Passive Impedance Adapter Tuning for VSC-HVDC Harmonic Resonance
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Solution Overview
Problem
VSC-HVDC transmission systems face the risk of high-band resonance due to impedance mismatch with the power grid, affecting the safety and stability of the power system.
Innovation Solution
A method for determining the parameters of a passive impedance adapter, comprising a main capacitor, a main resistor, and a branching inductor, to achieve positive impedance characteristics across the full frequency band, thereby eliminating harmonic resonance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If VSC-HVDC transmission capacity is increased and high-power electronic equipment is applied, then transmission efficiency and capacity are improved, but the risk of generating high-band resonance with the connected grid increases
Solution Approach 1:
The patent introduces a passive impedance adapter as an intermediary device between the VSC-HVDC system and the power grid. This adapter contains a main capacitor, main resistor, and branching inductor that work together to transform the impedance characteristics, preventing direct harmful interaction between the VSC-HVDC system and grid that would cause harmonic resonance.
Solution Approach 2:
The patent changes the impedance parameters of the adapter across different frequency bands. By adjusting the impedance magnitude and phase characteristics through the passive components (capacitor, resistor, inductor), the system transforms the impedance to maintain positive real part across full frequency band, thereby eliminating harmonic resonance while preserving high transmission capacity.
2Reliability
If operation modes are restricted to avoid harmonic resonance, then resonance risk is reduced, but adaptability to different operation modes and AC faults is worsened
Solution Approach 1:
The patent implements preliminary action by pre-configuring the passive impedance adapter with specific component values (main capacitor, main resistor, branching inductor) before system operation. This pre-established impedance transformation capability ensures that the system maintains positive impedance characteristics across all possible operation modes and fault conditions, eliminating the need for restrictive operation mode changes.
Solution Approach 2:
The passive impedance adapter serves multiple functions simultaneously: it provides impedance transformation, harmonic resonance suppression, and adaptability to various operation modes and AC faults. The universal design with its passive components enables the system to handle different operating conditions without requiring mode restrictions.
3Reliability
If auxiliary equipment is added to suppress harmonic resonance, then resonance risk is reduced, but system cost and complexity increase
Solution Approach 1:
The patent applies local quality by concentrating the harmonic resonance suppression function in a specific local component - the passive impedance adapter with its main capacitor, main resistor, and branching inductor. This localized solution provides targeted impedance transformation at the critical interface between VSC-HVDC and grid, achieving effective resonance suppression without complicating the entire system structure.
Data Source
AI summary
Method for determining parameter of a passive impedance adapter applicable to VSC-HVDC, including: S1. obtaining VSC-HVDC impedance and VSC-HVDC impedance curve X(f) based on VSC-HVDC impedance; S2. estimating upper limit value of the main capacitor in the passive impedance adapter; S3. calculating adapter parameter curve Xadapter(f); S4. determining value of the main capacitor and varying value of the main resistor until min[X(f)−Xadapter(f)] is maximized; determining whether min[X(f)−Xadapter(f)]>k holds; S5. If min[X(f)−Xadapter(f)]>k does not hold, increasing the value of the main capacitor and performing steps S2-S4 until min[X(f)−Xadapter(f)]>k holds when the value of the main capacitor is within the range of the value of the main capacitor, storing the parameters in an available parameter set; S6. reducing the value of the main capacitor, and storing the parameters when min[X(f)−Xadapter(f)]>k holds in the available parameter set; S7. selecting the available parameters from the available parameter set.