1 Introduction In order to improve the level of medical services, modern medical institutions are constantly introducing new and complex advanced medical equipment such as nuclear magnetic resonance, CT, X-ray, and hemodialysis machines, as well as various energy-saving lighting equipment, inverter air conditioners, and elevator equipment. Wait a lot for use. These devices are non-linear devices that generate a large number of higher harmonics during operation, causing some interference to the power distribution system and medical equipment. At the same time, these advanced medical equipments have high-end computer components and a large number of highly sensitive microelectronic devices. The power quality of the power supply is very high, and it is very sensitive to voltage fluctuations and power harmonics. Serious power harmonic problems will lead to medical treatment. Damage to the equipment can even lead to medical malpractice.
2 Harmonic source, harmonic characteristics and harmonic hazard analysis of hospital building power supply system
2.1 Source of harmonics
2.2 Characteristics of harmonics
2.3 Harmonic hazard analysis 2.3.1 Harmonic damage to the distribution system makes the additional loss of power components increase, which is easy to cause fire; affects the normal operation of electrical equipment; causes grid resonance; makes relay protection malfunction, electrical measurement error Big; make the industrial control system crash.
2.3.2 Harmonics damage to medical equipment leads to synchronization misalignment and data errors of devices that rely on microprocessor technology; directly endangers the internal electronic circuit safety of the device, resulting in breakdown or discharge; affecting the performance and accuracy of precision medical equipment.
3 Grid harmonic national standards require the current power quality (harmonic) assessment standard, mainly for the Chinese national standard "Power Quality: Utility Grid Harmonics" (GB/T14549-1993), the distortion of current and voltage in the grid The rate is clearly defined and is also an important basis for harmonic evaluation and governance.
Table 1: National Standards for Harmonic Voltage of Power Grid: Cited in (GB/T14549-1993)
Table 2: Allowable values ​​of harmonic currents injected into the common connection point of the grid: cited in (GB/T14549-1993)
Application of 4ANAPF low-voltage active filter in hospital buildings 4.1 Active filter application introduction A new outpatient hospital comprehensive building in a large-scale top three hospital has four sets of 2000kVA and one 1600kVA transformer and one 800kW diesel generator, according to The load rate of the nonlinear load equipment of the transformer and the corresponding harmonic distortion rate and the simultaneous use rate of each nonlinear device calculate the harmonic current, and five ANAPF active filters of different capacity specifications are configured.
The following is a detailed description of the comparison of the power quality test of the power distribution system before and after the 1#ANAPF active filter is put into operation. The 1# transformer load is mainly lighting, elevator, submersible sewage pump, computer center and so on.
4.1.1 Data before and after the active filter is put into operation (1) The current waveform distortion before the active filter input is serious. The three-phase current harmonic content is 19.7%, 27.8%, 26.6%, respectively, and the three-phase current is 45A. 40A, 64A, neutral current is 37A.
(2) The distortion of the current waveform after the active filter is input is obviously improved, and the harmonic content of the three-phase current is significantly reduced, which are 2.9%, 2.8%, and 3.4%, respectively. The three-phase currents are 47A, 48A, and 47A, respectively. The current is 5A.
(3) The current waveform is obviously improved. After using the filter, the current waveform is approximately sinusoidal, and the harmonic control work achieves the expected goal and effect.
4.1.2 Test data before and after the active filter is put into operation
Waveform before harmonic control waveform after harmonic control 
Measurement data before harmonic control Measurement data after harmonic control
4.2 The significance of the application of active filter in hospital buildings protects the safety of medical electrical equipment, purifies the power supply, protects the power factor compensation equipment, prevents the malfunction of the protection device, reduces the power loss, and expands the power supply capacity of the transformer and the generator.
4.3 Main technical indicators of active filters
4.4 Active filter quotation and component list
5 Conclusions This paper analyzes the harmonic source, harmonic characteristics and hazards of hospital buildings, and compares and analyzes the situation before and after the active filter input through the application cases of active filters in a large hospital low-voltage power distribution system. The harmonic control technology of active filter is one of the effective means to improve the quality of power supply. It can control the generated harmonics to a minimum, achieve scientific and rational use of electricity, suppress grid pollution, improve power quality, and ensure medical equipment safety. The role.
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