Control method and control system for rotor position angle of permanent magnet synchronous motor

Abstract

The present invention discloses a control method and control method for the rotor position angle of a permanent magnet synchronous motor, wherein the control method is to establish a sliding mode model to obtain a position angle estimation equation. By collecting the stator current signal of the permanent magnet synchronous motor, the rotor position can be effectively calculated to achieve sensorless setting, and after collecting the current and voltage, the protection circuit is input to achieve additional protection on the hardware, wherein the protection circuit 10 is electrically connected to the controller or the protection signal is directly input into the PWM drive module 9 to control the enabling of the PWM signal. Once a fault signal appears, the PWM signal is directly blocked to achieve the hardware protection function, and the direct drive method is adopted to reduce the possibility of interference interruption caused by the control board fault.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor control, and in particular relates to a method and a control system for controlling the rotor position angle of a permanent magnet synchronous motor. Background Art

[0002] AC permanent magnet synchronous motors have been widely used in many fields such as industrial control and aerospace due to their high energy utilization and excellent mechanical properties. Permanent magnet synchronous motors usually use vector control, which requires constant detection of the rotor position angle for calculation and control. The rotor position angle is generally obtained using a mechanical position sensor, but the presence of mechanical sensors increases the size and cost of the motor, reduces the reliability of the system, and also limits its promotion and application in some special occasions.

[0003] Moreover, the existing logic control mainly relies on software for protection, and when problems occur in the software, it is easy to cause disasters.

[0004] The sliding mode observer is a software algorithm that uses electrical information such as motor stator parameters, current and voltage to observe the motor back EMF and obtain the motor rotor position angle through the back EMF. The algorithm has the advantages of strong robustness, simple control, and easy engineering implementation. Due to the existence of chattering in the sliding mode observer, the observation results need to be low-pass filtered to obtain the back EMF. However, while eliminating the chattering, the observed signal will also produce a phase lag, affecting the detection accuracy. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a control system for the rotor position angle of a permanent magnet synchronous motor.

[0006] Another object of the present invention is to provide a control method for a control system of a permanent magnet synchronous motor rotor position angle.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for controlling the rotor position angle of a permanent magnet synchronous motor comprises the following steps:

[0009] Establish a sliding mode model and obtain the position angle estimation equation

[0010]

[0011]

[0012] In the formula is the estimated back EMF of the motor α and β axes;

[0013] z a ,z βis the equivalent control function of the sliding mode of α and β axes;

[0014] is the estimated motor rotor position angle;

[0015] ω c is the cutoff frequency of the low-pass filter.

[0016] In the above technical solution, the step of compensating the position angle for the offset angle is also included, and the offset angle calculation method is to use the speed reference value ω * Instead of the actual speed ω, the cutoff frequency ω c Select the speed reference value ω * N times.

[0017] In the above technical solution, if the speed reference value ω * The current speed ω is much larger than the current speed ω, and the segmentation strategy is adopted to gradually make the current speed ω close to the speed reference value ω. * ; Keep the speed reference value and the current speed value at a certain difference until it is equal to the final reference value ω * Consistent.

[0018] In the above technical solution, when the permanent magnet synchronous motor adopts the sensorless control method, when the motor speed reaches a certain speed ω q When the control mode is switched, it is necessary to switch to the speed current dual closed loop mode. Before the control mode is switched, the filter cutoff frequency is fixed to the switching speed ω q N times.

[0019] In the above technical solution, the offset angle compensation is performed when the rotation speed reaches more than 20% of the rated rotation speed.

[0020] In the above technical solution, the voltage equation of PMSM in the α-β coordinate system is expressed as:

[0021]

[0022] Where i s is the stator current, i s =(i α ,i β ) T ;

[0023] u s is the stator voltage, u s =(u α ,u β ) T ;

[0024] E s is the motor back electromotive force, E s =(E α ,E β )T ;

[0025] A is the coefficient matrix, A=(-R s / L s )I;

[0026] B is the coefficient matrix, B = (1 / L s )I;

[0027] I is the identity matrix;

[0028] R s is the stator resistance;

[0029] L s is the stator inductance;

[0030] Since the electrical time constant of PMSM is very small, the back EMF is regarded as the disturbance of the system, and the sliding mode observer equation is as follows:

[0031]

[0032] In the formula is the estimated value of stator current,

[0033] K is K = kI, where k is the sliding mode gain;

[0034] Subtracting equations (1) and (2) will yield the motor current observation error equation:

[0035]

[0036] In the formula is the sliding plane;

[0037] If the condition s is met T .s<0, the observer will enter the sliding mode state, at this time Define equivalent controls:

[0038]

[0039] To ensure the convergence of equation (4), the sliding mode gain k must satisfy k>max(|e α |,|e β |);

[0040] Since the Z variable contains back electromotive force information, the estimated value of the position angle can be obtained by filtering it and then performing an inverse tangent transformation.

