Patent Grant
7514931
1. Field of the Invention
The present invention relates to a solar simulator and a method for driving the same. In particular, the present invention relates to a solar simulator for generating light from a xenon arc lamp, which is preferable in measurement of the output characteristic of photovoltaic devices, as pseudo sunlight, and also to a method for driving such a solar simulator.
2. Description of the Related Art
As the importance of photovoltaic devices as clean energy is being widely recognized, the demand for such devices is increasing. The demand is coming from a variety of fields, from power energy supplies for large-scale machines to small-scale power supplies for precise electronic machines.
Here, in order for photovoltaic devices to be widely used in a variety of fields, accurate measurement of the characteristics, in particular, the output characteristic, of the photovoltaic devices is necessary, as many problems would otherwise be expected to arise where the photovoltaic devices is used. Therefore, conventionally, a solar simulator for measuring the output characteristic of photovoltaic devices has been proposed, and actually used (see Japanese Patent Publication No. Hei 6-105280).
When the output characteristic of photovoltaic devices is measured using such a solar simulator, in particular, when the output characteristic of large-scaled photovoltaic devices having the size (the area of an test plane) of 1 m×1 m or larger is measured, for example, it is necessary to use a solar simulator having a plurality of xenon arc lamps arranged therein. That is, where the amount of light emitted from a single xenon arc lamp presents the irradiance distribution schematically shown in
In addition, there are a variety of shapes (external shape) available, including a shape that is long in the lateral direction, as the shape of large-scaled photovoltaic devices, and with respect to large-scale photovoltaic devices having the size of 1 m×4 m, for example, a solar simulator having two xenon arc lamps each about 2,000 mm long arranged therein is used for the measurement of the output characteristic thereof.
In
However, a solar simulator having a plurality of xenon arc lamps as a light source suffers from a problem that an expected amount of light is not readily and stably obtained from each xenon arc lamp and therefore uniform irradiance over the test plane is not readily ensured.
As for the light emission circuit of a conventional solar simulator which has xenon lamps as a light source, when the solar simulator is constructed having a plurality of xenon lamps to produce light emission therefrom, a problem is expected in that the entire structure is resultantly enlarged as such a light emission circuit (in particular, a power supply device contained therein) is provided for each lamp and therefore a large space within the solar simulator is occupied by the light emission circuits.
Provision of an individual light emission circuit for each lamp leads to another problem that uniform irradiance is not readily ensured over the test plane relative to large-scale photovoltaic devices as the amount of light irradiated from each of the lamps may vary as time passes.
Here, a capacitor used as a power supply of a solar simulator in which a single light emission circuit is used to produce light emission from a single lamp is required to have comparable withstand voltage and a commercially available typical capacitor having such a withstand voltage is of a few μF to a few tens of μF. Therefore, when such a commercially available capacitor is used, the produced light emission can last at most for about 1 millisecond.
Moreover, as the amount of light emitted from the xenon arc lamp may vary when the capacitor discharges, depending on the voltage variation according to the discharge curve of the capacitor, this also makes it difficult to stably obtain a constant amount of light. In actual fact, in measurement of the output characteristic of photovoltaic devices, light emission is attempted from a few tens of times to about one hundred and thirty times for a single photovoltaic devices to be measured.
Therefore, in such a situation, it is more difficult, or sometimes even impossible using a conventional technique, to ensure uniform irradiance when the output characteristic of large-scale photovoltaic devices is measured while producing light emission from a plurality of lamps.
In measurement of the output characteristic of photovoltaic devices which is slow in response, light emission is required to be continued for from a few hundred microseconds to a few seconds. A light emission circuit capable of such prolonged light emission is constructed having a main discharge voltage supply prepared in the form of a large-scale high capacity power supply.
Here, suppose that the light source lamp is a xenon arc lamp in which discharge electrodes are situated apart from each other by a distance of about 1000 mm, for example, an electrical potential of about 2000 V to 3000 V is required, and a current of about 30 A flows in the main discharge. A power supply which meets the specifications of this high electrical potential and current is a large-scale power supply of about 60 KW to 90 KW.
