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What is the principle of UPS synchronous phase locking?
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What do you mean by primary phase locking and secondary phase locking of UPS?
To be precise, it should be a first-stage phase-locked loop and a second-stage phase-locked loop. A synchronous control scheme of high-power parallel UPS based on TMS320C240DSP controller of TT company is introduced in detail. Synchronization with power grid and UPS in parallel system become the key to control parallel UPS system. The core of UPS parallel system is high-precision phase-locked loop, and analog phase-locked loop is a mature technology, which has been widely used in many fields with its unique excellent performance. However, with the development of digital technology, full digital control of UPS is the general trend. Therefore, the phase-locked loop gradually changes to digital. Compared with analog phase-locked loop, digital DSP controlled phase-locked loop is more convenient to realize. At the same time, it can be realized by software instead of hardware, and it can also be designed in a unified way with other functions of the system to save costs. 1TMS320C240DSP controller introduction TMS320C240 is a 16-bit fixed-point arithmetic DSP specially designed for digital motor control, which provides an ideal solution for control system application. It has the following main components: three general timers, three full comparison units, three pairs of comparison /PWM pulses with dead-time control, three single comparison units, three comparison /PWM pulses and four capture pin caps for high-speed I/O management; Two sets of 8-channel 10-bit 10μs A/D converters, watchdog timer and timer interrupt timer; On-chip ROM or flash memory, etc. 2. UPS synchronous control scheme of parallel system 2. 1 UPS phase-locked control principle. Both the mains voltage waveform and UPS output voltage waveform are sine waves. Let the frequency of UPS inverter voltage be f and the frequency of mains voltage be f 1. The instantaneous value of the mains voltage waveform can be expressed as μ1= um1sin ω1t = um1sin2π f1t The instantaneous value of the UPS inverter output voltage waveform can be expressed as μ = um sin (ω t θ -θ is the phase angle of the UPS output waveform lagging behind the mains to realize UPS and the mains. The key is how to realize 2π F 1t = 2π ft θ. Only by changing f can θ decrease gradually, and finally θ=0 and f=f 1. When the UPS output waveform is ahead of the mains waveform, it is necessary to reduce the frequency of UPS output voltage. That is, f=f 1-θ/2πt When the waveform of UPS output voltage lags behind the commercial power, it is required that the frequency of UPS output voltage should be increased, that is, f=f 1+θ/2πt 2.2 can realize synchronous phase locking of parallel UPS systems. When the parallel system UPS switches between the commercial power and the inverter, if the output waveforms of the two are inconsistent at the switching moment, on the one hand, the power supply will be interrupted, on the other hand, it may be interrupted due to two factors. In order to ensure that there is no circulating current between the mains supply and the inverter in UPS system, it is necessary to ensure that the phases of the mains supply waveform and the inverter waveform are close. Therefore, a device is needed to detect the phase change of the commercial power, and control the phase and frequency of the inverter output voltage to keep the inverter and the commercial power running synchronously. The two-stage phase-locked structure can be used for the phase-locked of UPS in parallel system. Among them, the primary phase-locked loop (PLL) is also called external synchronization, which means that each UPS in parallel system tracks the phase and frequency of the commercial power and controls the phase synchronization with each other, that is, the synchronization between UPS and bypass commercial power is realized, and the secondary PLL is also called internal synchronization, which means that the frequency and phase tracking and synchronization control are carried out according to the output voltage of each UPS, so as to realize the synchronization between each UPS. PI regulators are used in both stages of PLL, which makes the internal synchronization faster and has high accuracy (= within = 10us), thus ensuring the minimization of parallel circulation between UPS. External synchronous PI regulator is slow, ensuring smooth switching of bypass and inverter. Each PLL includes phase error detection and regulator adjustment. The following describes how all stages of PLL are implemented. (1) The inputs of two UPS synchronized externally, that is, the commercial power, are shaped into square waves by the comparator circuit. After being synthesized by synchronous bus, the square wave signal is sent to CAPI pin of DSP capture unit of each UPS, and the rising edge or falling edge is set as capture. When the square wave signal jumps correspondingly, the value of the 1 interrupt reading counter is captured as the feedback signal of the PI regulator, and the phase difference can be obtained by comparing with the set value, and then the adjustment is formed through the operation of the PI regulator. (2) The internal synchronous T2 counter is used as the phase and frequency reference of UPS sine output. In order to ensure the synchronization between all UPS, all UPS use T2CNT to generate a square wave, which is synthesized by the synchronization bus and sent to the CAP2 ports of all UPS. When the square wave signal jumps correspondingly, it will enter Capture 2 to interrupt clearing T2CNT to ensure that the given internal synchronization is synchronous. In the interrupt corresponding to the midpoint of the sine wave, the value of T2CNT is read as the feedback quantity, which is compared with T2PR/2, and the value of TIPR is changed by the adjustment quantity obtained after the PI regulator operation, so that the sine wave output by the inverter is synchronized with the T2 counter, and the inverter output is kept synchronized.
