Airport Power Supply System
The reliability of the airport power supply system directly affects the operating state of the airport and is closely related to the safety of people's travel. However, in recent years, safety incidents caused by harmonic and reactive power faults in the power supply system have occurred frequently, so it is necessary to pay enough attention to such events in the airport power supply system and take effective measures to enhance the stability of the airport power supply system. It is an important link to ensure the safety of the airport power supply system by evaluating the risks of the airport power supply system based on its current status and making a risk assessment. It has certain reference value for improving the stability of the airport power supply system.
1 The Mechanism of Reactive Power Generation in Airports The reactive power of a circuit represents the magnitude of energy exchange. In sinusoidal circuits, reactive power due to inductive components is typically taken as positive, while reactive power due to capacitive components is taken as negative. This can lead to some unreasonable situations in non-sinusoidal circuits, where the same harmonic source may have some harmonics with capacitive reactive power and others with inductive reactive power, which cancel each other out. In reality, different frequency reactive powers cannot be cancelled out and compensated for. In general, the waveform distortion of the grid voltage is small, while the waveform distortion of the grid current can be large. The size of the power factor in a non-sinusoidal circuit is determined jointly by the degree of distortion of the fundamental current and the phase shift of the fundamental current.
1.1 Analysis of Power Factor for Inductive-Resistive Loads and Rectifier Circuits
Air conditioners, elevators, and fans can generate certain inductive-resistive loads. Inverter-based variable-frequency control is typically used for these types of equipment. In the grid, the influence of the harmonics generated by the inverter can be ignored because there is an intermediate filtering stage, which is usually composed of capacitors or inductors, and can effectively filter out harmonics. Therefore, under the premise of steady-state operation, the influence of the rectification stage on the grid is analyzed using the three-phase bridge rectifier control circuit model.
1.2 Analysis of Rectifier Circuits with Filter Capacitors The rectifier circuit with filter capacitors in the terminal building includes UPS, computer monitors, signal monitoring and automatic ticketing and access control, which can effectively show the relationship between harmonic indicators, power factor, harmonic order, and circuit parameters. When the stable state appears in the capacitor filter diode single-phase bridge rectifier circuit, the diodes need to be effectively set, with VD1 and VD4 set separately. The diodes are turned on at θ distance from the zero point of the power supply voltage.
2. Analysis of the current situation of the airport power supply system
2.1 Composition of the current situation assessment of the airport power supply system
The assessment of the current situation of the airport's power supply system includes many aspects, including the specific power supply form of the airport, the use of emergency standby power, transformers and loads, relay protection systems, power supply systems, underground pipelines, substation management, management organizations, etc. Systematically analyze and evaluate these aspects, and then clarify the dangerous sources in the airport power supply system, and take targeted comprehensive measures for power supply system safety. The assessment of the dangerous sources in the airport power supply system is also a key to the assessment of the airport power supply system.
2.2 Basis for analyzing the current situation of the airport power supply system
The current situation of the airport's power supply system is analyzed mainly based on current laws and regulations. For example, the Electric Power Law of the People's Republic of China, etc., also needs to be referenced to specific industry standards of the state and the power system. Of course, it is also necessary to analyze the actual situation of the airport for analysis, such as local power grid equipment handover and preventive testing procedures, local power company's detailed regulations for on-grid operation of electricians, and local power bureau's regulations for the management of user-owned power sources.
3 Power Supply System Compensation Plan
3.1 Control of Related Risks
Different risk control measures should be taken for different risk levels, mainly preventive control and emergency control. Different risk control measures should be taken for specific hazards of the airport power supply system. For equipment-related risks, the Phase I power supply system of the airport is used to supply the T1 terminal load, and as the passenger volume increases year by year, the T1 terminal is facing the possibility of being put into operation again, but the Phase I power supply system lacks zero-sequence protection, and the zero-sequence protection of each level of the airport power supply system needs to be redesigned and upgraded. The equipment is aging, and regular comprehensive inspections and timely replacement of parts are needed to prevent emergency damage. Emergency measures are needed to diagnose faults in a timely manner, and accurate and timely information transmission is needed. For personnel management, strict continuing training in business knowledge is needed, and assessment work should be done well. A centralized training program should be organized for new equipment, with professional technicians giving lectures. Operators should be strictly required to operate according to the established norms. For the external environment, regular inspections should be conducted, and the roof of the substation should be reinforced. Regular anti-lightning inspections should be conducted, and the power supply should be restored according to the emergency plan.
3.2 Analyze the causes of risk
The specific analysis of the hazard sources brought about by the unstable airport power supply system by equipment, personnel, and external environment is as follows. For equipment, the consequence of the lack of zero-sequence protection in the first phase of the airport power supply system is that the faulted cable loop cannot be precisely cut off, and the airport experiences over-level protection tripping, with the scope of the fault expanding. The main reason is that the grounding system of the first phase power supply is a neutral point ungrounded mode, so there is no zero-sequence protection design in the power supply system. Moreover, the aging equipment in the first phase of power supply is prone to faults during operation, leading to local power outages. The main reason is that the equipment has been in service for a long time, and some parts have aged. In terms of personnel management, operators did not strictly follow the established norms in operation, and the lack of adherence to the norms resulted in serious equipment damage, especially in emergency situations when personnel exhibited panicked emotions, lacked sufficient safety awareness, and were unfamiliar with operating procedures, leading to frequent equipment failures. The influence of external environment, natural disasters can cause the power supply system protection to trip, lightning can damage the power supply equipment. The two power supply routes of the incoming power substation simultaneously lost power.
3.3 Application of static reactive power compensator
The simulation of the static reactive power compensator's simulation process time was set to 0.25s, and a three-phase bridge-type silicon diode was used for rectification, with a resistance value of 90Ω and a capacitance value of 1000μF. The circuit breaker-connected branch was disconnected from the remaining load. The waveform distortion was caused by the typical rectification circuit in the grid, and the positive and negative half-waves formed two waveheads, with a peak current amplitude of about 75A. Based on the harmonic components and reactive power in the grid, the static reactive power compensator can effectively generate the desired waveform. The three-phase compensation current phase difference exists in the static reactive power compensator, but its waveform is roughly the same, and the current amplitude is about 23A. Using static reactive power compensation to adjust the current, the three-phase current is adjusted for 10ms to effectively restore its stable sinusoidal state, with an amplitude of 8A being the maximum value for the three-phase current. The fundamental wave current is effectively concentrated at this location, where the harmonic content can be ignored, and the power factor is approximately 0.968, effectively verifying the static response capability of the system's reactive power compensation. Conclusion.
In summary, the safety and reliability of the airport power supply system directly affect the operation of the airport, so it is necessary to evaluate the current status of the airport power supply system and conduct risk assessment based on the current status, and take targeted countermeasures to ensure the stability of the airport power supply system. The function and control method of the compensation current generation module were analyzed, and the static and dynamic responses of the reactive load were analyzed. The simulation results show that the system can achieve reactive power compensation and harmonic suppression, the power factor is improved to 0.98, the compensation accuracy is good, the current waveform is approximately sinusoidal and the phase angle is almost consistent with the voltage phase, no overcompensation or undercompensation occurred, and the satisfactory reactive power compensation and harmonic suppression effect was achieved.