A high-precision current compensation system and compensation method for a permanent magnet synchronous motor

Abstract

The present invention provides a high-precision current compensation system for a permanent magnet synchronous motor. This system generates an output voltage through a current controller, based on current reference and feedback. This voltage is applied to the motor through an SVPWM algorithm and an inverter, forming a closed-loop control system. This closed-loop control system primarily uses an algorithm to calculate the feedback current based on the changing trend of the speed reference value. The algorithm also uses the ratio of the speed feedback to the rated value in the load torque as an adjustment factor, thereby increasing the speed relevance of torque compensation. Specifically, the compensation algorithm provides precise compensation based on the reference current loop, improving control performance from the perspective of the reference current signal iq*.

Description

Technical Field

[0001] The present invention relates to the technical field of permanent magnet synchronous motors, and in particular to a high-precision current compensation system and compensation method for permanent magnet synchronous motors. Background Art

[0002] A permanent magnet synchronous motor primarily consists of a rotor, end caps, and stator. The stator structure of a permanent magnet synchronous motor is very similar to that of a conventional induction motor. The main difference between the rotor structure and that of an asynchronous motor is the placement of high-quality permanent magnet poles on the rotor. Depending on the placement of the permanent magnets on the rotor, permanent magnet synchronous motors are typically categorized as either surface-mount or internal-mounted rotors.

[0003] When permanent magnet synchronous motors are used in CNC machine tools and industrial robots, very precise control of motion control accuracy and speed is required. The most widely used application is position control.

[0004] In the prior art, the invention patent with patent publication number CN102075127B discloses a permanent magnet synchronous motor servo drive device and a position control method thereof. In addition to adopting a general controller structure, it also proposes to use correction information of speed feedback to effectively reduce position following deviation. The position control method of the permanent magnet synchronous motor servo drive device proposed in the present invention compensates for disturbances by designing a torque observer that utilizes speed model deviation.

[0005] There are many control algorithms for permanent magnet synchronous motors, among which the more mature ones are proportional-integral control (PI) and direct torque control. PI control offers good steady-state control performance, but poor dynamic performance. Fast response comes at the expense of speed. Direct torque control offers fast response and excellent parameter tolerance, but is essentially a hysteresis control. Even at rest, current fluctuates continuously. With the use of new electromagnetic materials and the modernization of power devices, it is possible to complete more complex algorithms within a single current cycle, including the use of new high-precision permanent magnet synchronous motor control algorithms. In summary, traditional control lacks current compensation, which impacts the dynamic performance of speed. Existing compensation methods cannot comprehensively consider the impact of speed on current performance and its requirements. Summary of the Invention

[0006] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a high-precision current compensation system and compensation method for a permanent magnet synchronous motor.

[0007] The present invention provides the following technical solutions:

[0008] A high-precision current compensation system for a permanent magnet synchronous motor, comprising a speed controller, a current controller, an SVPWM vector modulation module, an inverter, a motor, a current sensor, and a position sensor;

[0009] The speed controller is used to compare the speed reference point with the speed feedback to obtain a given current value;

[0010] The current controller includes a current loop structure for receiving a given current and current feedback to generate an output voltage. The given current is provided with precise compensation for the given current signal, thereby improving the control performance of the given current signal.

[0011] The SVPWM modulation module is used for space vector pulse width modulation, according to the voltage index under the input αβ axis Calculate and obtain PWM pulse signal;

[0012] The inverter is used to control the switch according to the PWM pulse signal to generate a voltage to control the motor;

[0013] The current sensor is used to output the i a and i b The coordinate transformation is calculated and fed back to the current loop of the current controller;

[0014] The position sensor is used to collect the electrical angle of the motor.

[0015] Preferably, the compensation includes the controller output of the speed loop, the compensation current output of the feedback current and the compensation circuit output of the load torque, and the current given signal expression is:

[0016] i q * =i q1 * +i q2 * +i q3 * (1)

[0017] In formula 1, i q * is the current given signal, i q1 * is the given current output by the speed controller to the current loop, i q2 * is the feedback compensation current, i q3 * is the compensation current of the load torque.

[0018] Preferably, the compensation current output of the feedback current is set according to the change trend of the speed given value. When the speed given value is in an upward trend and the upward trend is a large range, the compensation is a large positive value; when the speed given value is in a downward trend and the downward trend is a large range, the compensation is a large negative value; when the speed given value is close to the extreme value, the compensation value decreases; the feedback current compensation signal expression is:

[0019]

[0020] in is the given speed, It is the maximum value of the current change trend, K1 value range is 0.01-0.1, and Δt is the time interval of change.

[0021] Preferably, the load torque compensation is based on the output torque of the motor and the output torque of the torque observation, and then the load torque of the motor is calculated and compensated, and the expression is:

[0022]

[0023] in is the rated speed of the motor actually running, ω γ is the actual feedback speed, is the observed torque value, It is the torque current coefficient, and the value range of K2 is 0.1-0.6.

