Space Vector Modulation for Low-EMI Multilevel Inverters

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing power converters generate significant electromagnetic interference (EMI) noise, particularly in aerospace applications, necessitating bulky passive EMI filters and requiring improved active EMI mitigation techniques to meet stringent industry standards.

Innovation Solution

A modified space vector modulation scheme for multi-level inverters that reduces common mode voltage (CMV) by optimizing switching sequences using a four-vector approach on a space vector diagram, minimizing CMV to ±1/6 Vdc while maintaining dc-link capacitor balance without additional circuitry.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If passive EMI filters are used to reduce EMI noise, then EMI attenuation is improved, but the filter size and weight increase

Engineering Contradiction:

ImproveEMI noiseVSAvoidfilter weight

Core Design Contradiction:

Object-affected harmful factorsVSWeight of stationary object

Solution Approach 1:

The patent applies space vector modulation to convert the harmful EMI noise into beneficial control by optimizing the switching sequences. The modulation technique selectively applies voltage vectors to minimize common-mode voltage while maintaining the required output, effectively converting the EMI problem into a controllable parameter that can be optimized through software control rather than requiring bulky passive filtering hardware

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the modulation parameters by using an optimized space vector modulation scheme that adjusts the duty cycles and switching sequences of the inverter bridges. By modifying the modulation depth, switching frequency, and vector selection parameters, the common-mode voltage is reduced without requiring changes to the physical EMI filter hardware, thereby reducing filter size and weight

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If passive EMI filters are used to meet EMI standards, then EMI attenuation is improved, but the power density decreases

Engineering Contradiction:

ImproveEMI noiseVSAvoidpower density

Core Design Contradiction:

Object-affected harmful factorsVSPower

Solution Approach 1:

The modulation technique converts the EMI attenuation function from a passive hardware requirement to an active control function. By using optimized space vector modulation to minimize common-mode voltage, the system achieves EMI compliance without bulky filters, thereby improving power density while maintaining EMI standards

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent replaces the mechanical/passive EMI filter system with an electronic/software-based modulation control system. The space vector modulation algorithm electronically suppresses common-mode voltage through intelligent switching control, substituting the need for large passive filtering components and thereby increasing overall system power density

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Power

If switching speed is increased to improve power conversion efficiency, then power density is improved, but EMI noise increases

Engineering Contradiction:

Improvepower conversion efficiencyVSAvoidEMI noise

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The patent changes the relationship between switching speed and EMI by implementing space vector modulation that optimizes the switching sequences. The modulation technique adjusts the duty cycles and vector selection to minimize common-mode voltage even at high switching frequencies, thereby maintaining power conversion efficiency while suppressing EMI noise through parameter optimization rather than reducing switching speed

Inventive Principle:

Principle #35Parameter changes

4Power

If bus voltage is increased to improve power output, then power density is improved, but EMI noise increases

Engineering Contradiction:

Improvepower outputVSAvoidEMI noise

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The patent changes the modulation parameters to compensate for higher bus voltages. The space vector modulation scheme adjusts the voltage vector magnitudes and switching duty cycles to maintain optimal common-mode voltage levels even when operating at increased bus voltages, thereby achieving higher power output while keeping EMI noise under control through software-based parameter optimization

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP4629495A1Space vector modulation for EMI mitigation in power converters

Publication Date: 2025.10.08 COLLINS AEROSPACE IRELAND LTD

Figure 1
Figure 2
Figure 3

AI summary

A method of implementing a space vector pulse width modulation scheme comprising: mapping switching states for an n-phase, where n is an integer, multilevel inverter onto a two-dimensional hexagonal space vector diagram; identifying redundant vectors in the space vector diagram and removing redundant vectors associated with a common mode voltage current contribution of more than a predetermined threshold; identifying a location in the space vector diagram of a voltage reference vector; identifying a sector of the space vector diagram defined by four vectors within which the voltage reference vector is located; determining duty cycles and switching states associated with the four vectors to synthesise the voltage reference vector.