Motor Driving Apparatus Phase Current Estimation
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Solution Overview
Problem
Existing motor driving apparatuses lack accurate phase current calculation methods, especially in sensorless systems, which can lead to inefficiencies and increased manufacturing costs due to the need for multiple current sensors and complex detection circuits.
Innovation Solution
A motor driving apparatus that includes an inverter, a DC-link resistor, and a controller for estimating phase current through space vector-based pulse width modulation control, using a single DC-link resistor for phase current detection and gradient calculation, even in intervals where direct detection is not possible, thereby reducing manufacturing costs and enhancing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple current sensors are used for accurate phase current detection, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines multiple current detection functions into a single DC-link resistor. By measuring the voltage across this single resistor and using coordinate transformation algorithms, the system can calculate all three phase currents (ia, ib, ic) without requiring separate current sensors for each phase, thus reducing device complexity while maintaining measurement precision
Solution Approach 2:
The patent introduces a DC-link resistor as an intermediary element that indirectly provides phase current information. Instead of directly measuring each phase current with separate sensors, the system uses the voltage across the DC-link resistor as an intermediate measurement point and derives all phase currents through mathematical transformation, simplifying the detection circuit
2Measurement precision
If phase current is estimated during intervals when direct detection is not possible, then measurement precision is maintained, but calculation complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing current gradient values for different switching states in a lookup table. During operation, when direct detection is not possible, the controller quickly retrieves pre-computed gradient values and uses them for estimation, reducing the real-time computational burden while maintaining accuracy
Solution Approach 2:
The patent implements feedback by continuously comparing estimated current values with actual sampled values and adjusting the estimation algorithm accordingly. The controller uses the relationship between voltage vector application times and current gradients, with feedback from actual system behavior, to refine phase current calculations during intervals when direct detection is unavailable
3Ease of manufacture
If a single DC-link resistor is used for current detection, then manufacturing cost is reduced, but measurement precision may deteriorate
Solution Approach 1:
The patent replaces the mechanical/electrical system of multiple direct current sensors with an electrical measurement system using voltage detection across a single DC-link resistor. By substituting direct current measurement with voltage measurement and mathematical transformation, the system reduces component count and manufacturing cost while achieving equivalent or superior measurement precision through algorithmic compensation
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 allows for accurate phase current calculation without the need for multiple sensors, reducing costs and noise, and improves the overall efficiency of motor control by stabilizing phase current estimation across varying voltage vector application times.
Implementation Method 1
a DC-link resistor disposed between the DC-link capacitor and the inverter, and a controller for controlling the inverter based on a phase current sampled through the DC-link resistor
Data Source
AI summary
The present invention relates to a motor driving apparatus and a home appliance including the same. A motor driving apparatus according to an embodiment of the present invention includes an inverter for converting a DC voltage of a DC-link capacitor into an AC voltage according to a switching operation and outputting the converted AC voltage to a motor; a DC-link resistor disposed between the DC-link capacitor and the inverter; and a controller for controlling the inverter based on a phase current sampled through the DC-link resistor, wherein the controller estimates a phase current based on the phase current sampled through the DC link resistor, in an interval in which phase current detection is not possible. Thereby, the phase current flowing through the motor may be accurately calculated using the DC link resistor.