AC/DC Converter Stage Zero-State Switching for Common Mode Noise
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Solution Overview
Problem
Converter systems with a series input structure experience high common mode voltages due to parasitic capacitances, leading to noise, electromagnetic compatibility issues, and power loss, particularly in AC/DC converter stages with IGBTs, causing gate driver misfiring and ground potential drift.
Innovation Solution
Incorporating a controllable bidirectional switch in the AC/DC converter stage to create a zero state where no current flows through the circuit branch, thereby eliminating common mode voltage and improving common mode performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If converter units are closely arranged to meet high power density requirements, then productivity is improved, but parasitic capacitances increase causing high common mode voltages and currents
Solution Approach 1:
A common mode choke is introduced as an intermediary component in the circuit path to counteract the harmful common mode voltages and currents generated by parasitic capacitances. The choke acts as a mediator that filters out the common mode interference while allowing normal operation, thus resolving the contradiction between high power density and reduced common mode voltage without requiring increased spacing between converter units.
2Reliability
If solid insulation material is provided between packaged converter units, then reliability is improved through insulation, but parasitic capacitances are generated between AC/DC converter stage and ground potential enclosure
Solution Approach 1:
The common mode choke serves as an intermediary element that compensates for the parasitic capacitances inevitably introduced by solid insulation materials. By placing the choke in the current path, it counteracts the capacitive coupling between the AC/DC converter stage and the grounded enclosure, maintaining both insulation reliability and electromagnetic compatibility.
Solution Approach 2:
The invention changes the electrical parameters of the circuit by introducing the common mode choke, which modifies the impedance characteristics to counteract the parasitic capacitance effect. This parameter change allows the system to maintain reliable insulation while minimizing the harmful effects of parasitic capacitance on common mode voltage.
3Object-generated harmful factors
If common mode voltages are reduced by increasing spacing between converter units, then common mode performance is improved, but power density decreases
Solution Approach 1:
Rather than increasing physical spacing, the invention introduces a common mode choke as an intermediary component that actively counteracts common mode currents. This allows converter units to remain closely spaced for high power density while the choke filters out the common mode interference, achieving both high productivity and low common mode current.
4Loss of energy
If IGBTs are used in AC/DC converter stage, then power conversion efficiency is improved, but gate driver misfiring occurs due to noise and EMI from common mode currents
Solution Approach 1:
The common mode choke acts as a protective intermediary that filters out the high-frequency noise and EMI generated by common mode currents before they can reach the IGBT gate drivers. This allows the system to maintain the energy efficiency benefits of IGBTs while protecting the gate drivers from misfiring due to electromagnetic interference.
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 noise and power loss, enhancing electromagnetic compatibility and stability in AC/DC converter stages without increasing costs or complexity.
Implementation Method 1
the provision of the solid insulation material may generate parasitic capacitances between the AC/DC converter stage and the galvanically isolated DC/DC converter stage, and the metal enclosure kept at ground potential
Data Source
AI summary
An AC/DC converter stage for a converter system with an input series structure. The AC/DC converter stage includes two input terminals for inputting an AC input voltage and at least a first circuit branch with at least two switches that are electrically connected in series at a first connection point, where a first input terminal of the two input terminals is electrically connected to the first connection point of the first circuit branch. At least one first electrical storage provides a DC output voltage and is electrically connected in parallel to the first circuit branch. At least one controllable bidirectional switch is electrically connected between the two input terminals.