抄録
In a utility interactive photovoltaic (PV) generating system, a PWM inverter is used for the connection between the PV arrays and the utility. The inverter is controlled to keep the output power at the maximum point for the PV. Although the PV power can be easily found by using the measured PV voltage and PV current, the installation of two detectors in the system is indispensable to obtain the exact PV power. In the system operation with the maximum power which is fed into the utility, the PV does not always operate at the maximum point of the PV output power because of the power losses in the system. It has been reported that the use of the measured ac voltage or ac current in the inverter output side can exclude the system losses from consideration and achieve the system operation with the maximum utility power. In this manner, however, since the ac output waveforms of the PWM inverter consist of many pulse trains, the filter circuit may be necessary for the detector to get the exact values of the ac output.
This paper proposes a calculation method of the utility power in the PV generating system by using a PWM current source inverter. In this system, the PV current only is measured and is employed for the power calculation combining the control parameter of the PWM inverter. As the proposed manner monitors the utility power instead of the PV power, the control which does not need to take the system losses into consideration can be achieved. This paper presents the calculation method of the power for the single-phase inverter-PV system and gives the experimental basic characteristics. Moreover, the application of the proposed manner to the three-phase PWM inverter-PV system is shown and the experimental results are given.
