In Active Harmonic Filter (AHF), the function of an Insulated Gate Bipolar Transistor (IGBT) is to control the compensation currents that are generated to counteract the harmonic currents in an electrical power system. IGBTs are used as the main switching devices in AHFs due to their ability to handle high voltages and currents.
Here's a step-by-step explanation of how IGBTs function in an Active Harmonic Filter:
Sensing: The AHF monitors the electrical system for harmonic currents and measures their magnitude and phase angles using current sensors.
Signal Processing: The sensed current signals are processed using digital signal processing techniques to determine the required compensation current.
Control Logic: The control logic of the AHF generates the control signals based on the processed information. These control signals determine when and how much compensation current should be injected into the power system.
IGBT Switching: The control signals are fed to the gate terminals of the IGBTs. The IGBTs act as electronic switches, controlling the flow of compensation current to the power system. When the IGBT is turned on, it allows the compensation current to flow, and when it is turned off, it stops the flow of compensation current.
Filtering Action: The compensation current generated by the AHF is an inverted replica of the harmonic currents in the system. By injecting this compensating current with appropriate phase and magnitude, the AHF cancels out the harmonic currents, resulting in a clean sinusoidal waveform at the point of common coupling (PCC).
The IGBTs in an AHF need to operate at high switching frequencies to effectively cancel out the harmonics. They must also be able to handle the high voltages and currents present in the power system while maintaining accurate control. The IGBTs are typically incorporated into power converter circuits, along with other components such as capacitors and inductors, to form the complete Active Harmonic Filter system.
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