An Inverter Drive Control Method, System and Inverter for a Synchronous Motor

Abstract

The present application discloses an inverter drive control method, system and inverter for a synchronous motor. The synchronous motor is driven by a current source inverter. The method includes: constructing a mathematical model of the synchronous motor in dq coordinate system to obtain the actual currents and voltages of the synchronous motor on the d axis and the q axis; defining state variables, where the state variables include a first state variable, a second state variable, a third state variable and a fourth state variable; constructing a Lyapunov function according to the first to fourth state variables; making the Lyapunov function globally asymptotically stable at the equilibrium point to obtain the voltage reference values of the synchronous motor on the d axis and the q axis; calculating the ideal given value of the output current on the AC side of the current source inverter based on the voltage reference values, and converting to obtain the drive signals of the inverter bridge switching tubes in the inverter. The present application can improve the response speed and operation stability of the drive control system and reduce the complexity of the control system.

Description

Technical Field

[0001] The present application relates to the field of motors, and in particular, to an inverter drive control method, system, and inverter for a synchronous motor. Background Art

[0002] In a synchronous motor drive system, the inverter undertakes key energy conversion. In a motor control system, high-precision control of the motor is achieved by controlling the inverter. Inverters are divided into two types in principle, one is a voltage source inverter, and the other is a current source inverter. The current source inverter has an inductor connected in series in the DC circuit, which fits the characteristics of a high-speed motor with small inductance and large current ripple. Compared with the voltage source inverter, the current source inverter can better suppress current ripple and does not require a complex wave generation method, which is in line with the driving requirements of high-speed motors.

[0003] Currently, most of the control strategies for current source synchronous motor systems used in synchronous motor drive systems adopt the traditional PI (Proportional-Integral) method. This method requires tuning of many parameters, resulting in poor robustness of the control system. And considering the existence of the bus inductor and filter capacitor of the current source inverter, it further leads to a slow response speed of the control system. Summary of the Invention

[0004] To solve the deficiencies of the prior art, the present application adopts the following technical solutions:

[0005] In a first aspect, an inverter drive control method for a synchronous motor provided by the present application, the synchronous motor is driven by a current source inverter, and the drive control method includes:

[0006] Construct a mathematical model of the synchronous motor in the dq coordinate system to obtain the actual currents of the synchronous motor on the d axis and the q axis, and the actual voltages on the d axis and the q axis;

[0007] Define state variables, the state variables include a first state variable representing the difference between the actual current of the synchronous motor on the d axis and the current reference value on the d axis, a second state variable representing the difference between the actual current of the synchronous motor on the q axis and the current reference value on the q axis, a third state variable representing the difference between the actual voltage of the synchronous motor on the d axis and the voltage reference value on the d axis, and a fourth state variable representing the difference between the actual voltage of the synchronous motor on the q axis and the voltage reference value on the qThe fourth state variable of the difference between the shaft voltage reference values;

[0008] Construct a Lyapunov function according to the first to fourth state variables;

[0009] Make the Lyapunov function satisfy global asymptotic stability at the equilibrium point to obtain the voltage reference values of the synchronous motor on the d axis and q axis;

[0010] Based on the voltage reference values of the synchronous motor on the d axis and q axis, calculate the ideal given value of the output current on the AC side of the current source inverter, and based on the ideal given value of the output current, convert to obtain the driving signals of the inverter bridge switching tubes.

[0011] In summary, an inverter drive control method for a synchronous motor provided in this application is based on the actual current and actual voltage of the synchronous motor in the dq coordinate system, defines state variables, constructs a Lyapunov function based on the state variables, and by satisfying the global asymptotic stability of the Lyapunov function at the equilibrium point, thereby derives the voltage reference values of the synchronous motor in the dq coordinate system, thereby derives the ideal given value of the output current of the inverter AC side, obtains the driving signals for controlling the inverter bridge switching tubes, thereby obtaining the optimal inverter output current, improving the response speed and operation stability of the drive control system, reducing the complexity of the control system, and improving the robustness of the control method.

[0012] Furthermore, the Lyapunov function is expressed by the following formula:

[0013] ;

[0014] In the formula, L d represents the d axis inductance of the synchronous motor, L q represents the q axis inductance of the synchronous motor, C represents the shunt capacitor of the synchronous motor, x 1 represents the first state variable, x 2 represents the second state variable, x 3 represents the third state variable, x 4 represents the fourth state variable, V(x) represents the Lyapunov function.

[0015] Furthermore, by making the Lyapunov function satisfy the following four conditions, it thus satisfies global asymptotic stability at the equilibrium point. The conditions include:

[0016] ;

[0017] ;

[0018] ;

[0019] ;

[0020] Among them, represents the derivative of the Lyapunov function, and when the following conditions are met, make meet , and the conditions include:

[0021] ;

[0022] Among them, K d represents the shaft voltage damping regulation parameter of the synchronous motor d ; K q represents the shaft voltage damping regulation parameter of the synchronous motor q ; represents the fluctuation value of the dq axis current output by the AC side of the inverter compared with the steady-state current in the d coordinate system, represents the fluctuation value of the dq axis current output by the AC side of the inverter compared with the steady-state current in the q coordinate system.

