Research On Reactive Power Control Strategy Of HVDC Transmission Converter Station

The energy distribution in the east and west of our country is uneven.The energy content in the western region is relatively rich,and the eastern and central regions are relatively scarce.The acceleration of China’s urbanization will accelerate energy consumption,and power transmission is limited by transmission capacity and distance.Compared with high-voltage AC transmission,HVDC transmission has unique advantages and is widely used in power grids.The converter station of the HVDC transmission system based on the grid-commutated converter(referred to as "high-voltage direct current transmission")adopts thyristor commutation.The phase of the commutated current lags behind the voltage,so the converter station consumes reactive power,not only the reactive power balance of the converter station and the system voltage balance will affect,and will cause pollution to the AC system.When the traditional reactive power control method is used to control the reactive power of the converter station,there will be reactive power exchange between the AC system and the converter station.Therefore,this paper studies the reactive power control strategy of the converter station.The main research work is as follows:Research and design the structure of the converter station,conduct a detailed harmonic analysis on the AC and DC sides of the converter station structure,study the configuration scheme of the reactive power compensation device and the harmonic suppression scheme of the converter station,and the simulation proves that when the traditional reactive power control method is adopted,There is a reactive power exchange volume between the converter station and the AC system.Considering the method that can change the reactive power consumption of the converter station itself,an improved reactive power control strategy with DC current as the main control variable and reactive power exchange and reactive power deviation provided by reactive equipment as feedback is proposed.The simulation model is established in PSCAD/EMTDC,and the strategy is simulated and verified under two working conditions.The simulation results show that the improved reactive power control strategy can improve the accuracy of reactive power control of converter stations,but it has reactive power Limitations of narrow control range.Utilizing the characteristics of static synchronous compensator(STATCOM)that can dynamically compensate for the reactive power demand of the converter station,research and propose a STATCOM reactive power control strategy,establish an overall simulation model in PSCAD/EMTDC,and The simulation verification is carried out,and the simulation results show that the STATCOM reactive power control strategy can also improve the accuracy of the reactive power control of the converter station,and has the advantage of a large reactive power control range.