I have been working in hotels for many years, but I still don’t understand why hotel bathrooms need uninterruptible power supplies?

I have been working in hotels for many years, but I still don’t understand why hotel bathrooms need uninterruptible power supplies?

Most of the service industry is like this. Why does the UPS uninterruptible power supply need to be discharged?

The UPS system is composed of two categories of batteries: the UPS host. When the UPS works normally, it When charging, when the battery is fully charged, it will be in a float charge state. If there is no power outage for a long time, the battery's power will only enter but not exit. If the battery is overcharged, it will affect the service life of the battery. Therefore, perform regular and reasonable maintenance of the UPS battery. Discharge, regenerate the battery's performance and extend its service life. What are uninterruptible power supplies in hotel rooms?

Usually there is an uninterruptible power supply in the room, which is marked with words, and can be used for mobile phone charging, computer downloading, etc.

If you cannot find an uninterruptible power supply, you can use a card similar to a magnetic card key (such as a thicker business card, etc.) instead of a magnetic card key, and insert it into the power outlet to draw power. In this way, the power supply in the room and bathroom can be maintained when you go out. There will be no interruption.

Some rooms still have electricity without inserting the card, which is suitable for guests to charge their mobile phones or cameras, or for emergency use. But if the entire floor loses power, there will be no power in the sockets, unlike fire emergency lights. Uninterruptible power supply

UPS means "uninterruptible power supply" in Chinese and is the abbreviation of "Uninterruptible Power Supply" in English. It can ensure that the computer system continues to work for a period of time after a power outage so that users can emergency archive , so that you will not have your work affected or data lost due to power outage. It mainly plays two roles in computer systems and network applications: one is for emergency use to prevent sudden power outages from affecting normal work and causing damage to computers; the other is to eliminate surges, instantaneous high voltages, Improve power quality by eliminating "power pollution" such as instantaneous low voltage, wire noise and frequency offset, and providing high-quality power for computer systems.

New progress in three-phase uninterruptible power supplies

[Date: 2006-11-13] Source: Power Supply Technology Application Author: Wang Linbing, Zhejiang University, He Xiangning [ Font: Large, Medium, Small]

Abstract: A summary analysis of the module circuit topology, complete machine circuit structure and various popular control strategies of the three-phase uninterruptible power supply system was made, and the key points of uninterruptible Problems existing in power supply design and application and new hot spots in current research are finally predicted for the development trend of UPS

Keywords: three-phase uninterruptible power supply; inverter parallel connection; digital control

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O Introduction

For a long period of time in the future, my country's main power grid will still suffer from insufficient power supply, large voltage fluctuations and serious interference. The rapid development of various industries and fields has put forward increasingly higher requirements for power supply quality, especially the requirements for power supply quality of important systems, important departments and important power consuming devices with strong real-time nature and the actual situation of my country's power grid. The contradictions are becoming increasingly acute. Therefore, uninterruptible power supply (UPS), as a green power supply with stable voltage, stable frequency and purification, has become more and more the focus of people's attention. In order to continuously improve the performance of UPS, scientific researchers have done a lot of research on UPS systems and proposed many circuit topologies and control strategies.

1 UPS circuit topology

The reliable execution of UPS is inseparable from the coordination of each module. The following is a brief analysis of the UPS main functional module circuit topology.

1.1 Rectifier and power factor correction circuit

The rectifier circuit constitutes a DC power supply device in application and is the interface circuit between the public power grid and power electronic devices. Its performance will Affects the implementation and power quality of the public power grid. A high-efficiency UPS requires a high input power factor and minimizes the harmonic components of the input current. Traditional single-phase UPS mostly uses analog methods, while three-phase UPS mostly uses phase-controlled rectifier circuits and voltage-type single-tube rectifier circuits.

1.1.1 Traditional three-phase phase-controlled rectifier circuit and voltage-type single-tube rectifier circuit

The phase-controlled rectifier circuit uses semi-controlled power devices as switches, and there are The following issues:

1) The existence of grid-side harmonic current will reduce the grid-side power factor of the device and increase reactive power;

2) The phase-controlled rectification commutation method will lead to The voltage distortion of the power grid during the current period not only affects the performance of its own circuit, but also interferes with the power grid and brings adverse effects to other devices on the network at the same grounding point;

3) The phase-controlled rectifier link is a time-controlled rectifier The hysteresis link prevents rapid adjustment of the output voltage.

