Four-Quadrant Modulation for Multilevel Inverters
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Solution Overview
Problem
Existing multilevel converter/inverter technologies have limited modulation index ranges and increased switching frequency and power loss when attempting to extend harmonic requirements, making them inefficient for high-performance applications.
Innovation Solution
A four-quadrant modulation technique that determines switching angles without limitations, transforms undesired states into practical states, and generates driving signals using phase information, allowing for a full modulation index range and efficient harmonic management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional PWM modulation techniques are used to extend modulation index range, then modulation range is increased, but switching frequency and switching power loss increase
Solution Approach 1:
The patent changes the fundamental parameter of switching angle determination by introducing four-quadrant switching angles that extend beyond the conventional first quadrant. This parameter change allows the modulation technique to achieve full modulation index range while maintaining lower switching frequencies and reduced power losses by optimizing the switching patterns across all four quadrants of the modulation index plane.
2Adaptability or versatility
If conventional PWM modulation techniques are used to extend modulation index range, then modulation range is increased, but harmonic requirements are difficult to meet
Solution Approach 1:
The patent implements dynamic switching angle adjustment across four quadrants, where the switching angles are continuously optimized based on the operating point in the modulation index plane. This dynamic approach ensures that harmonic requirements are met at all modulation indices by adaptively selecting optimal switching patterns, rather than using fixed switching strategies.
Solution Approach 2:
The patent incorporates feedback mechanisms where the actual harmonic content is measured and used to adjust the switching angles in real-time. This closed-loop control ensures that harmonic requirements are continuously satisfied across the extended modulation index range by comparing actual performance with target specifications and making corrective adjustments.
3Adaptability or versatility
If switching angles are determined without limitations, then full modulation index range is achieved, but undesired switching states occur
Solution Approach 1:
The patent applies preliminary transformation to the four-quadrant switching angles to convert them into valid practical switching states before actual implementation. This pre-processing step checks and adjusts the switching angles to ensure they correspond to physically realizable switching patterns, preventing undesired or invalid switching states from occurring in the actual converter operation.
Data Source
AI summary
Four quadrant modulation techniques that can synthesize a full range solution or a full modulation index range are provided. Such techniques can be applied to a DC/AC inverter, an AC to DC rectifier, and AC/DC/AC topology. The techniques can also be applied to a neutral point clamped (NPC) topology, flying capacitor (FLC) topology, cascaded H-bridge (CHB) topology, modular multilevel topology, modular multilevel converters, and multimodule converters.