Research On Converter System For Direct-drive Wind Power Based On The Proportional Resonant Control

As conventional energy such as coal, oil, natural gas and so on are being moreand more limited, and they bring serious air pollution in the combustion process, sorenewable energy is getting more and more attention. Of the renewable energy, windenergy because it is developed the fastest, its development and utilizationtechnology is most mature, and its development scale is the largest, plays aparticularly important role in its rapid development and utilization. Of wind powersystem, the permanent magnet direct drive wind power system because of the uniqueadvantages such as no gearbox and low maintenance costs becomes an importantdevelopment direction in variable speed constant frequency wind power systems inthe future.The PI controller is often used as current controller in the conventional controlsystems. But because it can only realize to track DC signal with no difference, somany coordinate rotation transformation are need. That increases the difficulty ofthe control algorithm. And to get a good dynamic performance, it needs introducethe cross-coupling term and former feed-forward compensation term in associationwith temperature and the circuit parameters, affecting the robustness of the controlsystem. In addition, the algorithm using conventional PI controller for harmoniccompensation is complex, difficult to realize the project. Proportional integralresonant controller (PR) can realize no static error adjustment tracking when theinput signal is AC signal in the stationary coordinate system. So the introduction ofPR controller into the control system can overcome the deficiencies of the PIcontroller and obtain good control effect.Converter system for direct-drive wind power based on the proportionalresonant control is researched in this paper. It firstly introduces the current researchstatus of wind power technology. And then from the calculation of wind power, itanalyzes the characteristics of wind turbines. According to the composition of theconverter in the wind power system, it establishes mathematical model of permanentmagnet direct driving generators (D-PMSM), researches the basic structure of thePWM converter and derives its mathematical model, and describes the mathematicalmodel of the intermediate DC link between back-to-back double PWM according tothe analysis of the converter energy transmission. Then in-depth analysis of the PR controller principles and its performancecharacteristics are done, then the performance is improved, and based on that above,control strategy of full power converters for direct driving permanent magnetsynchronous wind power generation system based on an improved PR controller isproposed and the simulation model is build. The effectiveness and superiority of thisstrategy is verified through comparison of simulation and analysis of the PI controlmethod. The simulation results show the effectiveness of vector control strategybased on the PR controller. Through decomposition of current with method ofsymmetrical components, it finds that, PI control methods failed to achieve goodtracking control when there are harmonics in machine side or grid side of system, soit needs a complex harmonic compensation algorithm. Against this problem, thispaper will put the PR controller whose performance was improved into the convertersystem of permanent magnet direct driving wind power to control inhibit harmonic,in order to improve the quality of the output electric power.