METHOD FOR SEARCHING MTPA CURVE OF VEHICLE PERMANENT MAGNET SYNCHRONOUS MOTOR BASED ON DC POWER

Abstract

Disclosed is a method for searching a MTPA curve of a vehicle permanent magnet synchronous motor based on a DC power, which includes a current closed-loop adjuster, a current command generator, a current command angle generator, an active power calculator, an active power storage and comparison processor and a current given vector corrector. According to the present disclosure, the tedious manual calibration is relieved, the optimal angle is automatically searched, and the production efficiency is improved; according to the present disclosure, the step size can be arbitrarily set according to the calibration requirements, so as to achieve a higher calibration accuracy.

Claims

1. A method for searching a MTPA curve of a vehicle permanent magnet synchronous motor based on a DC power, comprising a current closed-loop adjuster, a current command generator, a current command angle generator, an active power calculator, an active power storage and comparison processor and a current given vector corrector; wherein an input of the current closed-loop adjuster is a dq current command output by the current given vector corrector, and the dq voltage command is output after passing through a proportional-integral controller; the current command generator is configured to gradually accumulate current amplitudes; the current angle generator is configured to gradually accumulate current angles; the active power calculator is configured to calculate a real-time active power; the active power storage and comparison processor is configured to store and compare the active power calculated by the active power calculator in a current step and a previous step in an angle accumulation process; if the active power increases after one step of current angle accumulation, the current angle accumulation is continued; and if the active power does not increase after one step of current angle accumulation, the current angle accumulation is stopped, and a current amplitude, a current angle of the previous step and a corresponding active power are output; according to the outputs of the current command generator and the current command angle generator, the current given vector corrector calculates dq current commands i.sub.dref and i.sub.qref. $\{\begin{array}{c}{i}_{qref}=I\left(j\right)\cos \left(\theta \left(k\right)\right)\\ i_{dref}=-I\left(j\right)\sin \left(\theta \left(k\right)\right)\end{array}$ where i(j) is the current amplitude, and j is for counting the number of steps for current amplitude accumulation; θ(k) is a current angle, and k is for counting the number of steps of angle accumulation; the method comprises that following specific steps: (1) starting from a current with a current of 0 A and an angle of 90°; (2) accumulating the current angle θ by the current command angle generator:
θ(k)=θ(k−1)+θ.sub.step (3) inputting, by the current command angle generator, the accumulated current angle into the current given vector corrector upon every step of current angle accumulation, and at the same time inputting, by the current command generator, the current amplitude into the current given vector corrector, and calculating, by the active power calculator, the active power P.sub.calcu(k) corresponding to one current step k; (4) repeating steps (2) to (3), accumulating current angles until the active power storage and comparison processor judge that the condition P.sub.calcu(k)−P.sub.calcu(k−1)≤0 is met, stopping current angle accumulation, and recording the current amplitude, the current angle 0(k−1) accumulated in the previous step and a corresponding active power P.sub.calcu(k−1) thereof as an available point; (5) accumulating, by the current command generator, the current amplitude I by taking the current amplitude as a starting point:
I(j)=I(j−1)+I.sub.step (6) repeating steps (2) to (5) until the current amplitude accumulated in step (5) reaches a maximum required current of the proportional-integral controller, stopping circulation, and outputting the available point recorded in step (4) for the current amplitude by each current command generator.

2. The method for searching a MTPA curve of a vehicle permanent magnet synchronous motor based on a DC power according to claim 1, wherein in the current closed-loop adjuster, the dq voltage command is obtained from an output of PI controllers, and inputs of the PI controllers are a deviation of the dq current command i.sub.dref, i.sub.qref and a dq current feedback, respectively.

3. The method for searching a MTPA curve of a vehicle permanent magnet synchronous motor based on a DC power according to claim 2, wherein the current command generator takes a current amplitude I=0A as a starting point and I.sub.step as a step length to accumulate the current amplitude I.

4. The method for searching a MTPA curve of a vehicle permanent magnet synchronous motor based on a DC power according to claim 3, wherein the current command angle generator takes 90° as a starting point and θ.sub.step as a step length to accumulate the current angle θ.

