CN113078860A - Seven-phase permanent magnet synchronous motor rotating speed rapid control algorithm - Google Patents

Abstract

The invention discloses a seven-phase permanent magnet synchronous motor rotating speed rapid control algorithm, which comprises the following steps: acquiring the output quantity of the seven-phase permanent magnet synchronous motor, and taking the output quantity and the prediction reference current as the input quantity of a prediction model; equally dividing the space into a plurality of sectors, wherein each sector has an optimal voltage vector; obtaining a voltage predicted value on the current time space through calculation of a prediction model, taking the voltage predicted value as the input of a sector judgment link, and judging the sector number of the current predicted voltage; outputting the optimal voltage vector in the corresponding sector as the optimal voltage vector at the current moment; calculating a pulse sequence required by a seven-phase voltage source inverter for synthesizing the current optimal voltage vector according to a space vector pulse width modulation principle; and applying the synthesized pulse sequence to the voltage source inverter. The invention ensures the rapidity of the speed regulation of the seven-phase permanent magnet synchronous motor and improves the quality of the input electric energy.

Description

A Fast Speed Control Algorithm for Seven-Phase Permanent Magnet Synchronous Motor

technical field

The invention relates to the field of control algorithms, in particular to a fast speed control algorithm of a seven-phase permanent magnet synchronous motor.

Background technique

With the development of science and technology, the traditional three cameras are widely used in various fields. In the shipbuilding industry, traditional three-phase motors are mainly used. Recently, the use of three-phase or more (such as seven-phase) motors has greatly increased, especially in high-power applications such as ship propulsion. The seven-phase motor has the advantages of high power density, high torque-to-inertia ratio, and high efficiency, as well as small torque ripple and high reliability.

The multi-camera is powered by a multi-phase voltage source inverter (voltage source inverter), and in order to drive the multi-phase voltage source inverter, space vector pulse width modulation (SVPWM), direct torque control (DTC), field Modulation and control schemes such as Oriented Control (FOC) and Model Predictive Control (MPC). Due to its simple and intuitive concept, fast dynamic response, flexible control, and its use of an optimization framework that can combine various nonlinear and practical constraints, MPCC is considered to be the most effective and simplest current control for multiphase voltage source inverters one of the options. However, when a multi-phase power system is powered by a multi-phase PWM inverter, a large amount of harmonic currents will be generated, resulting in degraded control performance.

Most modern ships use electric propulsion systems. The electric propulsion system has the advantages of environmental protection, strong controllability, good speed regulation characteristics, and no need to configure traditional reduction gearboxes. The speed control of the propulsion motor is one of the important indicators to measure the performance of the ship's power system, and the speed regulation performance is affected by the controlled object and the complexity of the system. The traditional double closed-loop control of the motor uses two PI regulators to control the speed loop and the current loop respectively. The adjustment of the parameters of the PI regulator is a troublesome problem. First, the entire system needs to be mathematically modeled to adjust the parameters through the transfer function of each part. Increase the complexity of the system. Moreover, unreasonable parameters will greatly affect the speed of speed adjustment and the dynamic performance of the system.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a seven-phase permanent magnet synchronous motor speed fast control algorithm, which can solve the dynamic performance of seven-phase permanent magnet synchronous motor speed regulation, optimize power quality and PI regulator parameter setting problems.

In order to achieve the above purpose, the technical solution of the present invention is as follows: a seven-phase permanent magnet synchronous motor speed control algorithm, comprising the following steps:

Step 1: Obtain the output of the seven-phase permanent magnet synchronous motor, and use it and the predicted reference current as the input of the MPCC prediction model;

Step 2: Divide the space into several sectors, and each sector has an optimal voltage vector;

Step 3: Through the calculation of the MPCC prediction model, the voltage prediction value in the space at the current moment is obtained, and it is used as the input of the sector judgment link composed of the adder, the divider, the remainder operation and the limiter, and the current prediction value is judged. The sector number where the voltage is located;

Step 4: output the sector number where the current predicted voltage is located, and match with several sectors, output the optimal voltage vector in the corresponding sector, and use it as the optimal voltage vector at the current moment;

Step 5: Calculate the pulse sequence required by the seven-phase voltage source inverter to synthesize the current optimal voltage vector according to the principle of space vector pulse width modulation;

Step 6: Apply the synthesized pulse sequence to the voltage source inverter to invert the DC voltage to the current required seven-phase voltage.

