Patent Application
20110156484
The invention relates generally to a photovoltaic (PV) power system, more particularly, to a reliable photovoltaic power system employing smart virtual low voltage photovoltaic modules.
Recently, the photovoltaic industry has been growing to meet an increasing need for electricity. The continuous challenge in the photovoltaic industry is to develop and manufacture photovoltaic power systems having a high efficiency for converting solar energy into electrical energy. The more efficient the photovoltaic system is at performing such a conversion, the greater amount of electricity can be generated for a given investment.
Additionally, a photovoltaic power system utilizing photovoltaic modules having low output voltages is more favorable, because such low-voltage PV modules can provide many advantages including lower wiring costs and easier string design. However, conventional thin film amorphous silicon PV modules often have high output voltages (greater than 20V) and therefore cannot meet the requirements for low manufacturing costs and easier design.
Additionally, since PV power systems are generally mounted outdoors, they need to have high environment resistance reliability. However, conventional PV systems available suffer poor reliability owing to operation failures of the conventional modules caused by various uncertainties.
In view of above, a reliable PV power system utilizing smart virtual low voltage photovoltaic modules is provided, which can provide advantages such as reduced wire costs and easier design due to the employment of the smart virtual low voltage photovoltaic modules. Additionally, the reliable PV power system can circumvent mismatch problems and can thus have high conversion efficiency. Additionally, the reliable PV power system can provide improved reliability and thus can operate against component failure scenarios caused by various uncertainties.
In accordance with an embodiment, a reliable photovoltaic (PV) power system comprises a plurality of smart virtual low voltage PV modules arranged in a plurality of columns and a plurality of rows, wherein the smart virtual low voltage PV modules on the same column are connected in series, and the smart virtual low voltage PV modules on the same row are connected in parallel. Additionally, each of the smart virtual low voltage PV modules comprises one or more photovoltaic cells, configured to convert solar energy into DC power; and a DC/DC converting unit, coupled to the PV module, configured to communicate with a control center to acquire from the control center a determined level value, thereby converting the DC power received from the PV module into a demanded output voltage having the determined level value.
These and other features, aspects, and embodiments are described below in the section entitled “Detailed Description of the Invention.”
Features, aspects, and embodiments are described in conjunction with the attached drawings, in which:
Additionally, the PV power system 100 can comprise a plurality of bypass diodes 112(1)-112(n), each connected in parallel with a corresponding one of the smart virtual low voltage PV modules 110(1)-110(n). With the parallel connection, the bypass diode 112(i) can provide a bypass path to the corresponding PV modules 110(i) if the corresponding PV modules 110(i) fails to operate normally.
Additionally, the PV power system 100 can further include an inverter 120 coupled between the string of the smart virtual low voltage PV modules 110(1)-110(n) and a load such as a power grid (not shown). The inverter 120 is configured to convert a system output voltage Vs provided by the string of the smart virtual low voltage PV modules 110(1)-110(n) into an AC (alternating current) voltage VAC for output to the load.
Additionally, the PV power system 100 can include or can be coupled externally to the control center 130, which can communicate with and thereby control each of the smart virtual low voltage PV modules 110(1)-110(n). Preferably, the control center 130 can perform the determination based on a condition that each normally-operating smart virtual low voltage PV module operates with an instantaneous maximum power production (i.e., at a respective instantaneous maximum power point). More preferably, the control center 130 can perform the determination based on another condition that the system output voltage Vs provided by the normally-operating ones in the smart virtual low voltage PV modules 110(1)-110(n) is equal to a predetermined voltage, e.g., an optimal input voltage of the inverter 120.
Benefiting by the implementation of the bypass diodes 120(1)-120(n) that can provide bypass paths for the corresponding smart virtual low voltage PV modules 110(1)-110(n), respectively, even if any one or more of the smart virtual low voltage PV modules 110(1)-110(n) fail to operate normally, no open circuit (or break circuit) will occur to result in an entire operation failure of the string of the smart virtual low voltage PV modules 110(1)-110(n).
Accordingly, no matter whether all of the smart virtual low voltage PV modules 110(1)-110(n) are normally operating or not, the control center 130 can still communicate with the ones among the smart virtual low voltage PV modules 110(1)-110(n) that are still normally-operating, and determine the level value of the respective demanded output voltage for each normally-operating smart virtual low voltage PV module. Consequently, the PV power system 100 can operate against component failure scenarios caused by various uncertainties.