[0024] Preferably, the rated speed of the motor actually running and the actual feedback speed form a relative speed ratio, forming an adjustment coefficient of the torque compensation, thereby increasing the speed correlation of the torque compensation.

[0025] Preferably, the observed value of the torque is calculated by designing a torque observer based on the reference model of Formula 4 and the adjustable model of Formula 5. The specific formula is as follows:

[0026] Jω γ s=T e -T L -Bω γ (4)

[0027]

[0028] Where J represents the moment of inertia, ω γ is the actual feedback speed, s represents the differential operator, T e Represents electromagnetic torque, T L is the load torque, B is the sliding friction coefficient, e is the deviation of the velocity model, To adjust the observation speed of the model, is the observed value of the load torque;

[0029] The deviation of the velocity model is:

[0030]

[0031] Subtracting Equation 4 from Equation 5 yields the state error:

[0032]

[0033] Preferably, is a positive real transfer function, so the observation law of load torque is obtained, and its expression is:

[0034]

[0035] where K L1 K is the integral coefficient of torque observation, LP is the proportional coefficient of torque observation.

[0036] A preferred high-precision current compensation method for a permanent magnet synchronous motor is characterized by the following specific steps:

[0037] S1, detects the rotor position θ of the motor, and the output voltage generated by the current controller is applied multiple times with non-zero vectors and zero vectors in one cycle through the SVPWM algorithm, so that the voltage space vector rotates close to the circular trajectory, and the i in the output three-phase current is a and i b ;

[0038] S2. The current sensor calculates the feedback current id and iq by coordinate transformation of ia and ib given by the feedback current;

[0039] S3, observe the load torque according to the motor angular velocity and current through the position sensor to obtain the load torque observation value

[0040] S4, the position sensor collects the actual angular velocity of the motor and receives the feedback speed at the same time. The two are used as the compensation current of the load torque through differential operation. And give it to the current controller;

[0041] S5. According to the change trend of the speed given value of the motor's running angular velocity, the compensation setting calculation of iq is performed to obtain the feedback compensation current i q2 * ;

[0042] S6, speed controller speed loop output current i q1 * , in conjunction with the feedback compensation current i q2 *and load torque compensation current The current given signal i is calculated q * and the current given signal i q * is given to the current controller, and the d-axis torque current given value i d * is given to the current controller, but the setting for the d-axis current is i d * =0;

[0043] S7, the current controller generates the output voltage according to the given current and current feedback and And the voltage and As the input of the SVPWM modulation module.

[0044] The beneficial effects of the present invention are:

[0045] By making a compensation algorithm for the current given signal, one part of it sets the compensation for the current given value according to the changing trend of the speed given value, that is, the current compensation amount is calculated by the changing trend of the difference between the speed extreme value and the speed given value at different times; the other part is for the relative ratio between the actual operating speed and the speed received feedback, combined with the observed torque value and the torque current coefficient calculation, to obtain the conversion of torque to current dimension, give compensation to the load torque, and thus obtain a better compensation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0047] Figure 1 It is a schematic structural diagram of the current compensation system of the present invention;

[0048] Figure 2 It is a speed given value variation trend diagram of the present invention. DETAILED DESCRIPTION

[0049] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0050] like Figure 1 As shown, a high-precision current compensation system for a permanent magnet synchronous motor includes a speed controller, a current controller, an SVPWM vector modulation module, an inverter, a motor, a current sensor, and a position sensor.

[0051] The speed controller is used to compare the speed reference point with the speed feedback to obtain a given value of the current.

[0052] The current controller includes a current loop structure for receiving a given current and current feedback to generate an output voltage. The given current is provided with precise compensation for the given current signal, thereby improving the control performance of the given current signal. The compensation includes the controller output of the speed loop, the compensation current output of the feedback current, and the compensation circuit output of the load torque. The expression of the given current signal is:

[0053] i q * =i q1 * +i q2 * +i q3 * (1)

[0054] In formula 1, i q * is the current given signal, i q1 * is the given current output by the speed controller to the current loop, i q2 * is the feedback compensation current, i q3 * is the compensation current of the load torque.

[0055] The SVPWM modulation module is used for space vector pulse width modulation, according to the voltage index under the input αβ axis Calculate and obtain PWM pulse signal;

[0056] The inverter is used to control the switch according to the PWM pulse signal to generate a voltage to control the motor;

[0057] The current sensor is used to calculate the coordinate transformation of ia and ib output by the SVPWM modulation module and feed back the calculated values to the current loop of the current controller.

[0058] The position sensor is used to collect the electrical angle of the motor.

