JP2002118274A - Photovoltaic power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new photovoltaic power generation system equipped with a snow-melting function that can precisely prevent the occurrence of overcurrent and overheating in each string of a solar battery module by monitoring the snow- melting current at every string when the system makes snow-melting operation. SOLUTION: In the photovoltaic power generation system, a by-pass circuit (3) having an electromagnetic contactor (31) for by-pass and a snow-melting current detector (32) is provided at every solar battery string (1), and a snow-melting current monitoring circuit (4) connected to the contactor (31) and detector (32) of each by-pass circuit (3) is provided. At the time of starting the snow-melting operation, the electromagnetic contactors (31) are turned on and snow-melting currents flow in the solar battery strings (1) through the by-pass circuits (3). In addition, the snow-melting current detectors (32) always detect the values of the snow-melting currents, and the snow- melting current monitoring circuit (4) discriminates whether or not the detected values of the snow-melting currents are larger than a prescribed value. When the value of one of the snow-melting currents is larger than the prescribed value, the supply of the snow-melting current to the relevant by-pass circuit (3) is stopped by turning off the electromagnetic contactor (31) of the by-pass circuit (3).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The invention of this application relates to a photovoltaic power generation system. More specifically, the invention of this application relates to a new photovoltaic power generation system having a snow-melting function capable of performing good overcurrent / overheat protection for each string of a solar cell module.

[0002]

2. Description of the Related Art Solar energy has been attracting attention with increasing interest in energy and environmental issues. For example, a photovoltaic power generation system that converts solar energy into electric power using a solar cell module has been actively used. It is being advanced. In this photovoltaic power generation system, naturally, it is necessary to remove as much as possible extraneous matter on the solar cell module surface that hinders the irradiation of sunlight, in order to prevent a decrease in power generation efficiency. Above all, snow is a problem, and often requires a function to melt it.

Conventionally, as a snow melting function, for example, a bidirectional inverter is used, and at the time of power generation, the bidirectional inverter operates as an inverter to send a generated current from each string of the solar cell module to the system, thereby generating a snow melt. In this method, a bidirectional inverter operates as a converter to convert the system's commercial power into direct current, inject it into each string as a snowmelting current, and heat the solar cell module as a low-temperature heating element to perform snowmelting. Are known.

However, such a conventional solar power generation system having a snow melting function has the following problems in practical use. That is, in the conventional system, the injection control of the snow melting current is performed by the constant power control of the bidirectional inverter. There was a risk of overheating.

More specifically, for example, when a part of a string is disconnected for some reason and the number of parallel circuits is reduced, the snowmelt current is controlled to be constant power, and the current is distributed to the remaining strings. Snowmelt current to healthy strings increases, resulting in overcurrent. In addition, when the snow or snow melts, the snow on the surface of the solar cell module may become mottled, resulting in uneven sunshine or a temperature difference between the solar cell modules, which may cause overheating. For example, during the daytime snowmelt operation, if there is a difference between the injection current value into the strings exposed by snow sliding and the snowmelt current value into the strings with the remaining snow,
The difference increases as the sunshine increases or the temperature of the outside air increases, and the current increases as the string rises in temperature due to the sunshine, and the temperature increases further due to the increase in the current. The current of the battery module decreases, the difference increases, and overheating occurs. Even if such an abnormal situation occurs, the snow melting current cannot be properly dealt with by the constant power control as a matter of course, and the overcurrent and overheat protection during snow melting cannot be appropriately performed.

The invention of this application has been made in view of the above circumstances, and solves the problems of the prior art. During snow melting operation, the present invention monitors the snow melting current of each string of the solar cell module. It is an object of the present invention to provide a new photovoltaic power generation system with a snow melting function that can accurately prevent overcurrent and overheating of each string.

[0007]

Means for Solving the Problems In order to solve the above-mentioned problems, the invention of the present application is provided with a bidirectional inverter for interconnecting each string of the solar cell module and the system, Inverter operates as an inverter to send the generated current from each string of the solar cell module to the system, and during snow melting, the bidirectional inverter operates as a converter to inject the system's commercial power into each string as snow melting current, In a photovoltaic power generation system that performs snow melting by generating heat using a module as a heating element, a bypass circuit having a bypass electromagnetic contactor and a snow melting current detector is provided for each string of the solar cell module, and each bypass circuit is provided. Equipped with a snowmelt current monitoring circuit connected to a bypass electromagnetic contactor and a snowmelt current detector At the start of snow melting, the electromagnetic contactor for bypass is turned on, the snow melting current is injected into each string through the bypass circuit, and the snow melting current value is constantly detected by the snow melting current detector. The circuit determines whether the snow melting current value from each snow melting current detector is greater than a predetermined current value.
The bypass magnetic contactor of the corresponding bypass circuit is Off
The system is configured such that the injection of the snowmelt current into the bypass circuit is stopped, and the strings of the solar cell module and the system are connected to each other. A power supply for snow melting that supplies snow melting current to each string of the inverter and the solar cell module is provided.When power is generated, the inverter sends the generated current from each string of the solar cell module to the system. In a solar power generation system that melts snow by injecting snow melting current from a power supply into each string and generating heat using a solar cell module as a heating element, a bypass circuit having a bypass electromagnetic contactor and a snow melting current detector includes a solar cell. A snow melting current detector and a bypass provided for each string of the module and for each bypass circuit A snow melting current monitoring circuit connected to the electromagnetic contactor is provided. At the start of the snow melting, the bypass electromagnetic contactor is turned on, the snow melting current is injected into each string through the bypass circuit, and the snow melting current value is reduced. It is always detected by the snow melting current detector, and further, it is determined by the snow melting current monitoring circuit whether the snow melting current value from each snow melting current detector is larger than a predetermined current value.
The bypass magnetic contactor of the corresponding bypass circuit is Off
The present invention provides a photovoltaic power generation system (claim 2), wherein the injection of snowmelt current into the bypass circuit is stopped.

