Abstract: An apparatus and method of control for converting DC (direct current) power from a solar photovoltaic source to AC (alternating current) power. A novel DC-to-AC power converter topology and a novel control method are disclosed. This combination of topology and control are very well suited for photovoltaic microinverter applications. Also, a novel variant of this control method is illustrated with a number of known photovoltaic DC-to-AC power converter topologies. The primary function of both control methods is to seek the maximum power point (MPP) of the photovoltaic source with novel, iterative, perturb and observe control algorithms. The control portion of this invention discloses two related control methods, both an improvement over prior art by having greatly improved stability, dynamic response and accuracy.

Abstract: An apparatus and method of control for converting DC (direct current) power from a solar photovoltaic source to AC (alternating current) power. A novel DC-to-AC power converter topology and a novel control method are disclosed. This combination of topology and control are very well suited for photovoltaic microinverter applications. Also, a novel variant of this control method is illustrated with a number of known photovoltaic DC-to-AC power converter topologies. The primary function of both control methods is to seek the maximum power point (MPP) of the photovoltaic source with novel, iterative, perturb and observe control algorithms. The control portion of this invention discloses two related control methods, both an improvement over prior art by having greatly improved stability, dynamic response and accuracy.

Abstract: A controlled switching system for converting the output of several photovoltaic solar arrays into a polyphase alternating electric current. Each array is utilized 100% of the time, and at any particular instant only one array or no array is feeding a particular phase. The specific line to which an array is connected is altered in a cyclic manner by the switching system to synthesize the polyphase current. Energy is not stored in the switching system, but instead is made available as polyphase electric current as soon as it is generated by the photovoltaic arrays. Each phase approximates a sine wave to an extent that is limited by the number of arrays. For the closest approximation, the arrays must be configured to have prescribed voltages and currents. Alternatively, a single array may be partitioned electrically in such a way that the desired voltages and currents are attained.

Abstract: A controlled switching system for converting the output of several photovoltaic solar arrays into a polyphase alternating electric current. Each array is utilized 100% of the time, and at any particular instant only one array or no array is feeding a particular phase. The specific line to which an array is connected is altered in a cyclic manner by the switching system to synthesize the polyphase current. Energy is not stored in the switching system, but instead is made available as polyphase electric current as soon as it is generated by the photovoltaic arrays. Each phase approximates a sine wave to an extent that is limited by the number of arrays. For the closest approximation, the arrays must be configured to have prescribed voltages and currents. Alternatively, a single array may be partitioned electrically in such a way that the desired voltages and currents are attained.

Abstract: The faulted cable is connected in a loop with a spark gap at one end. Voltage is applied until the spark gap breaks down and the arrival time of the resultant forward wave is measured at both ends of the loop to measure total cable length. Next, the spark gap is opened and the voltage is built up until the fault breaks down. The time of receipt of the wavefront at the two ends of the loop is measured to determine the location of the fault. The apparatus comprises the power supply equipment, the spark gap and the time measuring equipment with its voltage divider and clamp.

Abstract: Open conductors in an electric power distribution system are detected by sensing the abrupt change in balance of transformer magnetizing current among phases, particularly the third harmonic of the power system frequency. The current is sensed in each phase and the absolute magnitude of the third harmonic current is compared among the phases. When imbalance exceeds a predetermined value, a signal is produced.

Abstract: The ac transmission system is protected by circuit breaker apparatus capable of responding to fault current levels exceeding a predetermined critical fault level, but less than the maximum fault current. The fault current levels exceeding the critical level are detected by comparison of actual line current to a simulation of the critical level of fault current for one of a plurality of phases 01, 02, 03. Reference signals in quadrature with the three line voltages are continuously fed to differential amplifiers having both inputs connected in parallel until a potential fault is detected when one input is disconnected and clamped at the potential it had at the time of disconnect. The resulting output of the differential amplifiers accurately simulates the time-varying current of a system fault. The simulated signals are compared to actual line current to determine in less than one cycle if a fault is occurring and to order the appropriate breaker action.

Abstract: A high voltage system with self-test circuitry which senses the amount of current in a high voltage line and communicates this information by means of fiber optics to control electronics which in turn communicate said information to actuator means which compensate for excessive amounts of current or notify the operator of a fault. Also the system provides a continuous and automatic self test of the communication lines by use of a clocked parity checking system.