A vector control method based on reactive current control of permanent magnet synchronous motor

Abstract

The present invention proposes a vector control method based on reactive current control of a permanent magnet synchronous motor, which belongs to the technical field of permanent magnet synchronous motor control. First, the active current setting and reactive current setting are determined; second, the active current and reactive current are calculated from the feedback current; third, the given amplitude of the input voltage of the control power device is obtained; third, the frequency of the input voltage of the control power controller is obtained; finally, the angle θ between the rotor position and the A-phase winding is obtained by rotor position detection, and the direction of the magnetic field generated by the running current of the motor to be controlled is calculated, so that the magnetic field generated by the stator current is orthogonal to the rotor magnetic field, thereby realizing the vector control of the permanent magnet synchronous motor. The technical problem of complex algorithm of high-performance permanent magnet synchronous motor control existing in the prior art is solved.

Description

Technical Field

[0001] The present application relates to a permanent magnet synchronous motor control, and in particular to a vector control method based on reactive current control of a permanent magnet synchronous motor, belonging to the technical field of permanent magnet synchronous motor control. Background Art

[0002] Permanent magnet synchronous motors are increasingly widely used in the field of industrial control due to their high operating efficiency and high power density, especially in the field of high-precision control, where they have become dominant. Since the mathematical models of AC motors have the characteristics of nonlinearity and strong coupling, their control algorithms are complex, and the motor control performance is easily affected by parameter changes, that is, the existing permanent magnet synchronous motor vector control requires Park and Clark transformations to achieve orthogonal decoupling of the magnetic field, which is computationally intensive and parameter-dependent, and it is not easy to obtain high performance of system control. The present invention provides a technical solution for motor vector control that utilizes the characteristics that the active current and reactive current obtained by current decomposition of permanent magnet synchronous motors can independently control the torque and magnetic field, and the characteristics that the voltage phase can control the direction of the magnetic field. Summary of the invention

[0003] A brief overview of the present invention is provided below in order to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to identify key or important parts of the present invention, nor is it intended to limit the scope of the present invention. Its purpose is merely to present certain concepts in a simplified form as a prelude to a more detailed description discussed later.

[0004] In view of this, in order to solve the technical problem of low control performance of permanent magnet synchronous motors in the prior art, the present invention provides a vector control method based on reactive current control of permanent magnet synchronous motors.

[0005] A vector control method based on reactive current control of a permanent magnet synchronous motor comprises the following steps:

[0006] Step 1: Determine the active current setting and reactive current setting;

[0007] Step 2: Calculate active current and reactive current from feedback current;

[0008] Step 3, obtaining a given amplitude of the input voltage of the control power device;

[0009] Step 4, obtaining the frequency of the input voltage of the control power controller;

[0010] Step 5. Obtain the angle θ between the rotor position and the A-phase winding by rotor position detection, determine the phase of the voltage to control the direction of the magnetic field generated by the motor running current, so that the magnetic field generated by the stator current is orthogonal to the rotor magnetic field, thereby realizing vector control of the permanent magnet synchronous motor.

[0011] Preferably, the specific method for determining the active current and reactive current given in step one is that the speed controller determines the active current given according to the real-time speed difference; the reactive current is obtained by querying experimental data from the speed given and the real-time motor speed, and the reactive current is determined according to the speed given to determine the reactive current given required for the control process.

[0012] Preferably, the specific method for obtaining the given amplitude of the input voltage of the control power device described in step three is to calculate the active current and reactive current from the feedback current, compare them with the given active current and the given reactive current respectively, and input them to the current controller to obtain the given amplitude of the input voltage of the control power controller.

[0013] Preferably, the specific method for obtaining the frequency of the input voltage of the control power controller described in step 4 is to determine the frequency of the input voltage given by the control power controller according to the speed given.

