Switching Valve Timing Control for Low-Distortion HVDC Waveforms
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Solution Overview
Problem
In high voltage direct current (HVDC) transmission and reactive power compensation, existing switching valves face challenges in preventing voltage waveform distortion and ensuring accurate operational timing due to unwanted switching operations, leading to potential over or under-voltage conditions and electrical noise.
Innovation Solution
A switching valve with a controller that applies time delays to the start times of switching operations based on charging or discharging currents, incorporating module dead-time and switching element turn-on and turn-off times to optimize module switching in and out of the circuit, thereby reducing the risk of voltage waveform distortion and improving operational accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If switching operations are performed without time delay compensation, then switching speed is improved, but voltage waveform distortion and operational accuracy deteriorate
Solution Approach 1:
The controller pre-calculates and applies appropriate time delays to switching operations based on the current direction (charging or discharging). This preliminary timing adjustment compensates for the inherent switching element delays, ensuring that modules are switched at the precise moment needed to maintain voltage waveform accuracy while achieving fast switching response.
2Productivity
If module switching is performed rapidly, then productivity is improved, but voltage waveform distortion and electrical noise increase
Solution Approach 1:
The controller monitors the current direction (charging or discharging) and uses this feedback to dynamically adjust the switching timing. By detecting the operational state and applying compensatory time delays based on this feedback, the system maintains rapid switching while preventing voltage waveform distortion and electrical noise that would otherwise result from uncontrolled switching transitions.
3Device complexity
If switching element turn-on and turn-off times are not compensated, then device complexity is reduced, but voltage waveform distortion and operational reliability worsen
Solution Approach 1:
The controller modifies the timing parameters of switching operations by applying calculated time delays that account for switching element characteristics. This parameter adjustment compensates for the inherent delays in switching element turn-on and turn-off times without requiring additional hardware components, thereby maintaining device simplicity while significantly improving operational reliability and preventing voltage waveform distortion.
Data Source
AI summary
There is provided a switching valve for a voltage source converter, the switching valve including a number of modules, each module including at least one switching element and at least one energy storage device, each switching element and each energy storage device arranged to be combinable to selectively provide a voltage source, the switching valve including a controller programmed to selectively control the switching of the switching elements to select zero, one or more of the modules to contribute a or a respective voltage to a switching valve voltage. The controller is programmed to selectively control the switching of the switching elements to carry out a switching operation and to apply a time delay if a charging current is flowing through the modules and/or apply a time delay to a start time of the switching operation if a discharging current is flowing through the modules.