Inverter Filter Circuit With Common Mode Choke for Leakage Current
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Solution Overview
Problem
In grid-connected photovoltaic power generation systems, the leakage current caused by a through current loop involving photovoltaic panels, inverters, and the power grid leads to safety issues and reduced conversion efficiency due to the non-isolated architecture of most current inverters.
Innovation Solution
A power conversion circuit with a switching network, control circuit, filter circuit, direct current side circuit, and alternating current side circuit, incorporating a common mode choke and differential mode filter capacitors, which reduces common mode leakage current by providing a low impedance loop for common mode currents, and employs hybrid modulation control to improve conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a non-isolated architecture is used to reduce inverter costs, then device complexity is reduced, but common mode leakage current increases causing safety issues and reduced conversion efficiency
Solution Approach 1:
The patent introduces a common mode choke as an intermediary component in the filter circuit. This choke provides a low impedance path for common mode currents, effectively diverting leakage current away from the harmful through-current loop formed by the photovoltaic panel, inverter, and power grid. The common mode choke acts as a mediator that maintains the simple non-isolated architecture while eliminating the harmful leakage current effect.
Solution Approach 2:
The patent extracts the common mode current path from the main power conversion path by introducing a separate low impedance回路 through the common mode choke. This separation allows the common mode leakage current to be handled independently through the choke's low impedance path, preventing it from flowing through the harmful earth ground loop while maintaining the overall simplicity of the non-isolated architecture.
2Productivity
If a through current loop is formed by photovoltaic panel, inverter, and power grid, then power conversion is enabled, but leakage current causes personal safety problems and increased inverter loss
Solution Approach 1:
The common mode choke serves as an intermediary that provides an alternative low impedance path for common mode currents. This mediator component allows the power conversion function to continue through the main circuit while diverting the harmful leakage current through the choke's low impedance path, thereby reducing inverter losses and eliminating safety hazards without affecting power conversion productivity.
3Object-affected harmful factors
If common mode filter capacitors are connected to direct current side circuit through low impedance circuits, then common mode leakage current is reduced, but device complexity increases
Solution Approach 1:
The patent merges the common mode filtering function with the existing filter circuit components. The common mode filter capacitors are integrated into the filter circuit and connected through low impedance circuits to the direct current side circuit, combining multiple functions (filtering and leakage current reduction) into a unified circuit structure. This merging approach reduces device complexity compared to adding separate independent filtering systems.
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 reduces common mode leakage current and enhances conversion efficiency of the inverter, addressing safety and performance issues in grid-connected photovoltaic power generation systems.
Implementation Method 1
the common mode choke includes a third winding and a fourth winding... both a first end of the first winding and a first end of the second winding are separately connected to the switching network, a second end of the first winding is connected to a first end of the third winding, and a second end of the second winding is connected to a first end of the fourth winding
Implementation Method 2
the filter circuit includes a first power inductor, a common mode choke, a first differential mode filter capacitor, a first common mode filter capacitor, and a second common mode filter capacitor... before the first differential mode filter capacitor is connected to the common mode choke in the filter circuit, a loss caused when a high-frequency current component flows into the common mode choke can be effectively avoided
Data Source
AI summary
A power conversion circuit includes a switching network, a control circuit, a filter circuit, and a direct current side circuit; and the filter circuit includes a first power inductor, a common mode choke, a first differential mode filter capacitor, a first common mode filter capacitor, and a second common mode filter capacitor. The first power inductor includes a first winding and a second winding, and the common mode choke includes a third winding and a fourth winding; a first end of the first winding and a first end of the second winding are separately connected to the switching network, a second end of the first winding and a second end of the second winding are respectively connected to a first end of the third winding and a first end of the fourth winding.