[0041] In the above technical scheme, it includes a rectifier bridge, an inverter bridge, a PWM drive module, a control board, a DC voltage detection circuit whose output is electrically connected to the control board and is used to detect the output voltage of the rectifier bridge, a current detection circuit whose output is electrically connected to the control board and is used to detect the stator current of the permanent magnet synchronous motor, and a protection circuit connected to the output of the DC voltage detection circuit and the output of the current detection circuit, and the output of the protection circuit is respectively connected to the control board and the PWM drive module.

[0042] In the above technical solution, the positive output of the rectifier bridge is connected in series with a charging resistor and then connected to the input end of the three-phase inverter bridge. A DC contactor is connected in parallel to the charging resistor, and the DC contactor is driven to turn on or off by the control board.

[0043] In the above technical solution, the voltage sampling module is used to collect the output voltage of the rectifier, which includes a first operational amplifier with positive and negative input terminals and a voltage collection terminal, and the output of the first operational amplifier is connected to the signal processing module after passing through a signal adjustment unit. At the same time, the output of the first operational amplifier is connected to the input terminal through a resistor R4; the current sampling module is used to collect the output current of the rectifier, which includes a mutual inductor arranged at the negative output, a second operational amplifier whose positive and negative electrodes correspond to the two ends of the mutual inductor and are electrically connected accordingly, and at the same time, the output of the second operational amplifier is connected to the input terminal through a resistor R8, and the output of the second operational amplifier is connected to the positive electrode of the third operational amplifier after passing through a resistor R10, and the output of the third operational amplifier is connected to the negative electrode, and the output of the third operational amplifier is connected to the signal processing module after passing through a signal adjustment unit, and the signal adjustment unit includes two diodes whose positive and negative electrodes are connected in sequence, the negative electrode of the diode is connected to a positive voltage, and the positive electrode is grounded, and the output of the first operational amplifier or the third operational amplifier is electrically connected between the two diodes.

[0044] In the above technical solution, the protection signal circuit includes a comparator whose positive pole is respectively connected to the output of the first operational amplifier or the third operational amplifier, whose negative pole is respectively connected to the reference voltage and the reference current, an AND-OR gate whose two input ends are connected to the outputs of the two comparators, and an inverter connected to the output of the AND-OR gate, and the output end of the inverter is connected to the PWM drive module.

[0045] In the above technical solution, the main protection circuit includes a transistor with a base and an output end of the inverter, the emitter of the transistor is grounded, the relay electrode is connected in series with the corresponding coil and connected to a positive power supply, and a diode is connected in parallel with the coil and the negative electrode is connected to the positive power supply.

[0046] The advantages and beneficial effects of the present invention are:

[0047] According to the improved sliding mode observer method described above, the present invention uses the DSP28335 control board to perform software programming, implements the above control algorithm, and conducts motor tests. The test results show that the improved sliding mode observer algorithm effectively improves the detection accuracy of the rotor position angle, and the power factor of the inverter is also further improved.

[0048] By collecting the stator current signal of the permanent magnet synchronous motor, the rotor position can be effectively calculated to achieve sensorless setting. Moreover, after collecting the current and voltage, the protection circuit is input to achieve additional protection in hardware. Among them, the protection circuit 10 is electrically connected to the controller or the protection signal is directly input into the PWM drive module 9 to control the enablement of the PWM signal. Once a fault signal occurs, the PWM signal is directly blocked to achieve hardware protection function. The direct drive method is adopted to reduce the possibility of interference interruption caused by control board faults. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is the structure diagram of the permanent magnet synchronous motor control system;

[0050] Figure 2 This is the internal structure diagram of the diode rectifier bridge;

[0051] Figure 3 This is the internal structure diagram of the three-phase inverter bridge;

[0052] Figure 4 This is the circuit diagram for DC voltage collection;

[0053] Figure 5 This is the current acquisition circuit diagram;

[0054] Figure 6 To protect the circuit diagram;

[0055] Figure 7 Flowchart of improved sliding mode observer algorithm.

