Medium-Voltage PV Inverter Current Sensing for Pre-Grid Short Detection
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Solution Overview
Problem
Existing medium-voltage grid-connected photovoltaic inverter systems require an external current detection circuit to detect grid-connected current, leading to a large size and high cost, and fail to detect short circuits at the medium-voltage side before connection to the grid.
Innovation Solution
A medium-voltage grid-connected photovoltaic inverter system that integrates a current sensor within the medium-voltage switch, allowing for real-time detection of grid-connected current and enabling short circuit protection without the need for an external current detection circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an external current detection circuit is used to detect grid-connected current, then the detection function is achieved, but the system size and cost increase
Solution Approach 1:
The current sensor is integrated directly into the medium-voltage switch, merging the switching function and current detection function into a single component. This eliminates the need for separate external current detection circuits, thereby reducing system size and cost while maintaining reliable grid-connected current detection capability.
2Ease of manufacture
If the current detection circuit is arranged at the low-voltage side, then the detection circuit is protected, but short circuit at the medium-voltage side cannot be detected before connection
Solution Approach 1:
The current sensor is positioned at the medium-voltage side of the switch, enabling current detection before the photovoltaic inverter system connects to the grid. This preliminary detection capability allows the system to identify short circuits at the medium-voltage side before connection occurs, preventing damage while maintaining detection circuit protection through the switch's isolation function.
Data Source
AI summary
A medium-voltage grid-connected photovoltaic inverter system includes: a photovoltaic inverter, a medium-voltage transformer, a medium-voltage switch, and an inverter grid-connected controller. A direct current input terminal of the photovoltaic inverter is connected to a direct current bus. A low-voltage side of the medium-voltage transformer is connected to an alternating current output terminal of the photovoltaic inverter. An input terminal of the medium-voltage switch is connected to a high-voltage side of the medium-voltage transformer, and an output terminal of the medium-voltage switch is configured to be connected to a medium-voltage grid. A current sensor is integrated in the medium-voltage switch to detect a grid-connected current of the photovoltaic inverter system and output a current detection signal.