5. The method for searching a MTPA curve of a vehicle permanent magnet synchronous motor based on a DC power according to claim 4, wherein in the active power calculator, the real-time active power P.sub.calcu is:
P.sub.calcu=u.sub.di.sub.d+u.sub.qi.sub.q where i.sub.d and i.sub.q are d-axis and q-axis components of a measured current; u.sub.d and u.sub.q are d-axis and q-axis components of an inner loop observation voltage.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0044] FIG. 1 is a topology block diagram of flux weakening control in the related art.

[0045] FIG. 2 is a schematic diagram of variable calculation according to the present disclosure.

[0046] FIG. 3 is a logic main flow chart according to the present disclosure.

[0047] FIG. 4 is a schematic diagram of current angle search results.

DESCRIPTION OF EMBODIMENTS

[0048] The present disclosure relates to a method for searching a MTPA curve of a vehicle permanent magnet synchronous motor based on a DC power, which includes the following steps:

[0049] As shown in FIG. 2, the present disclosure includes the following modules:

[0050] 1. A current closed-loop adjuster: this part is the dependent module of the present disclosure, and its function is to obtain the dq voltage commands from the outputs of PI controllers, the inputs of PI controllers are the deviation of dq current commands i.sub.dref, i.sub.qref and the dq current feedback respectively.

[0051] 2. A current command generator: starting from I(0)=0A and taking I.sub.step as a step length to progressively increase the current vector size I, where A is the current unit of ampere.

[0052] 3. A current command angle generator: starting from θ(0)=90°, taking θ.sub.step as a step length to progressively increase the current angle θ.

[0053] 4. An active power calculator: calculating the real-time active power P.sub.calcu during the operation of the motor:

P.sub.calcu=u.sub.di.sub.d+u.sub.qi.sub.q

[0054] where i.sub.d and i.sub.q are measured stator d-axis and q-axis current; u.sub.d and u.sub.q are d-axis and q-axis components of the inner loop observation voltage, which are equal to v.sub.dqref in value; i.sub.d, i.sub.q, u.sub.d and u.sub.q are all sampled values.

[0055] 5. An active power storage and comparison processor: storing and comparing the active powers calculated by the active power calculator at the angles of the current step k and the previous step k−1; if P.sub.calcu(k)−P.sub.calcuk−1) is positive, continuing searching; if the difference is 0 or negative, stopping searching and outputting the result of the previous step as an available result, including the current amplitude, the current angle of the previous step and a corresponding active power.

[0056] 6. A current given vector corrector (sin/cos): calculating the current i.sub.dref, i.sub.qref of the d-axis and q-axis after magnetic weakening as follows according to the outputs of the current command generator and current command angle generator:

[00004]$\{\begin{array}{c}{i}_{qref}=I\left(j\right)\cos \left(\theta \left(k\right)\right)\\ i_{dref}=-I\left(j\right)\sin \left(\theta \left(k\right)\right)\end{array}$ [0057] where I(j) is the current amplitude and θ(k) is the current angle.

[0058] The workflow of that application is shown in FIG. 3, and includes:

[0059] (1) Starting from a current with a amplitude of 0A and an angle of 90°.

[0060] (2) Accumulating the current angle by the current command angle generator by taking θ step as a step length:

θ(k)=θ(k−1)+θ.sub.step

[0061] where k is used to count the steps for angle accumulation;

[0062] (3) inputting, by the current command angle generator, the accumulated current angle into the current given vector corrector upon every step of current angle accumulation, and at the same time inputting, by the current command generator, the current amplitude into the current given vector corrector, and calculating, by the active power calculator, the active power P.sub.calcu(k) corresponding to one current step k.

[0063] (4) Repeating steps (2) to (3), accumulating angles until the active power storage and comparison processor judges that the condition P.sub.calcu(k)−P.sub.calcu(k−1)≤0 is met, stopping current angle accumulation, and recording the current amplitude, the current angle θ(k−1) accumulated in the previous step and a corresponding active power P.sub.calcu(k−1) thereof as an available point, the current combination at this point corresponds to the maximum torque current.

[0064] (5) Accumulating, by the current command generator, the current amplitude I by taking I.sub.step as a step length:

I(j)=I(j−1)+I.sub.step

[0065] where j is used to count the steps for current amplitude accumulation.

[0066] (6) Repeating steps (2) to (5) until the current amplitude accumulated in step (5) reaches the maximum required current of the proportional-integral controller, stopping circulation, and outputting the available point recorded for each current amplitude by each current command generator. In this embodiment, the current angle search results with a step length I.sub.step of 100 A starting from 100 A to 600 A are shown in FIG. 4.