Inverter control apparatus

1. An inverter control apparatus which is configured to control an inverter interconnected to an alternating-current power system, a capacitor being provided on an alternating-current side of the inverter, the apparatus comprising:

a system voltage detector configured to detect a system voltage of the alternating-current power system;

a differentiation circuit configured to calculate a differential value of the system voltage detected by the system voltage detector;

a correction current instruction value calculator configured to calculate a correction current instruction value for correcting a current instruction value set for an output current of the inverter, based on the differential value of the system voltage calculated by the differentiation circuit;

an adder configured to receive the correction current instruction value generated from the correction current instruction value calculator that receives the detected system voltage from the system voltage detector, add the correction current instruction value to a preset current instruction value, and output a current instruction value; and

a controller configured to control the inverter based on the current instruction value.

2. The inverter control apparatus of claim 1 , wherein the correction current instruction value calculator calculates the correction current instruction value based on a capacitance of the capacitor.

3. A distributed power supply system comprising:

an inverter interconnected to an alternating-current power system;

a capacitor provided on an alternating-current side of the inverter;

a system voltage detector configured to detect a system voltage of the alternating-current power system;

a differentiation circuit configured to calculate a differential value of the system voltage detected by the system voltage detector;

a correction current instruction value calculator configured to calculate a correction current instruction value for correcting a current instruction value set for an output current of the inverter, based on the differential value of the system voltage calculated by the differentiation circuit;

an adder configured to receive the correction current instruction value generated from the correction current instruction value calculator that receives the detected system voltage from the system voltage detector, add the correction current instruction value to a preset current instruction value, and output a current instruction value; and

a controller configured to control the inverter based on the current instruction value.

4. The distributed power supply system of claim 3 , wherein the correction current instruction value calculator calculates the correction current instruction value based on a capacitance of the capacitor.

5. A control method of controlling an inverter which is interconnected to an alternating-current power system, a capacitor being provided on an alternating-current side the inverter, the control method comprising:

detecting, by a system voltage detector, a system voltage of the alternating-current power system;

calculating a differential value of the detected system voltage;

calculating, by a correction current instruction value calculator, a correction current instruction value for correcting a current instruction value set for an output current of the inverter, based on the calculated differential value;

receiving, by an adder, the correction current instruction value calculated from the correction current instruction value calculator that receives the detected system voltage from the system voltage detector, adding the correction current instruction value to a preset current instruction value, and outputting a current instruction value; and

controlling the inverter based on the corrected current instruction value.

6. The control method of claim 5 , wherein the correction current instruction value is calculated based on a capacitance of the capacitor.

7. The inverter control apparatus of claim 1 , wherein the correction current instruction value calculator calculates the correction current instruction value in such a manner that the larger the differential value, the more strongly a change in the output current of the inverter is restrained.

8. The distributed power supply system of claim 3 , wherein the correction current instruction value calculator calculates the correction current instruction value in such a manner that the larger the differential value, the more strongly a change in the output current of the inverter is restrained.

9. The control method of claim 5 , wherein the correction current instruction value is calculated in such a manner that the larger the differential value, the more strongly a change in the output current of the inverter is restrained.