Paralleled Passive Front-End Rectifiers for Common-Mode EMI Control
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Solution Overview
Problem
High power motor drives for applications like elevators and HVAC/R chiller systems face challenges with electromagnetic interference (EMI) due to timing and switching in power systems, leading to increased design costs and complexity, and existing solutions like CM filters are not viable due to weight penalties.
Innovation Solution
A three-phase paralleled passive front-end drive system with a rectifier bridge connected to a three-phase AC power source, using coupling reactance to transfer power to a DC bus and interphase inductors to combine motor excitation signals from multiple inverters, thereby reducing common-mode noise and eliminating the need for CM filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If paralleled drives are used to provide high power, then cost effectiveness improves, but common-mode EMI noise increases
Solution Approach 1:
Interphase inductors are introduced as intermediary components between paralleled inverters. These inductors act as mediators that combine motor excitation signals from multiple inverters while simultaneously suppressing common-mode EMI noise through their inductive impedance, allowing cost-effective paralleled operation without the harmful EMI effects
2Object-generated harmful factors
If CM filters are added to attenuate CM noises, then EMI noise is reduced, but weight increases significantly
Solution Approach 1:
The patent converts the potentially harmful common-mode currents that flow through paralleled drives into a beneficial solution. By using interphase inductors, the system allows these currents to circulate between paralleled inverters in a controlled manner, transforming what would be EMI noise into a manageable electrical phenomenon that actually helps balance the paralleled system while suppressing emissions
3Power
If a single large high power drive is used, then power capability is sufficient, but cost and design complexity increase
Solution Approach 1:
The high power drive system is segmented into multiple lower-power inverters operating in parallel. Each inverter handles a portion of the total power requirement, reducing individual component stress and simplifying design. The segmentation is coordinated through control signals that synchronize the paralleled inverters, achieving the equivalent of a single large drive with reduced complexity and cost
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 effectively reduces common-mode EMI noise, eliminates the need for CM filters, and allows for cost-effective high power drive systems by stabilizing DC buses and controlling circulation currents, enabling efficient operation of high power motor drives without excessive weight or complexity.
Implementation Method 1
coupling reactance operably configured to transfer power from the rectifier to a first direct current (DC) bus
Implementation Method 2
combining the plurality of motor excitation signals from the first inverter with the plurality of motor excitation signals from the second inverter with a plurality of interphase inductors
Data Source
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AI summary
Embodiments herein relate to a method of controlling a three-phase paralleled passive front-end drive connectable to a three phase alternating current power source. The method includes connecting a coupling reactance to the rectifier bridge, the coupling reactance configured to transfer power from the rectifier to a first direct current (DC) bus, coupling the first DC bus to a second DC bus, and connecting a first inverter to the first DC bus and connecting a second inverter to the second DC bus. The method also includes connecting a first controller to the first inverter and the second inverter, the first controller configured to generate control signals to cause the first inverter and the second inverter to generate a plurality of motor excitation signals respectively, and combining the plurality of motor excitation signals from the first inverter with the plurality of motor excitation signals from the second inverter.