Abstract:
A method for initializing a power inverter of a photovoltaic system includes: opening an AC mains switch and a DC switch to disconnect the power inverter from an electrical grid and to disconnect a capacitor bank associated with the inverter from a solar cell array; closing the AC mains switch to allow power to flow from an electrical grid to the DC capacitor bank to charge the DC capacitor bank; monitoring the DC capacitor bank until a desired voltage is reached; initiating the operation of the power inverter; stabilizing the DC voltage received from the DC capacitor bank at a predetermined power up voltage for the power inverter; waiting for an inverter initialization period to elapse; and adjusting DC voltage received by the power inverter to a voltage associated with a maximum power output level of the solar cell array.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/493,045, filed Jun. 3, 2011, entitled “High Dynamic DC-Voltage Controller for Photovoltaic Inverter.” 
    
    
     BACKGROUND 
     Photovoltaic systems use solar cells to convert light into electricity. A typical photovoltaic system includes a plurality of components, including photovoltaic cells, mechanical and electrical connections, mountings, and controllers for regulating and/or modifying the electrical current produced by the photovoltaic system. 
     The following terms are used herein to describe various components and/or operational aspects of photovoltaic systems: 
     PV photovoltaic 
     DC direct current 
     AC alternate current 
     I SC  short circuit current 
     V OC  open circuit voltage 
     P max  maximum output power of the solar array 
     V max  output voltage of the solar array at maximum output power 
     I max  output current of the solar array at maximum output power 
       FIG. 1  is a block diagram of a conventional photovoltaic power system  100 . The PV power system  100  includes a solar cell array  101  that comprises a plurality of solar cells (also referred to as photovoltaic cells) that convert light into DC voltage. The solar cells are solid state devices that convert the energy of sunlight directly into electricity by the photovoltaic effect. The solar cell array  101  is coupled to a DC switch  102 . The DC switch  102  can be closed to connect the solar cell array  101  to DC capacitor bank  104 , or can be opened to disconnect the solar cell array  101  from the DC capacitor bank  104 . When the DC switch  102  is closed and the solar cell array  101  is generating power, the solar cell array  101  can provide power to charge the DC capacitor bank  104 . 
     The DC capacitor bank  104  is connected to inverter  105 . The inverter  105  converts the DC voltage output from the capacitor bank  104  into 3-phase (or in some cases 2-phase) pulsed AC voltage. The filter  106  converts the pulsed AC voltage output by the inverter  105  into a sinusoidal AC voltage. The sinusoidal AC voltage can then be output to a mains power grid  109 . If an AC mains switch  107  is closed, the sinusoidal AC voltage output by the filter  106  is received by the power transformer  108 . The power transformer  108  adapts the voltage output by the PV system  100  to the grid voltage. This configuration allows the PV system  100  to output electricity onto the mains grid  109 . The voltage output by the photovoltaic system  100  has to be higher than the grid voltage. Inverter  105  may have a mandatory ramp up period where the DC voltage provided by the solar cell array  101  must be gradually ramped up from an initial startup voltage to an operating voltage. 
       FIG. 2  is a graph illustrating the characteristics of a photovoltaic cell. The graph is a current-voltage (I-V curve) for a typical PV cell. V OC  represents the output voltage of the solar cell or array of solar cells where no load is connected to the PV cell or array of cells. In the example illustrated in  FIG. 1 , when the DC switch  102  is open, V OC  represents the output voltage of the solar cell array  101 , because the solar cell array  101  is disconnected from the load (the grid  109 ). 
     The value I SC  represents the current produced by the PV cell or array of cells in the event that there is a short circuit. As can be seen from the graph in  FIG. 2 , there is a maximum voltage V max  where the PV cell or array of cells produces maximum power P max . In a typical photovoltaic system, such as PV power system  100 , the inverter  105  includes a DC voltage controller (not shown) that controls the DC voltage (V DC ) provided by the PV cell or array of cells to operates the PV cell or array of cells at the maximum power point. The grid voltage and the V max  of the PV cell or array of cells typically do not change very quickly, so the DC-voltage controller typically does not have to dynamically respond to rapid changes in these voltages. 
