A permanent magnet synchronous motor overmodulation method taking into account amplitude adjustment

Abstract

The present invention discloses a permanent magnet synchronous motor overmodulation method taking into account amplitude adjustment. For a three-phase permanent magnet synchronous motor, firstly, according to the dq axis current reference value i d ref 、i q ref Determine the dq axis predicted voltage reference value v d ref 、v q ref ; Then according to the predicted voltage reference value v d ref 、v q ref Determine the modulation area; then obtain a new dq axis current reference value i according to the modulation area d‑limit 、i q‑limit , construct a new predictive control value function, filter the voltage vector; finally get the inverter drive signal. This method only needs to obtain the dq axis current reference value to achieve overmodulation control, avoid complex angle and amplitude calculations, simple calculation, and easy operation.

Description

Technical Field

[0001] The invention relates to an overmodulation method taking amplitude adjustment into account, and belongs to the field of motor drive and control. Background Art

[0002] Permanent magnet synchronous motor (PMSM) has the advantages of low loss, high efficiency, and significant power saving, so it is widely used in the field of electric vehicles. The development of power electronics technology, microelectronics technology, computer technology and other technologies has given new vitality to the motor system, and motor control technology has also received widespread attention. The application environment of new energy vehicles is very different from that of industrial applications, so there are higher requirements for the safety, stability and control effect of motor control. High power density is one of the development directions of new energy motor controllers. Using overmodulation methods to improve voltage utilization is an effective means to improve power density.

[0003] Traditional SVPWM overmodulation methods mainly include phase following method and amplitude following method. Both methods need to calculate the real-time reference voltage vector phase information, so as to adjust the reference voltage vector phase or amplitude according to the phase information. These two methods have complex algorithms, large amount of calculation, long calculation time, high hardware requirements, and will lead to an increase in current harmonic content. Summary of the invention

[0004] Technical problem: In view of the above-mentioned existing technologies, a permanent magnet synchronous motor overmodulation method taking into account amplitude adjustment is proposed. While simplifying the overmodulation control algorithm, it can effectively reduce the current harmonic content and improve the overmodulation performance of the permanent magnet synchronous motor system.

[0005] Technical solution: A permanent magnet synchronous motor overmodulation method taking into account amplitude adjustment, comprising:

[0006] Step 1: Collect the three-phase current i of the motor a 、i b 、i c And get the motor electrical angle θ e and electrical angular velocity ω e , use Clark / Park transformation to calculate the current stator current dq axis component i d (k) and i q (k);

[0007] Step 2: Given the d-axis reference current i d ref =0, collect the error signal between the given speed and the measured speed, and obtain the q-axis reference current i through the PI controller q ref ;

[0008] Step 3: From the dq axis current reference value i d ref 、i q ref Determine the dq axis predicted voltage reference value v d ref 、v q ref ;

[0009] Step 4: Determine the modulation area according to the reference voltage vector amplitude;

[0010] Step 5: Determine the dq axis current reference value according to the modulation area;

[0011] Step 6: Construct a new predictive control value function according to the modulation area and select the voltage vector;

[0012] Step 7: Calculate the duty cycle of each voltage vector to obtain the inverter drive signal.

[0013] Furthermore, in step 3, the dq axis predicted voltage reference value v is calculated by equation (1): d ref 、v q ref ;

[0014]

[0015] In the formula, i d (k), i q (k) are the d-axis and q-axis currents at the current sampling moment; R is the stator resistance; ω e is the electrical angular velocity; L d , L q are the d-axis and q-axis inductance values ​​respectively; T s is the sampling period; ψ f is the permanent magnet flux.

[0016] Furthermore, in step 4, the reference voltage vector amplitude v is calculated by equation (2): ref , when v ref ≤(V dc / 1.732), the motor runs in the linear region. ref >(V dc / 1.732), the motor operates in the overmodulation area;

[0017]

[0018] Among them, V dc is the inverter DC bus voltage.

[0019] Furthermore, in step 5, when the motor is running in the linear region, the dq axis current reference value i is retained.d ref 、i q ref When the motor runs in the overmodulation region, the new dq axis current reference value i is calculated by formula (3): d-limit 、i q-limit ;

[0020]

[0021] In the formula, i d (k), i q (k) are the d-axis and q-axis currents at the current sampling moment; R is the stator resistance; ω e is the electrical angular velocity; L d , L q are the d-axis and q-axis inductance values ​​respectively; T s is the sampling period; ψ f is the permanent magnet flux.

