Multi-Motor Regenerative Drive with CHB Inverters and Shared DC Bus

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Solution Overview

Problem

Conventional single drive systems for multiple motors require multiple pairs of inverters and converters, which are inefficient and costly, and do not effectively utilize regenerative energy.

Innovation Solution

A multi-motor drive system utilizing cascaded H-bridge power inverters and neutral point converters/inverters, where one motor operates in a driving mode and another in a regenerative mode, with power flow managed through a DC bus to optimize efficiency and reduce components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple pairs of inverters and converters are used to drive multiple motors, then each motor can be driven independently, but the system complexity and cost increase significantly

Engineering Contradiction:

Improveindependent motor controlVSAvoidnumber of inverters and converters

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Multiple converter/inverter units are merged into a single integrated system that shares common DC bus and control architecture. Each motor is controlled by a converter/inverter unit that can operate independently while being part of the unified multi-motor system, reducing the total number of separate components needed.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The converter/inverter units are designed with multi-functionality to handle both motoring and regenerative modes across multiple motors. Each unit can function as a converter or inverter depending on the operating mode of connected motors, allowing a single component type to serve multiple purposes and reducing overall system complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Device complexity

If conventional single drive systems are used for multiple motors, then the system structure is simple, but regenerative energy cannot be utilized and efficiency is low

Engineering Contradiction:

Improvesystem structureVSAvoidregenerative energy utilization

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The regenerative energy that would normally be lost during motor deceleration or downhill operation is captured and converted into usable electrical energy. The converter/inverter units enable bidirectional power flow, allowing motors acting as generators to feed energy back to the DC bus where it can be utilized by other motors or returned to the grid, transforming energy loss into a beneficial resource.

Inventive Principle:

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

Solution Approach 2:

The control system continuously monitors the operating state of each motor and dynamically adjusts the converter/inverter operation to maximize regenerative energy capture. When motors enter regenerative mode, the system automatically routes the generated energy back to the DC bus through the converter/inverter units, creating a closed-loop energy management system that optimizes efficiency.

Inventive Principle:

Principle #23Feedback

3Ease of operation

If multiple pairs of inverters and converters are used, then each motor has dedicated control, but the cost and space requirements increase

Engineering Contradiction:

Improvededicated motor controlVSAvoidcost and space

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The system merges multiple converter/inverter functions into shared hardware units that can serve multiple motors. The common DC bus and integrated control architecture reduce the total component count and installation space while maintaining dedicated control capability for each motor through software-based control strategies.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The control system dynamically allocates converter/inverter resources based on real-time motor operating conditions. Converter/inverter units can be dynamically assigned to different motors depending on which motors require power conversion, allowing flexible resource utilization that reduces the need for permanent dedicated hardware for each motor.

Inventive Principle:

Principle #15Dynamics

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

The system efficiently manages power flow between driving and regenerative modes, reducing the number of converters needed and optimizing energy usage, thereby enhancing flexibility, reducing costs, and minimizing space requirements.

Implementation Method 1

Each of the multiple CHB power inverters includes one or more DC terminals configured to receive DC power

Methodology Applied

Scientific EffectPower conversion:

Implementation Method 2

The second neutral point converter/inverter is configured to convert the regenerative power to DC power and provide the DC power to the DC bus

Methodology Applied

Scientific EffectPower conversion:

Data Source

PatentEP3975418B1Systems and methods of multi-motor regenerative drive

Publication Date: 2026.04.22 ROCKWELL AUTOMATION TECH INC

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AI summary

A system is provided for driving multiple motors. The system includes multiple cascaded H-bridge (CHB) power inverters, a DC bus, and multiple neutral point converter/inverters. Each of the multiple CHB power inverters is connected to a respective motor at one or more AC terminals of the CHB power inverter. Each of the multiple CHB power inverters includes one or more DC terminals configured to receive DC power. Each of the multiple neutral point converter/inverters is connected to a respective CHB power inverter at one or more neutral terminals of the respective CHB power inverter and connected to the DC bus.