Current Compensation Inverter Control for Harmonic Compliance
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Solution Overview
Problem
Existing power converters struggle to effectively reduce harmonic components in the power-source current supplied to them from alternating-current power sources, which can lead to non-compliance with harmonic current emission standards like IEC61000-3-2.
Innovation Solution
The power converter incorporates a current compensation unit with a compensation controller and a drive signal generator that uses a three-phase modulation method to generate a drive signal for switching elements, ensuring that the compensating current reduces harmonic components in the power-source current. The dead time for the drive signal is optimized based on the carrier frequency and maximum input power to meet harmonic standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current compensation unit with three-phase modulation is added to reduce harmonic components, then harmonic current emission compliance is improved, but device complexity increases
Solution Approach 1:
The patent combines the power conversion unit and current compensation unit into a single integrated power converter system. The current compensation unit shares the same DC voltage source and control structure, merging multiple functions into one device. This reduces overall system complexity while achieving harmonic current emission compliance through the coordinated operation of both units.
Solution Approach 2:
The power converter is designed with multi-functionality, where the same basic structure serves both power conversion and current compensation purposes. The switching elements and control circuitry are utilized for both primary power conversion and harmonic compensation, making the device universally applicable for multiple functions without requiring separate dedicated components.
2Reliability
If dead time is increased to ensure proper switching operation, then switching reliability is improved, but harmonic component reduction effectiveness deteriorates
Solution Approach 1:
The patent dynamically adjusts the dead time parameter based on operating conditions such as carrier frequency and power level. By optimizing dead time as a variable parameter rather than using a fixed value, the system maintains reliable switching operation while minimizing the negative impact on harmonic reduction effectiveness. The dead time is calculated to satisfy both switching reliability and harmonic emission requirements.
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 effectively reduces harmonic components in the power-source current, ensuring compliance with IEC61000-3-2 harmonic current emission standards, thereby improving the efficiency and reliability of the power converter.
Implementation Method 1
The current compensation unit inverter supplies, by switching operation of switching elements, a compensating current to the alternating-current power source
Implementation Method 2
a drive signal generator that generates, based on the output voltage command value, a drive signal usable to drive the switching elements by a three-phase modulation method
Implementation Method 3
a current compensation unit reactor connected between the alternating current side of the current compensation unit inverter and the alternating-current power source
Implementation Method 4
a current compensation unit capacitor connected between direct-current-side nodes of the current compensation unit inverter
Data Source
AI summary
A power converter includes a power conversion unit for a three-phase alternating current output from an alternating-current power source, and a current compensation unit that supplies a compensating current to the alternating-current power source. The current compensation unit includes a current compensation unit inverter including switching elements, a current compensation unit capacitor, a current compensation unit reactor, a compensation controller that obtains an output voltage command value, and a drive signal generator that generates a drive signal usable to drive the switching elements by a three-phase modulation method. The current compensation unit inverter supplies the compensating current to the alternating-current power source via the current compensation unit reactor. Td≤(34.00/fsw−0.145)(1.55−0.055*Pmax), where fsw represents a carrier frequency employed for generation of the drive signal, Pmax represents a maximum input power of the power conversion unit, and Td represents a dead time for the drive signal.