Flight safety has always been a top priority in airport construction. As a convenient mode of transportation for people's daily transportation, airplanes have brought diverse choices to people's daily transportation and life. However, in the low-voltage distribution system of airports, there are a large number of harmonic sources, such as airport navigation lights, DC motors, electric furnaces, rolling mills, welding machines, etc. These harmonic sources have characteristics such as large current distortion, wide harmonic spectrum range, and rapid changes in reactive power demand, Becoming the first level of flight safety. Fortunately, an active filter has appeared at a critical moment, and its role is crucial.
Harmonic hazards at airports
The fundamental reason for the generation of harmonics in the power system is the transmission, distribution, and consumption equipment with nonlinear volt ampere characteristics. When the current flows through a nonlinear load, it does not have a linear relationship with the applied voltage, forming a non sine wave current and generating harmonics. Harmonic pollution is increasingly threatening the safety, stability, and economic operation of power systems, and has a significant impact on linear loads and other users in the same network. The harmonics generated by such loads can endanger the normal operation of the distribution system and even cause serious electrical accidents. Taking the airport navigational lighting system as an example, the load equipment of navigational lighting continues to increase, and a large number of controllable silicon dimming devices are used in airport lighting stations, resulting in a large amount of harmonic currents and pollution to power quality. At the same time, additional currents and thermal effects also pose certain risks to the safety of various electrical equipment and cable lines. Therefore, it is extremely important to analyze and manage the power harmonic problem of airport navigation aid lighting stations.
At present, there are two main mainstream methods for harmonic control in the power system: passive filtering technology and active filtering technology. The high-power power semiconductor dimming equipment used in the airport lighting station will produce a large number of high-order harmonics (mainly all odd harmonics except three times of the third harmonic), while the passive filter must design a single resonance filter for each harmonic, and the design parameters must be related to the system impedance (calculation of the system impedance is tedious, and the system impedance will change as the system expands year by year); Passive filtering cannot completely eliminate harmonics, but there is a risk of amplifying resonance; The aging of capacitors can also cause the original design resonance point to shift and fail to achieve the goal of filtering out target harmonics; Passive filtering systems are suitable for situations with single and stable loads.
Compared with passive filters, active filter systems have high controllability and fast response (≤ 1ms), can compensate for various harmonics, suppress flicker, and compensate for reactive power. They have the characteristic of one machine with multiple functions; Reasonable in terms of cost-effectiveness; The filtering characteristics are not affected by the system impedance, which can eliminate the danger of resonance with the system impedance; With adaptive function, it can automatically track and compensate for changing harmonics. The basic principle is to detect harmonic current from the load circuit of the harmonic source (compensated object), and the compensation device generates a compensation current waveform that is equal in magnitude but opposite in phase to the harmonic current. This is used to offset the harmonic current generated by the harmonic source load, so that the grid side current only contains the fundamental component.