[0023] Furthermore, the ideal given value of the output current of the AC side of the current-source inverter is calculated by the following formula:

[0024] ;

[0025] ;

[0026] In the formula, , , represents the permanent magnet flux linkage, L d represents the d axis inductance of the synchronous motor, L q represents the q axis inductance of the synchronous motor, I d represents the dq axis current value output by the AC side of the inverter in the steady state in the d coordinate system, I qIndicates the output dq under the q coordinate system when in steady state, R represents the phase resistance of the synchronous motor, represents the electrical angular velocity obtained by converting the given speed of the motor, C represents the shunt capacitance of the synchronous motor, i * ds represents the d axis current reference value of the synchronous motor, i * qs represents the q axis current reference value of the synchronous motor, u * ds represents the d axis voltage reference value of the synchronous motor, u * qs represents the q axis voltage reference value of the synchronous motor, u ds represents the d axis actual voltage of the synchronous motor, u qs represents the q axis actual voltage of the synchronous motor, e ds represents the d axis back electromotive force of the synchronous motor, e qs represents the q axis back electromotive force of the synchronous motor.

[0027] Furthermore, the ideal given value of the output current on the AC side of the current source inverter is calculated by the following formula:

[0028] ;

[0029] ;

[0030] In the formula, , , is the permanent magnet flux linkage, L d represents the d axis inductance of the synchronous motor, L q represents the q axis inductance of the synchronous motor, I d Indicates the output on the AC side of the inverter at steady state under dqOutput under the coordinate system d Axis current value, I q Indicates the output of the inverter's AC side at steady state in dq Output under the coordinate system q Axis current value, R Indicates the phase resistance of the synchronous motor, Indicates the electrical angular velocity obtained by converting the given speed of the motor, C Indicates the shunt capacitance of the synchronous motor, i * ds Indicates the d Axis current reference value of the synchronous motor, i * qs Indicates the q Axis current reference value of the synchronous motor, u * ds Indicates the d Axis voltage reference value of the synchronous motor, u * qs Indicates the q Axis voltage reference value of the synchronous motor, u ds Indicates the d Axis actual voltage of the synchronous motor, u qs Indicates the q Axis actual voltage of the synchronous motor, K Id Indicates the synchronous motor's d Axis current damping adjustment parameter, K Iq Indicates the synchronous motor's q Axis current damping adjustment parameter, e ds Indicates the d Axis back electromotive force of the synchronous motor, e qs Indicates the q Axis back electromotive force.

[0031] Furthermore, the d Axis current reference value i * ds Is set to 0, and the q Axis current reference value i * qs Is obtained by a PI controller through a speed closed-loop.

[0032] Furthermore, the inverter drive control method further includes: constructing a state space equation of the system, and adjusting the voltage damping adjustment parameters of the d axis and q axis of the synchronous motor, or adjusting the voltage damping adjustment parameters and current damping adjustment parameters of the d axis and q axis of the synchronous motor, so that all poles of the state space equation are distributed in the left half plane.

[0033] Furthermore, the state space equation is expressed by the following formula:

[0034] ;

[0035] Wherein, , ;

[0036] ;

[0037] ;

[0038] In the formula, represents the derivative of the state variable, X represents the state variable matrix, U represents the input quantity matrix, and A and B represent the parameter matrices. R represents the phase resistance of the synchronous motor, represents the voltage damping adjustment parameter of the d axis of the synchronous motor, represents the voltage damping adjustment parameter of the q axis of the synchronous motor, represents the current damping adjustment parameter of the d axis of the synchronous motor, represents the current damping adjustment parameter of the q axis of the synchronous motor, represents the electrical angular velocity obtained by converting the given speed of the motor, C represents the shunt capacitor of the synchronous motor, i ds represents the d axis actual current of the synchronous motor, i qs represents the q axis actual current of the synchronous motor, u ds represents the d axis actual voltage of the synchronous motor, u qs represents the q axis actual voltage of the synchronous motor, L d represents the d axis inductance of the synchronous motor, Lq representing the q axis inductance of the synchronous motor.

[0039] In a second aspect, the present application further provides an inverter, which includes a current source inverter circuit and a controller. The inverter is used to drive a synchronous motor, and the controller is configured to adopt the above-mentioned inverter drive control method.

[0040] In a third aspect, the present application further provides a synchronous motor drive system, which includes: a synchronous motor, and a current source inverter for driving the synchronous motor. The current source inverter is configured to adopt the above-mentioned inverter drive control method. Description of the Drawings

[0041] Figure 1 is a flowchart of the steps of the inverter drive control method for a synchronous motor provided by an embodiment of the present application;

[0042] Figure 2 is an overall drive schematic diagram of a current source inverter provided by an embodiment of the present application;

[0043] Figure 3 is a schematic diagram of energy distribution of a current source inverter provided by an embodiment of the present application;

[0044] Figure 4 is a control block diagram of the inverter drive control method for a synchronous motor provided by an embodiment of the present application;

[0045] Figure 5 is a schematic diagram of comparing the speed waveforms of a synchronous motor under the inverter drive control method of the present application and the traditional PI control method;

[0046] Figure 6 is a schematic diagram of comparing the torque waveforms of a synchronous motor under the inverter drive control method of the present application and the traditional PI control method;

[0047] Figure 7 is a schematic diagram of the three-phase current waveforms of a synchronous motor based on the inverter drive control method provided by an embodiment of the present application;

[0048] Figure 8 is a schematic diagram of the three-phase current waveforms of a synchronous motor based on the traditional PI control method provided by an embodiment;

[0049] Figure 9 is a schematic diagram of the result of Fourier analysis of the inverter drive control method for a synchronous motor provided by an embodiment;

[0050] Figure 10Schematic diagram of the result of Fourier analysis of a traditional PI control method provided by an embodiment;

