Microinverters for employment in connection with photovoltaic modules

Microinverters useable in association with photovoltaic modules are described. A three phase-microinverter receives direct current output generated by a microsystems-enabled photovoltaic cell and converts such direct current output into three-phase alternating current out. The three-phase microinverter is interleaved with other three-phase-microinverters, wherein such microinverters are integrated in a photovoltaic module with the microsystems-enabled photovoltaic cell.

BACKGROUND

Environmental concerns pertaining to utilization of fossil fuels to generate electric power, together with the non-renewable nature of such fossil fuels, have increased demand for alternative energy sources. Exemplary electric power systems that utilize renewable energy resources include solar power systems, wind power systems, hydroelectric power systems, geothermal power systems, amongst others.

Conventional solar power systems, particularly those utilized to provide electric power to a residence, include solar panels that comprise a plurality of relatively large silicon photovoltaic cells (e.g., approximately six inches by six inches). For instance, a single solar panel can include approximately 72 cells. The solar cells are manufactured to output a certain voltage (e.g., 0.6 V for silicon cells) that is approximately constant regardless of an amount of solar radiation received at the solar cells. Additionally, the solar cells are electrically connected in series within a solar panel, such that the solar panel produces approximately 40 V. A typical residential solar system includes several solar panels (e.g., between 5 and 10), and the panels are electrically connected in series, thereby resulting in several hundred cells being electrically connected in series that collectively output a voltage that is approximately equal to the sum of the voltages of the individual cells.

In typical solar power system installations, the series connected cells are coupled to an inverter that converts direct current output by the solar power installation into alternating current suitable for provision to the electric grid. Generally, because power produced by the photovoltaic system is relatively high, the inverter tends to be relatively sizable and costly, due at least in part to a large capacitance needed in a DC link that couples the solar power system to the inverter, as well as the relatively large inductance required on an output leg of the inverter for purposes of filtering. Moreover, such inverters are generally sold separately from the solar panels themselves. Thus, to install a solar power system on a residence, the panels themselves must be mounted, wired, inverters must be added, etc., increasing the cost of installing the solar power system.

SUMMARY

Described herein are various technologies pertaining to microinverters that can be utilized in connection with photovoltaic modules that include solar cells. In an exemplary embodiment, such solar cells can be microsystems-enabled photovoltaic (MEPV) cells, although the invention is not so limited. MEPV cells are photovoltaic cells manufactured utilizing semiconductor manufacturing techniques, and tend to be relatively small, with diameters, for instance, between 100 μm and 5 mm, with thicknesses between 1 μm and 1000 μm. Pursuant to an exemplary embodiment, a photovoltaic module includes at least one MEPV cell that is electrically connected to a three-phase microinverter. The microinverter can include a DC link with a capacitance of between 100 nF and 1 μF. It is to be understood, however, that in other embodiments, the DC link can have a larger capacitance, such as between 1 μF and 5 μF or more. Additionally, the inverter can comprise three phase legs, wherein inductance of each of the three phase legs can be between 4 mH and 10 mH. It is to be understood that the inductance is dependent upon switching frequency; as the switching frequency increases, an amount of inductance decreases. In an exemplary embodiment, the three-phase microinverter can be included in an apparatus that is physically separate from the photovoltaic module. In another exemplary embodiment, the three-phase microinverter can be integrated into the photovoltaic module, such that the MEPV cell and the three-phase microinverter reside on a common substrate. Thus, the three-phase microinverter can be an integrated circuit.

Further, a photovoltaic module can include numerous sub-modules that are connected in series, wherein each string of sub-modules can have a respective three-phase microinverter electrically connected thereto. These three-phase microinverters can be electrically connected in parallel.

