Reactive Power Dispatch Limits for Renewable Generator Voltage Control
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Solution Overview
Problem
Renewable energy generators face challenges in maintaining voltage levels within a specified dead-band due to reactive power control, leading to potential disruptions in power networks, especially in weak grid interconnections.
Innovation Solution
A method and controller system that determines generator-based and voltage-based reactive power limits for renewable energy generators, ensuring operation within physical and voltage constraints by monitoring local voltage levels and adjusting reactive power dispatch to prevent exceedances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reactive power is supplied to support voltage recovery during drops, then voltage levels are improved, but local voltage levels may rise out of the dead-band causing emergency measures to be implemented
Solution Approach 1:
The patent applies local quality by determining individual voltage-based reactive power limits for each generator based on its specific terminal voltage conditions. The controller monitors local voltage levels at each generator terminal and adjusts reactive power limits accordingly, allowing different generators to operate with customized limits that reflect their local voltage conditions rather than applying a uniform limit across the entire power plant.
Solution Approach 2:
The patent implements dynamics by making reactive power limits adaptive rather than static. The voltage-based reactive power limits are continuously adjusted based on real-time terminal voltage measurements. When terminal voltage approaches dead-band boundaries, the limits dynamically reduce to prevent voltage excursions, and when voltage is stable within the dead-band, limits are relaxed to allow greater reactive power support capability.
2Reliability
If reactive power exchange is controlled to meet power network requirements, then voltage levels are maintained within dead-band, but small changes cause large variations in local voltage in weak grid interconnections
Solution Approach 1:
The patent applies segmentation by dividing the power plant into individual generator units, each with its own voltage-based reactive power limits determined independently based on local terminal voltage conditions. Rather than controlling reactive power centrally without regard to individual generator conditions, the system segments the control to account for local voltage sensitivities at each generator, particularly important in weak grid interconnections where small reactive power changes can cause large voltage variations.
Data Source
AI summary
Aspects of the present invention relate to a method for controlling a plurality of renewable energy generators. The method comprises: determining preliminary reactive power set points for the generators based on a reactive power reference value; determining generator-based and voltage-based reactive power limits for the generators; generating dispatch signals for requesting reactive power from the generators based on the preliminary set point and the limits; and dispatching the dispatch signals to the generators. The generator-based reactive power limits correspond to the reactive power capability of the generator. The voltage-based limits are determined by: determining a terminal voltage of the generator; comparing the determined terminal voltage to a voltage limit; and determining the voltage-based reactive power limit based on the comparison.