Positive Damping Reconstruction Impedance Stability Control Method for HVDC Transmission System

Abstract

The invention discloses a method for stable control of positive damping reconstruction impedance of a high-voltage direct-current power transmission system. When switching frequency of a rectificationstation is relatively high, through introduction of a virtual resistor, system damping within control bandwidth is enhanced, and direct current side oscillation is suppressed. When switching frequency of the rectification station is relatively low, and direct current side oscillation frequency is beyond the control bandwidth, the virtual resistor turns to show negative resistance property, and system stability is deteriorated. Phase correction is performed on negative resistance beyond bandwidth, and amplitude of the virtual resistor is not changed, thereby effectively improving a damping characteristic of the high-voltage direct-current power transmission system, suppressing oscillation of the system direct current side, and improving system stability.

Description

technical field [0001] The invention relates to the field of high-voltage direct current transmission systems, in particular to a positive damping reconstruction impedance stabilization control method for high-voltage direct current transmission systems. Background technique [0002] The HVDC transmission system is a cascade system composed of rectifier stations and inverter stations through DC transmission cables. It has the characteristics of high voltage level, large power level, and small controller bandwidth. It can be used as an effective long-distance power transmission system for new energy power stations. Way. In order to increase the damping of the system and suppress the oscillation of the DC side, the traditional control method adopted by the rectifier station of the HVDC transmission system is to introduce a virtual resistance link into the control loop. When the working switching frequency of the rectifier station is high, the virtual resistance can effectivel...

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Problems solved by technology

When the working switching frequency of the rectifier station is high, the virtual resistance can effectively suppress the resonance peak of the system, such as Figure 5 As shown in (a); however, when the working switching frequency of the rectifier station is low, the phase-frequency characteristics of the output impedance of the DC side of the rectifier are as follows: Figure 8 It can be seen that the lower the switching frequency, the narrower the control loop bandwidth of the rectifier, and its phase may sink below -90 degrees outside the control loop bandwidth. If the resonant frequency of the system exceeds the control loop cut-off frequency, the output impedance of the DC side will deteriorate to Negative resistance, when the length of the transmission line changes, the system may have a resonance peak, such as Image 6 As shown in (a), it seriously affects the stability of the system

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