阅读说明：本技术 减小永磁同步电机变频器直流母线电压纹波幅值的方法 (Method for reducing DC bus voltage ripple amplitude of permanent magnet synchronous motor frequency converter ) 是由 童怀 陈新 陈新度 黄运保 于 2019-07-30 设计创作，主要内容包括：为了解决现有技术中加入转矩前馈补偿引起电解电容的纹波电流增大而导致的电容发热的问题,本发明提供一种减小永磁同步电机变频器直流母线电压纹波幅值的方法,根据压缩机转矩前馈补偿的特点,在低速运行区域某些特定的频率节点上,在对转矩电流实施前馈补偿控制的同时对转矩电流进行锁相环控制,使转矩电流波峰与输入交流电源过零点之间存在一个固定的相位角,控制系统中电流环采用PI调节控制,补偿后的转矩电流<Image he="76" wi="45" file="DEST_PATH_FDA0002149681230000015.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>作为q轴电流环的输入量,电流环的输出作为dq坐标系的电压分量V<Sub>d</Sub>、V<Sub>q</Sub>,过SVPWM计算功率模块中六个功率管导通的占空比,形成6路PWM信号,从而有效减小直流母线电压纹波幅值。(In order to solve the problem of capacitor heating caused by the increase of ripple current of an electrolytic capacitor due to the addition of torque feedforward compensation in the prior art, the invention provides a method for reducing the ripple amplitude of the DC bus voltage of a frequency converter of a permanent magnet synchronous motorAccording to the characteristic of torque feedforward compensation of a compressor, on certain specific frequency nodes in a low-speed operation area, feedforward compensation control is carried out on torque current and phase-locked loop control is carried out on the torque current at the same time, so that a fixed phase angle exists between a torque current peak and a zero crossing point of an input alternating current power supply, PI regulation control is adopted in a current loop in a control system, and the compensated torque current is subjected to PI regulation control The output of the current loop is taken as the voltage component V of the dq coordinate system as the input of the q-axis current loop d 、V q And calculating the conduction duty ratio of six power tubes in the power module through SVPWM to form 6 paths of PWM signals, thereby effectively reducing the ripple amplitude of the voltage of the direct current bus.)

1. A method for reducing the ripple amplitude of the DC bus voltage of a permanent magnet synchronous motor frequency converter is characterized by comprising the following steps:

s1: measuring stator phase current i of permanent magnet synchronous motor by sampling_u、i_vObtaining a third stator current i by calculation_w＝-i_u-i_v；

S2: obtaining the mechanical angle theta of the rotor position of the permanent magnet synchronous motor through a position sensor or a position-sensorless algorithm, and differentiating the theta to obtain the mechanical angular velocity omega of the permanent magnet synchronous motor_r＝dθ/dt；

S3: the stator current i obtained in the step S1 is used_u、i_v、i_wObtaining d-axis component i of stator current through Clarke transformation and PARK transformation_dAnd q-axis component i_q；

S4: according to a particular frequency node f_NSetting the running speed of the permanent magnet synchronous motor to be omega_set＝2πf_NThe speed regulation in the control system adopts PI control, and the given rotating speed omega_setAs the input to the speed ring, the output of the speed ring is

S5: according to the set running speed omega_setObtaining a feedforward compensation current;

the method for obtaining the feedforward compensation current in the step S5 is as follows:

in the formula i_{q_Amp}Compensating the current amplitude, theta, for feed-forward_{q_comp}Compensating angle, i, for feed forward_{q_comp}For feed-forward compensating current,Is the torque current output by the speed loop,is the compensated torque current; omega_setFor a given rotational speed.

S6: carrying out zero-crossing detection on the alternating-current input power supply to obtain a zero-crossing signal of the alternating-current input power supply;

s7: according to the zero-crossing signal of the AC input power obtained in the step S6, the torque current i is converted into_qPerforming phase-locked loop control by a phase-locked loop control system to enable i_qA fixed phase angle theta exists between the wave crest of the input alternating current power supply and the zero crossing point of the input alternating current power supply_PLLThe output of the phase-locked loop is omega_PLL；

S8: the output of the phase-locked loop control system in the step S7 is made to be omega_PLLAnd the set running speed omega_setAdding as inputs to the speed loop;

s9: the current loop in the phase-locked loop control system in the step S7 adopts PI regulation control, and the compensated torque currentAs an input quantity of the q-axis current loop, an input quantity of the d-axis current loopI obtained in step S3_d、i_qFor feedback of the current loop, the output of the current loop is used as a voltage component V of the dq coordinate system_d、V_q；

S10: v of the voltage component described in the step S9_d、V_qCalculating voltage component V of alpha and beta coordinate system through PARK inverse transformation_α、V_β；

S11: voltage component V_α、V_βCalculating the conduction duty ratio of six power tubes in the power module through SVPWM to form six paths of PWM signals;

s12: and controlling the three-phase power module to drive the permanent magnet synchronous motor to work by the six paths of PWM signals in the step S11, so as to achieve the purpose of inhibiting the bus voltage ripple of the frequency converter of the permanent magnet synchronous motor.