Therefore, a conventional light emission circuit capable of measuring the output characteristic of large-scale photovoltaic devices, which requires light emission from a plurality of lamps, inevitably has a large-scale power supply device. As a result, the solar simulator is resultantly enlarged with related device cost accordingly increased.
The present invention has been conceived in view of the above-described various problems of a conventional solar simulator, and aims to provide a solar simulator having a plurality of xenon arc lamps as a light source, in which an expected amount of light is stably obtained from each of the xenon arc lamps so that uniform irradiance is ensured over the test plane.
Another object of the present invention is to provide a solar simulator capable of stable long-pulse light emission produced from one or more xenon arc lamps without enlarging the device.
Still another object of the present invention is to provide a solar simulator capable of measuring the output characteristic of large-scale photovoltaic devices (for example, 1 m×1 m or over) while lighting a plurality of lamps using a small-scale power supply, without causing irregularity in irradiance over the test plane, and also capable of presenting innovative capability for enhancing measurement accuracy.
In order to solve the above described problems, according to one aspect of the present invention, there is provided a solar simulator, comprising: a plurality of xenon arc lamps; a plurality of light amount sensors provided on the basis of one for each of the xenon arc lamps; and a plurality of control circuits provided on the basis of one for each of the xenon arc lamps, for controlling a current flowing through, or a voltage applied to, each of the xenon arc lamps, wherein a detection signal output from each of the light amount sensors is fed back to each of the control circuits to control the relevant control circuit, to thereby control an amount of light emitted from each of the xenon arc lamps.
In the above, the detection signal output from each of the light amount sensors may be weighted and combined before being fed to each of the control circuits.
According to another aspect of the present invention, there is provided a solar simulator having a light emission circuit for concurrently or selectively lighting one or more xenon arc lamps, wherein the light emission circuit comprises a first power supply for applying electrical potential to destroy an electrically insulated state held between electrodes of each of the xenon arc lamps, a second power supply for applying electrical potential to trigger main discharge after application of the electrical potential to destroy the electrically insulated state held between electrodes of each of the xenon arc lamps, and a third power supply for maintaining the electrical potential required based on electrical resistance within a tube inside each of the xenon arc lamps and a current for main discharge, after the main discharge begins, and further maintaining the current of the main discharge.
Here, the third power supply may include a stabilizing power supply. Also, the third power supply may include a capacitor which is charged by the stabilizing power supply.
Also, a light amount sensor may be provided for each of the one or more xenon arc lamps, and a detection signal output from each of the light amount sensors may be fed back to a current control circuit or a voltage control circuit provided one for each of the xenon arc lamps to control the control circuit, whereby an amount of light emitted from each of the xenon arc lamps is controlled.
In the above, the detection signal output from each of the light amount sensors may be weighted and combined before being fed to each of the control circuits.
According to still another aspect of the present invention, there is provided a method for driving a solar simulator, comprising controlling light emission produced from each of a plurality of xenon lamps of a plurality of solar simulators each having at least one xenon lamp, the light emission being produced using a power supply circuit comprising the second power supply and the third power supply selected from the power supplies described above, to thereby drive the plurality of solar simulators.
In order to measure the output characteristic of large-scale photovoltaic devices having an external size of 1 m×1 m or larger, for example, a solar simulator to be used in the measurement needs to have a structure in which a plurality of xenon arc lamps are provided.
According to the present invention, in this case, a light amount sensor is provided for each of the lamps, so that a detection signal output from each of the light amount sensors is fed to each of the current or voltage control circuits provided for each of the lamps, to thereby control the control circuit. This makes it possible to stabilize the amount of light emitted from each of the lamps. It is therefore possible to realize uniform irradiance over the irradiation surface of the photovoltaic devices to be measured, and therefore highly accurate measurement.
In addition, light emission from the xenon arc lamp is produced using a power supply circuit which comprises the second power supply and the third power supply. This enables stable long-pulse light emission from one or more xenon arc lamps, without enlarging the device.
