Reactive Power Control for Grid Flicker Prevention
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Solution Overview
Problem
Existing flicker prevention methods using reactive power compensation devices like STATCOM fail to effectively mitigate voltage fluctuations of 6 to 7 Hz caused by distributed power supplies, and inappropriate gain values can even exacerbate flicker.
Innovation Solution
A flicker prevention device and method that includes a power converter, frequency detector, and controller to inject lead or delay reactive power based on system frequency changes, compensating for frequency fluctuations to cancel out reactive power from distributed power supplies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If reactive power control gain of STATCOM is increased to improve flicker suppression, then voltage fluctuation is reduced, but flicker may increase when gain value is inappropriate
Solution Approach 1:
The controller dynamically selects between two control characteristics based on real-time system conditions, making the reactive power control adaptive rather than using a fixed gain value. This dynamic selection ensures appropriate control action for different operating conditions, preventing the flicker amplification problem that occurs with inappropriate fixed gain values while maintaining effective flicker suppression.
Solution Approach 2:
The invention uses feedback from frequency detection to determine which control characteristic to apply. The controller continuously monitors system frequency and switches between control characteristics based on frequency change direction, creating a feedback mechanism that adapts control parameters to current system state. This ensures reliable flicker suppression across varying conditions without the risk of inappropriate gain application.
2Object-affected harmful factors
If lead reactive power is output in response to system frequency increase and delay reactive power in response to decrease, then flicker is suppressed, but control complexity increases due to frequency-based control logic
Solution Approach 1:
The controller implements dynamic switching between two predefined control characteristics based on simple frequency change detection. Rather than implementing complex continuous control logic, the system uses a simplified dynamic approach: detect frequency change direction, select appropriate control characteristic, and apply it. This reduces control logic complexity while maintaining effective flicker suppression through adaptive control.
Data Source
AI summary
A frequency detector detects a system frequency from an AC voltage on an AC power line to which a power conditioner performing system interconnection of a distributed power supply is connected. A power converter is configured to inject lead reactive power or delay reactive power into the AC power line. A controller controls reactive power output from the power converter to output the lead reactive power in response to an increase in the system frequency while outputting the delay reactive power in response to a decrease in the system frequency.