It is noted that although the bypass diode 112(i) in the embodiment is connected externally to the smart virtual low voltage PV module(i), it is only for purpose of illustration without limiting the protection scope of the present invention. For example, in an alternative embodiment, the bypass diode 112(i) can be integrated with the smart virtual low voltage PV module(i).
Additionally, it should be noted that although in the embodiment of
In the embodiment, the control center 130 performs the determination such that each normally-operating smart virtual low voltage PV module operates with an instantaneous maximum power production, and the smart virtual low voltage PV modules that are still operating normally can provide a system output voltage Vs equal to a predetermined voltage (e.g., an optimal input voltage of the inverter 120).
As shown in
Next, in step 220, the control center 130 can calculate a total maximum power value “Ps” by summing the respective maximum power value “Pmp(j)” of each normally-operating smart virtual low voltage PV module 110(j). As an example, the total maximum power value Ps is equal to Pmp(1)+Pmp(2) if only the smart virtual low voltage PV modules 110(1) and 110(2) are still normally operating.
Next, the method 200 enters step 230, where the control center 130 can calculate a string current “Is” as: Is =PsNs, where Vs is the system output voltage equal to a predetermined voltage (e.g., an optimal input voltage for the inverter 120) as described above.
Next, in step 240, the control center 130 can determine the level value of the respective output voltage VOD(j) for each normally-operating smart virtual low voltage PV module 110(j) as: VOD(j)=Pmp(j)/Is.
As a result, regardless of whether all of the smart virtual low voltage PV modules 110(1)-110(n) are normally operating or not, and whether the smart virtual low voltage PV modules 110(1)-110(n) are matched to each other or not, not only can each normally-operating smart virtual low voltage PV modules operate at respective maximum power point to provide maximum power production, but also all normally-operating smart virtual low voltage PV modules can collectively provide the system output voltage Vs optimal for input to the inverter 120. In other words, the reliable PV power system 100 can provide reliability against component failures, while circumventing mismatch problems between PV modules and providing high conversion efficiency.
The PV power system 300 differs from the PV power system 100 of
As shown, the smart virtual low voltage PV modules 310(i,1)-310(m,n) can be arranged in a plurality of columns C(1)-C(m) and a plurality of rows R(1)-R(n). The smart virtual low voltage PV modules 310(i,1)-310(i,n) on the same column C(i) (where 1≦i≦m) are connected in series as a string. Additionally, the smart virtual low voltage PV modules 310(1,j)-310(m,j) on the same row R(i) (where 1≦j≦n) are connected in parallel.
Similar to that in
Because the smart virtual low voltage PV modules 310(1,j)-310(m,j) on the same row R(j) are connected in parallel, the output demanded output voltages VOD(1,j)-VOD(m,j) can be equal to the same level (hereafter denoted as “VODR(j)”). Namely, VODR(j)=VOD(1,j)=VOD(2,j)= . . . =VOD(m,j). Detailed architecture and operation of each of the smart virtual low voltage PV modules 310(1,1)-310(m,n) are described with reference to the descriptions in connection with an embodiment illustrated with
With such a connection configuration, the smart virtual low voltage PV modules 310(1,j)-310(m,j) on the same row R(j) can provide bypass paths mutually to each other if any one or more of them fail to operate normally. This means that each of the smart virtual low voltage PV modules 310(1,j)-310(m,j) on the row R(j) can have (m=1) bypass paths provided by the other smart virtual low voltage PV modules on the same row.
Accordingly, the PV power system 300 can operate against component failure scenarios caused by various uncertainties. Only when all of the P(1,j)-P(m,j) on the same row R(j) fail to operate normally will an open circuit (or break circuit) occur in the row R(j) to result in an entire operation failure of the smart virtual low voltage PV modules 310(1,1)-310(m,n). With the increase of the total number “m” of the columns, the system reliability can be increased.
Consequently, compared with the PV power system 100 of
Additionally, the PV power system 300 can further include an inverter 320 coupled between the smart virtual low voltage PV modules 310(1,1)-310(m,n) and a load such as a power grid (not shown). The inverter 320 is configured to convert a system output voltage Vs provided by the smart virtual low voltage PV modules 310(1,1)-310(m,n) into an AC voltage VAC for output to the load.