[0056] in:

[0057] 1. Three-phase AC power supply 2. Diode rectifier

[0058] 3. Three-phase inverter bridge 4. Permanent magnet synchronous motor

[0059] 5. Touch screen 6. DSP control board

[0060] 7. DC voltage detection circuit 8. Current detection circuit

[0061] 9. PWM drive module 10. Protection circuit

[0062] 11. Charging resistor 12. DC contactor

[0063] 13. Bus capacitor 14. First operational amplifier

[0064] 15. Second operational amplifier 16. Third operational amplifier

[0065] 17. Comparator 18. Comparator

[0066] 19. OR gate 20. Inverter

[0067] For ordinary technicians in this field, other relevant drawings can be obtained based on the above drawings without any creative work. DETAILED DESCRIPTION

[0068] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with specific embodiments.

[0069] Embodiment 1

[0070] A control system for the rotor position angle of a permanent magnet synchronous motor comprises a rectifier bridge 2 whose input end is connected to the UVW three-phase of a three-phase alternating current 1, and a three-phase inverter bridge 3 whose output end ABC three-phase is connected to the permanent magnet synchronous motor 4, and a PWM drive module 9 and a DSP control board 9, and a DC voltage detection circuit 7 for detecting the output voltage of the rectifier bridge, respectively electrically connected to the control board, and a current detection circuit 8 for detecting the stator current of the permanent magnet synchronous motor, and a protection circuit 10, wherein the input of the protection circuit 10 is connected to the output of the DC voltage detection circuit and the output of the current detection circuit, and the output of the protection circuit is respectively connected to the control board and the PWM drive module.

[0071] By collecting the stator current signal of the permanent magnet synchronous motor, the rotor position can be effectively calculated to achieve sensorless setting. Moreover, after collecting the current and voltage, the protection circuit is input to achieve additional protection in hardware. Among them, the protection circuit 10 is electrically connected to the controller or the protection signal is directly input into the PWM drive module 9 to control the enablement of the PWM signal. Once a fault signal occurs, the PWM signal is directly blocked to achieve hardware protection function. The direct drive method is adopted to reduce the possibility of interference interruption caused by control board faults.

[0072] The positive output of the rectifier bridge is connected in series with the charging resistor 11 and then connected to the input end of the three-phase inverter bridge. The DC contactor 12 is turned on or off by the output drive of the control board 6. The charging resistor of the present invention is already connected in series in the charging circuit when the control system is powered on. Only when the capacitor voltage reaches the set value and charging is completed, the controller, i.e., the control board, will send a signal to close the DC contactor 12 and short-circuit the charging resistor. The charging resistor is an indispensable part of the charging circuit of the control system to prevent overcurrent from damaging system components during charging, and is particularly suitable for permanent magnet synchronous motor drive with large rotational inertia.

[0073] Among them, the PWM drive module uses the SKHI22AH4R module of Semikron, which integrates the drive and protection circuit functions, has a simple peripheral circuit, does not require optocoupler or transformer isolation, and can directly connect the DSP's PWM signal to the power module, making it easy to use.

[0074] Figure 2 : is the internal structure diagram of the diode rectifier bridge, and the specific connection method is as follows: the diode rectifier bridge 2 is composed of six diodes D1-D6, the diodes of the upper bridge arm are D1, D3, D5, and the diodes of the lower bridge arm are D2, D4, D6, wherein the positive electrode of the diode D1 is connected to the negative electrode of the diode D2 to form a bridge arm, the positive electrode of the diode D3 is connected to the negative electrode of the diode D4 to form a bridge arm, and the positive electrode of the diode D5 is connected to the negative electrode of the diode D6 to form a bridge arm.

[0075] Figure 3 It is the internal structure diagram of the three-phase inverter bridge. The specific connection method is as follows: the three-phase inverter bridge 3 is composed of six thyristors Q1-Q6, the upper bridge arm is composed of thyristors Q1, Q3, and Q5, and the lower bridge arm is composed of thyristors Q2, Q4, and Q6, wherein the emitter of thyristor Q1 is connected to the collector of thyristor Q2 to form a bridge arm, the emitter of thyristor Q3 is connected to the collector of thyristor Q4 to form a bridge arm, and the emitter of thyristor Q5 is connected to the collector of thyristor Q6 to form a bridge arm.

