Five-level inverter topology reduces leakage current and cost
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Solution Overview
Problem
Current photovoltaic inverter systems face challenges with high frequency leakage currents, leading to electromagnetic interference and increased costs due to the need for additional circuitry and high AC filtering inductance, particularly in transformerless designs.
Innovation Solution
A five-level inverter topology is introduced, utilizing a half-bridge inverter circuit with a floating capacitor and bidirectional switches, which outputs five distinct voltage levels including zero, reducing leakage currents and eliminating the need for double AC filtering inductors, thereby reducing system cost and size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a full bridge inverter circuit is used to eliminate high frequency leakage current, then leakage current is reduced, but system cost increases due to double AC filtering inductors and non-common magnetic cores
Solution Approach 1:
The patent segments the inverter circuit into modular units with shared magnetic cores. Instead of using separate AC filtering inductors for each phase, the invention uses a single three-phase AC filtering inductor with shared magnetic core, dividing the filtering function across phases while reducing component count and cost.
Solution Approach 2:
The patent merges the AC filtering functions of multiple phases into a single shared magnetic core structure. The three-phase AC filtering inductor combines the filtering capabilities that would otherwise require separate inductors, reducing system cost while maintaining leakage current elimination performance.
2Device complexity
If a half bridge inverter circuit is used to reduce system cost with single AC filtering inductor, then system cost decreases, but voltage utilization ratio is reduced to half
Solution Approach 1:
The patent transitions from a single-level bridge structure to a five-level inverter topology. By adding intermediate voltage levels through series-connected switching devices and capacitors, the system achieves higher voltage utilization ratio while maintaining the single AC filtering inductor configuration. The five-level structure provides five distinct output voltage levels (±Vdc, 0, ±Vdc/2), effectively utilizing the available DC voltage.
3Device complexity
If three-level half-bridge inverter is used for three-phase system, then system is simplified, but voltage utilization ratio equals one and additional circuitry is needed
Solution Approach 1:
The patent employs dynamic switching strategies in the five-level inverter topology, where switching devices are controlled to dynamically select from five available voltage levels. This dynamic control enables the system to achieve voltage utilization ratio greater than one by optimally utilizing the available DC voltage through coordinated switching of multiple semiconductor devices.
Data Source
AI summary
A five-voltage level inverter topology circuit and a three-phase five-voltage level inverter topology circuit, suitable for use with two series-connected direct current (DC) power sources, include a half-bridge inverter circuit having a first circuit module and a second circuit module. The half-bridge inverter circuit outputs five voltage levels including a 0V level. The five-voltage level inverter topology circuit has a five-voltage level half-bridge structure, and only requires an alternating current (AC) filtering inductor, thereby reducing system cost and size, removing leakage current, and providing high efficiency.