Research On Topology And Control Strategy Of New Hybrid Power Flow Control Device

With the dramatic increase of installed capacity of new energy in our country and the large-scale access of new energy with strong randomness and fluctuation to power grid,the impact of high proportion of new energy on power flow distribution is difficult to be coped with by conventional means of power flow regulation.There is an urgent need for power equipment with large capacity,high efficiency and continuous and accurate power flow regulation capability.Therefore,a new hybrid power flow control device(HPST)is presented in this paper,which combines a large capacity dual core symmetric phase shift transformer(PST)and a small capacity voltage source converter(VSC).Compared with PST,the phase shift angle range and the power flow adjustment range are increased,and the power flow can be adjusted continuously and accurately.This device is a high performance-price ratio and high efficiency power flow control device,and has a broad development prospect.In this paper,the existing tide control devices are classified,and the advantages and disadvantages of each type of device are analyzed.Then,the topology and working principle of PST are introduced in detail,and the voltage and power flow adjustment characteristics of PST are analyzed.Then a new hybrid power flow control device(HPST)is proposed based on large capacity PST and small capacity VSC.The voltage and power flow regulation characteristics of HPST are analyzed,and the capacity ratio between PST and VSC in HPST is deduced.Comparing HPST with PST,the advantages and disadvantages of HPST over PST are obtained.Then,for the power flow regulation function of HPST,the control strategies of PST and VSC and the collaborative control strategies of HPST are presented.Finally,PST and HPST simulation models are built in PSCAD simulation software to verify the correctness of the topology,working principle and control strategy of PST and HPST.The power flow regulation performance of PST and HPST is compared under given operating conditions,and the continuous and accurate power flow regulation characteristics of HPST are verified.The principle of power flow regulation in parallel lines by HPST is analyzed and simulated.The ability of HPST to balance power flow in parallel lines is verified.