CN104158462B - Method for detecting initial position of permanent magnet synchronous motor without position sensor - Google Patents

Abstract

The invention relates to a method for detecting the initial position of a permanent magnet synchronous motor without a position sensor, which is characterized in that under the condition of ensuring the motor to be in a static state, the current is subjected to open-loop control, the initial position of a rotor is initialized, high-frequency cosine voltage signals are injected through an estimated direct axis under an estimated synchronous rotating coordinate system, estimated high-frequency quadrature axis current is extracted, and the estimated high-frequency quadrature axis current is subjected to signal processing and adjustment to obtain an initial value of the initial position of the rotor; and continuously injecting a plurality of high-frequency cosine voltage signals with determined periods into the estimated direct axis, and judging the polarity of the magnetic pole and obtaining the accurate initial position of the rotor by judging the positive and negative of the integral value of the current of the estimated direct axis. The method and the device do not need to acquire motor parameters, effectively avoid the problems that the existing method for detecting the initial position of the rotor possibly causes the rotation of the motor and the detection of an identification signal is difficult, do not need to increase hardware, are convenient to realize, and realize the accurate acquisition of the initial position of any rotor magnetic pole of the motor in a static state.

Description

A method for detecting initial position of permanent magnet synchronous motor without position sensor

technical field

The invention relates to a method for judging the initial polarity of a motor rotor, and belongs to the field of motor control, in particular to a method for detecting the initial position of a permanent magnet synchronous motor without a position sensor.

Background technique

Permanent magnet synchronous motors have been widely used in the field of AC drives due to their excellent running performance. However, the control of the permanent magnet synchronous motor needs to know the accurate rotor position and speed. The mechanical sensors installed for this purpose, such as photoelectric encoders and resolvers, not only increase the size and cost of the system, but also reduce the reliability of the system. , which limits the applications of permanent magnet synchronous motors. Therefore, many experts and scholars have devoted themselves to the research of position sensorless in recent years. Among them, the initial position detection of the motor rotor has always been an important and urgent problem to be solved, and its accuracy directly determines whether the motor can be started smoothly and can be started with the maximum torque.

At present, scholars at home and abroad have proposed a variety of methods for detecting the initial position of permanent magnet synchronous motors without position sensors. If the rotor is allowed to rotate during start-up, the simplest and most effective method is to supply direct current to the stator to generate a static magnetic field to position the rotor at the set zero position and complete the initialization of the rotor position. However, in many applications, it is required that the motor can start normally at any static position, so some scholars have proposed a high-frequency signal injection method. Such methods are applicable to salient pole and hidden pole permanent magnet synchronous motors. The basic principle is to obtain the rotor position by detecting the current or voltage signal. This type of method is generally implemented in two steps. First, the rotor position is initially estimated, and then the magnetic polarity is detected and compensated to obtain the final rotor initial position. Among them, there are usually two ways to detect the polarity of the magnetic pole, both of which are realized by injecting positive and negative voltage pulses of equal amplitude and width on the estimated direct axis. One is determined by comparing the current peak value generated at this time, and the other is determined by comparing the time when it rises or falls to a certain current value. However, both of the above methods must choose the amplitude and duration of the injected signal reasonably. If the signal amplitude is too large or the duration is too long, it may cause the motor to rotate, and if the amplitude is too small or the duration is too short, the peak difference or time difference of the current cannot be detected.

Contents of the invention

The present invention aims to propose a method for detecting the initial position of a permanent magnet synchronous motor without a position sensor, especially a method for detecting the polarity of magnetic poles, so as to solve the problems existing in existing methods that may cause defects in motor rotation and difficult detection of identification signals.

In order to solve the existing problems of the background technology, the technical solution adopted in the present invention is:

A method for detecting the initial position of a permanent magnet synchronous motor without a position sensor, the method comprising the steps of:

Step 1: Define the actual angle as θ and the estimated angle as And lagging behind θ, the estimated angle error is Δθ, the actual direct axis is the d axis, the actual quadrature axis is the q axis, and the estimated direct axis is axis, the estimated intersection axis is axis, the actual synchronous rotating coordinate system is dq, and the estimated synchronous rotating coordinate system is Then, under the condition of ensuring the static state of the motor, open-loop control is performed on the current, and the initial position of the rotor is initialized, that is, an initial position of the rotor is arbitrarily assumed first;

