阅读说明：本技术 一种永磁同步电机mtpa控制与fw控制的切换方法 (A kind of switching method of permanent magnet synchronous motor MTPA control and FW control ) 是由 苏丹丹 杨昆 董小平 付超超 于 2019-09-04 设计创作，主要内容包括：本发明提供了一种永磁同步电机MTPA控制与FW控制的切换方法,在由MTPA控制切换至FW控制的过程中,基于调制比确定切换点；在由FW控制切换至MTPA控制的过程中,基于<I>d</I>轴电流确定切换点。基于调制比或<I>d</I>轴电流的永磁同步电机MTPA控制与FW控制的切换方法,能够避免电机转速、输出转矩的大小、直流母线电压的高低、电机参数的变化等对切换点的影响,保证了电机输出转矩与参考转矩基本一致,提高了永磁体同步电机工作的平顺性。(The present invention provides the switching methods of a kind of permanent magnet synchronous motor MTPA control and FW control to determine switching point based on modulation ratio during switching to FW control by MTPA control；During switching to MTPA control by FW control, it is based on d Shaft current determines switching point.Based on modulation ratio or d The switching method of the permanent magnet synchronous motor MTPA control and FW control of shaft current, it can be avoided the influence to switching point such as variation of motor speed, the size of output torque, the height of DC bus-bar voltage, the parameter of electric machine, it ensure that motor output torque is almost the same with torque reference, improve the ride comfort of permanent magnet synchronous motor work.)

1. a kind of switching method of permanent magnet synchronous motor MTPA control and FW control, characterized in that switched to by MTPA control During FW is controlled, switching point is determined based on modulation ratio.

2. the switching method of permanent magnet synchronous motor MTPA control and FW control according to claim 1, characterized in that work as tune When system is than being equal to or more than 0.907, FW control is switched to by MTPA control.

3. the switching method of permanent magnet synchronous motor MTPA according to claim 1 control and FW control, characterized in that by During FW control switches to MTPA control, switching point is determined based on d shaft current.

4. the switching method of permanent magnet synchronous motor MTPA control and FW control according to claim 3, characterized in that for Durface mounted permanent magnet synchronous motor switches to MTPA control by FW control when d shaft current is greater than zero.

5. the switching method of permanent magnet synchronous motor MTPA control and FW control according to claim 3, characterized in that for Internal permanent magnet synchronous motor is i by the condition that FW control switches to MTPA control_d> i_{d_MTPA}, i_dFor d shaft current, i_{d_MTPA}For D shaft current when MTPA is controlled.

Technical field

The present invention relates to Motor Control Field, specifically a kind of permanent magnet synchronous motor MTPA control is cut with what FW was controlled Change method.

Background technique

In permanent magnet synchronous motor (PMSM) control, when DC bus-bar voltage is rated value and motor output torque is specified When torque, corresponding motor speed is known as base speed.Base speed hereinafter referred to as permanent torque area, generallys use unitary current torque capacity (MTPA) it controls to reduce copper wastage, improves operational efficiency.Base speed generallys use weak magnetic (FW) control referred above to invariable power area System with weaken air gap flux linkage and limit counter electromotive force make its not with revolving speed improve and increase.

MTPA refers under the premise of torque reference is given, by the current component of reasonable distribution d axis and q axis, makes stator Electric current is minimum, i.e., the maximum control method of motor output torque under unitary current.MTPA control can reduce copper wastage, improve Operational efficiency, optimization system performance.Further, since the electric current exported needed for inverter is smaller, it can to the capacity requirement of inverter Relative reduction.FW control is to realize the important means of permanent magnet synchronous motor high-speed cruising, is controlled by FW to weaken air gap flux linkage And limiting counter electromotive force makes it not improve and increase with revolving speed.

When permanent magnet synchronous motor work is at permanent torque area, in order to improve drive-train efficiency, generally using MTPA control Strategy；And when permanent magnet synchronous motor work is at invariable power area, in order to guarantee the normal work of motor, it is necessary to control plan using FW Slightly.In invariable power area, to improve inverter efficiency, inverter exports maximum space voltage vector, at this time can be maximum by control Angle between voltage vector and q shaft voltage guarantees that output torque is consistent with target torque, is referred to as sweared based on space voltage The FW of measuring angle is controlled.

MTPA control is usually the control strategy of two close cycles, and is single closed loop based on the FW of space voltage vector angle control Control.How to realize switching of the permanent magnet synchronous motor between double-closed-loop control device and single closed loop controller, is to guarantee motor energy Enough premises to work in full speed range.

