Motor Drive Phase Control for Regenerative Overvoltage
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Solution Overview
Problem
Synchronous motor systems using permanent magnets face challenges in maintaining efficiency and preventing overvoltage during regenerative braking, especially when driving loads with inertia, which can lead to increased device size and costs due to the need for additional components to manage regenerative energy.
Innovation Solution
A motor drive device with a phase adjustment mechanism that adjusts the phase of the inverter voltage to match the phase of the motor current, using a phase adjustment selection circuit to either advance or delay the phase based on an index to minimize current and torque, thereby preventing overvoltage and enhancing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If regenerative braking is implemented in synchronous motor systems, then energy recovery efficiency is improved, but overvoltage occurs in the circuit leading to increased device size and cost
Solution Approach 1:
The control device performs preliminary action by detecting voltage levels before overvoltage occurs and preemptively adjusting the inverter output phase. When the DC link voltage exceeds a predetermined threshold during regenerative braking, the control device advances the phase of the inverter output voltage relative to the motor back-EMF, thereby preventing overvoltage before it happens rather than reacting after overvoltage occurs.
Solution Approach 2:
The control device changes operating parameters dynamically by adjusting the phase angle between inverter output voltage and motor back-EMF based on voltage conditions. During normal operation, the phases are aligned for maximum efficiency, but during regenerative braking when voltage exceeds the threshold, the control device introduces a phase advance (parameter change) to redirect regenerative energy and prevent overvoltage, thus adapting the system operation to different conditions.
2Reliability
If additional components are added to manage regenerative energy, then overvoltage prevention is improved, but device size and cost increase
Solution Approach 1:
The control device utilizes the existing inverter and control circuitry to manage regenerative energy without requiring additional hardware components. By implementing phase adjustment control using the available PWM generation capabilities and voltage detection functions already present in the system, the device achieves overvoltage prevention through intelligent control algorithms rather than adding physical components like braking resistors or DC-DC converters.
Solution Approach 2:
The invention replaces mechanical or hardware-based overvoltage protection mechanisms (such as braking resistors, choppers, or DC-DC converters) with an electronic control mechanism. Instead of using additional physical components to dissipate or redirect regenerative energy, the system uses software-based phase angle adjustment of the inverter output to achieve the same protective function, thereby reducing device complexity and cost.
3Object-affected harmful factors
If phase adjustment is used to prevent overvoltage, then overvoltage prevention is improved, but motor efficiency decreases due to phase mismatch
Solution Approach 1:
The control device implements dynamic phase adjustment rather than a fixed phase shift. During normal motoring operation, the inverter output phase is aligned with the motor back-EMF for maximum efficiency. During regenerative braking, when voltage exceeds the threshold, the control device dynamically advances the phase only for the duration and magnitude necessary to prevent overvoltage, then returns to optimal alignment, thus adapting the phase relationship to real-time operating conditions.
Solution Approach 2:
The control device applies partial phase adjustment rather than continuous phase shifting. Phase advance is applied only partially (when voltage exceeds threshold during regenerative braking) rather than continuously, and only to the extent necessary to prevent overvoltage. This selective application minimizes the impact on motor efficiency while achieving the required overvoltage protection.
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 device effectively prevents overvoltage and maintains high efficiency by dynamically adjusting the phase of the inverter voltage, reducing the risk of circuit overvoltage and minimizing the need for additional components to manage regenerative energy, thus optimizing motor performance and reducing system size and cost.
Implementation Method 1
a power conversion device configured to convert a DC voltage into a three-phase AC power of a given voltage and a given frequency through a switching operation of a plurality of semiconductor elements
Implementation Method 2
a voltage detection circuit configured to detect a voltage at a DC input side of the power conversion device
Implementation Method 3
a plurality of phase adjustment circuits each configured to adjust a phase of the drive voltage; and a phase adjustment selection circuit configured to select one of calculation results of the plurality of phase adjustment circuits
Implementation Method 4
A motor drive device with a phase adjustment mechanism that adjusts the phase of the inverter voltage to match the phase of the motor current
Data Source
AI summary
According to one embodiment, a motor drive device includes: a conversion device converting a DC voltage into a three-phase AC power, and supplying the AC power to a motor; a detection circuit detecting a voltage at a DC side of the conversion device; a control circuit to apply a drive voltage to the motor; phase adjustment circuits adjusting a phase of the drive voltage; and a selection circuit selecting one of calculation results of the phase adjustment circuits and outputting the selected result to the control circuit. A first phase adjustment circuit of the phase adjustment circuits perform control to exert the advancing phase on a phase of the drive voltage if a detection value of the detection circuit exceeds a threshold, and the phase adjustment selection circuit selects an output of the first phase adjustment circuit if the detection value exceeds the threshold.