The drive into the feasibility and application of uninterruptible power supplies(section two)

Any article of company general purpose inverter products for application examples to illustrate the working principle of the power of architecture composition and design methods
2 system components and working principle
The main power supply unit are: vector inverter, battery, DC / DC step-down DC-DC converter charging module, control logic board, DC / DC step-down operating power (+ 24V) module, output isolation transformer and LC filter, digital panel meters and energy-saving lamps and semiconductors man-machine interface unit, the structure shown in Figure 1
Still Siemens products, for example, take Ue = 510V is Uz = (O.875x510V) / (6 × 42) = 1.77V, taking into account the work of the battery and inverter reliability, battery discharge voltage Uz not less than 1.75V, That usually take Uz = 1.8V single battery termination voltage Uz = 1.8x6 = 10.8V, battery voltage Ud = 10.8 × 42 = 453 V, slightly less than the allowable minimum voltage inverter Ue (min) = 459 V, still 2.2.3 converter to meet the job requirements to determine the battery capacity Q
Battery capacity Q (A • h) depends on the battery discharge curve after the rated load supply current I and mains failure the load from the battery supply delay time T and battery discharge termination voltage Uz available after the battery manufacturer or discharge Select the table to calculate the empirical formula to calculate specific according to 15 kW load, outage duration lh example, the calculation result: Elect 50A.h battery 42
2.3 DC / DC step-down DC converter charging board
Charging module works using IGBT power electronic devices composed Buck (Buck) isolated DC-DC converter, voltage is l 200V. The battery capacity of the current press 0.1C (10) charging board can output current 10 ~ 20A, the output voltage of 274 ~ 300V adjustable, can 400A • h or less floating charge the battery pack into the battery pack to an equal number of Several groups (for example, 42 batteries divided into two groups 21, the charging voltage of only 287 ~ 289V), can reduce the charging module's output voltage, so that the module structure can be simplified to reduce the cost of this charge sheet also in parallel
2.4 rectifier diode
Using high-power diode rectifier DC isolation switch, when the mains is normal, the diode in the off state, cut off the battery pack and inverter access, but the drawback is the battery float charging when possible because of the high terminal voltage and mains After the rectified DC voltage output caused by discharge can not be filled when the mains power is turned on when the diode transient, battery spark, can do load mains and battery powered instantaneous conversion online uninterruptible The key aspects of the power of
2.5 DC / DC step-down operating power (+ 24V) module
Use Buck Buck DC / DC-DC converter can be universal inverter DC voltage into a logic control board point voltage required +24 V, for digital panel meters and energy-saving lamps and semiconductors with the man-machine interface unit
2.6 Digital Panel Meters and energy-saving lamps and semiconductors Human Interface Unit
Digital panel meters and energy-saving lamps and semiconductors human interface modules have man-machine display interface monitoring system, its functions are: charging panels and battery voltage, output current, input mains voltage, output voltage; power start-stop operation; operating parameter display; power supply status display; alarm and fault status to achieve four remote functions via RS485 and PC communication, shown in Figure 2

Balancing Manager 2.7 battery and battery detection system
Because the online uninterruptible power supply batteries used more, mostly based on past UPS battery failure and affect the whole system crashes lesson in battery increases the battery data logging devices (the company's own development) to detect the voltage of each cell within resistance, discharge current and ambient temperature, such logging devices can detect up to 128 batteries, to keep charging and voltage of each cell during discharge consistent with the company developed a battery can maintain this balance manager when the battery charge and discharge The consistency, the backward battery singled out, early detection of problems
2.8 output isolation transformer and LC filter
Because the power inverters output voltage waveform is a high frequency wave ladder, to make the output waveform is a perfect sine wave, so in the back of the isolation transformer coupled LC filter, the inductance value selected to 1.5 mH, a capacitance value of 20μF and in order This continuous increase in carrying capacity and reliability of power supply, avoid rush scrambling load, the output of the ac frequency converter is terminated with a △ / Y isolation transformer, the ratio is 300: 380, select the relationship to change than the regulated output Accuracy (due to the battery discharges gradually decreased to DC459V DC voltage, the actual voltage at the inverter output is AC 325V), which is the key to on-line uninterruptible power supply, but the drawback is that makes the drive power becomes small.