[0022] Furthermore, in step 6, the eight basic voltage vectors of the inverter are substituted into equation (4) to obtain the corresponding dq axis predicted current value i d (k+1) and i q (k+1), when the motor runs in the linear region, a value function as shown in formula (5) is constructed, and the optimal vector and the suboptimal vector are selected by formula (5); when the motor runs in the overmodulation region, a value function as shown in formula (6) is constructed, and the optimal vector and the suboptimal vector are selected by formula (6);

[0023]

[0024] g=|i d ref -i d (k+1)|+|i q ref -i q (k+1)| (5)

[0025] g=|i d-limit -i d (k+1)|+|i q-limit -i q (k+1)| (6)

[0026] In the formula, i d (k), i q (k) are the d-axis and q-axis currents at the current sampling moment; R is the stator resistance; ω e is the electrical angular velocity; L d , L q are the d-axis and q-axis inductance values ​​respectively; T s is the sampling period; ud (k) and u q (k) are the voltage vector d and q axis voltage values ​​at the current sampling time, ψ f is the permanent magnet flux.

[0027] Beneficial effects: 1) constructing a value function of the object controlled by the dq axis current reference value, which facilitates the optimal control of the linear region and the overmodulation region;

[0028] 2) The dq axis current reference value in the overmodulation region is determined by a simple formula, which greatly reduces the amount of calculation for amplitude adjustment;

[0029] 3) The dq reference current value adjusted with the modulation area is used as the controlled object, which is simple to calculate and easy to transplant into motor control algorithms such as model prediction and SVPWM. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A control block diagram of a permanent magnet synchronous motor overmodulation method taking into account amplitude adjustment of the present invention, wherein 1-modulation partition module, 2-amplitude adjustment module, 3-vector screening module, 4-action time module, 5-current prediction module, 6-Clark / Park conversion module and 7-rotor position and speed detection module;

[0031] Figure 2 A voltage vector diagram of a permanent magnet synchronous motor overmodulation method taking amplitude adjustment into account according to the present invention;

[0032] Figure 3 This is a comparative simulation diagram without using the overmodulation algorithm;

[0033] Figure 4 This is a simulation diagram of a permanent magnet synchronous motor overmodulation method taking into account amplitude adjustment according to the present invention. DETAILED DESCRIPTION

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and by way of examples. The following examples are intended to explain the present invention but the present invention is not limited to the following examples.

[0035] A permanent magnet synchronous motor overmodulation method taking into account amplitude adjustment comprises the following steps:

[0036] Step 1: Collect the three-phase current i of the motor a 、i b 、i c And get the motor electrical angle θ e and electrical angular velocity ω e , use Clark / Park transformation to calculate the current stator current dq axis component i d (k) and i q (k);

[0037] Step 2: Given the d-axis reference current i d ref =0, collect the error signal between the given speed and the measured speed, and obtain the q-axis reference current i through the PI controller q ref ;

[0038] Step 3: Calculate the dq axis predicted voltage reference value v by equation (1) d ref 、v q ref ;

[0039]

[0040] In the formula, i d (k), i q (k) are the d-axis and q-axis currents at the current sampling moment; R is the stator resistance; ω e is the electrical angular velocity; L d , L q are the d-axis and q-axis inductance values ​​respectively; T s is the sampling period; ψ f is the permanent magnet flux.

[0041] Step 4: Calculate the reference voltage vector amplitude v by equation (2) ref , when v ref ≤(V dc / 1.732), the motor runs in the linear region. ref >(V dc / 1.732), the motor runs in the overmodulation area, V dc is the inverter DC bus voltage;

[0042]

[0043] Step 5: When the motor runs in the linear region, keep the dq axis current reference value i d ref 、i q ref When the motor runs in the overmodulation region, the new dq axis current reference value i is calculated by formula (3): d-limit 、i q-limit ;

[0044]

[0045] Step 6: Substitute the eight basic voltage vectors of the inverter into equation (4) to obtain the corresponding dq axis predicted current value i d (k+1) and i q(k+1), when the motor runs in the linear region, a value function as shown in formula (5) is constructed, and the optimal vector and the suboptimal vector are selected by formula (5); when the motor runs in the overmodulation region, a value function as shown in formula (6) is constructed, and the optimal vector and the suboptimal vector are selected by formula (6);

[0046]

[0047] g=|i d ref -i d (k+1)|+|i q ref -i q (k+1)| (5)

[0048] g=|i d-limit -i d (k+1)|+|i q-limit -i q (k+1)| (6)

[0049] In the formula, i d (k), i q (k) are the d-axis and q-axis currents at the current sampling moment; R is the stator resistance; ω e is the electrical angular velocity; L d , L q are the d-axis and q-axis inductance values ​​respectively; T s is the sampling period; u d (k) and u q (k) are the voltage vector d and q axis voltage values ​​at the current sampling time, ψ f is the permanent magnet flux.

