A cross-axis voltage-regulating field-weakening control method

Abstract

A kind of cross-axis voltage-regulating flux-weakening control method: motor information is collected, three-phase current of output side is converted into d-q axis current, obtains electric angular velocity, d-q axis voltage is solved, obtains 6-way pulse signal for controlling the switching of power device in static frequency converter using space vector modulation strategy;According to voltage, current limit circle formula, the amplitude of stator current and stator voltage and d-q axis current given value is limited;Generate q-axis voltage given value;Q-axis flux-weakening control error is analyzed;The cross-axis voltage equation of surface-mounted permanent magnet synchronous motor is used as cross-axis circuit model;Design cross-axis flux-weakening controller;Introduce current loop first-order inertia link, obtain equivalent flux-weakening controller;The reference tracking performance of q-axis voltage is analyzed, and the control speed of q-axis voltage is realized by adjusting the size of cross-axis flux-weakening loop bandwidth.The flux-weakening controller parameter setting of the present application is simple, voltage amplitude fluctuation is small, system stability is strong, and flux-weakening loop bandwidth can be adjusted very conveniently.

Description

Technical Field

[0001] This invention relates to a quadrature-axis voltage regulation and field weakening control method. In particular, it relates to a quadrature-axis voltage regulation and field weakening control method for surface-mounted permanent magnet synchronous motors, based on a quadrature-axis field weakening algorithm and a voltage amplitude fluctuation control stage. Background Technology

[0002] Surface-mounted permanent magnet synchronous motors (PMSMs) offer high power density, low rotor magnetic field harmonic content, and accurate mathematical models, resulting in simpler and more intuitive control, making them widely used in electric drive systems. Generally, electric drive applications require motors with a wide speed range, necessitating the application of field-weakening control algorithms in the motor control system. Furthermore, during actual field-weakening operation, the motor is often under acceleration and loading conditions, and the inverter DC bus voltage is not constant. To avoid current loop saturation, the field-weakening loop needs a fast voltage amplitude response and strong resistance to load torque disturbances. Voltage feedback field-weakening algorithms are independent of motor parameters, have a simple control structure, zero steady-state error in voltage amplitude response, and strong algorithm portability, making them widely used in industrial fields. However, traditional voltage feedback field-weakening loops are strongly coupled nonlinear systems, making it difficult to provide a theoretical basis for field-weakening parameter tuning using linear analysis methods. In practice, fixed field-weakening controller parameters obtained through empirical parameter tuning methods cannot guarantee optimal dynamic, steady-state, and load disturbance resistance performance of the field-weakening loop in the constant power region, and may even lead to system instability.

[0003] Current research on voltage feedback field weakening algorithms mainly focuses on the linearization of the field weakening loop. To achieve linearization analysis of the field weakening loop, the main solution currently is to use Taylor series to analyze the voltage amplitude. and The relationship was approximated by a first order, until... and The nonlinear gain expression between them was then derived; subsequently, the magnetic weakening loop was modeled using small-signal analysis, and then an adaptive gain coefficient was introduced to eliminate the nonlinear gain expression. and The nonlinear gain between them; finally, the field weakening PI parameter is tuned by the zero-pole cancellation principle, and the field weakening loop is equivalent to a first-order system. Therefore, the bandwidth of the field weakening loop can be easily adjusted by the field weakening controller parameter. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a cross-axis voltage regulation magnetic weakening control method that can conveniently adjust the bandwidth of the weak magnetic ring.

[0005] The technical solution adopted in this invention is: a cross-axis voltage regulation and field weakening control method, comprising the following steps:

[0006] 1) Collect the rotor position angle of the motor Three-phase current on the motor output side DC bus voltage on the inverter side The output three-phase current is transformed by coordinate transformation. Converted to dq axis current Regarding the rotor position angle Differentiating yields the electric angular velocity. Then, based on the motor's dq axis current... and electric angular velocity Find the voltage along the dq axis. Finally, a space vector modulation strategy is adopted to obtain 6 pulse signals for controlling the switching of power devices in the static inverter;

[0007] 2) Limit the given values ​​of stator current, stator voltage, and dq-axis current according to the voltage and current limit circle formulas;

[0008] 3) Generate q-axis voltage setpoint ;

[0009] 4) Analysis of the q-axis field weakening control error shows that the q-axis field weakening control error approaches zero;

[0010] 5) The quadrature-axis voltage equation of the surface-mounted permanent magnet synchronous motor is used as the quadrature-axis circuit model;

[0011] 6) Design a quadrature-axis field weakening controller;

[0012] 7) Introducing a first-order inertial element in the current loop yields an equivalent field weakening controller;

[0013] 8) Analyze the q-axis voltage The reference tracking performance is improved by adjusting the bandwidth of the quadrature axis field weakening loop to control the speed of the q-axis voltage, thereby achieving the purpose of field weakening adjustment of the surface-mounted permanent magnet synchronous motor.

