Backfeed Soft-Start Circuit for PV Inverter Inrush Suppression
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Solution Overview
Problem
Conventional photovoltaic inverters face issues with inrush currents due to unidirectional DC/DC converters, leading to damage and operational challenges during backfeed current testing of photovoltaic modules, especially in high-voltage environments.
Innovation Solution
A backfeed soft-start circuit with branch switches and a primary switching switch is connected between the DC/AC converter and the photovoltaic array, allowing selective control of branch switches and incorporating current-limiting components to suppress surge currents, ensuring safe and efficient testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a unidirectional DC/DC converter is used in the string photovoltaic inverter, then cost is reduced, but inrush current damages the inverter during backfeed current testing
Solution Approach 1:
The patent introduces a bidirectional DC/DC converter as an intermediary device between the photovoltaic modules and the grid. This converter enables controlled bidirectional power flow, allowing the system to safely manage backfeed currents during testing while maintaining cost-effectiveness. The bidirectional converter acts as a mediator that prevents direct inrush current damage to the inverter by controlling the current path.
Solution Approach 2:
The patent implements dynamic switching control of the bidirectional DC/DC converter to adapt the system's operational mode. During normal operation, the converter operates in one direction for power generation, while during testing, it dynamically switches to bidirectional mode to enable safe backfeed current flow. This dynamic adaptability resolves the contradiction by allowing the system to maintain reliability during testing without permanently increasing cost.
2Productivity
If multiple photovoltaic modules are tested simultaneously in a string photovoltaic inverter, then testing efficiency is improved, but device size and operation difficulty increase
Solution Approach 1:
The patent segments the photovoltaic array into multiple independently controllable modules, each with its own branch switch connected to the bidirectional DC/DC converter. This segmentation allows selective testing of individual modules or groups of modules without requiring all modules to be tested simultaneously, thereby maintaining testing efficiency while reducing the operational complexity and device size requirements.
3Productivity
If multiple photovoltaic modules are tested simultaneously, then testing productivity is improved, but operation difficulty and security risk increase
Solution Approach 1:
The patent incorporates feedback control mechanisms through the bidirectional DC/DC converter that continuously monitors the operational status of each photovoltaic module during testing. The converter receives feedback signals from each module and automatically adjusts the current distribution and switching control accordingly. This feedback system enables multiple modules to be tested simultaneously while maintaining ease of operation, as the system self-regulates based on real-time module conditions without requiring complex manual intervention.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively suppresses inrush currents, protecting the inverter from damage and enabling flexible configuration of photovoltaic modules for testing while maintaining energy efficiency.
Implementation Method 1
a backfeed current generated through reverse rectification of the DC/AC converter
Implementation Method 2
converting solar radiation energy into electrical energy based on a photovoltaic effect of a semiconductor material
Data Source
AI summary
A backfeed soft-start circuit for a photovoltaic inverter is provided. The backfeed soft-start circuit includes a plurality of branch switches. A solar photovoltaic array includes a plurality of photovoltaic modules, where the plurality of branch switches are in a one-to-one correspondence with the plurality of photovoltaic modules, and when the plurality of branch switches are turned on, the corresponding photovoltaic modules are connected to the backfeed soft-start circuit; and a primary switching switch. The branch switches is connected to a corresponding photovoltaic module, and the primary switching switch. The primary switching switch is turned on after the branch switch is turned on.