[0014] Preferably, the magnetic field oriented control described in step five is determined by the voltage phase: the rotor magnetic field position is obtained by rotor position detection, and it can be known that the position of the stator current magnetic field needs to be controlled to achieve orthogonal control of the stator magnetic field and the rotor magnetic field, that is, the three-phase voltage phase is controlled to achieve orthogonal control of the magnetic field generated by the permanent magnet synchronous motor current and the rotor magnetic field.

[0015] The amplitude, frequency and phase of the modulation voltage signal that controls the output voltage of the power controller are determined, thereby controlling the operation of the permanent magnet synchronous motor.

[0016] The beneficial effects of the present invention are as follows: The present invention uses the current response as the key control parameter, and combines the motor and system rated point performance experimental data as the control reference, so that the motor control system performance has the characteristic of being independent of the motor parameters. The present invention is different from the traditional vector control. It controls the torque and magnetic field of the motor by calculating the active current and reactive current, and directly controls the voltage phase according to the rotor magnetic field position and the power factor angle so that the magnetic field generated by the stator current is orthogonal to the rotor magnetic field. It solves the problems of complex permanent magnet synchronous motor control algorithm and large amount of calculation in the prior art, and provides a technical solution that can achieve high-performance control of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0018] Figure 1 is a schematic diagram of the method flow chart;

[0019] Figure 2 It is the schematic diagram of control principle;

[0020] Figure 3 is the phasor diagram of the permanent magnet synchronous motor;

[0021] Figure 4 Schematic diagram of voltage and current zero crossing and peak value corresponding to obtain phase difference;

[0022] Figure 5 Schematic diagram for calculating power factor angle;

[0023] Figure 6 Schematic diagram for determining the rotor magnetic field position. DETAILED DESCRIPTION

[0024] In order to make the technical solutions and advantages in the embodiments of the present application more clearly understood, the exemplary embodiments of the present application are further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than an exhaustive list of all the embodiments. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0025] Example 1, reference Figure 1-Figure 6 The present embodiment describes a vector control method based on reactive current control of a permanent magnet synchronous motor, comprising the following steps:

[0026] Step 1: Determine the active current setting and reactive current setting;

[0027] Step 2: Feedback current ( Figure 2 In ) Calculate active current and reactive current;

[0028] Step 3, obtaining a given amplitude of the input voltage of the control power device;

[0029] Step 4, obtaining the frequency of the input voltage of the control power controller;

[0030] Step 5: Obtain the angle θ between the rotor position and the A-phase winding by detecting the rotor position ( Figure 2 In ∫, see Figure 6 The d-axis direction is the direction of the rotor magnetic field, and the ds-axis direction is the direction of the magnetic field generated by the motor current to be controlled). The voltage phase is calculated to control the direction of the magnetic field generated by the motor running current, so that the magnetic field generated by the stator current is orthogonal to the rotor magnetic field, thereby realizing vector control of the permanent magnet synchronous motor.

[0031] Specifically, the current of a permanent magnet synchronous motor running at a given speed contains two components, namely, the active current component that controls the active power of the motor and the reactive current component that controls the reactive power of the motor. When the voltage controlling the motor is less than the back electromotive force of the motor, the reactive current plays a demagnetizing role, and the current phase leads the voltage; when the voltage controlling the motor is greater than the back electromotive force of the motor, the reactive current plays a magnetizing role, and the current phase lags behind the voltage; when the voltage and current phases of the motor are the same, the reactive current is controlled to be zero. The voltage amplitude control law based on the characteristics of reactive current control is obtained.

[0032] Active power is directly related to the output torque of the motor. When the speed is constant, controlling the active current can control the motor torque. Reactive power is related to the energy of the motor magnetic field. Controlling the reactive current can control the air gap magnetic field amplitude. Therefore, the phase difference between voltage and current is obtained from the characteristics of the electrical response of the permanent magnet synchronous motor, and then the current component that controls the torque and the current component that controls the magnetic field are calculated.

[0033] Torque and magnetic field control are determined by the speed loop and reactive current comparison control link: the size of the active current component is determined by the output torque of the speed controller according to the speed response requirements of the control system; the size of the reactive current component is determined by the reactive current reference obtained by the control system based on the speed setting and real-time speed query experimental data.

