JP2016115283A - Current-voltage suppression device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current-voltage suppression device capable of protecting a DC circuit even when a transient phenomenon due to a sudden increase in solar radiation intensity or the like occurs, reducing operation cost, and improving productivity.SOLUTION: A device provided in a DC circuit between a photovoltaic power generation part S having a plurality of solar battery strings 1 and a power conditioner 4, comprises: a current measuring unit 11 which measures a current of the DC circuit; a voltage measuring unit 12 which measures a voltage of the DC circuit; a variable resistor 6 which is provided in the DC circuit in series; a resistance control unit 14 which changes a resistance value of the variable resistor 6; and an arithmetic unit 13 which has a preset current reference value and a preset voltage reference value, the arithmetic unit 13 outputting a command to change the resistance value of the variable resistor 6 to the resistance control unit 14 when a value of the current measured by the current measuring unit 11 exceeds a current reference value L or a value of the voltage measured by the voltage measuring unit 12 exceeds a voltage reference value L.SELECTED DRAWING: Figure 2

Description

  Embodiments described herein relate generally to a current-voltage suppressing device that suppresses current and voltage of a DC circuit in a photovoltaic power generation system.

  In recent years, a so-called mega solar system, which is called a mega solar system, has been developed for a solar power generation system having a power generation capacity exceeding 1 MW. Such a photovoltaic power generation system is configured to obtain desired power by connecting the output from the solar cell module to a device called a power conditioner (PCS). Such a solar power generation system is generally configured by connecting a plurality of solar cell strings in which solar cell modules are connected in series to a power conditioner in parallel.

  More specifically, in the photovoltaic power generation system, a connection box and a current collection box are provided between the solar cell module and the power conditioner. That is, a plurality of solar cell strings parallel to each other are connected in series to the connection box, and the connection box collects these powers and outputs them to the current collection box. A plurality of connection boxes parallel to each other are connected in series to the current collection box, and the input power is collected and output to the power conditioner.

  The power conditioner has an inverter function for connection to the power system and a maximum power tracking control function for controlling the output voltage and current of the solar cell module. The inverter function is a function of converting DC power output from the solar cell module into AC power and outputting the AC power to the power system. The maximum power tracking (MPPT) control function is a function for controlling the output power determined by the current and the voltage to always become maximum according to the output fluctuation of the solar cell accompanying the change in the amount of solar radiation.

  When power exceeding the rated power is input from the solar cell module, the power conditioner increases the voltage of the solar cell string and causes the current to reach the rated input power of the power conditioner as shown in FIG. Control is performed to move the operating point on the IV curve from the point P1 to the point P2 in a decreasing direction.

  For example, when the ratio of the total rated power of all the solar cell strings to the rated power of the power conditioner is 100%, the output curve of the power conditioner is as shown in FIG. 13, and the power of the solar cell string remains as it is. Output power. That is, the area of the output curve = the total power of the solar cell string. The operating point on the IV curve at this time is a point P1 in FIG.

  On the other hand, when the ratio of the total rated power of all the solar cell strings to the rated power of the power conditioner is 150%, the output curve of the power conditioner is as shown in FIG. 14, and is limited by the rated power of the power conditioner. . The operating point on the IV curve at this time is approximately point P2 in FIG.

  Moreover, in a solar power generation system, a solar panel may be installed so that the total rated power of all the solar cell strings exceeds the rated power of the power conditioner. As described above, when the rated power ratio of the solar cell string to the power conditioner is 100%, the power loss is not limited by the rated power of the power conditioner, so that the energy loss is small. However, as shown in FIG. 13, it is temporary that the performance of the solar cell string can be fully utilized, and the cost performance is low.

  This decrease in cost performance is particularly noticeable when solar panels are installed in a small site area. Accordingly, a solar panel is overloaded so that the rated power ratio exceeds 100%, and the time for which the performance of the solar cell string can be utilized to the maximum is made as shown in FIG.

JP2013-0383345A

  In the photovoltaic power generation system, a fuse is provided to protect the DC circuit when an overcurrent occurs. The fuse is provided in each of the connection box, the current collection box, and the power conditioner.

