1. Introduction In China's current stage of development, the demand for and consumption of energy are both large, especially of electricity. Therefore, effective conservation is of paramount importance. With economic development, the proportion of rectifier and frequency converter equipment in the significantly increased electricity load of various industries and residential use has increased. Reactive load currents and harmonic currents not only increase power supply system losses, but harmonic currents may also cause communication and computer system failures. A technical solution to these problems is to install compensation capacitors, thereby reducing system losses and improving power quality. Therefore, solving the reactive power compensation problem of the power grid is extremely important for reducing network losses and saving energy. 2. Principles of Reactive Power Compensation Reactive power compensation, as its concept, is well-known. It involves using reactive power compensation equipment to provide necessary reactive power to improve the system's power factor, reduce energy consumption, and improve the voltage quality of the power grid. From the basic situation of reactive power consumption in the power grid, it can be seen that all levels of the network and transmission and distribution equipment consume a certain amount of reactive power, especially the low-voltage distribution network. In order to minimize the transmission loss of reactive power and improve the efficiency of power transmission and distribution equipment, the configuration of reactive power compensation equipment should be reasonably arranged according to the principle of "graded compensation and local balance". The principles are as follows: 1) Combine overall balance with local balance, with local balance as the main focus. 2) Combine power sector compensation with user compensation. 3) Combine decentralized compensation with centralized compensation, with decentralized compensation as the main focus. 4) Combine loss reduction with voltage regulation, with loss reduction as the main focus. 3. The significance of improving the power factor The power factor reflects the degree to which the apparent power output of the power source is effectively utilized. We hope that the power factor is as high as possible. In this way, the reactive power in the circuit can be minimized, and most of the apparent power will be used to supply the active power, thereby improving the power transmission capacity. The significance of improving the power factor is as follows. (1) Improve the utilization rate of equipment Under a certain voltage and current, the higher the power factor, the greater the active power output of the equipment. Therefore, improving the power factor is an effective way to fully utilize the potential of the equipment and improve its utilization rate. (2) Reduce active power loss of the line. Due to the increase in cosφ, the voltage U2 after compensation is slightly larger than the voltage U1 before compensation. It can be approximated that U2 ≈ U1. Thus, the percentage reduction of line loss P is derived. When the power factor increases from 0.70 to 0.85 to 0.95, the active power loss will be reduced by 20% to 45%. (3) Reduce voltage loss (4) Improve the transmission capacity of the power grid 4. Main factors affecting power factor 1) A large number of inductive devices, such as asynchronous motors, induction furnaces, AC welding machines, etc., are the main consumers of reactive power. 2) The reactive power consumed by transformers is generally about 10% to 15% of their rated capacity. Their no-load reactive power is about 1/3 of that at full load. Therefore, in order to improve the power factor of the power system and enterprises, transformers should not be operated under no-load or in a low-load state for a long time. 3) Supply voltage exceeding the specified range will also significantly affect the power factor. When the supply voltage is 10% higher than the rated value, reactive power will increase rapidly due to magnetic circuit saturation. When the supply voltage is lower than the rated value, reactive power will decrease accordingly, thus improving the power factor. However, a decrease in supply voltage will affect the normal operation of electrical equipment. 5. Classification of Reactive Power Compensation Automatic reactive power compensation is classified into three-phase capacitor automatic compensation and single-phase capacitor automatic compensation according to its nature. 1) Three-phase capacitor automatic compensation is suitable for power distribution systems with balanced three-phase loads. Because the three-phase circuits are balanced and the reactive current in the circuits is the same, the signal for adjusting the reactive power parameter is taken from any one of the three phases during compensation. Based on the detection results, simultaneous switching of the three phases can ensure the quality of the three-phase voltage. 2) In civil buildings, the extensive use of single-phase loads can easily cause serious imbalances in the three-phase loads, especially in residential buildings where the three-phase imbalance is more severe during operation. In this situation, traditional three-phase reactive power compensation methods not only fail to save energy but also waste resources. They are also ineffective at compensating for reactive power in the system, and the resulting over- and under-compensation issues pose serious threats to the normal operation of the entire power grid. For three-phase unbalanced and single-phase distribution systems, phase-separated capacitor automatic compensation should be used. Its principle is that the signal for adjusting reactive power parameters is taken from each of the three phases, and compensation is performed accordingly based on the magnitude of the inductive load and the power factor of each phase, without affecting other phases. The above has introduced the main factors affecting the power factor and the significance of improving the power factor, and discussed the compensation principles and classifications of reactive power compensation, giving readers some understanding of reactive power compensation. The following section focuses on a new type of reactive power compensation device: the SVS type reactive power compensation device, and compares it with ordinary reactive power compensation devices. 