2. The method for reducing the ripple amplitude of the dc bus voltage of the inverter of the pmsm according to claim 1, wherein f in step S4_NThe value law is as follows: when the frequency of the input AC power is f, f_NCan selectOrOrOne value of (1).

Technical Field

The invention relates to the technical field of motor control, in particular to a method for inhibiting bus voltage ripples of a frequency converter of a permanent magnet synchronous motor running at a low speed, which is particularly suitable for the low-speed running condition of the permanent magnet synchronous motor in a single-rotor compressor frequency conversion air conditioner.

Background

The permanent magnet synchronous motor has the advantages of simple structure, high power density, high efficiency, wide speed regulation range and the like, and is widely applied to the field of variable frequency air conditioners at present. The single-rotor compressor is widely adopted in household variable frequency air conditioners at present due to the lowest cost and high efficiency, however, a permanent magnet motor in the single-rotor compressor drives a roller to compress a refrigerant through an eccentric crankshaft, the load torque period of the compressor fluctuates, and the load torque period fluctuation can cause severe vibration of an air conditioner outdoor unit under the condition of low speed.

Disclosure of Invention

In order to solve the problem of capacitor heating caused by the fact that ripple current of an electrolytic capacitor is increased due to the fact that torque feedforward compensation is added in the prior art, the invention provides a method for reducing the ripple amplitude of a direct-current bus voltage of a frequency converter of a permanent magnet synchronous motor.

In order to achieve the purpose, the invention adopts the specific scheme that: a method for reducing the ripple amplitude of the DC bus voltage of a permanent magnet synchronous motor frequency converter is characterized by comprising the following steps:

s1: measuring stator phase current i of permanent magnet synchronous motor by sampling_u、i_vObtaining a third stator current i by calculation_w＝-i_u-i_v；

S2: obtaining the mechanical angle theta of the rotor position of the permanent magnet synchronous motor through a position sensor or a position-sensorless algorithm, and differentiating the theta to obtain the mechanical angular velocity omega of the permanent magnet synchronous motor_r＝dθ/dt；

S3: the stator current i obtained in the step S1 is used_u、i_v、i_wObtaining d-axis component i of stator current through Clarke transformation and PARK transformation_dAnd q-axis component i_q；

S4: setting the running speed of the permanent magnet synchronous motor to be omega according to the specific frequency node fN_set＝2πf_NThe speed regulation in the control system adopts PI control, and the given rotating speed omega_setAs the input to the speed ring, the output of the speed ring is

S5: according to the set running speed omega_setObtaining a feedforward compensation current;

s6: carrying out zero-crossing detection on the alternating-current input power supply to obtain a zero-crossing signal of the alternating-current input power supply;

s7: according to the zero-crossing signal of the AC input power obtained in the step S6, the torque current i is converted into_qPerforming phase-locked loop control by a phase-locked loop control system to enable i_qA fixed phase angle theta exists between the wave crest of the input alternating current power supply and the zero crossing point of the input alternating current power supply_PLLPhase-locked loopOutput of ω_PLL；

S8: the output of the phase-locked loop control system in the step S7 is made to be omega_PLLAnd the set running speed omega_setAdding as inputs to the speed loop;

s9: the current loop in the phase-locked loop control system in the step S7 adopts PI regulation control, and the compensated torque currentAs an input quantity of the q-axis current loop, an input quantity of the d-axis current loopI obtained in step S3_d、i_qFor feedback of the current loop, the output of the current loop is used as a voltage component V of the dq coordinate system_d、V_q；

S10: v of the voltage component described in the step S9_d、V_qCalculating voltage component V of alpha and beta coordinate system through PARK inverse transformation_α、V_β；

S11: voltage component V_α、V_βCalculating the conduction duty ratio of six power tubes in the power module through SVPWM to form six paths of PWM signals;

s12: and controlling the three-phase power module to drive the permanent magnet synchronous motor to work by the six paths of PWM signals in the step S11, so as to achieve the purpose of inhibiting the bus voltage ripple of the frequency converter of the permanent magnet synchronous motor.

Wherein, the value law of fN in the step (4) is as follows: when the frequency of the input AC power supply is f, fN can be selectedOrOrOne value of (1).