Additionally, the PV power system 300 can include or can be coupled externally to the control center 330, which can communicate with and thereby control each of the smart virtual low voltage PV modules 310(1,1)-310(m,n).
Preferably, the control center 330 can perform the determination based on a condition that each normally-operating smart virtual low voltage PV module operates with an instantaneous maximum power production (i.e., at a respective maximum power point). More preferably, the control center 330 can perform the determination based on another condition that the system output voltage Vs provided by the smart virtual low voltage PV modules 310(1,1)-310(m,n) is equal to a predetermined voltage, e.g., an optimal input voltage of the inverter 320.
Similarly, no matter whether all of the smart virtual low voltage PV modules 310(1,1)-310(m,n) are normally operating or not, the control center 330 can still communicate with the ones among the smart virtual low voltage PV modules 310(1,1)-310(m,n) that are still normally-operating, and determine the level value of the respective demanded output voltage for each normally-operating smart virtual low voltage PV module.
As shown, the method 400 is started at step 410 which is similar to step 210 of
Next, in step 420 which is similar to step 220 of
Next, the method 400 enters step 430 which is similar to step 230 of
Next, in step 440, the control center 330 can determine the level value of the respective output voltage VODR(j) for each row R(j) as: VODR(j)=PRmp(j)/Is, where PRmp(j) denotes a sum of the maximum power values of the normally-operating smart virtual low voltage PV modules on the same row R(j). For example, in the case where only the smart virtual low voltage PV modules 310(1,1) and 310(2,2) are still normally operating, PRmp(1)=Pmp(1,1), and PRmp(2)=Pmp(2,2). Accordingly, the level value of the respective demanded output voltage of each normally-operating smart virtual low voltage PV module on the row R(j) can be determined to be equal to the determined level value of VODR(j) as described in connection with
As a result, regardless of whether all of the smart virtual low voltage PV modules 310(1,1)-310(m,n) are normally operating or not, and whether the smart virtual low voltage PV modules 310(1,1)-310(m,n) are matched to each other or not, not only can each normally-operating smart virtual low voltage PV modules operate at respective maximum power point, all normally-operating smart virtual low voltage PV modules can collectively provide the system output voltage Vs optimal for input to the inverter 320. In other words, the reliable PV power system 300 can provide reliability against component failures, while circumventing mismatch problems between PV modules and thus providing high conversion efficiency.
As shown, the smart virtual low voltage PV module 500 can comprise a PV module 520 and a DC/DC converting unit 530. The PV module 520 is configured to convert solar energy into DC power for output to the DC/DC converting unit 530. The DC/DC converting unit 530, coupled to the PV module 520, is configured to communicate with a control center 540 to acquire a level value determined by the control center 540, thereby converting the DC power output from the PV module 520 into a demanded output voltage VOD having the level value.
The MPPT 532, coupled to the PV module 520, is configured to track a maximum power operation point for the DC power output by the PV module 520, thereby maximizing the DC power transferred from the PV module 520. The DC/DC step down converter 534, coupled between the MPPT 532 and the controller 536, is configured to convert a DC input voltage VID generated from the MPPT 532 into the demanded output voltage VOD in accordance with a control of the controller 536. The controller 536, coupled between the DC/DC step down converter 534 and the control center 540, is configured to determine a voltage conversion ratio for the DC/DC step down converter 534 in accordance with the control of the control center 540. The controller 536 can preferably have a wireless communication interface 536a having wireless communication capability with the control center 540. With such a configuration, the DC/DC converting unit 530 can convert the DC input voltage VID into the demanded output voltage VOD having a level value determined by the control center 540.
Because the level of the demanded output voltage VOD in the smart virtual low voltage PV module 500 can be lower than that in conventional technologies employing a typical PV module to directly output an output voltage to an inverter without any conversion, the PV power systems 100 and 300 employing such smart virtual lower voltage PV modules can have reduced wiring costs and have achieved an easier design. More details of the architecture and operation of a smart virtual low voltage PV module applicable to the PV power system of
While certain embodiments have been described above, it will be understood that the embodiments described are by way of example only. Accordingly, the device and methods described herein should not be limited to the described embodiments. Rather, the device and methods described herein should only be limited in light of the claims that follow when taken in conjunction with the above description and accompanying drawings.
| Number | Date | Country | |
|---|---|---|---|
| 61291225 | Dec 2009 | US |
