Dead-zone DC converter

Abstract

A photovoltaic power system for supplying power to an electrical grid is provided in which a plurality of photovoltaic panels are each configured for generating a DC power signal. A plurality of DC-DC power converters connected to the photovoltaic panel are provided for converting a DC power signal into a dead-zone DC signal having a rectified sinusoidal waveform with repetitive dead-zone periods, which reduces the risk of arcing during power transfer. An electrical network interface is used to convert the dead-zone DC signal received from the plurality of DC-DC power converters into an AC power signal.

Description

[0001] This application is a divisional application of the patent application with the application number 201780082327.X, the application date of November 7, 2017, and the invention title of "Dead Zone DC Converter". Technical Field

[0002] The present invention generally relates to power distribution systems and methods, and in certain embodiments, to photovoltaic power distribution systems and methods. Background Art

[0003] Due to the nature of direct current (DC) transmission, DC power transmission and distribution systems are highly susceptible to arc faults. To prevent the potential hazards of arc faults, including fire risk and electric shock risk, conventional DC systems require large and expensive protection devices, such as DC-rated circuit breakers. Personnel working on DC systems must also wear a large amount of personal safety equipment for protection.

[0004] Figure 1A An example standard AC waveform 101 is shown. As shown, the waveform 101 periodically crosses a zero voltage indicated as the AC voltage waveform zero crossing 102. The zero voltage allows any arc that may occur in an AC power transmission or distribution system to easily extinguish during the zero crossing and allows the circuit breaker to easily open the circuit. In contrast, Figure 1B A standard DC waveform 103 is shown. The standard DC waveform 103 remains at a constant level and does not include a periodic zero voltage level or zero crossing. Due to the absence of a zero crossing, a DC-rated circuit breaker with more complex arc extinguishing and opening methods is required to safely transmit the waveform 103.

[0005] As an example of a DC power source, photovoltaic (PV) cells are currently used to collect solar energy for use in industrial, commercial, residential, and / or other power generation, transmission, and distribution environments. However, conventionally, the DC power generated by PV cells is immediately converted to alternating current (AC) by an inverter before being distributed to the power grid or electrical devices. Although this avoids some of the safety issues associated with DC transmission and the need for DC-rated circuit breakers, using an inverter in this capacity also represents a cost source and a fundamental inefficiency in these systems. In particular, this increases the cost per watt of the entire system and reduces the attractiveness of the system as a renewable energy source. Additionally, many electrical devices, such as portable electronic devices and lighting systems, must convert the AC power received from an outlet back to usable DC power, further reducing the efficiency of AC transmission from a DC source.

[0006] Accordingly, there has been a long-felt need in the art to be able to use DC power sources more economically, efficiently, and reliably and to do so safely. Summary of the Invention

[0007] Various embodiments of the present invention relate to a photovoltaic power system for powering an electrical grid. According to various embodiments, the system includes: (i) a solar cell array including a plurality of photovoltaic panels, each photovoltaic panel being configured to generate a DC power signal; (ii) a plurality of DC-DC power converters, each DC-DC power converter being connected to at least one of the photovoltaic panels and being configured to convert the DC power signal generated by its corresponding photovoltaic panel into a dead-band DC signal, where the dead-band DC signal includes a rectified sinusoidal waveform having a repeatedly occurring dead-band period with zero voltage; and (iii) an electrical network interface connected to the plurality of DC-DC power converters and being configured to convert the dead-band DC signals received from the plurality of DC-DC power converters into an AC power signal, where the electrical network interface is further connected to the electrical grid and is configured to supply the AC power signal to the electrical grid.

[0008] In some embodiments, each of the plurality of DC-DC power converters includes a pair of switching transistors configured to convert the DC power signal into the dead-band DC signal. In some embodiments, the DC-DC power converters are connected in series. Additionally, in some embodiments, the DC-DC power converters are integrated as part of a continuous trunk cable, which may include a plurality of housings. In such embodiments, each DC-DC power converter may include a removable cartridge configured to selectively engage within one of the housings and thereby be electrically integrated into the trunk cable. In particular, in some embodiments, the trunk cable may include a 20-ampere rated cable.

