Some power delivery systems comprise an array of power generation subassemblies whose combined output power is delivered to a power sink (a “power sink” being any device or apparatus that receives power from a power source). One example of such a system is a distributed photovoltaic power system in which each one of a plurality of solar panels is provided with a DC-AC inverter (“inverter”) that delivers power to an AC utility grid. Delivering the combined power from all of the inverters to the AC grid requires a suitable interconnection scheme. High operating efficiency, low cost, and reliable operation over long periods of time (e.g., twenty five years) may be highly valued features in such systems.
A typical way of interconnecting an array of photovoltaic inverters is illustrated in FIG. 1. As shown in FIG. 1, a distributed photovoltaic system 100 includes a plurality of photovoltaic panels 102 and associated inverters 104a-104d. Power from the photovoltaic panels 102 is delivered to the inverters 104a-104d by PV interconnects 106. Each inverter 104 may include a power input cable 108 and a power output cable 110. The power input cables 108 are terminated in input connectors 112 and the power output cables 110 are terminated in output connectors 114 that mate with the input connectors 112. Each power input connector 112 of each inverter 104 is connected to a power output connector 114 of an adjacent inverter 104 to form mated connectors 116 that may carry power between inverters.
A simplified schematic of the system 100 shown in FIG. 1 for delivering power from inverters 104a-104d to a split-phase AC grid (e.g., a 240 VAC grid comprising two 120 VAC “hot” wires 130, 132 and a neutral wire 134) is shown in FIG. 2. As illustrated in FIG. 2, each inverter 104 includes inverter circuitry 140 that receives DC power from an associated photovoltaic panel 102 and delivers AC power by means of two internal “hot” wires 130a, 132a and an internal neutral wire 134a. When the input connectors 112 and output connectors 114 of the inverters 104a-104d are coupled together to form mated connectors 116, as shown in FIGS. 1 and 3, the input cables 108 and output cables 110 are “daisy chained” (i.e., the cables are connected in series) to form a split-phase power bus 150 that receives power from each of the inverters 104 and carries the combined power to the AC grid 152 (inverters having cables that are connected in this way are referred to herein as “series-connected inverters”). An interface cable 119, connected to the output cable 110 of inverter 104a, delivers the split-phase bus 150 into junction box 120. The junction box 120 may be an electrical panel that connects to the AC grid or, as illustrated in FIGS. 1 and 2, it may provide a connection point between the wires of the split-phase bus 150 and the wiring 124 that connects to the AC grid 152 at a downstream panel (not shown).
Inverter circuitry 140 typically includes fuses and other protective devices, such as surge-protection devices, to protect the system 100 and components of the system 100 from transient electrical events and faults and to prevent failure of the entire system in the event of a failure in a single system subassembly (e.g., one of the inverters 104). One way to incorporate fuses and protective devices into a series-connected inverter 104 is illustrated in FIG. 3. As shown in FIG. 3, the inverter circuitry 140 includes a fuse 146 in series with each hot wire 130a, 132a and surge protection devices 154a, 154b, 154c (e.g., a metal-oxide varistor (“MOV”)) connected between each pair of wires 130a, 132a, 134a. 
Regulatory and safety requirements may also require that each inverter 140 be connected to earth ground. One way to provide an earth ground to each inverter 140, illustrated in FIGS. 1 and 2, is to provide a ground wire 122 that is connected (e.g., by means of a screw) to each series-connected inverter.
USPTO Backgrounds
USPTO Backgrounds