     The following is a typical process for powering up of a photovoltaic system, such a PV system  100 . If the V DC  of the solar array is higher than a predetermined threshold voltage (at least higher than the peak transformer output AC-voltage), the PV system controller closes the DC switch  102  between the DC capacitor bank  104  and the solar cell array  101 . Once the DC switch  102  has been closed, the solar array  101  is operating as a current source and begins to charge the DC capacitor bank  104  according to the specific photovoltaic cell characteristics of the solar array and the DC voltage level being generated. Once the DC capacitor bank  104  has been charged to V OC , the inverter  105  closes the AC mains switch  107 . The peak of the transformer output AC voltage is lower than V OC . At this point, no current is flowing between the solar array and the grid, even though all the switches are closed. Next, the inverter  105  starts to generate AC voltage and the inverter  105  synchronizes its AC output voltage to grid voltage and grid frequency. AC output current of the inverter  105  during this phase of operation is approximately zero. The photovoltaic system is not yet generating power, and the DC voltage is V OC . Once the inverter  105  has begun generating AC voltage and has synchronized its output voltage with the grid voltage, the DC voltage controller of the photovoltaic system begins operation and reduces the DC voltage from V OC  to V max . Change of the DC voltage is generally a very slow procedure.  FIG. 2  illustrates the difference between V OC  and V max . When the DC voltage is at V OC , the system is not generating power, and when the DC voltage is a V max , the system is generating maximum power. 
     The standard power up process described above has several disadvantages. For example, V DC  is one of the key design parameters for photovoltaic systems, especially with respect to the components of the inverter  105  and the DC capacitor bank  104 . The current trend for photovoltaic systems is that the V DC  has been increased to higher values (e.g., in the range of 1000V). A lower V DC  would be preferred from a design standpoint, because the inverter would not have to handle such high voltages. In order to operate at higher voltages, efficiency is compromised. The maximum DC voltage during operation of the inverter is V max , and the voltage level between V max  and V OC  is used only during the power up procedure. 
     One technique that can be used to lower the DC voltage provided by the solar cell array  101  is to introduce a preload into the PV system to lower the voltage provided to the inverter  105  during the ramp up period for the inverter  105 .  FIG. 3  illustrates a PV system  300  that includes a power up preload  303  (also referred to herein as a power up load). The PV system  300  includes a solar cell array  301 , a DC switch  302 , a DC capacitor bank  304 , an inverter  305 , a filter  306 , an AC mains switch  307 , and a power transformer  308 . The power transformer  308  adapts the voltage output by the PV system  300  to the grid voltage. This configuration allows the PV system  300  to output electricity onto the mains grid  309 . 
     The power up sequence for the PV system  300  is slightly different than that of the PV system  100 , because PV system  300  includes the preload  303 . In PV system  300 , the PV system controller closes the DC switch  302  which connects the solar cell array  301  to the power up load  303 . The power up load  303  is disposed between the solar cell array  301  and the DC capacitor bank  304 . The controller of the PV-inverter  305  then closes the AC mains switch  307  until the DC capacitor bank  304  is charged to V power up . The inverter  305  can then start generating AC voltage and the filter  306  begins synchronizing the AC output voltage and to the grid voltage and grid frequency. The power up load  303  is then disabled by the controller of the PV inverter  305 , and the DC voltage controller of the PV system  300  being operating to reduce the DC voltage from V power up  to V max  in order to generate maximum power for the PV system. 
       FIG. 4  illustrates the distinction between operating at V power up  where the power generated by the system equals P power up  and operating at V max  where the power generated by the system equals P max .  FIG. 4  is a graph illustrating the characteristics of a photovoltaic cell that includes the power up operating point. The graph is a current-voltage (I-V curve) for a typical PV cell. V power up  represents the power up voltage and I power up  represent the power up current. As can be seen in  FIG. 4 , the power up voltage falls between the V max  and the V OC  for the PV cell or array of cells. 
