Transformers are fundamental components of the power distribution system and are relatively inexpensive, highly reliable, and fairly efficient. However, they possess some undesirable properties including sensitivity to harmonics, voltage drop under load, (required) protection from system disruptions and overload, protection of the system from problems arising at or beyond the transformer, environmental concerns regarding mineral oil, and performance under dc‑offset load unbalances. These disadvantages are becoming increasingly important as power quality becomes more of a concern. With the advancement of power electronics circuits and devices, the all solid‑state transformer becomes a viable option to replace the conventional copper and‑iron based transformer for a better power quality. The solid‑state switching technologies allow power conversion between different formats such as dc/dc, dc/ac, ac/dc, and ac/ac with any desired frequencies. Moreover in order to reduce the emission of greenhouse gas and replace the limited energy sources like coal, oil or uranium, the number of renewable energy sources is constantly growing. This development results in a rising number of distributed power plants, which are principally subject to substantial energy fluctuations. In order to easily connect the new energy sources to the grid and improve the power quality by harmonic filtering, voltage sag correction and highly dynamic control of the power flow new power electronic systems ‑so called Intelligent Universal / Solid‑State Transformers (SST) ‑ are required. These interconnecting devices would enable full control of magnitude and direction of real and reactive power flow and could replace not controllable, voluminous and heavy line frequency transformers. Based on such devices a smart grid comparable to the internet, where a plug and play connection of sources and loads, distributed energy uploads and downloads and energy routing for transferring energy from the producer to the consumer, is possible
BLOCK DIAGRAM
CIRCUIT DIAGRAM
BRIDGE RECTIFIER AND BUCK CONVERTER
INVERTER
HARDWARE PICTURE
BULB WITH HIGH BRIGHTNESS IS THE OUTPUT OF BUCK STAGE AND LESS BRIGHTNESS IS THE OUTPUT OF INVERTER STAGE
PROGRAM
BUCK STAGE
void setup()
{
setPwmFrequency(11, 1);
analogWrite(11,150);
}
void loop()
{
}
void setPwmFrequency(int pin, int divisor) {
byte mode;
if(pin == 5 || pin == 6 || pin == 9 || pin == 10) {
switch(divisor) {
case 1: mode = 0x01; break;
case 8: mode = 0x02; break;
case 64: mode = 0x03; break;
case 256: mode = 0x04; break;
case 1024: mode = 0x05; break;
default: return;
}
if(pin == 5 || pin == 6) {
TCCR0B = TCCR0B & 0b11111000 | mode;
} else
DESIGN AND IMPLEMENTATION OF A SOLID STATE TRANSFORMER
86
EEE Dept. NSSCE, PALAKKAD
{
TCCR1B = TCCR1B & 0b11111000 | mode;
}
}
else if(pin == 3 || pin == 11) {
switch(divisor) {
case 1: mode = 0x01; break;
case 8: mode = 0x02; break;
case 32: mode = 0x03; break;
case 64: mode = 0x04; break;
case 128: mode = 0x05; break;
case 256: mode = 0x06; break;
case 1024: mode = 0x7; break;
default: return;
}
TCCR2B = TCCR2B & 0b11111000 | mode;
}
}