Synchronous Motor Control Device for Over-Voltage Prevention
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Solution Overview
Problem
Conventional synchronous motor control devices face challenges in managing regenerative energy during speed reduction, leading to over-voltage issues at the DC link part when the alternating-current power source fails, which increases costs and reduces efficiency, and may trigger over-voltage alarms.
Innovation Solution
A synchronous motor control device that detects and manages q-axis and d-axis currents to absorb regenerative energy within the motor, setting command values to balance power consumption and loss, ensuring zero regenerative power when the AC power source fails, thus preventing over-voltage without increasing costs or reducing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a regenerative resistor or dynamic brake is provided to consume regenerative energy when AC power source fails, then over-voltage at DC link part is avoided, but device complexity and cost increase
Solution Approach 1:
The synchronous motor itself is utilized to consume its own regenerative energy through controlled operation in generator mode during AC power failure. The motor acts as both the problem source and the solution, eliminating the need for external regenerative resistors or dynamic brakes. The control unit manages the motor's operation to absorb regenerative energy internally, achieving self-service energy management.
Solution Approach 2:
The control unit changes operational parameters (current commands, switching patterns) of the inverter to transition the synchronous motor between motor mode and generator mode. By dynamically adjusting these parameters based on power source status, the system enables the motor to absorb regenerative energy without requiring additional hardware components.
2Reliability
If d-axis current is increased to reduce regenerative energy during speed reduction, then operative efficiency decreases, but over-voltage is prevented
Solution Approach 1:
The control unit dynamically adjusts d-axis and q-axis current commands based on real-time operating conditions, specifically whether the AC power source is operational. During normal operation, standard current commands maintain high efficiency. During AC power failure, the control unit transitions to alternative current commands that prevent over-voltage while minimizing efficiency loss through optimized current vector control.
Solution Approach 2:
The system changes current control parameters (d-axis and q-axis current commands) based on power source status. During AC power failure, the control unit modifies these parameters to balance over-voltage prevention with efficiency maintenance, avoiding excessive d-axis current that would cause significant efficiency degradation while still preventing regenerative over-voltage.
3Measurement precision
If q-axis current is increased during speed reduction to maintain torque, then regenerative energy increases causing over-voltage alarm, but speed control accuracy is maintained
Solution Approach 1:
The control unit continuously monitors operational status (AC power source availability, motor speed, current values) and uses this feedback to adjust current commands in real-time. Based on feedback about power source status, the control unit switches between normal current commands (maintaining speed control accuracy) and alternative current commands (preventing over-voltage), achieving adaptive control that responds to system conditions.
Solution Approach 2:
The control system dynamically switches between different current control strategies based on power source status. During normal operation, standard dynamic current control maintains speed accuracy. During AC power failure, the control unit transitions to alternative dynamic current commands that limit regenerative energy while still providing adequate speed control through adjusted current vector management.
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 solution effectively avoids over-voltage at the DC link part, ensures safe and quick motor stoppage without alarms, and maintains operational efficiency by managing regenerative energy internally during AC power failures.
Implementation Method 1
regenerative energy, which is generated during speed reduction of the synchronous motor
Data Source
AI summary
A second q-axis current command value, which is set by a q-axis current command value setting unit when an alternating-current power source fails at the time of driving of a synchronous motor, and a second d-axis current command value, which is set by a d-axis current command value setting unit when the alternating-current power source fails at the time of the driving of the synchronous motor, are set so that an absolute value of power per unit time of the synchronous motor is equal to loss per unit time of the synchronous motor.