Step 2: In The shaft injects a continuous high-frequency cosine voltage signal, that is, given Shaft voltage is Transform the detected and sampled A and B two-phase winding current signals i _a and i _b into coordinates to obtain Axial current high frequency response in

Step 3: Due to the obtained Axial current high frequency response in Contains signals related to rotor position, for Perform signal processing and conditioning to obtain initial values for rotor initial position estimation for coordinate transformation

Step 4: Continue at Inject a number of high-frequency cosine voltage signals U _h cosω _h t of a certain period into the axis, and detect the sampled A and B two-phase winding current signals _{ia and i b together} with the estimated position Carry out the coordinate transformation to get Axial current

Step 5: Match the obtained Axial current Integrate to get the integral value

Step 6: Pass Judgment To determine the polarity of the magnetic poles and the initial position of the rotor: if is positive, the positive direction of the magnetic pole is consistent with the positive direction of the injected voltage, and the initial position of the rotor if is negative, the positive direction of the magnetic pole is opposite to the positive direction of the injected voltage, and the initial position of the rotor So far, the detection and identification of the initial position of the rotor is completed.

The beneficial effect of the present invention is that: the sensorless permanent magnet synchronous motor initial position detection method does not need to know the motor parameters, effectively avoiding the problems of the existing rotor initial position detection method that may cause the motor to rotate and identify signal detection difficulties , no need to add hardware, easy to implement, and realize accurate acquisition of the initial position of any rotor magnetic pole in the static state of the motor.

Description of drawings

Figure 1 is a physical model diagram of a permanent magnet synchronous motor in a synchronous rotating coordinate system.

Fig. 2 is a schematic diagram of the magnetic polarity detection of the present invention.

Fig. 3 is a flowchart of the method of the present invention.

detailed description

Below in conjunction with Fig. 1 to Fig. 3 illustrate the specific embodiment of the present invention, this embodiment comprises the following steps:

Step 1: As shown in Figure 1, the physical model of the permanent magnet synchronous motor in the synchronous rotating coordinate system, define the actual angle as θ and the estimated angle as And lagging behind θ, the estimated angle error is Δθ, the actual direct axis is the d axis, the actual quadrature axis is the q axis, and the estimated direct axis is axis, the estimated intersection axis is axis, the actual synchronous rotating coordinate system is dq, and the estimated synchronous rotating coordinate system is Then, under the condition that the motor is in a static state, open-loop control is performed on the current to initialize the initial position of the rotor, that is, an initial position of the rotor is arbitrarily assumed first.

Step 2: as shown in the flowchart of the method of the present invention in Fig. 3, in The shaft injects a continuous high-frequency cosine voltage signal The subscript h represents the high-frequency component, U _h is the amplitude of the injected high-frequency signal, ω _h is the angular frequency of the injected high-frequency signal, and t is time. Carry out coordinate transformation on the detected and sampled A and _B two-phase winding current signals _ia and ib to extract and estimate the high-frequency quadrature-axis current, that is, Axial current high frequency response in

In the formula, ΔL=(L _d -L _q )/2, L _d and L _q are d and q axis inductance, |Z _d |, |Z _q | are the modulus of d and q axis impedance, its corresponding phase angle. It can be seen from formula (1), The shaft high-frequency current changes sinusoidally within one cycle, and the average torque generated by it is zero, and the current cycle is much smaller than the mechanical time constant of the motor, so it will not cause the motor to rotate.

Step 3: Due to the obtained Axial current high frequency response in Contains signals related to rotor position, for for signal processing and conditioning, the Multiplied by sinω _h t and passed through a low-pass filter (LPF), the following error signal f _Δθ can be obtained:

In the formula, Δθ is the position error value. When the frequency of the injected signal satisfies ω _h >R _s /L _d , R _s is the stator resistance, which can make k>0.

