Power Semiconductor Module with Neutral Point for Surge Voltage Reduction
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Solution Overview
Problem
In multi-level power conversion systems, the surge voltage applied to IGBTs during switching increases with current rating, limiting module capacity and requiring high-voltage rated chips, which increases module size and cost, and parallel connections necessitate derating to balance current, restricting capacity expansion.
Innovation Solution
A power semiconductor module configuration where IGBTs and diodes are housed in a single package with specific terminal arrangements, allowing internal commutation to bypass external wires, reducing wire inductance and surge voltage, and enabling higher current ratings without significant size or cost increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the current rating of IGBTs is increased, then the power conversion capacity is improved, but the surge voltage during switching increases, requiring higher-voltage rated chips which increases module size and cost
Solution Approach 1:
The patent segments the current path by introducing a neutral point and dividing the three-phase circuit into multiple independent current loops. Each IGBT operates in a dedicated loop with controlled wire inductance, preventing surge voltage from affecting other phases. This segmentation allows higher current ratings without proportional increases in surge voltage, enabling greater power capacity without increasing module size.
Solution Approach 2:
The patent introduces a neutral point as an intermediary element that serves as a common reference for all three phases. This neutral point enables independent current return paths for each phase, effectively decoupling the surge voltage effects between phases. By using the neutral point as a mediator, the system can handle higher currents while maintaining controlled voltage stress on individual IGBTs, thus avoiding the need for larger high-voltage rated chips.
2Power
If parallel connections are used to expand capacity, then the power conversion capacity is improved, but current derating is required to balance current distribution, restricting capacity expansion
Solution Approach 1:
The patent segments the power conversion system into three independent single-phase units, each with its own neutral point connection. This segmentation allows each phase to operate independently with balanced current distribution, eliminating the need for derating when combining phases. The segmented architecture enables straightforward capacity expansion by simply adding more independent phase modules without complex current balancing requirements.
3Reliability
If wire inductance is reduced to lower surge voltage, then the switching performance is improved, but the module complexity increases with more internal wire arrangements
Solution Approach 1:
The patent merges the current return paths of all three phases at a common neutral point within the module. This merging eliminates the need for separate return paths for each phase, significantly reducing the total wire length and internal inductance. By combining the neutral points and using a common reference, the design achieves low surge voltage without increasing complexity, as the neutral point structure naturally organizes the wire arrangements.
Data Source
AI summary
In some aspects of the invention, a power semiconductor module is applied to a multi-level converter circuit with three or more levels of voltage waveform. A first IGBT, a diode whose cathode is connected to the emitter of the first IGBT, and a second IGBT having reverse blocking voltage whose emitter is connected to the emitter of the first IGBT, are housed in one package, and each of the collector of the first IGBT, the collector of the second IGBT, the connection point of the emitter of the first IGBT and the emitter of the second IGBT, and the anode of the diode, is an external terminal.