[0051] Figure 11 In the inverter drive control method of a synchronous motor provided by an embodiment of the present application, the synchronous motor d Axis voltage damping regulation parameter and q Schematic diagram of the root locus change of the motor control system during the change process of the axis voltage damping regulation parameter;

[0052] Figure 12 In the inverter drive control method of a synchronous motor provided by an embodiment of the present application, the synchronous motor d Axis voltage damping regulation parameter and q When the axis voltage damping regulation parameter is -0.4, the synchronous motor d Axis current damping regulation parameter and q Schematic diagram of the root locus change of the motor control system during the change process of the axis current damping regulation parameter;

[0053] Figure 13 In the inverter drive control method of a synchronous motor provided by an embodiment of the present application, the synchronous motor d Axis voltage damping regulation parameter and q When the axis voltage damping regulation parameter is -0.4 and d Axis current damping regulation parameter and q Schematic diagram of the root locus change of the control system under the change of rotational speed when the axis current damping regulation parameter is 5;

[0054] Figure 14 In the inverter drive control method of a synchronous motor provided by an embodiment of the present application, in the d Axis current damping regulation parameter and q When the axis current damping regulation parameter is 0 d Axis voltage damping regulation parameter and q Bode plot of the transfer function of the direct-axis current to the direct-axis current reference value under the change of the axis voltage damping regulation parameter;

[0055] Figure 15 In the inverter drive control method of a synchronous motor provided by an embodiment of the present application, in the d Axis current damping regulation parameter and q When the axis current damping regulation parameter is 0 d Axis voltage damping regulation parameter and q Bode plot of the transfer function of the quadrature-axis current to the quadrature-axis current reference value under the change of the axis voltage damping regulation parameter;

[0056] Figure 16 In the inverter drive control method of a synchronous motor provided by an embodiment of the present application, in thed Axis voltage damping regulation parameter and q When the axis voltage damping regulation parameter is -0.4 d Axis current damping regulation parameter and q Bode plot of the transfer function of the direct-axis current to the direct-axis current reference value under the change of the axis current damping regulation parameter;

[0057] Figure 17 In the inverter drive control method of a synchronous motor provided by an embodiment of the present application, in the synchronous motor d Axis voltage damping regulation parameter and q When the axis voltage damping regulation parameter is -0.4 d Axis current damping regulation parameter and q Bode plot of the transfer function of the quadrature-axis current to the quadrature-axis current reference value under the change of the axis current damping regulation parameter. Specific embodiments

[0058] The following will describe the present application in detail in conjunction with the specific embodiments shown in the drawings, but these embodiments do not limit the present application. Any structural, method, or functional transformation made by those of ordinary skill in the art based on these embodiments is included in the protection scope of the present application.

[0059] To solve the deficiencies of the prior art, in a first aspect, the present application provides an inverter drive control method for a synchronous motor. The synchronous motor is driven by a current source inverter, as Figure 1 shown, and the drive control method includes the following steps:

[0060] Step S11, construct a mathematical model of the synchronous motor in the dq coordinate system to obtain the actual currents of the synchronous motor on the d axis and the q axis, and the actual voltages on the d axis and the q axis.

[0061] Step S12, define state variables, which include a first state variable representing the difference between the actual current of the synchronous motor on the d axis and the d axis current reference value, a second state variable representing the difference between the actual current of the synchronous motor on the q axis and the q axis current reference value, a third state variable representing the difference between the actual voltage of the synchronous motor on the d axis and the d axis voltage reference value, and a fourth state variable representing the difference between the actual voltage of the synchronous motor on the q axis and the q axis voltage reference value.

[0062] Step S13: Construct a Lyapunov function based on the first to fourth state variables.

[0063] Step S14: Make the Lyapunov function globally asymptotically stable at the equilibrium point to obtain the voltage reference values of the synchronous motor on the d-axis and q-axis.

[0064] Step S15: Based on the voltage reference values of the synchronous motor on the d axis and q axis, calculate the ideal given value of the output current on the AC side of the current source inverter, and convert it to obtain the drive signals of the inverter bridge switching tubes in the inverter based on the ideal given value of the output current.

[0065] Specifically, the overall framework of the synchronous motor drive system is as Figure 2 shown, Figure 2 where i dc represents the current from the bus inductance. According to the current vector of the current source inverter shown in Table 1 (each current vector corresponds to two switching tubes of the inverter three-phase bridge conducting, and the other four are turned off), continuously switch the inverter switch state to switch the bus current to phases A, B, and C according to the needs of the synchronous motor.

[0066]

[0067] Table 1

[0068] In step S11, based on the inverter switch switching process, according to Kirchhoff's voltage and current laws, considering the three-phase filter capacitors connected in parallel on the motor side, and combining the mathematical model of the synchronous motor in the three-phase coordinate system, the mathematical model of the output side of the inverter of the current source inverter synchronous motor drive system in the three-phase coordinate system is obtained as:

[0069] (1);

[0070] (2);

[0071] In the formula, represents the phase inductance of the synchronous motor, respectively represent the three-phase phase currents of the synchronous motor, respectively represent the three-phase phase voltages of the synchronous motor, represents the phase resistance of the synchronous motor, respectively represent the three-phase back electromotive forces of the synchronous motor, represents the shunt capacitance of the synchronous motor, respectively represent the currents directly output by the three phases of the current source inverter.

