Multi-phase-shift Control for DAB Converter ZVS
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Solution Overview
Problem
Conventional electric vehicle power converters fail to provide zero-voltage switching (ZVS) for all semiconductor switches across a wide-input-voltage range and maintain high performance at light loads, leading to inefficiencies and grid current distortion.
Innovation Solution
The implementation of multi-phase-shift control in a power converter, which includes dual-phase-shift and triple-phase-shift modes, ensures zero-voltage switching and unity power factor by controlling the primary and secondary sides of the transformer with two-level or three-level voltage waveforms, allowing for efficient power transfer across a wide range of voltage levels and power outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If single-phase-shift mode is used in DAB circuit, then zero-voltage switching is achieved for all semiconductor switches, but light-load performance deteriorates and grid current distortion increases
Solution Approach 1:
The patent implements dynamic switching between single-phase-shift mode and dual-phase-shift mode based on load conditions. At light loads, the system transitions to dual-phase-shift mode to maintain unity power factor and reduce grid current distortion, while at higher loads it operates in single-phase-shift mode to ensure zero-voltage switching. This dynamic adaptation resolves the contradiction by adjusting the control strategy according to operating conditions.
Solution Approach 2:
The patent changes the control parameter from fixed single-phase-shift to variable phase-shift configuration. By introducing a second phase-shift degree of freedom in dual-phase-shift mode, the system can independently control both zero-voltage switching and power factor, thereby eliminating grid current distortion at light loads while maintaining ZVS capability.
2Reliability
If switching frequency and phase shift are varied in DAB circuit, then zero-voltage switching is ensured over wider voltage range, but light-load grid current performance is sacrificed
Solution Approach 1:
The patent segments the control strategy into distinct operating modes: single-phase-shift mode for high power factor requirements and dual-phase-shift mode for wide voltage range ZVS requirements. By dividing the control approach, the system can optimize for different priorities depending on operating conditions, resolving the contradiction between wide voltage range ZVS and light-load power factor performance.
3Power
If conventional DAB circuit is used, then power conversion is achieved, but performance is lost when operated with wide voltage-gains and light load conditions
Solution Approach 1:
The patent enhances the DAB circuit with dual-phase-shift control capability, making it universally applicable across wide voltage gains and all load conditions. The system can adapt its control mode (single-phase-shift or dual-phase-shift) to maintain optimal performance whether operating at full load or light load, thereby achieving both power conversion capability and reliable light-load performance.
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
This solution achieves ZVS and unity power factor over a wide range of input and output voltages, including low and high power outputs, while maintaining high performance at light loads, reducing grid current distortion and enhancing efficiency.
Implementation Method 1
The primary and secondary sides are inductively coupled through the transformer. Thus, power can be transferred from the primary to the secondary by proper control of the multi-level voltage signals applied to both the primary and secondary windings of the transformer.
Data Source
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AI summary
Multi-phase-shift control of a power converter is provided. The power converter includes a dual-active-bridge (DAB) converter having a transformer, a first H-bridge coupled to the primary winding of the transformer, and a second H-bridge coupled to the secondary winding of the transformer. The DAB converter is operable to generate two-level and three- level voltage waveforms on the primary winding and on the secondary winding to yield a system which ensures zero-voltage switching and unity power factor over a wide range of input and output voltage levels and power throughputs. In a multi-phase shift (MPS) mode of operation, the DAB converter changes from a two-level voltage in at least one of the windings to a three-level voltage in both windings in response to the instantaneous load being below a predetermined level, resulting in more efficient performance of the DAB converter in light load conditions.