of each phase in the three-phase coordinate system is exactly the same. Therefore, it is considered to establish ESO in the three-phase coordinate system to reconstruct the motor side current.

[0059] From formula (1), we can see that the state space equation of the third-order LCL system can be expressed as follows:

[0060]

[0061] Among them, x1, x2, x3 are the state variables of the state space equation, x1=i invx , x2=u c , x3=i sx ; Respectively represent the derivatives of x1, x2, and x3; k1, k2, k3, and k4 are system parameters, and k1 = R sx / L sx , k2=1 / L sx , k3=1 / C f , k4=1 / L f .

[0062] Define the state space equation as shown in formula (3):

[0063]

[0064] Then formula (3) can be transformed into a third-order integral series form:

[0065]

[0066] in, is the integral series state variable; Respectively express Perform derivation; Indicates u invx Derivative; is the internal disturbance of the system and satisfies the conditions in formula (5):

[0067]

[0068] Among them, l1, l2, l3 are the disturbance coefficients composed of system parameters, Indicates u invx Find the second derivative.

[0069] In formula (4) As an extended state variable, the overall disturbance of the system d all It can be expressed as formula (6):

[0070]

[0071] Therefore, the fourth-order ESO can be established as shown in formula (7):

[0072]

[0073] Where e is the observation error; z1, z2, z3, z4 are the observed variables, respectively. and the overall disturbance of the system d all Make observations, They represent the derivatives of z1, z2, z3, and z4 respectively; b1, b2, b3, and b4 are feedback coefficients, and their values are shown in formula (8) with reference to the Fibonacci sequence method.

[0074]

[0075] Where t is the sampling time T of the control system s .

[0076] Solving equation (3) yields equation (9):

[0077]

[0078] Referring to the observation results of ESO, we can get formula (10):

[0079]

[0080] At this point, the inverter side reconstruction current is obtained Reconstructing capacitor voltage Motor side reconstruction current