[0076] Specifically, the diode rectifier bridge 2 in the main circuit is used to convert AC power into DC power, the charging resistor 11 and the DC contactor 12 prevent current overcurrent during charging, the bus capacitor 13 is used to stabilize the DC voltage, and the three-phase inverter bridge 3 is used to realize the vector control of the permanent magnet synchronous motor 4. The 4th end of the diode rectifier bridge 2, that is, the positive output end, is connected to the charging resistor 11 and one end of the DC contactor 12, and the 5th end of the diode rectifier bridge 2, that is, the negative output end, is connected to the negative pole of the bus capacitor 13 and the 2nd end of the three-phase inverter bridge 3. The other end of the charging resistor 11 and the DC contactor 12 is connected to the positive pole of the bus capacitor 13 and the 1st end of the three-phase inverter bridge 3, and the 3rd, 4th, and 5th ends of the three-phase inverter bridge 3 are connected to the A, B, and C phases of the permanent magnet synchronous motor 4.

[0077] A control board, such as a DSP control board 6, is electrically connected to realize corresponding electrical connections. The DSP control board 6 is the control core of the system, and is used for collecting voltage and current signals, outputting PWM signals (pulse width modulation), realizing motor control algorithms and protection functions, and realizing human-machine communication and other functions.

[0078] It also includes a touch screen 5 that communicates with the DSP controller. The touch screen 5 is mainly used to realize the display and adjustment functions of the permanent magnet synchronous motor parameters. The touch screen 5 uses a 7-inch touch screen from Beijing Kunlun Tongtai Company, model TPC7062K. The touch screen is powered by a 24V DC power supply and communicates with the DSP using RS232. It integrates liquid crystal display, touch panel, control and data storage units. The software is divided into operating environment screen configuration software and data communication protocol, both of which are written using MCGS embedded version configuration software and its script driver development tool.

[0079] Among them, the protection circuit 10 is electrically connected to the controller or inputs the protection signal into the PWM drive module 9 to control the enablement of the PWM signal. Once a fault signal occurs, the PWM signal is directly blocked to realize the hardware protection function. A direct drive method is adopted to reduce the possibility of interference interruption caused by control board faults.

[0080] Embodiment 2

[0081] The DC voltage detection circuit 7 of the present invention is used to collect the output voltage of the rectifier, and includes a first operational amplifier 14 with positive and negative input terminals and a voltage collection terminal, and the output of the first operational amplifier 14 is connected to the signal processing module after passing through a resistor R5 and a signal adjustment unit, and at the same time, the output of the first operational amplifier is connected to the input terminal through a resistor R4, and a capacitor C2 is connected in parallel to the resistor R4. At the same time, the positive input terminal of the first operational amplifier is grounded after passing through a capacitor C1, and a resistor R3 is also provided in parallel with the capacitor C1.

[0082] The current detection circuit is used to collect the stator current of the motor, which includes a sensor arranged on the stator, a second operational amplifier 15 whose positive and negative electrodes correspond to the two ends of the sensor and are electrically connected, and at the same time, the output of the second operational amplifier is connected to the input end through a resistor R8, and the resistor R8 is connected in parallel with a capacitor C5, the output of the second operational amplifier is connected to the positive electrode of the third operational amplifier 16 after a resistor R10, the positive electrode of the third operational amplifier is grounded after a resistor R11, the output of the third operational amplifier is connected to the negative electrode, and the output of the third operational amplifier is connected to the signal processing module after a signal adjustment unit. Wherein, the signal adjustment unit includes two diodes D8 and D7, or D9 and D10, whose positive and negative electrodes are connected in sequence, the negative electrode of the diode D8 or D9 is connected to a positive voltage, the positive electrode of the diode D9 or D10 is grounded, the output of the first operational amplifier or the third operational amplifier is electrically connected to the two diodes and output to the control board, and the diode D7 or D10 on the ground side is also connected in parallel with a capacitor or C3 or C6.

