Regenerative Rectifier for Motor Drive Bi-Directional Power Flow
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Solution Overview
Problem
Existing variable frequency drives (VFDs) face limitations in handling regenerative energy, leading to high DC bus voltage trips due to the inability to efficiently manage power flow in both motoring and regeneration conditions, constraining regenerative torque and power to less than 2-3% of rated power.
Innovation Solution
A regenerative front-end AC to DC converter with anti-parallel electronic switching devices and a controller that determines a grid angle to generate control signals for the switching devices, allowing bi-directional power flow and efficient conversion of regenerative energy back to the AC power grid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-way rectifier is used in the VFD, then the device complexity is reduced and ease of manufacture is improved, but the regenerative torque and power handling capability deteriorates to less than 2-3% of rated power
Solution Approach 1:
The patent applies dynamics by making the rectifier circuit bidirectional and controllable, allowing it to adapt its operation mode based on whether the motor is in motoring or regenerative state. The electronic switching devices enable the circuit to dynamically switch between rectification modes, transforming the static single-way rectifier into a dynamic bidirectional power flow system that can handle significant regenerative power.
2Device complexity
If a single-way rectifier is used in the VFD, then the device complexity is reduced, but the ability to manage power flow in both motoring and regeneration conditions deteriorates
Solution Approach 1:
The patent implements universality by designing a rectifier circuit that performs multiple functions: it operates as a conventional rectifier during motoring mode and as a regenerative energy handling circuit during regeneration mode. The bidirectional electronic switching devices enable the same circuit topology to universally handle both power flow directions, eliminating the need for separate circuits for each mode.
Solution Approach 2:
The control system dynamically adjusts the switching states of electronic devices based on the operational mode (motoring or regenerative), enabling the circuit to adapt its power flow management characteristics in real-time, thereby achieving versatile power flow management without proportionally increasing complexity.
3Reliability
If regenerative energy is released through a chopper or dynamic brake, then the DC bus voltage is stabilized, but the regenerative energy is lost as heat and the regenerative torque is limited
Solution Approach 1:
The patent converts the harmful effect of regenerative energy causing DC bus voltage rise into a beneficial resource by enabling bidirectional power flow that feeds this energy back to the AC utility. The regenerative energy that would otherwise be wasted or require dissipative braking is instead transformed into useful power that can be returned to the grid, eliminating energy loss while maintaining DC bus stability.
4Power
If a regenerative rectifier is provided to convert regenerative energy back to AC, then the regenerative energy management is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent achieves high regenerative power handling capability while controlling complexity by designing a universal bidirectional rectifier circuit that serves both motoring and regenerative functions. The same electronic switching devices and control logic handle both power flow directions, eliminating the need for separate dedicated regenerative circuits and reducing overall system complexity despite the enhanced functionality.
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
Enables efficient management of regenerative energy, allowing for increased regenerative torque and power handling, reducing the likelihood of high DC bus voltage trips and enhancing the overall performance of VFDs in motor drives.
Implementation Method 1
A regenerative front end AC to DC converter... allowing bi-directional power flow and efficient conversion of regenerative energy back to the AC power grid
Data Source
AI summary
A system, and associated method, for controlling a motor drive coupled to an AC power source in a condition wherein the motor drive is generating a regenerative current. The system includes a plurality of electronic switching devices structured to be provided in anti-parallel connection with a plurality of rectifier diodes of the motor drive, and a controller structured and configured to receive a number of phase voltages from the AC power source, determine a grid angle for the AC power source using the number of phase voltages, and generate a number of control signals for controlling the electronic switching devices using the grid angle when the motor drive is generating the regenerative current.