Power Converter Harmonic Suppression via Dynamic Compensation
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Solution Overview
Problem
Power converters without electrolytic capacitors face challenges in reducing harmonics caused by motor rotation, as existing harmonic suppressors are ineffective for frequencies mismatched with the power supply frequency.
Innovation Solution
A power converter design that uses a compensation controller to generate active and reactive voltage instruction values, canceling harmonic components from motor rotation and power supply voltage periods, with active and reactive current controllers delaying components to match phase and reduce harmonic influence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a power converter is designed without electrolytic capacitors to reduce size, then the device size is reduced, but harmonic components in the power supply current increase due to pulsations in DC voltage and active power
Solution Approach 1:
The patent introduces a current compensator as an intermediary device that includes a compensation current generator and a current compensating capacitor. This compensator generates compensation currents that cancel out the harmonic components in the power supply current, thereby resolving the contradiction between reduced device size and harmonic reduction without requiring large electrolytic capacitors in the main power converter
2Object-generated harmful factors
If existing power supply harmonic suppressors are used to compensate for harmonics, then harmonics with power supply frequency periodicity are reduced, but harmonics caused by motor rotation at various velocities cannot be compensated due to frequency mismatch
Solution Approach 1:
The patent implements a dynamic compensation approach where the compensation controller dynamically adjusts the compensation currents based on the actual motor rotation speed and frequency characteristics. The system uses feedback from current detectors and a speed sensor to adapt the compensation parameters in real-time, enabling effective compensation for harmonics caused by motor rotation at various velocities rather than being fixed to power supply frequency only
3Quantity of substance
If small-capacitance capacitors are used instead of large electrolytic capacitors, then device size and component count are reduced, but pulsations in DC voltage and active power increase
Solution Approach 1:
The current compensator acts as a mediator that compensates for the instability caused by using small-capacitance capacitors. By generating appropriate compensation currents, the compensator smooths out the pulsations in active power and helps maintain DC voltage stability, thereby allowing the use of smaller capacitors without sacrificing stability
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
Significantly reduces harmonics in the power supply current, even with small capacitance capacitors, ensuring compliance with harmonic regulations and minimizing capacitor and reactor size.
Implementation Method 1
a rectifier configured to rectify alternating current supplied from an AC power supply and output pulsating direct current
Implementation Method 2
a voltage-type inverter for converting the DC voltage into an AC voltage
Implementation Method 3
a compensation current generator having an input connected to the AC power supply and an output connected to the current compensating capacitor and performing a switching operation in accordance with a drive signal, thereby controlling compensation currents flowing between itself and the AC power supply
Data Source
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AI summary
Disclosed herein is a technique for reducing harmonics resulting from the rotation of a motor and generated in a power supply current. This power converter device includes a compensation current generator (52) configured to control compensation currents (Icr, Ics, Ict) flowing between itself (52) and an AC power supply (12), and a compensation controller (60; 260) configured to obtain output voltage instruction values (Vid, Viq) such that the compensation currents (Icr, Ics, Ict) cancel a harmonic component in load currents (Ir, Is, It) flowing from the AC power supply (12) into a rectifier (22) and resulting from the rotation of the motor (16) and a harmonic component in the load currents (Ir, Is, It) and dependent on a period (Ts) of a voltage of the AC power supply (12).