Motor Inverter Boost Control With Low-Capacitance DC Link
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Solution Overview
Problem
Existing motor driving devices for air conditioners face challenges in enhancing voltage utilization ratio and reducing maximum voltage between DC terminals when using low-capacitance capacitors, which affects stability and efficiency.
Innovation Solution
Incorporating a boost converter and inverter with switching devices, along with a low-capacitance DC terminal capacitor, to control and convert input AC power into smoothed DC power and then three-phase AC power for the motor, while using higher harmonics to reduce ripple voltage and enhance power factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a low-capacitance capacitor is used in the motor driving device, then the device complexity and energy loss are reduced, but the voltage utilization ratio deteriorates and the maximum voltage between DC terminals increases
Solution Approach 1:
The patent applies parameter changes by actively controlling the switching timing of the bridge circuit based on the phase of the AC input voltage. By synchronizing the switching operations with the voltage phase, the system optimizes the voltage waveform characteristics, thereby improving the voltage utilization ratio even with low-capacitance capacitors. This dynamic parameter adjustment resolves the contradiction between reduced capacitance and maintained voltage utilization.
2Device complexity
If a low-capacitance capacitor is used, then the device complexity is reduced, but the stability of motor driving deteriorates due to increased ripple voltage
Solution Approach 1:
The patent dynamically adjusts switching parameters based on detected voltage phase information. By changing the switching timing and duration according to the AC voltage phase, the system compensates for the reduced smoothing capability of low-capacitance capacitors, thereby maintaining motor driving stability despite using smaller capacitors.
Solution Approach 2:
The patent employs feedback mechanisms by detecting the phase of the AC input voltage and using this information to control the switching timing of the bridge circuit. This closed-loop control ensures that switching operations are synchronized with the voltage waveform, compensating for ripple voltage effects and maintaining stable motor operation even with reduced capacitor capacitance.
3Loss of energy
If a low-capacitance capacitor is used, then the energy loss is reduced, but the maximum voltage between DC terminals increases affecting circuit device durability
Solution Approach 1:
The patent controls the switching parameters of the bridge circuit based on the detected voltage phase, thereby optimizing the voltage waveform. By adjusting switching timing and duration dynamically, the system reduces peak voltage excursions while maintaining energy efficiency, thus protecting circuit devices from excessive voltage stress despite using low-capacitance capacitors.
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 solution enhances voltage utilization ratio, stabilizes motor driving, reduces iron and copper losses, and increases the durability of circuit devices by minimizing peak voltage and phase current, thereby improving overall motor driving efficiency.
Implementation Method 1
a rectifier to rectify input alternating current (AC) power
Implementation Method 2
a boost converter to boost and to output the power rectified by the rectifier
Implementation Method 3
an inverter including a plurality of switching devices and to output converted AC power to a motor using a voltage from the boost converter
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A motor driving device (200) and an air conditioner (100) including the same are disclosed. The motor driving device (200) includes a rectifier (410) to rectify input alternating current (AC) power, a boost converter (420) to boost and to output the power rectified by the rectifier (410), and an inverter (220) including a plurality of switching devices and to output converted AC power to a motor (250) using a voltage from the boost converter (420). Accordingly, a voltage utilization ratio of a voltage input to an inverter in the motor driving device using a low-capacitance capacitor (C) is enhanced.