Emergency Power Supply,  UPS Power System

UPS Uninterruptible Power System

Issuing time:2019-07-24 00:00

I. Introduction

    Ensuring normal power supply under all conditions is an important foundation for the metallurgical industry. To this end, in addition to the normal power supply of the industrial grid, a UPS power supply system is also required. UPS power supply is an important equipment to ensure the stability and continuity of power supply. Because of its high degree of intelligence, the energy storage equipment uses maintenance-free batteries, which neglects the maintenance and overhaul of the system during operation. In fact, the quality of the maintenance has a great impact on the life and failure rate of the power supply. The following describes the precautions and daily maintenance requirements of the UPS power supply according to the specific conditions and maintenance experience in use.

    Although the model and system capacity of the UPS power supply system configured by each enterprise are different, the principle and main functions are basically the same. In the UPS power type selection, each station has selected the online type. At this time, because the online UPS power system has zero time switching for various types of power supply, the length of its own power supply time can be selected, and it has voltage regulation, frequency stabilization, and purification. Features.

    When the UPS power system itself fails, there is an automatic bypass function. When it is necessary to repair, manual bypass can be used, so that maintenance and power supply do not affect each other. In terms of power selection, Laiwu Steel's medium and small bar production line used a medium power system.

    Second, UPS power system

    The UPS power system consists of four parts: rectification, energy storage, conversion and switching control. The voltage regulation function of the system is usually completed by a rectifier. The rectifier device adopts a thyristor or high-frequency switching rectifier, and has a function of controlling the output amplitude according to the change of the external power, so that when the external power changes (the change should satisfy the system) Requirement), the rectified voltage whose output amplitude is basically constant. The purging function is completed by the energy storage battery. Since the rectifier can not eliminate the transient pulse interference, the rectified voltage still has interference pulses. In addition to the function of storing DC direct energy, the energy storage battery is like a large container capacitor for the rectifier. The equivalent capacitance is proportional to the capacity of the energy storage battery. Since the voltage across the capacitor cannot be abruptly changed, that is, the smoothing characteristic of the capacitor is used to eliminate the pulse interference, and the purification function is also used, which is also called the shielding of the interference. The stability of the frequency is done by the converter, and the frequency stability depends on the stability of the oscillation frequency of the converter. In order to facilitate the daily operation and maintenance of the UPS power system, the system work switch, the automatic bypass switch after the host self-test fault, and the bypass switch such as the bypass switch are controlled.


    As shown in Figure 1, when the grid voltage is working normally, the load is supplied as shown, and at the same time, the energy storage battery is charged; when the power failure occurs, the UPS power supply starts to work, and the energy storage battery supplies the power required by the load. , to maintain normal production (such as thick black → shown); when the load is severely overloaded due to production needs, the grid voltage is directly rectified to supply power to the load (as shown by the dotted line).

    The UPS power system is mainly divided into two parts, the main unit and the energy storage battery. The rated output power depends on the host part and is related to the nature of the load. Because the UPS power supply has different load driving capabilities for different performances, the load power should normally meet 70% of the rated power of the UPS power supply. The selection of the energy storage battery capacity depends on the length of the backup time when the load power is determined. This time varies depending on the situation of each enterprise. It is mainly determined by the access time of the backup power supply, usually in minutes or hours. . Laiwu Steel's small and medium-sized bar production line is not allowed to be powered off due to production needs. Therefore, after detecting the grid voltage interruption, the UPS power system can start the power supply by itself, and as the energy storage battery is slowly discharged, the capacity of the energy storage battery will follow. The time will gradually decrease. Considering that the energy storage battery capacity drops to 50% at the end of life and leaves a certain margin, the working time of our UPS power system is 2 hours when the energy storage battery is full, and the half capacity is 1 hour. .

    2.1 Power working principle

    2.1.1 AC-DC conversion: The AC power from the power grid is stepped down by the autotransformer, full-wave rectified, and filtered into a DC voltage for supply to the inverter circuit. The AC-DC input has a soft-start circuit to avoid the impact on the grid when it is turned on.

    2.2.2 DC-AC inverter circuit: It adopts high-power IGBT module full-bridge inverter circuit, which has a large power margin. The output impedance is extremely small in the output dynamic range and has fast response characteristics. Due to the high-frequency modulation current limiting technology and the fast short-circuit protection technology, the inverter can work safely and reliably whether it is a power supply voltage transient or a load shock or short circuit.

    2.3.3 Control drive: Control drive is the core of complete machine function control. In addition to providing detection, protection, synchronization and various switch and display drive signals, it also completes SPWM sinusoidal pulse width modulation control due to static and dynamic Dual voltage feedback. The dynamic characteristics and stability of the inverter are greatly improved. The block diagram of the uninterruptible power supply is shown in Figure 2.


