Position detection device and method of permanent magnet synchronous motor based on variable frequency tracking

Abstract

The present invention discloses a position detection device and method for a permanent magnet synchronous motor based on variable frequency tracking, and belongs to the technical field of motor control. The present invention aims to solve the problem that the existing sliding mode observer may cause system jitter and low accuracy of dynamic estimation of back electromotive force during the detection process. α 、u β Obtain a stator current estimation value #imgabs0# and obtain a stator current frequency f according to the stator current estimation value #imgabs1#; obtain a back electromotive force estimation value #imgabs2# according to the stator current frequency f and the stator current deviation value; #imgabs3# and obtain a rotor position angle estimation value of the permanent magnet synchronous motor according to the back electromotive force estimation value #imgabs4#. The present invention solves the problem of system jitter caused by the existing sliding mode observer and low accuracy of back electromotive force estimation in dynamic processes.

Description

Technical Field

[0001] The present invention relates to the field of motor control, and in particular to a position detection device and method for a permanent magnet synchronous motor based on variable frequency tracking. Background Art

[0002] Multiphase PMSM has the advantages of high output power, low torque pulsation, low harmonic content, and high reliability. It has broad application prospects in electric vehicles, ship propulsion, aerospace, rail transportation and other occasions that require high power and high reliability. Multiphase PMSM control systems need to install position sensors to detect rotor position information, but position sensors increase system costs and reduce system reliability, limiting their application scenarios. Therefore, in order to improve system reliability, position sensorless detection technology is a feasible technical solution.

[0003] The multi-phase PMSM position-free detection technology is generally divided into two categories: one is the high-frequency injection method suitable for low-speed and zero-speed areas, which uses the motor rotor salient effect to estimate the rotor position and speed. The estimation accuracy is independent of the speed and is insensitive to changes in motor parameters. However, this method requires the PMSM to have a certain salient polarity. In addition, the amplitude of the injected high-frequency signal must be well controlled, otherwise it will cause electromagnetic noise. The other is the estimation of the rotor position and speed suitable for medium and high speeds, which relies on the motor back electromotive force, such as the extended Kalman filter method, the model reference method, and the sliding mode observer method.

[0004] The existing sliding mode observer will cause system chattering and has low accuracy in dynamic estimation of back electromotive force during the detection process. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a position detection device and method for a permanent magnet synchronous motor based on variable frequency tracking, which suppresses system vibration through stator current tracking and improves the estimation accuracy of back electromotive force.

[0006] The present invention provides a position detection device for a permanent magnet synchronous motor based on variable frequency tracking, comprising:

[0007] Sliding mode observation module, used to calculate the stator voltage u α 、u β Get the estimated value of stator current

[0008] A phase-locked loop module is used to estimate the stator current according to the stator current Get the stator current frequency f;

[0009] A stator current variable frequency tracking module is used to obtain a back electromotive force estimation value according to the stator current frequency f and the stator current deviation value. The back EMF estimate Feedback to step S1;

[0010] A third-order extended state observer is used to estimate the back electromotive force according to the Get the estimated value of the rotor position angle of the permanent magnet synchronous motor

[0011] Another aspect of the present invention provides a position detection method for a permanent magnet synchronous motor based on variable frequency tracking, comprising the following steps:

[0012] S1, according to the stator voltage u α 、u β Get the estimated value of stator current

[0013] S2. According to the stator current estimated value Get the stator current frequency f;

[0014] S3. Obtaining a back electromotive force estimation value according to the stator current frequency f and the stator current deviation value The back EMF estimate Feedback to step S1;

[0015] S4, according to the estimated value of the back electromotive force Get the estimated value of the rotor position angle of the permanent magnet synchronous motor

[0016] Preferably, step S1 specifically includes:

[0017] S11. Establish a permanent magnet synchronous motor model in the α-β coordinate system:

[0018]

[0019] S12: Establish an improved sliding mode observer according to the permanent magnet synchronous motor model to obtain a stator current deviation value. The improved sliding mode observer is:

[0020]

[0021] Among them, F() is the FVT function.