[0009] According to various embodiments, the duration of each dead-band period with zero voltage may be, for example, about 100 microseconds, while the rectified sinusoidal waveform of the dead-band DC signal may have a frequency of, for example, about 60 Hz. Additionally, in some embodiments, the DC-DC power converters are configured to vary the duration of each of the dead-band periods. The electrical network interface may also be configured to communicate with each of the DC-DC power converters and synchronize each of the DC-DC power converters.

[0010] According to another embodiment of the present invention, a power distribution system for providing AC power to an electrical network is provided. In various embodiments, the system includes: (i) one or more DC power sources, each DC power source being configured to generate a DC power signal; (ii) one or more DC-DC power converters, each DC-DC power converter being connected to at least one of the DC power sources and being configured to convert the DC power signal received from one of the DC power sources into a dead-band DC signal, wherein the dead-band DC signal includes a rectified waveform having a repeatedly occurring dead-band period; and (iii) an electrical network interface, the electrical network interface being connected to the plurality of DC-DC power converters and being configured to convert the dead-band DC signal received from the plurality of DC-DC power converters into an AC power signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Reference will now be made to the accompanying drawings, which are not necessarily to scale, and in which:

[0012] Figure 1A An example standard alternating current (AC) waveform is shown;

[0013] Figure 1B An example standard direct current (DC) waveform is shown;

[0014] Figure 2 A schematic diagram of a dead-band DC converter system is shown;

[0015] Figure 3 An exemplary circuit diagram of a dead-band DC-DC power converter is shown;

[0016] Figure 4A An exemplary dead-band DC waveform according to one embodiment is shown;

[0017] Figure 4B An exemplary dead-band DC waveform according to one embodiment is shown;

[0018] Figure 5A A residential environment with a photovoltaic DC power system according to one embodiment is shown;

[0019] Figure 5B A schematic diagram of a cable-integrated dead-band DC-DC converter system according to one embodiment is shown;

[0020] Figure 6A An isometric view of a power converter box and a housing according to one embodiment, wherein the power converter box is separated from the housing.

[0021] Figure 6B Shows Figure 6A An isometric view of the power converter box and the housing, wherein the power converter box is fixed to the housing;

[0022] Figure 7 Shows an isometric view of a cable-integrated dead-time DC-DC converter according to another embodiment;

[0023] Figure 8A Shows a plan view of a cable-integrated dead-time DC-DC converter according to yet another embodiment;

[0024] Figure 8B Shows Figure 4A a plan view of the cable-integrated dead-time DC-DC converter of;

[0025] Figure 9 Shows a schematic diagram of a conventional DC transmission and distribution system; and

[0026] Figure 10 Shows a schematic diagram of a dead-time DC transmission and distribution system according to another embodiment. DETAILED DESCRIPTION

[0027] Various embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, embodiments of the invention are shown. In fact, the inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Unless otherwise noted, the term "or" is used herein in an alternative and conjunctive sense. The same numbers refer to the same elements throughout.

[0028] In some embodiments, a dead-time DC distribution system inserts regular zero-voltage periods or "dead time" into the DC power signal. In some embodiments, the dead-time DC converter system also advantageously shapes the DC power signal into a shaped waveform described in further detail herein. According to various embodiments, a dead-time DC distribution system is provided that allows power to be interrupted more easily by a circuit breaker. In particular, the dead-time DC converter system is configured such that a standard AC-rated circuit breaker can be used instead of a typically more expensive DC-rated circuit breaker to prevent sustained arcing and overcurrent situations. According to various embodiments, if arcing occurs in the dead-time DC distribution system (e.g., due to incorrect wiring or a damaged connector), the arc caused by the fault will extinguish during the next regular zero-voltage period. In this way, the dead-time DC distribution system will behave similarly to an AC system, where arcs typically extinguish when the AC signal crosses zero volts.

[0029] In various embodiments, the technology will allow for the use of smaller AC-rated equipment, such as circuit breakers, in DC distribution systems, thus significantly saving cost and size. According to various embodiments, the period of zero voltage can be adjusted based on voltage and / or current levels. Additionally, various wave shapes in the waveform can be used for this purpose to optimize power transmission, each waveform including a periodic zero voltage period (e.g., as described below Figure 4A and 4B shown). In fact, the dead time in the shaped waveform matches the zero-crossing advantage of the traditional AC waveform without the need to fully invert the power to AC.

