Development And Implementation Of High-power Grid Simulator

In recent years, with much attention on the development of new energy technology, in order to realize new energy generation, such as wind and solar energy, it usually need merge into power grid after converters control. Converters and grid are restricted and influence each other. The stability of the grid and grid power quality are impacted owing to converter access, simultaneously, it is a challenge on fault ride through capability of converters if the grid system is faulty. Due to the randomness of real power grid failure, the converter is not easy to study the grid adaptability. Therefore, it is particularly necessary to develop a flexible and perfect generator to simulate a variety of grid failure. This dissertation presents a simulator based on the form of converter and gives detailed study of the converter control technology. The control strategies of rectifier-side converter and inverter-side converter are both discussed comprehensively. Simulations and experiments demonstrate the correctness of the research results and the feasibility of the generator.Firstly, the mathematical model and control strategy of rectifier-side converter have been discussed. The mathematical model of PWM converter is established, and grid voltage oriented vector control strategy is researched on the basis of the model. In addition, the implementation methods of PI regulator and the Space Vector Pulse Width Modulation are introduced in detail.Secondly, the control strategy of inverter-side converter has been investigated. The symmetrical component method is employed to analyze the vectors under unbalanced grid voltage. The dual-dq coordinate system is analyzed to achieve positive and negative sequence separation. The mathematical algorithm and control strategy to simulate unbalanced fault are mainly researched. According to simulate different types of grid fault, different control methods have been taken and made comparative analysis. This dissertation also applies novel Proportion Resonant controller in asymmetric voltage dip vector control system.This dissertation adopts MATLAB to simulate the operation of the generator. The steady state performance and dynamic performance of rectifier-side converter have been studied as well as the performance of inverter-side converter when the grid’s fault is simulated. Moreover, based on the simulation results of different control strategies, comparison analysis is taken. In order to validate the theoretical analysis and simulation, this dissertation experimented on the system platform. Different types fault of grid have been simulated in the experiment. The steady state performance and dynamic performance of rectifier-side and inverter-side converter are investigated according to take25kW doubly-fed wind power simulation platform. The experiments validate the effectiveness and feasibility of control strategy of the simulator. It provides the condition for low voltage ride through (LVRT) and other related performance of converters in the future.