[0022] Preferably, step S2 comprises:

[0023] S21, according to the estimated value of stator current The current variation Δi is obtained, and the current variation Δi is:

[0024]

[0025] S22, the current change is adjusted by PI to obtain the angular frequency ω f, according to the angular frequency ω f Get the position angle And fed back to step S21, the angular frequency ω f for:

[0026]

[0027] S23, according to Get the stator current frequency f.

[0028] Preferably, the position angle in step S22 is Obtained according to the following formula:

[0029]

[0030] Preferably, the back electromotive force estimation value in step S3 is Obtained according to the following formula:

[0031]

[0032] Preferably, step S4 comprises:

[0033] S41, according to the rotor position angle change As input, the rotor position angle estimate is obtained through a three-stage extended state observer

[0034] The rotor position angle estimate is obtained according to the following formula

[0035]

[0036] is the motor rotor speed, J is the moment of inertia, P is the number of pole pairs, T L is the load torque, Q is the total disturbance of the system;

[0037] S42, the rotor position angle estimation value is used as feedback to calculate the rotor position angle variation Make corrections.

[0038] As described above, compared with the prior art, the present invention has the following effects:

[0039] 1. The present invention extends the concept of traditional three-phase position sensorless control technology to the motor mathematical model in multi-dimensional space, and realizes the stable operation of a six-phase permanent magnet synchronous motor based on position sensorless control.

[0040] 2. The present invention designs a FVT sliding mode observer, which adopts the FVT function to replace the switching function of the traditional sliding mode, so as to resist the influence of torque pulsation and harmonic components on the back electromotive force value estimated by the traditional SMO, and improve the estimation accuracy of the back electromotive force.

[0041] 3. The third-order ESO of the present invention processes the back electromotive force obtained by the FVT to estimate the position and speed of the rotor. The third-order ESO of the present invention can resist disturbances and improve estimation accuracy.

[0042] 4. The present invention can be applied to aerospace, electric vehicles and other occasions that have high requirements on the reliability and dynamic performance of motors, and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Attached Figure 1 It is a topological diagram of a six-phase inverter with dual three-phase winding neutral point isolation of the present invention;

[0044] Attached Figure 2 This is a star-type connection diagram of the isolated neutral point of the stator winding of the six-phase permanent magnet synchronous motor of the present invention;

[0045] Attached Figure 3 It is a block diagram of stator current frequency detection based on PLL of the present invention;

[0046] Attached Figure 4 It is the structural block diagram of FVT of the present invention;

[0047] Attached Figure 5 It is a block diagram of the rotor position information estimation based on the third-order ESO of the present invention;

[0048] Attached Figure 6 It is the structure diagram of the third-order ESO of the present invention;

[0049] Attached Figure 7 It is the overall implementation block diagram of the novel SMO of the present invention;

[0050] Attached Figure 8 This is a comparison diagram of the 500r / min speed waveform of the present invention;

[0051] Attached Fig. 9 This is the 500r / min speed error waveform diagram of the present invention;

[0052] Attached Fig.10 This is a 500r / min rotor position angle comparison waveform diagram of the present invention;

[0053] Attached Fig.11 This is the 500r / min rotor position angle error waveform diagram of the present invention;

[0054] Attached Fig.12 This is a comparison diagram of the rotor position angle error waveform at 500 r / min of the present invention;

[0055] Attached Fig.13 It is the main flow chart of the system of the present invention;

[0056] Attached Fig.14It is the main program flow chart of the present invention;

[0057] Attached Fig.15 It is a flow chart of the interrupt program of the present invention;

[0058] Attached Fig.16 It is the DSP power supply circuit diagram of the present invention;

[0059] Attached Fig.17 It is a voltage sampling circuit diagram of the present invention;

