Research On Control System Of Dynamic Voltage Restorer With Current Limiting Function

Recently, renewable energy sources such as photovoltaic, power plants and wind parks has led to a shift in the way the power grid imagined traditionally. With the development of modern science and technology and the expansion of the electric power construction, the utilization rate of user equipment has proportional increased, and nowadays power quality problems has been more and more sensitive.Dynamic voltage restorer, as the most effective means to solve the problem of power quality currently, can be used to protect sensitive equipment to avoid the influence of voltage dips and interruption.Meanwhile, electric power systems have increased in complexity because of a lot of loops that are composed by integrating the trunk transmission power system. And the inclination of power flow, would increase in short-circuit capacity and expansion of range of instantaneous voltage drop. To prevent damage to dynamic compensation device from fault current in the distribution network and rapidly limit short-circuit current to a set level, the proposed novel dynamic voltage restorer with current limiting function (DVR-FCL) is very meaningful to ensure safety and reliability of the power system.This paper introduces the basic structure and operation principle of DVR system. The topology of the DVR-FCL is set up, and on the basis of it a mathematical model is established. The working principles of the DVR-FCL in both voltage compensation and short-circuit fault are analyzed in detail. Choosing the optimal voltage detection strategies for three-phase four bridge legs inverter after further study of the existing detection method of voltage compensation and short-circuit current. Then the compensation control and current limiting strategies are proposed, and the sequence of state switching is designed for effectively implementing complex functions of the DVR-FCL with voltage compensation and short-circuit current limiting.This paper focus on the design of an optimal limiting characteristic impedance as the objective function accounting with the adjustment of DC voltage and proposed a parameter design with each part of DVR-FCL main ciruit,such as LC filter, series transformer, converter, DC-side capacitor. Consideration with constraints and influences between the current limiting module and voltage compensation module to further improve the parameter design. The correctness and rationality of the topology and parameters design method are verified by simulation results using PSCAD/EMTDC.This paper designs a DVR-FCL control system based on control core of TMS320F2812 and the main circuit selection. And the module structure design isadopted with hardware of the control system. Use CCS3.3 development platform for the control system main program and function subprogram. Finally the experimental prototype is set up for hardware and software debugging. And the results verify the working principle of DVR-FCL.