[0072] By using equal - amount coordinate transformation, formulas (1) and (2) are transformed from the three - phase stationary coordinate system to dq the coordinate system, obtaining the mathematical model of the synchronous motor in dq the coordinate system, obtaining the actual currents of the synchronous motor on the d axis and q the axis, and, on the d axis and q the axis, the actual voltages. The mathematical model of the synchronous motor in dq the coordinate system can be expressed by the following formula:

[0073] (3);

[0074] In the formula, respectively represent the d and q axis currents directly output by the inverter, respectively represent the d and q axis currents of the motor, respectively represent the d and q axis voltages of the motor, L k ( k = d , q ) respectively represent the d and q axis inductances of the motor; represents the synchronous angular velocity of the motor. The synchronous angular velocity varies with the rotational speed of the motor, respectively represent the d and q axis back electromotive forces of the motor. The back electromotive forces vary with the synchronous angular velocity of the motor.

[0075] In step S12, after obtaining the actual currents of the synchronous motor on the d axis and q the axis, and the actual voltages on the d axis and q the axis for the current - source inverter synchronous - motor drive system, due to the free - wheeling effect of the filter capacitor in the zero - vector state, it is necessary to regulate the currents of the synchronous motor on the d and q axes and the voltages of the synchronous motor on the d and q axes. Furthermore, the following four state variables are defined: The first state variable representing the difference between the actual current of the synchronous motor on the d axis and the d - axis current reference value, the actual current of the synchronous motor on the q axis and qThe second state variable of the difference between the shaft current reference values, characterizing the synchronous motor d The actual shaft voltage and d The third state variable of the difference between the shaft voltage reference value, characterizing the synchronous motor q The actual shaft voltage and q The fourth state variable of the difference between the shaft voltage reference values. The state variables can be expressed by the following formula:

[0076] (4);

[0077] Wherein, x 1 represents the first state variable, x 2 represents the second state variable, x 3 represents the third state variable, x 4 represents the fourth state variable; respectively represent the actual values of the shaft currents of the synchronous motor d and q respectively, respectively represent the reference values of the shaft currents of the synchronous motor d and q respectively, respectively represent the actual values of the shaft voltages of the synchronous motor d and q respectively, respectively represent the reference values of the shaft currents of the synchronous motor d and q respectively.

[0078] Furthermore, when the entire current-source inverter synchronous motor drive system is in a steady state, the actual values of the voltage and current of the synchronous motor in the dq coordinate system are equal to the reference values. At this time, the following equation exists:

[0079] (5);

[0080] At this time, the reference values of the voltage and current are constants. Substituting the actual values of the voltage and current of the synchronous motor at this time into formula (3) to calculate the steady-state equation of the synchronous motor, the steady-state equation can be expressed as follows:

[0081] (6);

[0082] Wherein, I k ( k = d , q ) respectively represent the dq coordinate system output by the AC side of the inverter at steady state d and q shaft current values.

[0083] As Figure 3 shown, when the current source inverter is in the non - zero vector state shown in Table 1, the total energy from the bus inductance is first consumed by 6 switching tubes and 6 diodes , and then a part is delivered to the three - phase filter capacitor in parallel with the permanent magnet synchronous motor , a part is delivered to the synchronous motor inductance , and then a part is consumed by the synchronous motor resistance , and the remaining is transferred to the synchronous motor back - electromotive force. Further, when the current source inverter is in the zero - vector state shown in Table 1, one of the three - phase bridge arms of A, B, and C is directly connected, and the switching tubes of the other two bridge arms are all turned on. During the process of the bus inductance storing energy and the AC filter capacitor supplying energy to the motor alone, the three - phase filter capacitor supplies energy to the synchronous motor inductance, resistance, and back - electromotive force, and finally all the energy is consumed.

[0084] In step S13, based on the states of the first to fourth state variables, when the energy of the current - source synchronous - motor drive system is in a continuously dissipating state, the four state variables converge to the equilibrium point. At this time, all four state variables are equal to 0. A Lyapunov function is constructed, and the Lyapunov direct method is used to analyze the global stability of the current - source synchronous - motor drive system at the equilibrium point.

[0085] As an optional implementation, the Lyapunov function can be expressed as follows:

[0086] (7);

[0087] In the formula, L d represents the d axis inductance of the synchronous motor, L q represents the q axis inductance of the synchronous motor, C represents the parallel capacitance of the synchronous motor, x 1 represents the first state variable, x 2 represents the second state variable, x 3 represents the third state variable, x 4 represents the fourth state variable, V(x) represents the Lyapunov function.

[0088] Furthermore, the Lyapunov direct method obtains the control law to ensure the global stability of the drive system by making the derivative of the Lyapunov function always negative. As an optional implementation, in step S14, by making the Lyapunov function satisfy the following four conditions, the global asymptotic stability at the equilibrium point is satisfied. The conditions include:

[0089] (8);

[0090] Wherein, represents the derivative of the Lyapunov function, which can be expressed as follows:

[0091] (9);

[0092] In the formula, represents the derivative of the first state variable, represents the derivative of the second state variable, represents the derivative of the third state variable, represents the derivative of the fourth state variable.

[0093] Furthermore, analyze the actual output current value of the inverter's AC side in the dq coordinate system. When the following conditions are met:

[0094] (10);

[0095] In the formula, respectively represent the actual output current values of the inverter's AC side in the dq coordinate system, respectively represent the output current values of the inverter's AC side at steady state in the dq coordinate system, respectively represent the fluctuation values of the output current of the inverter's AC side in the dq coordinate system compared with the steady-state current.