Pursuant to another example, a photovoltaic module can be associated with a plurality of interleaved microinverters that are electrically connected in parallel with one another. In such an embodiment, the microinverters can be single-phase, three-phase, or any poly-phase microinverters. Again, pursuant to an example, such microinverters can be integrated into the photovoltaic module. As the photovoltaic module comprises a plurality of interleaved microinverters, power rating of such microinverters can be relatively small. For instance, the power-rating of an interleaved microinverter can be between 15 W and 30 W. Additionally, each phase leg of each interleaved microinverter can have in inductance of between 500 pH and 1 mH, although as mentioned above, such inductances can depend upon a switching frequency employed. As is well known to practitioners, the inductance also depends on power rating and specifications for current ripple, and can be implemented with values much different than the range between 500 μH and 1 mH if preferred by the designer.

Other aspects will be appreciated upon reading and understanding the attached figures and description.

DETAILED DESCRIPTION

Various technologies pertaining to associating microinverters with photovoltaic modules that comprise micro-system enabled photovoltaic (MEPV) cells will now be described with reference to the drawings, where like reference numerals represent like elements throughout. Additionally, as used herein, the term “exemplary” is intended to mean serving as an illustration or example of something, and is not intended to indicate a preference.

With reference now toFIG. 1, an exemplary photovoltaic module100is illustrated. The photovoltaic module100can be a portion of a solar power system. For example, the photovoltaic module100can also be referred to as a solar panel, solar module, or the like.

In an exemplary embodiment, the photovoltaic module100can comprise a plurality of MEPV cells that are selectively electrically connected in series and parallel, in a manner described herein, to cause the photovoltaic module100to output a desired amount of voltage at a desired amount of current. MEPV cells are manufactured by way of semiconductor manufacturing techniques and are relatively small with diameters of between 100 μm and 5 mm and thicknesses as low as 1 μm for a III-V cell, but potentially as large as 1000 μm. Due to the relatively small size of the MEPV cells, the photovoltaic module100can comprise thousands of MEPV cells, in comparison to the 72 cells included in conventional photovoltaic modules.

As shown inFIG. 1, the photovoltaic module can comprise a first solar cell102. In an exemplary embodiment, the first solar cell102can be a MEPV cell. Thus, the first solar cell102, in an exemplary embodiment, can be a III-V cell, such as a gallium arsenide (GaAs) cell, an indium gallium phosphide (InGaP) cell, or an indium gallium arsenide (InGaAs) cell. In other exemplary embodiments, the first solar cell102can be a silicon (Si) cell. In still another embodiment, the first solar cell102can be a germanium (Ge) cell. In still another exemplary embodiment, the first solar cell102can be a multi-junction cell that comprises a suitable combination of the aforementioned cell types electrically connected in series. In still another example, the first solar cell102may be a portion of a multi junction cell that is independently contactable. It is therefore to be understood that the first solar cell102can be any suitable type of solar cell or portion of a multi junction solar cell.

Further, while not shown, the first solar cell102can be a portion of a string of solar cells connected in series. As will be shown below, such series-connected string of solar cells can be coupled in parallel with other series-connected strings of solar cells. These parallel connections may then be coupled in series with other similarly configured groups of solar cells, such that the photovoltaic module100outputs a desired voltage and current. In an exemplary embodiment, operating voltage of the solar cell102can be between 0.2 V and 3 V. Current traveling over the solar cell102can be relatively low, such as on the order of milliamps.

The photovoltaic module100further comprises a first microinverter104that is configured to convert direct current output by the first solar cell102to alternating current. In an exemplary embodiment, the first microinverter104can be a three-phase microinverter that converts direct current output by the first solar cell102to three-phase alternating current. As shown inFIG. 1, the first microinverter104can be an integrated circuit that is integrated into the photovoltaic module100, such that the first microinverter104lies on a substrate with the first solar cell102. In another exemplary embodiment, the first microinverter104can be in an apparatus that is separate from the photovoltaic module100, such that the first microinverter104can be implemented as a printed circuit board with discrete circuit elements. Other embodiments are likewise contemplated. The first microinverter104thus acts as at least a portion of an interface between the photovoltaic module100and the AC grid.

