Research On The Characteristics Of Large-Scale Wind Farms In Close Distance With DC Transmission

Along with worsening of ecological environment and drying up of conventional energy sources, it is to utilize the pollution-free renewable energy that have gradually become an significant direction of alleviating the global current energy crisis and energy development strategy across the world. In recent years, wind power as a major new energy technology has been developing rapidly.In China, the region abundant in wind energy is too far from the load center, as a result, the construction of large-scale long-distance DC transmission channels will greatly ease the present situation of inefficient wind power consumption locally. In order to ensure the safety and stability of large-scale wind power sending out via HVDC, it is of important practical significance to research the influence of DC power regulation and fault disturbance on stable operation of wind farms in close distance.This paper, firstly, analyzes the mathematics model and operation principle of DFIG windfarm, LCC-HVDC and thermal power unit which comprises the large-scale wind power DC transmission system, and verifies the validity of the control strategy for each part based on PSCAD/EMTDC simulation software, which reveals the system steady and transient characteristics. Then, it analyzes the grid system behavior characteristics of large-scale windfarms and DC converter station in close electric distance after fault disturbance from the point of voltage transient characteristics, and focuses on assessing the threat to wind power reliable interconnection of DC power regulation and blocking fault. It also proposes a coordinated control strategy based on STATCOM dynamic reactive support and DFIG converter reactive support from the point of optimizing control system, which effectively suppresses the transient shock to DFIGs by providing reactive support to stabilize the AC busbar voltage together with using DC Chopper circuit. Finally, the electromagnetic transient simulation shows that this control strategy can ensure HVRT performance of DFIG, assist in power grid voltage fast stabilization, and guarantee the security and reliability of DFIG-based wind farms from close range.