[0060] Attached Fig.18 It is the AC current sampling circuit diagram of the present invention;

[0061] Attached Fig.19 is a DC bias circuit diagram of the present invention;

[0062] Attached Fig. 20 This is the overcurrent protection circuit diagram of the present invention;

[0063] Attached Fig.21 It is the driving circuit diagram of 2SD315AI of the present invention; DETAILED DESCRIPTION

[0064] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0065] It should be noted that the illustrations provided in the following embodiments are only used to illustrate the basic concept of the present invention in a schematic manner, and thus the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0066] In a specific embodiment, if Figure 7 As shown, a position detection device of a permanent magnet synchronous motor based on variable frequency tracking in this embodiment includes:

[0067] Sliding mode observation module, used to calculate the stator voltage u α 、u β Get the estimated value of stator current

[0068] A phase-locked loop module is used to estimate the stator current according to the stator current Get the stator current frequency f;

[0069] A stator current variable frequency tracking module is used to obtain a back electromotive force estimation value according to the stator current frequency f and the stator current deviation value. The back EMF estimate Feedback to step S1;

[0070] A third-order extended state observer is used to estimate the back electromotive force according to the Get the estimated value of the rotor position angle of the permanent magnet synchronous motor

[0071] Depend on Fig.13 As can be seen from the main flow chart of the system, the position detection device of the permanent magnet synchronous motor based on variable frequency tracking includes a control circuit, a voltage and current sampling circuit, an overcurrent protection circuit, an IGBT drive circuit, and a six-phase PMSM.

[0072] The hardware circuit of the control system of this embodiment is mainly composed of control circuit, voltage and current sampling circuit, overcurrent protection circuit, IGBT driving circuit, etc. DSP architecture is adopted. During operation, the DSP chip uses TMS320F28335 of TI company. The DSP chip is mainly responsible for the operation of processed sampling signals, command current extraction, current tracking control algorithm, and inductive control algorithm. The phase voltage and phase current of the motor sampled by the voltage and current sampling circuit are processed and transmitted to the DSP control circuit. The voltage and current analog signals obtained by the sampling circuit are processed by digital signal through the ADC conversion unit of the DSP. Then, the motor rotor position information is estimated by the SMO algorithm on the DSP chip to realize the double closed loop of speed and current. The received modulation signal data is compared with the modulation wave and the carrier to obtain a PWM signal with a dead zone. The PWM is amplified by the driving circuit to drive the power switch tubes in each phase inverter to work.

[0073] The main program of TMS320F28335 is mainly used to complete system initialization and interruption. The interruption program includes AD sampling, fault diagnosis, FVT and ESO calculation, speed loop and current loop, etc. Fig.14 In the main program flow chart of the system shown in FIG, when the system starts running, all interrupts are turned off and the system is initialized, completing the initial settings of each unit used in the program. After the initialization is completed, the interrupt is turned on, the timer is started, and the interrupt is waited.

[0074] The flowchart of the interrupt subroutine is as follows Fig.15 It is used to complete the sampling of phase voltage and current, estimate the rotor position and speed, speed loop PI regulation, current loop PI regulation, coordinate transformation, and output the control signal to the power module through the SVPWM algorithm to control the motor operation.

[0075] like Fig.16 The figure shows the DSP power supply circuit, which uses the TPS767D301 chip to power the DSP and outputs two stable DC voltages, 1.9V to supply the DSP core and 3.3V DC to supply the I / O port.

[0076] like Fig.17 The figure shows a voltage sampling circuit. The phase voltage and DC bus voltage are collected through an isolation amplifier. The principle is to use a voltage divider resistor on the high-voltage side to obtain a small voltage, and isolate the voltage in a differential manner through an isolation amplifier. The output side of the isolation amplifier is also output in a differential manner, and then passes through an operational amplifier to convert the differential signal into a single-ended signal and send it to the DSP.

