Multilevel Power Converter Phase Control Harmonic Reduction
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Solution Overview
Problem
Multilevel power conversion systems face challenges in efficiently managing harmonics and reducing the size and complexity of power stage filters, particularly in regenerative applications, where existing solutions often require large and heavy LCL filters to meet harmonic standards.
Innovation Solution
The implementation of a multiphase multilevel regenerative power converter with a controller that provides non-zero phase relationships between switching rectifier and inverter control signals, allowing for selective harmonic reduction and potentially eliminating the need for large power stage filters by using carrier signal phase shifting and trap filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If large LCL filters are used to meet harmonic standards, then harmonic filtering performance is improved, but the size and weight of the power converter system increases
Solution Approach 1:
The patent applies carrier signal phase shifting by changing the phase angle parameter of the control signals. By adjusting the phase relationship between carrier signals of different power stages, the patent achieves harmonic cancellation without requiring large physical filters, thus resolving the contradiction between harmonic filtering performance and system size/weight
Solution Approach 2:
The patent replaces the mechanical/physical LCL filter system with an electronic control system that uses phase-shifted carrier signals. This substitution eliminates the need for large inductors and capacitors while maintaining harmonic filtering effectiveness through controlled phase relationships in the switching signals
2Object-generated harmful factors
If complex filter designs are implemented to reduce harmonics, then harmonic distortion is reduced, but device complexity increases
Solution Approach 1:
Instead of complex filter circuitry, the patent changes the control parameter (carrier signal phase angle) to achieve harmonic reduction. This parameter-based approach simplifies the device design while maintaining effective harmonic distortion reduction through phase-controlled switching
3Power
If traditional rectifier control is used, then power conversion is achieved, but harmonic injection into the grid occurs
Solution Approach 1:
The patent employs periodic switching action with phase-shifted carrier signals for the rectifier stages. This periodic control strategy, where switching occurs at specific phase angles, enables power conversion while the phase shifting creates destructive interference of harmonic components, preventing their injection into the grid
Solution Approach 2:
The patent converts the potentially harmful harmonic effects into a beneficial control mechanism. By intentionally introducing phase shifts in the carrier signals, the harmonics that would normally be harmful are transformed into a useful tool for active harmonic cancellation and grid current purification
Data Source
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AI summary
Power conversion systems and methods to control a multiphase multilevel regenerative power converter with multilevel phase circuits that individually include multiple regenerative power stages with respective power stage outputs connected in series, the individual power stages comprising a DC link circuit a switching rectifier coupled between a respective transformer secondary circuit and the DC link circuit, and a switching inverter coupled between the DC link circuit and the respective power stage output, including a controller that provides inverter switching control signals to control the respective switching inverters, provides rectifier switching control signals to control the respective switching rectifiers, and controls a non-zero phase relationship between the rectifier switching control signals of the respective switching rectifiers.