The method for obtaining the feedforward compensation current comprises the following steps:

in the formula i_{q_Amp}Compensating the current amplitude, theta, for feed-forward_{q_comp}Compensating angle, i, for feed forward_{q_comp}For feed-forward compensating current,Is the torque current output by the speed loop,is the compensated torque current; omega_setFor a given rotational speed.

Has the advantages that: the invention aims at the specific frequency node of the permanent magnet synchronous motor in low-speed operation, performs feedforward compensation control on the torque current and performs phase-locked loop control on the torque current at the same time, so that a fixed phase angle exists between the torque current wave crest and the zero crossing point of the input alternating current power supply, thereby effectively reducing the voltage ripple amplitude of the direct current bus and effectively reducing the voltage ripple amplitude of the direct current bus.

Drawings

FIG. 1 is a block diagram of a position sensorless vector control system for a permanent magnet synchronous motor.

Fig. 2 single rotor compressor load torque curve.

FIG. 3a Torque Current i_qThe simulated waveform of (2).

FIG. 3b shows the full-wave rectified output voltage | V_acA simulated waveform of l.

FIG. 3c shows the DC bus voltage V_PNThe simulated waveform of (2).

Fig. 4a is a phase diagram of a zero-crossing signal before phase-locking is stabilized.

FIG. 4b shows i before the phase lock is stabilized_qPhase diagram of (2).

Fig. 5a is a phase diagram of the zero-crossing point signal after phase locking stabilization.

FIG. 5b shows the phase locked i_qPhase diagram of (2).

Fig. 3a, 3b, and 3c are aligned with the horizontal axis (time axis) as a reference to fig. 3.

Fig. 4a and 4b are aligned with reference to the horizontal axis (time axis) to form fig. 4.

Fig. 5a and 5b are aligned with reference to the horizontal axis (time axis) to form fig. 5.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

According to the characteristic of torque feedforward compensation of the compressor, on certain specific frequency nodes in a low-speed operation area, the feedforward compensation control is carried out on the torque current, and meanwhile, the phase-locked loop control is carried out on the torque current, so that a fixed phase angle exists between a torque current wave crest and a zero crossing point of an input alternating-current power supply, and the voltage ripple amplitude of a direct-current bus is effectively reduced.

According to the invention, a simulation model of the three-phase permanent magnet synchronous motor position-sensorless vector control system shown in the figure 1 is built on a Matlab/Simulink platform. The parameters of the permanent magnet motor are as follows: the number of pole pairs pn is 3; stator resistance R_s1.7 Ω; stator straight axis inductance L_d8.9 mH; quadrature axis inductance L_qM 7H; back emf coefficient k_e46.8V/krpm; moment of inertia of rotor J7.6 x 10-⁴kg*m²(ii) a The ac input voltage is 220V, the input voltage frequency F is 50Hz, and the electrolytic capacitor size after the rectifier bridge is 680 μ F.

The method comprises the following specific steps:

step 1: measuring the stator phase current i of the parallel connection of the motors by sampling_u、i_vObtaining a third stator current i by calculation_w＝-i_u-i_v；

Step 2: obtaining the mechanical angle theta of the rotor position of the motor through a position sensor or a position-sensorless algorithm, and differentiating the theta to obtain the mechanical angular velocity omega of the motor_r＝dθ/dt；

And step 3: stator current i_u、i_v、i_wObtaining a d-axis component i of the stator current by performing Clarke conversion and PARK conversion_dAnd q-axis component i_q；

And 4, step 4: since the input voltage frequency f is 50Hz, it is selectedGiven operating speed of the compressor is ω_set50 π rad/s. Setting the operating speed of the compressor to ω_set＝2πf_NThe speed regulation in the control system adopts PI control, and the given rotating speed omega_setAs the input to the speed ring, the output of the speed ring is

And 5: in order to restrain the rotating speed fluctuation caused by the load torque fluctuation, the invention implements feedforward compensation control on the torque current, and the rotating speed is 50 pi rad/s corresponding compensation amplitude i_{q_Amp}4A, compensation angle theta_{q_comp}121.5 mechanical angle.

Step 6: carrying out zero-crossing detection on an alternating-current input power supply;

and 7: according to the zero-crossing signal of the AC input power supply, the torque current i is converted_qPerforming phase-locked loop control to make i_qA fixed phase angle theta exists between the wave crest of the input alternating current power supply and the zero crossing point of the input alternating current power supply_PLLThe output of the phase-locked loop is omega_PLL；

And 8: the output of the phase-locked loop is omega_PLLAnd the set running speed omega_setAdding as inputs to the speed loop;

and step 9: the current loop in the control system adopts PI regulation control, and the compensated torque currentAs an input quantity of the q-axis current loop, an input quantity of the d-axis current loopi_d、i_qFor feedback of the current loop, the output of the current loop is used as a voltage component V of the dq coordinate system_d、V_q；

Step 10: v of voltage component_d、V_qBy PARK inversionConverting and calculating voltage component V of alpha beta rectangular coordinate system_α、V_β；

Step 11: voltage component V_α、V_βCalculating the conduction duty ratio of six power tubes in the power module through SVPWM to form 6 paths of PWM signals;

step 12: and 6 paths of PWM signals control the three-phase power module to drive the permanent magnet synchronous motor to work.