Claims

1. A motor current reconstruction method based on inverter-side current sampling using an extended state observer, characterized by: The control system of the method comprises: a three-phase inverter (1), an LC filter (2), a permanent magnet synchronous motor (3), a signal sampling module (4), a motor current reconstruction module (5), a three-phase static-two-phase rotating coordinate transformation module (6), a speed calculation module (7), a speed loop PI controller module (8), a current loop PI controller module (9), a two-phase rotating-two-phase static coordinate transformation module (10), and an SVPWM module (11); The inverter side current signal i of the three-phase inverter (1) invx The rotor position θ of the permanent magnet synchronous motor (3) is given to the signal sampling module (4), and the current sampling signal i of the A-phase inverter side is output through sampling. inva , B-phase inverter side current sampling signal i invb , C-phase inverter side current sampling signal i invc and the rotor position θ; where x = a, b, c; The current sampling signal i of the inverter side of the three-phase inverter (1) phase A output by the signal sampling module (4) inva , B-phase inverter side current sampling signal i invb , C-phase inverter side current sampling signal i invc The current is given to the motor current reconstruction module (5) for current reconstruction, which includes the following reconstruction steps: Step 1: Ignoring the parasitic resistance of the LC filter itself, the state space description of the LCL system consisting of the LC filter, motor stator inductance, and resistance in the three-phase coordinate system is shown in Equation (1): where i invx ,u invx is the inverter side phase current and inverter side voltage; i sx ,u sx , R sx , L sx They are respectively the motor side phase current, motor side voltage, motor stator resistance and inductance; C f ,u c is the filter capacitance and capacitor voltage; L f is the filter inductance; Step 2: Rewrite Equation (1) into the state space equation shown in Equation (2): Among them, x1, x2, x3 are the state variables of the state space equation, x1=i invx , x2=u c , x3=i sx ; Respectively represent the derivatives of x1, x2, and x3; k1, k2, k3, and k4 are system parameters, and k1 = R sx / L sx , k2=1 / L sx , k3=1 / C f , k4=1 / L f ; Step 3: Define the state space equation as shown in Equation (3) based on Equation (2) and transform it into the third-order integral series form as shown in Equation (4): in, is the integral series state variable; Respectively express Perform derivatives; Indicates u invx Derivative; represents the internal disturbance of the system and satisfies formula (5): Among them, l1, l2, l3 are the disturbance coefficients composed of system parameters, Indicates u invx Find the second derivative; Step 4: Using the formula (4) As an extended state variable, the overall disturbance of the system d all It is expressed as formula (6): Establish a fourth-order extended state observer, as shown in formula (7): Where e is the observation error; z1, z2, z3, z4 are the observed variables, respectively. and the overall disturbance of the system d all Make observations, Respectively represent the derivatives of z1, z2, z3, and z4; b1, b2, b3, and b4 are feedback coefficients, and their values are shown in formula (8) with reference to the Fibonacci sequence method; Where t is the sampling time T of the control system s ; Step 5: Solve equation (3) to get equation (9): Referring to the observation results of the extended state observer, we can get formula (10): in, Reconstruct current for the inverter side; To reconstruct the capacitor voltage; Reconstruct the current for the motor side, x = a, b or c; The motor current reconstruction module (5) finally outputs the reconstructed current of the permanent magnet synchronous motor (3) phase A motor side B-phase motor side reconstruction current C-phase motor side reconstruction current The reconstructed current of the permanent magnet synchronous motor (3) phase A motor side output by the motor current reconstruction module (5) B-phase motor side reconstruction current C-phase motor side reconstruction current The rotor position θ of the permanent magnet synchronous motor (3) output by the signal sampling module (4) is given to the three-phase static-two-phase rotating coordinate transformation module (6), and the reconstructed current of the d-axis motor side of the permanent magnet synchronous motor (3) is output after calculation. q-axis motor side reconstruction current The rotor position θ of the permanent magnet synchronous motor (3) output by the signal sampling module (4) is given to the speed calculation module (7), and the actual speed ω of the permanent magnet synchronous motor (3) is output after calculation. e ; Reference speed ω ref Subtract the actual speed ω of the permanent magnet synchronous motor (3) output by the speed calculation module (7) e , and gives its calculation result to the speed loop PI controller module (8), and outputs the q-axis reference current i of the permanent magnet synchronous motor (3) after calculation. qref ; The q-axis reference current i of the permanent magnet synchronous motor (3) output by the speed loop PI controller module (8) qref Subtract the q-axis motor side reconstruction current output by the three-phase stationary-two-phase rotating coordinate transformation module (6) Permanent magnet synchronous motor (3) d-axis reference current i dref Subtract the reconstructed current of the permanent magnet synchronous motor (3) d-axis motor side output by the three-phase stationary-two-phase rotating coordinate transformation module (6) They are respectively given to the current loop PI controller module (9), and after calculation, the d-axis reference voltage u of the permanent magnet synchronous motor (3) is output dref , q-axis reference voltage u qref ; The d-axis reference voltage u of the permanent magnet synchronous motor (3) output by the current loop PI controller module (9) dref , q-axis reference voltage u qref The rotor position θ of the permanent magnet synchronous motor (3) output by the signal sampling module (4) is given to the two-phase rotation-two-phase stationary coordinate transformation module (10), and the α-axis reference voltage u of the permanent magnet synchronous motor (3) is output after calculation. αref , β-axis reference voltage u βref ; The α-axis reference voltage u of the permanent magnet synchronous motor (3) output by the two-phase rotating-two-phase stationary coordinate conversion module (10) αref , β-axis reference voltage u βref The SVPWM module (11) outputs 6 PWMs after calculation, wherein the PWMs are used as inputs of the three-phase inverter (1) to control the on / off of the 6 switching tubes in the three-phase inverter (1); the output signals of the SVPWM module (11) are 6 PWMs, and the 6 PWMs are used as inputs of the three-phase inverter (1) to control the on / off of the 6 switching tubes in the three-phase inverter (1).

2. The motor current reconstruction method based on inverter-side current sampling using an extended state observer according to claim 1, characterized in that: The motor current reconstruction module (5) comprises: a fourth-order extended state observer module (5-1), a motor side current reconstruction function module (5-2), and first converts the inverter side current i of the three-phase inverter (1) output by the signal sampling module (4) into invx The fourth-order extended state observer module (5-1) is given, and after observation, the observer state variables z1, z2, z3, and z4 are obtained. The observer state variables z1 and z3 are given to the motor side current reconstruction function module (5-2), and the motor side reconstructed current of the permanent magnet synchronous motor (3) is output after calculation.

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