In particular, as the light emission circuit to light the plurality of xenon arc lamps is constructed having the above-described structure, the power supply itself can be prepared for lower cost as use of a single power supply unit is sufficient. Moreover, such a structure enjoys the benefit of size reduction, as well as remarkable size reduction of the solar simulator for measuring the output characteristic of large-scale photovoltaic devices, compared to the case where a light emission circuit having a conventional structure is used.
In addition, according to the present invention, a plurality of xenon arc lamps are lit using a single power supply circuit which is constructed comprising the second power supply and the third power supply. This can realize a manner of measurement in which the plurality of solar simulators are driven using a single power supply circuit.
Therefore, as the photovoltaic devices is mass-produced, reduction of an area required for installation and simplification of power feeding equipment are attained, compared to a case where a plurality of solar simulators are installed.
In the following, an exemplary embodiment according to the present invention will be described while referring to the accompanied drawings.
Initially, the embodiment 1 of a light emission circuit in a solar simulator according to the present invention will be described while referring to
In
In
As the xenon arc lamps 41 through 4n shown, any xenon arc lamp is applicable as long as the lamp has a structure in which the discharge electrodes are situated apart from each other by a distance equal to or longer than 100 mm and an electrical potential to destroy the electrically insulated state held between the electrodes 4a and 4b can be applied from the outside of the glass tube.
As the lamp light emission power supply circuit 10, a known lamp light emission power supply circuit, such as is shown in
In this embodiment, as light emission is to be produced from a plurality of xenon arc lamps 41 through 4n, one of the wires on the secondary side of the transformer 1b in the first power supply 1 may be branched so as to correspond to the plurality of lamps 41 through 4n, as shown in
Further, in this embodiment, in order to monitor the amount of light emitted from each of the xenon arc lamps 41 through 4n, a light amount sensor S1 through Sn, which may be formed using a photovoltaic cell or the like, as one example, is mounted to each of the respective xenon arc lamps 41 through 4n, so that output signals from the sensors S1 through Sn are fed back to the relevant current control circuits 7 of the xenon arc lamps 41 through 4n as shown in
In the following, in connection with the embodiment 1 of the light emission circuit for the xenon arc lamps 41 through 4n, an operation thereof will be described.
Initially, in response to a manual operation by an operator of a solar simulator to press an activation button or the like, a charge start signal is applied to the capacitor C or capacitors C1 through C3 in the power supply circuit 10 shown in
In response to the lighting start signal 1c applied to the trigger pulse generation circuit 1a, a trigger pulse of a few KV is applied from the secondary side of the output transformer 1b to the external periphery of the glass tube of each of the xenon arc lamps 41 through 4n. With the application of the trigger pulse, the electrically insulated state held between the opposing electrodes 4a and 4b inside each of the xenon arc lamps 41 through 4n is destroyed.
Thereafter, the lamp light emission power supply circuit 10 shown in
In the embodiment 2 of the light emission circuit according to the present invention, as shown in
While referring to
In
Above the lamps 41 through 44, an optical filter 13 or the like is arranged so as to horizontally traverse the inside of the enclosure 11 such that the constant amount of light emitted from the lamps 41 through 44 irradiates the measurement surface 11a (namely, the test plane 11a) when the lamps 41 through 44 are turned on. As an example, photovoltaic devices of about 2 m×4 m may be placed on the measurement surface 11a and measured.
Here, in the inside of the enclosure 11, four light amount sensors S1 through S4 are arranged on the inside surfaces of the circumferential walls 11b so as to correspond to the respective lamps 41 through 44. Also, at a predetermined position on the measurement surface 11a, an irradiance measurement reference cell Sm according to a standard is mounted. A detection signal output from each of the sensors S1 through S4 is fed back to the current control circuit 7 or the voltage control circuit 8 of each of the lamps 41 through 44, so that control is performed such that a constant current or voltage is applied to each of the respective lamps 41 through 44 so that the lamps 41 through 44 can maintain constant irradiance.
