The voltage control of grid-connected inverter

What is it about?

This study describes the design and implementation of an inverter control algorithm with both the inverter inner controllable impedance and governor-free characteristics. The inverter controlled as a voltage supply works with open-loop power control in grid-connected operation. It is realised that a pulse-width modulation inverter mimics the primary frequency and voltage modulation characterised similarly to a synchronous generator. On the basis of the proposed control algorithm, the inner controllable impedance and governor-free characteristics are analysed mathematically. Simultaneously, the authors analyse the output power characteristics of the proposed inverter and the level of the decoupled power control for designing the inner controllable impedance. When the inverter connects with the stiff grid, it will appear as the output current deviation problem. The generation mechanism of the dc component from the proposed inverter is clearly identified. The current deviation compensation control is analysed and implemented to solve it. Simulations and experimental results are given to verify the idea.

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Why is it important?

For an excellent inverter control performances while connected with stiff or weak grid, the generation reason of dc component was analysed mathematically and a CDC control block was designed to eliminate the current deviation.

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