Abstract:Design a new type of energy-saving intelligent integrated power capacitor, which adopts energy-saving zero crossing switching and intelligent network control structure to achieve energy-saving, intelligent, networked, integrated, and improved reliability functions. Through its application in the distribution network, it has achieved the effects of reducing power grid losses, saving energy and materials, miniaturization, and lowering maintenance costs.

Keywordsintegrate; capacitance; Zero crossing switching

Introduction

Resolving the issue of reactive power compensation in the distribution network is crucial for reducing network losses and saving energy. Appropriately increasing the power factor of users can not only fully utilize the production capacity of power supply equipment, reduce line losses, alleviate the pressure of higher-level power grid compensation, and improve voltage quality, but also improve the efficiency of users' electrical equipment, effectively reduce energy losses, and reduce users' electricity bills. Its social and economic benefits are both very significant. Therefore, the development and promotion of energy-saving intelligent power capacitors have a significant impact on China's power energy conservation.

Structural design of intelligent integrated power capacitors

Energy saving intelligent integrated power capacitors are a new generation of low-voltage reactive power compensation devices developed within the overall development framework of intelligent appliances. It consists of intelligent measurement and control module, thyristor composite switch module, line protection module, and power capacitor. The principle and structure of intelligent integrated power capacitors are shown in Figure 1. It can replace the complete set of automatic reactive power compensation devices composed of intelligent controllers, fuses, composite switches or mechanical contactors, thermal relays, low-voltage power capacitors, indicator lights and other components connected by wires inside and on the cabinet. The traditional reactive power compensation device has been changed from using mechanical contactors or electromechanical integrated switches as the switching mode of capacitors, and the bulky and cumbersome structural mode of traditional reactive power compensation devices has been changed. This has made the new low-voltage reactive power compensation equipment have the characteristics of good compensation effect, low power consumption, small size, cost savings, flexible use, easy maintenance, long service life, and high reliability, and adapt to the high requirements of modern power grids for reactive power compensation.

Design points of energy-saving intelligent integrated power capacitors

2.1 Intelligent fully automatic combination control mode, achieving zero crossing switching

The key points of the design of intelligent integrated power capacitors lie in the use of electronic real-time detection signal feedback, contactless photoelectric triggering technology, thyristor and magnetic holding relay composite switching technology, which realizes equal voltage switching, zero crossing switching (switching inrush current is almost zero), and eliminates harmonic injection. Its intelligent fully automatic combination control mode uses various parameters such as reactive power, power factor, and reactive voltage as control parameters to achieve optimal compensation combination. Due to the intelligent network module of each capacitor, it can form a master and slave automatic combination mode for switching, which is equivalent to each capacitor acting as a controller, achieving high reliability. Hybrid compensation is a mode that optimizes the compensation effect, and intelligent integrated power capacitors can easily and reliably achieve complex and optimal compensation requirements such as phase separation compensation and hybrid compensation. Due to the excellent "zero crossing switching" function of intelligent integrated power capacitors in China, there is no surge impact, no operating overvoltage, and no arc reignition during the capacitor switching process, which improves the speed of control and extends the service life of capacitors. The traditional reactive power compensation device uses AC contactors for switching. When AC contactors disconnect capacitors, they generate high operating overvoltage, which is an important factor causing capacitor damage. After adopting zero crossing switching technology, the service life of capacitors has been extended by more than 2-3 times. The economic and social benefits brought by this are incalculable. The impact of zero crossing switching and non zero crossing switching on the lifespan of capacitors can be clearly compared through Figures 2 and 3.

2.2 The intelligent network adopts a decentralized control mode, which reduces the lifecycle cost exponentially

Intelligent integrated power capacitors eliminate the main controller and adopt a decentralized control mode, with each group of intelligent integrated power capacitors having a control unit. The automatic switching of multiple sets of capacitors eliminates the reliance on a single controller and prevents the entire system from collapsing due to controller failures. In addition, when multiple intelligent integrated power capacitors are connected to the network, a network will be automatically generated, where the one with the smaller address code is the master and the rest are the slaves, forming a low-voltage reactive power automatic control system. If individual slave machines fail, they will automatically exit without affecting other work; If the host fails, it must also exit and create a new host from the remaining slave machines to form a new system. Capacitors with the same capacity are switched according to the cyclic switching principle, while capacitors with different capacities are switched according to the adaptive compensation principle. And it has a 485 communication interface, which can be connected to the backend computer for comprehensive power distribution management. In short, the product adopts intelligent network technology, greatly improving operational reliability and sufficient investment of capacitors, and extending the life of compensation devices. Using reactive power compensation devices with the same capacity, although the price of intelligent integrated power capacitors is similar or higher than traditional capacitors with the same capacity, the cost of intelligent integrated capacitors is significantly reduced compared to the overall reactive power compensation device and the entire life cycle.