The photovoltaic module100can also comprise a second solar cell106. The second solar cell106can likewise be an MEPV cell, and can additionally be any of the cell types mentioned above with respect to the first solar cell102. Further, it is to be understood that a type of the first solar cell102can be different from a type of the second solar cell106. The photovoltaic module100further comprises a second microinverter108that is electrically connected to the second solar cell106. The second microinverter108receives direct current output by the second solar cell106, and in an exemplary embodiment, converts such direct current to three-phase alternating current. As shown, the first microinverter104and the second microinverter108can be electrically connected in parallel and can collectively act as at least a portion of an interface between the cells of the photovoltaic module100and the AC grid. In an exemplary embodiment, the first microinverter104and the second microinverter108can be integrated in the photovoltaic module100. In other embodiments, the first microinverter104and the second microinverter108can be in an apparatus that is separate from the photovoltaic module100.

While the photovoltaic module100is shown as including two microinverters connected in parallel, it is to be understood that the number of microinverters included in the photovoltaic module100can be greater than two. For example, if the photovoltaic module100comprises eight separate sub-modules, for example, then the photovoltaic module100may include eight microinverters that respectively correspond to the eight sub-modules, and wherein the eight microinverters are electrically connected in parallel with one another.

In another exemplary embodiment, the first microinverter104and the second microinverter108can be interleaved. The interleaving of the first microinverter104and the second microinverter108can result in substantial cancellation of the current ripple of the individual inverters104and108, while the fundamental component of each waveform output by the respective microinverters104and108are constructively reinforced when summed. In such an exemplary embodiment, the microinverters104and108can be single-phase inverters, three-phase inverters, or some other poly-phase inverters. Additionally, when multiple microinverters are connected in parallel in the photovoltaic module100, power rating of such microinverters can be reduced. For example, the power rating of the microinverters104and108can be between 15 W and 30 W. In contrast, if a single microinverter is employed to interface the photovoltaic module100with the AC grid, the power rating of such microinverter can be between 150 W and 300 W.

With reference now toFIG. 2, a schematic diagram of a microinverter200, which can be the first microinverter104and/or the second microinverter108, is illustrated. As shown inFIG. 2, the microinverter200is shown as being connected to the photovoltaic module100, rather than connected to a sub-module of the photovoltaic module100. It is to be understood, however, that the microinverter200can be coupled to a single solar cell, a string of series-connected solar cells, series connected sub-modules of the photovoltaic module100, a single sub-module of the photovoltaic module100, etc.

The microinverter200comprises a plurality of transistors202that are electrically connected to the photovoltaic module100by way of a DC link. The DC link has a capacitor204, which represents DC link capacitance. Such capacitance can be between 100 nF and 5 g. In an exemplary embodiment, the capacitance of the DC link can be 200 nF. The capacitor204is employed to buffer the photovoltaic module100from switching transients and maintain a small module voltage ripple. The aforementioned capacitance of 200 nF was selected via simulation to cause ripple losses to be less than 0.25% at a rated power of 200 W. It can therefore be ascertained that the capacitance of the capacitor204can be selected based on a threshold of acceptable ripple losses. For the microinverter200to be operational, the DC link voltage vpv, must always exceed the peak AC voltage.

The microinverter300comprises three phase legs206-210that are coupled to the AC grid. Each of the phase legs206-210has an inductance between 4 mH and 10 mH. In an exemplary embodiment, each of the phase legs206-210can have an inductance of 6 mH.

Maximum power point tracking can be employed in connection with controlling the microinverter200. A maximum power point tracker can be employed in connection with generating a voltage command for the photovoltaic module100. A PI controller can be employed to ensure that the voltage of the photovoltaic module100is driven to the voltage commanded by the maximum power point tracker by altering the magnitude of the phase current command, which controls current generated by the photovoltaic module100. A voltage with respect to neutral can be determined through a phase-locked loop. In general, the current output by the photovoltaic module100, the voltage of the photovoltaic module100, a neutral voltage, and current of the three phase legs206-210, can be monitored and employed in connection with outputting signals for a pulse width modulator to control the plurality of transistors202. The overall function of the control system is to increase the output current when the voltage of the photovoltaic module100is above the module maximum power point and decrease the output current when the voltage of the photovoltaic module100is below the module maximum power point.