[0083] The protection circuit 10 includes two comparators 17 and 18 whose positive electrodes are the outputs of the first operational amplifier or the third operational amplifier respectively, the negative electrodes of the two comparators 17 and 18 are respectively connected to the reference voltage and the reference current, an AND-OR gate 19 whose two input ends are connected to the outputs of the two comparators, and an inverter 20 connected to the output of the AND-OR gate, the output end of the inverter is connected to the PWM drive module, and an embedded resistor R12 is provided at the input end of the PWM drive module.

[0084] In order to realize the action of the DC contactor, its coil can be directly driven by the control board. The coil driving circuit output by the control board includes a transistor whose base is connected to the output end through a resistor, the emitter of the transistor is grounded, the collector is connected in series with the corresponding coil and then connected to the positive power supply, and a diode connected in parallel with the coil and the negative electrode is connected to the positive power supply.

[0085] Specifically, the resistor R1 is connected to the feedback voltage VolInput1 port, and the other end is connected to the resistor R4, the capacitor C2 and the negative end of the operational amplifier 14, and the other ends of the resistor R4 and the capacitor C2 are connected to the output end of the operational amplifier 14. The resistor R2 is connected to the feedback voltage VolInput2 port, and the other end is connected to the resistor R3, the capacitor C1 and the positive end of the operational amplifier 14, and the other ends of the resistor R3 and the capacitor C1 are connected to AGND. One end of the resistor R5 is connected to the output end of the operational amplifier 14, and the other end is connected to the capacitor C3, the negative electrode of the diode D7, and the positive electrode of the diode D8. The other end of the capacitor C3 and the positive electrode of the diode D7 are connected to AGND, the negative electrode of the diode D8 is connected to 3.3V, and the voltage output signal is connected to the positive electrode of the diode D8 and the negative electrode of the diode D7.

[0086] Figure 5 This is the current detection circuit diagram, the specific connection relationship is as follows:

[0087] Resistor R6 is connected to the feedback current CurInput1 port, and the other end is connected to resistor R8, capacitor C5 and the negative end of operational amplifier 15, and the other ends of resistor R8 and capacitor C5 are connected to the output end of operational amplifier 15. Resistor R7 is connected to the feedback current CurInput2 port, and the other end is connected to resistor R9, capacitor C4 and the positive end of operational amplifier 15, and the other ends of resistor R9 and capacitor C4 are connected to AGND. One end of resistor R10 is connected to the output end of operational amplifier 15, and the other end is connected to resistor R11 and the positive end of operational amplifier 16. One end of resistor R11 is connected to 3.3V, and the other end is connected to the positive end of operational amplifier 16. The negative end of operational amplifier 16 is connected to its output end, and the output end of operational amplifier 16 is connected to capacitor C6, the negative electrode of diode D10, and the positive electrode of diode D9. The other end of the capacitor C6 and the anode of the diode D10 are connected to AGND, the cathode of the diode D9 is connected to 3.3V, and the current output signal is connected to the anode of the diode D9 and the cathode of the diode D10.

[0088] Figure 6 To protect the circuit diagram, the connection relationship is as follows:

[0089] The negative end of comparator 17 is connected to the feedback current CurFk port, the positive end is connected to 3.3V, the output end is connected to pin 1 of OR gate 19, the negative end of comparator 18 is connected to the feedback voltage VolFk port, the positive end is connected to 3.3V, the output end is connected to pin 2 of OR gate 19, the output end of OR gate 19 is connected to the input end of inverter 20, the output end of inverter 20 is connected to resistor R12 and protection signal Pro, and the zero end of resistor R12 is connected to 3.3V.

[0090] Embodiment 3

[0091] (1) Construction principle of sliding mode observer

[0092] The voltage equation of PMSM in the α-β coordinate system can be expressed as:

[0093]

[0094] Where i s is the stator current, i s =(i α ,i β ) T ;

[0095] u s is the stator voltage, u s =(u α ,uβ ) T ;

[0096] E s is the motor back electromotive force, E s =(E α ,E β ) T ;

[0097] A is the coefficient matrix, A=(-R s / L s )I;

[0098] B is the coefficient matrix, B = (1 / L s )I;

[0099] I is the identity matrix;

[0100] R s is the stator resistance;

[0101] L s is the stator inductance.

[0102] Since the electrical time constant of PMSM is very small, the back EMF is regarded as the disturbance of the system, and the sliding mode observer equation is as follows:

[0103]

[0104] In the formula is the estimated value of stator current,

[0105] K is K=kI, where k is the sliding mode gain.