2.3 Modular design, easy expansion, and simple maintenance

Intelligent integrated power capacitors have achieved standardization and modularization, replacing traditional controllers, air switches, AC contactors, thermal relays, and capacitors. They are integrated into a whole and installed in a modular manner using building blocks. Multiple capacitor group screens are installed, reducing production hours by more than 60% compared to traditional modes, while reducing 80% of connecting lines and nodes. The cabinet is simple and can be quickly assembled on site. The product has a small size and simple wiring. As the power load of the electricity user increases, the number of capacitors can be increased at any time, which changes the limitations of the conventional mode due to complex wiring and rigidity. It meets the needs of enterprise development and can be invested in stages. The product is highly intelligent, user-friendly, easy to install, and easy to maintain. If the fault indicator light on the product panel is found to be on, simply remove the capacitor and replace it with a new one, which is as convenient as replacing the battery. No professional electrician is needed for timely maintenance, greatly improving the compensation effect, and the maintenance cost is only about 10% of other compensation devices. According to statistics, the labor cost for maintaining the compensation device is 5 yuan/kvar. If it is replaced with a smart integrated power container, the country can save 161.5 billion yuan annually.

Energy saving effect analysis of 3 intelligent integrated power capacitors

Conventional compensation devices require AC contactors to connect the compensation circuit, and the AC contactor contacts need to be maintained by electromagnetic coils. Each AC contactor (calculated based on the holding capacity of CJ19 relay) consumes 15W, and generally each circuit can connect 13kvar, which is equivalent to nearly 1kvar capacitor compensation consuming more than 1W of electrical energy on the switch. The intelligent integrated power capacitor adopts a magnetic holding relay, in which the armature is held by a permanent magnet. After the circuit is connected, it no longer consumes electrical energy. Therefore, after adopting intelligent integrated power capacitors, the losses per kVar after capacitor connection are reduced by more than 10000 compared to traditional reactive power compensation devices. In addition, the volume of intelligent integrated power capacitors is reduced by about 50% compared to other automatic compensation devices, thus reducing a large amount of electrical energy losses such as wires, contacts, and components, which can reduce such losses by about 50%.

At present, there are nearly 5 million distribution transformers in use in China (data from the China National Electric Power Regulatory Commission), with an average capacity of 200kVA and a total capacity of nearly 1 billion kVA. Reactive power compensation is calculated based on one-third of the average distribution transformer, and the existing distribution transformers require a reactive power compensation capacity of 330 million kVar. If the existing traditional reactive power compensation device for distribution transformers is replaced with intelligent integrated power capacitors, and calculated based on 1kvar saving 1W (excluding reducing wire and contact losses), it can save 2.891 billion kWh of electricity per year, exceeding the designed annual power generation of Qinshan Nuclear Power Plant by 1.7 billion kWh; It can reduce coal consumption by 1.0986 million tons and gas CO2 emissions by 2.8564 million tons, which is equivalent to increasing the forest area for air purification by 7616.94 square kilometers; It can reduce gas SO2 emissions by 5.17 million tons and gas NO2 emissions by 33600 tons, greatly saving coal resources and reducing environmental pollution. Recently, the national electricity load has increased by more than 10% annually, and the annual capacity of distribution transformers has grown by 100 million kVA, which is equivalent to adding about 370000 315kVA transformers every year. Low voltage power capacitors add 33.33 million kVar annually, which can save nearly 300 million kWh of electricity.

4. Introduction to Ankerui Intelligent Power Capacitor Products

The AZC/AZCL series intelligent capacitors automatically find the optimal input (cut-off) point through an internal thyristor composite switch circuit, achieving arc free switching; Ensure zero crossing switching, no inrush current, no sintering of contacts, minimal energy consumption, and no harmonics; At the same time, it has anti-interference, lightning protection, power phase loss, and no-load tripping protection functions, especially suitable for switching capacitors during reactive power compensation, without the need to install a heat sink.

This series of intelligent capacitors adopts an LCD display, which can display real-time electrical parameters such as three-phase bus voltage, three-phase bus current, three-phase power factor, frequency, number of capacitor circuits and switching status, active power, reactive power, total harmonic voltage distortion rate, capacitor temperature, etc.

(1) The AZC series intelligent capacitors use thyristor composite switches for switching, with optimal switching points to achieve arc free switching; Complete protection functions integrated into one module, easy to install.

AZC series intelligent capacitor selection:

(2) AZCL is a series connection of appropriate reactance rates based on AZC (7% suitable for harmonic environments above 5th/7th order, 14% suitable for harmonic environments above 3rd/5th/7th order), which can effectively solve harmonics, avoid resonant amplification of harmonics, and protect the life of the capacitor cabinet itself.

AZCL series intelligent capacitor selection:

5 Conclusion

Intelligent integrated power capacitors achieve zero crossing switching, adopt fully automatic combination control mode, improve reliability, achieve energy-saving effect of saving 1W per kVar compared to traditional compensation devices, and have advantages such as miniaturization, performance *, and low cost. They are ideal equipment for reactive power compensation.