6. Comparison between ordinary reactive power compensation devices and new reactive power compensation devices (SVS) (1) Switching devices Ordinary reactive power compensation devices connect the contactor through intermediate relays (or same-state relays) to control the input or output of compensation capacitors. The switching of capacitors cannot be guaranteed at zero potential instant, which can easily cause large surge currents or voltages, and thus cause electrical damage, becoming the main cause of power supply failures. The new reactive power compensation device uses imported chip thyristors, and the capacitors are switched at zero potential instant, without peak pulse current interference to the power grid, ensuring safe power supply of the system. This is very important in situations with sensitive electronic equipment. (2) Filtering circuit The new reactive power compensation device has an RC absorption circuit, which can filter out high-order harmonics, achieve no switching oscillation, and no compensation dead zone. This product is suitable for reactive power compensation in three-phase power grids with severe harmonic pollution. (3) Compensation method Ordinary reactive power compensation devices can only perform three-phase equal compensation in places with obvious three-phase unbalanced loads or single-phase loads. The new reactive power compensation device can automatically input equal or unequal capacitors according to actual needs to achieve three-phase symmetrical or asymmetrical compensation functions. (4) Response Time The response time of ordinary reactive power compensation devices is very slow. It takes 10-30 seconds to connect one group and several minutes to complete all compensation. For a 50Hz power grid, the new reactive power compensation device uses the Fast Fourier Transform algorithm in each cycle, and the automatic response time is less than 20ms. (5) Switching Time Ordinary reactive power compensation devices require a long time between switching on or off, thus affecting the characteristics of the compensation system. When the load changes and more than one group needs to be switched, the new reactive power compensation device can simultaneously and accurately control the corresponding number of groups. (6) Compensation Accuracy Ordinary reactive power compensation devices are configured with ten capacitors, which has low accuracy and slow tracking, resulting in inaccurate compensation such as leading or lagging. The new reactive power compensation device, with each capacitor increasing in equal capacity by multiples of 2n-1 (1≤n≤4), can realize instantaneous random combination switching and can simultaneously compensate for three-phase asymmetry, with an average power factor of 0.9-0.99. (7) Operational Performance The controller of the contactor switching system of ordinary reactive power compensation devices usually requires a DIP switch. The small display makes it very difficult to check the system characteristics. There is no additional remote control and communication, and the protection function is backward. The new reactive power compensation device adopts an advanced microcomputer controller, and the detection and tracking of switching are completed automatically without manual intervention. It uses a large LCD display screen, which provides very convenient operation. It can realize remote group control and reporting of system and power grid status. It has strict anti-interference capabilities and has protection functions against line faults such as overvoltage, phase loss, undervoltage and output short circuit. (8) Maintenance Performance The contactor of ordinary reactive power compensation device has a limited lifespan and needs to be replaced frequently. The surge caused by the contactor switching can lead to frequent equipment failures and additional replacements. The capacitors that are put into operation always start from zero potential, which has a considerable impact on the power grid and the capacitors themselves. The new reactive power compensation device can absorb the spike pulses in the circuit through a special absorption circuit and charge the capacitors to be put into operation in advance through a special charging circuit to maintain a certain DC level, thereby reducing the impact on the power grid, better protecting the switch module and capacitors, and having a long service life, thus greatly reducing on-site maintenance costs. (9) Economic performance The initial cost of ordinary reactive power compensation devices often changes due to the replacement and maintenance of the equipment. After a period of time, the actual cost and indirect losses of the contactor switch switching system will be greater than the initial investment. The initial investment of the new reactive power compensation device is higher than that of the contactor system, but when considering the cost of operation and maintenance, the overall investment is lower than that of the contactor switch switching system. At the same time, because the compensation factor is higher, the power supply department may also have a certain reward. From the above comparison, it can be seen that the technical performance of the new low-voltage reactive power dynamic compensation device is superior to that of the traditional compensation device. It also has a long service life, low maintenance workload, and good long-term energy saving effect. The article is from "Energy Saving Innovation 2006 - Proceedings of the First National Electrical Energy Saving Competition".