Photovoltaic system, direct current hybrid switching device, use and method for switching a photovoltaic string on and off

A photovoltaic system, comprising:

• at least one photovoltaic string, wherein the at least one photovoltaic string is formed by photovoltaic modules which are series-connected by a string line so as to generate a string voltage;
• a switching device which is connected in series in the string line, in order to switch on and off the at least one photovoltaic string using the switching device;
• wherein 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;
• and
• a control device to control the hybrid switch, wherein
• the control device closes the semiconductor switching device and then, after a time delay, closes the relay, when switching on the at least one photovoltaic string, and
• the control device opens the relay and then, after a time delay, opens the semiconductor switching device, when switching off the at least one photovoltaic string,
• wherein the switching device comprises the control device and a sensor device connected to the control device for measuring at least one electrical parameter on the associated photovoltaic string, wherein the control device is configured to be responsive to the at least one electrical parameter measured by the sensor device by electrically connecting the associated photovoltaic string to a current collector, said sensor device comprising:
• an input voltage sensor measuring a string side input voltage on the switching device;
• and
• an output voltage sensor measuring a current collector side output voltage on the switching device;
• and
• wherein the control device is configured to be responsive to at least one of the measured string side input voltage or the measured current collector side output voltage by electrically connecting the associated photovoltaic string to a central collection point, when release has been accorded by the user.

An electronically controlled DC hybrid switching device configured for a DC generator, for switching off at least one string of the DC generator from a current collector,

• wherein the DC hybrid 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, and
• a control device to control the hybrid switch,
• wherein the control device closes the semiconductor switching device and then, after a time delay for switching on, closes the relay, when switching on the at least one string, and the control device opens the relay and then, after a time delay for switching off, opens the semiconductor switching device, when switching off the at least one string, and
• wherein the at least one semiconductor switch of the semiconductor switching device and the relay are configured as normally open switches, and
• wherein the semiconductor switching device is maintained closed during a time period starting when the control device closes the semiconductor switching device and ending when the control device opens the semiconductor switching device after the time delay for switching off.