Inverter Mode Switching via Junction Box Auxiliary Switch Detection
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Solution Overview
Problem
Inverters fail to switch to the off-grid mode when externally connected to a junction box, even if the relay in the junction box is opened, due to synchronization issues between the inverter's relay and the junction box's switches.
Innovation Solution
Incorporating a detection circuit to detect the state of an auxiliary switch in the junction box and a controller to synchronize the inverter's operation mode with the state of the auxiliary switch, allowing seamless switching between grid-connected and off-grid modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the inverter is externally connected to a junction box to achieve high current or facilitate wiring, then the ease of operation and adaptability are improved, but the reliability of mode switching deteriorates because the inverter fails to detect grid islanding state when the junction box relay is opened
Solution Approach 1:
The patent introduces an auxiliary switch as an intermediary component in the junction box that provides a separate detection path for grid islanding state. This auxiliary switch works in conjunction with the existing power switch to enable the inverter to reliably detect when the grid is islanded, even when the junction box relay is opened. The auxiliary switch serves as a mediator that bridges the detection gap created by the external junction box connection.
2Adaptability or versatility
If a relay is used in the junction box to control power flow, then the adaptability for different connection scenarios is improved, but the device complexity increases due to synchronization requirements between multiple switches
Solution Approach 1:
The auxiliary switch is designed to serve multiple functions: it acts as a detection element for grid islanding state, provides a synchronization signal to the inverter, and works cooperatively with the power switch to control the overall power flow. This multi-functionality reduces the need for separate dedicated components for each function, thereby managing complexity while maintaining versatility.
Solution Approach 2:
The system implements a feedback mechanism where the inverter detects the state of the auxiliary switch and uses this information to determine the grid islanding state and adjust its operation mode accordingly. This feedback loop enables automatic mode switching without requiring complex manual synchronization procedures, reducing operational complexity while maintaining adaptability.
Data Source
AI summary
An inverter, a method for controlling an operation mode, and an inverter system are provided. The inverter includes a detection circuit and a controller. The detection circuit is configured to detect a state of an auxiliary switch in a junction box, and send the state of the auxiliary switch to the controller. The controller is configured to determine an operation mode of the inverter based on the state of the auxiliary switch. The state of the auxiliary switch is synchronized with a state of a power switch in a first switch assembly. The state of the power switch in the first switch assembly is used to indicate a state of a power grid.