[0030] Figure 2 A schematic diagram of a dead-time DC converter system is shown. Example embodiments include a DC power source 202. In some examples, the DC power source 202 may be embodied by one or more of a plurality of DC power sources, such as solar panels, a solar panel array, a windmill, a fuel cell, a generator, a battery, an AC-DC transformer, or a combination of one or more of a plurality of DC power sources, including those not listed herein.

[0031] Figure 2 Example embodiments of also include a dead-time DC converter 204 that receives DC power from the DC power source 202. In some examples, the dead-time DC converter 204 is configured to convert a standard DC waveform (such as waveform 103) into a shaped dead-time DC waveform. Converting the standard DC waveform into a dead-time DC waveform will be discussed in further detail in conjunction with Figure 3 , Figure 4A and Figure 4B .

[0032] Figure 2 Example embodiments of also include an electrical network interface 206 that receives the shaped dead-time DC waveform from the dead-time DC converter 204. In some embodiments, the electrical network interface 206 is configured as an inverter to invert the shaped dead-time DC waveform from the dead-time DC converter 204 into an output AC waveform. In some embodiments, the output AC waveform is configured to be output to an AC power network, such as a local power utility grid.

[0033] In some example embodiments, the electrical network interface 206 is configured to output the dead-time DC waveform from the dead-time DC converter 204 to a DC distribution system, such as a DC distribution system in a home or business. In some examples, the electrical network interface 206 is configured to directly output the dead-time DC waveform from the dead-time DC converter 204 to the DC distribution system. In some examples, the electrical network interface 206 is configured to transform the dead-time DC waveform to a higher or lower voltage according to the configuration of the DC distribution system.

[0034] In some examples, the electrical network interface 206 is configured to output an AC signal to an AC power network (such as to a local power utility) and a DC distribution system (such as a DC distribution system in a home or business). In some examples, the ratio of the amount of output sent as an AC signal to the AC power network to the output sent as a DC signal depends on factors such as the amount of power supplied by the DC power source 202, the power demand of the DC distribution system, user preferences, and / or the power demand of the AC power network. For example, if the power demand of the DC distribution network in a home increases due to an increase in the amount of activity within the home, then the electrical network interface 206 can direct most or all of the power from the DC power source 202 and the dead-band DC converter 204 to the DC distribution system for use within the home rather than directing the power to the AC power network. In some examples, if the power demand of the DC distribution network in a home is minimal due to low energy demand, then the electrical network can be configured to output most or all of the power from the DC power source 202 and the dead-band DC converter 204 to the AC power network, such as the local utility grid.

[0035] Figure 3 A circuit diagram of a dead-band DC-DC power converter 300 is shown. In some examples, the dead-band DC-DC power converter 300 can be embodied in a converter such as the dead-band DC converter 204 or other embodiments described herein. In this example, input DC power is supplied from DC power 302. In some examples, DC power 302 can be the DC power source 202 or other embodiments described herein.

[0036] In some examples, the dead-band DC-DC power converter 300 includes switching transistors 304 and 306, which can be configured to regulate the power flow through the converter to output dead-band DC power 308. The switching transistors 304 and 306 are configured to vary the switching times in the converter to convert a flat standard DC waveform such as waveform 103 into a shaped DC waveform with a "dead time," or to insert a dead band into the signal.

[0037] Figure 4A and 4B Example waveforms are shown that can be generated by the dead-band DC-DC power converter 300. For example, waveform 402 can be generated by the switching transistors 304 and 306 and by including a variable dead time 404 to produce a dead-band DC waveform such as the dead-band rectified sine waveform represented in waveform 402. Alternatively or additionally, waveform 406 can be generated by the switching transistors 304 and 306 and includes a variable dead time 408 to produce an alternative dead-band DC waveform. In both examples, the variable dead times 404 and 408 are similar to the AC voltage waveform zero-crossings 102, asFigure 1A As shown, to allow standard AC-rated equipment (such as an AC circuit breaker) to be used for overcurrent and arc protection. In some examples, the lengths of the dead times 404 and 408 can be adjusted such that power transfer is optimized while still providing the advantages of dead-time DC power. In some examples, the variable dead times 404 and 408 can include non-zero voltages such that the output voltage is low enough to serve as a dead time and allow the arc to be extinguished and the use of AC equipment.