     In conventional PV systems, such as those illustrated in  FIGS. 1 and 3 , the inverter may be “overdesigned” to allow the inverter to operate at higher voltages such as the V OC  of the solar cell array, but this approach this sacrifices efficiency of the inverter. Furthermore, adding a preload to the system as suggested in the alternative implementation illustrated in  FIG. 3  can decrease the voltage levels at which the inverter can operate, but this approach adds expense and complexity to the PV system. 
     SUMMARY 
     Techniques are described for powering up an inverter of a photovoltaic system where the inverter includes a high dynamic DC voltage controller. These techniques can allow the inverter of the PV system to operate more efficiently and to avoid the need to include additional equipment, such as a power up load, in the PV system. 
     An example method for initializing a power inverter of a photovoltaic system comprising a solar cell array includes: opening an alternating current (AC) mains switch and a direct current (DC) switch, wherein opening the AC mains switch disconnects the power inverter from an electrical grid, and wherein opening the DC switch disconnects a DC capacitor bank associated with the power inverter from the solar cell array; closing the AC mains switch to allow power to flow from the electrical grid to the DC capacitor bank connected to the power inverter to charge the DC capacitor bank; monitoring the DC capacitor bank until a desired voltage for the DC capacitor bank is reached; initiating the operation of the power inverter such that the power inverter begins to receive DC voltage from the DC capacitor bank; stabilizing the DC voltage received from the DC capacitor bank at a predetermined power up voltage for the power inverter; waiting for an inverter initialization period to elapse; and adjusting DC voltage received by the power inverter to a voltage associated with a maximum power output level of the solar cell array. 
     Implementations of such a method may include one or more of the following features. The desired voltage for the DC capacitor bank is a power up voltage for the power inverter. The DC capacitor bank stores an electrical charge and outputs a DC current to the power inverter. The DC voltage received from the DC capacitor bank at a predetermined power up voltage for the power inverter further comprises stabilizing the DC voltage received at the DC capacitor bank at the power up voltage for the power inverter. The voltage associated with a maximum power output level of the solar cell array is less than the power up voltage for the power inverter. After stabilizing the DC voltage received from the DC capacitor bank at a predetermined power up voltage for the power inverter, closing the DC switch to allow the solar cell array to provide DC power to the DC capacitor bank to charge the DC capacitor bank. Upon initiating operation, converts the DC voltage from the received from the DC capacitor bank to AC voltage that can be output onto the electrical grid. 
     An example controller for a photovoltaic system, the photovoltaic system including a solar cell array, a direct current (DC) capacitor bank, an alternating current (AC) switch, and a DC switch, the controller including: a tangible, non-transitory computer-readable memory, a plurality of modules comprising processor executable code stored in the memory, a processor, and a control interface. The processor is connected to the memory and configured to access the plurality of modules stored in the memory. The control interface configured to send control signals to the AC switch, the DC switch, and the power inverter. The plurality of modules stored in the memory includes: a voltage control module and a control signal module. The voltage control module is configured to cause the processor to perform a method for initializing a power inverter of a photovoltaic system comprising: opening an alternating current (AC) mains switch and a direct current (DC) switch, wherein opening the AC mains switch disconnects the power inverter from an electrical grid, and wherein opening the DC switch disconnects the power inverter from the solar cell array, closing the AC mains switch to allow power to flow from the electrical grid to a DC capacitor bank connected to the power inverter to charge the DC capacitor bank, monitoring the DC capacitor bank until a desired voltage for the DC capacitor bank is reached, initiating the operation of the power inverter such that the power inverter begins to receive DC voltage from the DC capacitor bank, stabilizing the DC voltage received from the DC capacitor bank at a predetermined power up voltage for the power inverter, waiting for inverter initialization period to elapse, and adjusting DC voltage received by power inverter to a maximum voltage associated with a maximum power level of the solar cell array. The control signal module configured to cause the processor to send control signals to the AC switch, the DC switch, and the power inverter. 