[0096] Substitute formula (4) and formula (10) into formula (3), and simplify through the steady-state equation formula (6) to obtain the following expression:

[0097] (11);

[0098] In the formula, respectively represent the fluctuation values of the output current of the inverter's AC side in the dq coordinate system compared with the steady-state current. Substitute formula (11) into the derivative of the Lyapunov function to obtain the following expression:

[0099] (12);

[0100] When the following conditions are met, make meet , and the conditions include:

[0101] (13);

[0102] In the formula, K d represents the synchronous motor d shaft voltage damping regulation parameter, K q represents the synchronous motor q shaft voltage damping regulation parameter.

[0103] According to the steady-state equation formula (6), it can be derived that:

[0104] (14);

[0105] As an alternative implementation, as Figure 4 shown, in the motor control system, the d shaft current reference value of the synchronous motor is set to 0, and the q shaft current reference value of the synchronous motor is obtained by the PI controller through the speed closed-loop. Based on formula (6), by making the Lyapunov function satisfy global asymptotic stability at the equilibrium point, the voltage reference values of the synchronous motor on the d axis and q axis are obtained. The voltage reference values of the synchronous motor on the d axis and q axis can be expressed as follows:

[0106] (15);

[0107] In the formula, represents the voltage reference value of the synchronous motor on the d axis, represents the voltage reference value of the synchronous motor on the q axis.

[0108] According to the equation of the permanent magnet synchronous motor in the dq coordinate system:

[0109] (16);

[0110] In the formula, represents the permanent magnet flux linkage, represents the electrical angular velocity of the synchronous motor. The electrical angular velocity changes with the speed of the synchronous motor, and the electrical angular velocity is obtained by converting the given speed of the synchronous motor.

[0111] As an alternative implementation, in step S15, according to formula (13), formula (14), formula (15), and the four state variables, based on the synchronous motor on the d axis andq Based on the voltage reference value of the shaft, the ideal given value of the output current on the AC side of the current source inverter can be calculated. The calculation formula for the ideal given value of the output current can be expressed as follows:

[0112] (17);

[0113] In the formula, , , represents the permanent magnet flux linkage, L d represents the d axis inductance of the synchronous motor, L q represents the q axis inductance of the synchronous motor, I d represents the dq axis current value output by the inverter on the AC side in the d coordinate system at steady state, I q represents the dq axis current value output by the inverter on the AC side in the q coordinate system at steady state, R represents the phase resistance of the synchronous motor, represents the electrical angular velocity obtained by converting the given speed of the motor, C represents the shunt capacitor of the synchronous motor, i * ds represents the d axis current reference value of the synchronous motor, i * qs represents the q axis current reference value of the synchronous motor, u * ds represents the d axis voltage reference value of the synchronous motor, u * qs represents the q axis voltage reference value of the synchronous motor, u ds represents the d axis actual voltage of the synchronous motor, u qs represents the q axis actual voltage of the synchronous motor.

[0114] Further, in step S15, the ideal given value of the output current obtained based on the above formula (17) is converted to obtain the drive signals of the inverter bridge switching tubes in the inverter, including: performing an inverse Park transformation on the obtained ideal given value of the output current to obtain the current required on the AC side of the inverter in the two-phase coordinate system of the current source inverter synchronous motor drive system . Furthermore, for the current source inverter, the effective vectors and zero vectors shown in Table 1 are reasonably allocated, and the current source SVPWM algorithm is adopted. When the bus inductance current remains unchanged at the steady-state value, the on / off of the inverter bridge switching tubes is controlled to synthesize the current required on the AC side of the inverter in the three-phase coordinate system .

[0115] The inverter drive control method further includes: constructing the state space equation of the system, and based on the state space equation, adjusting the voltage damping adjustment parameters of the d axis and the q axis of the synchronous motor so that the poles of the state space equation are all distributed in the left half plane

[0116] As another alternative implementation, a second current feedback loop can be added to further improve the control effect. The ideal given value of the output current on the AC side of the current source inverter can be calculated by the following formula

[0117] (18);

[0118] In the formula, , , represents the permanent magnet flux linkage, L d represents the d axis inductance of the synchronous motor, L q represents the q axis inductance of the synchronous motor, I d represents the dq axis current value output by the AC side of the inverter at steady state in the d coordinate system, I q represents the dq axis current value output by the AC side of the inverter at steady state in the q coordinate system, R represents the phase resistance of the synchronous motor, represents the electrical angular velocity converted from the given speed of the motor, C represents the shunt capacitor of the synchronous motor, i * ds represents the d axis current reference value of the synchronous motori * qs Indicating the q axis current reference value of the synchronous motor, u * ds Indicating the d axis voltage reference value of the synchronous motor, u * qs Indicating the q axis voltage reference value of the synchronous motor, u ds Indicating the d actual axis voltage of the synchronous motor, u qs Indicating the q actual axis voltage of the synchronous motor, K Id Indicating the d axis current damping adjustment parameter of the synchronous motor, K Iq Indicating the q axis current damping adjustment parameter of the synchronous motor.

[0119] Further, in step S15, the driving signals of the inverter bridge switching tubes are obtained by converting the ideal given value of the output current obtained based on the above formula (18), including: performing an inverse Park transformation on the obtained ideal given value of the output current to obtain the current required on the AC side of the inverter in the two-phase coordinate system of the current source inverter synchronous motor drive system . Furthermore, for the current source inverter, the effective vectors and zero vectors shown in Table 1 are reasonably allocated, and the current source SVPWM algorithm is used to control the on and off of the inverter bridge switching tubes to synthesize the current required on the AC side of the inverter in the three-phase coordinate system while keeping the steady-state value of the bus inductance current unchanged .