Voltage-type single-tube rectifier circuit is the abbreviation of three-phase uncontrolled rectifier bridge plus Boost circuit. Its disadvantage is: large current peak, which not only hinders the improvement of system power, but also increases conduction loss and switching Loss; in order to maintain the improvement of the grid-side power factor, the Boost circuit must have a certain boost ratio, which will cause the DC output voltage to be too high for the three-phase circuit.

1.1.2 Current-mode three-phase bridge rectifier circuit

The current-mode three-phase bridge rectifier circuit is shown in Figure 1. Its advantage is that the feedback control is simple and does not require By adding current feedback to the control circuit, the input current can be sinusoidal by simply adjusting the duty cycle of each switch; the voltage on the DC side is lower. The disadvantage is that the sinusoidality of the input current is not very good, and a parallel capacitor must be added to the input side to achieve phase shifting. This kind of circuit is now becoming one of the hot spots of research. This kind of circuit is suitable for high-power rectifier circuits where the power factor is not required to be high.

1.1.3 Voltage-type three-phase bridge rectifier circuit

The voltage-type three-phase bridge rectifier circuit is shown in Figure 2. It is characterized by the use of high-frequency PWM rectification technology. , the device is in a high-frequency switching state. Since the on and off states of the device can be controlled, the current waveform of the rectifier is controllable. The advantage of this circuit is that it can obtain an input current in the same phase as the input voltage, that is, the input power factor is 1, and the harmonic content of the input current can be close to zero; energy can flow in both directions, and normally energy flows from the AC side to the DC side. Flow, when the DC output voltage is higher than a given value, energy flows from the DC side to the AC side, with higher conversion efficiency. The disadvantage is that it is a Boost type rectifier circuit and has higher DC side voltage requirements. This kind of circuit is also a hot spot of research in recent years.

1.2 Battery pack and charge and discharge circuit

The battery pack is the energy storage unit of UPS. When the mains power is normal, it absorbs the energy from the mains power and stores it in the form of chemical energy. Once the mains power is interrupted, it converts the stored chemical energy into electrical energy to supply power to the inverter to maintain the continuity of power supply to the load. In small and medium-power UPS systems, the voltage of the battery pack is usually relatively low, so a charging and discharging circuit that can flow energy in both directions is usually used [4]. In order to improve efficiency in high-power systems, simplified circuits usually directly connect the battery pack to the DC bus.

1.3 Inverter circuit

The inverter is the core of UPS. It converts DC power into AC power with stable voltage and frequency required by the user. The following still uses the three-phase inverter as an object to analyze the research hot spots of inverters in recent years.

1.3.1 Three-phase half-bridge inverter circuit

Among the three-phase inverter circuits, the three-phase half-bridge circuit is the most commonly used. The characteristic is that it uses fully controlled devices to form an inverter, which has the advantages of high power density, good efficiency, small size and lightweight. This circuit facilitates the use of new control strategies to improve the quality of the inverter. However, it is difficult to achieve 100% independent load.

1.3.2 H-bridge inverter

For ultra-large-capacity inverters, due to the substantial increase in power levels, new structural requirements have been proposed for the inverter. Requirements, H-arm inverter is one of the choices. The output transformer of this inverter adopts a multi-winding connection method. The primary side of the output transformer uses three independent windings, and the inverter output uses three independent H-bridges. This control is convenient, but the cost is higher.

1.3.3 Three-phase four-leg conversion technology

Due to the inherent defects of the three-leg inverter itself in the three-phase circuit, people began to seek new Circuit structure, so a three-phase four-leg inverter appears, as shown in Figure 3.

The output of this circuit structure is a three-phase four-wire system. The three-phase voltages can be controlled independently and the control method is flexible. However, the algorithm of this topology is relatively complex. The PWM vector rotates in three-dimensional space. Digital control methods must be used to realize spatial PWM. Waveform generation, this circuit has become one of the hot topics of research in recent years.

1.4 Three-phase UPS complete circuit

1.4.1 Traditional three-phase UPS circuit structure

In the traditional three-phase UPS structure, the input uses thyristor rectification. The output uses an inverter, the battery is directly connected to the DC bus, and the rectifier also serves as a charger. The output is isolated by a transformer, which can achieve complete isolation of input and output, ensuring that disturbances in the power grid will not cause interference to the load. When the mains power is cut off, the battery outputs stable AC power through the inverter; when the inverter fails, the voltage is output through the bypass to ensure the reliability of the power supply. The main disadvantage of this structure is its relatively large size and weight.