[0034] The field-oriented control is determined by the voltage phase: the rotor magnetic field position is obtained from the rotor position detection, and it can be known that the position of the stator current magnetic field needs to be controlled to achieve orthogonal control of the stator magnetic field and the rotor magnetic field, that is, the three-phase voltage phase is controlled to achieve orthogonal control of the magnetic field generated by the permanent magnet synchronous motor current and the rotor magnetic field.

[0035] Two methods for determining active current and reactive current that can verify the accuracy of calculations: 1. There are two zero-crossing points and two peak points in one cycle of AC voltage, twelve identifiable points for three-phase voltage, and twelve identifiable points for three-phase current. The phase difference and current amplitude corresponding to voltage and current can be obtained when the operating frequency is certain, thereby calculating the active current component and reactive current component of the current; 2. Detect the real-time values ​​of the two-phase current to calculate the power factor angle and current amplitude. The phase difference between voltage and current is equal to the power factor angle. According to the operating characteristics of the permanent magnet synchronous motor in claim 1, the direction of the magnetic field generated by the stator current can be controlled by controlling the voltage phase; controlling the active current component i P It can control the motor torque and reactive current component i Q The air gap magnetic field amplitude can be controlled.

[0036] The direction of the magnetic field generated by the stator current is achieved by controlling the phase of the motor's three-phase voltage according to the detected rotor position, and the magnetic field amplitude is achieved by controlling the three-phase voltage. The three-phase voltage phase that is easy to identify is determined by the special point of the angle θ between the rotor position and the A-phase winding, such as 0, 90, 30, 60, etc. electrical angles in a quarter cycle of the AC voltage.

[0037] After the temperature rise of the motor is stable under rated load, the experiment tests the voltage, power factor angle and load current values ​​of several typical frequency points of the permanent magnet synchronous motor where the current and voltage phase difference is zero, the current phase leads the voltage by 45° electrical angle, and the current phase lags the voltage phase by 45°. At this time, the resistance and inductance parameters in the motor parameters are the real working state, which provides an accurate mathematical model for the control constructed with this model, and is the condition for achieving high-precision control, that is, providing accurate reference data for controlling the target torque and target magnetic field.

[0038] The calculation of the two key current components based on the current response characteristics makes the permanent magnet synchronous motor vector control mathematical model independent of the motor parameters and realizes independent control of the motor's magnetic field and torque.

[0039] The phase difference between the current and voltage during actual operation of the motor is calculated, and the active current component for controlling the torque and the reactive current component for controlling the magnetic field are obtained. In actual control, the amplitude of the control voltage is controlled according to the speed given and the reactive current given.

[0040] The angle θ between the rotor position and the A-phase winding is obtained by detecting the rotor position, and the direction of the magnetic field generated by the motor running current that needs to be controlled is calculated, so that the magnetic field generated by the stator current is orthogonal to the rotor magnetic field. Controlling the voltage phase angle at a special point of θ has a smaller amount of calculation, that is, higher real-time system response.

[0041] Specifically, Figure 2 The meaning of the parameters in are:

[0042] n ref Speed ​​setting;

[0043] i Motor status detection current;

[0044] nMotor status detection speed;

[0045] i p Active current;

[0046] i pref Active current given;

[0047] i Qref Reactive current given;

[0048] i Q Reactive current;

[0049] Δn real-time speed difference;

[0050] SVR speed controller;

[0051] AVR power controller;

[0052] u ref Voltage given amplitude;

[0053] f frequency.

[0054] The core idea of ​​the present invention is to obtain the active current component and reactive current component of the motor by detecting and calculating the phase difference between the current and the corresponding voltage, and to control the current component of the motor torque by the characteristics of the lagging reactive current and the leading reactive current and the reactive current being equal to zero when the synchronous motor is running to realize the torque control of the motor, and to realize the vector control of the permanent magnet synchronous motor by controlling the stator voltage phase so that the direction of the synthetic magnetic field generated by the winding current is orthogonal to the direction of the rotor magnetic field of the permanent magnet synchronous motor.