[0014] 9) Voltages along the dq axes Add a current controller to reduce the dq axis voltage. , Voltage amplitude fluctuation.

[0015] This invention provides a quadrature-axis voltage-regulating field weakening control method, which has advantages such as simple parameter tuning of the field weakening controller, small voltage amplitude fluctuation, and strong system stability. It allows for convenient adjustment of the field weakening loop bandwidth, solving the problem of poor stability in the field weakening control system when the rotational speed changes over a wide range. Compared to other voltage-based field weakening control methods, this method simplifies the quadrature-axis field weakening loop model, effectively improves the performance of the voltage feedback field weakening control algorithm, and adds a current controller to effectively reduce voltage fluctuations. Attached Figure Description

[0016] Figure 1 This is the block diagram of the cross-axis voltage regulation and field weakening control.

[0017] Figure 2 It is a quadrature-axis voltage feedback field weakening control structure;

[0018] Figure 3 It is a dynamic adjustment process based on voltage commands;

[0019] Figure 4 It is a cross-axis weak magnetic loop model;

[0020] Figure 5 It is an equivalent cross-axis weak magnetic loop model. Detailed Implementation

[0021] The following detailed description of a cross-axis voltage regulation and field weakening control method of the present invention, in conjunction with embodiments and accompanying drawings, provides a detailed explanation.

[0022] The present invention provides a cross-axis voltage regulation and field weakening control method, comprising the following steps:

[0023] 1) such as Figure 1 As shown in the signal processing section, the rotor position angle of the motor is acquired. Three-phase current on the motor output side DC bus voltage on the inverter side The output three-phase current is transformed by coordinate transformation. Converted to dq axis current Regarding the rotor position angle Differentiating yields the electric angular velocity. Then, based on the motor's dq axis current... and electric angular velocity Find the voltage along the dq axis. Finally, the voltages along the dq axes... Performing the inverse PARK transformation yields - shaft voltage , A space vector modulation (SVPWM) strategy is adopted to obtain six pulse signals for controlling the switching of power devices in the static inverter.

[0024] The dq axis voltage This is obtained by neglecting the stator resistance using the following steady-state equation:

[0025] (1)

[0026] (2)

[0027] In the formula, This represents the dq-axis voltage of the motor under steady-state conditions. For the stator inductance of the motor; Electric angular velocity; For permanent magnet flux linkage; This represents the dq-axis current.

[0028] The inverse PARK transformation formula is as follows:

[0029] (3).

[0030] 2) Limit the given value of the dq-axis current according to the voltage and current limit circle formula;

[0031] Due to limitations imposed by the inverter DC bus voltage and the maximum value of the motor stator current, when the motor operates in the field weakening region, it is necessary to limit the stator current and stator voltage. Step 2) The formula for limiting the stator current and stator voltage is as follows:

[0032] (4)

[0033] (5)

[0034] In the formula, This refers to the voltage across the dq axis of the motor. For dq axis current; This represents the maximum value of the motor stator voltage. This represents the maximum value of the motor stator current.

[0035] Substituting formulas (1) and (2) into formula (3), we obtain the voltage limit circle relationship formed by the dq axis current of the motor stator as follows:

[0036] (6);

[0037] To ensure the optimal operating trajectory of the current in different magnetic weakening regions, it is first necessary to ensure that the current command is located on the voltage limit circle boundary. This requires limiting the current setpoints of the dq axes separately, and the limiting formula is as follows:

[0038] (7)

[0039] (8)

[0040] In the formula, Set the d-axis current of the motor to a given value. The given value for the q-axis current of the motor; such as Figure 1 The current command limiting section is shown. , The motor dq-axis current limiting setpoint is generated by limiting the amplitude. , .

[0041] Depend on Figure 1 A current loop PI controller is designed in conjunction with feedforward decoupling control. The current loop uses a PI parameter regulator combined with a feedforward decoupling control strategy. Due to the stator current... Cross-coupled electromotive forces are generated on the q-axis and d-axis respectively, requiring... , By decoupling, the dq-axis voltage equations can be obtained as follows:

[0042] (9)

[0043] (10);

[0044] In the formula, This is the proportional gain of the dq-axis current loop PI controller. , This is the integral gain of the dq-axis current loop PI controller.