    2.3 power working process

    When the mains is normal 380Vac, the DC main circuit has DC voltage, which is supplied to the DC-AC AC inverter, and outputs a stable 220Vac AC voltage, and the mains charges the current. When the mains is under voltage or suddenly loses power, the battery pack feeds the DC loop through the isolation diode switch. There is no switching time from grid power to battery power. When the battery energy is about to run out, the uninterruptible power supply emits an audible and visual alarm, and stops the inverter operation at the lower limit of the battery discharge, and the alarm sounds long. The uninterruptible power supply also has an overload protection function. When an overload occurs (150% load), it jumps to the bypass state and automatically returns when the load is normal. When a serious overload (more than 200% of rated load) occurs, the uninterruptible power supply immediately stops the inverter output and jumps to the bypass state, at which point the front air switch may also trip. After the fault is eliminated, just close the switch and restart the work after restarting. In order to make the uninterruptible power supply work properly and avoid running under overload or underload, the power supply is first calculated before the power is turned on. FR-UK type uninterruptible power supply (nominal rated power) 80% resistive load design load capacity, generally with a computer load can withstand the following type of estimation:

    ∑i=1 n Pi≤P

    Where P is the uninterruptible power supply output capacity (VA) and P is the i-th load volt-ampere

    Each set of PLC power: 220V*0.5=110VA Power per station: 220V*2A=440VA IBM PC client and server: 220V*1.5A=330VA Total power: 10*110VA+4*440VA+11*330VA= 6?90VA 6?90VA/0.8=8112VA

    Therefore, in this bar production line, it is more suitable to use an uninterruptible power supply of 10KVA.

    Third, the use and maintenance of UPS power system

    1, UPS power system is on, off

    1.1 First boot

    (1) Closing in the following order: energy storage battery switch → automatic bypass switch → output switch is set to “ON” in sequence. (2) Press the “ON” button on the UPS start panel, the UPS power system will start slowly, and the “inverter” indicator will light. After 1 minute delay, the “bypass” light will go out, and the UPS will turn to the inverter power supply to complete the boot.

After about 10 minutes of running at no load, the load is started in the order of power-up from small to large.

    1.2 Daily boot

Simply press the UPS panel “ON” button and after about 20 minutes, you can turn on the computer or other instruments. Usually the power switch of the load device can be turned on after the UPS starts to enter stable operation (Note: The manual maintenance switch is in the "OFF" state when the UPS is in normal operation).

    1.3 Shutdown

Turn off the computer or other instruments first, let the UPS run for 10 minutes under no load, and then press the “Off” button on the panel.

    2, UPS power system use precautions

    Due to its high degree of intelligence, the UPS power system uses a maintenance-free battery, which brings a lot of convenience to the use. However, it should be paid attention to in many aspects during use to ensure safe use.

    (1) UPS power supply host does not require high ambient temperature, +5 °C ~ 40 °C can work normally, but requires indoor cleaning, less dust, otherwise dust and moisture will cause the host to work disorderly. The energy storage battery has higher temperature requirements. The standard operating temperature is 25 °C, and it should not exceed +15 °C to +30 °C. If the temperature is too low, the capacity of the storage battery will drop. When the temperature drops by 1 °C, its capacity drops by 1%. Its discharge capacity increases with temperature, but its life is reduced. If used at high temperatures for a long period of time, the battery life is reduced by about half for every 10 °C temperature increase.

    (2) The parameters set in the host cannot be changed at will during use. In particular, the parameters of the battery pack will directly affect its service life, but as the ambient temperature changes, the float voltage should be adjusted accordingly. Generally, at 25 ° C, the float voltage should be increased by 18 mV (relative to the 12 V battery) for every 1 ° C increase or decrease in ambient temperature.

    (3) When no external power is supplied by the UPS power supply system, the UPS power supply should be avoided with load. The load should be turned off first, and then the load should be turned on after the UPS power system is started. When the load is instantaneously powered, there will be a shock battery. The surge current of multiple loads and the required supply current will cause the UPS power supply to be instantaneously overloaded. In severe cases, the inverter will be damaged.

    (4) The power supply of the UPS power system is not large according to the requirements of use. In use, it is necessary to avoid adding extra power to the extra equipment, and it is not allowed to run for a long time under full load. However, the nature of the work determines that the UPS power system operates almost in an uninterrupted state. Increasing the high-power load, even if it is working under the basic full load condition, will cause the host to malfunction, and the inverter will be damaged in severe cases.

    (5) The output voltage of the self-supplied generator, the waveform, frequency and amplitude should be full of the input voltage requirements of the UPS power supply. The power of the generator should be much longer than the rated power of the UPS power supply. Otherwise, any condition will be dissatisfied. The UPS power supply is working abnormally or damaged.