[0055] The parameters that need to be controlled for permanent magnet synchronous motor vector control are: motor voltage amplitude, voltage frequency and voltage phase.

[0056] 1. The purpose of controlling the voltage amplitude is to control the torque and magnetic field of the motor. The control of torque and magnetic field can be reflected by the motor current. Specifically, the active current or torque current controls the torque, and the reactive current or magnetic field current controls the magnetic field.

[0057] 2. The frequency of the voltage controls the motor speed. The speed of the permanent magnet synchronous motor strictly corresponds to the frequency, that is, one frequency corresponds to one speed of the motor;

[0058] 3. Controlling the voltage phase is to control the direction of the magnetic field generated by the motor current. If the direction of the magnetic field generated by the motor current is perpendicular or orthogonal to the direction of the rotor magnetic field, vector control of the permanent magnet synchronous motor is achieved.

[0059] Specifically, Figure 2 The motor control system block diagram including the speed loop is given. The speed controller outputs the torque control current component i by comparing the given speed with the actual speed. Pref The control value is obtained by querying the experimental data to obtain the magnetic field control current given i Qref , respectively, with the calculated active current component i P and reactive current component i Q The comparison output is given to the current controller, and the comprehensive required i P Control value and i Q Control value output voltage amplitude control value, where i P Compare value with i Q The comparison value is calculated by the current feedback link.

[0060] Figure 3 Given the back EMF at a certain motor speed Applying different voltages Motor current Vector relationship to voltage.

[0061] Specifically, the control law of the voltage amplitude is determined according to the phase difference between the current and the voltage obtained by detection and calculation. Figure 3 It can be seen from the phasor relationship that the current phase leads the voltage phase. In actual control, increasing the voltage amplitude can reduce the phase difference between voltage and current.

[0062] When the voltage and current are in phase, the reactive current component of the motor is equal to zero, that is, at this time, all the current is torque control current, and the motor operates with a power factor equal to 1;

[0063] When the voltage is greater than the back electromotive force, it can be seen from the phasor diagram that the current phase lags behind the voltage phase. In actual control, reducing the voltage amplitude can reduce the phase difference between voltage and current.

[0064] Depend on Figure 3 The actual control can be based on the requirements of the current and voltage phase difference. The leading and lagging relationship between current and voltage is determined according to the detected phase difference, and the voltage control law is derived.

[0065] Figure 4 It can be seen that, taking the A phase of the three-phase permanent magnet synchronous motor as an example, within the electrical resolution cycle, Figure 4 The phase difference is calculated by the time difference Δt between the voltage zero-crossing point, the peak point and the current zero-crossing point and the peak point.

[0066]

[0067] Where ω=2πf, f is the voltage frequency.

[0068] When the motor is running stably, there is a strict corresponding relationship between f and the speed.

[0069] Two methods to detect and calculate the phase difference between current and voltage:

[0070] One is: Figure 4 In the equation, there are two zero crossing points and two peak points in one cycle of AC voltage, twelve identifiable points for three-phase voltage, and twelve identifiable points for three-phase current. The phase difference and current amplitude corresponding to voltage and current can be obtained when the operating frequency is certain, and the active current component and reactive current component of the current can be calculated accordingly. Figure 3 The operating characteristics of permanent magnet synchronous motors are achieved by controlling the voltage amplitude to control the phase difference and thus controlling the active current component i Pand reactive current component i Q size.

[0071] The other is: detect two-phase current, and the other phase current is calculated by the following formula:

[0072] i b =-(i a +i c ) (1)

[0073] Depend on Figure 5 Detect two-phase current A phase current i a and C phase current i c Calculate the maximum current I m and phase difference Get i P and i Q .

[0074]

[0075] when i a +2i c ≠0, find:

[0076]

[0077] We can get:

[0078] when i a ≠0,

[0079] Find:

[0080] Find:

[0081] The calculated active current component and reactive current component determine the torque and magnetic field that need to be controlled when the motor is running, which gives the amplitude of the control voltage. The specific direction of the magnetic field generated by the current is given by Figure 6 Determine the phase of the voltage.