In general, it is desirable that the fuse rating has a margin of about 1.4 to 1.7 times the solar cell rated current Imp in consideration of fluctuations in solar radiation based on the solar cell rated current Imp of the photovoltaic power generation system. . In actual operation, the solar radiation intensity at the solar cell rated output rarely exceeds 1000 W / m ^2, and the current during normal operation is smaller than the solar cell rated current Imp. Therefore, there may be a case where a fuse with a small tolerance for the solar cell rated current Imp is selected.

  When a solar battery string is overloaded, the total power of the solar battery string exceeds the rated input power of the inverter before each solar battery outputs the rated power due to increased solar radiation. Since the current of the solar cell string is narrowed down, it is likely that the normal current is smaller than the solar cell rated current Imp, and a fuse having a small tolerance is easily selected. Moreover, the number of parallel solar cell strings connected to the power conditioner increases due to overloading, and the tolerance of the fuse rating installed in the integrated circuit tends to decrease.

However, when the rated tolerance of the fuse is small, when some solar cell strings are exposed to strong solar radiation from the gap of the clouds on a cloudy day, for example, relatively strong solar radiation of about 1400 W / m ² is biased, When relatively weak solar radiation of about 200 W / m ² is uniformly applied to other solar cell strings, the current output from the string is within a range where the total power of the solar cell string does not exceed the rated input power of the power conditioner. The current of about 1.4 to 1.7 times the solar cell rated current Imp flows, and the fuse provided in the junction box, the current collector box or the power conditioner is blown. As a result, the amount of power generated by the solar cell string connected to the circuit where the fuse has been blown is lost, loss of opportunity occurs, and periodic inspection and replacement of the fuse is necessary, resulting in increased operating costs. It was.

Further, when the entire solar cell string group is temporarily exposed to strong solar radiation (for example, about 1200 W / m ² ) and power exceeding the rated capacity is input to the power conditioner due to overloading or the like, the power conditioner In order to reduce the input power, control is performed to decrease the input current and increase the input voltage while keeping the power of the solar cell string constant as shown in FIG. However, during this control, the operating voltage range of the power conditioner may be exceeded and an overvoltage V2 may be generated, causing the power conditioner to stop operating. For this reason, there is a problem that the operation rate is lowered due to the stoppage of power generation, and the productivity is lowered.

  The current-voltage suppressing device according to the present embodiment is made to solve the above-described problems, and can protect a DC circuit even when a transient phenomenon occurs due to a sudden increase in solar radiation intensity, etc. An object of the present invention is to provide a current-voltage suppressing device capable of reducing and improving productivity.

  In order to achieve the above object, the current / voltage suppressing device of the present embodiment is a current / voltage suppressing device provided in a DC circuit between a photovoltaic power generation unit having a plurality of solar cell strings and a power conditioner. A current measuring unit that measures the current of the DC circuit, a voltage measuring unit that measures the voltage of the DC circuit, a variable resistor provided in series with the DC circuit, and a resistance control that changes the resistance value of the variable resistor And a calculation unit having a preset current reference value and voltage reference value, and the calculation unit, when the current value measured by the current measurement unit exceeds the current reference value, or When the voltage value measured by the voltage measurement unit exceeds the voltage reference value, a command to change the resistance value of the variable resistor is output to the resistance control unit.

