Power conversion device

1. A power conversion device comprising:

an inverter to convert a power output from a distributed power source into an AC power and output the AC power to an AC system; and

a controller to control the inverter,

the controller including

virtual synchronous generator control circuitry to impart a transient characteristic of a synchronous generator to the inverter,

control parameter generating circuitry to generate a control parameter for controlling the virtual synchronous generator control circuitry,

inverter voltage control circuitry to control the inverter as a voltage source, based on AC system voltage information input from the virtual synchronous generator control circuitry, and

communication circuitry to receive, from a management device that manages the distributed power source, a power target value of the distributed power source and information necessary for generating the control parameter,

wherein the control parameter generating circuitry generates at least one of a speed adjustment rate and a damping coefficient to be used in the virtual synchronous generator control circuitry, based on the power target value and the information necessary for generating the control parameter received by the communication circuitry.

2. The power conversion device according to claim 1 , wherein

the virtual synchronous generator control circuitry includes

governor control circuitry to mimic a governor function of the synchronous generator, and

mass system computing circuitry to mimic a swing equation of the synchronous generator,

the control parameter for controlling the governor control circuitry includes a governor time constant to determine response performance of the synchronous generator, and the speed adjustment rate, and

the control parameter for controlling the mass system computing circuitry includes an inertia constant to mimic inertia of a mechanical rotor, and the damping coefficient to apply a damping force to the mechanical rotor.

3. The power conversion device according to claim 1 , further comprising a voltmeter to measure an AC system voltage of the AC system,

wherein the inverter voltage control circuitry generates an AC voltage target value based on the AC system voltage information input from the virtual synchronous generator control circuitry and controls the inverter as the voltage source based on the generated AC voltage target value and a measurement value of the voltmeter.

4. The power conversion device according to claim 2 , further comprising a voltmeter to measure an AC system voltage of the AC system,

wherein the inverter voltage control circuitry generates an AC voltage target value based on the AC system voltage information input from the virtual synchronous generator control circuitry and controls the inverter as the voltage source based on the generated AC voltage target value and a measurement value of the voltmeter.

5. The power conversion device according to claim 2 , further comprising:

a voltmeter to measure an AC system voltage of the AC system;

an ammeter to measure an AC current of the AC system;

effective power calculating circuitry to calculate an AC effective power based on measurement values of the voltmeter and the ammeter; and

an AC frequency detector to detect a frequency and a zero cross point or a phase of the AC system voltage, based on a measurement value of the voltmeter, wherein

the governor control circuitry calculates an offset value to be added to the power target value, based on a reference frequency of the AC system voltage and a frequency of the AC system voltage detected by the AC frequency detector, and outputs a result of the calculation to the mass system computing circuitry, and

the mass system computing circuitry generates a frequency and a phase of the AC system voltage to be output as the AC system voltage information to the inverter voltage control circuitry, based on a result of addition of the power target value and the offset value, and the AC effective power.

6. The power conversion device according to claim 4 , further comprising:

an ammeter to measure an AC current of the AC system;

effective power calculating circuitry to calculate an AC effective power based on measurement values of the voltmeter and the ammeter; and

an AC frequency detector to detect a frequency and a zero cross point or a phase of the AC system voltage, based on a measurement value of the voltmeter, wherein

the governor control circuitry calculates an offset value to be added to the power target value, based on a reference frequency of the AC system voltage and a frequency of the AC system voltage detected by the AC frequency detector, and outputs a result of the calculation to the mass system computing circuitry, and

the mass system computing circuitry generates a frequency and a phase of the AC system voltage to be output as the AC system voltage information to the inverter voltage control circuitry, based on a result of addition of the power target value and the offset value, and the AC effective power.

7. The power conversion device according to claim 5 , wherein

the inverter voltage control circuitry includes current limiting circuitry to limit an AC current output by the inverter, and

the current limiting circuitry imposes a limit on an AC current output by the inverter when a measurement value of the ammeter deviates from a preset current range.

8. The power conversion device according to claim 1 , wherein the control parameter generating circuitry generates the control parameter, based on a capacity of the inverter, prescribed information for connecting to the AC system, and the power target value and the information necessary for generating the control parameter received by the communication circuitry.

9. The power conversion device according to claim 8 , wherein

the control parameter generating circuitry:

generates a reference ΔF/ΔP characteristic indicating a relation between a differential frequency and a differential power when a multiplication value obtained by multiplying a capacity of the inverter by a predetermined ratio is set as the power target value, the differential frequency being a deviation of a system frequency from a reference frequency of an AC system voltage of the AC system, the differential power being a deviation of an output power of the inverter from the power target value;

generates a ΔF/ΔP characteristic for controlling the inverter, based on the generated reference ΔF/ΔP characteristic and the power target value given from the management device; and

generates the control parameter using the generated ΔF/ΔP characteristic.

10. The power conversion device according to claim 1 , wherein

the information necessary for generating the control parameter includes a reference ΔF/ΔP characteristic or information necessary for generating the reference ΔF/ΔP characteristic, or a ΔF/ΔP characteristic or information necessary for generating the ΔF/ΔP characteristic,

the reference ΔF/ΔP characteristic indicates a relation between a differential frequency and a differential power when a multiplication value obtained by multiplying a capacity of the inverter by a predetermined ratio is set as the power target value, the differential frequency being a deviation of a system frequency from a reference frequency of an AC system voltage of the AC system, the differential power being a deviation of an output power of the inverter from the power target value,

the ΔF/ΔP characteristic indicates a relation between a differential frequency and a differential power, the differential frequency being a deviation of a system frequency from the reference frequency, the differential power being a deviation of an output power of the inverter from the power target value given from the management device, and

the control parameter generating circuitry generates the control parameter, based on the power target value and the information necessary for generating the control parameter given from the management device, and a capacity of the inverter.

11. The power conversion device according to claim 9 , wherein

the control parameter generating circuitry:

calculates the differential power of an output power of the inverter from the power target value given from the management device;

calculates the differential frequency, based on the ΔF/ΔP characteristic or the information necessary for generating the ΔF/ΔP characteristic; and

generates the control parameter, based on the calculated differential power and differential frequency.

12. The power conversion device according to claim 10 , wherein

the control parameter generating circuitry:

calculates the differential power of an output power of the inverter from the power target value given from the management device;

calculates the differential frequency, based on the ΔF/ΔP characteristic or the information necessary for generating the ΔF/ΔP characteristic; and

generates the control parameter, based on the calculated differential power and differential frequency.