[0120] As an optional implementation manner, the inverter drive control method further includes: constructing the state space equation of the system, and the state space equation can be expressed by the following formula:

[0121] (19);

[0122] Wherein, represents the derivative of the state variable, X represents the state variable matrix, and , U represents the input quantity matrix, and , A and B represent the parameter matrices.

[0123] Further, the parameter matrices A and B exist:

[0124] (20);

[0125] (21);

[0126] Wherein, R represents the phase resistance of the synchronous motor, represents the synchronous motor d shaft voltage damping regulation parameter, represents the synchronous motor q shaft voltage damping regulation parameter, represents the synchronous motor d shaft current damping regulation parameter, represents the synchronous motor q shaft current damping regulation parameter, represents the electrical angular velocity obtained by converting the given speed of the motor, C represents the shunt capacitance of the synchronous motor, i ds represents the d actual shaft current of the synchronous motor, i qs represents the q actual shaft current of the synchronous motor, u ds represents the d actual shaft voltage of the synchronous motor, u qs represents the q actual shaft voltage of the synchronous motor, L d represents the d shaft inductance of the synchronous motor, L q represents the q shaft inductance of the synchronous motor.

[0127] Further, based on the state space equation, adjust the voltage damping regulation parameters and current damping regulation parameters of the d-axis and q-axis of the synchronous motor so that the poles of the state space equation are all distributed in the left half plane. d d-axis and q q-axis voltage damping regulation parameters and current damping regulation parameters of the synchronous motor, so that the poles of the state space equation are all distributed in the left half plane.

[0128] Specifically, according to the state space equation, plot the pole distribution of the entire system, and then select the d-axis voltage damping regulation parameter d of the synchronous motor, the d-axis voltage damping regulation parameter q of the synchronous motor, the q-axis current damping regulation parameter d of the synchronous motor, and the q-axis current damping regulation parameter q of the synchronous motor. .

[0129] When the poles of a system are all in the left half-plane, the system remains stable. and When it is negative, the magnitudes of these two determine the distance between the system poles and the imaginary axis. The larger the absolute value of the negative real part of the closed-loop poles, that is, the farther the negative real part of the closed-loop poles is from the imaginary axis on the left side of the S-plane, the faster the corresponding response component decays, and the stronger the dynamic response ability of the system.

[0130] For further illustration and to verify a drive control method for a synchronous motor provided by this application, a simulation experiment was conducted. The simulation parameters are shown in Table 2:

[0131]

[0132] Table 2

[0133] By comparing the traditional PI control method and the control method provided by this application through simulation experiments, the speed waveform of the synchronous motor is as Figure 5 shown, Figure 5 where the blue line represents the reference line, the red line represents the control method provided by this application, and the yellow line represents the traditional PI control method. As can be seen from Figure 5 it, the speed of the synchronous motor reaches a steady state of 18,000 rpm from an initial 0 rpm at 0.3 s and suddenly adds a rated load torque of 0.85 N·m. During the entire operation of the motor, the control method provided by this application is overall better than the traditional PI control method in terms of tracking the given speed, and the overshoot is also smaller. The torque waveform of the synchronous motor is as Figure 6 shown. In the figure, the blue line represents the control method provided by this application, and the red line represents the traditional PI control method. From the start of speed increase of the synchronous motor until it reaches the steady-state speed and then suddenly adds a load, the control method provided by this application has a faster response speed and better stability. The current waveforms of the three-phase current of the synchronous motor are obtained, and Fourier analysis is performed on the traditional PI control method and the control method provided by this application. The three-phase current waveform of the synchronous motor based on the control method of this application is as Figure 7 shown, and the three-phase current waveform of the synchronous motor based on the traditional PI control method is as Figure 8 shown. The result of Fourier analysis on the control method provided by this application is as Figure 9 shown, and the result of Fourier analysis on the traditional PI control method is as Figure 10 shown. It can be obtained that the harmonics of the three-phase current of the synchronous motor of the control method provided by this application are smaller than those of the traditional PI control method.

[0134] Furthermore, based on the transfer function, the influence of parameter changes on the stability of the control system is analyzed. Specifically, adjust the d axis and q axis voltage damping adjustment parameters of the synchronous motor, the synchronous motord Axis voltage damping regulation parameter and q Axis voltage damping regulation parameter During the change process, the root locus change of the motor control system is as Figure 11 shown. It can be seen that when only d Axis voltage damping regulation parameter and q Axis voltage damping regulation parameter exist, as d Axis voltage damping regulation parameter and q Axis voltage damping regulation parameter become smaller, there are multiple conjugate complex roots of the control system approaching the imaginary axis, and the stability of the system gradually decreases, thus limiting the d Axis voltage damping regulation parameter and q Axis voltage damping regulation parameter change range.

[0135] Set d Axis voltage damping regulation parameter and q Axis voltage damping regulation parameter both to -0.4, and adjust the current damping regulation parameters of the d axis and q axis of the synchronous motor. During the change process of the d axis current damping regulation parameter and q axis current damping regulation parameter of the synchronous motor, the root locus change of the motor control system is as Figure 12 shown. It can be seen that by introducing the current damping regulation parameters of the d axis and q axis of the synchronous motor, the two conjugate complex roots originally close to the imaginary axis start to move away from the imaginary axis, and the stability of the control system is improved.

[0136] Furthermore, set d Axis voltage damping regulation parameter and q Axis voltage damping regulation parameter both to -0.4, and set d Axis current damping regulation parameter and q Axis current damping regulation parameter both to 5. The root locus change of the control system when the rotational speed changes is as Figure 13 shown. As the motor rotational speed increases, the real part of the root locus of the control system remains unchanged, and the control system remains stable during the process of the motor rotational speed increasing to the rated rotational speed.

