Design principles and functions of EPS emergency power supply

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Design principles and functions of EPS emergency power supply [Copy link]

Design principles and functions of EPS emergency power supply

In recent years, the domestic power grid has developed rapidly, and its risk resistance has been continuously enhanced. However, there is still a big gap compared with the requirements of rapid social and economic development and rapid growth in electricity consumption. For example, the construction of the power grid has lagged behind for a long time, and it is still in the early stage of national networking; the electromagnetic ring network problem affects the full use of the transmission capacity, the reactive power compensation capacity of the power grid is insufficient, and the hierarchical and regional balance has not been achieved; the safe operation of the power grid is threatened by external damage, and there are safety hazards in the secondary system. In addition, the quality of some equipment is not high, which also affects the safe operation of the power grid to a certain extent. Under this situation, it is not impossible for regional blackouts caused by power grid accidents in the United States, Canada and Russia to occur in my country. Once such a blackout occurs, the consequences will be very serious.

The lessons learned from power grid safety accidents at home and abroad tell us that power grid power planning must be scientific and reasonable, power grid structure construction must be rigorous and standardized, and we must increase the application of advanced technologies, strengthen power system management, and improve load forecasting and regulation. In addition, relevant experts have also put forward some opinions and suggestions that are worth referring to or adopting:

First, large cities should have two or more power plants with "black start" capabilities, or consider having a certain number of single-cycle gas turbine generator sets with fast "black start" capabilities as backup. These sets can be used for peak load regulation or as emergency backup power sources.

The second is to strengthen the construction of distributed power supply systems, especially distributed power supply systems with trigeneration functions.

The third is to introduce the "User Safety Level System" as soon as possible, use it as the basis for power outage procedures and plans, and establish a market-oriented mechanism for effectively allocating electricity resources.

Fourth, establish social system engineering to improve the government’s ability to respond to power grid emergencies.

Fifth, establish an electricity hearing system to speed up the operation of the electricity management system and electricity regulatory system.

Next, we need to understand the EPS emergency power supply system.

EPS emergency power supply can be said to be an emerging industry that has developed rapidly in the past two years. Compared with the mature UPS, the similarities are that both have the function of continuing to provide AC power to the load in the event of a mains failure, and both use IGBT inverter technology and pulse width modulation (PWM) technology. The difference is that in addition to providing uninterrupted power supply, UPS also has the function of improving the quality of the mains, while EPS emergency power supply mainly solves the problem of emergency power supply in the event of a mains failure; UPS mainly provides power supply for IT industry equipment, while EPS emergency power supply is suitable for various industries; UPS is mainly aimed at maintaining smooth information transmission, while EPS emergency power supply is mainly aimed at preventing major disasters and accidents.

There are many brands of EPS emergency power supplies on the market. They can be divided into the following three types according to the type of load: one is the single-phase EPS mainly used for emergency lighting and accident lighting; the second is the three-phase series EPS that can be used for inductive loads such as air conditioners, elevators, rolling doors, exhaust fans, water pumps, etc.; the third is the variable frequency series EPS that directly powers the motor.

The main design concept of EPS emergency power supply is to provide safe and reliable emergency power supply when the city power is suddenly interrupted, and to effectively avoid personal injury and property loss when disasters occur. Therefore, when designing EPS, its safety, reliability, applicability and rationality should be considered. Including: the power-off conversion time is generally in milliseconds (25ms) to ensure the timeliness of power supply; strong load adaptability, including capacitive, inductive, and mixed loads, and strong overload capacity and impact resistance; with multiple outputs to prevent failures caused by single output; with fire linkage and remote control capabilities, and can be converted between manual and automatic; in addition, it is required to have strong environmental adaptability, be applicable to various harsh environments, have measures to prevent high and low temperatures, humidity, heat, smoke, dust, vibration and rat bites, and have complete alarm functions to provide timely alarms for various abnormal conditions.

EPS for emergency lighting and accident lighting are generally single-phase, mainly providing centralized power supply for emergency lighting occasions (shopping malls, entertainment venues, exchanges, etc.). When the input power is normal, one way of the mains power is output to daily lighting through the conversion device, and the other way is used to charge the battery pack through the charger. When the controller detects that the mains power is interrupted or abnormal, it sends a start signal to the inverter and controls the conversion device to switch to the inverter output.

Emergency lighting and mixed load EPS are generally suitable for occasions with complex load properties, such as both lighting loads and power loads, so three-phase is generally the most common. Applicable occasions include hotels, high-rise buildings, hospitals, large shopping malls, etc.

The motor-specific variable frequency starting EPS is mainly designed for motor loads to avoid damage to the equipment due to high current shock during motor starting. It can be used for high-power motor loads, such as elevators, fire pumps, large fans, etc. The difference from other EPS is that this type of EPS generally has only a single output. When the three-phase input mains power is normal, it provides DC power to the inverter after rectification, and charges the battery pack through the charger at the same time; when the three-phase input power is off or abnormal, it automatically switches to the battery pack to provide DC power to the inverter. When the motor load needs to work, the start signal (operation signal or remote control signal, etc.) is transmitted to the inverter, and the inverter will output immediately. The frequency is changed from 0 to 50Hz to provide variable frequency starting for the motor, and it maintains normal operation when its frequency reaches 50Hz.

With the continuous development of science and technology, many intelligent buildings have sprung up, and people have put forward higher requirements for living environment, including power supply and fire safety issues. However, EPS started later than generators and UPS, and people are not aware of it enough. Therefore, in many emergency power supply occasions, generators and UPS are still the main emergency power supply methods to realize the function of EPS. In terms of providing emergency power supply capabilities, these two methods have exposed many shortcomings.

Using diesel generator sets as emergency power supply is the most common emergency backup power supply at present. Due to the large capacity of diesel generators, they can be operated in parallel and have a long continuous power supply time, so they have a long application history. However, it takes at least a certain amount of time from the time the generator receives the start signal after the power outage to the time when the generator voltage, frequency, etc. reach a stable power supply. During this period, all electrical equipment stops working, which may cause damage to a few equipment or safety issues of life and property. The start-up of EPS generally does not exceed 25ms, so it will not affect the normal operation of the equipment. In addition, diesel generators have many disadvantages in emergency power supply occasions. For example, in high-rise buildings, diesel generator sets are generally placed in the basement, which is difficult to design and expensive. The equipment such as air intake, cooling, smoke exhaust, shock absorption, and silencer need to be fully considered, and there are fire hazards. Its oil tank is like a "time bomb". In case of fire, the consequences are disastrous; diesel generators are noisy, and there is a large amount of sulfur dioxide in the exhaust smoke, which is seriously polluting and affects the environmental protection.

　In today's society, people are trying every possible way to solve the problem of sudden power outages. As people's emergency awareness increases, the EPS emergency power supply industry will heat up rapidly, and various enterprises and institutions will soon launch an emergency power supply revolution. EPS will be recognized and widely adopted by people for its unique advantages.

jfejf

Not bad~Thank you for the tutorial~very informative...