Inverter Phase Control for Motor Ripple Suppression
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Solution Overview
Problem
Conventional inverter devices face challenges in suppressing ripple and beat in motor current without lowering the voltage utilization factor, particularly when using electrolytic capacitors for smoothing, leading to increased motor current rms values and vibration.
Innovation Solution
An inverter device configuration that includes a converter section for full-wave rectification of three-phase AC voltage, an inverter section for AC voltage conversion, and a control device that adjusts the phase of the d-axis voltage relative to the q-axis voltage in a rotating coordinate system to lead the q-axis voltage by 90 degrees, effectively suppressing ripple and beat in the motor current without reducing voltage utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the modulation factor is corrected to eliminate ripple in the voltage applied to the motor, then ripple and beat in the motor current are suppressed, but the voltage utilization factor decreases to 86.6% of the maximum value
Solution Approach 1:
The invention changes the phase relationship between d-axis and q-axis voltage components as a parameter adjustment. By making the d-axis voltage lead the q-axis voltage by a specific phase angle (optimally 30 degrees), the invention eliminates motor current ripple while maintaining maximum voltage utilization factor, resolving the contradiction between ripple suppression and voltage utilization.
Solution Approach 2:
The invention introduces dynamic phase adjustment in the voltage commands applied to the inverter. The control device dynamically modifies the phase relationship between d-axis and q-axis voltages based on the ripple frequency characteristics, enabling adaptive suppression of motor current ripple while maintaining optimal voltage utilization under varying operating conditions.
2Use of energy by moving object
If the modulation factor is set to the maximum possible value to increase the voltage utilization factor, then the voltage utilization factor increases, but the motor output voltage pulsates causing ripple and beat in the motor current
Solution Approach 1:
The invention changes the phase relationship between d-axis and q-axis voltage components as a parameter adjustment. By making the d-axis voltage lead the q-axis voltage by a specific phase angle (optimally 30 degrees), the invention eliminates motor current ripple while maintaining maximum voltage utilization factor, resolving the contradiction between ripple suppression and voltage utilization.
Solution Approach 2:
The invention converts the harmful effect of DC voltage ripple into a beneficial control mechanism. By intentionally introducing a phase lead in the d-axis voltage that corresponds to the ripple frequency, the invention uses the ripple itself as a reference to generate compensating voltage commands that cancel out the harmful effects in the motor current, thereby maintaining maximum modulation factor without causing beat phenomena.
3Object-affected harmful factors
If large capacitors and reactors are used to smooth out voltage ripple, then voltage ripple is reduced, but the cost and volume of the inverter device increase
Solution Approach 1:
The invention extracts and eliminates the need for large smoothing capacitors and reactors by implementing a control-based ripple suppression method. The control device processes voltage commands to counteract ripple effects electronically, removing the requirement for bulky passive filtering components and thereby reducing the overall inverter device volume while effectively suppressing voltage ripple.
Solution Approach 2:
The invention replaces the mechanical/passive filtering approach (using large capacitors and reactors) with an active electronic control system. The control device uses computational processing of voltage commands to achieve ripple suppression, substituting physical filtering components with intelligent control algorithms that accomplish the same function with minimal 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 configuration enhances voltage utilization, reduces motor current ripple and beat, and minimizes the need for large capacitors and reactors, thereby reducing costs and component sizes.
Implementation Method 1
a converter section that full-wave rectifies a three-phase AC voltage and outputs a DC voltage including a ripple component having a frequency six times a frequency of the three-phase AC voltage
Implementation Method 2
an inverter section that converts the DC voltage including the ripple component from the converter section into an AC voltage and outputs the AC voltage to a motor
Implementation Method 3
a control device that, in a rotating coordinate in which an N-pole direction of a permanent magnet embedded in a rotor of the motor is taken as a d-axis and a direction orthogonal to the d-axis is taken as a q-axis, controls the inverter section so that a phase of a d-axis voltage Vd of the ripple component included in the DC voltage leads a phase of a q-axis voltage Vq
Data Source
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AI summary
An inverter device includes: a converter section (21) that full-wave rectifies a three-phase AC voltage and outputs a DC voltage including a ripple component having a frequency six times the frequency of the three-phase AC voltage; an inverter section (22) that converts the DC voltage including the ripple component from the converter section (21) into an AC voltage and outputs the AC voltage to a motor (23); and a control device (100) that, in a rotating coordinate in which an N-pole direction of a permanent magnet embedded in a rotor of the motor (23) is taken as a d-axis and a direction orthogonal to the d-axis is taken as a q-axis, controls the inverter section (22) so that a phase of a d-axis voltage Vd of the ripple component included in the DC voltage leads a phase of a q-axis voltage Vq. Thus, an inverter device capable of suppressing ripple and beat in a motor current without lowering the voltage utilization factor is provided.