[0077] like Fig.18 The figure shows the AC current sampling circuit, which collects the AC current of the motor through the current Hall sensor. The model of the current Hall sensor is HA2020 produced by YHDC. The maximum sampling current value is 100A, the power supply is ±15V, and the transformation ratio is 2000:1.

[0078] like Fig.19 The figure shows a DC bias circuit, which limits the voltage amplitude of the current sampling signal to between 0-3V through the bias circuit. The bias voltage of 1.65V is generated by the voltage divider of resistors R37 and R39. Resistor R39 and capacitor C10 form a first-order RC filter circuit. The Schottky diode D2 constitutes a clamping circuit for the sampling voltage to prevent the voltage entering the DSP from being too large, which may damage the chip.

[0079] The overcurrent protection circuit in this embodiment is as follows: Fig. 20 As shown, the main function is to prevent the phase current of the motor from exceeding the rated value of the IGBT switch tube, causing the IGBT switch tube to burn out. The circuit is composed of a comparator to form a voltage comparator. The sampled current signal passes through the bias circuit and is compared with the limit value. If the voltage value of the biased current signal is higher than 4.5V or lower than 0.6V, the control system blocks the PWM output. The selection of the limit value is related to the motor rating and the gain of the sampling circuit.

[0080] The driving circuit is used to amplify the low-level and low-power control signal output by the DSP so that it can drive the power switch tube. Fig.21As shown, the driving circuit of this embodiment uses the driving module model 2SD315AI launched by the Swiss CONCEPT company, which has two working modes: direct mode and half-bridge mode. The 8-pin MOD of the driver is short-circuited with VDD, and it works in direct mode. At this time, channels A and B have no relationship, and the two channels work independently. RC1 and RC2 are short-circuited with GND, and the state output SO1 / SO2 also works independently. The 8-pin MOD of the driver is short-circuited with GND, and it works in half-bridge mode. A dead time is generated between the two channels. The dead time is adjusted by the RC network between pins 5 and 7. At this time, INB is connected to a high level to enable, and INA is the total input terminal of the two signals.

[0081] In a specific embodiment, a method for position detection of a permanent magnet synchronous motor based on variable frequency tracking includes the following steps:

[0082] S1, according to the stator voltage u α 、u β Get the estimated value of stator current

[0083] This embodiment designs a sliding mode stator current frequency conversion tracker through a permanent magnet synchronous motor model to independently estimate the electromotive force, specifically including:

[0084] S11. Establish a permanent magnet synchronous motor model in the α-β coordinate system:

[0085]

[0086] Where: i α 、i β are the components of the stator current on the α-β axis, R is the stator winding of the motor, L s is the self-inductance coefficient of the stator winding, e α 、e β are the components of the back electromotive force on the α-β axis, which can be expressed as:

[0087]

[0088] S12: Establish an improved sliding mode observer according to the permanent magnet synchronous motor model to obtain a stator current deviation value.

[0089] The sliding mode observer dynamically changes the system structure to make the state variable trajectory move along the ideal sliding mode surface. Taking the current component as the state variable, it can be obtained from formula (1):

[0090]

[0091] According to sliding mode variable structure control theory, the sliding surface is defined as The traditional sliding mode switching function is the switching function, and the current sliding mode observer in the α-β coordinate system is:

[0092]

[0093] Where: sign() is the switching function, which is the traditional sliding mode switching function; is the estimated value of stator current; K s is the sliding mode gain, and its value range must satisfy the stability, existence and reachability conditions of the sliding mode observer.

[0094] From equations (3) and (4), the current deviation equation can be obtained as:

[0095]

[0096] Where: Estimate the current error for the observer.