Wherein, the output of the motor includes α-β space stator current, rotor angle, and rotor speed.

Wherein, the predicted reference current is provided by the outer loop rotational speed PI regulator.

Wherein, the prediction model of the MPCC is based on the load. Different load models have different mathematical models and different prediction models in the continuous state.

Further, the fast speed control algorithm of the seven-phase permanent magnet synchronous motor is characterized in that, the optimal vector for prediction needs to be calculated within a sampling period through a discrete mathematical model, and the discrete mathematical model is obtained through the previous calculation. It is obtained by discretizing the mathematical model in the continuous state by the Euler method in the sampling period. Due to the difference of the load, the mathematical model in the continuous state is also different, and the prediction model is also different, then it predicts the position and value of the voltage vector. The size is also different, that is, the output of the prediction model determines the optimal vector for prediction.

Each of the optimal voltage vectors is synthesized by five basic voltage vectors, and under the condition of ensuring the minimum common mode current and harmonic suppression, the seven-phase voltage source inverter bridge arm switch synthesis of each optimal voltage vector is obtained sequence.

Further, when synthesizing the pulse sequence required by the seven-phase voltage source inverter of the current optimal voltage vector, it is necessary to synthesize the continuous turn-on pulse of the lower cliff first, and then combine the judgment of the current sector to output the intermittent turn-on bridge arm pulse. The reverse sequence of the sequence.

Compared with the prior art, the present invention has the following significant advantages and effects:

1. The present invention ensures the rapidity of the speed adjustment of the seven-phase permanent magnet synchronous motor and improves the quality of the input power, avoids that the system is too complicated to calculate the algorithm, increases the calculation time, reduces the real-time performance of the voltage source inverter, and causes The seven-phase permanent magnet synchronous motor cannot be quickly and accurately adjusted to the given value, and even causes the seven-phase permanent magnet synchronous motor to lose steps.

2. The present invention optimizes the input voltage power quality of the seven-phase permanent magnet synchronous motor, especially reduces the generation of a large number of low-order harmonics, which greatly reduces the harmonics caused by the voltage source inverter and the seven-phase permanent magnet synchronous motor. resulting in additional losses.

3. The SVPWM is introduced in the present invention, which makes the control system easier to realize digitization, and the control system has only one speed PI regulator, which greatly reduces the complexity of parameter setting of the system PI regulator compared with the traditional double PI regulator.

Description of drawings

Fig. 1 is the control algorithm principle block diagram in the present invention;

Fig. 2 is the sector judging module in the present invention;

Fig. 3 is the schematic diagram of the plane of static α-β coordinate system in the present invention;

Fig. 4 is the distribution diagram of basic voltage vector in α-β space in the present invention;

Fig. 5 is the spatial distribution diagram of basic voltage vector in x ₁ -y ₁ in the present invention;

Fig. 6 is the basic voltage vector in the present invention in x ₂ -y ₂ spatial distribution diagram;

7 is a composite diagram of the voltage vector V ₂ in the present invention;

8 is a composite diagram of the optimal voltage vector V ₂ in the present invention;

Fig. ₉ is the pulse timing diagram of the optimal voltage vector V2 in the present invention;

10 is a schematic diagram of the pulse timing adjustment module of the optimal voltage vector V ₂ in the present invention;

11 is a control effect diagram of the present invention applied to a seven-phase permanent magnet synchronous motor control system;

FIG. 12 is the result of applying the present invention to the seven-phase permanent magnet synchronous electric harmonic suppression.

Detailed ways

The technical content, structural features, achieved objects and effects of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in Figure 1, it is a principle block diagram of a seven-phase permanent magnet synchronous motor speed control algorithm provided by the present invention, the present invention takes seven-phase permanent magnet synchronous motor as an example, first builds its mathematical model, and solves the prediction according to the mathematical model Model.

The prediction model is constructed by a seven-phase permanent magnet synchronous motor. As shown in Figure 3, the stationary α-β coordinate system is flat. The α-β coordinate system is not the same rotating coordinate system as the motor speed. α represents the α axis and β represents the β axis. .

The output of the motor includes α-β space stator current (i), rotor angle (θ), and rotor speed (ω).

Further, the outer-loop speed PI regulator provides a predicted reference current.

As shown in Figure 2, the motor output and the predicted reference current will be used as the feedback for the input of the prediction model of the MPCC algorithm.

