Photovoltaic module, photovoltaic module array, photovoltaic...

Details Photovoltaic module, photovoltaic module array, photovoltaic... Photovoltaic module, photovoltaic module array, photovoltaic...

1999-03-12

2003-02-04

Pyon, Harold (Department: 1772)

Batteries: thermoelectric and photoelectric

Photoelectric

Panel or array

C136S291000, C136S293000, C323S906000

Reexamination Certificate

active

06515215

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photovoltaic module, a photovoltaic module array, a photovoltaic system (photovoltaic power generation apparatus), and a method of detecting failure of a photovoltaic module.
2. Related Background Art
With the recent spreading use of photovoltaic modules, there is a rapidly growing demand for photovoltaic modules suitable for use in medium-scale electric power systems installed outdoors, particularly in the personal houses. Generally, in the case of using the photovoltaic module for electric power generation, a plurality of the photovoltaic modules are connected in series (hereinafter, referred to as “string”) for generating a voltage not smaller than a certain value, and a plurality of the strings are connected in parallel to form a photovoltaic module array.
FIG. 29
is a circuit diagram showing the constitution of a conventional photovoltaic module. In
FIG. 29
, there are shown a photovoltaic module
1
, a photovoltaics
1
a,
and a bypass diode
1
b
connected parallel to the photovoltaics
1
a.
When a shadow is partly formed on the photovoltaic module
1
thereby increasing the electrical resistance of the photovoltaics
1
a
and causing the application of voltage generated in other modules within the string as an inverse bias to the module
1
(hereinafter, referred to as “partial shadow”), the bypass diode
1
b
prevents the application of an inverse bias to the photovoltaics
1
a
in the photovoltaic module
1
thereby preventing the damage of the photovoltaic cell. Also, when a photovoltaic module which was part of the photovoltaic module array exhibited abnormal output, it was usually necessary, for detecting the position of the failure, to check whether the electrical output is normal in each string, then to interrupt the operation of the photovoltaics-photovoltaic system and to measure the electrical output of each photovoltaic module constituting the string by utilizing the output terminals of each photovoltaic module.
However, since the output terminals are usually provided on the back surface (a surface opposite to a light incident surface) of the photovoltaic module, it was very difficult to locate a failure position by using the output terminals after the installation of the photovoltaic module. On the other hand, if terminals for inspection are provided in each of the modules in such a way that they are exposed to the exterior, they may cause leakage of electricity or danger of electrical shock, thereby causing reliability problems. For these reasons, terminals for inspection were not provided. Consequently, for locating the failed photovoltaic module in a photovoltaic module array, the current flowed in the wiring of the photovoltaic module array is typically measured utilizing a clamping ampere meter.
It is preferable in practical use to have a photovoltaic module provided with current detecting means not exposed to the exterior in order to locate a failed position. An example of such a photovoltaic module includes the photovoltaic module shown in
FIGS. 30A and 30B
, as disclosed in the Japanese Patent Application Laid-Open No. 6-125105 and the photovoltaic module shown in
FIG. 31
, as disclosed in the Japanese Patent Application Laid-Open No. 9-148613. In
FIGS. 30A and 30B
, reference characters
1
c
and
1
d
indicate magnetic field generating means, and in
FIG. 31
reference character
1
e
indicates light emitting means. In the photovoltaic module shown in
FIG. 30A
, a current flows in a bypass diode
1
b
to generate a magnetic field by the magnetic field generating means
1
c.
The photovoltaic module shown in
FIG. 30B
is so constructed that by the electromotive force generated by the photovoltaics
1
a,
an operation current flows into the magnetic field generating means
1
d
to generate a magnetic field. The photovoltaic module shown in
FIG. 31
is so constructed that a current flows into the bypass diode
1
b
to turn on the light emitting means
1
e.
The current detecting means shown in
FIG. 30B
utilizes an operation current c
1
generated during the operation of the photovoltaics
1
a,
while the current detecting means shown in
FIGS. 30A and 31
utilize a current c
2
flowing into the bypass diode
1
b
when the voltage of the photovoltaics
1
a
is lowered.
However, the conventional method of detecting failure of a photovoltaic module array has the following problems. First, when the photovoltaics fails, a current flowing into the bypass diode is generated only when the failure of the photovoltaics is an open circuit failure, and this method cannot be applied to short circuit failure. Second, the failure may not be detected in some cases, depending on the configuration of the photovoltaic module array. This problem becomes more conspicuous when the photovoltaic module array is equipped with a blocking diode for blocking a reverse current.
An open circuit failure means a failure such as an open circuit of the photovoltaic cell itself constituting the photovoltaics, or, in the case of plural photovoltaic cells constituting the photovoltaics, a failure such as breaking of a wiring connecting such photovoltaic cells.
Also, a short circuit failure means a failure such as a short circuit of the photovoltaic cell itself constituting the photovoltaics (including partial short circuit of the photovoltaic cell itself, the same is applied hereinafter), or, in the case of plural photovoltaic cells constituting the photovoltaics, a failure such as the short circuit of the wiring connecting such photovoltaic cells.
Both the open circuit failure and the short circuit failure are modes of failure, and these failure states (modes) are referred to as the open circuit failure mode and the short circuit failure mode, respectively.
The above two problems will be further explained with reference to
FIGS. 32A
to
34
B.
FIGS. 32A and 32B
show the cases of a short circuit failure of the photovoltaics
1
a
in the photovoltaic module. In such situation, regardless of the failure state, a current
2
flows into the failure signal generating means D
1
for detecting the failure by the “absence” of the operation current of the photovoltaics
1
a.
On the other hand, even in the case of a failure state, the current
2
does not flow into the failure signal generating means D
2
for detecting the failure by the “presence” of the current flowing into the bypass diode
1
b.
Distinguishing the failure state from the normal state is not possible in either case, and the failed photovoltaic module in the string cannot be detected.
FIGS. 33A and 33B
show examples of the photovoltaic module array constituted by connecting plural strings in parallel.
FIG. 33A
shows the state in the normal operation, while
FIG. 33B
shows the state in the failure state. Reference character
3
indicates a photovoltaic module array, and
3
c
indicates blocking diodes for preventing loss resulting from the reverse current generated in the case of generating a voltage difference. In such a configuration, when a photovoltaic module
1
A constituting a part of a string
3
a
fails and reaches an open state, the operation current
2
does not flow through the string
3
a
at all, as shown in
FIG. 33B
, if the sum of open circuit voltages Voc
2
+Voc
3
generated in other photovoltaic modules
1
B and
1
C is lower than the sum of operation voltages V
4
+V
5
+V
6
of the string
3
b.
In other words, there is obtained a state that a current does not flow into all the bypass diodes and the photovoltaics constituting the string
3
a.
Consequently, it is not possible to detect the failed photovoltaic module in the string
3
a.
FIGS. 34A and 34B
are circuit diagrams showing an example of the photovoltaics module array formed by connecting in series a plurality of parallel members
3
e
of the photovoltaics.
FIG. 34A
shows the state in the normal operation, while
FIG. 34B
is an equivalent circuit diagram showing a failure state. In
FIG. 34A
, I
1
+I
2
indicates the oper

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