Rectangular Wave Control Device for Electric Motor Driving Apparatus
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Solution Overview
Problem
Existing electric motor driving apparatuses face inefficiencies due to limited usage of rectangular wave control at low rotation speeds, leading to torque ripples and reduced efficiency, as they rely on boosting system voltage to high speeds for optimal performance.
Innovation Solution
A control device that performs rectangular wave control with adjustable switching timings based on system voltage changes, ensuring time-integrated voltage values across phases remain balanced, allowing for low-switching loss operation from lower rotation speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If rectangular wave control is performed from lower rotation speed region, then switching loss is reduced and efficiency is improved, but system voltage variation disrupts voltage balance among phases causing torque ripple
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the ON/OFF timings of switching elements based on the rate of change of system voltage. This allows the rectangular wave control to maintain voltage balance among phases even when system voltage varies, enabling efficient operation at lower rotation speeds without causing torque ripple.
Solution Approach 2:
The patent implements feedback control by using the detected rate of change of system voltage to adjust the switching element timings. The control device continuously monitors system voltage variations and modifies the rectangular wave output timing accordingly, creating a closed-loop system that prevents torque ripple while maintaining low switching loss.
2Stability of the object's composition
If system voltage is boosted to maximum system voltage before performing rectangular wave control, then voltage balance is maintained, but usage region of rectangular wave control is limited to high rotation speed region
Solution Approach 1:
The patent applies preliminary action by proactively adjusting the switching element timings in response to system voltage variations before severe imbalance occurs. This allows rectangular wave control to be performed at lower rotation speeds without waiting for the system voltage to reach maximum levels, thereby expanding the usable rotation speed range.
Solution Approach 2:
The patent implements dynamics by making the switching element timings adjustable and responsive to real-time system voltage conditions. Instead of using fixed timings, the control device dynamically modifies the ON/OFF timings based on the rate of change of system voltage, enabling flexible operation across a broader rotation speed range while maintaining voltage balance.
3Stability of the object's composition
If PWM control is used instead of rectangular wave control, then voltage balance is easier to maintain, but switching loss increases and efficiency decreases
Solution Approach 1:
The patent applies parameter changes by modifying the ON/OFF timings of switching elements during rectangular wave control to compensate for system voltage variations. This maintains voltage balance among phases while preserving the low switching loss characteristics of rectangular wave control, avoiding the need to switch to higher-loss PWM control.
Solution Approach 2:
The patent implements feedback control by continuously monitoring system voltage and adjusting switching element timings accordingly. This closed-loop approach maintains voltage balance during rectangular wave control, eliminating the need to resort to PWM control and its associated higher switching losses.
Data Source
AI summary
A control device for an electric motor driving apparatus, configured with a switching control unit that performs rectangular wave control in which a plurality of switching elements provided in a direct current-alternating current conversion unit are ON/OFF-controlled to output rectangular wave-shaped voltages of a plurality of phases. System voltage varies during execution of the rectangular wave control, the switching control unit performs rectangular wave width adjustment control to set ON/OFF timings of the plurality of switching elements on the basis of a rate of change of the system voltage such that time-integrated values of the rectangular wave-shaped voltages of the respective phases within a control period set at a length corresponding to an integral multiple of a single electrical angle period are substantially identical among the respective phases.