Which device is capable of converting DC power into AC power with a specific frequency and voltage?

The device capable of converting DC power into AC power while controlling the specific frequency and voltage is the inverter. Inverters are crucial components in photovoltaic systems, as they allow the electricity generated by solar panels—typically in the form of direct current (DC)—to be transformed into alternating current (AC). This conversion is essential for compatibility with the electric grid and most household appliances, which primarily operate on AC power.

Inverters not only handle the conversion but also incorporate advanced technology to adjust the output frequency and voltage to match grid standards or the requirements of connected loads. Their ability to manage these parameters ensures a stable and efficient power supply, making them indispensable in renewable energy systems.

Other options do not fulfill the functionality of direct DC to AC conversion. Power converting utilities primarily refer to large-scale systems or organizations that manage electrical power distribution and do not perform the conversion themselves. Step-up and step-down transformers are devices used to increase or decrease AC voltage levels, but they cannot convert DC to AC or vice versa, focusing solely on manipulation of AC voltage. Therefore, the inverter is the correct answer due to its specific role in DC to AC conversion.