The invention of this application is also directed to the above-described photovoltaic power generation system, wherein the snow melting current monitoring circuit compares an input snow melting current value with a predetermined current value, and determines that the input snow melting current value is larger than the predetermined current value. Is provided with a comparator that outputs a snow melting stop signal (claim 3).

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention of the present application has the features as described above. Hereinafter, embodiments will be described with reference to the accompanying drawings, and the embodiments of the invention will be described in more detail. .

[0010]

[Embodiment 1] FIG. 1 shows an embodiment of a solar power generation system according to the present invention.

For example, as exemplified in FIG. 1, the photovoltaic power generation system according to the invention of the present application connects both the strings (1) (hereinafter, referred to as solar cell strings) of the solar cell module and the system. A directional inverter (2) is provided. When power is generated, the bidirectional inverter (2) operates as an inverter to send the generated current from each solar cell string (1) to the system. (2) The converter operates to inject the commercial power of the system into each of the solar cell strings (1) as a snow-melting current and generate heat by using the solar cell module as a heating element to perform snow-melting. A bypass circuit (3) having a magnetic contactor (31) for use and a snow melting current detector (32) is provided for each solar cell string (1), and The bypass electromagnetic contactor of the bypass circuit (3) (31) and snow melting current detector (3
A snow melting current monitoring circuit (4) connected to 2) is provided. The embodiment of FIG. 1 is a case in which four solar cell strings (1) are provided, but the number is not limited, and any number of solar cell strings (1) may be provided for each generated current circuit. The bypass circuit (3) is provided.

At the time of the start of snow melting, the bypass electromagnetic contactor (31) is turned on, the snow melting current is injected into each solar cell string (1) through the bypass circuit (3), and the snow melting current value is reduced. The snow melting current detector (32) constantly detects, and the snow melting current monitoring circuit (4) determines whether the snow melting current value from each snow melting current detector (32) is larger than a predetermined current value. In case,
The bypass electromagnetic contactor (31) of the corresponding bypass circuit (1) is turned off, and the injection of the snowmelt current into the bypass circuit (1) is stopped.

In this case, a further explanation will be given. First, the snow melting operation is started manually or by automatic control in accordance with snowfall detection by a snowfall sensor or the like. At the start of snow melting, the bidirectional inverter (2) switches from inverter operation to converter operation. At this time, a snow melting start signal is sent from the bidirectional inverter (2) to the bypass electromagnetic contactor (31) of each bypass circuit (3), and the bypass electromagnetic contactor (31) is excited by the snow melting start signal. You.
That is, it becomes On. Thereby, the blocking diode (5) for power generation is bypassed, and the snow melting current is injected into each solar cell string (1) through the bypass circuit (3). The solar cell module generates heat by this snow melting current, and snow melting is performed.

During the snow melting operation, the current value of the snow melting current flowing through each bypass circuit (3) is constantly detected by the snow melting current detector (32), and the current value is monitored by the snow melting current monitoring circuit (4).
To be sent to Snow melting current monitoring circuit (4)
Determines whether the snow melting current value is greater than a predetermined current value for each bypass circuit (3). For example, the input snow melting current value and the predetermined current as illustrated in FIG. A comparator that compares the current value with the current value and outputs a snowmelt stop signal when the input snowmelt current value is greater than a predetermined current value. And this snow melting current monitoring circuit (4)
If it is determined that the value is larger than the electromagnetic contactor (31) for the bypass of the bypass circuit (3) in which the determination is made.
A snowmelt stop signal is sent to the electromagnetic contactor (31) for turning off by the snowmelt stop signal. The snow melting stop signal may be simultaneously output to the bidirectional inverter (2), and the bidirectional inverter (2) stops the inverter operation according to the signal. Thereby, the injection of the snowmelt current is automatically stopped.

As described above, in this photovoltaic power generation system, the feedback circuit for the current supply state during the snow melting is built around the snow melting current monitoring circuit (4), and the snow melting current of each solar cell string (1) is constructed. By monitoring the energization state, the injection stop at the time of abnormality can be accurately and automatically controlled, and overcurrent / overheat protection for each solar cell string (1) can be realized.