[0097] Since the discrete switching characteristics of the sign function in the traditional SMO easily lead to high-frequency jitter in the estimated back electromotive force, to address this problem, this embodiment uses the FVT function to replace the original switching function sign() to track the fundamental wave of the stator current, and obtains the specific current deviation equation as shown in formula (6):

[0098]

[0099] The improved sliding mode observer is established in the α-β coordinate system as shown in formula (7):

[0100]

[0101] S2. According to the stator current estimated value Get the stator current frequency f;

[0102] In the prior art, proportional resonant control (PR) is usually used to track a specific frequency, and the stator current error can converge at a specific frequency. However, during the actual operation of the motor, the frequency of the stator current changes with the speed. When the frequency changes, the traditional PR controller cannot accurately track the AC signal. In order to track the changing frequency, this embodiment adopts the following method: Figure 3 The PLL-based stator current frequency detection method shown detects the stator current frequency, specifically including:

[0103] S21, according to the estimated value of stator current The current variation Δi is obtained, and the current variation Δi is:

[0104]

[0105] S22, the current change is adjusted by PI to obtain the angular frequency ω f , according to the angular frequency ω f Get the position angle And fed back to step S21, the angular frequency ω f for:

[0106]

[0107] Among them, K p is the proportional gain, K i is the integral gain

[0108] Position angle for:

[0109]

[0110] S23, according to Get the stator current frequency f.

[0111] S3. Obtaining a back electromotive force estimation value according to the stator current frequency f and the stator current deviation value The back EMF estimate Feedback to step S1;

[0112] In this embodiment, FVT is used according to the stator current deviation value and stator current frequency f to obtain the estimated back EMF Specific as Figure 4 As shown, The FVT function is:

[0113]

[0114] Among them, K p is the proportional gain, K r is the resonant gain, ω c is the cutoff frequency.

[0115] In order to adapt to the changing frequency, the transfer function (11) is converted to the Z domain, and we get:

[0116]

[0117] Which then translates into:

[0118]

[0119] Define the state variables:

[0120]

[0121] Deriving the derivative of (14) yields the following state-space equation:

[0122]

[0123] The FVT function is obtained by formula (15):

[0124]

[0125] When the moving point converges to the sliding surface, the back electromotive force estimated by the improved sliding mode observer according to equation (7) is the FVT function output y, which is equivalent to:

[0126]

[0127] S4, according to the estimated value of the back electromotive force Get the estimated value of the rotor position angle of the permanent magnet synchronous motor

[0128] S41, according to the rotor position angle change As input, the rotor position angle estimate is obtained through a three-stage extended state observer

[0129] like Figure 5 As shown, it is a schematic diagram of the three-stage extended state observer of this embodiment. This embodiment establishes the following relationship:

[0130]

[0131] in, when

[0132] According to the relationship between the speed and the rotor position in the rotor motion equation, the rotor position angle θ can be established. e The state equation of the three-stage extended state observer (ESO) with is the main variable is shown in formula (19), and its structural principle diagram is shown in Figure 6 shown.

[0133] The rotor position angle estimate is obtained according to the following formula

[0134]

[0135] is the motor rotor speed, J is the moment of inertia, P is the number of pole pairs, T L is the load torque, Q is the total disturbance of the system;

[0136] S42, the rotor position angle estimation value is used as feedback to calculate the rotor position angle variation Make corrections.

[0137] As can be seen from the above, the present invention adopts the stator current variable frequency tracking function to replace the traditional switching function. By improving the SMO method, the independent estimation of the electromotive force is realized, and the accuracy is maintained in the startup or speed change state. Secondly, in order to improve the estimation accuracy and anti-disturbance ability of the observer, the rotor position is used as a disturbance term, and a third-order extended state observer (ESO) is constructed through the motor mechanical motion equation to estimate the speed and rotor position. In order to further illustrate and verify the embodiment of the present invention, this embodiment is analyzed by the simulation of the six-phase PMSM non-sensing operation:

