Research On Reactive Power And Voltage Control Strategy For Distribution Network With DGs

For a long time,energy issues have been the bottleneck in the development of human society.At present,environmental pollution caused by traditional fossil energy power generation has become increasingly prominent.And as a developing power generating system,distributed generation is profoundly affecting the direction of the power industry development.As the substitution and supplemented to traditional fossil energy,the distributed generation,has received strong support from the state for its energy efficiency,low loss,low pollution,flexible operation and efficiency.With the increase of the permeability,the distributed generation changed the power supply mode of the radial passive distribution network from a one-way flow of the traditional power flow to a trend multidirectional flow or even reverse to the active distribution network.Clean energy also changes the distribution of the node voltage.Therefore,in order to ensure the safe and stable operation of the distribution line,it is necessary to study and govern the problem of the voltage limit of the distributed power access point.The main work is as follows:Firstly,the principle of the rise of the node voltage on distributed generation is studied.According to the distribution network model and the formula of the node voltage drop,the voltage of the distributed generation node is affected by the distributed power output and the load.In order to evaluate the influence of distributed generation,a node voltage estimation method suitable for different conditions is proposed.The limit distributed generation access point voltage amplitude is the max node voltage amplitude when the distributed power output power reaches its maximum capacity and the node load does not consume power can reach.This algorithm can be used to judge whether the node voltage may exceed the limit before put the distributed generation into distribution network.The operating distributed generation access point voltage amplitude is the running voltage amplitude under the condition of node load power consumption.This method is suitable to estimate the distributed power supply access point voltage in operation.Then,in this paper,a control strategy of node voltage is proposed to solve the single and multiple distributed generation accessed node voltage control problem.The local voltage control method combines the capacity characteristics and technical specifications of the inverter to adjust the active/reactive output power of the inverter,and has the advantage of maximizing the voltage adjustment of the inverter capacity,which is suitable for the voltage control of a single node in the distribution network.When more than one distributed power supply is connected to the feeder,the local voltage control method can’t control the node voltage of the whole line,then the cooperative voltage control method needs to be implemented.The collaborative voltage control method is suitable for the cooperative control of node voltage.The power adjustment order of distributed power supply is determined by the change law of the influence level of node voltage on each distributed power supply power,which make the economical use of reactive power on the whole feeder through the communication.Through the calculation and analysis of the IEEE33 node simulation system,it is shown that the node voltage estimation algorithm of distributed generation access node voltage is uncomplicated to calculate,and the voltage of distributed power supply access node voltage can be calculated accurately.The local voltage control strategy of distributed power supply access distribution network can make full use of inverter capacity to solve the problem of voltage limit of distributed power supply access node,and the collaborative voltage control strategy of distributed power supply access distribution network can make full use of the surplus reactive power of each node on the whole feeder to realize the cooperative control of node voltage.