Motor Current Control Unit Voltage Saturation Prevention
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Solution Overview
Problem
Existing motor control methods face challenges in achieving high-speed, high-output performance while maintaining stability, as they either lead to voltage saturation or instability due to reactive current control and waveform modifications, which are costly and inefficient.
Innovation Solution
A control device comprising a converter unit, inverter unit, current detector, position detector, and current control unit that includes limit processing, PI compensation, and voltage limiting units to manage q-axis and d-axis currents, preventing overshoot and ensuring stable operation by converting two-phase to three-phase voltages and controlling armature currents effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a d-axis current is controlled to be passed at a set speed near to voltage saturation, then the motor capacity is drawn out as much as possible, but the current control becomes unstable in the worst case
Solution Approach 1:
The patent applies preliminary action by calculating and limiting the q-axis current command value before it is applied to the motor control system. The limit processing unit pre-calculates the maximum allowable q-axis current based on the relationship between d-axis and q-axis currents, preventing instability before it occurs. This proactive approach ensures that the motor operates at maximum capacity while maintaining control stability.
2Force
If the voltage to be applied is increased to obtain a larger torque, then the torque increases, but a large equipment is necessary which is expensive
Solution Approach 1:
The patent applies parameter changes by transforming the control strategy from voltage-based to current-based control. Instead of increasing applied voltage to obtain larger torque, the system optimizes the relationship between d-axis current (Id) and q-axis current (Iq) parameters. The limit processing unit calculates the optimal current distribution to maximize torque output within the existing voltage constraints, eliminating the need for expensive voltage increase equipment.
3Force
If capacities of the motor and inverter are increased to obtain a larger torque, then the torque increases, but this solution needs a high cost
Solution Approach 1:
The patent applies partial action by focusing control efforts on optimizing only the critical current parameters (Id and Iq) rather than increasing the entire motor and inverter system capacity. The limit processing unit implements partial control by selectively managing the q-axis current command based on d-axis current conditions, achieving maximum torque within existing hardware constraints without the high cost of upgrading entire system capacities.
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 solution enables the motor to achieve high-speed, high-output performance while securing stability, effectively preventing voltage saturation and ensuring efficient capacity utilization without the need for excessive equipment or increased costs.
Implementation Method 1
a converter unit configured to rectify and smooth an AC voltage
Implementation Method 2
a converter unit configured to rectify and smooth an AC voltage, and to output a DC main circuit voltage
Implementation Method 3
when the motor is rotated, a counter electromotive voltage occurs
Data Source
AI summary
The present invention is a control device of a motor, for drawing out a capacity of the motor as much as possible so as to achieve a high-speed high-output performance thereof while securing a stability, including: a converter unit configured to rectify and smooth an AC voltage, and to output a DC main circuit voltage; an inverter unit configured to pass a current for driving the motor, with the use of the main circuit voltage; a current detector configured to detect an armature current passing through the motor; a position detector disposed on the motor, the position detector being configured to detect a motor speed; and a current control unit configured to control, upon reception of a q-axis current command (Iqr), the armature current passing through the motor, by outputting a signal for driving the inverter unit, with the use of data from the current detector and data from the position detector.