Paralleled Passive Front-End Drives Using PWM EMI Cancellation
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Solution Overview
Problem
High power motor drives for elevator and HVAC/R chiller systems face challenges with electromagnetic interference (EMI) noise, particularly common-mode noise, which can damage motor components and require expensive high-voltage components, and existing solutions like CM filters are not viable due to weight and cost issues, while high power drives are costly and time-consuming to develop.
Innovation Solution
A three-phase paralleled passive front-end drive system with two rectifier bridges, coupling reactances, and interphase inductors, where controllers generate PWM signals to synchronize and perturb duty cycles of inverters to minimize common-mode noise and balance currents, reducing the need for costly filters and high-power components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected 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 harmful common-mode noise into a useful control parameter by using PWM techniques to actively cancel CM voltage. The controllers generate complementary perturbation signals that create opposing CM voltages, which cancel each other out, thereby converting the harmful EMI effect into a beneficial noise cancellation mechanism.
Solution Approach 2:
The patent introduces controllers as intermediary devices that mediate between the rectifier bridges and the load. These controllers actively manage the PWM signals and duty cycles to suppress CM noise at its source, rather than passively filtering it afterward with heavy CM filters.
2Power
If a single large high power drive is used, then high load requirements are met, but cost and development time increase
Solution Approach 1:
The patent segments the high power drive requirement into multiple parallel lower-power drives (first and second drive assemblies). Each drive assembly handles a portion of the total load, allowing the system to meet high power requirements while using off-the-shelf lower-power components, thereby reducing development time and cost.
Solution Approach 2:
The patent merges multiple parallel drive assemblies to achieve the required high power output. By combining the outputs of several lower-power drives through interphase inductors and synchronized control, the system achieves equivalent performance to a single large drive without the associated costs and development delays.
3Ease of manufacture
If paralleled drives are used, then cost is reduced, but current balancing and synchronization become more complex
Solution Approach 1:
The patent implements feedback control mechanisms where controllers continuously monitor the operation status and load conditions of each parallel drive assembly. Based on this feedback, the controllers dynamically adjust PWM duty cycles and firing angles to maintain current balance and synchronize operation, simplifying the control of paralleled drives.
Solution Approach 2:
The patent employs periodic PWM switching actions with synchronized timing across all parallel drives. By using periodic control signals with coordinated duty cycles and complementary perturbations, the system achieves current balancing and synchronization through rhythmic, predictable switching patterns rather than complex continuous control.
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, balances current outputs, and allows for cost-effective and efficient high load handling by paralleling lower power drives, reducing development time and costs.
Implementation Method 1
a first rectifier bridge configured for connection to a three phase alternating current power source; a first coupling reactance operably connected to the first rectifier bridge and configured to transfer power from the rectifier to a first direct current (DC) bus
Implementation Method 2
a first coupling reactance operably connected to the first rectifier bridge and configured to transfer power from the rectifier to a first direct current (DC) bus
Implementation Method 3
a plurality of interphase inductors operable to combine the plurality of motor excitation signals from the first inverter with the plurality of motor excitation signals from the second inverter
Data Source
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AI summary
Embodiments herein relate to a three-phase paralleled passive front-end drive, that includes a rectifier bridge, a coupling reactance operably connected to the rectifier bridge and configured to transfer power from the rectifier to a first direct current (DC) bus, and a bus coupler operably coupling the first DC bus to a second DC bus. The paralleled drive also includes a first inverter operably connected to the first DC bus; a second inverter operably connected the second DC bus, the first inverter and second the inverter each configured to provide a plurality of motor excitation signals, respectively. The paralleled drive also includes a plurality of interphase inductors operable to combine the plurality of motor excitation signals from the first inverter with the plurality of motor excitation signals from the second inverter.