1.4.2 High-frequency chain-type three-phase UPS

In order to reduce costs and reduce the size and weight of UPS, high-frequency chain-type three-phase UPS appeared, as shown in Figure 4. This kind of circuit eliminates the need for a huge power frequency transformer, and uses high-frequency rectification for the input, which can achieve higher input power factor and lower input harmonic current. Its disadvantage is that the input and output are not isolated by a transformer, and disturbances in the power grid may cause disturbances to the output of the UPS; the output three-phase voltage relies on the midpoint of the battery and capacitor to form a neutral line, so the positive and negative DC voltage amplitudes must be kept equal during control, otherwise The output neutral line will have a large DC component, which is detrimental to the load and the transformer in the load; the input adopts a three-phase four-wire system, and current flows through the neutral line, which may cause the neutral line potential to shift and cause interference to the load; the input and output are not isolated , the circulation problem in parallel connection is difficult to solve.

1.4.3 New online interactive UPS

Since the above two UPSs have to go through two full power conversions, the efficiency of the system is low, so as to improve the system efficiency. From the perspective of efficiency, a series-parallel compensation large-capacity structure has emerged, which is a new online interactive structure, as shown in Figure 5. The input and output of this topology also do not have transformer isolation, so there are disadvantages of high-frequency chain UPS. The output frequency of this kind of UPS must be consistent with the power grid, and its ability to suppress grid disturbances is not strong, so the power supply quality is worse than that of traditional three-phase UPS. Its characteristic is that the energy from input to output does not undergo full power conversion. It is also composed of two high-frequency converters, but converter 1 can only bear a maximum of 20% of the power. In terms of cost, this structure Lower cost. In terms of control method, converter 1 is a voltage compensator, used to compensate for the distortion of the grid voltage; converter 2 is a current compensator, used to compensate for the harmonic current of the load, and acts as full power when the mains power is cut off. The voltage-type inverter supplies power to the load.

1.4.4 High-frequency chain UPS with input and output isolation

Since the input and output of traditional power frequency UPS are equipped with isolation transformers, the output has good isolation characteristics, and high-frequency chain UPS has many advantages. Good input characteristics, therefore, this high-frequency chain UPS with input and output isolation appears as shown in Figure 6. Due to the shortcomings of high-frequency rectification, an autotransformer must be connected on the input side to reduce the voltage, which increases the weight and cost of the whole machine. In addition, because the input uses a high-frequency converter, the efficiency of the whole machine is higher than that of high-frequency chain UPS and traditional UPS. The efficiency is low. However, since the input power factor is 1 and there is no harmonic current, the total power consumed is lower than that of a traditional three-phase UPS.

1.4.5 UPS with parallel input and output

In this circuit, the input terminal is composed of multiple rectifiers connected in parallel to supply power to the DC bus, and at the same time, the DC bus supplies multiple The inverter provides DC voltage, and the output terminals of multiple inverters are directly connected to supply power to the load at the same time. This method can enhance the capacity of the UPS, increase the reliability of the system, reduce costs, and enhance maintainability. However, the more modules are connected in parallel, the more difficult it is to solve the problem of current sharing between modules.

2 Control technology of uninterruptible power supply

With the rapid development of control theory and various microcontrollers with rich functions and excellent performance, a variety of discrete control methods have emerged. The number of control feedback loops can be divided into single-loop, dual-loop, and multi-loop control. The control effect can be improved by increasing the number of feedback loops as much as the hardware allows.

From the perspective of control principles, it includes digital PID control, state feedback control, deadbeat control, repetitive control, sliding mode variable structure control, fuzzy control, neural network control, space vector control and other methods.

Digital PID control has good adaptability and strong robustness; the algorithm is simple and easy to implement with a microcontroller or DSP. However, there are two limitations: on the one hand, the sampling quantization error of the system reduces the control accuracy of the algorithm; on the other hand, the sampling and calculation delays make the controlled system a system with pure time lag, causing the PID controller to The stable domain is reduced and the design difficulty is increased.

Predictive control can achieve very small output current distortion and has strong noise immunity. However, this algorithm requires knowing the precise load model and circuit parameters, so it has poor robustness and is caused by numerical calculations. Delay is also a problem in practical applications. Hysteresis control has fast response speed and high stability, but the switching frequency of hysteresis control is not fixed, which reduces the reliability of circuit operation and worsens the spectrum of the output voltage, which is detrimental to system performance.