[0059] The speed controller is connected to the current controller, the current controller is connected to the SVPWM modulation module, the SVPWM modulation module is connected to the inverter, the inverter is connected to the motor, the motor is connected to the position sensor, and the position sensor is connected to the speed controller, wherein the inverter and the position sensor are also connected to the current controller respectively.

[0060] like Figure 2As shown in the figure, point A is in the range of a large rising slope, and the difference in speed values at both ends of a certain time Δt is large, so the feedback compensation is positive compensation and the current i q2 * The value is large; on the contrary, in the range of large descending slope, the feedback compensation is negative compensation and the current i q2 * The value is large.

[0061] As can be seen from the figure, when the rise or fall approaches the extreme value, the compensation value decreases. For C and D, the values of C and D are less than A and greater than B. Since the speed value is the given value, the change trend of the speed given value is very clear. The change trend is obvious, and the compensation expression set according to the speed given value is:

[0062]

[0063] in is the given speed, It is the maximum value of the current change trend, K1 value range is 0.01-0.1, and Δt is the time interval of change.

[0064] The load torque compensation is based on the output torque of the motor and the output torque of the torque observer. The load torque of the motor is calculated and compensated. The expression is:

[0065]

[0066] in is the rated speed of the motor actually running, ω γ is the actual feedback speed, is the observed torque value, It is the torque current coefficient, and the value range of K2 is 0.1-0.6.

[0067] The observed value of the torque is calculated by designing a torque observer based on the reference model of Equation 4 and the adjustable model of Equation 5. The specific formula is as follows:

[0068] Jω γ s=T e -T L -Bω γ (4)

[0069]

[0070] Where J represents the moment of inertia, ω γ is the actual feedback speed, s represents the differential operator, T e Represents electromagnetic torque, T L is the load torque, B is the sliding friction coefficient, e is the deviation of the velocity model, To adjust the observation speed of the model, is the observed value of the load torque.

[0071] The deviation of the velocity model is:

[0072]

[0073] Subtracting Equation 4 from Equation 5 yields the state error:

[0074]

[0075] is a positive real transfer function, so the observation law of load torque is obtained, and its expression is:

[0076]

[0077] where K L1 K is the integral coefficient of torque observation, LP is the proportional coefficient of torque observation.

[0078] The specific steps of the current compensation method are as follows:

[0079] S1, detects the rotor position θ of the motor, and the output voltage generated by the current controller is applied multiple times with non-zero vectors and zero vectors in one cycle through the SVPWM algorithm, so that the voltage space vector rotates close to the circular trajectory, and the i in the output three-phase current is a and i b ;

[0080] S2. The current sensor calculates the feedback current id and iq by coordinate transformation of ia and ib given by the feedback current;

[0081] S3, observe the load torque according to the motor angular velocity and current through the position sensor to obtain the load torque observation value

[0082] S4, the position sensor collects the actual angular velocity of the motor and receives the feedback speed at the same time. The two are used as the compensation current of the load torque through differential operation. And give it to the current controller;

[0083] S5. According to the change trend of the speed given value of the motor's running angular velocity, the compensation setting calculation of iq is performed to obtain the feedback compensation current i q2 * ;

[0084] S6, speed controller speed loop output current i q1 * , in conjunction with the feedback compensation current i q2* and load torque compensation current The current given signal i is calculated q * and the current given signal i q * is given to the current controller, and the d-axis torque current given value i d * is given to the current controller, but the setting for the d-axis current is i d * =0;

[0085] S7, the current controller generates the output voltage according to the given current and current feedback and And the voltage and As the input of the SVPWM modulation module.

[0086] The prior art, patent publication number CN102075127B, describes a permanent magnet synchronous motor servo drive device and position control method thereof. This method uses PI control as a compensation method, primarily focusing on torque observation and compensation current output. This prior art uses the ratio of the motor's actual speed to its given speed as the torque compensation coefficient, ignoring external factors such as resistance to the motor's rotation during actual operation.

[0087] However, the present invention adopts the ratio of the real-time feedback speed of the motor and the rated speed of the motor as the torque compensation adjustment coefficient, which is closer to the actual operation situation, and effectively takes into account the influence of the outside world on the motor while compensating for it when executing the compensation algorithm, making the compensation more accurate.

[0088] On this basis, the current compensation for the speed setting is also compensated in real time with the changing speed. Therefore, the combination of the above two points makes the compensation for the current setting signal more accurate than the existing technology.

[0089] In a specific real-time operation process, when the motor is set to run for 100ms so that the operating speed reaches 2500r / min, the current is controlled by PI control and the compensation algorithm adopted by the present invention respectively, and the results are compared. Compared with PI control, the above-mentioned compensation algorithm adopted by the present invention is about 10ms ahead in time, and the bandwidth of the current on the d-axis and q-axis is increased by 15%.

