Multi-Leg Three-Phase Inverter Control for Balanced Leg Lifetime
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Solution Overview
Problem
Inverter systems with three-phase inverters face challenges in maintaining balanced operational lifetimes of their legs, leading to premature failure and costly replacements, as the introduction of a fourth leg for replacement causes imbalance in the remaining lifetime of the other two legs.
Innovation Solution
The implementation of a four or more leg inverter system with a controller that uses space vector pulse width modulation (SVPWM) strategies and temperature sensors to select and balance the operation of legs, ensuring equal operation time and replacing legs based on junction temperature information, thereby extending the operational lifetime and reducing the need for frequent replacements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fourth leg is added to replace a failed leg, then the inverter can continue operating, but the remaining lifetime of the other legs becomes unbalanced
Solution Approach 1:
The patent combines multiple legs into a single inverter system with shared control and switching mechanisms. The controller manages multiple legs (at least three, preferably four) as an integrated system, allowing them to share operational load and extend individual leg lifetimes through coordinated switching sequences and null vector states.
Solution Approach 2:
The patent implements dynamic leg selection and switching where the controller actively manages which legs are operational at any given time. By using space vector PWM strategies and null vector states, the system dynamically rotates through different leg combinations, ensuring balanced usage and preventing any single leg from reaching failure point before others.
2Duration of action of moving object
If the entire inverter is replaced to maintain balanced leg lifetimes, then lifetime balance is maintained, but cost and waste increase
Solution Approach 1:
Instead of discarding functional legs when one fails, the patent recovers and continues using them by integrating them into a multi-leg system. The controller manages the remaining functional legs alongside newly added legs, rotating through different combinations to extend the operational life of all legs and avoid premature disposal of still-functional components.
Solution Approach 2:
The patent creates a universal inverter system where legs can serve multiple functions and be interchangeable. Any leg can replace another in the operational sequence, and the controller adapts to use any combination of functional legs, making the system flexible and reducing the need to replace entire units.
3Productivity
If legs operate continuously without rotation, then inverter productivity is maximized, but leg degradation accelerates
Solution Approach 1:
The patent implements periodic rotation through null vector states where legs are cyclically switched in and out of operation. During these periodic intervals, the controller activates null vector sequences that allow legs to rest while maintaining continuous power output through other legs, creating a rhythm of work and rest that extends individual leg lifetimes while sustaining overall system productivity.
Solution Approach 2:
The patent maintains continuous useful action at the system level while allowing individual legs to cycle through operational and resting states. By coordinating multiple legs and using space vector PWM with null vectors, the system ensures uninterrupted power delivery while distributing wear across all legs over time, achieving both continuity and sustainability.
Data Source
AI summary
An inverter system is provided such that the system includes a direct-current (DC) voltage supply, an inverter, an electric machine such as a motor, and a controller coupled with the inverter. The inverter has four or more legs, each with two switches operating complementary to each other. The controller can determine which three of the four or more legs are selected to operate the inverter and uses a remaining one of the four or more legs to operate the inverter by activating/deactivating certain switches during null vector state.