[0038] Additionally, the shaping of the standard DC of both waveforms 404 and 408 allows the standard DC power to be more easily used in other applications, such as output to an AC power network or distribution in a dead-time DC distribution system. For example, since the shaped waveform 402 is similar to a rectified AC sine waveform, it allows the waveform 402 to be easily inverted to a standard AC waveform, such as waveform 101, for output to the local power grid. Additionally, shaping the standard DC waveform into a shaped waveform allows a dead time to be inserted into the waveform without causing increased electromagnetic interference that might be caused by a sharp change in voltage or current.

[0039] Return reference Figure 2 and Figure 3 , in some examples, the DC-DC power converter 300 can be embodied in the dead-time DC converter 204, where the dead-time DC converter 204 is configured to be connected to an input DC power source, such as the DC power source 202, and detect the nature of the input DC power source, such as voltage or current. In some examples, the dead-time DC converter 204 is configured to determine the nature of the output DC signal, such as voltage, dead time, and waveform. In some examples, a DC converter, such as the dead-time DC converter 204, communicates with an electrical network interface (such as the electrical network interface 206), and the electrical network interface 206 can specify the nature of the output DC signal (such as the output dead-time DC power 308). For example, the dead-time DC converter 204 can be configured to determine from the specified nature that the output DC signal should have a dead time of 100 microseconds and have a waveform (such as waveform 402) suitable for inverting an AC signal.

[0040] In some embodiments, the dead-time DC converter 204 is configured to control the switching transistors 304 and 306 to generate the desired output dead-time DC power 308 from the input DC power 302, and the desired output dead-time DC power 308 has specified properties, including adjustable voltage, dead time, and waveform.

[0041] Return reference Figure 3 , in some examples, the input DC power 302 and the output power 308 can be a single-phase 120-volt electrical system. The converter can be used to generate a rectified voltage at the output 308, which is similar to Figure 4AThe waveforms shown in . In this example, switch transistors 304 and 306 can be configured to include a dead time or deadband of 100 microseconds, such as variable dead times 404 and 408, approximately every 8.33 milliseconds. The 8.33 millisecond interval corresponds to a rectified AC 60Hz signal, but the present invention is applicable to other types of electrical systems, including 50 hertz electrical systems. In some examples, since the current or voltage of the input DC power 302 can be greater than or less than the above example, switch transistors 304 and 306 can be configured to insert longer or shorter dead times or deadbands over longer or shorter time spans.

[0042] In addition, it should be understood that the present invention is applicable to many types of DC power sources, such as other types of renewable energy sources (such as windmills, water wheels, geothermal), and is applicable to other types of energy storage devices, such as fuels, batteries, capacitor banks, and / or the like.

[0043] Reference Figure 5A and Figure 5B and, according to certain embodiments, the deadband DC distribution system is embodied as a cable integrated converter system that is provided for converting DC power received from photovoltaic cells into deadband DC power. The cable integrated converter system can be used in conjunction with various photovoltaic power systems, including systems in industrial, commercial, residential, and / or other power generation, transmission, and distribution environments. As an example, Figure 5A illustrates a building structure 5 that has a photovoltaic power system interconnected with a deadband DC distribution system 9 routed through the structure 5. In the illustrated embodiment, the photovoltaic power system includes a photovoltaic solar cell array 10. In particular, the solar cell array 10 is configured to be combined with a wind turbine 20 to generate power that can be stored in an energy storage unit (e.g., including the illustrated battery array 22 and fuel cell array 24). In the illustrated embodiment, a fuel-operated generator 26 is also provided for emergency operation.

[0044] Figure 5A The photovoltaic solar cell array 10 of includes a plurality of photovoltaic solar panels 11 - 18. Although the building structure 5 has been shown as a residential building structure, it should be understood that the photovoltaic solar cell array 10 can be installed on almost any type of building structure or on the ground. In one embodiment, each of the plurality of photovoltaic solar panels 11 - 18 is made up of a plurality of photovoltaic solar cells 19. Each of the photovoltaic solar cells 19 can generate, for example, approximately 0.5 volts. When connected in series and parallel, the cells 19 can provide, for example, approximately 300 watts of power at 30 volts. In some cases, individual photovoltaic solar panels 11 - 18 are mounted on equatorial mounts (not shown) for following the movement of the sun during the day.