The basic idea of ??deadbeat control is to calculate the PWM pulse width of the next switching cycle based on the state equation of the inverter and the output feedback signal. Therefore, the output voltage can theoretically be adjusted in phase and amplitude. The values ??are very close to the reference voltage, and output voltage errors caused by load changes or nonlinear loads can be corrected within one switching cycle. However, deadbeat control is a control method based on an accurate mathematical model of the controlled object and has poor robustness.

Sliding control is a kind of nonlinear control, which is characterized by control discontinuity. This control can be used for both linear and nonlinear systems. This control method is highly robust. The disadvantage is that it is difficult to obtain a satisfactory sliding surface.

Repeated control is a control method based on the internal model principle. The purpose of using repetitive control in the inverter is to eliminate the periodic distortion of the output voltage waveform caused by the rectifier bridge load. The repetitive controller can eliminate the steady-state error caused by periodic interference. However, due to the control characteristics of repetitive control delaying one power frequency cycle, the dynamic characteristics of the UPS inverter using repetitive control alone are extremely poor.

Fuzzy control belongs to the category of intelligent control. The design of fuzzy controller does not require a precise mathematical model of the controlled object, so it has strong robustness and adaptability. Fuzzy control is similar to traditional PD control, so this control has a fast response speed, but its static characteristics are not satisfactory. Neuron network control is a control method that simulates the intelligent activities of the human brain's central nervous system. Neural networks have the advantages of nonlinear mapping capabilities, parallel computing capabilities and strong robustness, and have been widely used in the field of control, especially in the field of nonlinear systems. At present, certain results have been achieved in the design of neural network structures and learning algorithms. However, due to limitations of the hardware system, neural network control currently cannot achieve online control of the inverter output voltage waveform. Most applications use offline learning to obtain optimized control rules, and then use the obtained rules to achieve online control. control.

With harmonic injection PWM technology, the utilization rate of DC bus voltage can basically reach loo%. This method is very effective for voltage open-loop control systems, but in closed-loop control systems, since the initial phase of harmonic injection must be consistent with the fundamental wave, it is difficult to accurately locate the initial phase of the voltage fundamental wave in voltage instantaneous value control. application.

Space vector PWM has the advantages of small current distortion, high DC bus voltage utilization and easy digital implementation, so it has been widely used in recent years. This control method also requires an accurate model of the circuit.

Each of the above control schemes has its advantages, but it also has its shortcomings. The control scheme that simultaneously uses different control methods to form composite control has been widely used in practice and achieved good results.

3 Problems in the design and application of uninterruptible power supplies

American UPS manufacturer APC. company, summarized and summarized 5 problems that UPS power supply systems are currently facing and must be solved in the future:

1) Life cost cycle issues;

2) Uninterruptible power supply The adaptability and expandability of the system;

3) The issue of improving the availability of uninterruptible power supplies;

4) The manageability of uninterruptible power supplies to the power supply system;

5) Serviceability issues.

4 The latest development trend of uninterruptible power supplies

The development trend of uninterruptible power supplies is the multi-machine parallel redundancy of UPS, using redundant parallel technology to improve the capacity and reliability of UPS characteristics; the use of hardware devices with richer functions to achieve full digital control, so that various advanced complex control algorithms can be used to continuously improve the performance of UPS, that is, to develop towards digitalization and high frequency; the further intelligence and network of UPS ization, making the computer network an uninterrupted network.

4.1 The multi-machine parallel connection technology of UPS achieves redundancy

The parallel connection technology of UPS can bring the following benefits:

1) The capacity of the power supply system can be flexibly expanded;

2) A parallel redundant system can be formed to improve execution reliability:

3) Extremely high system maintainability, when single When the power supply fails, it can be easily replaced and repaired by hot-swapping.

Parallel technology can be used to form a redundant power supply system with fault tolerance. From the current information available, there are mainly the following redundant configuration schemes:

1) Centralized

2) Master-slave parallel control;

3) Decentralized parallel control;

4) Chain-type parallel control;

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5) Wireless parallel control.

Among these parallel connection methods, from the perspective of reliability, centralized control is the worst and wireless control is the best, which has also become a research hotspot in recent years.

4.2 Digitization and high frequency of UPS

The original UPS adopted analog control method, which had many limitations. With the continuous improvement of the calculation speed of digital processors, various advanced digital control methods have been realized, which makes the design of UPS highly flexible, the design cycle is shortened, and the efficiency is greatly improved. The high frequency of UPS effectively reduces the size and weight of the device, eliminates the audio noise of the transformer and inductor, and improves the dynamic response capability of the output voltage. Digital control methods have become a research hotspot in the field of AC power supply today. An inevitable development trend is for various methods to penetrate each other and combine with each other to form a composite control scheme. Digital composite control is a development direction of UPS control.

