电流源型逆变器电机驱动系统的直流链电流控制

DC-Link Current Control of Current Source Inverter Motor Drive System

电流源型逆变器(CSI)电机驱动系统通常使用电压源串联电感来实现恒定的直流链电流,然而因这种方式未对直流链电流进行控制,直流链电流会出现断续或持续增加的问题。为此,采用DC-DC变换器电路设计PI控制器,可以实现对直流链电流的控制。同时,详细分析一个周期内DC-DC变换器与CSI的电压变化规律,通过优化CSI的电流矢量序列,使得直流链电流纹波得到抑制,提高了输出端电机的电流波形质量。实验结果验证了所提出的直流链电流控制方法的可行性与有效性。

Motor drive system can be divided into voltage source inverter(VSI)topology and current source inverter(CSI)topology according to the type of DC side power supply.Compared with VSI,CSI uses inductance as energy storage element,which has high reliability.At the same time,CSI also has the advantages of high output current waveform quality,can realize four quadrant operation of motor load,inherent short circuit protection function and voltage boost function to expand the constant power operation range of motor.However,the DC-link current is not controlled in this way,and the DC-link current will be intermittent or continuously increased.Therefore,a PI controller is designed by using DC-DC converter circuit to control DC-link current.At the same time,the ripple of DC-link current is suppressed by optimizing the current vector sequence of CSI,the inductance and switching loss are reduced,and the current waveform quality of the motor at the output end is improved.Firstly,in order to realize the control of DC-link current,a DC-DC converter circuit is adopted on the basis of the traditional current source inverter circuit.Through the analysis of different working modes of DC-DC converter,two working modes are selected to realize the control of DC-link current,and the field oriented control of CSI motor drive systemis designed.Secondly,the analysis of the DC-link current ripple of CSI system shows that in order to reduce the DC-link current ripple,the voltage difference between the two ends of the inductance should be reduced without increasing the inductance value and the switching frequency.Therefore,by analyzing the output voltage of DC-DC converter and the input voltage of CSI in a cycle in detail,we can know the voltage difference between the two ends of the inductance.Finally,according to the variation regularity of voltage between the DC-DC converter and CSI in one cycle,a method to optimize CSI current vector sequence is proposed.The feasibility of the method is illustrated through the specific analysis of the three segment SVPWM modulation method,and the feasibility of other more segment modulation methods is analyzed.The method proposed in this paper is tested.By observing the DC-link current in the startup stage and the speed change stage,it can be seen that the DC-link current can be controlled by the DC-DC converter circuit in this paper,and it has good dynamics.The current ripple suppression method does not change the dynamics of the DC side.The experiments of DC-link current ripple suppression at different speeds show that the ripple of DC-link current is reduced.At the same time,the harmonic analysis of the output current is carried out,and the total harmonic distortion of the output current is reduced by using the proposed DC-link current ripple suppression method,which proves the effectiveness of the proposed DC-link current ripple suppression method.Therefore,the following conclusions can be drawn.This paper presents a DC-link current control method for CSI motor drive system.The method uses DC-DC converter circuit and PI controller to control the DC-link current.After analyzing the voltage variation rule between DC-DC converter and CSI in one cycle,the DC-link current ripple is reduced by optimizing the current vector sequence of CSI.The experimental platform was built and the experimental verification was carried out.The experimental results show that the proposed DC-link current control method can realize the control of DC-link current,reduce the ripple of DC-link current,thus reduce the inductance loss and switching loss,and improve the quality of the current waveform of the motor.