A method of fabricating a four junction solar cell having an upper first solar subcell composed of a semiconductor material including aluminum and having a first band gap; a second solar subcell adjacent to said first solar subcell and composed of a semiconductor material having a second band gap smaller than the first band gap and being lattice matched with the upper first solar subcell; a third solar subcell adjacent to said second solar subcell and composed of a semiconductor material having a third band gap smaller than the second band gap and being lattice matched with the second solar subcell; and a fourth solar subcell adjacent to and lattice matched with said third solar subcell and composed of a semiconductor material having a fourth band gap smaller than the third band gap; wherein the fourth subcell has a direct bandgap of greater than 0.75 eV.

Various implementations described herein are directed to a methods and apparatuses for disconnecting, by a device, elements at certain parts of an electrical system. The method may include measuring operational parameters at certain locations within the system and/or receiving messages from control devices indicating a potentially unsafe condition, disconnecting and/or short-circuiting system elements in response, and reconnection the system elements when it is safe to do so. Certain embodiments relate to methods and apparatuses for providing operational power to safety switches during different modes of system operation.

Various implementations described herein are directed to a methods and apparatuses for disconnecting, by a device, elements at certain parts of an electrical system. The method may include measuring operational parameters at certain locations within the system and/or receiving messages from control devices indicating a potentially unsafe condition, disconnecting and/or short-circuiting system elements in response, and reconnection the system elements when it is safe to do so. Certain embodiments relate to methods and apparatuses for providing operational power to safety switches during different modes of system operation.

Tracking of health and resilience of physical equipment and related systems are disclosed. A system includes physical equipment and one or more processors. The physical equipment includes one or more assets. The one or more processors are configured to determine a resilience metric for the physical equipment. The resilience metric includes a real power component and a reactive power component based, at least in part, on an aggregation of real components and reactive components of adaptive capacities of the one or more assets. A cyber-physical system includes physical equipment, network equipment configured to enable the physical equipment to communicate over one or more networks, a physical anomaly detection system (ADS) configured to detect anomalies in operation of the physical equipment and provide a physical component of a cyber-physical metric, and a cyber ADS configured to detect anomalies in network communications over the one or more networks.

Tracking of health and resilience of physical equipment and related systems are disclosed. A system includes physical equipment and one or more processors. The physical equipment includes one or more assets. The one or more processors are configured to determine a resilience metric for the physical equipment. The resilience metric includes a real power component and a reactive power component based, at least in part, on an aggregation of real components and reactive components of adaptive capacities of the one or more assets. A cyber-physical system includes physical equipment, network equipment configured to enable the physical equipment to communicate over one or more networks, a physical anomaly detection system (ADS) configured to detect anomalies in operation of the physical equipment and provide a physical component of a cyber-physical metric, and a cyber ADS configured to detect anomalies in network communications over the one or more networks.

A method for detecting a potential-induced degradation (PID) of PV modules of a PV installation includes operating a PV generator at a maximum power point (MPP), at a first generator voltage (U.sub.1) and first generator current (I.sub.1), and at a second generator voltage (U.sub.2) and second generator current (I.sub.2), where a first power (P.sub.1) at the first generator voltage (U.sub.1) is in a predefined first ratio V.sub.1=P.sub.1/P.sub.MPP and V.sub.1≤1, with the power (P.sub.MPP) at the maximum power point (MPP) of the PV generator, and where a second power (P.sub.2) at the second generator voltage (U.sub.2) is in a predefined second ratio V.sub.2=P.sub.2/P.sub.1 and V.sub.2<1, with the first power (P.sub.1) of the PV generator, and where a quantity Y that characterizes a progress of the potential-induced degradation (PID) is determined from the values of the voltages (U.sub.1, U.sub.2) and/or the currents (I.sub.1, I.sub.2).

A method for detecting a potential-induced degradation (PID) of PV modules of a PV installation includes operating a PV generator at a maximum power point (MPP), at a first generator voltage (U.sub.1) and first generator current (I.sub.1), and at a second generator voltage (U.sub.2) and second generator current (I.sub.2), where a first power (P.sub.1) at the first generator voltage (U.sub.1) is in a predefined first ratio V.sub.1=P.sub.1/P.sub.MPP and V.sub.1≤1, with the power (P.sub.MPP) at the maximum power point (MPP) of the PV generator, and where a second power (P.sub.2) at the second generator voltage (U.sub.2) is in a predefined second ratio V.sub.2=P.sub.2/P.sub.1 and V.sub.2<1, with the first power (P.sub.1) of the PV generator, and where a quantity Y that characterizes a progress of the potential-induced degradation (PID) is determined from the values of the voltages (U.sub.1, U.sub.2) and/or the currents (I.sub.1, I.sub.2).

A photovoltaic power generation system and a method and a device for detecting an earth fault of a photovoltaic string. The controller obtains a terminal voltage of each photovoltaic string before voltage disturbance, where the terminal voltage is a voltage to earth of a positive electrode or negative electrode of the photovoltaic string; performs voltage disturbance on each photovoltaic string and obtains a terminal voltage of each photovoltaic string after the voltage disturbance; determines a photovoltaic string with an earth fault based on the terminal voltage of each photovoltaic string before and after the voltage disturbance; obtains a photovoltaic panel with an earth fault by using the terminal voltage and an output voltage of the photovoltaic string before the voltage disturbance, or obtains a photovoltaic panel with an earth fault by using the terminal voltage and an output voltage of the photovoltaic string after the voltage disturbance.

A photovoltaic power generation system and a method and a device for detecting an earth fault of a photovoltaic string. The controller obtains a terminal voltage of each photovoltaic string before voltage disturbance, where the terminal voltage is a voltage to earth of a positive electrode or negative electrode of the photovoltaic string; performs voltage disturbance on each photovoltaic string and obtains a terminal voltage of each photovoltaic string after the voltage disturbance; determines a photovoltaic string with an earth fault based on the terminal voltage of each photovoltaic string before and after the voltage disturbance; obtains a photovoltaic panel with an earth fault by using the terminal voltage and an output voltage of the photovoltaic string before the voltage disturbance, or obtains a photovoltaic panel with an earth fault by using the terminal voltage and an output voltage of the photovoltaic string after the voltage disturbance.

An arc detection device includes: a current detector that includes a magnetic core penetrated by first and second paths and each connecting a DC power source and a device, and detects a current flowing through each of the first and second paths and in accordance with a magnetic field generated at the magnetic core; a low impedance circuit having a lower impedance than the DC power source and the device, the low impedance circuit being connected to the first path and the second path to cause a high frequency component to bypass one of the first path or the second path; and an arc determiner that determines an occurrence of an arc based on a current detected by the current detector. In the magnetic core, a direct current flows through the first path in a direction opposite to a direction in which a direct current flows through the second path.