[0045] 3) Generate q-axis voltage setpoint ;include:

[0046] Depend on Figure 2 Therefore, when the motor operating speed is below the base speed, the following applies: For speeds above the base velocity, field weakening control is used.

[0047] When the motor is running in the field weakening zone, the stator voltage setpoint of the motor is... Through the collected , Generating motor stator voltage The formula is shown below:

[0048] (11)

[0049] Thus, the given value of the motor's q-axis voltage is obtained, as shown in the following formula:

[0050] (12).

[0051] 4) Analysis of the q-axis field weakening control error shows that the q-axis field weakening control error approaches zero; including:

[0052] like Figure 2 As shown, u1 is defined as the first voltage vector command when the motor is in steady state, with an amplitude of , angle is ;definition This is the second voltage vector command when the current controller saturates, and the magnitude difference between the first voltage vector command u1 and the second voltage vector command u2 is... The angle difference is ;definition The third voltage vector command is the output of the field weakening controller when the current controller saturates; the control error of the dq-axis field weakening control algorithm is defined as the third voltage vector command. With the first voltage vector command The amplitude difference between them, using This indicates that u1 and... amplitude difference The expression:

[0053] (13);

[0054] For motor control, the field weakening controller begins to operate in the next control cycle after the current controller reaches saturation. , As the value approaches zero, the field weakening control error also approaches zero. Based on the above analysis, we can conclude that the q-axis field weakening control error approaches zero.

[0055] 5) The quadrature-axis voltage equation of the surface-mounted permanent magnet synchronous motor is used as a quadrature-axis circuit model, and an adaptive coefficient is introduced; the quadrature-axis circuit model is as follows:

[0056] (14)

[0057] in, Represented as the current q-axis voltage; R is the motor stator winding resistance; and This refers to the dq-axis current of the motor. For the stator inductance of the motor; Represents electric angular velocity. For permanent magnet flux linkage; The output noise of the system is used to represent the effect of torque disturbance on the field weakening system; The load disturbance of the system is used to represent the impact of the dynamic process of motor speed on the field weakening system; This is the gain between the quadrature-axis voltage and the direct-axis current.

[0058] From formula (14), we can obtain: quadrature axis voltage With direct-axis current Gain between As the rotational speed increases, an adaptive coefficient for cross-axis field weakening gain is introduced. :

[0059] (15)

[0060] Due to the cross-axis magnetic weakening gain adaptive coefficient Unaffected and The effect of speed changes can be effectively reduced. and The impact.

[0061] 6) Design a quadrature-axis field weakening controller;

[0062] like Figure 3 As shown, the expression for the quadrature-axis field weakening controller is as follows:

[0063] (16)

[0064] in, This is expressed as the q-axis voltage setpoint, where s is a complex number. Indicates to Perform integration processing; These are the proportional parameters for the quadrature-axis field weakening controller; These are the integral parameters of the quadrature-axis field weakening controller; The given value for the d-axis current of the motor; Represented as the current q-axis voltage; The cross-axis magnetic weakening gain adaptive coefficient;

[0065] Based on the quadrature-axis circuit model, current loop, and field weakening loop bandwidth, and taking the principle of pole-zero cancellation between the first-order inertial element of the current loop and the field weakening PI controller, the proportional and integral parameters of the quadrature-axis field weakening controller are tuned, as shown in the following expressions:

[0066] (17)

[0067] (18);

[0068] in, This is the bandwidth of the quadrature axis weak magnetic loop; The current loop bandwidth is used to output the d-axis current setpoint through the field weakening controller. The d-axis current is obtained through a first-order inertial element of the current loop. The formula for a first-order inertial element in a current loop is as follows:

[0069] (19)

[0070] Substituting formulas (16), (17), and (18) into formula (19), we obtain the equivalent field weakening controller as follows:

[0071] (20).

[0072] 7) Introducing a first-order inertial element into the current loop, we obtain the following: Figure 4 The equivalent field weakening controller shown includes:

[0073] Substituting formula (20) into formula (14) yields:

[0074] (twenty one)

[0075] Formula (21) gives the q-axis voltage With q-axis voltage setpoint System output noise System load disturbance Expressions between;

[0076] Performing a Laplace transform on equation (21), we obtain the voltage on the q-axis at time t. Transformation from the time domain to the complex domain q-axis voltage complex field expression The formula is as follows:

[0077] (twenty two).