1 is an overall configuration diagram of a photovoltaic power generation system in which a current-voltage suppressing device according to a first embodiment is installed. 1 is an overall configuration diagram of a current-voltage suppressing device according to a first embodiment. It is an operation | movement flowchart of the current-voltage suppression apparatus which concerns on 1st Embodiment, and shows 1st operation | movement. It is an operation | movement flowchart of the current-voltage suppression apparatus which concerns on 1st Embodiment, and shows 2nd operation | movement. It is an operation | movement flowchart of the current-voltage suppression apparatus which concerns on 1st Embodiment, and shows 3rd operation | movement. It is a whole block diagram of the current-voltage suppression apparatus which concerns on 2nd Embodiment. It is an operation | movement flowchart of the current-voltage suppression apparatus which concerns on 2nd Embodiment, and shows 1st operation | movement. It is an operation | movement flowchart of the current-voltage suppression apparatus which concerns on 2nd Embodiment, and shows 2nd operation | movement. It is an operation | movement flowchart of the current-voltage suppression apparatus which concerns on 2nd Embodiment, and shows 3rd operation | movement. It is a whole block diagram of the current-voltage suppression apparatus which concerns on 3rd Embodiment. It is a whole block diagram of the current-voltage suppression apparatus which concerns on 4th Embodiment. It is a figure which shows the change of a solar cell string IV curve operating point when the electric power of a solar cell string exceeds power conditioner rated input power. It is a power conditioner output curve in case the ratio of the total rated power of all the solar cell strings with respect to the rated power of a power conditioner is 100%. It is a power conditioner output curve when the ratio of the total rated power of all the solar cell strings to the rated power of the power conditioner is 150%. It is a figure which shows the change of the solar cell string IV curve operating point when the strong solar radiation hits the whole group of a solar cell string temporarily, and the input electric power exceeding the rated capacity of a power conditioner generate | occur | produces.

[1. First Embodiment]
Below, the current-voltage suppression apparatus of this embodiment is demonstrated, referring FIGS. 1-3. First, this embodiment will be schematically described, and then the configuration will be described in detail.

[1-1. Outline]
FIG. 1 is an overall configuration diagram of a photovoltaic power generation system in which the current-voltage suppressing device of the present embodiment is installed. The solar power generation system is a so-called mega solar power plant that is linked to a power system, has a large number of solar cell strings 1, converts solar energy into electric power, and sends it to the power system.

  This solar power generation system includes a plurality of solar cell strings 1, a connection box 2, a current collection box 3, and a power conditioner 4. The solar cell string 1 is configured by connecting a plurality of solar cell modules in which a plurality of solar cells are arranged in a panel shape, and generating DC power by receiving a photovoltaic effect by receiving sunlight. Let The plurality of solar cell strings 1 are connected to the power conditioner 4, and these solar cell strings 1 are collectively referred to as a photovoltaic power generation unit S. A group of solar cell strings 1 provided in parallel with each other is referred to as a solar cell string group 1G.

  The connection box 2 is connected in series with the solar cell string group 1G, and outputs the input power as one. The connection box 2 is provided with a switch SW for switching connection and disconnection of the solar cell string 1 and a fuse H having a predetermined tolerance on the circuit for each solar cell string 1. In this embodiment, since three solar cell strings 1 are connected, three switches and three fuses H are provided.

  The current collection box 3 is connected in series with a plurality of connection boxes 2 that are parallel to each other, and the input power is combined into one and output to the power conditioner 4. In the current collection box 3, a switch SW for switching connection / disconnection of the connection box 2 and a fuse H having a predetermined tolerance rating are provided on a circuit for each connection box 2.

  The power conditioner 4 is connected between the current collection box 3 and the power system, and is a device that links the solar cell string 1 to the power system. The power conditioner 4 is connected to a fuse H having a predetermined tolerance rating provided on a circuit for each current collection box 3, a switch SW for switching connection and disconnection of the current collection box 3, and a power system. A DC / AC converter T that converts input DC power into AC power having a predetermined frequency, and a control unit (not shown) are provided. The control unit has a maximum power tracking (MPPT) control function for controlling so that the output power determined by the current and the voltage is always maximized according to the output fluctuation of the solar cell string 1 due to the change in the amount of solar radiation. Have.

  The current / voltage suppressing device 5 of the present embodiment is provided in a DC circuit between the photovoltaic power generation unit S and the power conditioner 4, and by changing the resistance value of the variable resistor 6 provided in the DC circuit, The protection of the DC circuit fuse H and the continuation of power generation are realized. The DC circuit refers to a circuit from the photovoltaic power generation unit S to the DC / AC converter in the power conditioner 4 and has a plurality of paths. The current / voltage suppressing device 5 of the present embodiment is provided closer to the photovoltaic power generation unit S than the fuse H in each of the junction box 2, the current collection box 3, and the power conditioner 4. However, you may make it provide in at least any one of the connection box 2, the current collection box 3, and the power conditioner 4. FIG.

