A solar panel cleaning system includes: an automated cleaning device for cleaning a surface of a reference cell panel; a cleaning device controller in communication with a motor of the automated cleaning device, the cleaning device controller configured to receive a signal corresponding to measurement of a current of photovoltaic system. The cleaning device controller activates the automated cleaning device to clean a surface of the reference cell panel when the received signal indicates that a measurement of the current of the photovoltaic system is to be taken.

The present disclosure relates to a DC generator that has at least one string, wherein the at least one string is formed by modules which are series-connected by a string line so as to generate a string voltage; and a switching device which is connected in series in the string line, in order to switch on and off the at least one string using the switching device. The switching device comprises a hybrid switch including a relay and a semiconductor switching device connected in parallel to the relay, wherein the semiconductor switching device includes at least one semiconductor switch. The switching device comprises a current sensor which is adapted to measure a negative current flow.

The present disclosure relates to a DC generator that has at least one string, wherein the at least one string is formed by modules which are series-connected by a string line so as to generate a string voltage; and a switching device which is connected in series in the string line, in order to switch on and off the at least one string using the switching device. The switching device comprises a hybrid switch including a relay and a semiconductor switching device connected in parallel to the relay, wherein the semiconductor switching device includes at least one semiconductor switch. The switching device comprises a current sensor which is adapted to measure a negative current flow.

A photovoltaic system, an inverter, and a direct current electric arc detection method. The system includes an inverter, a controller, and at least two converters. When detecting an electric arc, the controller controls an input current of the inverter to decrease to extinguish the arc. After the arc is extinguished, the controller controls an output voltage of at least one photovoltaic string to decrease to a first preset voltage, where the first preset voltage is less than an input voltage of the inverter when the electric arc is detected, or controls a maximum value of an output current of the at least one photovoltaic string to be a second preset current, where the second preset current is less than the input current of the inverter when the electric arc is detected. In the foregoing two recovery manners, no electric arc recurs.

In a sensor used in an energy harvesting system, electric power generated by a solar cell module is more efficiently utilized. In a sensor (100), a resistor (3) is connected in parallel with one of a first solar cell module (1a) and a second solar cell module (1b) that have mutually different current-voltage characteristics in the same illuminance environment and in series with the other one of the first solar cell module (1a) and the second solar cell module (1b). A first voltmeter (4a) measures a voltage (V1) across the first solar cell module (1a), and a second voltmeter (4b) measures a voltage (V2) across the second solar cell module (1b). A load (6) is fed with the electric power generated by the first solar cell module (1a) and the second solar cell module (1b).

In a sensor used in an energy harvesting system, electric power generated by a solar cell module is more efficiently utilized. In a sensor (100), a resistor (3) is connected in parallel with one of a first solar cell module (1a) and a second solar cell module (1b) that have mutually different current-voltage characteristics in the same illuminance environment and in series with the other one of the first solar cell module (1a) and the second solar cell module (1b). A first voltmeter (4a) measures a voltage (V1) across the first solar cell module (1a), and a second voltmeter (4b) measures a voltage (V2) across the second solar cell module (1b). A load (6) is fed with the electric power generated by the first solar cell module (1a) and the second solar cell module (1b).

A system and method for determining seasonal energy consumption with the aid of a digital computer is provided. Through a power metering energy loads for a building situated in a known location are assessed as measured over a seasonal time period. Outdoor temperatures for the building are assessed as measured over the seasonal time period through a temperature monitoring infrastructure. A digital computer comprising a processor and a memory that is adapted to store program instructions for execution by the processor is operated, the program instructions capable of: expressing each energy load as a function of the outdoor temperature measured at the same time of the seasonal time period in point-intercept form; and taking a slope of the point-intercept form as the fuel rate of energy consumption during the seasonal time period.

A system and method for determining seasonal energy consumption with the aid of a digital computer is provided. Through a power metering energy loads for a building situated in a known location are assessed as measured over a seasonal time period. Outdoor temperatures for the building are assessed as measured over the seasonal time period through a temperature monitoring infrastructure. A digital computer comprising a processor and a memory that is adapted to store program instructions for execution by the processor is operated, the program instructions capable of: expressing each energy load as a function of the outdoor temperature measured at the same time of the seasonal time period in point-intercept form; and taking a slope of the point-intercept form as the fuel rate of energy consumption during the seasonal time period.

It is disclosed an insulation impedance detection circuit and detection method of a photovoltaic inverter system. The photovoltaic inverter system includes one or more input circuits and an inverter circuit, each of the input circuit electrically coupled to the inverter circuit through a positive bus and a negative bus, with a first equivalent impedance R.sub.p between the positive bus and a protective earth point and a second equivalent impedance R.sub.n between the negative bus and the protective earth point. The detection circuit includes: a bus voltage sampling circuit coupled to the positive bus and the negative bus for generating a first bus voltage and a second bus voltage; a protective earth voltage sampling circuit coupled to the protective earth point for generating a first protective earth voltage and a second protective earth voltage; and a controller for calculating an equivalent insulation impedance.

It is disclosed an insulation impedance detection circuit and detection method of a photovoltaic inverter system. The photovoltaic inverter system includes one or more input circuits and an inverter circuit, each of the input circuit electrically coupled to the inverter circuit through a positive bus and a negative bus, with a first equivalent impedance R.sub.p between the positive bus and a protective earth point and a second equivalent impedance R.sub.n between the negative bus and the protective earth point. The detection circuit includes: a bus voltage sampling circuit coupled to the positive bus and the negative bus for generating a first bus voltage and a second bus voltage; a protective earth voltage sampling circuit coupled to the protective earth point for generating a first protective earth voltage and a second protective earth voltage; and a controller for calculating an equivalent insulation impedance.