Now referring toFIG. 3, a system300of interleaved microinverters that can be associated with the photovoltaic module100is illustrated. An interleaved set of n triangular waveforms with period TCcan be generated by introducing specified amounts of time delay between each of the multiple waveforms. Specifically, each waveform can be delayed by a unique multiple of Δ, where Δ=TC/n. Generally, any number of interleaved triangular waveforms greater than one sums to a smaller magnitude than the magnitude of the constituent waveform. It can therefore be concluded that if interleaved triangular waveforms are superimposed on any set of other waveforms, such as sine waves, and summed, the net signal contains the non-triangular portions of the original signals and the triangle ripple is attenuated.

FIG. 3illustrates multiple microinverters302-306arranged electrically in parallel, wherein interleaved carrier pulse width modulation is used. The system300comprises a plurality of photovoltaic modules308-312, wherein the microinverters302-306are respectively connected to the photovoltaic modules308-312. In another exemplary embodiment, the photovoltaic modules308-312can be sub-modules of a photovoltaic module, and the microinverters302-306can be integrated into the photovoltaic module. In the configuration shown inFIG. 3, the microinverters302-306can be single-phase, three-phase, or other poly-phase inverters. Further, it can be noted that the source of energy can be altered. For example, the plurality of inverters302-306can be employed in connection with conventional photovoltaic systems, batteries, fuel cells, rectified AC power sources, and the like.

In an exemplary embodiment, the triangular carrier waveforms are interleaved such that each carrier is delayed by a unique multiple of A, which can be defined as follows:

Δ⁢≡TCnp(1)
where TCis the carrier waveform period and npis the number of parallel inverters. The interleaved carrier waveforms have the effect of causing the switch timing among the inverters to be interleaved such that the ripple is also interleaved. Using this method, the interleaved nature of pulse width modulator (PWM) carrier signals is propagated to the final output current ripple. It can be noted that sawtooth or other types of carrier waveforms can also be implemented, so long as the switch timing among the inverters302-306is interleaved.

The inductance on any phase legs of the microinverters302-306can be between 200 μH and 1 mH. In an exemplary embodiment, the inductance can be 800 μH. The system300further comprises a plurality of pulse width modulators314-318that are respectively controlled by control systems320-324. As indicated above, the control systems320-324control the pulse width modulators314-318such that the switch timing among the microinverters302-306is interleaved. In such an exemplary embodiment, the power rating of each of the microinverters can be relatively low, such as between 15 W and 30 W. Additionally, it can be noted that in an MEPV module, because of the relatively low current that flows through each microinverter and because conduction losses are proportional to the current squared, high resistances can be tolerated while keeping conduction losses low. Specifically, an exemplary maximum allowable total resistance within one phase branch of a three-phase integrated inverter, Rbr(max), while maintaining conduction losses below 1.5%, can be estimated as follows:

Rbr⁡(max)≈0.015⁢⁢VLL2Prated(2)
where Pratedis the power rating of the individual integrated circuit microinverter. For instance, a 200 W MEPV module can be outfitted with eight 25 W, interleaved integrated circuit microinverters. Utilizing the equation set forth above, with Prated=25 W while connected to a 208 V or 480 V system, gives 26 ohms and 139 ohms, respectively.

The system300further comprises at least one voltage source, wherein a number of voltage sources is equivalent to a number of AC phases. Further, connections from the inverters302-306are illustrated as single wires; it is to be understood, however, that a number of wires exiting the inverters302-306is equivalent to a number of AC phases.

