超高海拔光伏电站低电压穿越测试系统设计关键技术

西北高海拔地区太阳能资源丰富,大规模光伏电站并网影响西北电网安全稳定,低电压穿越能力是光伏电站可靠接入西北电网的重要指标。海拔超过4 000m的超高海拔地区开展光伏发电系统低电压穿越能力测试需要解决测试装备的频繁操作过电压与高原电气设备绝缘配合等问题,防止出现绝缘放电事故。测试系统的绝缘放电问题既取决于投切电抗器产生的高频过电压,也与狭小空间内设备布置结构优化设计相关。首先结合光伏发电低电压穿越试验系统,提出了超高海拔地区光伏电站低电压穿越测试装备设计方法,并针对影响瞬态过电压的因素进行了理论分析,提出了抑制试验过程中过电压的有效措施。通过有限元分析方法对车载空间内部的电场强度进行校核,保障超高海拔环境下车载狭小空间结构设计不出现绝缘放电风险点,保障了设备的电气绝缘安全。设计方案成功应用于海拔超过4 000m地区的低电压穿越测试系统,并开展多个电站低电压穿越测试。

Key Design Techniques of Low Voltage Ride-through Test System for Ultra-high Altitude Photovoltaic Power Station

The solar energy resources of high-altitude areas in Northwestern China are abundant and the large-scale grid-connected photovoltaic(PV)power station affects the safety and stability of the northwest power grid. The low voltage ride-through(LVRT)capability is an important indicator for the reliable access of PV power station to the northwest power grid. The LVRT test of PV power generation system in ultra-high altitude areas with an altitude over 4 000 meters needs to solve the problems of frequent operation overvoltage of test equipment and insulation coordination of plateau electrical equipment to prevent the occurrence of insulation discharge accidents. The insulation discharge problem of the test system depends not only on the high-frequency overvoltage generated by the switching reactor, but also on the optimal design of the equipment layout structure in a small space. An LVRT experimental system for PV power generation is proposed, and a method for the development of LVRT test equipment for PV power station in the ultra-high altitude regions is proposed. The factors that affect the transient overvoltage are analyzed theoretically, and the measures for the suppression of overvoltage in the test process are finally suggested. Through the finite element analysis method, the electric field strength inside the vehicle-mounted space is checked to ensure that no risk of insulation discharge occurs in the narrow space structure of the vehicle under the ultra-high altitude environment, and the electrical insulation safety of the equipment is ensured. The design scheme has been successfully applied to LVRT test system at an altitude of over 4 000 meters, and LVRT tests are carried out for several power stations.