High-frequency signal injection-based sensorless control method for permanent magnet synchronous motor
Technical Field
The invention belongs to the field of permanent magnet synchronous motor control, and relates to a high-frequency signal injection-based sensorless control method for a permanent magnet synchronous motor.
Background
The permanent magnet synchronous motor speed regulating system has the advantages of fast dynamic response, strong overload capacity, good stability and the like, and is suitable for the running states of various loads. The permanent magnet synchronous motor rotor is made of permanent magnet materials, has high power density, small volume and weight and flexible appearance size design, and is widely applied to various fields of national production and life. The electric energy is a main secondary energy source for production and life of the nation, the motor is used as a main body for electromechanical energy conversion and electric energy consumption, and the application of the motor relates to a plurality of aspects such as metallurgy, mines, electric power, petroleum, chemical industry, building intelligence, municipal administration, textiles, building materials and the like. In 2013, the Ministry of industry and informatization came out motor energy efficiency improvement plan, which provides policy guarantee and support for the performance improvement of a motor control system.
At present, most permanent magnet synchronous motor control systems need to acquire real-time position information of a rotor to perform speed closed-loop control and rotation coordinate transformation, generally, the position information of the rotor is acquired by mechanical position sensors, such as a photoelectric encoder, a rotary transformer, a hall element and the like, and the mechanical sensors bring the following problems to the system: the high-precision sensor is expensive, the system cost is increased, and the volume is increased; the signal is easy to be interfered by external electromagnetic waves in the transmission process, so that the stability of the system is reduced; under severe environment, a photoelectric encoder may not be used, a hall sensor is easily affected by temperature, and an external demodulation circuit is needed for a rotary transformer, so that the reliability of the system is reduced; the sensor increases the rotational inertia, and the dynamic performance of the system is influenced; the problems of concentricity, angle deviation and the like exist in the installation process of the position sensor, so that the system precision is reduced; some special occasions cannot install and use the sensor.
In order to effectively solve the problems and practically improve the control quality of a permanent magnet synchronous motor control system, domestic and foreign scholars try to estimate the position of a rotor through parameters such as voltage, current and the like which can be directly obtained in the motor operation process so as to replace a mechanical sensor, and thoroughly solve the problem of reduction of system stability, reliability and accuracy caused by sensing, thereby forming a sensorless control method of the permanent magnet synchronous motor.
Although the existing sensorless control method can well estimate the rotor position, the existing sensorless control method has certain limitations: when the permanent magnet synchronous motor operates in a zero/low speed range, the signal-to-noise ratio of a useful signal which can be detected is very low, even cannot be extracted, but the basic idea of the methods relying on the fundamental wave mathematical model is that the back electromotive force is in direct proportion to the rotating speed of the motor, and the speed value of the permanent magnet synchronous motor during zero/low speed operation is very small and even possibly zero, so that the method finally fails at zero/low speed, and the position of a rotor cannot be effectively estimated.
Disclosure of Invention
The invention aims to overcome the defects of low estimation precision, time delay, low dynamic response speed and the like in the prior art, provides a high-frequency signal injection-based permanent magnet synchronous motor sensorless control method, can effectively overcome the defects of the traditional rotor position estimation method through mathematical analysis derivation and calculation, adopts a compensation matrix method to directly obtain an analytical expression of the rotor position, eliminates the time delay problem caused by the use of a low-pass filter and a band-pass filter in the prior art, and effectively estimates the rotor position.
The invention provides a permanent magnet synchronous motor sensorless control method based on high-frequency signal injection, which is used for motor rotor position estimation in a permanent magnet synchronous motor sensorless control system and comprises the following steps:
step 1: establishing a fundamental wave mathematical model of the permanent magnet synchronous motor and a high-frequency excitation mathematical model under the excitation of a high-frequency voltage signal under a two-phase static coordinate system (alpha beta coordinate system);
step 2: injecting a high-frequency voltage excitation signal under a two-phase static coordinate system (alpha beta coordinate system), sampling according to a high-frequency excitation mathematical model, and obtaining a current item containing rotor position information so as to obtain a display expression of the rotor position;
and step 3: and sending the estimated rotor position to a rotating speed controller and a current controller to form a rotating speed-current double closed-loop control structure and generate a control signal.
