Contact Person : Dina Huang
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January 10, 2024
Abstract: With the widespread use of electronic devices, non-linear loads are increasing, which results in that the harmonic pollution in enterprise power grids is becoming more and more serious. Due to the adverse effects of harmonics, the quality of electricity is deteriorating, the additional losses increasing, the reliability of the power grid reducing, so that the normal operation of enterprise power supply and consumption equipment is affected, and even equipment is damaged to cause electrical faults. Based on the requirements and current situations of electricity safety, this paper analyzes the functions and effects of active filter devices in biopharmaceutical safety power supply systems.
Keywords: harmonic, power quality, active filter
Nowadays, a variety of power electronic devices are widely applied in the pharmaceutical enterprises, where rectifier devices accounted for a large proportion. Direct-current power supply required by the inverter and DC chopper, etc., is mainly from the rectifier circuit. The thyristor phase-controlled rectifier circuit or the diode rectifier circuit is the serious harmonic source. Although the single capacity of electrical equipment is small, the number is massive, most of which contains switching power supplies. Various types of switching power supplies and frequency converters are used more and more, together with the harmonics generated by fluorescent lamps, so that the harmonic pollution of the power supply is becoming more and more prominent. Grid harmonics make the voltage, current waveform distort, so that many abnormal phenomena and faults happens in the company’s power system and electrical equipment. Effective prevention to harmonics has become an important part of the safe operation of the enterprise power system. The active filter collects the harmonic current through CT, quickly calculating and extracting the content of each harmonic by CPU, and sends out instructions to make the power device to produce the compensation current of equal amplitude and opposite direction to the harmonic current, and injects it into the power grid so as to offset the harmonic current in the system.
2. Key features of power quality in biopharmaceutical industry
2.2 The main loads are pumps and motors driven by frequency converters. The main harmonic source is the frequency converter with a large content of harmonics, which requires a separate configuration of APF for harmonic management.
3. Harmonic sources in biopharmaceutical power supply and distribution system
With the rapid development of the pharmaceutical industry, many advanced equipment came into being required by the pharmaceutical industry. There exist a large number of loads of pumps and motors, and many are equipped with frequency converters. The large number of applications of frequency converters make the harmonic content of the power distribution system greatly increase.
At present, most of the frequency converters use 6 pulse rectification to convert AC current in to DC current, so the harmonics are mainly the 5th, 7th and 11th. At the same time, there are usually laboratories and automatic production lines in pharmaceutical enterprises with a large amount of precision devices, which in many cases are both generators and victims of harmonics. Harmonics will affect the normal work of the equipment in the laboratory, making the ongoing experiments lost; harmonics will also affect the intelligent controllers and PLC systems in automated production lines to make the automatic control equipment failure. Therefore, the harmonic problems of pharmaceutical enterprises has far-reaching impact and serious harm, which urgently need to be managed.
3.1 Research stations and laboratories
In laboratories, a large number of sensitive equipment needs a clean grid environment to ensure the normal operation of the system, such as high-tech instruments, precision instruments and measuring equipment, switching power supplies, rectifier inverters, UPS / EPS, etc., which are also larger harmonic sources. Laboratories and other places where there are a large number of switching power supply loads will produce significant 3rd, 5th and 7th harmonics, where we should pay special attention to the affect of 3rd harmonic current on the neutral line.
3.2 Automatic production lines
Fermentation is an important part of the production of API, which is made by the fermenter. With the continuous expansion of product output, updating of new processes and increasing of new varieties, there are different requirements of the control of the fermenter, stirring frequency and time period adjustments. For the situations with heavy loads, large power consumption, long fermentation cycle, in recent years the fermentation production enterprises have also taken a variety of methods to carry out equipment renovation. Frequency control can both meet the requirements of the production process and reduce consumption. However, with the continuous improvement of the automation, power pollution by automation equipment is also getting worse and worse. The corresponding interference with the automatic control system is also getting stronger and stronger. The requirements on the power supply filtering and purification to obtain a relatively stable and green power supply are also getting higher and higher.
4. Practical case
Take a biopharmaceutical power quality management project in Shandong Province as an example, according to the feedback from the person in charge of the plant, frequent tripping phenomenon occurs in the comprehensive office building of the plant, and the reactor in the capacitor cabinet of the production workshop appears to be burnt and the N-wire cable is overheated. The main reason is expected to be the fact that there are many loads of inverter air-conditioning, computer and communication equipment, LED lighting, pumps and others in the comprehensive office building and the production workshop, which will generate harmonics and affect the entire power supply and distribution system. Now it’s necessary to measure the distribution rooms of the comprehensive office building and production workshop, and to give the appropriate solution according to the corresponding power quality data.
4.1 Harmonic measurement data in the distribution room of the comprehensive office building
4.2 Harmonic measurement data in the distribution room of the production workshop
From the above two sets of measurement data, it can be concluded that the harmonics of the comprehensive office building are mainly 5th and 7th and the current distortion rate is up to 22%. The 5th and 7th harmonics can be centrally managed in the distribution room to eliminate the harmonic impact on the entire power supply and distribution system, transformers, capacitor cabinets, and other electricity equipment, so as to ensure the normal production of biopharmaceuticals. The harmonics of the production workshop distribution room are more serious, where the 3rd and 5th harmonics have exceeded the national GB/T14549-1993 "harmonics in public supply network" 0.38KV system harmonic current value standard. On-site capacitor cabinets are connected in series with 7% reactance. The 3rd and 5th harmonics flow into the capacitor cabinet, and the harmonic current is superimposed on the fundamental current of the capacitor, which makes the capacitor's operation current become larger and the temperature rises, leading to overheating and reduces the service life of the capacitor or causes the capacitor to be damaged.
The active filter devices can be used to solve these problems, which adopt DSP+FPGA all-digital control method and are connected in parallel in the system. They can fully compensate for the 2nd to 51st harmonics or compensate for specific harmonics, eliminate harmonics in the system to prevent damages to the N line, and protect the circuits against the fire.
With the introduction and deepening of modern production processes, power equipment and other advanced scientific means, a large number of nonlinear power electronic equipment emerges, which improves the quality of biopharmaceuticals, but also brings a severe impact on the power quality of the power supply and distribution system of the entire plant at the same time, especially the scientific research laboratories, where the loads are diverse and the harmonic generation and changes have a great randomness and complexity. By studying the power quality of the supply and distribution system in biopharmaceutical buildings and proposing a reasonable solution in conjunction with the system platform, the quality of power supply in biopharmaceuticals can be improved as well as the safe and economic operation of the grid and the energy consumption can be reduced.
 Acrel Enterprise Microgrid Design and Application Manual. Version 2022.05