     Implementation of the controller may include one or more of the following features. The desired voltage for the DC capacitor bank is a power up voltage for the power inverter. The DC capacitor bank stores an electrical charge and outputs a DC current to the power inverter. Stabilizing the DC voltage received from the DC capacitor bank at a predetermined power up voltage for the power inverter further comprises stabilizing the DC voltage received at the DC capacitor bank at the power up voltage for the power inverter. The voltage associated with a maximum power output level of the solar cell array is less than the power up voltage for the power inverter. After stabilizing the DC voltage received from the DC capacitor bank at a predetermined power up voltage for the power inverter, closing the DC switch to allow the solar cell array to provide DC power to the DC capacitor bank to charge the DC capacitor bank. The power inverter, upon initiating operation, converts the DC voltage from the received from the DC capacitor bank to AC voltage that can be output onto the electrical grid. 
     A system for initializing the power inverter of a photovoltaic system that includes a solar cell array includes: means for opening an alternating current (AC) mains switch and a direct current (DC) switch, wherein opening the AC mains switch disconnects the power inverter from an electrical grid, and wherein opening the DC switch disconnects a DC capacitor bank associated with the power inverter from the solar cell array; means for closing the AC mains switch to allow power to flow from the electrical grid to the DC capacitor bank connected to the power inverter to charge the DC capacitor bank; means for monitoring the DC capacitor bank until a desired voltage for the DC capacitor bank is reached; means for initiating the operation of the power inverter such that the power inverter begins to receive DC voltage from the DC capacitor bank; means for stabilizing the DC voltage received from the DC capacitor bank at a predetermined power up voltage for the power inverter; means for waiting for inverter initialization period to elapse; and means for adjusting DC voltage received by power inverter to a voltage associated with a maximum power output level of the solar cell array. 
     Implementation of the system may include one or more of the following features. The desired voltage for the DC capacitor bank is a power up voltage for the power inverter. The DC capacitor bank stores an electrical charge and outputs a DC current to the power inverter. The means for stabilizing the DC voltage received from the DC capacitor bank at a predetermined power up voltage for the power inverter further comprises means for stabilizing the DC voltage received at the DC capacitor bank at the power up voltage for the power inverter. The voltage associated with a maximum power output level of the solar cell array is less than the power up voltage for the power inverter. Means for closing the DC switch to allow the solar cell array to provide DC power to the DC capacitor bank to charge the DC capacitor bank when the DC voltage received from the DC capacitor bank at a predetermined power up voltage for the power inverter has been stabilized. The power inverter, upon initiating operation, includes means for converting the DC voltage from the received from the DC capacitor bank to AC voltage that can be output onto the electrical grid. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a high level block diagram of a conventional photovoltaic system. 
         FIG. 2  is an I-V curve for a solar cell that illustrates the maximum power point for the solar cell. 
         FIG. 3  is a high level block diagram of another conventional PV system that includes a preload. 
         FIG. 4  is an I-V curve for a solar cell that illustrates the characteristics of a photovoltaic cell and a power up loading operating point. 
         FIG. 5  is a high level block diagram of a PV system that includes a DC controller for the PV inverter of the PV system. 
         FIG. 6  is a block diagram of a DC controller for a PV inverter. 
         FIG. 7  is a block flow diagram of a method for powering up a photovoltaic system. 
     
    
    
     DETAILED DESCRIPTION 
     Techniques are described for powering up an inverter of a photovoltaic system where the inverter includes a high dynamic DC voltage controller. These techniques can allow the inverter of the PV system to operate more efficiently and to avoid the need to include additional equipment, such as a power up load, in the PV system. 