As shown in FIG. 4 , according to the combination of the seven bridge arms of the seven-phase voltage source inverter, a total of 2 ⁷ =128 voltage vectors in the α-β space can be obtained.

Further, as shown in Fig. 5 and Fig. 6, in the third harmonic space x ₁ -y ₁ and the fifth harmonic space x ₂ -y ₂ , there are also 128 voltage vectors respectively, and the synthesis method is as shown in formula (1)

V_dc为电压源逆变器直流侧电压，S为各桥臂上桥的开关状态(0(关闭)或1(开通))，128个电压矢量的编号是通过桥臂的开关状态按A-G相进行排序的唯一二进制码，如电压矢量V₂，为A-G相开关信号为0000010，即F相上桥臂开关接通，其他桥臂开关全部断开下的输出电压矢量。in,

V _dc is the DC side voltage of the voltage source inverter, S is the switch state of the bridge on each bridge arm (0 (closed) or 1 (open)), and the number of the 128 voltage vectors is the switch state of the bridge arm according to the AG phase The unique binary code for sorting, such as the voltage vector V ₂ , is the output voltage vector when the AG-phase switch signal is 0000010, that is, the F-phase upper arm switch is turned on and all other bridge arm switches are turned off.

As shown in Figure 3, by dividing the α-β space into 14 equal parts, each part is a sector, there are 14 sectors in total, and each sector has an optimal voltage vector.

Among them, as shown in FIG. 4 , the optimal voltage vector is the outermost voltage vector with the largest amplitude of the α-β space voltage vector. When the outermost voltage acts on the voltage source inverter, the common mode voltage formed between the neutral point of the inverter DC side and the center point of the motor stator winding is the smallest, which has the purpose of reducing the motor loss.

Through the calculation of the prediction model, the voltage prediction value in the α-β space at the current moment is obtained. Specifically, the voltage prediction value is a voltage vector including its amplitude and position information in the α-β space. Since the predicted voltage does not have the effect of suppressing harmonics and reducing the common-mode voltage, the predicted voltage is used as the input of the sector judgment link composed of the adder, the divider, the remainder operation and the limiter, and the current Sector judgment of the predicted voltage, output the sector number where the current predicted voltage is located, and match with 14 sectors, output the optimal voltage vector in the corresponding sector, and use it as the optimal voltage vector at the current moment.

Each optimal voltage vector is synthesized by 5 basic voltage vectors. Under the condition of ensuring the minimum common mode current and harmonic suppression, the bridge arm switching sequence of each optimal voltage vector is obtained.

According to the principle of SVPWM (space vector pulse width modulation), the pulse sequence required by the seven-phase voltage source inverter to synthesize the current optimal voltage vector is calculated.

Specifically, since some of the bridge arm switches are turned on intermittently, when synthesizing such bridge arm pulses, it is necessary to synthesize the continuous turn-on pulses of the lower cliff first, and then combine the judgment of the current sector to output the intermittent turn-on bridge arm pulses. The reverse sequence of the sequence.

Finally, the synthesized pulse sequence is applied to the voltage source inverter to invert the DC voltage to the seven-phase voltage currently required.

Ideally, the mathematical model of the motor's voltage in the α-β space is shown in equation (2):

为定子在α-β空间的电阻矩阵，

为定子在α-β空间的电感矩阵，

为永磁体在α-β空间上的磁链分量。Among them, μ _αβ is the stator voltage vector in the α-β space, i _αβ is the stator current vector in the α-β space,

is the resistance matrix of the stator in α-β space,

is the inductance matrix of the stator in α-β space,

is the flux linkage component of the permanent magnet in α-β space.

Specifically, the prediction model of MPCC is based on the load. Different load models have different prediction models. As shown in formula (2), if the load is an induction heating power supply, its model is in the form of an RLC series or parallel load.

According to formula (1), taking the current as the state quantity, it can be transformed into:

A, B, C, G, H, and M are the prediction model coefficient matrix of the seven-phase permanent magnet synchronous motor, where A=-(L _αβ ) ^-1 R _αβ , B=(L _αβ ) ^-1 , C=-( L _αβ ) ^-1 Φ(θ)

If T _s is too large, the prediction will be incorrect. If T _s is too small, the prediction will be too sensitive and the predicted output will be unstable, resulting in a large number of harmonics in the motor input voltage. According to the simulation analysis, the value of T _s in this algorithm is T _s = 4×10 ^-5 s, within this sampling time T _s , Equation (3) is linearized by the forward Euler method to obtain Equation (4):

i _αβ (k+1)=Gi _αβ (k)+Hu _αβ (k)+M(k)………………(4)

Wherein, G=(1+A)T _s , H=BT _s M=CT _s

In the process of hardware implementation, due to the limited operation speed of the single-chip microcomputer, the large amount of operation of the model predictive control will lead to the delay of the optimal voltage vector output. To solve this problem, the two-step forecasting method is usually applied to the model predictive control link.