[0106] Subtracting equations (1) and (2) will yield the motor current observation error equation:

[0107]

[0108] In the formula The sliding plane.

[0109] If the condition s is met T .s<0, the observer will enter the sliding mode state, at this time Define equivalent controls:

[0110]

[0111] To ensure the convergence of equation (4), the sliding mode gain k must satisfy k>max(|e α |,|e β |).

[0112] Since the Z variable contains back electromotive force information, the estimated value of the position angle can be obtained by filtering it and then performing an inverse tangent transformation:

[0113]

[0114]

[0115] In the formula is the estimated back EMF of the motor α and β axes;

[0116] z a ,z β is the equivalent control function of the sliding mode of α and β axes;

[0117] is the estimated motor rotor position angle;

[0118] ω c is the cutoff frequency of the low-pass filter.

[0119] (2) Compensation method

[0120] Since a low-pass filter is used to obtain the back EMF, a phase delay is introduced. The phase delay is related to the cutoff frequency of the low-pass filter. The lower the cutoff frequency, the greater the phase delay. Therefore, it is necessary to compensate for the phase delay. There are usually two compensation methods:

[0121] ① When the cutoff frequency of the low-pass filter is ω c When the value is fixed, the corresponding deviation angle Δθ is calculated according to the actual running speed ω. Compensation is performed to obtain the estimated rotor position angle θ:

[0122]

[0123] ② Low-pass filter cutoff frequency ω c When a fixed value is not used, its value is generally selected as N times the actual operating speed ω (the value of N is generally 2 to 5, such as 3). Since the value of N is a constant, the compensation angle Δθ is a fixed value, and then the rotor position angle estimation value θ is obtained according to formula (7).

[0124] In the above two methods, the cutoff frequency in method 1 is fixed, so the compensation effect is not obvious when the motor is at medium and low speed. Therefore, the method of changing the cutoff frequency in method 2 is often used. However, both methods use the actual speed to calculate the compensation value, and the calculated value of the actual speed is easily affected when the position-free algorithm is used. Especially when the motor control mode is switched, once the compensation angle calculation deviation is large and the rotor position angle is inaccurate, it will seriously affect the motor operation and even cause protection shutdown. For this reason, the following improvements are made on the basis of method 2:

[0125] (1) When calculating the deviation angle, the speed reference value ω is used * Instead of the actual speed ω, the cutoff frequency ω c Select the speed reference value ω * N times.

[0126] ① If the speed reference value ω * The speed reference value is much larger than the current speed ω, and a segmentation strategy is adopted to keep a certain difference between the speed reference value and the current speed value until it is equal to the final reference value ω. * Consistency;

[0127] Segmentation strategy: If the speed reference value ω * Much larger than the current speed ω, the cutoff frequency ω c The final speed reference value ω is no longer selected * N times, but choose a speed reference value that maintains a certain difference Δω with the current speed ω N times, where When the actual motor speed reaches When the speed Still much smaller than ω * , cut-off frequency ω c Select and current speed Maintain a certain difference Δω speed reference value N times, where And so on, until the motor speed reaches the final set speed ω * , cut-off frequency ω c Then select ω * N times. The difference Δω is the set value. That is, if the speed reference value ω * Much larger than the current speed ω, the cut-off frequency ω is gradually increased in a step-by-step manner c , until it reaches the speed reference value ω * N times.

[0128] Among them, according to the angle value estimated by the sliding mode observer, the current speed ω of the motor can be obtained by differentiating the angle value and filtering it, and then compared with the speed reference value ω * The speed reference value is set by the tester through external (touch screen) input.

[0129] ②When the permanent magnet synchronous motor adopts sensorless control, when the motor speed reaches a certain speed ω q When the control mode is switched, it is necessary to switch to the speed current dual closed loop mode. Therefore, before the control mode is switched, the filter cutoff frequency is fixed to the switching speed ω q N times. Due to the switching speed ω q Generally, it is 10% of the rated speed. Usually, in the speed range from when the motor starts to before switching, the filter cutoff frequency is fixed to the switching speed ω qN times, and does not adjust with the speed change.