       FIG. 5  is a high level block diagram of a PV system  500 . The inverter  505  of the PV system includes a high-dynamic DC controller  599  that has a fast current control rise time. The PV system  500  includes solar cell array  501 . Solar cell array includes one or more PV cells that generate DC voltage when exposed to light using the photovoltaic effect. The solar cell array  501  is coupled to DC switch  502 . The DC switch  502  can be closed to connect the solar cell array  501  to DC capacitor bank  504 , or opened to disconnect the solar cell array  501  from the DC capacitor bank  504 . The DC controller  599  can be configured to send a control signal to the DC switch  502  to open or close the switch. 
     The DC controller  599  can control the operation of the DC switch  502 . During the power up procedure for the inverter  505 , the DC controller  599  does not close the DC switch  502  and disconnect the solar cell array  501  from the DC capacitor bank  504  to prevent the solar cell array  501  from charging the DC capacitor bank  504 . Instead, the DC controller  599  can cause the DC capacitor bank  504  to be charged from the grid  509  by closing the AC mains switch  507 . A method for implementing a power up procedure for the inverter  505  is illustrated in  FIG. 7  where the DC controller  599  charges the DC capacitor bank  504  from the grid  509  rather than from the solar cell array  501 . By charging the DC capacitor bank  504  from the grid  509  rather than the solar cell array  504  during the startup period for the inverter  505 , the inverter  505  can be designed to operate at lower voltages which can result increased efficiency. This approach also eliminates the need to include an expensive preload to the PV system  500 . 
     The DC capacitor bank  504  is connected to inverter  505 . The inverter  505  converts the DC voltage output from the capacitor bank  504  into 3-phase (or in some cases 2-phase) pulsed AC voltage. The inverter  505  outputs pulsed AC current to a filter  506 . The filter  506  converts the pulsed AC voltage output by the inverter  505  into a sinusoidal AC voltage. The sinusoidal AC voltage can then be output to a mains power grid  509 . 
     The DC controller  599  can also control the operation of AC mains switch  507 . The DC controller  599  can be configured to send a control signal to the AC mains switch  507  to close the AC mains switch  507  to allow the sinusoidal AC voltage output by the filter  506  to be received by the power transformer  508 . The power transformer  508  adapts the voltage output by the PV system  500  to the grid voltage. This configuration allows the PV system  500  to output electricity onto the mains grid  509 . The DC controller  599  can also send a control signal to close the AC mains switch  507  to initiate a power up phase of the inverter  505 . During the power up phase of the inverter  505 , the DC controller  599  will not close the DC switch  502 , to disconnect the DC capacitor bank  504  from the solar cell array  501  and close the AC mains switch  507  to charge the DC capacitor bank  504  through the filter  506  and inverter  505  from the grid  509 . This approach allows the DC controller  599  to charge the capacitor bank  504  from the grid  509 . The DC controller  599  can initialize the operation of the inverter  505  once the DC capacitor bank  504  has been charged to V power up . The DC controller  599  can then stabilize the operating voltage of the inverter  505  at V power up . 
     The DC controller  599  can close the DC switch  502  to allow the solar cell array  501  to provide power to the DC capacitor bank  504  to charge the capacitor bank. The solar cell array  501  can then charge the DC capacitor bank as a current source with a constant current of I power up . The high dynamic DC voltage controller  599  starts immediately with high dynamic to let flow power from the DC capacitor bank  504  over the different parts  505 ,  506 ,  507 ,  508 , of the PV system  500  to the grid  509 . This approach limits transient overshooting of the DC voltage (V Δ ) to very low levels. As a result, the maximum DC voltage for the operation of the inverter  505  is V power up +V Δ . The inverter  505  will not be required to operate at V OC  of the solar cell array  501 . Accordingly, even in systems where the solar cell array  501  has a very high V OC , the operating voltage of the inverter  505  can be closely controlled and kept close to V power  up, which means that the inverter  505  does not need to be overdesigned to handle higher than necessary operating voltages and more efficient inverter components can be used in inverter  505 . 