[0050] Step 7: Use the traditional three-vector model predictive current control method to calculate the duty cycle of each voltage vector and obtain the inverter drive signal.

[0051] An overmodulation method taking amplitude adjustment into account disclosed by the present invention is implemented under the condition of a DC bus voltage of 100V.

[0052] The variable speed dynamic simulation is carried out under the condition that the load torque is 5N·m and the speed suddenly changes from 360r / min to 385r / min in 0.5s. The variable speed dynamic simulation results are shown in Figure 3 and Figure 4 shown. Figure 3 The comparison simulation diagram without overmodulation algorithm is shown in Figure 1, where (a) represents the phase current and (b) represents the speed. Figure 3It can be seen that within 0 to 0.5s, the speed is stable, the three-phase current has high sinusoidality and low harmonic content; after 0.5s, the speed fluctuates and cannot be maintained steadily at the given speed of 385r / min, and the current distortion is large. This is because the voltage output by the inverter at this time cannot reach the voltage required for the motor to run at a speed of 385r / min. Figure 4 This is a simulation diagram of an overmodulation method taking into account amplitude adjustment of the present invention, where (a) represents the phase current and (b) represents the speed. Figure 4 It can be seen that after 0.5s, the speed can reach the given speed of 385r / min and remain stable, and the three-phase current still maintains a good sinusoidal degree and relatively less harmonic content. Figure 3 and Figure 4 It can be seen that the proposed overmodulation algorithm can expand the motor speed and improve the DC bus voltage utilization.

[0053] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A permanent magnet synchronous motor overmodulation method taking into account amplitude adjustment, characterized in that: include: Step 1: Collect the three-phase current i of the motor a 、i b 、i c And get the motor electrical angle θ e and electrical angular velocity ω e , use Clark / Park transformation to calculate the current stator current dq axis component i d (k) and i q (k); Step 2: Given the d-axis reference current i d ref =0, collect the error signal between the given speed and the measured speed, and obtain the q-axis reference current i through the PI controller q ref ; Step 3: From the dq axis current reference value i d ref 、i q ref Determine the dq axis predicted voltage reference value v d ref 、v q ref ; Step 4: Determine the modulation area according to the reference voltage vector amplitude; Step 5: Determine the dq axis current reference value according to the modulation area; Step 6: Construct a new predictive control value function according to the modulation area and select the voltage vector; Step 7: Calculate the duty cycle of each voltage vector to obtain the inverter drive signal; In step 3, the dq axis predicted voltage reference value v is calculated by formula (1): d ref 、v q ref ; In the formula, i d (k), i q (k) are the d-axis and q-axis currents at the current sampling moment; R is the stator resistance; ω e is the electrical angular velocity; L d , L q are the d-axis and q-axis inductance values ​​respectively; T s is the sampling period; ψ f is the permanent magnet flux; In step 4, the reference voltage vector amplitude v is calculated by equation (2): ref , when v ref ≤(V dc / 1.732), the motor runs in the linear region. ref >(V dc / 1.732), the motor operates in the overmodulation area; Among them, V dc is the inverter DC bus voltage; In step 5, when the motor runs in the linear region, the dq axis current reference value i is retained. d ref 、i q ref When the motor runs in the overmodulation region, the new dq axis current reference value i is calculated by formula (3): d-limit 、i q-limit ; In the formula, i d (k), i q (k) are the d-axis and q-axis currents at the current sampling moment; R is the stator resistance; ω e is the electrical angular velocity; L d , L q are the d-axis and q-axis inductance values ​​respectively; T s is the sampling period; ψ f is the permanent magnet flux; In step 6, the eight basic voltage vectors of the inverter are respectively substituted into equation (4), and the corresponding dq axis predicted current values ​​i are obtained. d (k+1) and i q (k+1), when the motor runs in the linear region, a value function as shown in formula (5) is constructed, and the optimal vector and the suboptimal vector are selected by formula (5); when the motor runs in the overmodulation region, a value function as shown in formula (6) is constructed, and the optimal vector and the suboptimal vector are selected by formula (6); g=|i d ref -i d (k+1)|+|i q ref -i q (k+1)| (5) g=|i d-limit -i d (k+1)|+|i q-limit -i q (k+1)| (6) In the formula, i d (k), i q (k) are the d-axis and q-axis currents at the current sampling moment; R is the stator resistance; ω e is the electrical angular velocity; L d , L q are the d-axis and q-axis inductance values ​​respectively; T s is the sampling period; u d (k),u q (k) are the voltage vector d and q axis voltage values ​​at the current sampling time, ψ f is the permanent magnet flux.

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