[0137] The d shaft current damping adjustment parameters and q shaft current damping adjustment parameters are both set to 0. At this time, the direct-axis current i d for the direct-axis current reference value i d * The Bode plot of the transfer function is as Figure 14 shown. The quadrature-axis current i q for the quadrature-axis current reference value i q * The Bode plot of the transfer function is as Figure 15 shown. It can be seen that as the d shaft voltage damping adjustment parameters and q shaft voltage damping adjustment parameters decrease, there is a resonance peak in the current loop, and the d shaft voltage damping adjustment parameters and q shaft voltage damping adjustment parameters of the synchronous motor have limited adjustment ranges, resulting in limited adjustment capabilities of the control system.

[0138] On this basis, a current feedback loop is added, and the d shaft current damping adjustment parameters and q shaft current damping adjustment parameters of the synchronous motor are introduced. The d shaft voltage damping adjustment parameters and q shaft voltage damping adjustment parameters are both set to -0.4. At this time, the direct-axis current i d for the direct-axis current reference value i d * The Bode plot of the transfer function is as Figure 16 shown. The quadrature-axis current i q for the quadrature-axis current reference value i q * The Bode plot of the transfer function is as Figure 17 shown. It can be seen that as the d shaft current damping adjustment parameters and q shaft current damping adjustment parameters increases, the original resonance peak disappears, and the synchronous motor d shaft voltage damping regulation parameter and q shaft voltage damping regulation parameter has a widened adjustment range, thereby improving the adjustment ability of the control system and improving the damping performance of the control system.

[0139] According to the above description, an inverter drive control method for a synchronous motor provided by this application is based on the actual current and actual voltage of the synchronous motor in dq the coordinate system, defines state variables, constructs a Lyapunov function based on the state variables, and satisfies the global asymptotic stability of the Lyapunov function at the equilibrium point, thereby deriving the voltage reference value of the synchronous motor in dq the coordinate system, thereby deriving the ideal given value of the output current of the AC side of the inverter, obtaining the drive signal for controlling the switching tubes of the inverter bridge, thereby obtaining the optimal inverter output current, improving the response speed and operation stability of the motor drive control system, reducing the complexity of the control system, and improving the robustness of the control method. Further, an inverter drive control method for a synchronous motor provided by this application also improves the damping performance of the control system by introducing a current feedback loop, and the calculation of the current on the AC side of the inverter includes motor current feedback and motor voltage feedback.

[0140] In a second aspect, this application also provides an inverter, which includes a current source inverter circuit and a controller. The inverter is used to drive a synchronous motor, and the controller is configured to adopt the inverter drive control method described above to improve the response speed and operation stability of the drive control of the synchronous motor and reduce the complexity of the drive control of the synchronous motor.

[0141] In a third aspect, this application also provides a synchronous motor drive system, which includes: a synchronous motor and a current source inverter for driving the synchronous motor. The current source inverter is configured to adopt the inverter drive control method described above, thereby improving the response speed and operation stability of the synchronous motor and reducing the complexity of the drive system.

[0142] It will be understood that the term "exemplary" as used herein means "serving as an example, instance, or illustration". Any embodiment described as "exemplary" is not necessarily preferred or superior to other embodiments and / or does not exclude incorporating features of other embodiments. It should be understood that certain features of the present application described in the context of separate embodiments may also be provided in combination in a single embodiment. Conversely, the various features of the present application described in the context of a single embodiment may also be provided separately or in any suitable combination or as any other described embodiment of the present application.

[0143] In the description of the present application, unless otherwise specified, " / " means "or", for example, A / B may mean A or B. The "and / or" herein is merely an associative relationship describing associated objects, indicating that there can be three relationships, for example, A and / or B, which can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, "at least one" means one or more, and "a plurality" means two or more. The terms "first", "second", etc. do not limit the quantity and execution order, and the terms "first", "second", etc. do not necessarily mean different.

[0144] The above-disclosed are only the preferred embodiments of the present application, but they are not intended to limit the scope of the rights of the present application. Those of ordinary skill in the art can understand that within the spirit and scope of the present application and the appended claims, changes, modifications, substitutions, combinations, and simplifications should all be equivalent replacement methods and still fall within the scope covered by the invention.

Claims

1. An inverter drive control method for a synchronous motor, characterized in that, The synchronous motor is driven by a current source inverter, and the drive control method includes: Construct the mathematical model of the synchronous motor in dq coordinate system to obtain the actual currents of the synchronous motor on the d axis and q axis, and the actual voltages on the d axis and q axis; Define state variables, where the state variables include those characterizing the synchronous motor d the difference between the actual current of the d axis and the q reference value of the axis current, a first state variable characterizing the synchronous motor q the difference between the actual current of the d axis and the d reference value of the axis current, a second state variable characterizing the synchronous motor q the difference between the actual voltage of the q axis and the reference value of the axis voltage, a third state variable characterizing the synchronous motor; a fourth state variable of the difference between the actual voltage of the Construct a Lyapunov function according to the first to fourth state variables; Make the Lyapunov function satisfy global asymptotic stability at the equilibrium point to obtain the voltage reference values of the synchronous motor on the d axis and q axis; Based on the voltage reference values of the synchronous motor on the d axis and the q axis, the ideal given value of the output current on the AC side of the current source inverter is calculated, and the driving signals of the inverter bridge switching tubes in the inverter are obtained by conversion based on the ideal given value of the output current; The Lyapunov function is expressed by the following formula: ； In the formula, L d represents the d axis inductance of the synchronous motor, L q represents the q axis inductance of the synchronous motor, C represents the shunt capacitance of the synchronous motor, x 1 represents the first state variable, x 2 represents the second state variable, x 3 represents the third state variable, x 4 represents the fourth state variable, V(x) represents the Lyapunov function; By making the Lyapunov function satisfy the following four conditions, so as to satisfy global asymptotic stability at the equilibrium point. The conditions include: ； ； ； ； Among them, represents the derivative of the Lyapunov function.

