HVDC Converter Controller Redundancy via Integrator Term Transfer
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Solution Overview
Problem
The control of high voltage direct current (HVDC) systems is complex, particularly in scenarios requiring redundancy to allow for controller failure and maintenance, while minimizing disturbance to AC and DC voltage waveforms during switching.
Innovation Solution
A control apparatus for a chain-link voltage source converter featuring two converter controllers with integrator elements that can operate in two modes, allowing for smooth transition and initialization of control signals between controllers, including a selector to manage the switching and integrator term transfer between them.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundancy is introduced to allow controller failure and maintenance, then system reliability is improved, but device complexity increases
Solution Approach 1:
The control system is segmented into two independent converter controllers, each capable of independently controlling the voltage source converter. This segmentation allows one controller to fail while the other maintains service, improving reliability without requiring a completely redundant complex system.
Solution Approach 2:
Both converter controllers are designed with identical functionality and structure, each capable of performing the same control tasks. This universality allows either controller to take over seamlessly, simplifying the redundancy implementation while maintaining reliability.
2Ease of repair
If switching between controllers is implemented for redundancy, then system maintainability is improved, but disturbance to voltage waveforms increases
Solution Approach 1:
The standby converter controller continuously calculates and maintains its integrator terms in parallel with the active controller, preparing the control signal in advance. When switching occurs, the standby controller is already prepared with up-to-date integrator values, eliminating startup transients and waveform disturbances.
Solution Approach 2:
The integrator terms are continuously updated by both controllers simultaneously, ensuring that the control signal maintains continuity during switching. This continuous calculation prevents interruptions or disturbances in the voltage waveform when transitioning between controllers.
3Stability of the object's composition
If integrator terms are transferred between controllers during switching, then voltage waveform stability is improved, but device complexity increases
Solution Approach 1:
The standby controller continuously copies the integrator terms from the active controller through parallel calculation. This copying mechanism ensures that when switching occurs, the standby controller has identical integrator values, maintaining voltage waveform stability without requiring complex transfer protocols.
Data Source
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AI summary
A control apparatus (20) configured to control a chain link voltage source converter (1), the control apparatus comprising; two converter controllers (21a, 21b), each converter controller configured to receive a measure of the output voltage and/or current from the converter and determine a control signal therefrom for controlling the voltage source converter (1), each converter controller including at least one integrator element configured to perform an integration operation and output an integrator term in that determination of the control signal, a selector (22) configured to select which one of the converter controllers (21a, 21b) provides its control signal to the converter (1); wherein each integrator element is configured to have two modes, a first mode in which the integrator element determines the integrator term and a second mode in which the integrator term is provided by a corresponding integrator element in the other converter controller.