Summary of the invention

It is an object of the invention to provide the switching methods of a kind of permanent magnet synchronous motor MTPA control and FW control, to improve Ride comfort when permanent magnet synchronous motor MTPA control switches with FW control.

The object of the present invention is achieved like this: a kind of switching method of permanent magnet synchronous motor MTPA control and FW control, During switching to FW control by MTPA control, switching point is determined based on modulation ratio.Specifically, when modulation ratio is equal to or greatly When 0.907, FW control is switched to by MTPA control.

During switching to MTPA control by FW control, switching point is determined based on d shaft current.For durface mounted permanent magnet Synchronous motor switches to MTPA control by FW control when d shaft current is greater than zero.For internal permanent magnet synchronous motor, by FW The condition that control switches to MTPA control is i_d> i_{d_MTPA}, i_dFor d shaft current, i_{d_MTPA}D shaft current when being controlled for MTPA.

The invention proposes a kind of controlled based on the permanent magnet synchronous motor MTPA of modulation ratio or d shaft current to cut with what FW was controlled Method is changed, during switching to FW control by MTPA control, switching point is determined based on modulation ratio；It is switched to by FW control During MTPA is controlled, switching point is determined based on d shaft current.Permanent magnet synchronous motor MTPA based on modulation ratio or d shaft current The switching method of control and FW control, can be avoided motor speed, the size of output torque, the height of DC bus-bar voltage, electricity The influence to switching point such as variation of machine parameter, ensure that motor output torque is almost the same with torque reference, improves permanent magnetism The ride comfort of body synchronous motor work.

Detailed description of the invention

Fig. 1 is the output speed torque characteristic map figure of permanent magnet synchronous motor.

Fig. 2 is the switching method flow chart of MTPA control with FW control.

Fig. 3 is the maximum voltage polar plot that inverter is exported in linear zone.

Fig. 4 is inverter maximum output voltage V under dq coordinate system_smaxWith the relational graph of dq shaft voltage.

Fig. 5 is the functional block diagram of the FW control based on space voltage vector angle.

Specific embodiment

When analyzing three-phase PMSM, generally requires and does following hypothesis:

1) stator winding Y shape connects, and leads to symmetrical three phase sine alternating current；2) saturation effect of silicon steel sheet is ignored not Meter, air-gap field is at Sine distribution；3) eddy-current loss and magnetic hystersis loss of motor are not considered；4) there is no excitation winding on rotor.

According to above-mentioned it is assumed that voltage equation of the PMSM under dq two-phase rotating coordinate system are as follows:

In formula (1), V_d、V_qRespectively stator voltage component under dq two-phase rotating coordinate system；L_d、L_qRespectively d-axis (d axis) Inductance and quadrature axis (q axis) inductance, have L for surface-mount type PMSM_d=L_q, have L for built-in PMSM_d<L_q；i_d、i_qRespectively d axis With the electric current of q axis；R_sFor stator winding resistance；ω_rFor the angular rate of rotor；λ_fThe magnetic linkage generated for permanent magnet.

The torque equation of motor are as follows:

In formula (2), T_eTo export electromagnetic torque, P is the number of poles of PMSM.

As shown in FIG. 1, FIG. 1 is the output speed torque characteristic map of permanent magnet synchronous motor figures.In general, when permanent magnetism is same Motor work is walked when base speed is following, Ying Caiyong MTPA control；When permanent magnet synchronous motor work is more than base speed, Ying Caiyong FW Control.However, motor, in practical work process, MTPA controls the selection with FW control switching point (CSP) in addition to being influenced by motor speed In addition, the size of output torque, variation of the height of DC bus-bar voltage, the parameter of electric machine etc. can generate the selection of switching point It influences, two regions A, B as shown in figure 1.

Be divided into two parts by dotted line in Fig. 1: the region MTPA and the region FW, dotted line is common with output torque by motor speed Determining controlling tactic switch curve.On switching curve, MTPA control and the control of FW are applicable in.Work as DC bus-bar voltage (V_dc) when remaining unchanged, modulation ratio (MI) is maximum value (0.907), and inverter exports maximum voltage V at this time_smax.According to permanent magnetism Voltage equation (formula (1)) and torque calculation formula (formula (2)) of the synchronous motor under dq two-phase rotating coordinate system are it is found that In Switch on curve, when output torque increases, corresponding revolving speed is reduced；When output torque reduces, corresponding revolving speed liter It is high.For example, in region A, output torque T_eLess than rated value T_eratedWhen, the revolving speed of switching point is higher than base speed n_rated.In region B, Output torque T_eGreater than rated value T_erated, the revolving speed of switching point is lower than base speed n_rated。

In addition, during MTPA control switches with FW control, in order to guarantee the ride comfort of motor work, motor need to be made Reality output torque is consistent with torque reference.Therefore, the smooth switching between MTPA control and FW control, it is important to determine two A switching point: first is that MTPA control is switched to the switching point of FW control；Second is that FW control is switched to the switching point of MTPA control.