2. The inverter drive control method for a synchronous motor according to claim 1, wherein When the following conditions are met, enable Meet , the conditions include: ； Among them, K d represents the synchronous motor d axis voltage damping regulation parameter, K q represents the synchronous motor q axis voltage damping regulation parameter, represents the fluctuation value of the dq axis current output by the AC side of the inverter in the d coordinate system compared with the steady-state current, represents the fluctuation value of the dq axis current output by the AC side of the inverter in the q coordinate system compared with the steady-state current.

3. The inverter drive control method for a synchronous motor according to claim 2, wherein Calculate the ideal given value of the output current on the AC side of the current source inverter through the following formula: ； ； Wherein, , , is the permanent magnet flux linkage, L d represents the d axis inductance of the synchronous motor, L q represents the q axis inductance of the synchronous motor, I d represents the dq axis current value output by the AC side of the inverter in the d coordinate system at steady state, I q represents the dq axis current value output by the AC side of the inverter in the q coordinate system at steady state, R represents the phase resistance of the synchronous motor, represents the electrical angular velocity obtained by converting the given speed of the motor, C represents the shunt capacitance of the synchronous motor, i * ds represents the d axis current reference value of the said synchronous motor, i * qs represents the q axis current reference value of the said synchronous motor, u * ds represents the d axis voltage reference value of the said synchronous motor, u * qs represents the q axis voltage reference value of the said synchronous motor, u ds represents the d axis actual voltage of the said synchronous motor, u qs represents the q axis actual voltage of the said synchronous motor, e ds represents the d axis back electromotive force of the said synchronous motor, e qs represents the q axis back electromotive force of the said synchronous motor.

4. The inverter drive control method for a synchronous motor according to claim 2, wherein Calculate the ideal given value of the output current on the AC side of the current source inverter through the following formula: ； ； Wherein, , , is the permanent magnet flux linkage, L d represents the d axis inductance of the synchronous motor, L q represents the q axis inductance of the synchronous motor, I d represents the dq axis current value output by the AC side of the inverter in the d coordinate system at steady state, I q represents the dq axis current value output by the AC side of the inverter in the q coordinate system at steady state, R represents the phase resistance of the synchronous motor, represents the electrical angular velocity obtained by converting the given speed of the motor, C represents the shunt capacitance of the synchronous motor, i * ds represents the d axis current reference value of the synchronous motor, i * qs represents the q axis current reference value of the synchronous motor, u * ds represents the d axis voltage reference value of the synchronous motor, u * qs represents the q axis voltage reference value of the synchronous motor, u ds represents the d axis actual voltage of the synchronous motor, u qs represents the q axis actual voltage of the synchronous motor, K Id represents the d axis current damping adjustment parameter of the synchronous motor, K Iq represents the q axis current damping adjustment parameter of the synchronous motor, e ds represents the d axis back electromotive force of the synchronous motor, e qs represents the q axis back electromotive force of the synchronous motor.

5. The inverter drive control method for a synchronous motor according to claim 3 or 4, characterized in that The d axis current reference value i * ds is set to 0, and the q axis current reference value i * qs is obtained by a PI controller through a speed closed-loop.

6. The inverter drive control method of the synchronous motor according to claim 3 or 4, characterized in that, The inverter drive control method further includes: Construct the state - space equation of the system, and adjust the d axis and q the voltage damping adjustment parameters of the axis, or adjust the d axis and q the voltage damping adjustment parameters and current damping adjustment parameters of the axis, so that all poles of the state - space equation are distributed in the left - hand plane.

7. The inverter drive control method for a synchronous motor according to claim 6, wherein The state space equation is expressed by the following formula: ； Among them, , ; ； ； In the formula, represents the derivative of the state variable, X represents the state variable matrix, U represents the input quantity matrix, A and B represent the parameter matrices, R represents the phase resistance of the synchronous motor, represents the synchronous motor d axis voltage damping regulation parameter, represents the synchronous motor q axis voltage damping regulation parameter, represents the synchronous motor d axis current damping regulation parameter, represents the synchronous motor q axis current damping regulation parameter, represents the electrical angular velocity obtained by converting the given speed of the motor, C represents the shunt capacitor of the synchronous motor, i ds represents the d actual axis current of the synchronous motor, i qs represents the q actual axis current of the synchronous motor, u ds represents the d actual axis voltage of the synchronous motor, u qs represents the q actual axis voltage of the synchronous motor, L d represents the d axis inductance of the synchronous motor, L q represents the q axis inductance of the synchronous motor.

8. An inverter, characterized in that, The inverter includes a current source inverter circuit and a controller. The inverter is used to drive a synchronous motor, and the controller is configured to adopt the inverter drive control method according to any one of claims 1 to 7.

9. A synchronous motor drive system, characterized in that, The synchronous motor drive system includes: a synchronous motor, and a current source inverter for driving the synchronous motor. The current source inverter is configured to adopt the inverter drive control method according to any one of claims 1 to 7.

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