Five-Level Inverter Topology Eliminates Boost Circuit
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Solution Overview
Problem
Non-isolated inverters in photovoltaic systems face challenges with high frequency and common mode current, leading to electromagnetic interference and safety concerns, while existing five-level inverters require extra boosting circuits, increasing cost and reducing efficiency.
Innovation Solution
A five-level topology unit with a half-bridge inverter module that uses a floating capacitor and bidirectional switches, eliminating the need for an extra boosting circuit, reducing cost and enhancing efficiency by using only one AC filtering inductor and minimizing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a non-isolated inverter is used to eliminate transformer, then cost is reduced and power density is improved, but high frequency and common mode current causes electromagnetic interference and safety concerns
Solution Approach 1:
The inverter is divided into multiple independent H-bridge modules, each capable of operating autonomously. This segmentation allows the system to function as a non-isolated inverter (reducing cost and increasing power density) while each module's independent operation helps control common mode current and electromagnetic interference through balanced switching patterns.
2Device complexity
If a full bridge inverter circuit is used, then input voltage boosting is not needed, but high frequency leakage current cannot be substantially cancelled due to parasitic factors
Solution Approach 1:
The parasitic capacitances and inductances that normally cause high frequency leakage current are utilized beneficially. By carefully controlling the switching sequences of the H-bridge modules and using the parasitic elements as part of the filtering mechanism, the system converts these harmful parasitic factors into useful components that help suppress common mode current and electromagnetic interference.
3Object-generated harmful factors
If a half bridge or mid-point clamped inverter circuit is used, then leakage current is substantially eliminated, but an extra circuit is needed to boost input voltage which lowers efficiency
Solution Approach 1:
The system dynamically switches between different operating modes and configurations of the H-bridge modules to achieve voltage boosting without requiring a separate boosting circuit. By dynamically adjusting which modules operate in which configurations, the system eliminates leakage current while maintaining high efficiency through the inherent voltage multiplication capability of the modular architecture.
4Object-generated harmful factors
If conventional H4 full bridge circuit improvements are made to reduce high frequency leakage current, then industry standard is met, but cost increases significantly
Solution Approach 1:
The H-bridge modules are designed with universal functionality that serves multiple purposes: they provide the main power conversion function, act as their own voltage boosting mechanism, and simultaneously function as filtering elements to reduce high frequency leakage current. This multi-functionality eliminates the need for separate filtering components and boosting circuits, meeting industry standards while keeping costs low.
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 achieves high efficiency and low cost by eliminating the need for an extra boosting circuit, reducing the complexity of the inverter design and enhancing safety by minimizing electromagnetic interference.
Implementation Method 1
a floating capacitor that is charged by the first DC power supply or the second DC power supply
Implementation Method 2
each semiconductor switch is connected in reverse parallel with a diode... the term 'bidirectional switch' as used herein is intended to refer to a semiconductor switch connected in reverse parallel with a diode
Data Source
AI summary
Five-level topology units and inverters based on the five-level inverter units without a boost circuit. Cost is reduced by using only one AC filtering inductor and high efficiency is achieved in the absence of an extra boosting circuit. Leakage current is eliminated substantially by using a half-bridge inverter module. A five-level inverter including a five-level topology unit without a boost circuit to raise the input voltage is able to output the same AC power as a five-level full bridge inverter under the same working condition.