4.3 Intelligentization and networking of UPS

In order to adapt to the development of computer networks, UPS has begun to be equipped with RS232 interface, RS485 interface, USB interface, SNMP card and MODEM is combined and becomes a part of the computer network, which has the following excellent intelligent and networked characteristics.

1) The real-time monitoring function performs real-time high-speed sampling of various analog parameters of the UPS and the switching values ??indicating the working status to achieve digital monitoring.

2) Self-diagnosis and self-protection function The UPS analyzes and compares the various simulation parameters and working status data collected in real time as well as the data of key hardware devices in the system with normal values ??to determine whether the UPS There is a risk of malfunction. If there is a fault, according to the corresponding fault information level, the alarm will be alarmed through a friendly graphical interface and text prompts on the display screen of the control panel, or the alarm will be alarmed at the scene and in the control room by indicator lights and alarm beeps, or automatically. Call the police by calling the police, etc., and take corresponding protective actions.

3) Man-machine dialogue control method Large-scale UPS can provide users with a monitor LCD screen to display workflow and parameter information in graphics and text. Can provide visual menus for users to operate. It also provides help and constant reminders to guide users to handle faults in established ways, effectively preventing misoperations.

4) Remote control function In the era of networking, UPS should not only provide protection to the hardware devices directly powered by it, but also protect the execution programs and data in the entire network, as well as the protection of data. The transmission path is comprehensively protected, making it an uninterrupted network. This means that the UPS should be equipped with corresponding power monitoring software and SNMP (Simple Network Management Protocol) manager so that it has remote management capabilities. Users can perform remote monitoring and data exchange between the UPS and the network platform. Network communication operations make UPS an important part of the network system. In this way, the network administrator can monitor multiple UPSs through the network management software, and the managed UPSs can be in the same LAN or in different LANs, or even through the Internet, they can be incorporated into the network management system to manage the UPSs.

Due to the extensiveness and globalization of the Internet in the future, the complexity of the Internet will inevitably occur, and various forms of network systems will be connected together. As part of the network system, UPS is required to be able to implement monitoring on various network platforms. With the ultra-high-speed development of Internet, Intra and e-commerce, users will have higher and higher requirements for network availability. UPS extends from the protection of key network devices to the protection of the entire network path. Why does the Santak uninterruptible power supply keep cutting off the power on its own?

The UPS is connected to the mains power supply but "continuously" cuts off the power. The possible situations are: < /p>

1. For online UPS, if there is a problem with the inverter, the mains output will be cut off. Unless there is a problem with the mains, the power will not be cut off "always".

2. For backup UPS, if there is a problem with the mains power, it will switch to the inverter output. Unless there is a problem with the inverter, the power will not be cut off all the time.

When a power outage occurs, there is a problem with the inverter and the mains bypass circuit (the mains power is not good, or the bypass circuit is bad).

If your description is correct, I guess this UPS is not genuine and the warranty is difficult. Or maybe, just too old. It's not worth repairing anymore, buy a new one. Will the uninterruptible power supply in hotel rooms have power after a power outage?

The uninterruptible power supply in hotel rooms is not controlled by the room card and is directly connected to the external circuit. If the external circuit loses power, it has no power. Why does UPS use reactors in uninterruptible power supplies

UPS power supplies that use reactors are generally high-power UPSs, and they use controllable silicon rectifiers and filters. Controlled silicon UPSs will produce harmonics. It pollutes the power grid, so reactor filtering is required.

Only power frequency machines require reactors. Their main function is filtering, or in parallel operation, a reactor must be connected in series to reduce circulating current. Why is the computer room equipped with uninterruptible power supply

1. The computer room equipment is mainly composed of servers, computers, monitoring, communication and other important devices. Data transmission, reception and integration are all carried out here. In the event of a sudden power outage, important data will be lost. Failure to save in time resulted in loss. UPS uninterruptible power supply plays the role of uninterrupted power supply during power outages, allowing you to have sufficient time to store data or generate electricity.

2. The instantaneous voltage and current during a sudden power outage or incoming call will be very high. Some precision devices cannot withstand this instantaneous impact and will be burned. UPS has a voltage stabilizing function, and its existence protects it. These devices are safe in this situation.

3. Some work processes cannot be interrupted, such as surgery, experiments, scientific research, payment collection, etc. These places must be protected by power supply.