In the sensorless control method of the permanent magnet synchronous motor based on high-frequency signal injection, the step 1 specifically includes:
step 1.1: establishing a fundamental wave mathematical model of the permanent magnet synchronous motor under a two-phase static coordinate system (alpha beta coordinate system), as shown in the following formula:
wherein [ u ]α uβ]TAnd [ iα iβ]TStator voltage and current under a two-phase static coordinate system are respectively; rsA stator winding resistor; l issA stator winding inductance; lambda [ alpha ]fIs a rotor permanent magnet flux linkage; thetaeIs the rotor position; omegaeIs the rotor speed; l is-A half-differential inductance;
wherein, the stator winding inductance matrix is:
wherein L is+Is average inductance, L-A half-differential inductance; l isd、LqRespectively a d-axis inductor and a q-axis inductor under a two-phase rotating coordinate system (dq coordinate system);
when the sampling time is sufficiently short, the fundamental mathematical model can be expressed in the form:
wherein, [ Delta i [ ]αΔiβ]TIs a current variable under a two-phase static coordinate system (alpha beta coordinate system); Δ T is the sampling time;
step 1.2: the injection frequency of the high-frequency signal is far higher than the fundamental frequency, the permanent magnet synchronous motor can be regarded as a simple RL loop, the stator resistance is far smaller than the reactance in high frequency, the rotary electromotive force is very small and can be ignored, and then a high-frequency excitation mathematical model of the permanent magnet synchronous motor under high-frequency excitation can be obtained by the formula (1.1):
when the sampling time is short, in terms of the differential term in the discrete quantity approximation equation (2.1), equation (2.1) can be written as follows:
in the sensorless control method of the permanent magnet synchronous motor based on the high-frequency signal injection, the step 2 is specifically as follows:
step 2.1: injection frequency of omega in two-phase stationary coordinate system (alpha beta coordinate system)inAmplitude of UinThe high-frequency voltage excitation signal of (2) is as follows:
wherein [ u ]αin uβin]ΤIs a high-frequency voltage signal injected under a two-phase static coordinate system.
Step 2.2: when the sampling time is short enough, the fundamental frequency components of the voltage and the current can be regarded as constants, and only the high-frequency component is taken as a variable, so that the voltage difference is only related to the current variable, and the difference is made between the sampling values of two sampling periods of the formula (2.2), so that the following results can be obtained:
wherein [ u ]α1 uβ1]TAnd [ u ]α2 uβ2]TFor the voltage in each sampling period, [ u ]α21 uβ21]TIs the voltage difference in the sampling period; [ Delta iα1Δiβ1]TAnd [ Delta i [ ]α2Δiβ2]TIs a sampled current corresponding to the sampled voltage.
Step 2.3: since the inductance matrix in equation (1.2) can be divided into rotor position dependent terms and rotor position independent terms, equation (3.2) is rewritten into the following form according to equation (1.2) and equation (1.3):
setting:
then there are:
a compensation matrix is arranged:
combining the following double angles and the sum and difference formulas of the two angles:
simplifying the left and right ends of the expression (3.5) by the expression (3.6) and the expression (3.7) to obtain 2 thetaeReduction of terms to thetaeTerm, the compensation matrix can be derived:
and the results at the left and right ends of the compensation matrix multiplier (3.5) are:
then, a display expression of the rotor position of the permanent magnet synchronous motor can be further obtained:
compared with the prior art, the sensorless control method of the permanent magnet synchronous motor based on high-frequency signal injection has the following advantages:
1. the invention provides a mathematical model under high-frequency excitation on the basis of a fundamental wave mathematical model, and simultaneously provides an improved permanent magnet synchronous motor rotor position estimation method based on high-frequency voltage signal injection in a two-phase static coordinate system.
2. The method adopts the compensation matrix and the voltage and current differential equation to obtain the rotor position information, omits the low-pass and band-pass filtering links used in the prior art, successfully eliminates the hidden trouble that the estimated rotor position lags behind the actual position due to the time delay brought by the filtering link, and greatly improves the estimation precision of the rotor position of the permanent magnet synchronous motor.
3. The invention obtains the rotor position display expression of the permanent magnet synchronous motor under the condition of high-frequency signal injection through rigorous and accurate mathematical derivation and analysis, improves the technology that the prior art can only indirectly obtain the rotor position, greatly reduces the estimation error compared with the prior art when the invention is adopted to estimate the rotor position, obviously improves the dynamic response speed, has strong robustness, and does not influence the rotor position estimation precision due to the change of motor parameters.
4. In order to verify the effectiveness of the method provided by the invention, the simulation link verification is specially carried out in an MATLAB/Simulink simulation environment, and the simulation result shows that the method can greatly improve the rotor position estimation precision.