[0045] Figure 5B FIG. 1 shows a schematic diagram of a cable integrated converter system 108 according to an embodiment. In the illustrated embodiment, the cable integrated converter system 501 includes a main cable 502, a plurality of power converters 606 distributed along the main cable 502, and an electrical network interface 206. As Figure 5B shown, each of the power converters 606 is electrically connected to one of a plurality of photovoltaic modules 11 - 18. The power converters 606 are also connected in series with each other via the main cable 502. As explained in more detail herein, each of the power converters 606 is configured to function as a dead - zone DC power converter, such as the dead - zone DC converter 204. In operation, the power converters 606 convert the DC power received from the photovoltaic modules 11 - 18 into various shaped DC waveforms with dead zones, including, for example, a rectified half - sine wave signal with a dead zone or waveforms 402 and 404, which are added and delivered to the electrical network interface 206 via the main cable 502.

[0046] In some examples, multiple power converters (such as power converters 606) fed into a single line (such as the main cable 502) require the power converters to be highly synchronized to prevent equipment failures due to synchronization differences. In some examples, the electrical network interface 206 is configured to communicate with the power converters 606 via the main cable 502 and provide the necessary parameters to ensure synchronization. Additionally, including a dead zone advantageously aids in this synchronization. For example, in DC - to - AC inversion, the dead zone allows for improved synchronization between signal switching between positive and negative signals.

[0047] As Figure 5B shown, the power converters are integrated into the main cable 502, and the main cable 502 connects the power converters 606 in series. As an example, in one embodiment, the main cable 502 includes a 30 - ampere rated AC cable. In another embodiment, the main cable 502 includes a 20 - ampere rated AC cable. The main cable 502 extends between the integrated power converters 606, and the integrated power converters 606 can be embedded, enclosed, or otherwise integrated into the cable in various ways. In some examples, the main cable 502 includes at least two wires for power transmission and two wires for communication between the power converters 606 and the electrical network interface 206.

[0048] As an example, Figure 6A FIG. 2 shows an isometric view of a cable integrated dead - zone DC power converter 606 according to an embodiment. In the illustrated embodiment, for ease of maintenance and replacement of a faulty device, the power converter 606 includes a removable box 611, which can be selectively removed from the main cable 502. In particular, as Figure 6AAs shown, the power converter box 611 is configured to be selectively fixed to the housing 608. According to various embodiments, the housing 608 may be constructed of a thermally conductive material (e.g., metal, metal alloy, thermally conductive plastic, a combination of plastic and metal, and / or the like). For example, the housing 608 may be constructed of a thermally conductive plastic and include a metal heat sink. Similarly, the power converter box 611 may be constructed of a similar thermally conductive material in a similar manner.

[0049] As Figure 6A shown, the housing 608 is a generally rigid member that defines a generally horizontal flat base and a central recessed area 614 that is configured to receive the removable power converter box 611. Opposite ends of the housing 608 are attached to the trunk cable 502. For example, in the illustrated embodiment, the trunk cable 502 is fixed to the housing 608 in a weatherproof manner (e.g., via weatherproof rubber gaskets 613a, 613b, or by overmolding the housing onto the trunk cable).

[0050] In the illustrated embodiment, the power converter box 611 defines a generally rigid outer shell that is configured to be inserted into the recessed area 614 of the housing 608. As explained in more detail below, the electronic components of the power converter are sealed within the box 611 and are thus protected from the external weather. As Figure 6A shown, the power converter box 611 includes a positive terminal 602 and a negative terminal 604 that are configured to be connected to the photovoltaic modules 11-18. In particular, the terminals 602, 604 enable the power converter 606 to receive DC power from the photovoltaic modules 11-18, and then the power converter 606 converts it into a shaped DC waveform with a dead zone, as described below.

[0051] The power converter box 611 also includes connection terminals 610b on its opposite ends for providing an electrical connection between the power converter box 611 and its housing 608. As Figure 6A shown, the housing 608 includes corresponding connection terminals 610a that project inwardly into the recessed area 614 of the housing. Thus, the connector terminals 610b of the power converter box are conductive cavities that are configured to receive the connector terminals 610a of the housing. In the illustrated embodiment, the connectors 610a and 610b help to fix the power converter box 611 within the housing 608. Additionally, in the illustrated embodiment, the power converter box 611 and the housing 608 each include two connectors. However, in various other embodiments, the power converter box 611 and the housing 608 include a single connector or multiple connectors (e.g., three connectors, four connectors, five connectors, and / or the like). In additional embodiments, the connectors may include only flat electrical contacts that contact each other.

