The "high availability" of the USP power supply system requires that its system must have four elements of reliability, functionality, maintainability and fault tolerance, and the internal topology of the UPS plays a decisive role in the reliability and functionality of the system. The key elements of availability, especially maintainability and fault tolerance, depend to a large extent on UPS redundancy and power distribution system selection. This paper analyzes and evaluates the different topologies within the UPS to illustrate how the structure is “highly availableâ€. "The four elements of the power system have an impact.
First, UPS topology: offline UPS or backup power supply (SPS)
The offline topology is the simplest UPS structure, as shown in Figure 1. Under normal operating conditions, AC mains flows directly through the UPS to critical loads. The charger or "4-quadrant converter" converts the alternating current to direct current to charge the battery. The inverter is used to convert the DC power provided by the battery into AC power, and to supply power to the load when the utility power fails. The inverter normally runs in standby mode, keeping the battery charged. If the mains exceeds the specified range, the inverter supplies power to the load through the battery. This topology is called "single transform" because at any time, the power supply can only be converted once (AC is converted to DC or DC to AC). Under normal operating conditions, a small amount of AC power is converted to DC power to keep the battery powered. When the input utility power exceeds the specified range, the UPS detects a power failure, switches the relay action, and the output inverter starts the inverter to convert the DC power provided by the battery into AC power to supply power to the load.
Off-line UPSs are very inexpensive and are only suitable for home use or for powering a single computer workstation that only requires power-off protection applications. Sometimes off-line products have built-in surge suppression and/or “buck and boost†circuits that compensate for higher or lower input voltages, but do not attempt to provide any effective input power regulation.
Offline UPS scores higher in terms of design simplicity, while others are slightly lacking in other measurements. Off-line UPSs are typically used for single-phase, non-critical loads. In particular, it is not compatible with generators, which makes it unsuitable for three-phase applications.
Second, UPS topology: interactive UPS
The interactive UPS topology is shown in Figure 2. This structure is similar to the off-line UPS product, except that a transformer or inductor is added in series between the mains supply and the load. The inductor allows the UPS inverter to "interact" with the input power and regulate the output power connected to the load. This means that the "buck and boost" circuit can be adjusted accordingly when the input voltage is high and low.
The four-quadrant converter is typically a constant voltage device. When the load or input voltage changes, the four-quadrant converter makes a corresponding change by adjusting the output phase angle. Frequent changes in load will cause the battery to discharge, and frequent battery discharge will greatly shorten its service life.
Another downside of the interactive UPS product is that it can't completely isolate the critical load from the input power supply if it is not battery powered. Frequent frequency perturbations and poor power quality will directly affect important loads. If electrical isolation is not implemented, common mode noise will also directly affect the normal operation of the load.
Another downside of the interactive UPS product is that it can't completely isolate the critical load from the input power supply if it is not battery powered. Frequent frequency perturbations and poor power quality will directly affect important loads. If electrical isolation is not implemented, common mode noise will also directly affect the normal operation of the load.
Like an offline UPS, an interactive UPS product may be less expensive and more efficient because it only supplies power to critical loads when the input power is abnormal and only operates during battery operation. Compared to off-line UPS, interactive UPS devices suffer from loss in efficiency due to their series inductors and power regulation. In addition, when the UPS is converted to battery power, there is usually at least one (but measurable) voltage drop.
Generator compatibility
Off-line UPS and interactive UPS products require a very stable frequency and phase of the input power supply. The power supply frequency must be stable because the inverter must track the power supply frequency to calibrate the voltage and current so that the system output frequency is the same as the input frequency unless the UPS is running through the battery.
A typical operational problem is that when the other loads on the generator are started, the output frequency of the generator will change greatly, causing the off-line UPS or the interactive UPS to discharge through the battery. This problem is particularly evident on natural gas generator sets. Repeated charging and discharging of the battery may cause overdischarge of the battery, which will greatly shorten the battery life. Another potential problem is that the generator output will be unstable when the UPS load is loaded, which means that the sudden increase of the UPS load will cause the generator voltage and frequency to drop, which will cause the UPS to enter the battery discharge operating state. When the generator output is stable, the UPS returns to the normal state. If the generator output voltage drops again, the UPS will enter the battery discharge state again.
The above problem does not occur for a double-conversion UPS. The double-conversion UPS adjusts the input supply and allows for large variations in the supply frequency while continuing to provide a stable output frequency without the need for battery power. Moreover, major manufacturers of dual-conversion UPS have developed techniques to reduce output current distortion, greatly improving the compatibility of UPS and generators, and making load specification selection more accurate. The double-conversion UPS capacity and generator capacity ratio can reach 1.25~1.5:1, and no operation problems will occur.
Third, UPS topology: linear interactive structure with power factor correction (including "Delta transform" products)
In recent years, several companies have launched online interactive three-phase UPS products with power factor correction. Compared with offline products and general interactive products, these products improve the regulation performance of the power supply and improve the power quality of the output. But at the same time it also has some disadvantages, such as active power regulation will reduce efficiency. In fact, when with a non-linear load (typically a computer load), its efficiency is generally lower than that of a double-conversion UPS product. And the complexity of this product structure is often more than the double-conversion UPS. And to make it easy to mislead users, this type of online interactive product is even labeled as an "online" product because its inverter is always "running", providing voltage regulation or input power factor correction.
