Multi-Three-Phase Inverter Layout for EMI and DC Ripple Reduction
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Solution Overview
Problem
Existing motor drive systems face challenges in reducing the size and weight of passive components, particularly EMI filters and DC link capacitors, which are crucial for aviation applications and overall system efficiency.
Innovation Solution
A multi-three-phase motor drive system with electrically isolated three-phase windings and phase-shifted carrier signals is employed to achieve common-mode noise cancellation and reduce DC ripple current, utilizing a configuration of inverters and phase-shifted carrier signals to minimize passive components and ripple current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If EMI filter and DC link capacitors are designed to meet EMI and power quality standards, then electromagnetic compatibility and power quality are improved, but system weight and volume increase significantly
Solution Approach 1:
The patent segments the single three-phase inverter into multiple three-phase inverters (first upper inverter unit, second upper inverter unit, first lower inverter unit, second lower inverter unit), each handling separate three-phase windings. This segmentation allows the common-mode voltage from each inverter to be independently controlled and canceled, reducing the need for large EMI filters and DC link capacitors.
Solution Approach 2:
The patent applies preliminary anti-action by using phase-shifted carrier signals to generate opposite common-mode voltages that cancel each other out before they can cause EMI issues. The controller generates carrier signals with specific phase shifts (e.g., 180 degrees) to create common-mode voltages that are equal in magnitude but opposite in polarity, thereby preemptively neutralizing the harmful EMI effects.
2Reliability
If EMI filter and DC link capacitors are sized to meet power quality standards, then power quality is improved, but system volume increases
Solution Approach 1:
The patent divides the motor drive system into multiple independent three-phase inverter units, each with its own DC link capacitor. This segmentation allows each capacitor to be sized much smaller than a single large capacitor would need to be, while collectively they provide the same or better power quality performance. The distributed capacitance reduces the total volume required.
Solution Approach 2:
The patent combines multiple small DC link capacitors from different inverter units to achieve the collective power quality performance that would otherwise require a single large capacitor. The capacitors work together in parallel to filter ripple current and maintain voltage stability, providing equivalent or superior power quality with reduced total volume.
3Object-generated harmful factors
If multi-three-phase configuration with phase-shifted carrier signals is used, then common-mode voltage cancellation and DC ripple reduction are achieved, but device complexity increases
Solution Approach 1:
The patent makes each three-phase inverter unit multi-functional by having it perform both motor drive functions and common-mode voltage cancellation. The same inverter devices and carrier signals used for motor control also generate the phase-shifted common-mode voltages needed for EMI reduction, eliminating the need for separate dedicated cancellation hardware.
Solution Approach 2:
The system achieves self-service by using its own control system to generate phase-shifted carrier signals that automatically cancel common-mode voltages. The controller monitors and adjusts the carrier signal phases to maintain common-mode cancellation without requiring external EMI filtering components, making the system self-regulating against its own harmful emissions.
Data Source
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AI summary
A multi-three-phase motor drive system (100) includes a power distribution network (101), a motor drive unit (120), and a motor network (150). The power distribution network includes a partitioned direct current, DC, link (106) connected between a positive voltage rail (102) and a negative voltage rail (104). A connection between the positive voltage rail and a mid-point node (108) defines an upper portion (110) of the partitioned DC link and a connection between negative voltage rail and the mid-point node defines a lower portion (112) of the partitioned DC link. The motor drive unit includes a plurality of inverter units (122, 124, 126, 128), and the motor network includes a plurality of motor windings (152, 154, 156 158) which are each connected to a respective inverter unit. A first group of the inverter units is connected in parallel with the upper portion of the portioned DC link, and a second group of the inverter units is connected in parallel with the lower portion of the partitioned DC link.