Motor Drive Ripple Frequency Detection for Current Distortion Control
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Solution Overview
Problem
Existing motor drive devices face challenges in eliminating motor current distortion and torque pulsation due to direct current voltage ripples, requiring large smoothing capacitors that increase cost and size, and are sensitive to frequency differences and time delays in discrete control systems.
Innovation Solution
A motor drive device that estimates the ripple frequency of the direct current voltage and uses a sine wave transfer function controller to correct voltage command values, eliminating the need for additional components like high-pass filters and dedicated detection circuits, and employs a small-capacity smoothing capacitor to reduce size and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the capacity of the smoothing capacitor is increased to reduce voltage ripples, then the voltage ripple reduction is improved, but the cost and volume of the motor drive device increase
Solution Approach 1:
The invention extracts and addresses the voltage ripple problem not by enlarging the capacitor, but by detecting the ripple frequency and using control algorithms (current command correction) to compensate for its effects, thereby solving the ripple issue without adding volume
Solution Approach 2:
The invention changes the approach from passive ripple suppression (larger capacitor) to active ripple compensation by detecting ripple frequency and adjusting control parameters (current commands) dynamically, maintaining performance without increasing component size
2Object-affected harmful factors
If the capacity of the smoothing capacitor is increased to reduce voltage ripples, then the voltage ripple reduction is improved, but the cost of the motor drive device increases
Solution Approach 1:
The invention extracts the ripple frequency information from the system and uses it for active compensation through control algorithms, avoiding the need for expensive large-capacity capacitors while maintaining voltage stability
Solution Approach 2:
The invention replaces the passive mechanical/electrical solution (large capacitor) with an active control system that uses detection and correction algorithms, reducing both cost and complexity
3Object-generated harmful factors
If high-pass filters are used to extract high frequency components for eliminating beat phenomenon, then the beat phenomenon elimination is improved, but the device complexity increases due to additional components and fine adjustment requirements
Solution Approach 1:
The invention makes the existing controller perform multiple functions: it detects voltage ripple frequency, processes current commands, and eliminates beat phenomenon, all within the same control unit without adding dedicated hardware filters or detection circuits
Solution Approach 2:
The controller uses its own existing detection and processing capabilities to identify and compensate for beat phenomenon, making the system self-sufficient without requiring external additional components
4Object-generated harmful factors
If discrete controllers are used to implement high-pass filters, then the beat phenomenon elimination is improved, but the measurement precision deteriorates due to time delay from control period
Solution Approach 1:
The invention performs preliminary detection of the voltage ripple frequency and uses this information proactively in the control algorithm to preemptively compensate for beat phenomenon, reducing the impact of control delays
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 effectively eliminates motor current distortion and torque pulsation without large capacitors and additional components, maintaining performance across varying power supply frequencies.
Implementation Method 1
a rectifier circuit configured to convert an alternating current voltage supplied from an alternating power supply into a direct current voltage
Implementation Method 2
a smoothing capacitor configured to smooth a direct current voltage outputted from the rectifier circuit
Implementation Method 3
an inverter circuit configured to convert a direct current voltage outputted from the smoothing capacitor into an alternating current voltage
Data Source
AI summary
A motor drive that enables the elimination of distortion of a motor current caused by direct current voltage ripples with the use of a smoothing capacitor having a small capacity and refrigeration equipment. A motor drive includes a rectifier circuit, a smoothing capacitor, voltage detector, an inverter circuit, current sensor, and a controller configured to control the inverter circuit. The controller has a voltage controller configured to generate a voltage command value used for controlling the motor, a ripple frequency arithmetic unit configured to operate a ripple frequency included in the direct current voltage signal, and a harmonic suppressor configured to process a signal based on the direct current signal using an S controller having a gain near the ripple frequency and output a corrected amount. The inverter circuit is controlled based on a signal that the voltage command value is corrected using the corrected amount.