Asymmetrical T-Type Rectifier for Low-Current Harmonic Control
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Solution Overview
Problem
High-tier chiller applications require low total harmonic current distortion, which is not adequately addressed by traditional Vienna rectifiers at low currents, while T-type rectifiers are costly and inefficient.
Innovation Solution
An asymmetrical semiconductor arrangement is implemented in the T-type rectifier, where insulated gate bipolar transistors (IGBTs) have a smaller current rating than diodes, enabling them to bypass current only at low loads, and operate in pulse width modulation mode to reduce harmonic distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional Vienna rectifiers are used, then device complexity is reduced, but total harmonic current distortion increases at low currents
Solution Approach 1:
The patent applies asymmetry by configuring the T-type rectifier with unequal semiconductor ratings: diodes are rated for full load current while IGBTs are rated for only a portion of the load current. This asymmetric arrangement allows the IGBTs to remain inactive during high-current operation (reducing complexity to Vienna rectifier mode) while enabling harmonic distortion correction through PWM control during low-current operation when IGBTs become active.
2Object-generated harmful factors
If T-type rectifiers are used, then total harmonic current distortion is reduced, but manufacturing cost increases
Solution Approach 1:
The patent applies local quality by assigning different current ratings to different semiconductor devices based on their functional requirements. Diodes receive full-current ratings for continuous operation, while IGBTs receive reduced ratings since they only operate during low-current conditions. This localized differentiation optimizes component selection and reduces overall manufacturing cost while maintaining harmonic distortion benefits.
3Object-generated harmful factors
If T-type rectifiers with PWM control are used, then total harmonic current distortion is reduced, but energy loss increases
Solution Approach 1:
The patent applies dynamics by implementing a dynamic switching strategy where IGBTs are activated only when input current falls below a threshold level. During high-current operation, the rectifier operates in passive diode mode with zero switching losses. During low-current operation, IGBTs are dynamically activated with PWM control to correct harmonics, accepting localized energy losses only when necessary for harmonic mitigation.
Data Source
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AI summary
Systems for operating a rectifier (200; 300) are provided. Aspects include a rectifier comprising a set of bridge structures configured to receive an input current of a power supply (220; 320), wherein each bridge structure in the set of bridge structures comprises a set of diodes (204; 304) and a set of active switches (202; 302), wherein each active switch in the set of active switches is configured to provide a parallel path around each diode in the set of diodes when in a PWM state, a controller (240; 340) configured to determine a threshold current for the rectifier and operate one or more active switches in the rectifier in a PWM state based on the input current being less than the threshold current.