Grid interconnection system, interconnection control device and grid interconnection method

A grid interconnection method for a power grid, comprising:

• by using a storage battery and a power conversion device for converting power from the storage battery into AC, supplying power from a commercial power supply to a load;
• supplying power from the power conversion device to the load when the commercial power supply fails;
• causing the power conversion device to synchronize a voltage phase of power supplied from the power conversion device to the load with a voltage phase of power from the commercial power supply when the commercial power supply is restored;
• starting supply of power from the commercial power supply to the load after the voltage phase of the power supplied from the power conversion device to the load is synchronized with the voltage phase of the power from the commercial power supply;
• and
• stopping the supply of power from the power conversion device to the load after the supply of power from the commercial power supply to the load is started,
• wherein, in order to synchronize the voltage phase of the power supplied from the power conversion device to the load with the voltage phase of the power from the commercial power supply, matching a frequency of the power supplied from the power conversion device to the load with a frequency of the power from the commercial power supply, and
• after the matching between the frequencies of the powers, matching a zero crossing point of the power supplied from the power conversion device to the load with a zero crossing point of the power from the commercial power supply.

A grid interconnection system for a power grid, comprising:

• a storage battery;
• a power conversion device that converts power from the storage battery into AC;
• and
• an interconnection control device that supplies power from a commercial power supply to a load and supplies power from the power conversion device to the load when the commercial power supply fails,
• wherein, when the commercial power supply is restored, the interconnection control device starts supply of power from the commercial power supply to the load, and stops supply of power from the power conversion device to the load after the supply of power from the commercial power supply to the load is started,
• wherein, when the commercial power supply is restored, the power conversion device synchronizes a voltage phase of power supplied from the power conversion device to the load with a voltage phase of power from the commercial power supply, and
• after the voltage phase of the power supplied from the power conversion device to the load is synchronized with the voltage phase of the power from the commercial power supply, the interconnection control device starts supply of power from the commercial power supply to the load,
• wherein, the power conversion device determines whether or not a voltage and a frequency of the power from the commercial power supply are within a predetermined range,
• when the voltage and the frequency are within the predetermined range, the power conversion device synchronizes the voltage phase of the power supplied from the power conversion device to the load with the voltage phase of the power from the commercial power supply, and
• when the voltage or the frequency is not within the predetermined range, the power conversion device waits for a process for phase synchronization and continues supply of power to the load.

A grid interconnection method for a power grid, comprising:

• by using a storage battery and a power conversion device for converting power from the storage battery into AC, supplying power from a commercial power supply to a load;
• supplying power from the power conversion device to the load when the commercial power supply fails;
• causing the power conversion device to synchronize a voltage phase of power supplied from the power conversion device to the load with a voltage phase of power from the commercial power supply when the commercial power supply is restored;
• starting supply of power from the commercial power supply to the load after the voltage phase of the power supplied from the power conversion device to the load is synchronized with the voltage phase of the power from the commercial power supply;
• and
• stopping the supply of power from the power conversion device to the load after the supply of power from the commercial power supply to the load is started,
• wherein, determining whether or not a voltage and a frequency of the power from the commercial power supply are within a predetermined range,
• when the voltage and the frequency are within the predetermined range, synchronizing the voltage phase of the power supplied from the power conversion device to the load with the voltage phase of the power from the commercial power supply, and
• when the voltage or the frequency is not within the predetermined range, waiting for a process for phase synchronization and continues supply of power to the load.