Abstract: An inverter unit converts power from a solar battery into AC power and interconnects the AC power with a utility power supply. A control circuit manages the time during which the inverter unit stops. If the time is equal to or longer than a predetermined time, it is determined that one day has passed. Data for one day stored in a memory is accordingly cleared and data is newly stored in the memory.

Abstract: An inverter unit converts power from a solar battery into AC power and interconnects the AC power with a utility power supply. A control circuit manages the time during which the inverter unit stops. If the time is equal to or longer than a predetermined time, it is determined that one day has passed. Data for one day stored in a memory is accordingly cleared and data is newly stored in the memory.

Abstract: A solar generation system includes a standard solar cell string and a substandard solar cell string. A DC voltage output from the substandard solar cell string is boosted by a booster unit to the level of the DC voltage output from the standard solar cell string, and the DC voltage from the standard solar cell string and the boosted DC voltage are applied to a DC/AC inverter, whereby an AC power is obtained, which is supplied to a utility power supply.

Abstract: A solar generation system includes a standard solar cell string and a substandard solar cell string. A DC voltage output from the substandard solar cell string is boosted by a booster unit to the level of the DC voltage output from the standard solar cell string, and the DC voltage from the standard solar cell string and the boosted DC voltage are applied to a DC/AC inverter, whereby an AC power is obtained, which is supplied to a utility power supply.

Abstract: There is provided an inverter apparatus islanding operation detecting method capable of surely detecting an islanding operation with a simple construction. A distortion for causing a variation in an output frequency of an inverter apparatus in an islanding operation stage is applied to an inverter output waveform. With this arrangement, even when the inverter apparatus is disconnected from an AC power system in a state in which a power factor of a load impedance is proximate to one, a frequency variation is generated in an inverter output, thereby ensuring detection of the islanding operation.

Abstract: An inverter-control device includes a subtractor for detecting an error between a waveform of a reference current signal generated in synchronization with a waveform of an inverter output current signal and the inverter output current signal, a delay portion for delaying by a prescribed time period a signal obtained by amplifying and removing high frequency component by filtering the error, an error waveform integrating portion for integrating the delayed signal f' output from delay portion, a proportional control portion for amplifying the error, and an adding portion for adding an error amplified signal output from the proportional control portion and an inverter driving waveform pattern output from the error waveform integrating portion.

Abstract: A pulse width of a pulse train signal used for PWM (pulse width modulation) control is monitored. When a variation of the pulse width substantially disappears within a specified time, it is determined that an operating point on an output characteristic curve of a photovoltaic array is located on the open-circuit voltage side of a maximum power point. When the variation of the pulse width does not disappear after the elapse of the specified time, it is determined that the operating point is located on the short-circuit current side of the maximum power point. Based on the determination result, the inverter control is performed such that the operating point follows the maximum power point.

Abstract: In a method of controlling an inverter for adjusting a periodic inverter output waveform to a desired periodic waveform, an error waveform pattern between an inverter output waveform of the present prescribed period and a desired periodic waveform generated in synchronization with the prescribed period is formed, and the error waveform pattern is added to an inverter driving waveform pattern in the last prescribed period, whereby an inverter driving waveform pattern is updated.

Abstract: A pulse train pulse-width modulated by PWM control using a sine-wave signal and a carrier signal is inverted alternately in positive-negative polarity. With a high-frequency AC signal obtained by the inversion, a primary side of a transformer for insulating input and output from each other is excited. This arrangement makes it possible to employ a high-frequency transformer which has a capacity ratio of about 1/30 and a weight ratio of about 1/20 relative to a commercial-frequency transformer, instead of using it. Thus, an inverter apparatus can be reduced in size and weight as compared with the system using the power-frequency transformer. A sine-wave AC waveform with substantially less distortion similar to the waveform output by the conventional PWM control can be obtained with a simple construction.

Abstract: This electric power supply system includes an air conditioner serving as load, a solar photovoltaic cell for supplying power to the air conditioner, and a system power control circuit and further including a commercial power source for use in combination with the solar photovoltaic cell for supplying additional power when insufficient, power is supplied from the solar photovoltaic cell to the air conditioner. In an operation state of the air conditioner, the system power control circuit operates to regulate an operating point of the solar photovoltaic cell and variably regulate the supplied power from the solar photovoltaic cell while comparing required power of the air conditioner with the supplied power from the solar photovoltaic cell.