Motor Inverter Current Sampling Synchronized for Stable Sensorless Control
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Solution Overview
Problem
Existing motor driving apparatuses, particularly those using the sensorless method, face challenges in precisely calculating phase currents flowing into motors, leading to inaccurate motor control and reduced stability, especially at high speeds.
Innovation Solution
A motor driving apparatus that includes an inverter converting DC power into AC power, a dc stage resistance element, and a control unit synchronizing the frequency of the voltage or rotating frequency of the motor with the sampling frequency of the phase current, allowing for precise calculation of phase currents using a single dc stage resistance element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a sensorless method is used to reduce manufacturing cost, then manufacturing cost is reduced, but measurement precision of phase current deteriorates
Solution Approach 1:
The patent introduces a DC stage resistance element as an intermediary component to enable phase current measurement in a sensorless motor driving apparatus. By placing this resistance element in the DC power supply line, the system can calculate phase currents through voltage measurements across the resistance, achieving accurate current detection without requiring expensive sensors in each motor phase.
Solution Approach 2:
The patent replaces physical current sensors with an electrical calculation method. Instead of using mechanical/electronic sensing devices to directly measure phase currents, the system substitutes this with an electrical calculation approach using voltage measurements across a DC stage resistance element and computational algorithms to derive phase current values.
2Measurement precision
If sampling frequency is increased to improve measurement precision, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent implements periodic sampling of the DC stage voltage at specific intervals synchronized with the motor's electrical cycle. By sampling at predetermined periods corresponding to the motor's operating frequency, the system achieves accurate phase current measurement without requiring continuous high-frequency sampling, thus maintaining measurement precision while avoiding excessive device complexity.
3Stability of the object's composition
If frequency synchronization is implemented to improve stability, then stability is improved, but device complexity increases
Solution Approach 1:
The patent employs feedback control by continuously monitoring the relationship between the sampling frequency and the motor's electrical frequency, and adjusting the sampling timing accordingly. This feedback mechanism ensures that phase current measurements are always synchronized with the motor's operating state, maintaining stability without requiring complex external synchronization hardware.
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 enables precise calculation of phase currents, improves motor control accuracy, and stabilizes motor operation at high speeds by synchronizing frequencies, enhancing transient response and reducing torque ripple.
Implementation Method 1
an inverter converting DC power of a dc stage capacitor into AC power by a switching operation
Implementation Method 2
the control unit controls the frequency of a voltage applied to the motor or the rotating frequency of the motor and the sampling frequency of the phase current sampled through the dc stage resistance element so that the frequency of the voltage or the rotating frequency of the motor and the sampling frequency of the phase current are synchronized
Implementation Method 3
a phase current sampled through the dc stage resistance element
Data Source
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Figure 5~6b
AI summary
The present invention relates to a motor driving apparatus and a home appliance comprising the same. The motor driving apparatus according to an embodiment of the present invention comprises: an inverter which converts a direct current power source of a DC stage capacitor to an alternating current power source and outputs the converted alternating power source to a motor by a switching operation; a DC stage resistance device arranged between the DC stage capacitor and the inverter; and a control unit which controls the inverter on the basis of phase current sampled by means of the DC stage resistance device, wherein the control unit controls the frequency of voltage applied to the motor or the rotation frequency of the motor to be synchronized with the sampling frequency of the phase current sampled via the DC stage resistance device. Accordingly, it is possible to accurately calculate the phase current flowing through the motor by means of the DC stage resistance device.