Five-Level Half-Bridge Inverter Topology for Leakage Current Elimination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional 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-cost magnetic components, 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 system costs by eliminating the need for double AC filtering inductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a full bridge inverter circuit is used to achieve high voltage utilization ratio, then voltage utilization is improved, but cost increases due to double AC filtering inductors and difficulty in canceling leakage current
Solution Approach 1:
The patent segments the DC voltage into multiple levels (five-level output) using series capacitors and switching circuits, achieving high voltage utilization without requiring a full bridge configuration. This segmentation allows the inverter to operate efficiently at higher voltage levels while reducing the need for additional filtering inductors.
Solution Approach 2:
The patent merges the voltage multiplication function and the inverter function into a single integrated circuit structure. The series capacitors and switching circuits simultaneously achieve voltage boosting and AC output generation, eliminating the need for separate voltage boosting circuits and reducing overall system cost.
2Device complexity
If a half bridge inverter circuit is used to reduce cost with single AC filtering inductor, then system cost is reduced, but voltage utilization ratio drops to half of full bridge
Solution Approach 1:
The patent transitions from a traditional two-level half-bridge structure to a five-level inverter structure by adding series capacitors and multiple switching stages. This dimensional expansion in voltage levels allows the circuit to achieve high voltage utilization (comparable to full bridge) while maintaining the cost advantages of a simplified topology.
3Use of energy by moving object
If additional circuitry is added to boost input voltage in half bridge inverter, then voltage utilization is improved, but system efficiency decreases and cost increases
Solution Approach 1:
The patent incorporates voltage boosting action within the normal switching operation sequence. The series capacitors are charged and discharged as part of the regular inverter switching cycles, achieving voltage multiplication without requiring separate boosting phases or additional energy conversion steps that would reduce efficiency.
4Object-affected harmful factors
If conventional H4 full bridge circuit is used to reduce leakage current, then leakage current is reduced, but cost increases due to non-common magnetic cores and double AC filtering inductors
Solution Approach 1:
The patent extracts and eliminates the need for double AC filtering inductors by designing a topology that inherently provides better common-mode noise rejection. The five-level structure with series capacitors naturally filters high-frequency leakage currents, removing the requirement for additional expensive magnetic components.
Data Source
AI summary
A single phase five-level inverter topology comprising a half-bridge inverter circuit with a floating capacitor which outputs five mutually different voltage levels including zero, wherein both the system cost and the size is reduced, the leakage current is eliminated substantially and high efficiency is achieved by using five-level half-bridge structure with only one AC filtering inductor. A three-phase five-level inverter topology wherein the voltage utilization is twice that of the present three-phase five-level half-bridge inverter under the same operating conditions; the AC filtering inductance is smaller than that of the three-level half-bridge inverter; the DC link mid-point voltage can be balanced without additional circuitry.