Power Conversion Device Islanding Detection
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Solution Overview
Problem
Existing power conversion devices for grid connection face delays in islanding operation detection due to the interaction between reactive power injection for constant power factor control and islanding operation detection, leading to inaccurate detection.
Innovation Solution
A power conversion device with a voltage detection unit, current detection unit, and a constant power factor control unit that performs constant power factor control by injecting reactive power based on detected voltage and current values, while an islanding operation detection unit calculates frequency variations to determine islanding mode, with a reference time period longer than the islanding operation detection process to minimize interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reactive power is injected for constant power factor control, then the power factor is maintained at a preset value, but the islanding operation detection accuracy deteriorates due to interference with frequency variation detection
Solution Approach 1:
The patent segments the reactive power injection into two distinct components: a first reactive power for constant power factor control and a second reactive power for islanding operation detection. By separating these functions and controlling them independently with different timing characteristics, the interference between power factor control and islanding detection is reduced, thereby improving detection accuracy while maintaining reliable power factor control.
2Speed
If different control response properties are employed for constant power factor control and islanding operation detection, then detection delay is suppressed, but the interaction between reactive power injections still causes detection delays
Solution Approach 1:
The patent applies preliminary action by injecting the second reactive power (for islanding detection) in advance before the first reactive power (for power factor control). This timing arrangement ensures that the frequency variation caused by the second reactive power is established before the first reactive power injection begins, allowing the islanding detection to proceed without being obscured by the power factor control effects.
Data Source
AI summary
A power conditioner that includes a voltage detection unit that detects a voltage value of output voltage of the power conditioner, a current detection unit that detects a current value of output current of the power conditioner, and a constant power factor control unit that performs a constant power factor control process of a power factor of output power of the power conditioner to become a preset power factor command value. The constant power factor control unit performs the constant power factor control process using the detected voltage and current values at a second moment in past, the second moment in past being earlier than a first moment by a preset reference time period, and the first moment being a moment at which the voltage and current values are acquired for performing the constant power factor control process.