1 Like 227 Browse 20 18-09-27
Does the internal circuit of UPS power supply need PLL circuit?
The answers of the following brothers are better together, hehe, offline UPS does not need it, online UPS does. In addition to locking the bypass frequency for the inverter output frequency of on-line UPS (this is to ensure that the UPS changes from the mains inverter state to the bypass state, or the phase remains unchanged when the bypass state changes to the mains inverter state), when the input sources of several machines are power grids with different phases and frequencies during the parallel operation of UPS, it is often necessary to designate a host to ensure that the voltage frequency and phase of the mains inverter output from the slave machines lock the host. Here, the phase-locked source need not be accurate to 50 or 60Hz. The requirement of Theil certification in China is that the frequency range is plus or minus 4%, and for a 50Hz system, it is plus or minus 2Hz.
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How ups Synchronizes with the World
UPS power supply generally has three-level protection. 1 means that it stabilizes the voltage and frequency when the mains supply is normal. 2. When the mains supply is interrupted or seriously unstable, it is powered by the battery. Third, when the battery is discharged and the bypass still has normal power supply, it will go to the bypass to supply power. On the other hand, when the inverter of UPS itself fails or the inverter is overloaded, it will automatically switch to bypass power supply. In other words, the bypass power supply is the last protection of UPS. In order to switch to the bypass power supply safely at this time without affecting the back-end equipment, it is required that the frequency output by UPS should be synchronized with the frequency of the bypass power supply, which is called phase locking. The specific principle is that UPS has two paths, one is sampling from the bypass, and the other is the standard sine wave of self-excited oscillation. UPS inverts according to standard sine wave. However, the frequency will change with the frequency of the bypass, but in order to protect the back-end load, UPS has a synchronization range, which is generally plus or minus 3HZ. If it exceeds this range or the bypass is out of power, UPS will only output according to the internal standards of the machine.
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Briefly describe the working principle of UPS.
UPS is the abbreviation of Uninterruptible Power Supply, which means "Uninterruptible Power Supply". It is a constant voltage and constant frequency uninterrupted power supply with energy storage device (usually battery) and inverter as main components. It can solve the problems of power failure, low voltage, high voltage, surge and noise in the existing power supply, and make the computer system run more safely and reliably. Now it has been widely used in computer, transportation, banking, securities, communication, medical treatment, industrial control and other industries, and is rapidly entering the family. Below, let's briefly understand the working principle of UPS. When we don't use UPS, terminal devices such as PC and printer are directly connected to the power supply. When using UPS, terminal devices such as PC and printer are connected to UPS, and UPS is connected to power supply. When the mains input is normal, UPS will stabilize the mains and supply it to terminal devices (compared with UPS, we call these terminal devices loads). At this time, UPS is an AC mains voltage regulator, and it also charges its own built-in battery. When the power supply is interrupted (such as power failure), UPS will immediately provide 220V alternating current to the load through inverter conversion to keep the load working normally and protect the hardware and software systems of the load from being damaged. Second, the impact of commercial power on home PC and its terminal equipment If our PC, computer network and other equipment do not use UPS, what impact will it have? Many people have a common misunderstanding that the electricity we use is continuous except for occasional power outages. Actually, it is not. As a public power grid, commercial power system is connected with thousands of loads, some of which are inductive, capacitive and switching power supplies. They not only get electric energy from the power grid, but also adversely affect the power grid itself, worsen the power supply quality of the power grid or local power grid, and cause waveform distortion or frequency drift of commercial power supply voltage. In addition, unexpected natural and man-made accidents, such as lightning strike, open circuit or short circuit of power transmission and transformation system, power plug plugging and unplugging errors, etc. , will endanger the normal power supply, thus affecting the normal work of the load. In particular, personal computers, network equipment, communication systems, medical equipment, etc. They are all very sophisticated electronic devices, and their influence is particularly prominent. For PC, the monitor and host need normal power supply. Especially memory, has higher requirements for power supply. It is a kind of storage device that relies on electric energy, and it needs constant refreshing action to keep the stored content. Once the power is cut off, the stored contents will disappear immediately. If there