Voltage Stability Control Method for Multi-Voltage Source Converters Connected to Medium-Voltage DC System

Abstract

The invention discloses a voltage stability control method for connecting a multi-voltage-source converter to a medium-voltage DC system. The method mainly comprises four parts composed of virtual resistive-capacitive impedance reconstruction, DC-side current feedforward, VSC DC port voltage control, and AC port current control. When the VSC uses DC voltage droop control to adjust the DC output voltage, the output impedance of the VSC exhibits negative resistance outside a voltage control bandwidth. Through the virtual resistive-capacitive impedance, the output impedance characteristics of multiple VSC DC ports are reconstructed, such that the VSC output impedance maintains large positive resistance outside the voltage control bandwidth so as to compensate the negative damping of the system outside the voltage control bandwidth and suppress the voltage oscillation of the medium-voltage DC System. Based on the virtual resistive-capacitive impedance, the DC output current feedforward isintroduced. The VSC DC port voltage control uses proportional integral control. The AC port current control is decoupling control in a synchronous rotation coordinate system. The method can enhance the inertia of the DC system while suppressing the oscillation of the DC system so as to realize the stable control of the bus voltage.

Description

technical field [0001] The invention relates to the field of medium-voltage direct current system control, in particular to a medium-voltage direct current system dominated by voltage source converters, and a voltage stability control method for multiple voltage source converters to jointly control the bus voltage of the direct current system. Background technique [0002] The medium-voltage DC system has the advantages of high efficiency and no problems related to frequency and reactive power. It has good application prospects in military and industrial fields such as island power supply, multi-electric aircraft, ships, and submarine power supply. It is a current research hotspot. one. The DC bus voltage is the key to measure the safe and stable operation of the DC system, but the DC system contains a large number of power electronic converters, the negative impedance characteristics of the constant power load, the interaction between the converters, and the change of activ...

AI Technical Summary

Problems solved by technology

However, although the droop control reduces the amplitude of the output impedance within the voltage loop control bandwidth and suppresses low-frequency oscillation, it cannot deal with the oscillation problem outside the voltage loop control bandwidth.

However, in a medium-voltage DC system in which multiple VSCs (Voltage Source Converter, VSC) are used as source converters via droop control, the existing DC system stability and stability control methods based on voltage droop control rarely involve control bandwidth, lines, etc. Influence of effective inductance, filter capacitor, converter control parameters and other factors on system stability

Therefore, traditional droop control or virtual resistance stabilization control is not suitable for medium-voltage DC systems connected to multi-voltage source converters.

Images