The design of a 1 kW buck-boost chopper with proportional-integral (PI) control is presented and discussed in this paper. The buck-boost chopper was proposed as a photovoltaic power converter to achieve a stable dc output voltage. In the design, the circuits employed IGBT power switch to function the PWM control signals to adjust the chopper’s output voltage. The circuits were tested to investigate the output waveform set at 24 V from various dc input voltage values. The chopper circuits were connected to ten solar PV modules with a total capacity of 1 kW. Simulation test results confirmed that the system was able to output 24 dc voltage with output current about 41 A. Furthermore, a prototype of the buck-boost chopper was set up and tested. The circuits worked well to output a stable 24 V DC voltage from PV output voltage varied 15 V-32 V.

No abstract

Protection using Over Current Relays (OCR) with cascade coordination patterns is commonly used in 20 kV primary distribution networks to protect transformers from phase to phase fault currents. To anticipate a large fault current, the OCR feeder is equipped with an instant time setting. The problem occurs when the OCR feeder or PMT feeder fails to work then the transformer will be at risk because it is burdened with the fault current for a relatively long time. This study will discuss the use of a non-cascade pattern for the coordination of OCR feeders and incoming OCR in a primary distribution system supplied by a 60 MVA transformer, 150/20 kV from the substation by the calculation method. OCR feeders use very inverse (VI) characteristics and OCR inverses use standard inverse (SI) characteristics. A large feeder fault current is obtained by determining the 3 phase fault current upstream of the feeder as 7 x the nominal current (In) of the transformer. The result is that when the PMT feeder fails to work, the incoming OCR cascade coordination pattern will work with a time of 1.05 seconds. Meanwhile, if we use a non-cascade pattern the incoming OCR will work in the time setting of 0.3 seconds. Work time difference of (1.05 - 0.3 = 0.75 s) shows an increase in protection reliability and reduces the risk of damage to the transformer.