By advancing equation (4) by one sampling period, the value of the predicted current at time (k+2) can be obtained. At this time, the prediction model of MPCC is shown in equation (5):

为α-β坐标系下由预测模型预测的下一时刻七相永磁同步电机定子相电压矢量，

为α-β坐标系下由电流环给定的参考七相永磁同步电机定子电流矢量，H^-1为系数矩阵H的逆矩阵。in,

is the stator phase voltage vector of the seven-phase permanent magnet synchronous motor at the next moment predicted by the prediction model in the α-β coordinate system,

is the reference seven-phase permanent magnet synchronous motor stator current vector given by the current loop in the α-β coordinate system, and H ^-1 is the inverse matrix of the coefficient matrix H.

Specifically, the optimal vector for prediction needs to be calculated within a sampling period through a discretized mathematical model, and the discretized mathematical model is obtained by discretizing the mathematical model in a continuous state through the forward Euler method within the sampling period .

Due to the difference of the load, the mathematical model in the continuous state is also different, the coefficient matrix in the prediction model is different, or the prediction model itself is different from the form of equation (5), the position and size of the predicted voltage vector are also different, that is, The output of the prediction model determines the optimal vector for prediction.

Figure 2 shows the sector judgment module. As shown in Figure 2, the angle of the output voltage vector of the prediction model is used as the input, and π/14 is added to adjust the sector to make it symmetrical about the X-axis. Divide π/7 to calculate the The vector occupies the number of a sector, and the plane is divided into 14 sectors. After dividing by 14, add 1 to get the position of the sector where the vector is located.

The construction of virtual voltage vector is the core content of the present invention. As shown in Figures 4 to 6, there are 128 cases of switch combinations of 7 bridge arms, that is, 128 basic voltage vectors. Among these basic voltage vectors, the modulo value is the largest. When the outermost voltage vector acts on the voltage source inverter, the generated common mode current is the smallest. Therefore, the present invention uses the outermost basic voltage vector as the basic voltage vector for constructing the virtual voltage vector.

Taking the virtual voltage vector V ₂ as an example, it is composed of basic voltage vectors 113, 97, 112, 99 and 120. As shown in Figure 7, it is a composite diagram of the virtual voltage vector V ₂ in three subspaces, as shown in formula (6) Shown is the composite expression of the virtual voltage vector V2.

In order to suppress harmonics, the virtual voltage vector in other spaces is zero. Under this constraint, the calculation of time factors t ₁ , t ₂ and t ₃ is shown in equation (7):

Solving equation (7), it can be obtained: t ₁ =0.198062; t ₂ =0.158834; t ₃ =0.286208. Bringing t ₁ , t ₂ , and t ₃ into formula (6) can obtain the composite graph of the optimal vector in V ₂ on the three subspaces, as shown in Fig. 8, from which it can be seen that the other two The value of the space is zero, so as to achieve the purpose of suppressing harmonics. At the same time, no loss function is needed to decide the selection of the optimal voltage vector, which reduces the calculation time and improves the running speed of the system.

Figure 9 shows the SVPWM pulse timing diagram of the optimal voltage vector V ₂ . Timing pulses are generated by a pulse generator. In order to reduce the generation of harmonics as much as possible, a symmetrical pulse sequence as shown in Figure 9 is used. As can be seen from Figure 9, the timing diagram of the upper bridge channel of the f and g bridge arms is intermittent (gray). Therefore, in order to generate the timing diagram of the vector more conveniently, the inverse timing diagram of the f and g bridge arms is used. (that is, the timing diagram of the lower bridge arm) is modulated, and when the switching timing diagram of the voltage source inverter is output, the timing diagram of the two bridge arms is inverted to output the correct timing diagram, as shown in Figure 10. Shown as the pulse timing adjustment module.

