Motor driving apparatus and air conditioner including the same
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Solution Overview
Problem
Existing motor driving apparatuses for air conditioners face challenges in reducing harmonics, particularly orders 5, 7, 11, and 13, without detecting input current, which leads to harmonic distortion in the current outputted to the inverter, and require additional communication lines for harmonic compensation.
Innovation Solution
A motor driving apparatus with a rectifier, capacitor, harmonic reducer, current and voltage detectors, and a controller that reduces harmonics without detecting input current, using a harmonic reducer with switching elements and capacitors to control harmonics based on detected voltage and current, and is disposed on separate circuit boards to enhance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a film capacitor is used instead of an electrolytic capacitor, then the capacitor size is reduced, but the capacitance becomes lower causing larger voltage ripple and increased harmonic components
Solution Approach 1:
The capacitor system is segmented into two parts: a film capacitor for size reduction and a ceramic capacitor for ripple suppression. This segmentation allows each capacitor type to perform its optimal function - the film capacitor provides compact size while the ceramic capacitor compensates for its low capacitance by suppressing voltage ripple and harmonic components.
Solution Approach 2:
The invention uses a composite capacitor configuration combining film capacitor and ceramic capacitor with different electrical characteristics. The film capacitor (lower capacitance, compact size) and ceramic capacitor (higher capacitance, low ESR) work together as a composite system to achieve both size reduction and voltage ripple suppression that neither capacitor could achieve alone.
2Measurement precision
If input current detection is performed for harmonic compensation, then harmonic reduction accuracy is improved, but additional communication lines and device complexity are required
Solution Approach 1:
The invention extracts and eliminates the unnecessary input current detection function from the harmonic compensation system. By using only voltage detection combined with harmonic reduction circuit control, it removes the need for separate current detection circuits and communication lines while maintaining effective harmonic compensation through voltage-based control signals.
Solution Approach 2:
The invention introduces a voltage-based intermediary control mechanism where voltage detection signals serve as mediators to control the harmonic reduction circuit. Instead of directly detecting and compensating current harmonics, the system uses voltage as an intermediary parameter to indirectly control and reduce current harmonics, simplifying the overall system architecture.
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
Efficient reduction of specific order harmonics and harmonic distortion in the current flowing through the inverter, meeting THD and PWHD standards without additional communication lines, thereby reducing production costs.
Implementation Method 1
a rectifier configured to rectify a three-phase alternating current (AC) voltage
Implementation Method 2
a capacitor configured to store a pulsating voltage from the rectifier
Implementation Method 3
a harmonic reducer disposed between the rectifier and the capacitor and including at least one switching element and a second capacitor, and configured to reduce harmonics in the three-phase AC voltage
Data Source
Figure 1
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AI summary
A motor driving apparatus and an air conditioner including the same are disclosed. The motor driving apparatus includes: a rectifier; a capacitor to store a pulsating voltage from the rectifier; a first voltage detector to detect the pulsating voltage; a harmonic reducer disposed between the rectifier and the capacitor and including at least one switching element and a second capacitor, and to reduce harmonics in a three-phase AC voltage; a current detector to detect a current flowing in the harmonic reducer; a second voltage detector to detect a voltage at both ends of the second capacitor; an inverter to output a converted AC voltage to a motor; and a controller to control the harmonic reducer, based on the pulsating voltage, the current detected by the current detector, and the voltage detected by the second voltage detector. Accordingly, it is possible to reduce harmonics without detecting an input current.