Motor Drive Control Device Stabilizing Booster Circuit During Start-Stop
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Solution Overview
Problem
The motor drive control apparatus faces instability during starting and stopping operations of the booster circuit, leading to uncontrollable current flow and potential overcurrent issues due to rapid or slow voltage changes, affecting the controllability of anti-harmonic devices and the efficiency of the motor drive system.
Innovation Solution
A motor drive control apparatus with a rectifier, booster circuit, smoothing capacitor, inverter circuit, boost control unit, and inverter control unit, which includes a boosting operation stop determination unit to manage the booster circuit's operation based on detected DC bus voltage and modulation degree, ensuring stable operation by fixing the motor's rotation speed and controlling the booster circuit's start and stop conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the DC bus voltage is boosted rapidly to the target voltage during starting operation, then the voltage reaches the target quickly, but a current rapidly flows to the AC source side which deteriorates the controllability of anti-harmonic devices and the booster circuit
Solution Approach 1:
The patent applies dynamics by making the voltage change speed adjustable rather than fixed. The control device dynamically adjusts the voltage change speed of the DC bus voltage during boosting operation based on system conditions, allowing the system to adapt between rapid voltage rise (for efficiency) and controlled voltage rise (for stability and controllability).
2Reliability
If the DC bus voltage is boosted to the target voltage with slow voltage change, then the controllability is maintained, but a voltage necessary for driving the motor is not obtained and an overcurrent flows through the motor
Solution Approach 1:
The control device dynamically adjusts the voltage change speed during boosting operation. When the motor requires higher voltage, the system increases the voltage change speed to prevent overcurrent while maintaining controllability through coordinated control of the inverter circuit's switching elements.
3Ease of operation
If the modulation degree is used to determine boosting operation stop, then the boosting operation can be stopped appropriately, but the reference modulation degree must be updated at each starting operation completion which adds control complexity
Solution Approach 1:
The patent uses feedback by detecting the modulation degree during boosting operation and comparing it with a reference modulation degree. The boosting operation stop determination unit continuously monitors the modulation degree and determines when to stop boosting based on whether the detected value exceeds the reference value, creating a closed-loop control system.
Solution Approach 2:
The reference modulation degree is pre-calculated and stored before the boosting operation begins. This preliminary action allows the system to have a predetermined threshold for stopping boosting, simplifying the real-time decision-making process during operation.
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
Ensures stable operation of the motor drive control apparatus during starting and stopping operations by controlling the booster circuit's boosting operations, preventing overcurrent and improving the efficiency and controllability of the system.
Implementation Method 1
a rectifier (10) to convert an AC voltage supplied from an AC source (6) into a DC bus voltage
Implementation Method 2
In the booster circuit, energy is stored in the reactor (21) in ON period of the switching element (22) and the stored energy is discharged in OFF period of the switching element (22), to thereby boost the DC bus voltage
Implementation Method 3
an inverter circuit (40) to convert the DC bus voltage into an AC voltage and supply the AC voltage to a motor (2M)
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A motor drive control apparatus (1) according to the present invention includes: a three-phase rectifier (10) to rectify an AC voltage supplied from a three-phase AC source (6); a booster circuit (20) including a reactor (21), a switching element (22), and a backflow preventing element (23), to boost a DC bus voltage supplied from the three-phase rectifier (10); a smoothing capacitor (30) to smooth an output of the booster circuit (20); and an inverter circuit (40) to convert the DC bus voltage smoothed by the smoothing capacitor (30) into an AC voltage and supplying the AC voltage to a motor. During a starting operation of a boosting operation of the booster circuit (20) or a stopping operation of the boosting operation thereof, a rotation speed of the motor is fixed.