Parallel Inverter Wave Blocking for DC Bus Short-Circuit Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In photovoltaic power generation systems, when an inverter is short-circuited, the direct current bus voltage of non-faulty inverters can increase, potentially leading to component damage and fault expansion due to direct current bus overvoltage.
Innovation Solution
A photovoltaic system and method that includes a controller and two groups of inverters, where the controller detects a circulating current between inverters connected in parallel and performs wave blocking on all inverters connected in parallel to the faulty inverter, thereby preventing further damage and ensuring system safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple inverters are connected in parallel to improve power capacity, then the power capacity of the inverter system is improved, but the risk of fault expansion increases when a direct current bus capacitor is short-circuited
Solution Approach 1:
The controller detects circulating current between parallel-connected inverters and identifies short-circuit faults before they can cause widespread damage. By performing preliminary detection and triggering wave blocking protection immediately when circulating current exceeds thresholds, the system prevents fault expansion to other inverters while maintaining the parallel connection configuration for high power capacity
Solution Approach 2:
The system continuously monitors circulating current between parallel inverters and uses this feedback to detect short-circuit conditions. When the circulating current exceeds predetermined thresholds, the controller provides feedback to trigger wave blocking protection, creating a closed-loop protection mechanism that enables high-power parallel operation while automatically responding to fault conditions
2Reliability
If wave blocking is performed on all parallel-connected inverters when circulating current exceeds threshold, then the protection effectiveness is improved, but the system availability decreases due to shutdown of non-faulty inverters
Solution Approach 1:
The wave blocking protection mechanism applies preliminary anti-action by preemptively shutting down all parallel-connected inverters when circulating current exceeds thresholds. This prevents the short-circuit fault from expanding to other inverters through the parallel connection, sacrificing temporary availability of non-faulty inverters to ensure long-term system reliability and prevent catastrophic failures
Data Source
Figure 1
Figure 2
Figure 3
AI summary
This application provides a photovoltaic system, a protection method, and an inverter system. The system includes a controller and two groups of inverters. The two groups of inverters include a positive inverter group and a negative inverter group. The positive inverter group includes at least two inverters: a first inverter and a third inverter. The negative inverter group includes at least two inverters: a second inverter and a fourth inverter. Alternating current output ends of the first inverter and the third inverter are connected in parallel. Direct current input ends of the first inverter and the second inverter are connected in series. Alternating current output ends of the second inverter and the fourth inverter are connected in parallel. Direct current input ends of the third inverter and the fourth inverter are connected in series. The controller obtains a circulating current between at least two inverters whose alternating current output ends are connected in parallel; and when the circulating current is greater than a preset current threshold or a rising rate of the circulating current is greater than a preset rate, controls all inverters whose corresponding alternating current output ends are connected in parallel to undergo wave blocking. This solution can accurately determine that a direct current bus is short-circuited and perform the wave blocking to avoid fault expansion.