Regenerative Multicell Drive Control for Low Harmonic Distortion
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Solution Overview
Problem
Existing medium voltage variable frequency drives face challenges in meeting IEEE-519 guideline harmonics limits during regeneration mode due to fixed conduction angles in power cells, particularly in cascaded H-bridge converters with low cell counts, leading to significant harmonic distortion.
Innovation Solution
A regenerative drive system with variable conduction angles for active front-end switching devices, adjusting the conduction angles based on output current and impedance to reduce harmonic distortion, using formulas to determine optimal angle advances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If fixed conduction angles are used in power cells during regeneration mode, then the control system is simple, but the harmonic distortion exceeds IEEE-519 guidelines
Solution Approach 1:
The patent implements dynamic adjustment of conduction angles for active front-end switching devices based on real-time operating conditions. The control system varies conduction angles according to output current magnitude and impedance characteristics, transitioning from fixed to variable control. This dynamic approach enables the system to meet IEEE-519 harmonic distortion limits during regeneration mode while maintaining operational flexibility across different load conditions.
Solution Approach 2:
The patent changes the conduction angle parameter of switching devices from a fixed value to a variable parameter that adapts to operating conditions. By adjusting conduction angles based on output current and impedance, the system optimizes harmonic performance during regeneration. This parameter modification transforms the control strategy to achieve compliance with IEEE-519 standards without requiring complete system redesign.
2Object-generated harmful factors
If variable conduction angles are implemented to reduce harmonic distortion, then IEEE-519 compliance is achieved, but the control algorithm complexity increases
Solution Approach 1:
The patent employs feedback mechanisms where the control system continuously monitors output current and impedance characteristics, then adjusts conduction angles accordingly. This closed-loop control enables real-time optimization of harmonic distortion while maintaining IEEE-519 compliance. The feedback approach allows the system to adapt to changing operating conditions without requiring overly complex predictive algorithms.
Data Source
AI summary
A regenerative drive system includes a plurality of power cells receiving power from a source and supplying power to one or more output phases, wherein each power cell is operable in multiple operation modes, each power cell including multiple switching devices including active front-end switching devices, and a central control system controlling operation of the plurality of power cells, wherein the central control system is configured to control the active front-end switching devices of each power cell with variable conduction angles in the multiple operation modes.