Electric power system

An electric power system comprising:

• an uninterruptible power supply including an AC switch provided between a commercial power supply and an output part, a secondary battery, and an inverter provided between the AC switch and secondary battery;
• an important load connected to the output part;
• a distributed power supply connected to the output part;
• total load power consumption detection means for detecting the power consumption of all loads including the important load;
• charge/discharge power detection means for detecting charge/discharge power of the secondary battery;
• output power detection means for detecting the output power of the distributed power supply;
• important load power consumption detection means for detecting the power consumption of the important load;
• and
• a controller that inputs thereto detection values from the total load power consumption detection means, charge/discharge power detection means, output power detection means, and important load power consumption detection means and outputs a control command value for controlling the secondary battery,
• wherein the controller adds the detection values from the total load power consumption detection means and the charge/discharge power detection means, passes the added detection values into a band-pass filter outputting a filtered signal, and inputs the filtered signal into a limiter limiting the inputted signal by maximum and minimum limit values for power flow in the AC switch, and
• wherein the controller determines the control command value for operating the secondary battery based on the equation:
• (command value WACSWref)−(the detection value of the output power detection means)+(the detection value of the important load power consumption detection means), the command value W ACSWref being the output from the limiter.