Switching Valve Timing Compensation for HVDC Waveform Accuracy
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Solution Overview
Problem
Voltage source converters in HVDC transmission systems face challenges in minimizing voltage waveform distortion and operational accuracy due to incorrect timing of switching operations, leading to unwanted harmonics and electrical noise.
Innovation Solution
A switching valve with a controller that applies a time delay to the start time of switching operations, considering charging and discharging currents, module dead-time, and switching element turn-on and turn-off times to accurately control the selection and deselection of modules, thereby optimizing the timing of module switching.
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 increases due to incorrect timing
Solution Approach 1:
The controller pre-calculates and applies time delay compensation based on the current state (charging or discharging) before initiating the switching operation. This preliminary timing adjustment ensures that the module switching occurs at the correct moment, preventing voltage waveform distortion while maintaining fast switching response.
2Ease of operation
If module switching is performed without considering current direction, then operational simplicity is improved, but operational accuracy deteriorates due to wrong number of modules switched
Solution Approach 1:
The controller continuously monitors the current direction (charging or discharging) through feedback signals and dynamically adjusts the time delay parameter accordingly. This feedback mechanism ensures that the correct number of modules are switched in or out based on the real-time operational state, maintaining high accuracy without complicating the switching logic.
3Manufacturing precision
If time delay is applied to switching operation start time, then voltage waveform distortion is reduced, but switching response time increases
Solution Approach 1:
The controller dynamically changes the time delay parameter based on the operational state (charging or discharging current). By optimizing the delay value for each specific condition, the system achieves minimal voltage waveform distortion while keeping the switching response time as short as possible, avoiding excessive delays.
Data Source
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AI summary
There is provided a switching valve for a voltage source converter (20), the switching valve comprising a plurality of modules (44), each module (44) including at least one switching element (46) and at least one energy storage device (48), the or each switching element (46) and the or each energy storage device (48) in each module (44) arranged to be combinable to selectively provide a voltage source, the switching valve including a controller (50) programmed to selectively control the switching of the switching elements (46) to select zero, one or more of the modules (44) to contribute a or a respective voltage to a switching valve voltage, wherein the controller (50) is programmed to selectively control the switching of the switching elements (46) to carry out a switching operation, the switching operation including switching at least one of the modules (44) into circuit in the switching valve and/or switching at least one of the modules (44) out of circuit from the switching valve, wherein the controller (50) is programmed to apply a time delay to a start time of the switching operation to switch the at least one module (44) into circuit in the switching valve if a charging current is flowing through the modules (44) and/or apply a time delay to a start time of the switching operation to switch the at least one module (44) out of circuit from the switching valve if a discharging current is flowing through the modules (44), wherein the time delay includes a sum of a module dead-time and a switching element turn-on time reduced by a switching element turn-off time.