VSC-HVDC Virtual Grid Control for High-Frequency Resonance
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Solution Overview
Problem
The dynamic characteristics of a power system are deteriorated when filters are used to suppress high-frequency resonance in VSC-HVDC transmission lines, leading to potential system instability and increased risk of converter valve overcurrent during AC faults.
Innovation Solution
A VSC-HVDC high-frequency resonance suppression method that employs a virtual grid adaptation controller in the feedforward procedure of the inner loop controller, which detects the dq-axis component of the actual AC voltage, generates a virtual voltage to track the actual AC voltage, and performs adaptive tracking to correct deviations, thereby reducing resonance risk and improving fault ride-through performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a feedforward low-pass filter is used to suppress high-frequency resonance, then resonance suppression is improved, but system delay increases and dynamic characteristics deteriorate
Solution Approach 1:
The invention changes the control parameter from traditional voltage feedforward to active power feedforward. By detecting actual active power and using it as the feedforward signal, the system avoids the delay issues associated with voltage filtering while still suppressing resonance. The active power signal inherently contains the necessary frequency information without requiring additional filtering that would introduce delay.
Solution Approach 2:
The invention replaces the mechanical filtering approach (low-pass filter on voltage signal) with a computational approach (active power detection and feedforward). Instead of physically filtering the voltage signal to remove high-frequency components, the system computes active power and uses its feedforward signal, which naturally suppresses resonance without introducing significant delay.
2Object-affected harmful factors
If a feedforward nonlinear filter is used to suppress high-frequency resonance, then resonance suppression is improved, but overcurrent risk during AC faults remains
Solution Approach 1:
The invention introduces active power as an intermediary signal between the AC system and the VSC-HVDC controller. By using active power feedforward instead of direct voltage or current feedback, the system indirectly suppresses resonance while maintaining better fault ride-through characteristics. The active power signal acts as a mediator that provides resonance suppression without directly exposing the converter to harmful high-frequency voltage variations during faults.
3Object-affected harmful factors
If filters are used to suppress high-frequency resonance, then resonance suppression is improved, but system stability deteriorates
Solution Approach 1:
The invention replaces traditional voltage-based filtering mechanisms with an active power-based feedforward control mechanism. This substitution eliminates the need for filters that would introduce phase shifts and delays, thereby maintaining system stability while achieving resonance suppression. The active power feedforward approach preserves the natural dynamic response of the system without the stabilizing degradation caused by filter-induced delays.
Data Source
AI summary
Disclosed are a voltage source converter based high voltage direct current (VSC-HVDC) high-frequency resonance suppression method, system, and device. The method includes: when an effective value of an actually input alternating current (AC) voltage is reduced from a normal value to meet a preset condition, making the virtual electrical quantity completely equal to the actual electrical quantity, and performing full real-time tracking for the actual electrical quantity to improve dynamic characteristics of a power system at the moment of a fault; and after performing the full tracking for a period of time, if the effective value of the actual AC voltage is less than a preset threshold, performing adaptive tracking until the actual electrical quantity recovers to a stable value. The present disclosure can reduce a risk of high-frequency resonance of a VSC-HVDC, avoid deteriorating dynamic characteristics of the VSC-HVDC, and improve safety of fault ride-through of the VSC-HVDC.