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: The invention is a method of tracking the overall maximum power point of a grounded bipolar photovoltaic array by tracking and regulating the voltage of the weaker of the two monopolar subarrays at any instant in time. The transfer between subarrays being tracked for the maximum power point is seamless when the voltage of one subarray becomes lower than the other. This tracking method insures stable operation and maximum power transfer under all balanced and unbalanced PV array conditions. This tracking algorithm would typically be part of a larger digital power converter control system.

Abstract: The invention is an electrical power system for powering quasi-remote loads wherein local electric utility power is stepped up in voltage and transmitted to a remote battery bank via a low cost, two-conductor, direct burial cable. The system is configured such that current in is this cable is relatively low and constant. The battery bank is used to buffer the low power feed from the electric utility source and the high power, high crest factor remote loads. An inverter, like the type used with off-grid solar power systems, converts the DC battery power to AC power to supply the remote loads.

Abstract: The invention is a bipolar solar photovoltaic to three-phase AC power converter with a novel non-isolated power conversion topology which allows multiple power converter outputs to be directly paralleled without the need for synchronized switching or galvanic isolation. The invention directly supports a new approach to solar photovoltaic system design wherein a large number of distributed lower power converters are used in lieu of one large central inverter.

Abstract: The invention is an electrical power conversion topology. The preferred embodiment is as a three-phase, on-line Uninterruptible Power Supply (UPS). The desired AC output voltage waveform is formed on each output line or phase of the UPS, using pulse modulation techniques and a smoothing output filter inductor. A semiconductor switching matrix is used to switch the power converter side of each output filter inductor between three voltage potentials, a positive battery potential, a negative battery potential and a third intermediate and varying AC potential synchronized with the desired output voltage. The invention potentially provides the same performance as that of a multi-level inverter topology approaching an infinite number of DC levels.

Abstract: The invention is a high efficiency single-phase or poly-phase DC-to-AC power converter apparatus and power conversion method which includes a line filter inductor or line filter inductors to integrate or filter pulse modulated waveforms into substantially sinusoidal waveforms wherein (i) the line filter inductor or inductors have inductance values that swing substantially from zero current to peak rated current and (ii) a pulse width modulation technique is used that varies both pulse width modulation duty cycles and periods as a function of the predicted instantaneous line filter inductance and the predicted di/dt across the line filter inductor or inductors in order to minimize power converter switching losses while maintaining AC power quality. With the invention, substantial CEC power conversion efficiency enhancements should be achievable and with an overall reduction in power converter parts cost.

Abstract: The invention is a high efficiency single-phase or poly-phase DC-to-AC power converter apparatus and power conversion method which includes a line filter inductor or line filter inductors to integrate or filter pulse modulated waveforms into substantially sinusoidal waveforms wherein (i) the line filter inductor or inductors have inductance values that swing substantially from zero current to peak rated current and (ii) a pulse width modulation technique is used that varies both pulse width modulation duty cycles and periods as a function of the predicted instantaneous line filter inductance and the predicted di/dt across the line filter inductor or inductors in order to minimize power converter switching losses while maintaining AC power quality. With the invention, substantial CEC power conversion efficiency enhancements should be achievable and with an overall reduction in power converter parts cost.

Abstract: The invention is a method of tracking the overall maximum power point of a grounded bipolar photovoltaic array by tracking and regulating the voltage of the weaker of the two monopolar subarrays at any instant in time. The transfer between subarrays being tracked for the maximum power point is seamless when the voltage of one subarray becomes lower than the other. This tracking method insures stable operation and maximum power transfer under all balanced and unbalanced PV array conditions. This tracking algorithm would typically be part of a larger digital power converter control system.

Abstract: The invention is an electrical power system for powering quasi-remote loads wherein local electric utility power is stepped up in voltage and transmitted to a remote battery bank via a low cost, two-conductor, direct burial cable. The system is configured such that current in is this cable is relatively low and constant. The battery bank is used to buffer the low power feed from the electric utility source and the high power, high crest factor remote loads. An inverter, like the type used with off-grid solar power systems, converts the DC battery power to AC power to supply the remote loads.

Abstract: The invention is a bipolar solar photovoltaic to three-phase AC power converter with a novel non-isolated power conversion topology which allows multiple power converter outputs to be directly paralleled without the need for synchronized switching or galvanic isolation. The invention directly supports a new approach to solar photovoltaic system design wherein a large number of distributed lower power converters are used in lieu of one large central inverter.

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: The invention is a liquid cooled photovoltaic power converter with a liquid-to-earth heat exchanger. With the invention, removal of heat from primary power converter heat sources is accomplished without cooling fans or ambient air exchange in order to eliminate associated particulate contamination and maintenance issues.

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 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: 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.