Converter Voltage Feedback Control for Renewable Microgrids
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Solution Overview
Problem
Island grids and microgrids supplied by renewable energy sources face challenges in maintaining stable grid voltage and frequency due to variable energy production from sources like solar and wind, leading to undesirable fluctuations.
Innovation Solution
A method for controlling a converter that regulates load power by monitoring AC grid voltage, using a controller to adjust converter output based on measured voltage and load conditions, independent of communication between source and load converters, employing techniques such as Clarke transformation, low-pass filtering, and PI control to stabilize the grid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If load power regulation is achieved by controlling grid voltage magnitude and frequency, then energy consumption can be matched with production, but grid voltage and frequency variations occur when environmental conditions change
Solution Approach 1:
The patent implements a feedback mechanism where the converter continuously monitors grid voltage and adjusts its output power accordingly. When environmental conditions cause voltage deviations, the controller detects these changes and modifies the converter's power output to counteract the voltage variations, thereby maintaining grid stability without requiring frequent voltage and frequency adjustments
Solution Approach 2:
The system enables the converter to autonomously regulate load power by monitoring grid voltage conditions and automatically adjusting its output. This self-regulating capability allows the converter to match energy consumption with production without external control signals or communication between source and load converters, maintaining grid stability through decentralized decision-making
2Reliability
If grid forming control is performed by voltage regulation on the converter side, then voltage amplitude can be maintained, but communication between source and load converters is required which increases system complexity
Solution Approach 1:
The converter is equipped with autonomous control capability that allows it to independently regulate grid voltage by monitoring local voltage conditions and adjusting its output power accordingly. This self-service approach eliminates the need for communication between source and load converters, simplifying the system while maintaining effective voltage control
Solution Approach 2:
The control function is segmented and distributed to individual converters rather than requiring centralized control or inter-converter communication. Each converter independently performs grid forming control based on local measurements, dividing the overall control task into autonomous local decisions that collectively maintain grid stability
Data Source
AI summary
A method for controlling a converter supplying a load is described. The converter is connected to an alternating current (AC) grid supplied by at least one renewable energy source. The method comprises receiving a measured AC grid voltage measured in the AC grid and a measured load voltage measured at an output of the converter. The method further comprises determining a magnitude of a fundamental positive-sequence component of the measured AC grid voltage. The method additionally comprises determining a load voltage reference from the magnitude and from a nominal load voltage reference, wherein the load voltage reference decreases when the magnitude decreases. The method also comprises determining a voltage error by subtracting the measured load voltage from the load voltage reference. The method further comprises controlling an output power of the converter based on the voltage error.