Coordinated Control Of Multi-terminal HVDC Transmission System With Large-scale Energy Storage Connected To The Grid

The construction of a new power system with new energy as the main body requires large-scale energy storage devices.Energy storage has good application prospects in multi-terminal direct current transmission.This article focuses on the coordinated control of large-scale energy storage into the grid,focusing on the impact of energy storage power stations on the power of the receiving end of the system when the output of new energy is unstable due to the influence of weather.Firstly,based on the mathematical model in the MMC rotating coordinate system,this paper proposes the nearest level approximation modulation and the MMC converter station level internal and external loop decoupling control strategy,and builds the simulation model of MMC-HVDC at both ends in PSCAD/EMTDC.The simulation results show that when the line power changes,the double closed loop control strategy of rectifier and inverter side under active components can quickly respond,achieve smooth send by the end of the power transmission.Based on the mathematical model in the MMC rotating coordinate system,this paper first proposes the nearest level approximation modulation and MMC converter station-level inner and outer loop decoupling control strategies.The simulation results show that when the line power changes,the active components on the rectifier side and the inverter side under the dual closed-loop control strategy can respond quickly to achieve smooth power transmission at the sending and receiving ends.According to the mathematical models of wind turbines,photovoltaic power generation,and battery energy storage,respectively,wind turbine grid-connected control strategies,photovoltaic grid-connected system control strategies,and battery energy storage control strategies are successively proposed.The simulation results verify the correctness of the above-mentioned control strategies..Finally,a comprehensive energy control strategy for the multi-terminal wind-fire-light-storage HVDC transmission system is proposed and verified by simulation.The simulation results show that,regardless of energy storage charging or discharging,the power range of the receiving end grid fluctuates within ±5%,and the response time when it reaches a steady state is less than 0.5s.The research in this paper shows that in the multi-terminal DC transmission system,after the energy storage power station is added,the comprehensive energy coordinated control strategy proposed in this paper is adopted,and the power response of the receiving end of the grid is fast.When the system has a transmission power shortage,the energy storage power station responds quickly and maintains The power grid of the receiving end is balanced.