Development And Application Of Dynamic Voltage Regulating Device In Distribution Network

In the medium voltage distribution network system of our country,abnormal conditions such as low,high or amplitude fluctuation are common scenes because of the large difference in power supply radius,unreasonable setting of distribution shift position and unequal load distribution.At the same time,voltage quality problems such as voltage harmonics and unbalance are becoming increasingly serious when nonlinear loads connecting to the public grid,which will affect the power supply reliability of the distribution system and bring extra line loss.As a new type of power electronic device to solve the voltage quality problem effectively,Dynamic Voltage Reguator which is based on Flexible AC Transmission Systems has become a research hotspot in recent years.Firstly,the working principle of the dynamic voltage regulating device suitable for the 10kV medium voltage distribution network is studied in this dissertation.For the rapid calculation of voltage deviation,harmonics and unbalance components,an improved synchronous coordinate transformation strategy based on backward difference calculation is adopted.To ensure the overall dynamic performance and steady precision of the control system,a compound control strategy based on the combination of feedback and feed-forward control is implemented.In order to avoid the transient impulse voltage,the output side of the studied device is connected in parallel with a bidirectional power electronic switch and a zero-voltage virtual bypass strategy is adopted to improve the overall reliability of the system.The function of the dynamic voltage regulator is simulated in the software of PSIM and the experimental platform of the device is built on the basis of software and hardware design.Last but not least,the studied device is applied in the lOkV network of a manufacturing enterprise,which verifies the feasibility and correctness of the research contents in this dissertation.