Controlling And Switching Method Strategy Research On Utility-interactive Inverter

Nowadays, the fossil fuels such as goal and oil are going to be exhausted. Renewableenergy including solar and wind energy has been attracting more and more attentions.In thedistributed generation system based on renewable energy.The grid connected inverter is theinterface between DG and grid.In this paper, the key for the Utility-Interactive invertertechnology, focusing on the following aspects of the problem: a Utility-Interactive inverter filterdesign, standalone mode voltage inverter control technology and grid_connected operationmode of the inverter current control technology, smooth Utility-Interactive inverter switchingmethod different operating modes.Utility-Interactive inverter operates independently LC-type structure, using LCLgrid_connected structure and running, there is a huge difference in their operating characteristics;therefore, the filter design is very important. To this end, a quantitative analysis of thedistribution of this article Bridging the arm voltage harmonics and voltage distortion inaccordance with the filter capacitor, the inverter side inductor current ripple, and net currentdistortion three indicators selected filter parameters, and from theory a systematic exposition ofLCL filter design methods.In standalone mode, the paper established inverter state space and transfer function of twomathematical models, analyzes the instantaneous value of the voltage of a single loop PIDcontrol and dual-loop control based on capacitive current feedback, and introduce two poleplacement design method the system controller analysis and design parameters, simulationresults show that the inverter output voltage fast dynamic response, steady-state accuracy is high.Also verifies the introduction of the current inner loop control, the system showed a better abilityof anti-load disturbances.In grid_connected mode, the paper established LCL grid inverter transfer function of themathematical model, based on a detailed analysis of the feedback capacitor current feedback andnet current regulator design, PI and PR is mainly based on two current regulator. And theintroduction of controller parameters design of the steady-state error, phase margin and gain margin based on this method can be simply and accurately obtain the appropriate closed loopparameters. Simulation results verify the validity and accuracy of parametric design.For stand-alone mode and grid_connected mode and in the structure and control algorithmsconstitute difference, we design the Utility-Interactive switching process inverter mode whenswitching to discuss and summarize the method of switching between the two operating modes.And for the grid mode to standalone mode load voltage oscillation phenomena studied will begradually reduced to zero reference current solutions. The simulation results show theeffectiveness of switching strategy.In order to verify the correctness of the simulation and theoretical analysis, experimentalplatform to build a prototype, and details of the hardware and software design of the system.Apreliminary experimental results had been given through experimental platform.