Research on power quality in the hottest distribut

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Research on power quality problems in distributed generation

Abstract: due to the gradual depletion of traditional energy and people's attention to environmental protection, the power system will face great reform. Distributed generation is the development direction of the future power system, and power quality problems can not be avoided by any way of power generation. This paper analyzes the possible power quality problems in distributed generation system, points out its existing problems and explores its potential, and finally puts forward some feasible research directions

key words: distributed generation power quality formulation power technology reactive power compensation since the 1980s, a large number of computer-based control equipment and power electronic devices have been put into use, making the performance of power quality very sensitive; The appearance of adjustable speed motor, reactive power compensation device and new load leads to the continuous rise of system harmonic level, which puts forward higher requirements for power quality; The growing awareness of power quality among power users forces power companies to improve power supply quality. Under the traditional power system system, countries all over the world have conducted in-depth research on power quality problems and adopted corresponding solutions. At present, 90% of the world's power supply systems are single power supply systems characterized by large units, large electricity and high voltage. However, due to the gradual depletion of traditional energy resources, the improvement of power quality requirements in many departments of today's society, and the increasing attention paid by countries all over the world to environmental protection issues, distributed power generation, an environmentally friendly, efficient and flexible power generation method, has been paid attention to by countries all over the world, It has become the most important research direction of power system in the 21st century. The introduction of distributed generation will have a great impact on the existing power system. Many countries in Europe and the United States have carried out scientific research on this new type of power generation. The research of distributed generation in China lags behind some developed countries in Europe and the United States, but in recent years, China has also carried out some basic research on distributed generation, This paper analyzes the impact of the development of distributed generation with a practical area of 5000 square meters on power quality and system stability, and then puts forward its own views on related issues. Distributed generation brings potential problems to power quality. Distributed generation is based on power electronic technology. A large number of power electronic converters will be applied to the power system. These devices will bear the important functions of energy transmission and load switching. With the wide application and development of power electronics technology, a large number of nonlinear loads have been added to the power supply system, especially the static converter working in the switching mode. Its operation will cause the distortion of electric current and voltage waveforms, causing electric harmonic pollution. At present, common power quality problems include: frequency offset, long-term voltage offset, short-term voltage offset, electromagnetic transient, three-phase imbalance, waveform distortion, voltage fluctuation and flicker, among which the harmonic problem in the middle of waveform distortion has been gradually paid attention to in recent years. Distributed generation (DG) has two main impacts on power quality. First, it will affect the voltage flicker. Voltage flicker is the visual perception caused by the instability of light illumination. The main reason for voltage flicker caused by traditional electricity is the instantaneous change of load. With the introduction of distributed generation, it will bring other factors that cause voltage flicker. These factors are mainly the following aspects: the start-up of a large distributed unit, the short-term upheaval of the output of the distributed unit, and the adverse effects of the interaction between the distributed unit and the voltage feedback control equipment in the system. As we all know, there are a large number of nonlinear components in the power system, which introduces a large number of harmonics. The harm caused by the introduction of harmonics to the power system includes: the occurrence of harmonics increases the power loss of power stations and user equipment; Sometimes harmonics will cause sensitive loads or control equipment, so the process level is poor; If the proportion of harmonic components in the waveform is too large, the service life of some power equipment will be reduced, such as transformers, generators, capacitors, etc. Because power electronic devices are widely used in distributed generation, it will inevitably bring a lot of harmonics to the system. As for the amplitude and order of harmonics, it is affected by the mode of power generation and the working mode of the converter. 2 distributed generation has potential advantages in improving power quality. Although the introduction of distributed generation brings many uncertainties to the system, causing voltage flicker and introducing a large number of harmonics, which further worsens some aspects of power quality, distributed generation also has the potential to improve power quality. First of all, the distributed power supply can provide power in time and quickly. When the electrical load is large, the distributed power supply is put into use in the shortest possible time under the relevant control strategy, so that the system can reduce faults as little as possible, so as to improve the stability of the whole electrical system. Now many experts and scholars of power system have conducted extensive and in-depth research on the power quality of traditional electricity. At present, there are several devices to choose from in terms of restraining harmonics, reducing voltage fluctuations and flickers, and solving three-phase imbalance. 6. All parts of the experimental machine should be cleaned frequently. Passive filters, static var compensation devices (SVC) and other mature technologies have been developed. With the emergence of high-performance power electronic components (such as GTO, IGBT, LTT, etc.) and the development of micro processing and microelectronics technology, information technology and control technology, American power experts have proposed that when people choose tensile machines, they should choose AC transmission systems (also known as facts), At present, the main facts devices include static var compensator (STATCOM), thyristor controlled series switching capacitor (TSSC), controllable series compensation capacitor (TCSC), unified power flow controller (UPFC), etc. As an extension of facts technology in distribution system, DFACTS Technology (also known as custom power technology) has become a powerful tool to improve the power quality of traditional centralized power generation system. The core device of this technology is IGBT. At present, the main devices are: active filter, dynamic voltage recovery, static var compensator for distribution system, solid-state switch, etc. APF is an effective tool to compensate harmonics, and DVR is an effective device to suppress voltage sag. The above technologies to improve power quality are based on power electronic technology and communication control technology, and distributed generation is based on the development of power electronic technology, computer, communication technology and control technology. This new power system makes it possible to reuse its own power electronic converter, and use the existing power electronic equipment to absorb or release active and reactive power, so as to not only realize the transmission and conversion of power, And change

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