[1-2. Detailed configuration]
FIG. 2 is an overall configuration diagram of the current-voltage suppressing device 5 of the present embodiment. The current / voltage suppressing device 5 includes a current measuring device 8, a voltage measuring device 9, a switch 7 and a variable resistor 6 provided in series in each path, and a control device 10 connected to these devices 6 to 9. I have. The current measuring device 8, the voltage measuring device 9, the switch 7, and the variable resistor 6 are connected in series from the photovoltaic power generation unit S to the power conditioner 4 in this order.

  The current measuring device 8 measures the current of the DC circuit and outputs the measured current to the control device 10 as an electrical signal. The current measuring device 8 is, for example, a current transformer (CT). The current measuring device 8 can measure not only a forward current flowing from the solar cell string 1 to the power conditioner 4 but also a reverse current flowing in the opposite direction. The voltage measuring instrument 9 measures the voltage of the DC circuit, and outputs the measured voltage to the control device 10 as an electric signal. The voltage measuring instrument 9 is, for example, an instrument transformer (VT).

  The switch 7 has a contact point, receives and receives a command from the control device 10, and opens and closes the contact point to switch between conduction and interruption of the DC circuit. The switch 7 has a state notification unit (not shown) for notifying the contact state of the contact closed state or the contact open state where the DC circuit is in a conductive state. The variable resistor 6 receives a command from the control device 10 and changes the resistance of the DC circuit. The variable resistor 6 is not particularly limited as long as it can change its resistance value in response to an external electric signal or the like, but it is desirable that the resistance value can be changed in the range of several Ω to several hundred Ω.

  The control device 10 includes, for example, a computer having a CPU, a memory, and the like. The control device 10 stores a program in an HDD, an SSD, or the like, appropriately expands in a RAM, and processes the input current, voltage, and the like. From the contact state, the variable resistor 6 and the switch 7 are controlled based on a predetermined condition.

  In other words, the control device 10 includes a current measurement unit 11, a voltage measurement unit 12, a calculation unit 13, a resistance control unit 14, a contact control unit 15, and a contact state confirmation unit 16.

  The current measuring unit 11 is connected to the current measuring device 8 of each path, converts the input electric signal, and calculates the current value of each path. In other words, the current measuring unit 11 measures the current of the DC circuit using the current measuring device 8 as a current sensor. The voltage measuring unit 12 is connected to the voltage measuring device 9 of each path, converts the input electric signal, and calculates the voltage value of each path. In other words, the voltage measurement unit 12 uses the voltage measuring device 9 as a voltage sensor and measures the voltage of the DC circuit.

  The calculation unit 13 includes a CPU and a recording medium such as an HDD or an SSD, and is connected to the current measurement unit 11, the voltage measurement unit 12, the resistance control unit 14, the contact control unit 15, and the contact state confirmation unit 16. Yes. Based on the input current value and voltage value, the calculation unit 13 instructs the resistance control unit 14 and the contact control unit 15 to change the resistance value of the variable resistor 6 and the contact point of the switch 7 under predetermined conditions. Outputs a command to contact and separate.

The recording medium stores a preset current reference value L, voltage reference value L, backflow reference value L, current reference value H, voltage reference value H, and backflow reference value H. These reference values L and H are set as follows, for example.
Current reference value L: Rated current value of the fuse H of the DC circuit Voltage reference value L: Upper limit value of the operating range of the power conditioner 4 Reverse flow reference value L: Value that allows the deterioration of the solar cells Current reference value H: DC circuit Value that determines the short-circuit current that flows when short-circuited Voltage reference value H: Value that determines voltage abnormality that occurs when a DC circuit ground fault Backflow reference value H: Value that determines the back-flow current that flows when a DC circuit is short-circuited

  However, the current reference value H is larger than the current reference value L, and the voltage reference value H is larger than the voltage reference value L. The absolute value of the backflow reference value H is larger than the absolute value of the backflow reference value L. Note that these specific values can be appropriately changed according to the design. As will be described later, the reverse flow means that a current flows to the solar cell string 1, and when the power conditioner 4 is stopped and a difference in voltage between the solar cell strings 1 occurs due to an uneven solar radiation amount or the like. Arise.

