Inverter Control Device for Motor Efficiency with Small Capacitance
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Solution Overview
Problem
Inverter control devices with small capacitance face efficiency reduction due to pulsating DC voltage, leading to torque pulsations and reduced motor driving efficiency, and conventional methods to mitigate this either increase armature current or reduce regenerative energy efficiency.
Innovation Solution
The device controls regenerative energy to a predetermined value, optimizing the efficiency of the converter and inverter system by utilizing a motor with a higher reluctance torque ratio and adjusting electric current phases to minimize input power, thereby reducing regenerative energy and maintaining constant magnetic flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a smoothing capacitor with small capacitance is used, then capacity and cost are reduced, but DC voltage pulsations increase causing torque pulsations and reduced motor driving efficiency
Solution Approach 1:
The invention changes the control parameters of the inverter by adjusting the PWM signal output timing based on the detected polarity of the smoothing capacitor current. This dynamic parameter adjustment allows the system to compensate for voltage pulsations without requiring a large smoothing capacitor, thus reducing capacitor capacitance while maintaining motor driving efficiency.
Solution Approach 2:
The invention implements a feedback mechanism by detecting the current flowing through the smoothing capacitor and using this information to adjust the PWM signal timing. The control device detects the capacitor current polarity and accordingly adjusts the inverter output voltage phase, creating a closed-loop control system that maintains efficient motor operation despite small capacitor capacitance.
2Loss of energy
If PWM signal output timing is advanced to compensate for DC voltage pulsations, then motor driving efficiency is maintained, but armature current increases due to field weakening control
Solution Approach 1:
The invention uses feedback control by detecting the smoothing capacitor current and adjusting PWM timing accordingly. This feedback mechanism allows precise control that maintains motor driving efficiency without causing excessive armature current increase, as the timing adjustment is directly correlated with the actual capacitor charging/discharging state rather than using general field weakening control.
Solution Approach 2:
The invention dynamically adjusts the PWM signal timing based on real-time capacitor current detection. This dynamic adjustment allows the system to optimize motor driving efficiency moment-by-moment without continuously applying field weakening control, thereby avoiding sustained high armature current conditions while maintaining efficiency during voltage pulsations.
3Loss of energy
If regenerative energy is reduced to optimize converter efficiency, then overall system efficiency improves, but control complexity increases
Solution Approach 1:
The invention uses straightforward feedback based on capacitor current polarity detection to optimize converter efficiency. By simply advancing or retarding PWM timing based on whether the capacitor is charging or discharging, the system achieves efficient regenerative energy management without complex control algorithms, maintaining low control complexity while improving converter efficiency.
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 approach optimizes the entire motor driving system efficiency by minimizing regenerative energy and input power, reducing torque pulsations and maintaining efficient motor operation despite small capacitance.
Implementation Method 1
a smoothing portion constructed with a capacitor having a significantly-small capacitance is connected to an output terminal of a rectification portion
Implementation Method 2
the inverter is configured that the smoothing capacitor is unnecessary or have a largely-reduced capacitance, this causes the DC voltage resulted from the rectification to pulse in synchronization with the AC power supply
Implementation Method 3
An inverter control devices for driving an ordinary motor are adapted to rectify an AC power supply and smoothen the DC electric power resulted from the rectification
Data Source
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AI summary
A driving control portion 6 in an inverter control device structured by a capacitor 32 having a smaller capacitance includes a magnetic-flux estimation portion 17 for estimating a flux linkage in a motor 5 based on an electric current in the motor 5 having a higher ratio of a reluctance torque detected by an electric current detection portion 7, an electric-current phase-difference adjustment portion 14 for adjusting a phase difference between the electric current and an induced voltage generated by the motor 5, and an electric power calculation portion 20 for calculating input electric power to the motor 5, from an output voltage from a DC/AC conversion portion 4, and from the electric current from the electric-current detection portion 7, wherein the electric-current phase-difference adjustment portion 14 performs a phase adjustment, such that an estimated flux-linkage value estimated by the magnetic-flux estimation portion 17 is equal to or less than a predetermined set value and, an average value of the input electric power obtained by the electric power calculation portion 20 has a minimum value, thereby optimizing the efficiency of a motor driving system.