[0082] Figure 6 A position determination diagram between the rotor magnetic field and the A-phase winding is given. For a permanent magnet synchronous motor, θ=ωt.

[0083] The direction of the stator current magnetic field is given by Figure 6 As shown in the ds axis, the detected rotor position is achieved by controlling the phase of the three-phase voltage of the motor, and the magnetic field amplitude is achieved by controlling the size of the three-phase voltage.

[0084] Specifically, the phase of the three-phase voltage that is easy to identify is determined by the special point of the rotor position and the angle θ between the A-phase winding. For example, in a quarter cycle of the AC voltage, the corresponding voltage and current phase difference plus the rotor angle θ electrical angle, that is:

[0085] When the current phase leads the voltage, take "-", otherwise take "+".

[0086] The rotor position is detected to obtain the included angle θ between the rotor position and the A-phase winding, and the direction of the magnetic field generated by the motor running current that needs to be controlled is calculated so that the magnetic field generated by the stator current is orthogonal to the rotor magnetic field.

[0087] In the time-resolvable range, controlling the voltage phase angle at a special point of θ has a smaller amount of calculation, which means higher real-time system response.

[0088] In summary, controlling the active current and reactive current of the stator current can achieve motor torque control and magnetic field control; controlling the motor voltage phase according to the rotor position and the angle θ of the A-phase winding can achieve position control of the magnetic field amplitude generated by the stator current. When the direction of the magnetic field amplitude is perpendicular to the rotor magnetic field direction, orthogonal magnetic field control is achieved, which is the vector control of the permanent magnet synchronous motor.

[0089] Although the present invention has been described according to a limited number of embodiments, it will be apparent to those skilled in the art, with the benefit of the above description, that other embodiments may be envisioned within the scope of the invention thus described. In addition, it should be noted that the language used in this specification is selected primarily for readability and teaching purposes, rather than for explaining or defining the subject matter of the present invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the present invention is illustrative, not restrictive, with respect to the scope of the present invention, which is defined by the appended claims.

Claims

1. A vector control method based on reactive current control of a permanent magnet synchronous motor, characterized in that: The following steps are involved: Step 1: Determine the active current setting and reactive current setting; Step 2: Calculate active current and reactive current from feedback current; Step 3, obtaining a given amplitude of the input voltage of the control power device; Step 4, obtaining the frequency of the input voltage of the control power device; Step 5: Obtain the angle between the rotor position and the A-phase winding by rotor position detection, determine the phase of the voltage to control the direction of the magnetic field generated by the motor running current, so that the magnetic field generated by the stator current is orthogonal to the rotor magnetic field, thereby realizing vector control of the permanent magnet synchronous motor; The specific method for determining the active current and reactive current given in step 1 is to determine the active current given by the speed controller according to the real-time speed difference; The reactive current is obtained by querying the experimental data of the speed setting and the real-time motor speed. The reactive current is determined according to the speed setting to determine the reactive current setting required for the control process. Step 5: The specific method for determining the voltage phase of the field-oriented control is to obtain the rotor magnetic field position from the rotor position detection, and it is known that the position of the stator current magnetic field needs to be controlled to achieve orthogonal control of the stator magnetic field and the rotor magnetic field, that is, to control the three-phase voltage phase to achieve orthogonal control of the magnetic field generated by the permanent magnet synchronous motor current and the rotor magnetic field.

2. The method according to claim 1, characterized in that The specific method for obtaining the given amplitude of the input voltage of the control power device described in step three is to calculate the active current and reactive current from the feedback current, compare them with the given active current and the given reactive current respectively, and input them to the current controller to obtain the given amplitude of the input voltage of the control power device.

3. The method according to claim 1, characterized in that The specific method for obtaining the frequency of the input voltage of the control power device described in step 4 is to determine the frequency of the input voltage given by the control power device according to the speed given.

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