Motor Driver Circuit for Grid-Feedback Regenerative Braking
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Solution Overview
Problem
Existing motor driving systems face issues with overvoltage damage due to regenerated energy in DC link circuits, which can damage capacitors and require large, expensive braking resistors that generate excessive heat and occupy significant space.
Innovation Solution
A motor driver system with a rectifying circuit, DC link circuit, and inverter circuit, incorporating half bridge branches and freewheeling diodes, allows regenerated energy to be fed back to the power grid, eliminating the need for a braking resistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a braking resistor is used to dissipate regenerated energy, then overvoltage damage is prevented, but system volume increases and heat dissipation becomes a major challenge
Solution Approach 1:
The patent extracts the harmful braking resistor from the system by implementing a regenerative braking circuit that feeds energy back to the power grid instead of dissipating it as heat. The circuit includes a rectifier bridge, DC link circuit, and inverter circuit with switching devices that enable bidirectional energy flow, eliminating the need for resistive energy dissipation and its associated volume and heat problems.
Solution Approach 2:
The patent converts the harmful regenerated energy that causes overvoltage into a beneficial resource by feeding it back to the power grid. The DC link circuit with capacitor and the inverter circuit with controlled switching devices enable the system to return energy to the grid, transforming the overvoltage problem into an energy recovery opportunity that improves efficiency and reduces waste.
2Reliability
If a braking resistor is used to dissipate regenerated energy, then overvoltage damage is prevented, but manufacturing cost increases due to custom-made requirements
Solution Approach 1:
The patent removes the specialized braking resistor component from the system architecture. Instead of using a custom-made high-power resistor, the design employs standard off-the-shelf switching devices, capacitors, and diodes arranged in a regenerative circuit topology, significantly improving ease of manufacture and reducing dependency on custom components.
Solution Approach 2:
The inverter circuit and switching devices serve multiple functions: they control motor operation during normal driving and simultaneously enable regenerative braking by feeding energy back to the grid. This multi-functionality eliminates the need for separate braking resistor components and their associated manufacturing complexities.
3Reliability
If a braking resistor is used to dissipate regenerated energy, then overvoltage damage is prevented, but heat dissipation requirements increase system complexity
Solution Approach 1:
The patent eliminates the heat generation problem entirely by converting the regenerated energy into useful electrical energy that is fed back to the power grid. The switching devices and control circuitry manage the energy flow, transforming what would have been waste heat into recoverable energy, thereby eliminating the need for complex heat sink designs.
Solution Approach 2:
The patent extracts the heat dissipation function from the system by preventing energy dissipation altogether. Instead of using a braking resistor that converts energy to heat requiring heat sinks, the design uses power electronic switches and a DC link capacitor to redirect energy back to the grid, eliminating the thermal management burden.
4Use of energy by moving object
If the DC voltage rises due to regenerated energy, then energy is stored in the capacitor, but overvoltage damage occurs to the capacitor
Solution Approach 1:
The patent implements a feedback mechanism where the DC link voltage is continuously monitored and the inverter circuit responds by activating regenerative braking mode when overvoltage conditions are detected. The switching devices are controlled to feed energy back to the grid, creating a closed-loop control system that prevents capacitor overvoltage while maximizing energy recovery.
Solution Approach 2:
The patent converts the harmful overvoltage condition into a beneficial energy recovery opportunity. When the DC link capacitor voltage rises due to regenerated energy, the system activates the inverter circuit to feed this excess energy back to the power grid, preventing capacitor damage while utilizing the stored energy productively.
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 design prevents overvoltage damage, reduces system volume, lowers costs, and enables energy recovery by feeding back regenerated energy to the power grid, improving system cooling and efficiency.
Implementation Method 1
the rectifier bridge (2101) comprises a first bridge arm and a second bridge arm connected in parallel
Implementation Method 2
the DC link circuit (220) comprises a capacitor (C1) and a second half bridge (2202)
Implementation Method 3
the inverter circuit (230) comprising first, second and third DC/AC conversion branch circuits (2301, 2302, 2303)
Implementation Method 4
the ninth freewheeling diode (D9) is connected in reverse between a collector and an emitter of the ninth switching device (T9)
Data Source
AI summary
Some embodiments of the teachings herein include a motor driver with an input end connected to a three-phase power grid, an output end connected to a motor, a rectifying circuit, a DC link circuit; and an inverter circuit. The inverter circuit has three DC/AC conversion branch circuits connected in parallel between positive and negative output ends of the DC link circuit and each conversion branch circuits has six switching devices. The rectifying circuit comprises a rectifier bridge, a first half bridge, three switches, and an inductor. When the motor is operating in a braking regeneration mode, regenerated energy generated during braking of the motor is fed back to a power grid.