[0078] 8) Analyze the q-axis voltage The reference tracking performance is improved by adjusting the bandwidth of the quadrature-axis field weakening loop to control the speed of q-axis voltage, thereby achieving the purpose of field weakening regulation of the surface-mounted permanent magnet synchronous motor; including:

[0079] Set the q-axis voltage value Modeling as a step signal Find the q-axis voltage. q-axis voltage setpoint The frequency domain and time domain expressions are as follows:

[0080] (twenty three)

[0081] (twenty four)

[0082] Thus, the bandwidth of the quadrature axis weak magnetic loop is obtained. The larger the value, the higher the q-axis voltage. The faster the response, the better, by adjusting the bandwidth of the quadrature axis magnetic weakening loop. The size of the voltage on the q-axis is used to control the voltage. The speed of the control is adjusted to achieve the purpose of field weakening adjustment of the surface-mounted permanent magnet synchronous motor.

[0083] 9) Add a voltage amplitude fluctuation suppression section, through the dq axis voltage The current controller can reduce the dq axis voltage. , Voltage amplitude fluctuation; d-axis voltage The expression is as follows:

[0084] (25)

[0085] Current controller Substituting into formulas (14) and (25), where This represents the difference between the current setpoint and the actual current value; it yields the dq-axis voltage after adding a current controller. , The expression is as follows:

[0086] (26)

[0087] (27);

[0088] in, For the integral parameters of the current controller; These are the proportional parameters of the current controller; adding a current controller effectively reduces the dq-axis voltage. , Voltage amplitude fluctuation.

Claims

1. A cross-axis voltage regulation and field weakening control method, characterized in that, The steps include the following: 1) Collect the rotor position angle of the motor Three-phase current on the motor output side DC bus voltage on the inverter side The output three-phase current is transformed by coordinate transformation. Converted to dq axis current Regarding the rotor position angle Differentiating yields the electric angular velocity. Then, based on the motor's dq axis current... and electric angular velocity Find the voltage along the dq axis. Finally, a space vector modulation strategy is adopted to obtain 6 pulse signals for controlling the switching of power devices in the static inverter; 2) Limit the given values ​​of stator current, stator voltage, and dq-axis current according to the voltage and current limit circle formulas; 3) Generate q-axis voltage setpoint ; 4) Analysis of the q-axis field weakening control error shows that the q-axis field weakening control error approaches zero. 5) The quadrature-axis voltage equation of the surface-mounted permanent magnet synchronous motor is used as the quadrature-axis circuit model; the quadrature-axis circuit model is as follows: （11）； in, Represents the current q-axis voltage; R is the motor stator winding resistance; and This refers to the dq-axis current of the motor. For the stator inductance of the motor; Represents electric angular velocity. For permanent magnet flux linkage; The output noise of the system is used to represent the effect of torque disturbance on the field weakening system; The load disturbance of the system is used to represent the impact of the dynamic process of motor speed on the field weakening system; This is the gain between the quadrature-axis voltage and the direct-axis current. Introducing cross-axis magnetic weakening gain adaptive coefficient : （12）； Due to the adaptive coefficient of cross-axis magnetic weakening gain Unaffected and The effect of speed changes can be effectively reduced. and The impact; 6) Design a quadrature-axis field weakening controller; the expression for the quadrature-axis field weakening controller is as follows: （13）； in, This is expressed as the q-axis voltage setpoint, where s is a complex number. Indicates to Perform integration processing; These are the proportional parameters for the quadrature-axis field weakening controller; These are the integral parameters of the quadrature-axis field weakening controller; The given value for the d-axis current of the motor; Represented as the current q-axis voltage; The cross-axis magnetic weakening gain adaptive coefficient; Based on the quadrature-axis circuit model, current loop, and field weakening loop bandwidth, and taking the principle of pole-zero cancellation between the first-order inertial element of the current loop and the field weakening PI controller, the proportional and integral parameters of the quadrature-axis field weakening controller are tuned, as shown in the following expressions: （14）； （15）； in, This is the bandwidth of the quadrature axis weak magnetic loop; The current loop bandwidth is used to output the d-axis current setpoint through the field weakening controller. The d-axis current is obtained through a first-order inertial element of the current loop. The formula for a first-order inertial element in a current loop is as follows: （16）； Substituting formulas (13), (14), and (15) into formula (16), we obtain the equivalent field weakening controller as follows: （17）； 7) Introducing a first-order inertial element in the current loop yields an equivalent field weakening controller; 8) Analyze the q-axis voltage The reference tracking performance is improved by adjusting the bandwidth of the quadrature axis field weakening loop to control the speed of the q-axis voltage, thereby achieving the purpose of field weakening adjustment of the surface-mounted permanent magnet synchronous motor. 9) Voltages along the dq axes Add a current controller to reduce the dq axis voltage. , Voltage amplitude fluctuation.

