Simulation Research On Doubly-Fed Induction Generator Control Strategy Of VPI-DPC Under Unbalanced Grid

In the current shortage of traditional fossil energy,renewable energy is becoming more and more important.As a kind of clean and renewable energy,wind energy has attracted wide attention and application.Doubly fed wind power generation system has been favored by many users because of its excellent control performance and economic characteristics.There are many kinds of power equipment,power generation equipment and environment in the grid,which make the ideal grid do not exist in practical application.There are a lot of power quality problems in the non ideal power grid,especially the imbalance and harmonic problems.Doubly fed wind power generation system,which is working in a non ideal grid environment,is affected by unbalanced and harmonic problems in the power grid.It may cause the distortion of the current waveform in the rotor,the torque jitter and the gear box damage.Not only can not achieve the ideal power generation effect,but also will deteriorate the power quality in the power grid and cause harm to the doubly fed wind power generation system itself.The control strategy of back-to-back converter in doubly fed wind power generation system is designed.Doubly fed wind power generation system can operate better in non ideal grid environment.And has the ability to withstand harmonics,imbalances and other issues.Therefore,the design of DFIG control stra tegy is of great significance both in theory and practice.This paper expounds the development and present situation of wind power at home and abroad.The doubly fed wind power generation system and its existing control technology are mainly introduced.In order to study the better control technology,this paper starts with the mathematical model of doubly fed wind power generation system.The mathematical model of doubly fed wind power generation system under stationary ABC three-phase coordinates is established.And the mathematical model under DQ rotating coordinate is established respectively.Considering the harmonic and unbalanced phenomena of different frequencies,the model under the dq coordinate is improved.A mathematical model of double PWM converter is constructed for the fan converter of back to back structure.Three resonant controllers are introduced.The PR,PIR,and VPI control strategies control the fan converter.In theory and simulation experiments,the doubly fed wind power generation system under these control strategies is studied and validated.The advantages and disadvantages of various control strategies are obtained.Among them,the VPI control strategy has more obvious advantages for doubly fed wind power generation system under imperfect power grid.The article focuses on the power point of view of the DFIG system controller design.In the bottom of the converter,the space vector modulation method is used to control the converter state.The power transfer relationship is analyzed after the article is rented.Combined with the mathematical model,a direct power control strategy for doubly fed wind power generation system is proposed.The control strategy of VPI-DPC is constructed by combining it with VPI control strategy.Through th eoretical analysis and simulation,the effectiveness and superiority of the control strategy are obtained.