AC Motor Drive System Loss Minimization via Dynamic Pulse Control
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Solution Overview
Problem
Existing AC motor drive systems face inefficiencies due to unoptimized switching frequency and number of pulses, leading to increased harmonic and fundamental wave losses, which vary with load conditions, making it challenging to maximize overall system efficiency.
Innovation Solution
The AC motor drive system dynamically adjusts the carrier frequency and number of pulses based on the drive frequency, load state, and DC voltage to minimize total losses by employing a carrier frequency determiner, number of pulses compensator, and real-time loss computing units, ensuring optimal operation and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If synchronous PWM is employed to suppress increase in number of times of switching, then the switching frequency is controlled, but complex control is required to achieve maximum efficiency in the entire drive system
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing optimal switching frequencies and pulse numbers in map storage before operation. The optimal values are determined based on offline analysis of the relationship between switching frequency, pulse number, and losses for various operating conditions. During operation, the control device simply retrieves the appropriate values from the map based on current fundamental wave frequency and modulation rate, avoiding complex real-time optimization calculations.
Solution Approach 2:
The patent introduces an intermediary element - the map storage - that mediates between the complex loss optimization problem and the simple control execution. The map acts as a pre-computed lookup table that translates operating conditions (fundamental wave frequency and modulation rate) into optimal control parameters (switching frequency and pulse number). This intermediary structure simplifies the control algorithm while maintaining optimization performance.
Data Source
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AI summary
It is an object of the invention to realize minimization of the total loss from magnification relationships among a fundamental wave loss generated by an AC motor, a loss of an inverter that drives the motor, and a loss generated by a harmonic of the inverter. Since the fundamental wave loss is increased along with the increase in load of the AC motor, a switching frequency of the inverter is lowered to reduce the fundamental wave loss, and the loss caused by fundamental wave current is lowered, so that the efficiency of a system is improved. In contrast, since the harmonic loss of the AC motor is dominant in a light load area, the efficiency is maximized by increasing the switching frequency of the inverter or the number of pulses and reducing a harmonic current.