is abnormal power failure, the information in the memory will not be saved to the hard disk and other storage devices, resulting in the loss of value due to complete loss or incompleteness, wasting a lot of work energy and time; And UNIX, Linux and other operating systems (which are used by many computer enthusiasts now), if they are not shut down normally, the system information in the memory will not be written back to the hard disk, which may also cause the system to crash and cannot be restarted; In addition, although the hard disk in the computer uses magnetic storage media, it will not lose information because of power failure, but sudden power failure will damage the physical head of the hard disk being read and written, or system files will cause file allocation table errors when maintaining the file system, thus causing bad tracks on the hard disk, and even leading to the scrapping of the whole hard disk. In addition, most operating systems can set virtual memory at present. Due to the sudden power failure, the system had no time to cancel the virtual memory, resulting in "information fragmentation" on the hard disk, which not only wasted the storage space of the hard disk, but also caused the machine to run slowly. Computer power supply is a kind of rectifier power supply. Excessive voltage may cause the rectifier to burn out. However, voltage spikes, transient overvoltage and power noise may all enter the motherboard through the rectifier, which will affect the normal work of the machine and even burn out the host circuit. Generally speaking, the standard sine wave (220V, 50Hz) is an ideal state, but in practice, according to the test of power experts, there are several situations that often occur in the power grid, causing interference or damage to computers or precision instruments: surge, high voltage spike, transient overvoltage, voltage sag, conductor noise, frequency drift, continuous low voltage, power interruption and so on. 1. Power surge: the effective value of the output voltage is higher than the rated value 1 10% for one or several cycles. Surge is mainly due to the high voltage caused by the sudden unloading of the power grid when the large electrical equipment connected to the power grid is turned off (such as the common household air conditioner is turned off) (we all have such personal experiences: the peak period of electricity consumption is from 6 pm to 9 pm, the mains voltage is generally low, and the lighting at home is dim. After the peak power consumption, for example, around 10:00 in the afternoon, you 2. High voltage spike: refers to the voltage with a peak value of 6000V and a duration from one ten thousandth of a second to half a period (10 ms). This is mainly caused by lightning strike, arc discharge, electrostatic discharge or switching operation of large electrical equipment. 3. Switching transient: refers to the pulse voltage whose peak voltage is as high as 20000V, but its duration is between one millionth of a second and one ten thousandth of a second. The main causes and possible damages are similar to those of high-voltage sharp pulses, but the solutions are different. 4. Power sag: refers to the low voltage state where the effective value of the mains voltage is between 80% and 85% of the rated value and lasts for one to several cycles. Large equipment startup, large motor startup or large power transformer connection may cause this problem. 5. Electrical line noise refers to high-frequency interference such as radio frequency interference (RFI) and electromagnetic interference (EFI). The operation of motor, the action of relay, the work of motor controller, broadcast emission, microwave radiation and electric storm will all cause line noise interference. 6. Frequency change: refers to the power supply frequency change exceeding 3Hz. This is mainly caused by unstable operation of emergency generator or unstable power frequency. 7. Undervoltage: refers to that the effective value of the power supply voltage is lower than the rated value and lasts for a long time. The reasons include: start-up and application of large equipment, switching of main power lines, start-up of large motors, and line overload (this problem exists in many areas of China). 8. Power outage: that is, the power outage we usually encounter. The reasons are: circuit breaker tripping, mains interruption and power grid failure. Three. Classification of UPS UPS has developed from a rotating generator in the 1960s to an intelligent static all-electronic circuit today, and it is still developing. At present, UPS generally refers to static UPS, which can be divided into three categories according to its working mode: standby, online interaction and online. 