[0130] (2) Compensation strategy: When the permanent magnet synchronous motor is at medium and low speed, its back electromotive force is small and the sliding mode observer calculation is not very accurate. At this time, the offset angle compensation effect is not good. The best offset angle compensation effect is when the motor completes the control mode switching and the speed reaches more than 20% of its rated speed.

[0131] According to the improved sliding mode observer method described above, the present invention uses the DSP28335 control board to perform software programming, implements the above control algorithm, and conducts motor tests. The test results show that the improved sliding mode observer algorithm effectively improves the detection accuracy of the rotor position angle, and the power factor of the inverter is also further improved.

[0132] Fourth embodiment

[0133] Figure 7 To improve the sliding mode observer algorithm flow chart, the control algorithm is written in C language and runs in the DSP control board 6. Figure 7 (a) is the main program flow chart, (b) is the timer interrupt subroutine flow chart, the timer interrupt subroutine is executed in the main program, mainly to complete the large moment of inertia control and speed current dual loop vector control algorithm, the specific implementation method is as follows:

[0134] The specific implementation of the main program is as follows:

[0135] (I) Start

[0136] The program starts from the main program entry, S1;

[0137] (Ⅱ) Initialization

[0138] Initialize DSP and complete the initialization of DSP peripheral clock, watchdog, IO port (input and output) and interrupt vector table, S2;

[0139] (III) Configuration Register

[0140] Configure the timer, PWM register, SCI register and interrupt register, and enable the related interrupt function, S3;

[0141] (IV) Initialize software parameters

[0142] Initialize timer, PWM duty cycle, delay time, RS232 communication software and other related parameters, S4;

[0143] (V) Loop Waiting

[0144] Enter the main loop and wait for the timer interrupt to occur, S5;

[0145] (VI) Execute the interrupt program and return

[0146] Execute the timer interrupt subroutine, return to the main program after completion, and wait in a loop, S6.

[0147] The specific implementation of the timer interrupt subroutine is as follows:

[0148] (Ⅰ) Interruption start

[0149] A timer interrupt occurs, and the timer interrupt program is entered, S7;

[0150] (II) Has it been started?

[0151] Determine whether the motor is started. If it is started, execute the improved sliding mode observer algorithm. Otherwise, enter the motor positioning start procedure, S8;

[0152] (Ⅲ) Motor positioning start

[0153] After entering the motor starting procedure, a sufficiently large DC current is first passed through the motor stator winding to position the rotor to a given initial position, completing the motor pre-positioning, and starting the motor using the IF control method to bring the motor to the set switching speed, S9;

[0154] (IV) Improved sliding mode observer

[0155] Execute the sliding mode observer algorithm to calculate the rotor position angle of the motor, and calculate the compensation angle value according to the current speed and the set speed reference value, and execute the corresponding compensation strategy, S10;

[0156] (V) Is it possible to switch

[0157] Determine whether the motor reaches the set switching speed. If the condition is met, execute the motor switching strategy. Otherwise, the interrupt is completed and returns to the main program to wait for the motor to reach the set speed, S11;

[0158] (VI) Motor switching control

[0159] After the motor reaches the set speed, the motor switching strategy is executed and switched to the speed and current double closed loop vector control mode, S12;

[0160] (VII) Motor double closed loop operation

[0161] Perform vector coordinate transformation and execute the motor space vector control algorithm to ensure that the motor is in the speed and current dual closed-loop vector control mode after switching or during normal operation, S13;

[0162] (Ⅷ) Return to the main program after the interrupt is completed

[0163] Complete the motor operation control algorithm, interrupt completion and return to the main program, S14.

[0164] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by those skilled in the art without inventive effort falls within the protection scope of the present invention.

