Solar Power Plantsare systems A power plant that utilizes energy from light the sun to produce electrical energy. But often a problem was found, where the resulting output voltage not constant. For this reason, the Buck-Boost circuit is used converter, a piece of equipment that has a converting function the varying DC input voltage becomes a voltage constant DC output. In this research, a simulation was carried out to a buck-boost converter using PID control. Design simulated with Proteus 8.9. Input voltage setting is the main objective in analyzing success simulation series created. Selection of PID control constants the right one will produce a buck-boost output voltage the converter matches the setpoint and gets a response stable output voltage. By using the trial method and error obtained that with the PID constant, namely Kp = 1.0, Ki=0.01, Kd = 0.1 and for an input voltage range of 12 volts up to 40 volts, the simulation results show that the voltage The output is relatively constant, namely 24 volts with a load test fixed and variable loads.