Voltage Source Converter Phase Current Control
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Solution Overview
Problem
Voltage source converters face challenges in independently controlling phase currents from a multi-phase AC electrical network, especially when imbalances occur due to uneven loading or changes in electrical ratings, which limits their ability to draw a wide range of current combinations and requires additional hardware, increasing size, weight, and cost.
Innovation Solution
A voltage source converter with a controller that can selectively generate modified AC voltage demands for each single-phase limb, allowing independent control of AC voltage and phase current, enabling the modification of phase currents to balance imbalances and adapt to changes in electrical ratings without affecting other phase currents, and eliminating the need for additional converter hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If additional converter hardware is added to handle phase current imbalances, then the ability to draw a wide range of current combinations is improved, but the size, weight, and cost increase
Solution Approach 1:
The controller dynamically adjusts operating parameters (AC voltage demand, switching patterns) of existing single-phase limbs to adapt to phase current imbalances and draw a wide range of current combinations without adding hardware
Solution Approach 2:
The voltage source converter uses its own existing components (controller, switching elements, single-phase limbs) to self-regulate and handle imbalances, eliminating the need for additional converter hardware
2Ease of operation
If traditional converter control is used, then the structure is simple, but the ability to independently control phase currents is limited
Solution Approach 1:
The controller independently controls each single-phase limb separately, allowing independent adjustment of AC voltage demand for each phase to achieve independent phase current control
Solution Approach 2:
The controller dynamically adjusts the AC voltage demand and switching patterns in real-time based on detected phase current conditions, enabling adaptive independent control of each phase
Data Source
AI summary
A voltage source converter includes DC terminals, a plurality of single-phase limbs, and a controller. Each single-phase limb includes a phase element and switching elements. Each limb is connected between the DC terminals and is controllable to generate an AC voltage at the AC side of the corresponding phase element so as to draw a respective phase current from a multi-phase AC electrical network. The controller is configured to selectively generate a modified AC voltage demand for at least one limb in response to an imbalance in the phase currents and/or a change in electrical rating of at least one limb. The controller is configured to selectively control, in accordance with the or the respective modified AC voltage demand, the or each corresponding limb independently of the or each other limb to modify the voltage at the AC side of its phase element and thereby modify the corresponding phase current.