[0052] According to certain embodiments, the electrical connector is configured to provide a dedicated electrical connection between the power converter 606, an adjacent power converter 606, and the electrical network interface 206. For example, in one embodiment, the electrical connector includes a power connection line, a fault detection line, and a synchronization line between the power converter 606 and the electrical network interface 206.

[0053] As described above, the power converter box is configured to be removably fixed within the housing 608. Figure 6B A power converter box 611 fixed within the housing 608 is shown. According to various embodiments, the housing 608 may include a latch or other fastening means (not shown) for securing and / or releasing the power converter box. In other embodiments, the shape of the housing 608 aids in snapping the power converter box 611 into place when inserted into the housing.

[0054] In certain embodiments, the power converter 606 may include a light emitting diode (LED) to indicate the status of the power converter. For example, if the power converter is properly fixed in place, the LED may display a green light. Or, if the power converter is loose and / or not properly fixed within the housing 608, the LED may display a red light.

[0055] As described below, the power converter 606 electronics are housed within the power converter box 611. In certain embodiments, when the power converter box 611 is removed from the housing 608, a jumper box may be inserted to bridge the gap left by the power converter box. In other embodiments, a set of connectors may be provided to connect the power converter to a cable. The connectors left on the cable after removing the power converter may then be directly connected together to connect the gap left by removing the converter. Additionally, when it is determined that the power converter 606 is faulty, the power converter 606 may be easily replaced by inserting a new power converter box 611 into the corresponding housing 608.

[0056] It should be understood from the description herein that, in one embodiment, Figure 5B each of the power converters 606 shown in Figure 6A and 6B may adopt the configuration shown and described with respect to

[0057] As another example, Figure 7 An isometric view of a cable integrated dead - zone DC power converter 606 according to another embodiment is shown. In Figure 7In the illustrated embodiment, the electronics of the power converter are housed within a housing 711, which may be sealed for weather protection. The housing of the power converter includes a positive terminal 705 and a negative terminal 708, which are configured such that the power converter can be connected to a photovoltaic module. The housing 711 also includes terminals 702a, 702b, and 702c disposed on its opposite ends. The terminals 702a, 702b, and 702c are configured to provide a detachable electrical connection to the backbone cable 502 at both ends of the housing 711. For example, as Figure 7 shown, the trunk cable 502 includes corresponding connection terminals 704a, 704b, and 704c. The opposite ends of the power converter 606 (blocked by the view in Figure 7 ) are connected to the second section of the trunk cable 502 in the same manner.

[0058] In one embodiment, a pair of corresponding power converter and trunk cable connection terminals 702a / 704a; 702B / 704B; and 702c / 704c are configured to provide a dedicated electrical connection between the power converter 606, an adjacent power converter 606, and the above-described electrical network interface 206. For example, in one embodiment, the terminal 702a / 704a connects a power connection line, the terminal 702b / 704b connects a fault detection line, and the terminal 702c / 704c connects a synchronization line, with each connection established between the power converter 606 and the electrical network interface 206. It should be understood from the description herein that the terminals 702a / 704a, 702b / 704b, and 702c / 704c may be integrated into a single multi-pin interface.

[0059] Regarding Figure 7 the illustrated embodiment, a faulty power converter 606 can be replaced by disconnecting the trunk cable 502 from the power converter 606 and connecting the trunk cable 502 to a new power converter 606 of the same type. Thus, Figure 7 the actual operation of the cable laying system is similar to that described above with reference to Figure 6A and Figure 6B .

[0060] As yet another example, Figure 8A and Figure 8B show a top view of a cable integrated dead zone DC power converter 606 according to another embodiment. In Figure 8A the illustrated embodiment, the electronics of the power converter are housed within a power converter box 811, which is configured to be removably fixed between brackets 804 and 802 disposed at the ends of a section of the trunk cable 502. According to various embodiments, the power converter box 811 is configured to be connected to the photovoltaic modules 11-18 via positive and negative terminals (not shown), as described above.