When the position error value Δθ is small, f _Δθ is approximately proportional to Δθ. If f _Δθ can be adjusted to approach zero, the estimated value of the rotor position will converge to the actual value θ. In the method of the present invention, f _Δθ is adjusted by an integral regulator to obtain the initial value of position estimation

However, it can be seen from formula (2) that when Δθ is equal to 0, π/2, π or 3π/2, f _Δθ is zero, and the regulation system is in a steady state at this time. And only when Δθ=0, The remaining three cases must therefore be ruled out. do this first The convergence characteristic analysis of , where the initial value of the initial estimated angle is set to zero, that is Taking the actual position of the motor rotor at (0, π/2) as an example, since k>0, formula (2) shows that f _Δθ >0, under the adjustment of the regulator gradually increases, and will eventually converge to the actual position θ; similarly, according to the above derivation process, it can be obtained that the actual position is in other intervals and boundary values The convergence value of is shown in Figure 2, where the dotted line is the actual position θ, and the solid line is the estimated position

It can be seen from Figure 2 that: There are two types of relationships between the convergence value of and θ:

(1) If The convergence value is 0, then θ=0, π/2, π or 3π/2;

(2) If The convergence value is not 0, then or

For the first type of situation, a special location judgment is required. The specific method is as follows: Take the actual position of the motor rotor as 0 as an example, set the special position judgment time T, if the estimation algorithm runs to the time T is still zero (or less than a certain threshold θ _t ), it indicates that the motor rotor is in (or close to) the four special positions of 0, π/2, π or 3π/2. value, it may be set to π/4, taking the motor rotor actually at 0 as an example, at this time f _Δθ <0, then after the function of the regulation system, gradually decreases, and finally converges to 0; similarly, the other three convergence situations can be deduced as shown in Table 1. So far all the results can be unified as or Only need to judge the magnetic polarity again.

Table 1 Convergence characteristics of special position judgment

Due to the saturated salient pole characteristics of the motor, when the injected voltage direction is consistent with the positive direction of the magnetic pole polarity, the current response value generated is larger than the current response value generated when it is opposite, so that the magnetic pole polarity can be judged.

Step 4: According to step 3, obtain the initial value of the rotor initial position estimation for coordinate transformation After that, continue at Inject several (assumed 10) high-frequency cosine voltage signals U _h cosω _h t of a certain period into the axis, and detect the sampled A and B two-phase winding current signals i _a and i _b together with the estimated position Carry out the coordinate transformation to get Axial current

Step 5: Match the obtained Axial current Integrate to get the integral value

Step 6: Pass Judgment To determine the polarity of the magnetic poles and the initial position of the rotor: if is positive, that is Then the positive direction of the magnetic pole is consistent with the positive direction of the injected voltage, and the initial position of the rotor if is negative, ie Then the positive direction of the magnetic pole is opposite to the positive direction of the injected voltage, and the initial position of the rotor So far, the detection and identification of the initial position of the rotor is completed.

The protection scope of the present invention covers all the variants described above.

Claims (1)

1. the permagnetic synchronous motor initial position detection method of a position-sensor-free, it is characterised in that under the method includes State step:

Step 1: definition actual angle is θ, estimated angle isAnd lag behind θ, estimate angular error be Δ θ, actual d-axis be d Axle, actual quadrature axis be q axle, estimation d-axis beAxle, estimation quadrature axis areAxle, actual synchronization rotating coordinate system are d-q, estimation same Step rotating coordinate system isThen under ensureing motor resting state, electric current is carried out opened loop control, initialize rotor initial Position, i.e. first arbitrarily assumes an initial position of rotor；

Step 2:Axle injects lasting high-frequency cosine voltage signal, the most givenShaft voltage isWherein subscript H represents high fdrequency component, U_hFor injecting the amplitude of high-frequency signal, ω_hFor injecting the angular frequency of high-frequency signal, t is the time；Will detection A, B biphase winding current signal i sampled_a、i_bCarry out coordinate transform, obtainShaft currentIn high frequency response

Step 3: due to obtainShaft currentIn high frequency responseComprise the signal relevant to rotor-position, rightCarry out letter Number process and regulation obtain for coordinate transform initial position of rotor estimation initial value

Step 4: continueAxle injects several high-frequency cosine voltage signal U determining the cycle_hcosω_hT, samples detection A, B biphase winding current signal i_a、i_bWith the estimated position obtainedCarry out coordinate transform, obtainShaft current

Step 5: to obtainShaft currentIt is integrated, obtains integrated value

Step 6: by judgingPositive and negative determine pole polarity and initial position of rotor: ifFor just, then magnetic pole is square To consistent with injecting voltage forward, its initial position of rotorIfBe negative, then magnetic pole positive direction is with injecting voltage just To on the contrary, its initial position of rotorThe most i.e. complete detection and the identification of initial position of rotor.