Now referring toFIG. 4, an exemplary photovoltaic sub-module400that can be included in the photovoltaic module100is illustrated. Pursuant to an example, size of the photovoltaic sub-module400can be between 10 cm and 30 cm in length and between 10 cm and 30 cm in width. The photovoltaic sub-module400comprises a plurality of groups402-440of electrically connected photovoltaic cells, wherein the groups402-440are electrically connected in series. While the photovoltaic sub-module400is shown as including 20 groups, it is to be understood that a number and arrangement of groups in the photovoltaic sub-module400can depend upon a desired voltage output by the photovoltaic sub-module400. Furthermore, while the photovoltaic sub-module400is shown as being a definable physical sub-element of the photovoltaic module100, it should be understood that a photovoltaic sub-module can be defined by a circuit that is employed to connect cells in a solar panel. Both arrangements are intended to fall under the scope of the hereto appended claims.

Pursuant to an example, the photovoltaic sub-module400can comprise approximately 100 groups, wherein each of the groups is configured to output a consistent voltage, for example, approximately 2.4 V. In such example, the desired output of the photovoltaic sub-module400is approximately 240 V. Furthermore, as will be shown in an example herein, some of the groups may be connected in parallel. For instance, the photovoltaic sub-module400can comprise a first plurality of groups that are connected in series and a second plurality of groups are connected in series, wherein the first plurality of groups and the second plurality of groups are connected in parallel.

As shown, a microinverter442, such as the first microinverter104or the second microinverter108, is connected to the sub-module by way of groups402and440, respectively. While shown as being separate from the sub-module400, it is to be understood that the microinverter442can be integrated in the sub-module400. Furthermore, as the photovoltaic module100comprises a plurality of such groups, a plurality of microinverters can be independently coupled to a respective plurality of groups, and such microinverters can subsequently be electrically connected in parallel.

Turning now toFIG. 5, an exemplary group500that can be included as one of the groups402-440in the photovoltaic sub-module400is illustrated. The group500comprises a plurality of photovoltaic cells502-532. Pursuant to an example, the photovoltaic cells502-532can be MEPV cells. For example, the following references which are incorporated herein, by reference, described the building of photovoltaic modules that comprise numerous photovoltaic cells using micro-fabrication techniques: Nielson, et al., “Microscale C-SI (C) PV Cells for Low-Cost Power”, 34thIEEE Photovoltaic Specialist Conference, June 7-10 2009, Philadelphia, Pa., 978-1-4244-2950/90, and Nielson, et al., “Microscale PV Cells for Concentrated PV Applications,” 24thEuropean Photovoltaic Solar Energy Conference, Sep. 21-25, 2009, Hamburg, Germany 3-936338-25-6.

Thus, as mentioned above, the photovoltaic cells502-532can be or include Si cells, GaAs cells, and InGaP cells. Therefore, it is to be understood that at least one of the photovoltaic cells502-532can be III-V photovoltaic cells. Additionally or alternatively, the photovoltaic cells502-532can include at least one Ge cell. Still further, the photovoltaic cells502-532can be, or can be included in multi junction cells that include layers of differing types of photovoltaic cells with differing band gaps. As mentioned above, in an exemplary embodiment, each layer of the multi junction cell can be independently contacted. In another example, a multi junction cell may be contacted at one position, such that voltages of the cells in the multi junction cell are series generated voltages. Thus, in an exemplary embodiment, each of the photovoltaic cells502-532can be multi junction cells, wherein for each multi junction cell, layers are integrally connected. This effectively creates a string of photovoltaic cells electrically connected in series in a relatively small amount of space.

In an exemplary embodiment, the group500can comprise a first string of photovoltaic cells534, a second string of photovoltaic cells536, a third string of photovoltaic cells538, and a fourth string of photovoltaic cells540. The first string of photovoltaic cells534comprises the photovoltaic cells502-508electrically connected in series. Similarly, the second string of photovoltaic cells536comprises photovoltaic cells510-516electrically connected in series. The third string of photovoltaic cells538comprises the photovoltaic cells518-524electrically connected in series, and the fourth string of photovoltaic cells540comprises the photovoltaic cells526-532electrically connected in series. The first string of photovoltaic cells534, the second string of photovoltaic cells536, the third string of photovoltaic cells538, and the fourth string of photovoltaic cells540are electrically connected in parallel.

