Optimization And Control Of Governor Parameters In Power System Under Asynchronous Networking Condition

During the long-term grid planning process,China Southern Power Grid proposed that Yunnan Power Grid be used as a separate sending-end power grid and asynchronously connected to the South China Power Grid.Yunnan Power Grid’s rich hydropower resources were sent out through 7 DC lines,which improved Yunnan The power transmission capability of the power grid greatly reduces the risk of system instability caused by DC commutation failure or lock-up in the original synchronous power grid operating state.In order to verify the safety and stability of China’s power grid operation after the implementation of asynchronous connection,China Southern Power Grid Corporation conducted a comprehensive test on the system after asynchronous networking in 2016.During the test,there were many long-term ultra-low frequency oscillations phenomenon in the Yunnan power grid.Therefore,studying the mechanism of ultra-low frequency oscillation and the factors that cause ultra-low frequency oscillation in asynchronously connected systems are of great significance for the safe and stable operation of the power grid.Firstly,this paper introduces the related content in the small disturbance analysis and the related models of water turbines and steam turbines in the Yunnan power grid.Based on the Phillips-Heffron model,the mechanism of ultra-low frequency oscillation is analyzed using the method of damping torque.The effects of the water hammer time constant T_W and the steam volume time constant T_CH on ultra-low frequency oscillations are analyzed in detail.The results show that in the ultra-low frequency band,the damping characteristics of the steam turbine speed regulation system are significantly better than that of the hydro turbine,and the steam turbine basically provides the positive damping coefficient,and the hydraulic turbine unit basically provides a negative damping coefficient,and the turbine has an obvious abrupt change point of the negative damping characteristic.As the T_W continues to increase,the negative damping characteristic also strengthens.These conclusions provide for subsequent analysis.The theoretical basis.In this paper,by comparing the impact of the permanent droop coefficient b_p in the simplified model of the governor of the hydroturbine unit with the complex model,the analysis shows that the simplified model can be applied to the analysis of ultra-low frequency oscillation theory.The analysis results show that the safe and stable operation of the power grid can be guaranteed by increasing the bp parameter within a reasonable range.Then in the complex model,the influence of the PID parameters in the governor on the ultra-low frequency oscillation is analyzed based on the damped torque method,and then a method for optimizing PID parameters based on the genetic-particle swarm algorithm is proposed.This method also considers the primary frequency adjustment of the speed control system and the time constant of different water hammer effects.Finally,the simulation analysis is performed in a 4 machine 2 area system with single machine single load and asynchronous networking to verify the effectiveness of the PID parameter optimization strategy for ultra-low frequency oscillation suppression.Finally,the ultra-low frequency oscillation phenomenon in Yunnan power grid is studied,and the damping characteristics of steam turbine and water turbine speed control systems in Yunnan power grid are analyzed in detail.The results show that the thermal power unit in Yunnan power grid can suppress the occurrence of ultra-low frequency oscillation.The hydropower unit exacerbated the occurrence of oscillations.This paper uses the actual data of Yunnan Power Grid,and through the simulation analysis of different operating conditions,reproduces the ultra-low frequency oscillation phenomenon of Yunnan Power Grid.The simulation results are consistent with the theoretical analysis.Finally,the method of this paper is used to optimize and compare the PID parameters of the governor of Yunnan power grid.Simulation results show that the optimization method proposed in this paper can effectively suppress the ultra-low frequency oscillation problem in Yunnan power grid...