Abstract: The invention is an apparatus for and method of configuring a solar PV system where the output power of the system is stabilized under dynamic cloud cover conditions. The invention comprises a typical grid-tied solar photovoltaic power system which includes solar modules and a typical grid-tied DC to AC power converter and a second, semi-autonomous, bidirectional power converter coupled between the same electrical grid and storage batteries. The system also includes sensors and/or a communication link between the two power converters. The composite system acts to stabilize the amount of power into the grid by monitoring dynamic power reductions in PV power production and by supplying power from the storage batteries to the grid during a PV power dropout event, for a net smoothing of the amount of power injected into the grid over a wide range of dropout event durations.

Abstract: A DC-to-AC power converter is disclosed which provides current regulated three-phase AC outputs and very high conversion efficiencies. The converter sinks power from an external DC current source and steers that current directly into two phases of a three-phase load by using complementary semiconductor switches in disparate half-bridges of a six-pole bridge. The steering switch selection rotates every 60° to direct current into the two phases with the largest voltage differential at any given time. The remaining half-bridge acts as a high-frequency, bi-directional current source to balance the three-phase load currents. This topology and control method significantly reduces power conversion losses. Prior art converters first convert “soft” DC sources to voltage sources and then to AC current sources. The invention eliminates the need for large filter inductors and DC bus capacitors used in prior art converters. The invention is optimized for photovoltaic, utility-grid-interactive applications.

Abstract: An improved method of collecting DC power in solar photovoltaic systems is disclosed where series string overcurrent protection is provided at distributed series string terminus locations and a tap connection is made to higher current conductors carrying the combined currents of a number of series strings. A number of related string combiner methods and embodiments are disclosed.

Abstract: The invention is a photovoltaic-specific, DC load-break disconnect switch intended for applications where load-break capability is only required under abnormal operating conditions or in an emergency due to the catastrophic failure or other system components. Under normal operating conditions, the load will be switched off before a DC disconnect switch is opened. Under conditions where a load-break disconnect operation is required, an alternate path is automatically provided through a sacrificial fuse to divert current from opening contacts such that the fuse interrupts the current and not the contacts, thereby providing a substantially arcless load break. The current rating of the sacrificial fuse may be orders of magnitude less than the normal carry current. Equipment based on this invention will provide a one-time load break function that is renewable by the replacement of a fuse. The invention leverages the superior, cost-effective fault clearing capability of fuses in DC applications.

Abstract: A geo-cooled photovoltaic power conversion apparatus including a cooling system having liquid-to-earth sub-grade heat exchanger, multiple cooling loops, and a coolant reservoir which provides thermal storage for the cooling system.

Abstract: The invention is a novel photovoltaic power system that uses a number of relatively low-power DC to polyphase AC power converters distributed within the photovoltaic array field. In prior art megawatt-scale systems, typically one or two central power converters would be used for every 1 MW of solar photovoltaic array. With the present invention, 100 distributed power converters may be used per megawatt. The distributed power converters are sized to convert power from one or two series string of crystalline modules or from a greater but limited number of thin-film module strings and in both cases at the highest possible DC and therefore AC grid-tie voltages, with respect to module ratings and local safety code compliance.

Abstract: A solar photovoltaic plant is disclosed where a number of distributed DC-to-DC converters are used in conjunction with a central DC-to-AC converter. Each DC-to-DC converter is dedicated to a portion of the photovoltaic array and tracks the maximum power point voltage thereof. The DC-to-DC converters also boost the photovoltaic voltage and regulate a DC output current for transmission to the central DC-to-AC converter. Five distinct advantages are had over the prior art. First, efficiencies in intra-field power collection are greatly improved by transferring power at higher DC voltages. Second, the number of independent photovoltaic maximum power point trackers in the power plant can be increased, in a cost effective manner, to optimize the overall photovoltaic array energy harvest. Third, each DC-to-DC converter output “looks” like a current source at the input of the DC-to-AC converter and therefore can be easily paralleled.

Abstract: The invention is an apparatus and method for safely disconnecting a bipolar photovoltaic array from earth ground under normal static operating conditions. The invention senses the voltage to earth on all three terminals of a bipolar photovoltaic array and uses a set of operable contacts to selectively couple or uncouple the DC neutral point of the array (the center tap) to earth ground. When all three terminals of the bipolar array are within the rated voltage capability of the photovoltaic array the DC neutral point is allowed to float.

Abstract: An electrical contactor with high DC and AC interrupt capability is disclosed. The invention is intended for applications where load break capability is only required under abnormal operating conditions. Under overload conditions, an alternate path is automatically provided through a sacrificial fuse to divert current from opening, or open and arcing, contacts such that the fuse interrupts the fault current and not the contacts. The current rating of the sacrificial fuse may be orders of magnitude less than the normal carry current of the contactor. The contactor provides a one-time load break function that is renewable by the replacement of a fuse.

Abstract: A photovoltaic power plant design is disclosed where a two-tier DC power collection method is used in concert with specific array field geometries and equipment locations to minimize system wiring costs and/or resistive wiring losses.

Abstract: A device and method is disclosed for providing electrical grid-tied power converter anti-islanding protection, which is autonomous to the operation of the power converter. The device can protect any number of paralleled power converters and can independently detect an islanding condition. The method involves actively perturbing the electrical grid at a common point of coupling between converter and grid, observing the effect of the perturbation, comparing the perturbed and non-perturbed grid characteristics and disconnecting the converter from the grid if an island is indicated. Perturbation is accomplished by switching a reactive load or loads onto the grid or by changing a transformer tap. The invention is targeted for solar photovoltaic applications where a number of distributed power converters are used.

Abstract: A power converter design is disclosed with a novel approach to thermal management which enhances the performance and significantly reduces the cost of the converter compared to prior art power converters. The invention minimizes the heating of one power component by another within the power converter and therefore enables the power converter to work at higher power levels. Essentially, the power converter uses a heatsink having a high length to width ratio, a linear array of power components thermally coupled to the heatsink parallel to the long axis of the heatsink and a heat removal system which produces the highest cross sectional thermal flux perpendicular to said long axis. In addition, a number of ancillary thermal management techniques are used to significantly enhance the value of this basic approach.