Traditionally, these products should be referred to as inter-acting UPSs, where series transformers and output inverters interact with input mains to adjust the output voltage. Some products have small input inverters/chargers (sometimes referred to as "delta" inverters) to regulate the input voltage. The small inverter is generally connected to the DC bus. The DC bus provides a channel for power conversion of the output (main) inverter. The output inverter corrects the input power factor. When the power is off, the energy output of the battery is inverted. Power supply protection.
In normal mode (standard input power waveform, UPS load is linear load), input isolation switch, mains input static switch and output isolation switch are closed, and the mains supply directly to the load output. The input inverter is used as a charger to charge and charge the battery system. In the above ideal (non-realistic) state, the main inverter is not working. When the UPS input voltage has an abnormal condition, the delta converter generates the corresponding voltage through the buck/boost transformer and the input.
The input voltages are superimposed (added or subtracted) to adjust the output voltage to ensure stable output. This regulation principle is similar to some electronic voltage regulators currently on the market. When the input voltage exceeds the adjustable range, the main inverter starts to work, and the DC output provided by the battery is inverted to provide full-scale output power. At this time, the mains input static switch must be disconnected to prevent the power supply from being reversed to the input side. Its role is similar to offline UPS.
If the online interactive UPS uses a rectified mains input static switch, when the input power supply fails, it is very susceptible to the fault, because they can not be quickly shut down, causing the inverter to reverse supply to the failed input power supply. Then close.
Online interactive UPS (or Delta Transform) also provides load harmonic current and input power factor correction. The main inverter produces the required compensation current—both harmonic current and fundamental current. As long as the inverter is running, whether it is used for voltage correction inverter / charger (Delta converter), or the main inverter for harmonic current and power factor correction, additional losses will occur, greatly reducing equipment efficiency Therefore, its actual efficiency is much lower than its advertised efficiency.
Fourth, UPS topology: double conversion online UPS
A true online or dual conversion UPS product (shown in Figure 4) is a very popular UPS topology. The rectifier converts the input AC power into DC power, and supplies power to the internal DC bus of the UPS. The output inverter converts the DC into AC, and outputs the regulated AC power to supply power to the important load. During normal operation, the battery connected to the DC bus is float charged. When the input power is outside the specified range, the battery supplies power to the inverter and important loads.
The advantages of the double conversion online UPS configuration are as follows:
(1) The critical load is completely isolated from the input AC.
(2) The important load is always powered by the output inverter, while the output inverter is always powered by the internal DC bus. When the input power fails, there is no switching drop in the output voltage because the inverter is always running through the DC input. The voltage and frequency of the input mains may vary, but the double conversion UPS will not be affected because the rectifier will only
Provides DC power to the DC bus. For example, the UL33 Series UPS can operate for long periods of time, even when the battery input voltage is 15% lower than its nominal voltage. It can continue to operate at a voltage 20% lower than the nominal voltage without draining the battery. Similarly, if the input frequency is below or outside the specified range, the rectifier will continue to provide DC power, while the output inverter will continue to output 50Hz power instead of battery.
(3) The output inverter is usually equipped with an isolation transformer that can provide another neutral line. The UPS thus provides electrical insulation and provides common mode noise protection for the load.
(4) The double-conversion UPS has a built-in dual-input wiring structure, that is, a rectifier input and a bypass circuit input terminal, respectively. Users may choose a single-input UPS for ease of installation, but dual-input UPS products are more fault tolerant. (5) A true double-conversion UPS can be used in a dual-bus power system. In all operating modes, the double-conversion UPS within the system is synchronized with a specified reference source: mains, battery, or standby generator operating mode.
(6) If the input power line fails, the UPS will enter the battery power supply mode. At this time, the UPS rectifier will prevent the current from being reversed from the input of the DC bus to the previous stage.
V. Conclusion
All UPS topologies provide power-off protection and play a role in the current power protection industry:
(1) Off-line UPS is a simple and low-cost power-off protection solution. Only available for single-phase work computer applications.
(2) The performance of the interactive UPS is greatly improved compared with the offline type, but it still cannot completely eliminate the faults and interferences caused by all the mains and the oil machine, and can provide certain power adjustment for small network applications. Suitable for single-phase computers and non-critical server applications.
(3) Online inter- UPS with power factor correction provides better power regulation for small network applications. Suitable for single-phase workstations and non-critical server applications. Not suitable for three-phase applications in the factory.
(4) Double conversion UPS has the best performance and provides all power failure protection. Recommended for all important single-phase and three-phase applications, especially for high availability and 24/7 operation.
Two Wheel Electric Scooter,2 Wheel Electric Motorcycle,2 Wheel Eec Electric Scooter,Self-Balancing Electric Scooters
Wuxi Jiangyin Xufeng Electric Bicycle Co., Ltd. , https://www.xufengrelxrides.com