Sensorless Motor Start with Modular Multilevel Cascade Inverter
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Solution Overview
Problem
Existing motor starting methods using modular multilevel inverters face issues with voltage fluctuation and excess current during slow speed operations, and require speed sensors for stable variable speed driving, which can be impractical for large-capacity fans or blowers.
Innovation Solution
A speed sensorless motor starting method using a modular multilevel cascade inverter with chopper cells and a three-terminal coupled reactor, where a current command value is created by increasing amplitude and frequency from 0 to a prescribed value over a predetermined period, allowing motor start control without a speed sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a speed sensor is used for stable variable speed driving, then motor control stability is improved, but device complexity and cost increase
Solution Approach 1:
The invention extracts and eliminates the speed sensor component from the motor control system. By using sensorless control methods that rely on motor back-EMF and current measurements instead of direct speed feedback, the system achieves stable variable speed operation without the complexity and cost of speed sensors, particularly suitable for large-capacity fans or blowers where sensor installation is impractical
2Productivity
If frequency and amplitude are increased rapidly during motor start, then productivity is improved, but torque pulsation and voltage fluctuation increase
Solution Approach 1:
The invention implements dynamic control of the frequency and amplitude increase rate during motor starting. By adaptively adjusting the ramp rate based on motor characteristics and load conditions, the system achieves rapid yet stable motor acceleration. The control dynamically balances the need for quick start (productivity) with torque stability, preventing excessive torque pulsation and AC voltage fluctuation while maintaining high start speed capability
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 method stabilizes motor start and reduces torque pulsation, eliminates excess current, and suppresses AC voltage fluctuation, enabling efficient variable speed operation without a speed sensor, suitable for devices with gentle speed and torque changes.
Implementation Method 1
a modular multilevel cascade inverter (MMCI) of a double star chopper cell (DSCC)
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A speed sensorless motor starting apparatus (100) for starting a motor includes a modular multilevel cascade inverter (1) of a double star chopper cell, a current command value creation unit (31) configured to create a current command value by using an amplitude command value and a frequency command value increased from 0 to a prescribed value over a predetermined period of time, and a motor start control unit (32) configured to start the motor by performing control so that a motor driving current output from the modular multilevel cascade inverter (1) to the motor can follow the current command value.