In
In the example shown in
Here, the sensors S5, S6, S7 receive not only the light emitted from the respectively corresponding lamps 45, 46, 47 but also the light emitted from other lamps. Therefore, a feedback signal which is created by weighting and combining the detection signals output from the three sensors S5 through S7 is fed to each of the current or voltage control circuits 7 or 8 of the lamps 45 through 47. For example, a signal Fs to be fed back to the current control circuit 7 or the voltage control circuit 8 of the xenon arc lamp 45 is obtained as
Fs=α×(output signal from the light amount sensor S5)+β×(output signal from the light amount sensor S6)+γ×(output signal from the light amount sensor S7)
wherein, α, β, and 0 γ are weighting variables.
The lamps 46 and 47 also each receive a feedback signal created in the same manner as that for the signal Fs. A feedback signal created through the above-described weighting and combining is similarly applicable to the solar simulator shown in
As a lamp light emission power supply circuit of a solar simulator, a lamp light emission power supply circuit according to the present invention shown in
While referring to
Initially, a lighting start signal 1c is applied to the trigger pulse generation circuit 1a (the first power supply 1). The input of the lighting start signal 1c is achieved by a start signal which is output in response to a manual operation by the operator who operates the solar simulator to press an activation button or the like. Alternatively, in the case of an automatic operation such as an automatic driving, the start signal is output from a control device such as a personal computer.
It should be noted that the switch SW, which remains open, is initially closed, and, after the lighting start signal 1c is output, the lamp begins light emission, and a predetermined period of time (about 100 milliseconds to a few seconds) is passed, becomes open again.
When the lighting start signal 1c shown in
This process triggers main discharge inside each of the tubes of the lamps 41 through 4n, upon which the inside-tube resistance of each of the xenon arc lamps 41 through 4n drops sharply from a value larger than a few MΩ to a value lower than a few Ω (different depending on lamps). Thereafter, the DC power supply A (the third power supply 3) is activated, upon which a discharge maintenance voltage of about 130 V is applied to between the electrodes 4a and 4b of each of the xenon arc lamps 41 through 4n.
With the above, the main discharge in the inside of each of the xenon arc lamps 41 through 4n is continued, so that emission of a predetermined amount of light is continuously produced for a predetermined period of time (about 100 milliseconds to a few seconds).
As long pulse light emission for a long period of time is now possible as described above, the output characteristic of large-scaled photovoltaic devices which is slow in response can be measured with high accuracy by producing light emission from a plurality of lamps. It should be noted that a structure is also applicable in which a single xenon arc lamp is connected to the lamp light emission power supply circuit 10 to produce long pulse light emission from the xenon arc lamp.
In addition, use of the power supply circuit (comprising the second and third power supplies) of the present invention, shown in
In the drawing, with respect to three solar simulators SS1 through SS3 each having a single xenon arc lamp 48, 49, 410, the first power supplies 1A, 1B, 1C are provided for the xenon arc lamps 48, 49, 410, respectively, and the output circuits of the second power supply 2 and the third power supply 3 are connected in parallel to the xenon arc lamps 48, 49, 410 via the switches SW1 through SW3. Therefore, when the lighting start signals C1 through C3 are concurrently input to the respective first power supplies 1A through 1C, the three xenon arc lamps 48, 49, 410 concurrently emit light.
As for the example shown in
Meanwhile, as for the structure shown in
The embodiment of the present invention, which has been described above, is extremely useful as a solar simulator as it is possible to produce light emission from a plurality of lamps of a solar simulator using a single light emission circuit.
Specifically, the embodiment can present the advantages described below.
(1) As it is possible to produce light emission from a plurality of lamps of a solar simulator using a single light emission circuit, the output characteristic of large-scaled photovoltaic devices can be measured using a remarkably small and inexpensive power supply, compared to the conventional art.
(2) As it is possible to stably maintain the amount of light when light emission is continuously produced from a plurality of lamps of a solar simulator, the output characteristic of photovoltaic devices can be measured using the solar simulator with high accuracy.
(3) As it is possible to drive a plurality of solar simulators using a single power supply circuit which comprises the second and third power supplies, an area in which the device is installed can be reduced and power feeding equipment can be simplified.
Also, the use of a power supply circuit which comprises the second and third power supplies makes it possible to produce long pulse light emission from one or more xenon arc lamps, without enlarging the device.
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