       FIG. 6  is a block diagram of the high dynamic DC  599  for the inverter  505  of PV system  500 . Controller  599  includes a processor  605 , memory  620 , voltage inputs  635 , voltmeter  630 , and control interface  640 . The memory  620  includes a voltage control module  622  and a control signal module  626 . The memory  620  can comprise one or more types of tangible, non-transitory computer-readable memory, such as random-access memory (RAM), read-only memory (ROM), flash memory, or a combination thereof. The modules can comprise processor-executable instructions that can be executed by processor  605 . 
     The processor  605  can comprise one or more microprocessors configured to access memory  620 . The processor  605  can read data from and write data to memory  620 . The processor  605  can also read executable program code from memory  620  and execute the program code. 
     The voltage inputs  635  provide an interface through which the controller  599  can monitor voltages throughout the photovoltaic system  500 . For example, the voltage inputs  635  can be used to monitor the grid voltage (V grid ), the DC voltage (V DC ) provided by the solar cell array  501 , and/or the voltage of the DC capacitor bank  504 . Voltmeter  630  can be used to determine the voltage of the various inputs being monitored using the voltage inputs  635 . The voltmeter  630  may be an external voltmeter and the controller  599  can be configured to receive a signal from the external voltmeter that monitors the grid voltage (V grid ), the DC voltage (V DC ) provided by the solar cell array  501 , and/or the voltage of the DC capacitor bank  504 . 
     The processor  605  can send control signals to one or more external devices via control interface  640 . For example, control interface  540  can be connected to AC mains switch  507  and DC capacitor bank  504  and can sent control signals to each of the switches to open and close the switches. The control interface can also sent a control signal to the inverter  504  to initiate a power up sequence of the inverter. The control interface  640  can be configured to provide wired connections, wireless connections, or a combination thereof for controlling the AC mains switch  507  and the DC capacitor bank  504 , and for communicating with the inverter  505 . 
     The voltage control module  622  can include executable code that causes the processor  605  to perform a power up method for inverter  505  of a PV system  500 . The voltage control module  622  can be configured to perform the steps described in the method of  FIG. 7  when the inverter  505  is powered up. The voltage control module  622  can instruct the control signal module  626  to open and close the AC mains switch  507  and the DC switch  502  to control the flow of power through the PV system  500 . The voltage control module  622  can also instruct the control signal module  626  to send control signals to the inverter  505 . For example, the voltage control module  622  can instruct the control signal module  626  to send a control signal to the inverter  505  to stop operation, to start operation, or to enter into a power up mode. 
     The control signal module  626  can include executable code that can cause the processor  605  to instruct the control interface  640  to send a command to one or more external devices, such as the AC mains switch  507 , the DC capacitor bank  504 , and the inverter  505 . For example, the control signal module  626  can send a signal to the AC mains switch  507  to close the switch to provide a connection from the grid  509  to the inverter  505  or the control signal module  626  can send a signal to the AC mains switch  507  to open the switch to disconnect the grid  509  from the inverter  505 . The control signal module  626  can send a signal to the DC switch  502  to close the switch to provide a connection from the solar cell array  501  to the DC capacitor bank  504  or the control signal module  626  can send a signal to the DC switch  502  to open the switch to disconnect the solar cell array  501  from the DC capacitor bank  504 . 
       FIG. 7  is a block flow diagram of a method for powering up an inverter of a photovoltaic system. The method for powering up a PV system illustrated in  FIG. 7  can be implemented by voltage control module  622  of the controller  599  of PV system  500 . In the method illustrated in  FIG. 7 , the DC capacitor bank  504  can be charged with power from the grid and the inverter  505  is operating with his high dynamic DC-voltage controller  599  before the DC switch  502  is closed. 
     The controller  599  of the inverter  505  can then open the DC switch  502  and the AC switch  507  (step  705 ). The solar cell array  501  may be generating high DC voltage at this point, but because the DC switch  502  is open, the solar cell array  501  cannot charge the DC capacitor bank  504  up to this high voltage. Also, because the AC mains switch  507  is open, PV system  500  is disconnected from the power grid  509  and is not providing power to or receiving power from the grid  509 . 