Embodiment 2 FIG. 3 shows another embodiment of the photovoltaic power generation system of the present invention.
In the embodiment shown in FIG. 3, unlike the above-described embodiment, a one-way inverter (6) and a snowmelt separate from a commercial power supply for power generation are used instead of the expensive bidirectional inverter (2). A power supply (7) is used, and a power generation current is sent to a system via an inverter (6) during power generation, and a snow melting current is supplied from a snow melting power supply (7) during snow melting.

In this case, the snow melting current stop control at the time of abnormality is basically the same as that described above. At the start of snow melting, the bypass electromagnetic contactor (31) is turned on, and the snow melting current is reduced by the bypass circuit. It is injected into each solar cell string (1) through (3), the snow melting current value is constantly detected by the snow melting current detector (32), and furthermore, each snow melting current detector is detected by the snow melting current monitoring circuit (4). It is determined whether the snowmelt current value from (32) is greater than a predetermined current value. If the current value is greater than the predetermined value, the bypass electromagnetic contactor (31) of the corresponding bypass circuit (3) is turned off and the bypass circuit is turned off. The injection of the snowmelt current into the circuit (3) is stopped.

Of course, since the inverter (6) and the snow melting power supply (7) are used, at the start of snow melting, the snow melting from the snow melting power supply (7) is performed after the inverter (6) is manually or automatically stopped. When current injection is performed and a snowmelt abnormal stop occurs, a snowmelt stop signal from the comparator is also sent to the snowmelting power supply (7).

It is needless to say that snow melting can be stopped when a set time has elapsed by timer control in addition to the above-described abnormality detection.

The present invention is not limited to the above examples, and various embodiments can be made in detail.

[0021]

As described above in detail, according to the invention of this application, the snow melting current of each string of the solar cell module is monitored during the snow melting operation, and the overcurrent and the overheating of each string can be properly prevented. it can,
A new solar power generation system with snow melting function is provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a photovoltaic power generation system of the present invention.

FIG. 2 is a circuit diagram illustrating an example of a comparator.

FIG. 3 is a circuit diagram showing another embodiment of the photovoltaic power generation system of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 solar cell strings 2 bidirectional inverter 3 bypass circuit 31 bypass electromagnetic contactor 32 snow melting current detector 4 snow melting current monitoring circuit 5 blocking diode 6 inverter 7 snow melting power supply

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kiyoshi Kinoshita 3-12-15 Wakaoji, Amagasaki City, Hyogo Prefecture Sonoda Keiki Kogyo Co., Ltd. (72) Inventor Hiroki Nakagawa 3-12-15 Wakaoji Amagasaki City, Hyogo Prefecture Sonoda Keiki Kogyo Co., Ltd. F-term (reference) 5F051 BA11 JA07 JA11 JA20

Claims (3)

[Claims] A bidirectional inverter for interconnecting each string of the solar cell module and the system is provided, and at the time of power generation, the bidirectional inverter operates as an inverter to generate electric current from each string of the solar cell module. In a solar power generation system, a bidirectional inverter operates as a converter during snow melting, injects commercial power from the system into each string as snow melting current, and generates heat using a solar cell module as a heating element. A bypass circuit having a bypass electromagnetic contactor and a snowmelt current detector is provided for each string of the solar cell module, and a snowmelt current monitor connected to the bypass electromagnetic contactor and the snowmelt current detector of each bypass circuit is provided. A circuit is provided. At the start of snow melting, the electromagnetic contactor for bypass is turned on, The current is injected into each string through the bypass circuit, the snow melting current value is constantly detected by the snow melting current detector, and the snow melting current value from each snow melting current detector is increased by the snow melting current monitoring circuit from the predetermined current value. Is determined, and if so, the bypass electromagnetic contactor of the corresponding bypass circuit is turned off, and the injection of the snowmelt current into the bypass circuit is stopped. And solar power system. 2. An inverter for interconnecting each string of the solar cell module and the system and a snow melting power supply for supplying a snow melting current to each string of the solar cell module are provided. In a solar power generation system that sends the generated current from each string to the system, injects the snow current from the power supply for snow melting into each string during snow melting, and generates heat using the solar cell module as a heating element, it melts snow, A bypass circuit having an electromagnetic contactor and a snowmelt current detector is provided for each string of the solar cell module, and a snowmelt current monitoring circuit connected to the snowmelt current detector and the bypass electromagnetic contactor of each bypass circuit is provided. At the start of snow melting, the electromagnetic contactor for bypass is turned on and the snow melting current is reduced. While being injected into each string through the bypass circuit, the snow melting current value is constantly detected by the snow melting current detector, and furthermore, the snow melting current value from each snow melting current detector is larger than the predetermined current value by the snow melting current monitoring circuit. It is determined whether or not it is large, and when it is large, the bypass electromagnetic contactor of the corresponding bypass circuit is turned off, and the injection of the snowmelt current into the bypass circuit is stopped. Solar power system. 3. A snow melting current monitoring circuit includes a comparator for comparing an input snow melting current value with a predetermined current value and outputting a snow melting stop signal when the input snow melting current value is larger than the predetermined current value. The solar power generation system according to claim 1.