[0090] In addition, when the motor speed is stabilized at 1500r / min, an additional load torque of 6Nm is added to the system through the powder brake. Under this condition, the PI control restores the rotation to a stable state after 155ms, while the compensation algorithm mentioned in the present invention takes 113ms to restore the steady state. In comparison, the interference resistance of the compensation algorithm mentioned in the present invention is improved by about 25%.

[0091] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A high-precision current compensation system for a permanent magnet synchronous motor, characterized in that: Including speed controller, current controller, SVPWM vector modulation module, inverter, motor, current sensor, position sensor; The speed controller is used to compare the speed reference point with the speed feedback to obtain a given current value; The current controller includes a current loop structure for receiving a given current and current feedback to generate an output voltage. The given current is provided with precise compensation for the given current signal, thereby improving the control performance of the given current signal. The SVPWM modulation module is used for space vector pulse width modulation, according to the voltage index under the input αβ axis Calculate and obtain PWM pulse signal; The inverter is used to control the switch according to the PWM pulse signal to generate a voltage to control the motor; The current sensor is used to output the i a and i b The coordinate transformation is calculated and fed back to the current loop of the current controller; The position sensor is used to collect the electrical angle of the motor; The compensation includes the controller output of the speed loop, the compensation current output of the feedback current and the compensation circuit output of the load torque. The current given signal expression is: i q * =i q1 * +i q2 * +i q3 * (1) In formula 1, i q * is the current given signal, i q1 * is the given current output by the speed controller to the current loop, i q2 * is the feedback compensation current, i q3 * is the compensation current of the load torque; The load torque compensation is based on the output torque of the motor and the output torque of the torque observation, and then the load torque of the motor is calculated and compensated. The expression is: in is the rated speed of the motor actually running, ω γ is the actual feedback speed, is the observed torque value, is the torque current coefficient, K2 has a value range of 0.1-0.6; the observed value of the torque is calculated by designing a torque observer based on the reference model of formula 4 and the adjustable model of formula 5. The specific formula is as follows: Jω γ s=T e -T L -Bω γ (4) Where J represents the moment of inertia, ω γ is the actual feedback speed, s represents the differential operator, T e Represents electromagnetic torque, T L is the load torque, B is the sliding friction coefficient, e is the deviation of the velocity model, To adjust the observation speed of the model, is the observed value of the load torque; The deviation of the velocity model is: Subtracting Equation 4 from Equation 5 yields the state error:

2. A high-precision current compensation system for a permanent magnet synchronous motor according to claim 1, characterized in that: The compensation current output of the feedback current is set according to the change trend of the speed given value. When the speed given value is in an upward trend and the upward trend is a large range, the compensation is a large positive value; When the speed given value is in a downward trend and the downward trend is large, the compensation is a large negative value; when the speed given value is close to the extreme value, the compensation value decreases; the feedback current compensation signal expression is: in is the given speed, It is the maximum value of the current change trend, K1 value range is 0.01-0.1, and Δt is the time interval of change.

3. The high-precision current compensation system for a permanent magnet synchronous motor according to claim 1, characterized in that: The rated speed of the motor actually running and the actual feedback speed form a relative speed ratio, forming an adjustment coefficient of the torque compensation, thereby increasing the speed correlation of the torque compensation.

4. The high-precision current compensation system for a permanent magnet synchronous motor according to claim 1, characterized in that: is a positive real transfer function, so the observation law of load torque is obtained, and its expression is: where K L1 K is the integral coefficient of torque observation, LP is the proportional coefficient of torque observation.

5. A compensation method for a high-precision current compensation system of a permanent magnet synchronous motor according to claim 1, characterized in that: The specific steps are as follows: S1, detects the rotor position θ of the motor, and the output voltage generated by the current controller is applied multiple times with non-zero vectors and zero vectors in one cycle through the SVPWM algorithm, so that the voltage space vector rotates close to the circular trajectory, and the i in the output three-phase current is a and i b ; S2. The current sensor calculates the feedback current id and iq by coordinate transformation of ia and ib given by the feedback current; S3, observe the load torque according to the motor angular velocity and current through the position sensor to obtain the load torque observation value S4, the position sensor collects the actual angular velocity of the motor and receives the feedback speed at the same time. The two are used as the compensation current of the load torque through differential operation. And give it to the current controller; S5. According to the change trend of the speed given value of the motor's running angular velocity, the compensation setting calculation of iq is performed to obtain the feedback compensation current i q2 * ; S6, speed controller speed loop output current i q1 * , in conjunction with the feedback compensation current i q2 * and load torque compensation current The current given signal i is calculated q * and the current given signal i q * is given to the current controller, and the d-axis torque current given value i d * is given to the current controller, but the setting for the d-axis current is i d * =0; S7, the current controller generates the output voltage according to the given current and current feedback and And the voltage and As the input of the SVPWM modulation module.

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