Addressing harmonic issues, suppressing radiation interference, and power supply system disturbances can be achieved through techniques such as shielding, isolation, grounding, and filtering. The main measures for harmonic control include: increasing the system short-circuit capacity; raising the voltage level of power supply; enhancing the pulsation number of the converter devices; improving the operational mode of the system; and setting up AC filters, all of which can reduce the harmonic content within the system. AC filters are categorized into passive and active filters. Active filters are a type of active filtering device that injects compensating harmonic currents into the system to offset the harmonics generated by nonlinear loads. They can quickly dynamically track and compensate for changing harmonics, and their compensation characteristics are not affected by system impedance. Aviation ground power: 2, 36V aviation power supply; 1, 400HZ variable frequency power supply; 7, 115/200V power supply; 2, 27V DC power supply; 5, 400HZ power supply; 12, aviation power supply.
The structure is relatively complex, with high operational losses and high equipment costs; while compensating for harmonic distortions, it also introduces new harmonics. The passive filter, also known as an LC filter, utilizes the LC resonance principle to artificially create a series resonance branch, providing a low-impedance path for the main harmonics to be filtered out, preventing them from being injected into the power grid. The LC filter has a simple structure and demonstrates significant harmonic absorption effects; however, it only offers good compensation for harmonics at its inherent frequencies. Moreover, its compensation characteristics are greatly influenced by the grid impedance, and at specific frequencies, parallel or series resonance may occur between the grid impedance and the LC filter.
