Probabilistic Decision Method Of Coordinated Secondary Voltage Control Considering The Randomness Of Wind Power

With the rapid development of power system technology,the large amount of new energy in the power grid and connection of AC/DC system has become a common phenomenon.It brings great challenges to the voltage control.The secondary voltage control is the key part of the multi level voltage control systems.On the one hand,in the gird with centralized wind power connected,there is a large random fluctuation of wind power in a short period of time,whose impact on the voltage and reactive power control cannot be ignored.And this fluctuation makes the traditional coordinated secondary voltage control hard to work.On the other hand,China has put HVDC projects into operation one after another,and the large scale wind power is transmitting through long distance DC system,which put forward new requirements for the coordinated secondary voltage control.Therefore,this paper studies the probability decision method of coordinated second voltage control considering the randomness of wind power.The specific work is as follows:In order to answer whether and how to consider the random fluctuation of wind power in the secondary voltage control,the performance of wind power and scenario simulation method from perspective of the secondary voltage control is in research.The characteristic index of wind power fluctuation is defined.and the wind power fluctuation in hours and seasons is analyzed.Through the given definition of wind power fluctuation,the characteristic time periods with large wind power fluctuation are selected from the original data of wind power.So the randomness of wind power should be considered in the secondary voltage control in these time periods,and the scenario in the characteristic periods should be compressed to get typical scenario and its probability to simulate the wind power random fluctuation.For the first time,the proposed method statistically analyzes the wind power random fluctuation within 15 minutes of the second voltage control period,and simulate the wind power fluctuation,which offers a reference for whether how to consider the wind power randomness in the second voltage control To deal with the influence of wind power random fluctuation on coordinated secondary voltage control,a probabilistic decision method of coordinated secondary voltage control considering the randomness of wind power is proposed.To consider the influence of wind power random fluctuation on coordinated secondary voltage control,a probabilistic decision making method for coordinated secondary voltage control of AC system considering wind power randomness is proposed.On the basis of deterministic coordinated secondary voltage control,the stochastic disturbance of wind power is introduced,and a coordinated secondary voltage control model considering the randomness of wind power is proposed.The sensitivity of node voltage and generator reactive power to wind power is derived,and the decision variables and stochastic control variables are distinguished,and the balance target of generator reactive power and power deviation constraint of tie line are considered simultaneously.The interaction between the two factors is analyzed.The probabilistic scenario method is used to stand for the random power deviation of wind energy,and the chance constrained programming method is used to solve the uncertain optimization problem.This method is worked by the modified IEEE39 node system.This method can adapt to all kinds of possible reactive wind power conditions in the future period.When the wind fluctuation is big,this method can significantly decrease the voltage fluctuation of the pilot bus,and reduce the risk of exceeding the limit of the pilot bus and the generator terminal voltage.At the same time,it has good performance in the balance degree of the reactive power output of the generator,and limitation of the power flow in the tie line.This method has a certain amount of engineering value.In order to consider the influence of HVDC system on coordinated secondary voltage control,a probabilistic decision making method for coordinated secondary voltage control of AC/DC systems is proposed.In view of period of the small and large wind power fluctuation,two coordinated secondary voltage control models of AC/DC systems are established.In the case of small wind power fluctuation,a coordinated secondary voltage control model of AC/DC system considering the voltage and reactive power characteristics of converter station is established.Compared with the existing model,the bus of converter station is regarded as PQ or PV node.In this paper,the role of converter station is reflected through the equation,and the sensitivity of its trigger angel and absorbed reactive energy are derived.In addition to the pilot bus,the bus of converter station is included in the target of minimum the voltage deviation.In the case of large wind power fluctuation,based on the coordinated secondary voltage control model considering the voltage and reactive power characteristics of converter station,the random disturbance of wind power is introduced,and the coordinated secondary voltage control model of AC/DC system considering the randomness of wind power is proposed.The sensitivity of trigger angle and absorbed reactive power of converter to wind power are derived.The probabilistic scenario is selected to represent the original data.The chance constrained programming method is useful to solve the uncertain optimization problem.The method is worked out in the example system.This method can significantly reduce disturbance in AC system to DC system,and reduce the fluctuation of bus voltage in converter station,and also can reduce the action times of discrete equipment in DC system,improve the control accuracy.It is beneficial to the safe and economic operation of AC/DC systems.