[0061] Each of brackets 804 and 802 is configured to be removably attached to opposite ends of the power converter box 811. For example, bracket 804 includes projecting elements 804a and 804b for removably attaching the trunk cable 502 to the power converter box 811. Similarly, bracket 802 includes projecting elements 802a and 802b for removably attaching the trunk cable 502 to the power converter box 811. As Figure 8A and Figure 8B shown, the shape of the edges of brackets 804 and 802 corresponds to the shape of the edges of the power converter box 811. Inserting the power converter box 811 into bracket 802 fixes the power converter box 811 between elements 802a and 802b. Similarly, inserting the power converter box 811 into bracket 802 fixes the power converter box 811 between elements 804a and 804b. The projecting elements 804a, 804b; 802a, 802b can be configured to partially surround and engage the power converter box 811 using a press-fit configuration, a snap configuration, a latch, a magnetic attachment, or by other suitable means.

[0062] Figure 8A illustrates the power converter box 811 disconnected from the trunk cable 502, while Figure 8B illustrates the power converter box 811 connected and fixed to the trunk cable 502. As shown, the trunk cable 502 is electrically connected to brackets 804 and 802 (e.g., with weatherproof rubber gaskets 813a, 813b for a secure connection). Brackets 804, 802 are configured to electrically connect the power converter box 811 to the trunk cable 502 via projecting terminals 806a and 808a. In particular, the projecting terminals 806a and 808a are configured to be inserted into corresponding terminals 806b and 808b of the power converter box 811. As can be understood from Figure 8A and Figure 8B inserting terminal 806a into terminal 806b establishes an electrical connection between the first section of the trunk cable 502 and the power converter box 811, while inserting terminal 808a into terminal 808b establishes an electrical connection between the second section of the trunk cable 502 and the power converter box 811. Additionally, connecting terminals 808 and 806 helps to fix the power converter box 811 to brackets 802, 804 and the trunk cable 502.

[0063] In one embodiment, a corresponding pair of power converter box 811 and trunk cable 502 connection terminals 808a / 808b and 806a / 406b are configured to provide a dedicated electrical connection between the power converter 606, adjacent power converters 606, and the above-described electrical network interface 206. For example, in one embodiment, Figure 8A and Figure 8BThe three pins of the electrical connections 808a, 808b and 806a, 806b shown in [Fig. 0] respectively represent a power connection line, a fault detection line and a synchronization line. However, as will be understood from the description herein, the connection terminals may be integrated into a single multi-pin interface or any other suitable electrical connection interface. In fact, in various other embodiments, the power converter box 811 and the housing 608 may include a single connector or multiple connectors (e.g., four connectors, five connectors, and / or the like). Additionally, in further embodiments, the connector may include flat electrical contacts that only contact each other.

[0064] Figure 9 A schematic diagram of an alternative DC transmission and distribution system 900 without a dead-time DC converter is shown, which can be improved by various embodiments described herein. In the DC transmission and distribution device 900, the photovoltaic solar cell array 10 directly generates electrical power as a standard DC waveform (such as waveform 103) into the DC transmission and distribution system 904. In order for the DC transmission and distribution system 904 to safely distribute power in industrial, commercial, residential, and / or other power generation, transmission, and distribution environments (such as a home or business), expensive DC safety precautions must be implemented. For example, a DC circuit breaker 902 must be installed to prevent continuous arc faults from occurring in the system 904.

[0065] Figure 10 A schematic diagram of a dead-time DC transmission and distribution system 1000 is shown. The system 1000 includes a single dead-time DC-DC converter 1002. The DC-DC converter 1002 may be configured to convert the DC power generated by the photovoltaic solar cell array 10 into a dead-time DC signal or waveform for distribution. In some embodiments, the DC-DC converter 1002 may include a dead-time DC converter 204 and an electrical network interface 206 to output a dead-time DC power signal to the DC distribution network 1006. For example, the DC distribution network 1006 may supply power to an LED lighting network in a home or business. In another example, the DC-DC converter 1002 may directly output a dead-time DC power signal to the LED lighting network. Due to the advantages of the dead-time DC signal generated by the DC-DC converter 1002, the dead-time DC transmission and distribution system 1000 does not require more expensive DC-rated equipment, such as the DC circuit breaker 902, but instead may use a more common and less expensive AC circuit breaker 1004 to eliminate faults in the DC transmission and distribution system 1000.