Drawings
FIG. 1 is a block diagram of a sensorless control system for a PMSM in the practice of the present invention;
FIG. 2 is a rotor position estimation method of a sensorless control system of a conventional permanent magnet synchronous motor;
FIG. 3 illustrates a rotor position estimation method for a PMSM according to the present invention;
FIG. 4 is a rotation speed fluctuation simulation verification of the existing permanent magnet synchronous motor rotor position estimation method;
FIG. 5 is a rotation speed fluctuation simulation verification of the permanent magnet synchronous motor rotor position estimation method of the present invention;
FIG. 6 is a rotor position simulation verification of a prior art PMSM rotor position estimation method;
FIG. 7 is a simulation verification of rotor position for the PMSM rotor position estimation method of the present invention;
FIG. 8 is a simulation verification of rotor position estimation error of the existing PMSM rotor position estimation method;
FIG. 9 is a simulation verification of rotor position estimation error of the PMSM rotor position estimation method of the present invention.
Detailed Description
In order to realize sensorless control in a full speed range including zero/low speed, the invention provides that a high-frequency signal injection method is applied to a permanent magnet synchronous motor control system, the accurate estimation of the position of a rotor is realized through detected parameters such as motor voltage, current and the like, the time delay problem caused by the use of a low-pass filter and a band-pass filter in the prior art is eliminated, and the estimation precision and the dynamic response speed are improved.
Fig. 1 is a block diagram of a sensorless control system of a permanent magnet synchronous motor in the specific implementation process of the present invention, and the sensorless control system is divided into the following main parts:
(1) high frequency signal injection part
High-frequency signal generator continuously injects high-frequency signal u into systemαβinThe high-frequency signal is injected after the current controller, and generates a control signal along with the current controller and transmits the control signal to the PWM module, and the PWM module generates six paths of pulse signals to drive a power switch tube of a voltage type inverter VSI and drive a PMSM (permanent magnet synchronous motor) to operateAnd (6) rows.
(2) Signal processing section
The part is to extract three-phase high-frequency induction current i from the end of the permanent magnet synchronous motor
ABCTransformed by rotating coordinates T
3s/2sConverted to two-phase static coordinate system (alpha beta coordinate system), and converted current signal i
αβOne path is transformed by coordinates
After being converted into a two-phase rotating coordinate system (dq coordinate system), the two-phase rotating coordinate system is filtered by a low pass filter LPF and then is sent to a current controller, and the other path of current signal i
αβAnd sending the rotor position estimation algorithm module to estimate the rotor position.
(3) Rotor position estimating section
High frequency induced current i extracted from the motor end
αβThe method comprises the steps of extracting a rotor position related item and a rotor position unrelated item, obtaining a rotor position value through related operation, filtering the calculated rotor position value through a Low Pass Filter (LPF) and then sending the filtered rotor position value to a position/speed observer, outputting the observed speed of a rotor by the observer and then sending the observed speed to a speed controller to further obtain a control signal as shown in figure 3
Fig. 2 is a rotor position estimation method of a sensorless control system of a conventional permanent magnet synchronous motor.
FIG. 3 shows a three-phase high-frequency voltage u extracted from the end of a PMSM according to the method for estimating the rotor position of a PMSM according to the present invention
ABCAnd an induced current i
ABCTransformed by rotating coordinates T
3s/2sConverting the signal from ABC coordinate system to two-phase stationary coordinate system (alpha beta coordinate system), and obtaining delta i after the difference between the sampling values of current and voltage
αβ21And u
αβ21The rotor position expression is calculated to obtain a rotor position value, the calculated rotor position value is filtered by a low pass filter LPF and then is sent to a position/speed observer, and the observer outputs observed values of the rotating speed and the position
And
the invention discloses a high-frequency signal injection-based sensorless control method for a permanent magnet synchronous motor, which is used for estimating the position of a motor rotor in a sensorless control system of the permanent magnet synchronous motor and specifically comprises the following steps:
step 1: establishing a fundamental wave mathematical model of the permanent magnet synchronous motor and a high-frequency excitation mathematical model under the excitation of a high-frequency voltage signal under a two-phase static coordinate system (alpha beta coordinate system); the step 1 specifically comprises:
step 1.1: establishing a fundamental wave mathematical model of the permanent magnet synchronous motor under a two-phase static coordinate system (alpha beta coordinate system), as shown in the following formula:
wherein [ u ]α uβ]TAnd [ iα iβ]TStator voltage and current under a two-phase static coordinate system are respectively; rsA stator winding resistor; l issA stator winding inductance; lambda [ alpha ]fIs a rotor permanent magnet flux linkage; thetaeIs the rotor position; omegaeIs the rotor speed; l is-A half-differential inductance;
wherein, the stator winding inductance matrix is:
wherein L is+Is average inductance, L-A half-differential inductance; l isd、LqRespectively two-phase rotating coordinate system(dq coordinate system) under d-axis inductance and q-axis inductance;
when the sampling time is sufficiently short, the fundamental mathematical model can be expressed in the form:
wherein, [ Delta i [ ]αΔiβ]TIs a current variable under a two-phase static coordinate system (alpha beta coordinate system); Δ T is the sampling time;
step 1.2: the injection frequency of the high-frequency signal is far higher than the fundamental frequency, the permanent magnet synchronous motor can be regarded as a simple RL loop, the stator resistance is far smaller than the reactance in high frequency, the rotary electromotive force is very small and can be ignored, and then a high-frequency excitation mathematical model of the permanent magnet synchronous motor under high-frequency excitation can be obtained by the formula (1.1):
when the sampling time is short, in terms of the differential term in the discrete quantity approximation equation (2.1), equation (2.1) can be written as follows:
step 2: injecting a high-frequency voltage excitation signal under a two-phase static coordinate system (alpha beta coordinate system), sampling according to a high-frequency excitation mathematical model, and obtaining a current item containing rotor position information so as to obtain a display expression of the rotor position; the step 2 specifically comprises the following steps:
step 2.1: injection frequency of omega in two-phase stationary coordinate system (alpha beta coordinate system)inAmplitude of UinThe high-frequency voltage excitation signal of (2) is as follows:
wherein [ u ]αin uβin]ΤInjecting a high-frequency voltage signal under a two-phase static coordinate system;
step 2.2: when the sampling time is short enough, the fundamental frequency components of the voltage and the current can be regarded as constants, and only the high-frequency component is taken as a variable, so that the voltage difference is only related to the current variable, and the difference is made between the sampling values of two sampling periods of the formula (2.2), so that the following results can be obtained:
wherein [ u ]α1 uβ1]TAnd [ u ]α2 uβ2]TFor the voltage in each sampling period, [ u ]α21 uβ21]TIs the voltage difference in the sampling period; [ Delta iα1Δiβ1]TAnd [ Delta i [ ]α2Δiβ2]TIs a sampling current corresponding to the sampling voltage;
step 2.3: since the inductance matrix in equation (1.2) can be divided into rotor position dependent terms and rotor position independent terms, equation (3.2) is rewritten into the following form according to equation (1.2) and equation (1.3):
setting:
then there are:
a compensation matrix is arranged:
combining the following double angles and the sum and difference formulas of the two angles:
simplifying the left and right ends of the expression (3.5) by the expression (3.6) and the expression (3.7) to obtain 2 thetaeReduction of terms to thetaeTerm, the compensation matrix can be derived:
and the results at the left and right ends of the compensation matrix multiplier (3.5) are:
then, a display expression of the rotor position of the permanent magnet synchronous motor can be further obtained:
and step 3: and sending the estimated rotor position to a rotating speed controller and a current controller to form a rotating speed-current double closed-loop control structure and generate a control signal.
Fig. 4 to 9 are simulation studies conducted in the present invention and the prior art, and a system simulation model is built in the MATLAB/Simulink environment. The parameters of the permanent magnet synchronous motor are as follows: 2 pairs of poles, 5.2 millihenry of d-axis inductance, 17.4 millihenry of q-axis inductance, 0.33 ohm of stator resistance and 0.008 Newton-meter seconds of damping coefficient. The simulation conditions are as follows: DC side voltage Udc36V; PWM switching frequency fpwm5 kHz; adopting a variable step size ode45 algorithm; the relative error is 0.001. Injection amplitude Uin20V, frequency ωin1000Hz, sinusoidal high frequency voltage signal. The motor is arranged in a simulation wayThe simulation results are shown in FIGS. 4-9 when the operation is carried out under two working conditions that the rotation speed is suddenly changed from 30rpm to 50rpm under the conditions of 40rpm, no load and 0.1 s.
The following results can be obtained by simulation:
in a steady state, the simulation results of the prior art and the invention are as follows:
(1) the fluctuation of the rotating speed of the rotor position estimation method based on the heterodyne method is 10.5rpm, and the estimation error of the rotor position is 34.4 degrees;
(2) the fluctuation of the rotating speed of the rotor position estimation method based on the compensation matrix is 5rpm, and the estimation error of the rotor position is 14.3 degrees.
In the dynamic process, the simulation results of the prior art and the invention are as follows:
(1) the transition time of the rotor position estimation method based on the heterodyne method is 25ms, the rotating speed overshoot is 9rpm, and the estimated rotor position is obviously lagged behind the actual rotor position, so that the performance of the rotor position estimation method provided by the invention is obviously superior to that of the rotor position estimation method based on the heterodyne method;
(2) the transition time of the rotor position estimation method based on the compensation matrix is 16ms, the rotating speed overshoot is 5rpm, and the estimated rotor position is basically consistent with the actual rotor position. Therefore, the rotor position estimation method provided by the invention can still show good tracking performance in the dynamic transition process.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the scope of the present invention, which is defined by the appended claims.