ENGINEERING ARTICLES

Solid-state Controls systems differ from off-line designs in the following ways: 1. Solid-state Controls offers an on-line, double conversion UPS system. Therefore, the client’s critical load is being powered continuously from the inverter. The battery is always being floated by the fully-rated rectifier/charger and is always connected to the inverter input. As result, all components used in the Solid-state Controls design are fully rated to carry 120% of the load on a continuous basis over a 20-year life. 2. Solid-state Controls’ Ferro resonant design has a built in capacity to supply nonlinear (crest factor) loads of up to 3:1 without oversizing. 3. Solid-state Controls’ on-line UPS design is provided with a make-before-break static switch to aid in downstream fault clearing and to protect against possible system failures. 4. Solid-state Controls’ on-line UPS system is a double conversion type, converts AC to DC and then reconverts DC back to AC. It is also insensit...

The following is an outline of some of the major problems associated with off-line (stand by) UPS designs. INPUT FREQUENCY/ VOLTAGE PASS THROUGH The off-line unit is designed to pass through the input line voltage and frequency to the load. (Note: the power passed through is non-conditioned utility power.) While this may be fine for office environments, it is not acceptable for industrial settings with periodic voltage and frequency deviations. Due to the design of off-line systems, some of the deviations will be passed directly to the loads, causing loads to drop and/or loss of data. Off-line UPS suppliers could tighten input parameters so these levels of voltage and frequency are not passed through. However, this would require the systems’ batteries to assume the load more frequently. BATTERY PICKUP If the input voltage and frequency deviate outside of acceptable limits, the systems’ batteries will automatically assume the supply of the charger/inverter. While this m...

The D-STATCOM is basically one of the custom power devices. It is nothing but a STATCOM but used at the Distribution level. The D-STATCOM is a voltage or current source inverter based custom power device connected in shunt with the power system. It is connected near the load at the distribution systems. The key component of the D-STATCOM is a power VSC that is based on high power electronics technologies. Basically, the D-STATCOM system is comprised of three main parts: a VSC, a set of coupling reactors and a controller. The basic principle of a D-STATCOM installed in a power system is the generation of a controllable ac voltage source by a voltage source converter (VSC) connected to a dc capacitor (energy storage device). The ac voltage source, in general, appears behind a transformer leakage reactance. The active and reactive power transfer between the power system and the D-STATCOM is caused by the voltage difference across this reactance. The D-STATCOM is connected in shunt w...