1. standby UPS: when the commercial power is normal, it directly supplies power to the load, and when the commercial power exceeds its working range or power is cut off, it is converted into battery inverter power supply through the changeover switch. Its characteristics are simple structure, small volume and low cost, but the input voltage range is narrow, the output voltage stability accuracy is poor, there is switching time, and the output waveform is generally square wave. The schematic diagram is as follows: 2. Online interactive UPS: When the commercial power is normal, it directly supplies power to the load; When the commercial power is low or high, it is output through the internal voltage stabilizing circuit of UPS; When the commercial power is abnormal or power is cut off, it is converted into battery inverter power supply through the changeover switch. Its characteristics are: wide input voltage range, low noise, small size, etc., but it also has switching time, but compared with the general standby UPS, this model has stronger protection function and better inverter output voltage waveform, which is generally sinusoidal. The schematic diagram is as follows: 3. When the commercial power is normal, the online UPS is rectified by the commercial power to provide DC voltage for the inverter to work, and the inverter provides AC power for the load. When the commercial power is abnormal, the inverter is powered by the battery, and the inverter is always in working state to ensure uninterrupted output. Its characteristics are extremely wide input voltage range, no switching time and high output voltage stability precision, which is especially suitable for occasions with high requirements for power supply but high cost. At present, almost all UPS with power greater than 3KVA are on-line UPS. The schematic diagram is as follows: UPS is divided into small capacity below 3KVA, medium and small capacity between 3 kva- 10KVA and medium and large capacity above 10 kva according to output capacity. UPS can be divided into three types according to input/output modes: single-phase input/single-phase output (abbreviated as single input and single output), three-phase input/single output (abbreviated as three-input and single output) and three-phase input/three-phase output (abbreviated as three-input and three-output). For users, three-phase power supply is convenient to distribute power and load, and each phase bears a part of load current, so the power supply mode of medium and large power UPS is mostly three-phase input/single-phase output or three-phase input/three-phase output. Backup UPS is mainly used to provide power protection for a single PC. It has the characteristics of small size, low price and simple operation, and is very suitable for home use. Therefore, when you buy a UPS for your home computer, please choose a standby UPS. Online UPS can solve almost all common power problems. When there is commercial power, its function is to stabilize the voltage and prevent power supply fluctuation interference. Because of its perfect function, its cost also rises with the enhancement of performance, which is much more expensive than backup UPS. Online UPS is mainly used for some computer equipment, medical instruments and so on. The requirements for power supply are very strict. Generally, it is used in series with multiple external storage batteries to extend the power supply time, and most of them are configured as units. Intelligent UPS is a major development trend of UPS today. With the application of UPS in network system, network managers emphasize the protection of the whole network system, hoping that when the power supply system fails, the whole network system can continue to work without interruption. Therefore, it is a new trend to equip UPS with microprocessor to make it intelligent. The combination of hardware and software in UPS greatly improves the function of UPS, and can monitor the operation status of UPS, such as output voltage frequency of UPS, grid voltage frequency, battery status, fault record and so on. The software can also be used to detect batteries, automatically discharge and charge, and remotely switch batteries. Network managers can analyze the power supply quality according to this information and take corresponding measures according to the actual situation. When UPS detects the interruption of power supply network, UPS will automatically switch to battery power supply. When the battery power supply capacity is insufficient, immediately notify the server to prepare for shutdown, and shut down before the battery runs out. The intelligent UPS communicates with the computer through the interface, so that the network administrator can monitor the UPS, so the function of its management software is extremely important. What is a standby UPS? Usually charge the battery. In case of power failure, the inverter switches to the working state urgently, and converts the direct current provided by the battery into stable alternating current output. Standby UPS is also called offline UPS. The standby UPS has a time switch of 2 to 10 milliseconds, which is not suitable for key power supply places. In addition, the standby UPS can only supply power for a few minutes to ten minutes. The advantages of standby UPS power supply are: high operating efficiency, low noise and relatively cheap price, which is mainly suitable for occasions with little fluctuation of mains electricity and low requirements on power supply quality. What is online UPS Online UPS: When online UPS works, firstly, the commercial power is converted into direct current to charge the UPS battery, and at the same time, the inverter (see the prompt) converts this direct current into alternating current to supply power to the load. Because the commercial power has gone through the conversion process from AC to DC and then to AC, the original interference and pulse voltage components of the commercial power have been filtered very cleanly, so the voltage of online UPS inverter is very stable. Because the inverter circuit is always working, when there is a power failure, UPS can immediately convert its stored electric energy