Research On Three-Phase Current Source High Frequency Link Matrix Type Inverter And Control

Inverters are widely used in new energy power generation systems.According to the characteristics of dc-side power supply,they can be divided into voltage source inverters and current source inverters.Compared with the voltage source inverter,the current source inverter has a boost characteristic,and no additional boost link is required.At the same time,high-frequency isolated inverters have received extensive attention because of their advantages in safety,compactness,and high voltage ratio.Compared with the traditional line frequency isolated inverter,the high frequency isolated inverter has lower cost,smaller volume and higher frequency.Therefore,this paper takes the three-phase current source high-frequency link matrix inverter as the research object,and studies its topology,modulation and closed-loop control strategy.Firstly,in order to suppress the voltage spike caused by the mismatch between the dcside current and the leakage inductance current of the high-frequency transformer,a threephase current source high-frequency link matrix inverter is proposed.The topology includes a current source H-bridge and a matrix converter,which are connected by a highfrequency transformer.The primary side of the high-frequency transformer is current source H-bridge,which can directly control the dc-side current and achieve safe commutation and soft switching of the H-bridge through a series resonant tank composed of resonant capacitor and high-frequency transformer leakage inductance.The secondary side is direct matrix converter,which can directly transform the single-phase highfrequency square wave voltage into three-phase power frequency voltage,reducing the power conversion stage.At the same time,an integrated current-type SPWM modulation and an integrated current-type space vector modulation suitable for the topology are proposed,and their working principles are analyzed in detail.Secondly,aiming at the on-state loss problem of the proposed two modulations,this paper analyzes the stage in which the on-state loss can be reduced during the working process,and proposes an improved method to make the high-frequency transformer work in the current discontinuous mode to reduce its loss.At the same time,combined with the characteristics of the two modulations,the integrated SPWM modulation and the integrated space vector modulation of the transformer current are formed.The proposed improved modulation strategy reduces the on-state loss when the bridge arm is through.Then,the mathematical model of three-phase current source high frequency link matrix inverter is established in three-phase stationary coordinate system and two-phase synchronous rotating coordinate system.At the same time,combined with the modulation principle,the dc inductance,resonant capacitance and output filters are designed.In addition,the control strategy of the proposed converter is studied.In order to suppress the resonance of the output CL filter,the active damping control is introduced,and the control loop including the active damping link and the system delay link is analyzed.Finally,a three-phase current source high-frequency link matrix inverter experimental platform is built,and the hardware and software of the experiment are designed.The DSP + CPLD control system is adopted.The feasibility and effectiveness of the proposed scheme are verified by experiments.