Parallel Inverter Islanding Detection Without High-Speed Communication
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Solution Overview
Problem
Conventional islanding detection methods for multiple inverters operating in parallel face challenges, particularly in scenarios without communication, leading to poor robustness and failure in detecting islanding states, especially in applications like photovoltaic energy storage and electric vehicles with bi-directional power interaction.
Innovation Solution
An islanding detection system that includes a current detection circuit on the grid side or AC side of one inverter, connected to a controller which determines whether to perform distributed or centralized islanding detection based on grid voltage and current signals, allowing for adaptive detection without relying on high-speed communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional passive islanding detection is used by monitoring voltage and frequency at PCC point, then the detection method is simple, but the non-detection zone is large leading to poor detection reliability
Solution Approach 1:
The patent combines passive islanding detection (monitoring voltage and frequency at PCC) with active islanding detection (frequency shift and reactive power injection methods) into a unified detection system. This merging allows the system to leverage both the simplicity of passive detection and the high reliability of active detection, eliminating the large non-detection zone while maintaining ease of implementation.
Solution Approach 2:
The patent changes the detection parameters by introducing active injection signals (frequency shifts and reactive power injections) into the system. These parameter changes enable the detection system to identify islanding conditions that passive monitoring alone cannot detect, thereby reducing the non-detection zone and improving overall detection reliability.
2Reliability
If synchronous injection method with master controller is used for multiple inverters, then islanding detection synchronization is achieved, but high-speed communication is required increasing system complexity
Solution Approach 1:
The patent extracts the communication requirement from the islanding detection system by implementing asynchronous injection detection. Each inverter independently performs detection without needing to communicate with a master controller, eliminating the high-speed communication infrastructure while maintaining detection effectiveness through individual inverter autonomy.
Solution Approach 2:
Each inverter in the parallel system performs islanding detection independently using its own local measurements and control capabilities. This self-service approach allows inverters to autonomously detect islanding conditions without relying on external communication systems, thereby reducing system complexity while maintaining detection reliability.
3Measurement precision
If high-speed communication bus is used for real-time synchronization, then detection accuracy is improved, but system cost and complexity increase
Solution Approach 1:
The patent replaces the mechanical communication infrastructure (high-speed communication buses and master controllers) with an electronic-based autonomous detection mechanism. Each inverter uses its own electronic sensors and processors to independently detect islanding conditions, achieving high measurement precision without the need for complex communication hardware.
4Adaptability or versatility
If conventional islanding detection method is used in parallel systems without communication capability, then system applicability is improved, but detection reliability deteriorates due to inability to synchronize
Solution Approach 1:
The patent segments the islanding detection function into independent units at each inverter, eliminating the need for inter-inverter communication. Each inverter independently monitors its own operating conditions and detects islanding events autonomously, thereby maintaining high detection reliability while enabling broad system applicability including scenarios without communication capabilities.
Data Source
AI summary
An islanding detection system and method for multiple inverters operating in parallel, wherein the multiple inverters at least comprises a first inverter and a second inverter connected in parallel. The islanding detection system comprises a current detection circuit arranged on a grid side or an AC side of the second inverter; and a controller connected to the current detection circuit and the first inverter. The controller determines whether to perform distributed islanding detection or centralized islanding detection on the first inverter and the second inverter according to a grid voltage signal and a current detection signal of the current detection circuit. By recognizing the islanding detection mode of the second inverter, matching it with typical islanding detection modes preset in a library, and determining to perform a distributed or centralized islanding detection according to matching results, the application improves the success ratio of islanding detection.