As will be understood by one skilled in the art, different types of photovoltaic cells have different operating voltages. For instance, if the photovoltaic cells502-532are Ge cells, the operating voltage may be approximately 0.3 V. If the photovoltaic cells502-532are Si cells, then the operating voltage can be approximately 0.6 V. If the photovoltaic cells502-532are GaAs cells, then the operating voltage may be approximately 0.9 V, and if the photovoltaic cells502-532are InGaP cells, then the operating voltage may be approximately 1.3 V. Pursuant to an example, the photovoltaic cells502-532can be Si cells. In such an example, each of the strings of photovoltaic cells534-540outputs approximately 2.4 V (a common voltage), and therefore, the group of photovoltaic cells500is configured to output approximately 2.4 V. In this case, strings534,536,538, and540have different numbers of cells for the different cell types approximating the common voltage. For example, in an exemplary embodiment, the first strings of photovoltaic cells534can include eight Ge cells, the second string of photovoltaic cells536can include four Si cells, the third string of photovoltaic cells538can include three GaAs cells, and the fourth string of photovoltaic cells can include two InGaP cells. Slight voltage mismatch is tolerable, and if desired, a larger number of cells, and a higher voltage, can be used to provide more precise voltage matching. Additionally, power management circuitry can be used independently boost voltages generated by the series connections of different cell types to a common voltage. If the desired output of the photovoltaic module100is approximately 240 V, then the photovoltaic sub-module400can include 100 of the groups500electrically connected in series. Thus, each sub-module in the photovoltaic module100can output approximately 240 V and the output of the photovoltaic module100is thus approximately 240 V. It will be recognized that the configuration of cells, groups, and sub-modules can be arranged to obtain a desired output voltage.

Continuing with the example set forth above, the photovoltaic module100can include 38,400 cells. When an entirety of the photovoltaic module100is illuminated with solar radiation, the photovoltaic cells502-532, in each of the groups, generate approximately 4 mW of electric power.

With reference now toFIG. 6, an exemplary photovoltaic sub-module600that can be included as one of the photovoltaic sub-modules in the photovoltaic module100is illustrated. Pursuant to an example, the photovoltaic sub-module600can comprise a plurality of multi junction photovoltaic cells, such that each multi junction photovoltaic cell comprises a plurality of photovoltaic cells. As discussed above, each multi junction photovoltaic cell can comprise a Si photovoltaic cell and a III-V photovoltaic cell. In a more specific example, each multi junction photovoltaic cell can comprise a Ge photovoltaic cell, a Si photovoltaic cell, a GaAs photovoltaic cell, and an InGaP photovoltaic cell.

The exemplary photovoltaic sub-module600comprises 72 multi junction photovoltaic cells, wherein each of the multi-junction photovoltaic cells comprises a Ge cell, a Si cell, a GaAs cell, and an InGaP cell. These different cells are shown as laid out adjacent to one another; however, such layout is for purposes of explanation. As indicated above, the cells in the multi-junction cells are stacked on top of one another. In another exemplary embodiment, cells can be placed in a side-by-side configuration (e.g. if spectrum spreading optics are used).

The photovoltaic module600comprises different numbers of each cell type connected in series (to create a string) to arrive at similar intermediate (higher) voltages. These strings can be connected in parallel to effectively add currents. In an example, a desired intermediate voltage output by the photovoltaic sub-module600can be approximately 10 V. As discussed above, a Ge cell may have an operating voltage of approximately 0.3 V, a Si cell may have an operating voltage of approximately 0.6 V, a GaAs cell may have an operating voltage of approximately 0.9 V, and an InGaP cell may have an operating voltage of approximately 1.3 V. Therefore, the photovoltaic sub-module600can comprise a first string of Ge cells602and a second string of Ge cells604that each comprises 36 cells electrically connected in series. Accordingly, each of the first string of Ge cells602and the second string of Ge cell604outputs approximately 10.8 V. Further, while not shown, a first microinverter can be connected to the parallel combination of the first string of Ge cells602and the second string of Ge cells604.

