Method and apparatus for power inverter synchronization

A control circuit to control interconnection of a power inverter with an electrical system, the control circuit comprising:

• a regulator circuit to control an inverter voltage to match an electrical system voltage by measuring x-y phasor components of the inverter voltage and the electrical system voltage;
• a synchronization detection circuit to detect synchronization of the inverter voltage with the electrical system voltage by calculating a voltage error based on the x-y phasor components;
• and
• a contactor control circuit to command contactor closure to interconnect the power inverter with the electrical system responsive to detecting synchronization.

A power inverter including a control circuit to control interconnection of a power inverter with an electrical system, the control circuit comprising:

• a regulator circuit to control an inverter voltage to match an electrical system voltage by measuring x-y phasor components of the inverter voltage and the electrical system voltage;
• a synchronization detection circuit to detect synchronization of the inverter voltage with the electrical system voltage by calculating a voltage error based on the x-y phasor components;
• and
• a contactor control circuit to command contactor closure to interconnect the power inverter with the electrical system responsive to detecting synchronization.

A computer readable medium storing a computer program to control interconnection of a power inverter with an electrical system, the computer program comprising:

• program instructions to control an inverter voltage to match an electrical system voltage;
• program instructions to detect synchronization of the inverter voltage with the electrical system voltage based on calculating a voltage error between x-y phasor components of the inverter and electrical system voltages;
• and
• program instructions to command contactor closure to interconnect the power inverter with the electrical system responsive to detecting synchronization.

A method of connecting an initially disconnected power inverter with an electrical system, the method comprising:

• locking a phase and frequency of an inverter voltage to an electrical system voltage, and adjusting the inverter voltage to approximate the electrical system voltage;
• commanding contactor closure to connect the inverter to the electrical system responsive to determining that the inverter voltage substantially matches the electrical system voltage;
• and
• verifying contactor closure by measuring harmonic current flow between the inverter and the electrical system.

A method of controlling interconnection of a power inverter with an electrical system, the method comprising:

• controlling an inverter voltage to match an electrical system voltage based on comparing x-y phasor components of the inverter voltage with x-y phasor components of the electrical system voltage;
• detecting synchronization of the inverter voltage with the electrical system voltage;
• and
• commanding contactor closure to interconnect the power inverter with the electrical system responsive to detecting synchronization.