Three-Phase AC/DC Converter Topology for Low-THD Input Current
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Solution Overview
Problem
Current three-phase AC/DC converters face challenges in achieving low input-current harmonic distortion and high power factor while being cost-effective, especially in high input voltage and power applications, with existing solutions either being costly due to the use of wide-band-gap devices or requiring numerous active switches.
Innovation Solution
A three-phase AC/DC converter design featuring a switching stage with half bridge modules connected in series, utilizing flying capacitors and a controller for generating control signals, which allows for zero voltage switching and variable-frequency modulation, decoupling input currents, and providing low THD and high power factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If Vienna rectifier is used to minimize current distortion, then THD is reduced and power factor is improved, but device complexity and cost increase due to too many components
Solution Approach 1:
The rectifier is divided into multiple independent half-bridge modules (first, second, third, and fourth modules) with each module handling a specific phase and switching sequence. This segmentation allows each module to operate semi-independently, reducing the need for complex interconnections while maintaining low THD through phase-separated current paths.
Solution Approach 2:
The patent implements dynamic switching sequences where the switching states of different modules are coordinated in time. The controller dynamically adjusts which modules are active during different intervals of the AC cycle, enabling flexible current shaping that achieves low THD without requiring all components to be active simultaneously, thus reducing effective complexity.
2Loss of energy
If six-switch boost converter with wide-band-gap devices is used, then efficiency and power density are improved, but cost increases due to expensive devices
Solution Approach 1:
Multiple half-bridge modules are merged into a unified circuit architecture where they share common components such as the output capacitor CO and the load. The modules are combined in a modular fashion that allows them to collectively achieve high efficiency through coordinated switching while using standard voltage-rated devices rather than expensive wide-band-gap devices for each individual switch.
Solution Approach 2:
The patent uses replicated half-bridge module designs where each module is a copy of the basic two-switch topology. This copying approach allows the system to achieve the efficiency benefits of active switching in multiple parallel paths while using conventional, cost-effective semiconductor devices in each replicated module, avoiding the need for expensive specialized devices.
3Power
If ultra-high voltage devices are used for high input voltage, then power delivery capability is improved, but cost increases and device availability decreases
Solution Approach 1:
The high voltage input is segmented across multiple series-connected half-bridge modules, each handling a portion of the total voltage. This segmentation allows the use of standard voltage-rated switches in each module rather than requiring a single ultra-high voltage device, improving both cost-effectiveness and device availability while maintaining the required power delivery capability through the combined action of all modules.
Solution Approach 2:
The patent transitions from a single-device high voltage approach to a multi-device series arrangement, adding the dimension of modular series connection. This dimensional change in the circuit architecture allows standard voltage devices to be combined to achieve ultra-high voltage operation, solving the availability and cost issues associated with single ultra-high voltage devices while maintaining power delivery capability.
4Stress or pressure
If multiple DC/DC converters are cascaded for high input voltage, then voltage blocking capability is improved, but device complexity increases due to multiple switches and galvanic isolation requirements
Solution Approach 1:
The patent merges the voltage blocking function with the power conversion function in a single integrated half-bridge module architecture. The series-connected modules provide both the necessary voltage blocking capability and the power conversion in one unified structure, eliminating the need for separate DC/DC converter stages and their associated isolation components, thus reducing overall device complexity.
Data Source
AI summary
The present disclosure provides a three-phase AC/DC converter aiming for low input current harmonic. The converter includes an input stage for receiving a three-phase AC input voltage, an output stage for at least one load, and one or more switching conversion stages, each stage including a plurality of half bridge modules. The switches in each module operate with a substantially fixed 50% duty cycle and are connected in a specific pattern to couple a DC-link and a neutral node of the input voltage. The AC/DC converter further includes one or more controllers adapted to vary the switching frequency of the switches in the switching conversion stages based on at least one of load voltage, load current, input voltage, and DC-link voltage. The converter can also include one or more decoupling stages, such as, inductive components adapted to decouple the output stage from the switching conversion stages.