The exemplary photovoltaic sub-module600further comprises a first string of Si cells606, a second string of Si cells608, a third string of Si cells610, and a fourth string of Si cells612. Each of the strings of Si cells606-612can comprise 18 cells electrically connected in series resulting in each string outputting approximately 10.8 V. As mentioned above, a microinverter can be electrically connected to the parallel combination of the strings of Si cells.

The sub-module600can additionally comprise a first string of GaAs cells614, a second string of GaAs cells616, a third string of GaAs cells618, a fourth string of GaAs cells620, a fifth string of GaAs cells622and a sixth string of GaAs cells624. Each of the strings of GaAs cells614-624can comprise 12 cells electrically connected in series resulting in each string of GaAs cells outputting approximately 10.8 V. Similar to what has been described above, the parallel combination of the strings of GaAs cells414-424can have a microinverter electrically connected thereto.

Further, the sub-module600can also comprise a first string of InGaP cells626, a second string of InGaP cells628, a third string of InGaP cells630, a fourth string of InGaP cells632, a fifth string of InGaP cells634, a sixth string of InGaP cells636, a seventh string of InGaP cells638, an eighth string of InGaP cells640, and a ninth string of InGaP cells642. Each of the strings of InGaP cells426-442can comprise eight cells electrically connected in series, resulting in each string of InGaP cells outputting approximately 10.4 V. Again, at least one microinverter can be connected to a parallel combination of InGaP cells. The micro-inverters respectively coupled to the strings of different cell types can then be connected in parallel, for example, in an interleaved fashion.

From the above, it can be ascertained that an intermediate operating voltage for each string of cells can be approximately 10 V. It can further be ascertained that voltages output by strings of different cell types are not identical, and thus, the voltage output by the sub-module600will be the lowest voltage output by the string of cells.

Because only one type of cell is initially connected in series, power output from other cells in the sub-module is relatively unaffected by spectral shifts that cause a decrease in output of one type of cell versus another.

With reference now toFIGS. 7-8, exemplary methodologies are illustrated and described. While the methodologies are described as being a series of acts that are performed in a sequence, it is to be understood that the methodologies are not limited by the order of the sequence. For instance, some acts may occur in a different order than what is described herein. In addition, an act may occur concurrently with another act. Furthermore, in some instances, not all acts may be required to implement a methodology described herein.

With reference solely toFIG. 7, an exemplary methodology700for including a three-phase microinverter in a photovoltaic module is illustrated. The methodology700starts at702, and at704, a photovoltaic module that comprises a solar cell is received. At706, a three-phase microinverter is electrically coupled to the solar cell, thereby causing energy generated by the solar cell, when irradiated with solar radiation, to be converted from direct current to three-phase alternating current. As mentioned above, the microinverter can be an integrated circuit that is integrated directly into the photovoltaic module with the solar cell. The methodology700completes at708.

With reference now toFIG. 8, an exemplary methodology800that facilitates utilizing interleaved microinverters in a photovoltaic module is illustrated. The methodology800starts at802, and at804, a photovoltaic module that comprises a plurality of sub-modules is received. Such sub-modules can include, for instance, a plurality of MEPV cells that are electrically connected in series. Additionally, a sub-module can include groups of MEPV cells that are electrically connected in series.

At806, integrated interleaved microinverters are electrically connected to respective sub-modules. Therefore, for example, each sub-module can have a microinverter electrically connected thereto, and the microinverters can be controlled such that they are interleaved. At808, the interleaved microinverters are connected in parallel such that the output of the photovoltaic module is the output of a plurality of parallel interleaved inverters. The methodology800completes at810.

It is noted that several examples have been provided for purposes of explanation. These examples are not to be construed as limiting the hereto-appended claims. Additionally, it may be recognized that the examples provided herein may be permutated while still falling under the scope of the claims.