The Control Strategy Research Of New Grid-connected Converter Of Direct Drive Wind Power System

Along with the energy crisis and environmental pollution is becoming more andmore serious, the development and utilization of new and renewable clean energy hasbecome an urgent problem in today’s society. In renewable energy, wind energy has largereserves、renewable、non-pollution and other characteristics, at the same time, windpower is a power generation mode with lower cost and commercial prospects, which hasbeen drawn extensive attention to many countries. At present, the variable speed constantfrequency (VSCF) wind power system is widely adopted in the field of wind power, inwhich the direct-drive wind power generation system has become the mainstream ofdevelopment attributing to low mechanical loss、high power generation efficiency、lowmaintenance cost and so on, and the grid converter which is seen as core device forgrid-connection of wind turbine has become the focus of research. At present, indirect-drive wind power generation system, grid converter which is widely used hasvarious types, such as the “AC-DC-AC dual PWM converter” and “non-controlledrectifier+boost+PWM inverter” program, in which each of them has differentcharacteristics, but also exist problems such as large volume and high cost. Therefore,this paper proposes a new Buck-Boost matrix converter (BBMC) as grid-connectedconverter, and analyzes its grid-connected control strategy and low voltage ride-throughtechnical background capability during the fault of grid, and verifies the correctness oftheoretical analysis through the simulation. The main work of this thesis includes:First of all, the background、significance and the research status of wind powergeneration system are discussed, and BBMC is put forward as grid-connected converterof direct-drive wind power system and the dynamic performance of BBMC is studied andsimulated by MATLAB. The results show that the dynamic performance of BBMC is ofhigh practical value.Secondly, according to BBMC characteristics which can be divided into machine side converter and grid side converter two parts on the structure and can be controlledindependently, the corresponding control strategies are studied and simulated. Themotor-side converter uses the rotor flux-oriented vector control strategy; according to thebasic requirements of wind power, taken the grid voltage as reference signal, thegrid-side converter uses dual loop control strategy based on capacitor voltage andinductance current for controlling variable.Thirdly, this article expounds the low voltage ride through protection circuit ofdirect-drive wind power system, analyzes the basic principle based on BBMC, uses thedual loop control strategy and simulates its control effect.Finally, the experimental system based on grid-side converter of BBMC has beendeveloped, in which DSP is taken as controller and MOSFET as power switch. Theexperimental system is tested combing with the relevant software and the relatedindicators can meet the design requirements.