Research On LCL Type Dual Buck Bidirectional Inverter

With the distributed energy as the representative of renewable energy,electric vehicles and grid interaction(V2G),AC and DC hybrid microgrid,battery energy storage technology in full swing to achieve the bidirectional flow of energy converter as an important interface with the power grid Equipment plays a big role.In this paper,a dual Buck bidirectional DC-AC converter with high efficiency and non isolation is selected as the research object.The output filter of bidirectional DC-AC converter has three types:L,LC and LCL.LC type filter is usually used in voltage source off-grid converter,can suppress the harmonic of converter output voltage;when in current source grid-connected circuit,due to the grid voltage clamp,the attenuation effect on grid current harmonic only filter inductor,the filter capacitor is approximately a local load,which will affect the phase of the injection network current,the LC type filter is generally not suitable for current source grid-connected circuit.L type filter has large inductance and low dynamic response speed,so LCL type is gradually replacing L type filter because of its higher harmonic attenuation efficiency and small size compared with L type,LCL type filter is selected in this paper.Since the LCL filter is a three order system,the selection of filtering parameters is more complex than the L filter,and there are inherent resonance problems,resulting in instability of the system.The existing of the LCL filter filter parameters and reasonce suppression methods are summarized.And the LCL filter was modeled and analyzed,considering the filtering performance and resonance suppression using illustration method to design the filter parameters,ensure the high quality of the network side current,and the LCL filter parameter selection process is given.When the LCL dual Buck bidirectional inverter is working in the grid-connected mode,the method of current weighted average control based on grid-connected voltage feedforward is adopted in this paper,and the order of the system is reduced so as to solve the resonance problem of the LCL filter,and has better waveform quality of the incoming current.When the circuit is working in rectified PFC mode,an improved double-loop control method of voltage and current is adopted,PI control is adopted for the voltage outer loop,current weighted average control of current inner loop,which to achieve the stability of the output DC voltage and high power factor and the high quality of the network side current waveform.The paper regard the LCL type dual Buck bidirectional inverter as the research object,through the PSIM simulation software to build the LCL dual Buck inverter simulation platform,the simulation research of both the grid-connected inverter and rectifier PFC,and the Altium PCB software design principle prototype,a 1000W LCL dual buck bidirectional inverter experimental platform was set up to verify the rationality of the LCL filter parameter selection and the effectiveness of the resonance suppression control strategy.