When using MTPA control, the value of MI should be less than 0.907；When MI value is equal to or more than 0.907, motor should be from MTPA control switches to FW control.When motor is controlled using FW, since the value of MI is 0.907 always, needed at this time according to d axis Electric current judges switching point.Referring to fig. 2, Fig. 2 is the switching method flow chart of MTPA control with FW control.

(1) FW control is switched to by MTPA control

In order to improve the utilization rate of DC bus-bar voltage, and avoids inverter from entering inelastic region and generates torque pulsation, The maximum value of MI takes 0.907 in the present invention.I.e. when the value of MI increases to 0.907, in order to guarantee that motor can work normally, MTPA control must switch to FW control.

For based on space voltage vector angle FW control, when MTPA control switch to FW control switching point determine with It afterwards, is the ride comfort for guaranteeing handoff procedure, i.e. guarantee motor output torque and torque reference is almost the same, it is also necessary to calculate voltage The initial angle γ of vector₀.If γ₀It is improper to select, it will causes output torque to deviate reference value, and causes motor speed Fluctuation.On switching point, MTPA control is applicable in FW control, available following formula:

In formula (3), V_d0, V_q0It is the dq shaft voltage of switching point.

The initial angle γ of space voltage vector at switching point₀It can be calculated by following formula:

(2) MTPA control is switched to by FW control

According to the working principle of permanent magnet synchronous motor it is found that by revolving speed, the reduction of torque or the raising of DC bus-bar voltage Etc. factors influence, motor should from FW control switch to MTPA control.And when motor use FW control when MI value always for 0.907, therefore switched to without image of Buddha MTPA control and judge switching point according to MI when FW is controlled.

MTPA control can reduce stator current, improve the efficiency of drive system, therefore when motor works in permanent torque area When be generally used MTPA control.If using FW in permanent torque area and controlling, and motor output torque and motor is kept to turn Speed is given reference value, the voltage vector V being applied on motor at this time_sV will be equal to_smax, it is electric which is greater than actual demand Pressure.According to the math equation (formula (1)) of motor it is found that motor stator electric current will be greater than using after the increase of dq shaft voltage value Electric current when MTPA is controlled, it may be assumed that

In formula (5), i_{q_MTPA}、i_{d_MTPA}Dq shaft current when respectively using MTPA control, i_{q_FW}、i_{d_FW}To be controlled using FW Dq shaft current when processed.

For durface mounted permanent magnet synchronous motor, its q shaft current is constant under identical output torque.It is increased at this time Electric current is d shaft current.Therefore when d shaft current value is greater than zero, FW control should switch to MTPA control；It is same for built-in type permanent-magnet Motor is walked, due to q axle inductance L_qGreater than d axle inductance L_d, can use d shaft current and generate reluctance torque, therefore controlled using MTPA When d shaft current value will be less than zero.At this point, being answered by the condition that FW control switches to MTPA control are as follows:

i_d> i_{d_MTPA} (6)

FW control based on space voltage vector angle is described below down.

The transmission characteristic of inverter refers to the relationship between line voltage virtual value and modulation ratio.Modulation ratio is defined as inverter The ratio between the peak value of fundamental wave phase voltage phasor and maximum fundamental wave phase voltage, calculation method is as follows:

In formula (7), V_dcFor DC bus-bar voltage.

As inverter output voltage V_sFor space voltage vector hexagon maximum inscribed circle when, the value of modulation ratio are as follows:

Space voltage vector modulation (Space Vector Pulse Width Modulation, SVPWM) control strategy Advantage is can to directly control alternating-current motor stator magnetic linkage rotational trajectory, to obtain quasi-circular rotating excitation field, therefore can be not High switching frequency declines low torque ripple, reduces current harmonics.When modulation ratio is less than 0.907, inverter output line voltage It is linear relationship between modulation ratio.Once modulation ratio is greater than or equal to 0.907, inverter output line voltage can be in modulation ratio Existing non-linear, current harmonics increases at the same time, and torque pulsation increases.To guarantee that inverter works in linear zone, modulation ratio Maximum value should take 0.907.