The above examples were analysed according to the attached figures: fig. 1 is a block diagram of a position sensorless vector control system for a permanent magnet synchronous motor in a rolling rotor compressor according to an embodiment of the present invention, which includes units such as a speed loop, a dq axis current loop, Clarke and PARK transformation, speed and position estimation, maximum torque to current ratio control (MTPA), torque current feed-forward compensation, PARK inverse transformation, SVPWM calculation, a three-phase PWM inverter, and a permanent magnet synchronous motor.

The embodiment discloses a technical scheme for inhibiting bus voltage ripples of a controller of a variable frequency air conditioner, wherein the variable frequency air conditioner adopts a single-rotor compressor, and a permanent magnet motor in the compressor drives a roller to compress a refrigerant through an eccentric crankshaft and meets the sudden change of load torque in the rotating process: the load sudden change is carried out once in each mechanical period corresponding to the permanent magnet motor; load variations are closely related to the mechanical position of the compressor rotor; the amplitude of the load sudden change is closely related to the working condition of the air conditioner and is increased along with the increase of the internal pressure; this sudden change in torque is more pronounced as the inlet and outlet pressure differential is greater at lower speeds.

Fig. 2 is a waveform of a load torque curve of a compressor adopted by the invention in a mechanical cycle of a rotor within 360 degrees under three different working conditions. When the working condition of the inverter air conditioner changes, the profiles of the load torques of the compressor are basically the same, the fluctuation of the load torques is increased along with the increase of the internal pressure of the compressor, as shown in the figure, the torque changes between 0.3 and 4.2Nm under light load, and the torque fluctuation changes between 0.3 and 6.8Nm under heavy load. Under different working conditions, the mechanical angle of the rotor corresponding to the maximum load torque changes, for example, the mechanical angle corresponding to the light load working condition is 245 degrees, and the mechanical angle corresponding to the heavy load working condition is 230 degrees.

Shown in FIG. 3 as torque current i_qFull wave rectified output voltage | V of input AC power supply_acL and electrolytic capacitor end DC bus voltage V_PNSimulated waveform of (f)_N25Hz, the input AC voltage frequency is 50Hz, so that a torque current i_qPeriod and | V_acFour periods correspond. Before t is 2s, the torque current i is not adjusted_qPerforming phase-locked loop control, and starting to control the torque current i when t is 2s_qAnd performing phase-locked loop control, and stabilizing through about 0.5s of phase-locked control. FIG. 4 shows i before the phase lock is stabilized_qBefore the phase relation graph between the waveform and the zero crossing point of the input alternating current power supply is locked and stabilized_qThe phase angle between the wave crest of the input alternating current power supply and the zero crossing point of the input alternating current power supply is a random value; FIG. 5 shows the phase locked i_qThe phase relation between the waveform and the zero crossing point of the input alternating current power supply is shown schematically, i after phase locking is stable_qA fixed phase angle theta exists between the wave crest of the input alternating current power supply and the zero crossing point of the input alternating current power supply_PLL。

Theta in FIG. 5_PLLThe mechanical angle is approximately equal to 70 degrees, the value is obtained by online adjustment during the experiment by a user, the aim of obtaining the minimum direct current bus voltage ripple amplitude is achieved, and different hardware circuit parameters, different given speeds and different load working conditions theta are achieved_PLLMay not be the same.

As shown in fig. 3, before t is 2.5s, the torque current i is not applied_qPerforming stable phase-locked loop control, DC bus voltage V_PNThe ripple range of the transformer is 270V-315V, and the ripple amplitude reaches 45V; after t is 2.5s, the torque current i is converted_qThe phase-locked loop is controlled to enter a steady state, and then the voltage V of the direct current bus is_PNThe ripple range of the DC bus voltage is 278V to 308V, the ripple amplitude is reduced to 30V, and the ripple amplitude of the DC bus voltage is reduced by about 30%.

The invention is in the process of rotating torque current i_qApplying feedforward compensation control while simultaneously applying torque current i_qAnd the phase-locked loop control is carried out, so that the ripple amplitude of the voltage of the direct current bus can be effectively reduced.

The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily change or replace the present invention within the technical scope of the present invention. Therefore, the protection scope of the present invention is subject to the protection scope of the claims.