As shown in Fig. 11, for the dynamic simulation of the seven-phase permanent magnet synchronous motor based on the sub-fast algorithm, the present invention applies this control algorithm to the seven-phase permanent magnet synchronous motor speed control system, and the motor starts 0.05s after no-load start. The no-load steady state is reached, and the stator current of the motor is a sinusoidal waveform with a frequency of 50Hz. After FFT analysis, as shown in Figure 12, it is the result of applying the present invention to the seven-phase permanent magnet synchronous electric harmonic suppression. The THD is only 3.78% of the fundamental component, which has a good harmonic suppression effect.

Further, when the load torque of the motor changes, as shown in Figure 12, the load is suddenly added at 0.1s and the load is suddenly reduced at 0.155s. After the algorithm operation, after only 0.05s of adjustment, the motor quickly reaches a new steady state, indicating that the algorithm The application of the 7-phase permanent magnet synchronous motor improves the dynamic performance of the speed regulation of the seven-phase permanent magnet synchronous motor.

While the content of the present invention has been described in detail by way of the above preferred embodiments, it should be appreciated that the above description should not be construed as limiting the present invention. Various modifications and alternatives to the present invention will be apparent to those skilled in the art upon reading the foregoing. Accordingly, the scope of protection of the present invention should be defined by the appended claims.

Claims (8)

1. A seven-phase permanent magnet synchronous motor rotating speed rapid control algorithm is characterized by comprising the following steps:

the method comprises the following steps: acquiring the output quantity of the seven-phase permanent magnet synchronous motor, and taking the output quantity and the prediction reference current as the input quantity of an MPCC prediction model;

step two: equally dividing the alpha-beta space into a plurality of sectors, wherein each sector has an optimal voltage vector;

step three: obtaining a voltage predicted value on the current time space through calculation of an MPCC prediction model, and taking the voltage predicted value as the input of a sector judgment link consisting of an adder, a divider, a remainder operation and an amplitude limiter to judge the sector number of the current predicted voltage;

step four: outputting the sector number of the current predicted voltage, matching the sector number with a plurality of sectors, outputting the optimal voltage vector in the corresponding sector, and taking the optimal voltage vector as the optimal voltage vector at the current moment;

step five: calculating a pulse sequence required by a seven-phase voltage source inverter for synthesizing the current optimal voltage vector according to a space vector pulse width modulation principle;

step six: the synthesized pulse sequence is acted on the voltage source inverter, so that the direct-current voltage can be inverted into the current required seven-phase voltage.

2. The algorithm for rapidly controlling the rotational speed of a seven-phase permanent magnet synchronous motor according to claim 1, wherein the output quantity of the motor comprises space stator current, rotor angle and rotor rotational speed.

3. The algorithm as claimed in claim 1, wherein the predicted reference current is provided by an outer loop speed PI regulator.

4. The algorithm for fast controlling the rotating speed of the seven-phase permanent magnet synchronous motor according to claim 1, wherein the prediction model is constructed by the seven-phase permanent magnet synchronous motor.

5. The algorithm for fast controlling the rotation speed of a seven-phase permanent magnet synchronous motor according to claim 1, wherein the MPCC prediction model is based on load, the load model is different, the mathematical model is different in the continuous state, and the prediction model is different.

6. The algorithm for rapidly controlling the rotating speed of the seven-phase permanent magnet synchronous motor according to claim 5, wherein the predicted optimal vector is calculated in a sampling period through a discretized mathematical model, the discretized mathematical model is obtained by discretizing the mathematical model in a continuous state through a forward Euler method in the sampling period, and the mathematical model in the continuous state is different due to different loads, and the positions and the sizes of the predicted voltage vectors are different due to different predicting models, that is, the output of the predicting model determines the predicted optimal vector.

7. The algorithm for rapidly controlling the rotating speed of the seven-phase permanent magnet synchronous motor according to claim 1, wherein each optimal voltage vector is synthesized by 5 basic voltage vectors, and a seven-phase voltage source inverter bridge arm switch synthesis sequence of each optimal voltage vector is obtained under the condition that minimum common-mode current and harmonic suppression are ensured.

8. The algorithm for rapidly controlling the rotation speed of a seven-phase permanent magnet synchronous motor according to claim 7, wherein when a pulse sequence required by a seven-phase voltage source inverter with the current optimal voltage vector is synthesized, continuous turn-on pulses of a cliff therebelow are synthesized, and then an inverse sequence of an intermittent turn-on bridge arm pulse sequence is output by combining judgment of a current sector.

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