When modulation ratio is equal to 0.907, the voltage vector of inverter output is its maximum value V in linear zone_smax, such as scheme Shown in 3, which is the radius of the maximum inscribed circle of space voltage vector hexagon.Hexagon is no Zero voltage vector in Fig. 3 When the maximum voltage vector that can be output of inverter, but current harmonics increases at this time, and torque pulsation increases, and inverter works non- Linear zone.To reduce current harmonics, the voltage vector hexagon for using space voltage vector modulation technology to export inverter Inscribed circle.Modulation ratio is equal to 0.907 at this time, and the voltage vector of inverter output is the radius V of inscribed circle_smax。

For permanent magnet synchronous motor, either controlled using unitary current maximum torque control or weak magnetic, Voltage equation under dq two-phase rotating coordinate system is the same, i.e. formula (1).But inverter under both control strategies The constraint condition of output voltage vector (see formula (10)) is different (such as formula (11), (12)), therefore the property of equation group There is notable difference.

V_s< V_smax (11)

V_s=V_smax (12)

When using unitary current maximum torque control, voltage vector V needed for motor work_sIt is defeated less than inverter maximum Voltage V out_smax(see formula (11)), voltage equation of the permanent magnet synchronous motor under dq two-phase rotating coordinate system are two independent Linear equation, therefore can be solved using the method for decoupling.Theoretically, after motor speed and given torque reference, the two Whether there is or not array solutions for equation, and can get by unitary current maximum torque control makes the smallest optimal solution of stator current.

It is limited by DC bus-bar voltage, the maximum output voltage of inverter is V_smax.Under weak magnetic control, in order to improve The utilization rate of DC bus-bar voltage, the voltage vector V of motor work_sInverter maximum output voltage V should be equal to_smax(see formula (12)), at this time voltage equation group of the permanent magnet synchronous motor under dq two-phase rotating coordinate system be two intercouple it is non-linear Equation.After motor speed and torque reference are given, which only has unique solution.In asking for Nonlinear System of Equations In solution preocess, even there is the disturbance of very little, it is also possible to cause the greatest differences of solution.And motor is during the work time, it is various Disturbance be it is unavoidable, such as the fluctuation of DC bus-bar voltage, the variation of the parameter of electric machine, inverter output voltage it is non-linear Deng.Therefore, which is one of the difficult point of weak magnetic control.

The maximum space voltage vector V of inverter output_smaxRelationship with dq shaft voltage is as shown in figure 4, γ is V in figure_smax With q shaft voltage V_qBetween angle.At this point, dq shaft voltage can be calculated by formula (13).

Formula (13) are substituted into permanent magnet synchronous motor in the voltage equation formula (1) under dq two-phase rotating coordinate system, it can :

Formula (14) is the theoretical basis of the weak magnetic control based on space voltage vector angle.It is by analysis it is found that public Formula (14) is single input (γ), dual output (i_q、i_d) Nonlinear System of Equations, and each given input quantity (γ) can only be acquired One group of solution (i of equation group_q、i_d), the group solution based on equation can calculate output at this time according to torque formula (2) and turn Square.

Therefore, the weak magnetic control based on space voltage vector angle can not decouple Nonlinear System of Equations (formula (14)) Under the premise of, torque reference needed for the angle (γ) by controlling space voltage vector makes motor output, without being answered with calculating Given weak magnetoelectricity stream (i_d)。

When being controlled using the weak magnetic based on space voltage vector angle, after given voltage vector angle, the output of motor Torque is unique.It therefore can be based on the error between torque reference and actual torque, using PI control strategy, needed for obtaining Space voltage vector angle γ^*, it is shown below:

In formula, Δ T_eFor torque reference T_e ^*With actual torque T_eBetween torque error, K_pT、K_iTRespectively torque error Ratio and integral coefficient, γ₀For the initial angle of voltage vector.

Fig. 5 is the functional block diagram of the FW control based on space voltage vector angle.Firstly, the letter that current sensor is fed back Number carry out Clarke transformation with Park convert, obtain current motor output torque T_e, and calculate itself and torque reference T_e ^*Between Error delta T_e；Then, the angle that the space voltage vector of inverter output can be obtained in PI (formula (15)) is carried out to torque error γ^*, and d axis and q shaft voltage are calculated according to formula (13)；Finally, carrying out Park inverse transformation to d axis and q shaft voltage obtains v_α ^*、 v_β ^*, and required voltage vector is modulated based on SVPWM.