T-Type Multilevel Inverter Bus Layout for Mutual Inductance Cancellation
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Solution Overview
Problem
High-voltage and high-power multilevel inverters used in electrified vehicles face issues such as capacitor voltage imbalance and overvoltage stress due to neutral current oscillations, as well as parasitic inductance leading to ringing and electromagnetic interference.
Innovation Solution
A system and method for mutual inductance cancellation in a multi-phase power inverter using T-type multilevel power converters, where the positive DC power bus, negative DC power bus, and neutral bus are arranged in a configuration that minimizes parasitic inductance by coupling positive and negative mutual inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If T-type multilevel power converters use neutral point connection to stacked DC-link capacitor, then zero voltage vector capability is achieved, but capacitor voltage imbalance and overvoltage stress occur due to neutral current oscillation
Solution Approach 1:
The patent extracts the neutral point connection from the conventional T-type inverter topology, creating a neutral-point-less multilevel inverter. This removes the source of neutral current oscillation while preserving the ability to generate zero voltage vectors through alternative switching state combinations, thus eliminating capacitor voltage imbalance without sacrificing operational capability.
Solution Approach 2:
Instead of using the traditional neutral point connection method to achieve zero voltage vectors, the patent inverts the approach by using complementary switching states of the semiconductor switches to create equivalent zero voltage vectors. This alternative method achieves the same functional goal without the harmful neutral current oscillation.
2Object-affected harmful factors
If power loop size is reduced to minimize parasitic inductance, then ringing and EMI are reduced, but circuit topology complexity increases
Solution Approach 1:
The patent merges the positive and negative DC power buses with the neutral bus in a integrated bus structure. This merging of bus functions creates compact current loops that minimize parasitic inductance and reduce ringing and EMI, while the modular bus design maintains circuit clarity and reduces overall complexity.
Solution Approach 2:
The patent transitions from planar bus arrangement to a three-dimensional stacked configuration where power buses and neutral buses are vertically integrated. This dimensional change allows for shorter current paths and reduced loop areas, minimizing parasitic inductance without increasing planar complexity.
3Productivity
If switching frequency is increased to improve power density, then productivity increases, but parasitic inductance effects are amplified causing more severe ringing
Solution Approach 1:
The patent incorporates mutual inductance cancellation features directly into the bus topology design before switching operations occur. The bus structure is configured to generate opposing magnetic fields that cancel each other, creating preliminary anti-action against the parasitic inductance effects that would be amplified at high switching frequencies, thus preventing ringing before it occurs.
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 proposed solution effectively reduces parasitic inductance, minimizing ringing and electromagnetic interference, and enhancing the reliability and efficiency of high-voltage and high-power multilevel inverters in electrified vehicles.
Implementation Method 1
System and method for mutual inductance cancellation for multi-phase power inverters... topology that reduces parasitic inductance within the multi-phase power inverter
Data Source
AI summary
A multi-phase power inverter for an electric propulsion system includes a plurality of T-type multilevel power converters arranged between a high-voltage direct current (DC) power supply and an electric machine. Each of the plurality of T-type multilevel power converters is a solid-state integrated circuit that includes a positive DC power bus, a negative DC power bus, a neutral bus, and a plurality of semiconductor switches disposed in a stacked arrangement. The plurality of semiconductor switches is interconnected via the positive DC power bus, the negative DC power bus, and the neutral bus.