[0066] Although this specification contains many specific implementation details, these should not be construed as limitations on the scope of any invention described herein, but rather as descriptions of features specific to particular embodiments of a specific invention. Certain features described herein in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, the various features described in the context of a single embodiment can also be implemented separately in multiple implementations or in any suitable sub-combination. Additionally, although the features may have been described above as acting in certain combinations, one or more features from a combination may in some cases be removed from the combination, and the combination may involve a sub-combination or variation of a sub-combination.

[0067] Furthermore, those skilled in the art will envision many modifications and other embodiments of the invention set forth herein in light of the foregoing description and the teachings presented in the related drawings. Accordingly, it is to be understood that the invention is not limited to the specific embodiments disclosed, and that modifications and other embodiments are intended to be included within the scope of this application.

Claims

1. A photovoltaic power system for powering an electrical grid, the system comprising: A solar cell array including a plurality of photovoltaic panels, wherein each photovoltaic panel is configured to generate a DC power signal; A plurality of DC-DC power converters, each DC-DC power converter connected to at least one of the photovoltaic panels and configured to convert the DC power signal generated by its corresponding photovoltaic panel into a dead-band DC signal, wherein the dead-band DC signal includes a rectified sinusoidal waveform having a recurring dead-band period of zero voltage; An electrical network interface connected to the plurality of DC-DC power converters and configured to convert the dead-band DC signals received from the plurality of DC-DC power converters into AC power signals, wherein the electrical network interface is further connected to the electrical grid and configured to supply the AC power signals to the electrical grid, wherein each of the plurality of DC-DC power converters includes a pair of switching transistors configured to convert the DC power signal into the dead-band DC signal; And One or more electrical connectors between the electrical network interface and the plurality of power converters, the one or more electrical connectors including at least one or more fault detection lines.

2. The photovoltaic power system according to claim 1, wherein the one or more electrical connectors further include one or more synchronization lines.

3. The photovoltaic power system according to claim 1, wherein the DC-DC power converters are connected in series.

4. The photovoltaic power system according to claim 3, wherein the DC-DC power converters are integrated as part of a continuous trunk cable.

5. The photovoltaic power system according to claim 4, wherein the trunk cable includes a plurality of housings integrated into the trunk cable, and Wherein each DC-DC power converter includes a removable box configured to selectively engage within one of the housings and thereby be electrically integrated into the trunk cable.

6. The photovoltaic power system according to claim 4, wherein the trunk cable includes a 20 ampere rated cable.

7. The photovoltaic power system according to claim 4, wherein the trunk cable is fixed to the electrical network interface for transmitting the dead-band DC signals generated by the DC-DC power converters to the electrical network interface.

8. The photovoltaic power system according to claim 1, wherein the electrical network interface includes an inverter.

9. The photovoltaic power system according to claim 1, wherein the duration of each dead-band period of zero voltage is about 100 microseconds.

10. The photovoltaic power system according to claim 1, wherein the rectified sinusoidal waveform of the dead-band DC signal has a frequency of about 60 Hz.

11. The photovoltaic power system according to claim 1, wherein the DC-DC power converters are configured to vary the duration of each dead-band period.

12. The photovoltaic power system according to claim 1, wherein the electrical network interface is configured to communicate with each of the DC-DC power converters and synchronize each of the DC-DC power converters.

13. A power distribution system for supplying AC power to an electrical network, the system comprising: one or more DC power sources, each DC power source being configured to generate a DC power signal; one or more DC-DC power converters, each DC-DC power converter being connected to at least one of the DC power sources and being configured to convert a DC power signal received from one of the DC power sources into a dead-band DC signal, wherein the dead-band DC signal includes a rectified waveform having a repeatedly occurring dead-band period; an electrical network interface, the electrical network interface being connected to the plurality of DC-DC power converters and being configured to convert the dead-band DC signals received from the plurality of DC-DC power converters into an AC power signal; and one or more electrical connectors between the electrical network interface and the plurality of power converters, the one or more electrical connectors including at least one or more fault detection lines.

14. The power distribution system according to claim 13, wherein the dead-band period includes a period of zero voltage.

15. The power distribution system according to claim 13, wherein the dead-band DC signal includes a rectified sine wave.

16. The power distribution system according to claim 13, wherein the dead-band period in the dead-band DC signal includes a period of zero voltage.

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