2. The quadrature-axis voltage regulation and field weakening control method according to claim 1, characterized in that, Step 1) The dq axis voltage This is obtained by neglecting the stator resistance using the following steady-state equation: （1）； （2）； In the formula, This represents the dq-axis voltage of the motor under steady-state conditions. For the stator inductance of the motor; Electric angular velocity; For permanent magnet flux linkage; This represents the dq-axis current.

3. The quadrature-axis voltage regulation and field weakening control method according to claim 1, characterized in that, Step 2) The formula for limiting the stator current and stator voltage is as follows: （3）； （4）； In the formula, This refers to the voltage across the dq axis of the motor. For dq axis current; This represents the maximum value of the motor stator voltage. This represents the maximum value of the motor stator current. Substituting formulas (1) and (2) into formula (3), we obtain the voltage limit circle relationship formed by the stator dq axis current of the motor as follows: （5）； To ensure the optimal operating trajectory of the current in different magnetic weakening regions, it is first necessary to ensure that the current command is located on the voltage limit circle boundary. This requires limiting the current setpoints of the dq axes separately, and the limiting formula is as follows: （6）； （7）； In the formula, Set the d-axis current of the motor to a given value. This is the given value for the q-axis current of the motor.

4. The quadrature-axis voltage regulation and field weakening control method according to claim 1, characterized in that, Step 3) includes: When the motor is running in the field weakening zone, the stator voltage setpoint of the motor is... Through the collected , Generating motor stator voltage The formula is shown below: （8）； Thus, the given value of the motor's q-axis voltage is obtained, as shown in the following formula: （9）。 5. The quadrature-axis voltage regulation and field weakening control method according to claim 1, characterized in that, Step 4) includes: Define u1 as the first voltage vector command when the motor is in steady state, with an amplitude of , angle is ;definition This is the second voltage vector command when the current controller saturates, and the magnitude difference between the first voltage vector command u1 and the second voltage vector command u2 is... The angle difference is ;definition The third voltage vector command is the output of the field weakening controller when the current controller saturates; the control error of the dq-axis field weakening control algorithm is defined as the third voltage vector command. With the first voltage vector command The amplitude difference between them, using This indicates that u1 and... amplitude difference The expression: （10）； Therefore, it can be concluded that the q-axis field weakening control error approaches zero.

6. The quadrature-axis voltage regulation and field weakening control method according to claim 1, characterized in that, Step 7) includes: Substituting formula (17) into formula (11) yields: （18）； Formula (18) gives the q-axis voltage. With q-axis voltage setpoint System output noise System load disturbance Expressions between; Performing a Laplace transform on equation (18), we obtain the voltage on the q-axis at time t. Transformation from the time domain to the complex domain q-axis voltage complex field expression The formula is as follows: （19）。 7. The quadrature-axis voltage regulation and field weakening control method according to claim 1, characterized in that, Step 8) includes: Set the q-axis voltage value Modeling as a step signal Find the q-axis voltage. q-axis voltage setpoint The frequency domain and time domain expressions are as follows: （20）； （21）； Thus, the bandwidth of the quadrature axis weak magnetic loop is obtained. The larger the value, the higher the q-axis voltage. The faster the response, the better, by adjusting the bandwidth of the quadrature axis magnetic weakening loop. The magnitude of the voltage is used to control the q-axis voltage. The speed of the control is adjusted to achieve the purpose of field weakening adjustment of the surface-mounted permanent magnet synchronous motor.

8. The quadrature-axis voltage regulation and field weakening control method according to claim 7, characterized in that, Step 9) Adjust the dq axis voltage Add a current controller, d-axis voltage The expression is as follows: （22）； Current controller Substituting into formulas (11) and (21), where This represents the difference between the given current value and the actual current value. Obtain the dq-axis voltage after adding a current controller , The expression is as follows: （23）； （24）； in, For the integral parameters of the current controller; These are the proportional parameters of the current controller; adding a current controller effectively reduces the dq-axis voltage. , Voltage amplitude fluctuation.

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