into alternating current through the inverter to supply power to the load, thus achieving the switching goal of zero interruption of output voltage. Double conversion also means that the output voltage of UPS is converted from AC to DC twice. And high frequency means that UPS works in high frequency environment. The advantages of high-frequency UPS are small size, light weight and high working efficiency, while the disadvantages are poor overload and impact resistance. What is online interactive UPS Online interactive UPS: This is an intelligent UPS. The so-called on-line interactive UPS means that when the input commercial power is normal, the inverter of UPS works in the opposite direction (i.e., the rectification working state) to charge the battery pack; When the commercial power is abnormal, the inverter will immediately turn into the inverter working state, and the battery power will be converted into AC output, so the online interactive UPS also has conversion time. Compared with standby UPS, online interactive UPS has stronger protection function, and the output voltage waveform of inverter is better, which is generally sine wave. Its biggest advantage is that the software function is stronger, and it can easily access the Internet to remotely control and intelligently manage UPS. It can automatically detect whether the external input voltage is within the normal range, and if there is deviation, it can step up or step down through the voltage stabilizing circuit to provide a relatively stable sine wave output voltage. But also can communicate with computer through data interface (such as RS-232 serial port). Through the monitoring software, users can directly monitor the power supply and UPS status from the computer screen, which simplifies and facilitates the management and improves the reliability of the computer system. This kind of UPS combines the advantages of high efficiency of standby UPS and high power supply quality of online UPS, but its frequency stabilization characteristics are not ideal and it is not suitable for constant delay UPS power supply.
58 Zan 5,017 Browse 20 17-09-24
Working principle of UPS power supply
UPS uninterruptible power supply immediately enters the battery inversion state; In order to prevent the mains from switching back and forth, UPS will turn into the mains inverter state only when the mains is restored to170 ~ 270 V ~ 270 V. Detection and control of commercial power frequency The purpose of detecting commercial power frequency is to serve as the basis of inverter phase locking, and adjust the inverter phase by adjusting the zero-crossing point of the inverter, so that the inverter output and the commercial power input in the commercial power state are basically in the same frequency and phase. When the commercial power is connected, UPS detects the frequency of the input commercial power as the output frequency of the inverter; When the battery is turned on, the frequency output by the frequency converter is set to the previously output frequency. When the commercial power is normal, phase locking is implemented. The inverter frequency follows the mains frequency first, and the frequency is the same before tracking the phase. By changing the inverter frequency, the inverter and the mains are in phase. After phase locking, the phase difference between inverter and commercial power is less than 3 degrees, and the frequency error is less than 0.0 1Hz. When the mains frequency exceeds the range of 47 ~ 53 Hz, UPS will immediately switch to the battery inverter state without phase locking. Only when the mains frequency returns to 48 ~ 52 Hz, UPS will phase lock again and switch to the mains inverter state. The square wave of 38.4kHz emitted by the CPU of the triangular wave generator is converted into a square wave of 19.2kHz by a frequency dividing circuit composed of an operational amplifier, and then integrated into a triangular wave by an integrator. The CPU of the standard sine wave generator sends out an analog sine wave with a frequency division of 128, which is filtered by a second-order low-pass filter to generate a standard sine wave. The standard sine wave of PWM signal is compared with the sine wave feedback signal of inverter output voltage, and the PWM signal is generated by triangle wave cutting. The inverter voltage regulating CPU reads the inverter voltage value every 16ms and compares it with the set voltage value. When the difference is higher than 10V, the CPU immediately adjusts the standard sine wave, thereby adjusting the PWM signal, so that the output voltage is correspondingly increased or decreased by 5V to narrow the difference. When the difference is lower than 10V, the CPU accumulates the difference. When the accumulated value reaches 30V, the CPU adjusts the standard sine wave to increase or decrease the output voltage by 2V. A/D reading of CPU The CPU reads the battery voltage, positive and negative bus voltages and internal temperature once every half cycle, and reads the mains voltage, inverter voltage and inverter current once every eight standard sine wave points (at the beginning of each cycle, the CPU changes the initial position of the reading point to make it read once every eight standard sine wave points, and the scanning effect is achieved by A/D reading at 128 points, and the reading value is stored in RAM).
8 Like 30, 156 Browse 20 19-09-22
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