    (6) Due to the high voltage of the assembled battery pack, there is a danger of electric shock. Therefore, the safety protection should be applied when loading and unloading the conductive connecting strip and output line. The tool should adopt insulation measures, especially the output contact should have anti-touch measures.

    (7) Whether it is in the floating charge working state or in the charging and discharging maintenance test state, it is necessary to ensure that the voltage and current meet the specified requirements. Excessive voltage or current may cause thermal runaway or water loss of the battery, and voltage and current will cause the battery to lose power. This will affect the service life of the battery. The former has a greater impact.

    (8) In any case, short-circuit or deep discharge of the battery should be prevented because the cycle life of the battery is related to the depth of discharge. The deeper the discharge depth, the shorter the cycle life. In the capacity test or during the discharge repair, it is usually sufficient to discharge 30% to 50% of the capacity.

(9) The battery should avoid large current charge and discharge. Although it can accept large current during charging, it should be avoided in the actual operation. Otherwise, the battery plate will be deformed and expanded, so that the active material of the plate will fall off and the internal resistance of the battery will increase. Large, the higher the temperature rise, the more serious the capacity will be reduced, and the life expectancy will be terminated early.

    3. Daily maintenance and overhaul

    (1) Under normal use conditions, the UPS power supply has little maintenance work, mainly dustproof and regular dust removal. Especially in areas with dry climate, there are more ash particles in the air. The fan inside the machine will bring dust into the machine. When the air is wet, it will cause the host to control the disorder, causing the host to work abnormally, and inaccurate alarms occur. Dust can also cause poor heat dissipation in the device. It should be thoroughly cleaned every quarter. The second is to check whether the connectors and connectors are loose or not in contact during dust removal.

    (2) Although the energy storage battery pack currently uses maintenance-free batteries, it only eliminates the previous measurement, ratio, and regular addition of distilled water. However, the influence of the external working state on the battery has not changed, and the impact of the abnormal working state on the battery has not changed. This part of the maintenance and repair work is still very important, and a large number of maintenance and repair work of the UPS power system is mainly in the battery part.

    a. The operation of the energy storage battery is all in a floating state, in which case the discharge should be performed at least once a year. Before the discharge, the battery pack should be balanced and charged to achieve the balance of the whole battery. Be aware of the backward battery that already exists in the battery pack before discharge. If one of the discharge processes reaches the discharge termination voltage, the discharge should be stopped. Continue to discharge and then remove the backward battery before releasing.

    b. Checking the discharge, not the first to pursue the release of the capacity, but to pay attention to the discovery and treatment of the backward battery, after the treatment of the backward battery and then the nuclear discharge test. This can prevent accidents, so as to prevent the backward battery from deteriorating into a reverse polarity battery.

    c. At normal time, each group of batteries should have at least 8 batteries as the labeled battery. As a reference for understanding the working condition of the full battery pack, the marked battery should be regularly measured and recorded.

    d. Items that need to be checked frequently during routine maintenance are: clean and test the voltage and temperature at both ends of the battery; whether there is looseness at the joint, corrosion phenomenon, and detection of the pressure drop of the connecting strip; whether the appearance of the battery is intact, whether there is shell deformation and leakage; Whether there is acid mist around the pole and safety valve; whether the host equipment is normal.

    e. Maintenance-free battery maintenance, not a nonsense, should be based on a broad sense of maintenance, to ensure the operation, daily management of thoughtful, meticulous and normative, to ensure that equipment (including host equipment) maintain good operating conditions, thereby extending The service life is guaranteed; the DC bus always maintains the qualified voltage and the discharge capacity of the battery; the battery operation and personnel are safe and reliable. This is the purpose of battery maintenance, as well as the content and rules of the battery operating procedures.

    (3) When the UPS battery system fails, the cause should be first identified, whether it is the load or the UPS power system; whether it is the host or the battery pack. Although the UPS host has a fault self-test function, but it is opposite to the point, it is convenient to replace the parts, but to repair the fault point, still need to do a lot of analysis and testing work. In addition, if the self-test part fails, the displayed fault content may be incorrect.

    (4) For the failure of the host to break down, break the insurance or burn the device, be sure to find out the cause and eliminate the fault before restarting, otherwise the same fault will occur in succession.

    (5) When a battery with reverse voltage, large voltage drop, large differential pressure and acid mist leakage is found in the battery pack, it should be restored and repaired in time according to the corresponding method. If it cannot be recovered and repaired, it must be replaced, but it cannot be different. Capacity, different performance, and different manufacturers' batteries are connected together, otherwise it may adversely affect the entire battery. Replace the battery pack whose life has expired in time to avoid affecting the host.

    Fourth, the conclusion

    Even the best equipment has a long life, and various types of failures can occur. However, good maintenance work can prolong life and reduce the occurrence of faults. This is the life of the person and the illness.

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