     The AC mains switch  507  can then be closed to connect the inverter  505  to the grid  509  (step  710 ). Power from the grid  509  can now reach the inverter  505  that includes the high dynamic DC voltage controller. The inverter  505  can allow current from the grid to flow into the DC capacitor bank  504  to charge the DC capacitor bank  504 . The inverter converts the AC power from grid into DC power that can charge the capacitor bank  504 . This approach utilizes power from the grid to charge the capacitor bank  504  rather than relying on DC current provided by the solar cell array  501 . The inverter  505  is not operating at this point to convert DC to AC power. 
     The DC voltage controller can monitor the voltage of the capacitor bank  504  (step  715 ), and make a determination whether a desired voltage is reached (step  717 ). If the desired voltage has not yet been reached, the controller  599  can continue to monitor the voltage of the capacitor bank. In one example, the capacitor bank  504  can be charged to V power up , where V power up  is a desired for powering up the inverter  505 . As can be seen in  FIG. 4 , V power up  is less than V OC  but is greater than V max . Operating at V power up  will place less of a strain on the inverter  505  than if the inverter  505  were operating at V OC . The inverter  505  would not need to be overdesigned to handle the higher voltage. Overdesigned systems have lower efficiency and higher complexity than systems that are not overdesigned. 
     Once the DC capacitor bank has reached the desired charge level, the DC voltage controller can initiate the operation of the inverter  505  (step  720 ). The inverter  505  begins to operate and draw current from the DC capacitor bank  504  to start generating AC power and the filter  506  begins synchronizing the AC output from the inverter  505  to the voltage and frequency of the grid  509 . 
     The DC voltage controller then stabilizes the DC voltage of the system at power up voltage. V power up  (step  725 ). The DC voltage controller can the close the DC switch  502  (step  730 ). Closing the DC switch allows DC power provided by the solar cell array  501  to charge the DC capacitor bank  504 . The solar cell array  501  can now charging the DC capacitor bank as a current source with a constant current I power up . 
     The DC voltage controller  599  can the wait for the inverter startup period to elapse (step  735 ) before adjusting the DC voltage from V power up  to V max  to allow the PV system  500  to generate as close to maximum power from the solar cell array  501  as possible (step  740 ). 
     The highly dynamic DC voltage controller keeps transient overshooting of DC voltage (V Δ ), caused by the power generated by the solar cell array  501  after closing the DC switch  502 , very low. As a result, the maximum DC voltage for the inverter operation is V power up +V Δ . Additional equipment, such as a preload, can be eliminated even where the solar cell array  501  has a very high V OC . Furthermore, because the operating voltages of the inverter  505  have been reduced, the inverter  505  can use higher efficiency components. 
     Those of skill will appreciate that the various illustrative logical blocks, modules, and algorithm steps described in connection with the embodiments disclosed herein can often be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the design constraints imposed on the overall system. Skilled persons can implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the invention. In addition, the grouping of functions within a module, block or step is for ease of description. Specific functions or steps can be moved from one module or block without departing from the invention. 
     The various illustrative logical blocks and modules described in connection with the embodiments disclosed herein can be implemented or performed with a general purpose processor, a digital signal processor (DSP), application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor can be a microprocessor, but in the alternative, the processor can be any processor, controller, microcontroller, or state machine. A processor can also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. 
     The steps of a method or algorithm described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium. An exemplary storage medium can be coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor. The processor and the storage medium can reside in an ASIC. 
     While the foregoing disclosure shows illustrative aspects and/or embodiments, it should be noted that various changes and modifications could be made herein without departing from the scope of the described aspects and/or embodiments as defined by the appended claims. For example, for enhanced security, it should be noted that data stored on wireless device and/or data stored on remote server may be stored in an encrypted format. Furthermore, although elements of the described embodiments may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated. Additionally, all or a portion of any aspect and/or embodiment may be utilized with all or a portion of any other aspect and/or embodiment, unless stated otherwise.