[0138] The power side topology of the six-phase PMSM control system is an AC-DC-AC topology, that is, the 220V industrial frequency AC power is first passed through a rectifier bridge to obtain a DC bus voltage, and then the DC bus voltage output by the rectifier bridge is filtered and stabilized by a non-polarity filter capacitor and sent to a six-phase voltage inverter. This embodiment uses a six-phase voltage inverter with an anti-parallel diode structure to achieve inverter processing. The phase voltage and phase current of the motor are processed by a voltage and current sampling circuit and transmitted to a DSP control circuit. The voltage and current analog signals obtained by the sampling circuit are digitized by an ADC conversion unit of the DSP, and then the motor rotor position information is estimated by the SMO algorithm on the DSP chip to achieve a double closed loop of speed and current. The current closed loop is output to the SVPWM modulation algorithm to obtain a drive signal for the drive circuit; SVPWM modulation is achieved by controlling the on and off of the power devices in the inverter, thereby controlling the operation of the six-phase PMSM.

[0139] The motor is started with a load torque of 5 N·m and the given speed is set to 500 r / min. Figure 8 and Fig.10 The speed and rotor position angle waveforms are shown respectively. The solid line in the figure represents the estimated speed and position of the rotor, and the dotted line in the figure represents the actual speed and position measured by the motor. Fig. 9 and Fig.11 The waveforms of the speed error and rotor position angle error are shown respectively. It can be seen that the speed error is within ±1r / min and the rotor position angle error is very small. The observer can accurately estimate the speed and track the rotor position angle. Fig.12 The comparison of the rotor position angle error waveforms obtained by the conventional SMO and the improved SMO at 500r / min is shown. It can be seen from the figure that the rotor position angle error estimated by the improved SMO is smaller than that estimated by the conventional SMO, so the proposed position sensorless control algorithm can estimate the rotor angle more accurately.

[0140] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A position detection method for a permanent magnet synchronous motor based on variable frequency tracking, characterized in that: The steps include: S1, according to the stator voltage , Get the estimated value of stator current , , comprising the following steps: S11. Establish a permanent magnet synchronous motor model in the α-β coordinate system: ； In the formula, , are the components of the stator current on the α-β axis, R is the stator winding of the motor, L s is the self-inductance coefficient of the stator winding, , are the components of the back electromotive force in the α-β axis respectively; S12: Establish an improved sliding mode observer according to the permanent magnet synchronous motor model to obtain a stator current deviation value. , , the improved sliding mode observer is: ； in, is the FVT function; is the estimated value of stator current; Estimate the current error for the observer, respectively: , ; S2. According to the stator current estimated value , Obtaining the stator current frequency f includes the following steps: S21, according to the estimated value of stator current Get the current change , the current change for: ； S22, the current change is adjusted by PI to obtain the angular frequency , according to the angular frequency Get the position angle And fed back to step S21, the angular frequency for: ； in, is the proportional gain, is the integral gain; S23, according to Get the stator current frequency f; S3, according to the stator current frequency f and the stator current deviation value , Get the estimated back EMF , , the estimated back EMF value , Feedback to step S1; S4, according to the estimated value of the back electromotive force , Get the estimated value of the rotor position angle of the permanent magnet synchronous motor , including the following steps: S41, according to the rotor position angle change As input, the rotor position angle estimate is obtained through a three-stage extended state observer ; The rotor position angle estimate is obtained according to the following formula : ； in, is the motor rotor speed, J is the moment of inertia, P is the number of pole pairs, T L is the load torque, Q is the total disturbance of the system; S42, the rotor position angle estimation value is used as feedback to calculate the rotor position angle variation Make corrections.

2. The position detection method of a permanent magnet synchronous motor based on variable frequency tracking according to claim 1 is characterized in that: Step S22: Position angle Obtained according to the following formula: 。 3. The position detection method of a permanent magnet synchronous motor based on variable frequency tracking according to claim 1 is characterized in that: Step S3: Back electromotive force estimation value , Obtained according to the following formula: 。

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