Claims

1. A method for controlling the rotor position angle of a permanent magnet synchronous motor, characterized in that: Establish a sliding mode model and obtain the position angle estimation equation In the formula is the estimated back EMF of the motor α and β axes; z a ,z β is the equivalent control function of the sliding mode of α and β axes; is the estimated motor rotor position angle; ω c is the cut-off frequency of the low-pass filter, and also includes the step of compensating the above position angle for the offset angle. The offset angle calculation method is: Among them, ω is the actual operating speed, Δθ is the calculated corresponding offset angle, and θ is the estimated value of the rotor position angle obtained by compensation; Cut-off frequencyω c Select as the speed reference value ω * N times, if the speed reference value ω * The current speed ω is much larger than the current speed ω, and the segmentation strategy is adopted to gradually make the current speed ω close to the speed reference value ω. * ; The segmentation strategy is if the speed reference value ω * Much larger than the current speed ω, the cutoff frequency ω c The final speed reference value ω is no longer selected * N times, but choose a speed reference value that maintains a certain difference Δω with the current speed ω N times, where When the actual motor speed reaches When the speed Still much smaller than ω * , cut-off frequency ω c Select and current speed Maintain a certain difference Δω speed reference value N times, where And so on, until the motor speed reaches the final set speed ω * , cut-off frequency ω c Then select ω * N times; the difference Δω is the set value; Among them, when the motor speed reaches a certain speed ω q When the control mode is switched, it is necessary to switch to the speed and current dual closed loop mode. Before the control mode is switched, in the speed range from the motor starting to before the switch, the filter cutoff frequency is fixed to the switching speed ω q N times of the rated speed, after the motor completes the control mode switching, the deviation angle compensation is performed when the speed reaches more than 20% of its rated speed.

2. The control method according to claim 1, characterized in that: The voltage equation of PMSM in the α-β coordinate system is expressed as: Where i s is the stator current, i s =(i α ,i β ) T ; u s is the stator voltage, u s =(u α , u β ) T ; E s is the motor back electromotive force, E s =(E α ,E β ) T ; A is the coefficient matrix, A=(-R s / L s )I; B is the coefficient matrix, B = (1 / L s )I; I is the identity matrix; R s is the stator resistance; L s is the stator inductance; Since the electrical time constant of PMSM is very small, the back EMF is regarded as the disturbance of the system, and the sliding mode observer equation is as follows: In the formula is the estimated value of stator current, K is K = kI, where k is the sliding mode gain; Subtracting equations (1) and (2) will yield the motor current observation error equation: In the formula is the sliding plane; If the condition s is met T .s<0, the observer will enter the sliding mode state, at this time Define equivalent controls: To ensure the convergence of equation (4), the sliding mode gain k must satisfy k>max(|e α |,|e β |); Since the Z variable contains back electromotive force information, the estimated value of the position angle can be obtained by filtering it and then performing an inverse tangent transformation.

3. A control system for realizing the rotor position angle of a permanent magnet synchronous motor as claimed in any one of claims 1 to 2, characterized in that: It includes a rectifier bridge, an inverter bridge, a PWM drive module, a control board, a DC voltage detection circuit whose output is electrically connected to the control board and is used to detect the output voltage of the rectifier bridge, a current detection circuit whose output is electrically connected to the control board and is used to detect the stator current of the permanent magnet synchronous motor, and a protection circuit connected to the output of the DC voltage detection circuit and the output of the current detection circuit, wherein the output of the protection circuit is respectively connected to the control board and the PWM drive module.

4. A control system for the rotor position angle of a permanent magnet synchronous motor according to claim 3, characterized in that: The positive output of the rectifier bridge is connected in series with a charging resistor and then connected to the input end of the three-phase inverter bridge. A DC contactor is connected in parallel to the charging resistor, and the DC contactor is driven to be turned on or off by a control board.

5. The control system for the rotor position angle of a permanent magnet synchronous motor according to claim 3, characterized in that: The voltage sampling module is used to collect the output voltage of the rectifier, and includes a first operational amplifier with positive and negative input terminals and a voltage collection terminal. The output of the first operational amplifier is connected to the signal processing module after passing through a signal adjustment unit. At the same time, the output of the first operational amplifier is connected to the input terminal through a resistor R4; the current sampling module is used to collect the output current of the rectifier, and includes a mutual inductor arranged at the negative output, a second operational amplifier whose positive and negative terminals are electrically connected to the two ends of the mutual inductor respectively, and at the same time, the output of the second operational amplifier is connected to the input terminal through a resistor R8, the output of the second operational amplifier is connected to the positive terminal of the third operational amplifier after passing through a resistor R10, the output of the third operational amplifier is connected to the negative terminal, and the output of the third operational amplifier is connected to the signal processing module after passing through a signal adjustment unit. The signal adjustment unit includes a first diode and a second diode, the negative terminal of the first diode is connected to a positive voltage, the positive terminal is connected to the negative terminal of the second diode, the positive terminal of the second diode is grounded, and the outputs of the first operational amplifier and the third operational amplifier are connected between the two diodes.

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