  More specifically, the calculation unit 13 compares the current value and the voltage value input from the current measurement unit 11 and the voltage measurement unit 12 with the current reference value L and the voltage reference value L. When the input current value exceeds the current reference value L or the input voltage value exceeds the voltage reference value L, the calculation unit 13 outputs a command to increase the resistance value of the variable resistor 6 to the resistance control unit 14. .

  In addition, when the input current value exceeds the backflow reference value L, the calculation unit 13 outputs a command to increase the resistance value of the variable resistor 6 to the resistance control unit 14. Further, when the input current value and the input voltage value exceed any of the current reference value H, the voltage reference value H, and the backflow reference value H, the calculation unit 13 issues a command to open the switch 7. Output to the contact control unit 14.

  After changing the resistance value of the variable resistor 6, it is necessary to restore it when the transient phenomenon settles down. Therefore, the calculation unit 13 is provided with a timer (not shown) for measuring time, and the input current value is any one of the current reference value L, the current reference value H, the backflow reference value L, and the backflow reference value H. Measure the time from when it exceeds and falls below that value. Further, the time from when the resistance value of the variable resistor 6 is changed to when it is changed next is measured.

  The resistance control unit 14 is connected to the variable resistor 6 in each path, and changes the resistance value of the variable resistor 6 in response to a command from the calculation unit 13. The contact control unit 15 is connected to the contact of the switch 7 provided in each path, and receives a command from the calculation unit 13 to open or close the contact of the switch 7. The contact state confirmation unit 16 is connected to the state notification unit and the calculation unit 13 of the switch 7 provided in each path, and notifies the contact state of either the open state or the closed state of the contact from the state notification unit. The signal is acquired and the signal is output to the calculation unit 13.

[1-3. Action]
The operation of the current / voltage suppressing device 5 of this embodiment will be described with reference to FIGS. The operation of the current / voltage suppressing device 5 is independent in each path in the apparatus 5, and the operation in one path will be described below. As an initial state, the switch 7 is closed, that is, the DC circuit is in a conductive state, and the resistance value of the variable resistor 6 is the lowest value of the resistor 6.

There are roughly three operations in the present embodiment. 3 to 5 are first to third operation flowcharts.
[First operation]
The first operation will be described as shown in FIG. 3. First, the control device 10 acquires the contact state of the switch 7 by the contact state confirmation unit 16 and confirms that the switch 7 is in the closed state. (Step S01). If this is not the case, the switch 7 is closed via the contact state confirmation unit 16, the calculation unit 13, and the contact control unit 15, and the process returns to step S01.

  Next, the current measuring unit 11 and the voltage measuring unit 12 measure the current value and the voltage value using the current measuring instrument 8 and the voltage measured value 9 (Step S02), and the measured current value and voltage value are calculated by the calculating unit 13. Output to. The calculation unit 13 compares the input current value and voltage value with the current reference value L and voltage reference value L (step S03), and determines whether the current reference value L or the voltage reference value L is exceeded (step S03). S04).

  If none of the reference values L is exceeded (No in step S04), the process returns to step S02. On the other hand, if any of the reference values L is exceeded (Yes in step S04), the resistance of the variable resistor 6 is set so that the input current value is equal to or less than the current reference value L and the input voltage value is equal to or less than the voltage reference value L. A command to change the value is output to the resistance control unit 14. That is, a command for increasing the resistance value of the variable resistor 6 is output. Upon receiving this command, the resistance control unit 14 changes the resistance value of the variable resistor 6 to R (> minimum value Rmin) based on the received command (step S05). Thereby, it is suppressed that an electric current and a voltage become an excessive value.

  Further, the time is measured by a timer, and the resistance value R is maintained until a predetermined time elapses when the input current value is equal to or less than the current reference value L and the input voltage value is equal to or less than the voltage reference value L. When the predetermined time has elapsed, the calculation unit 13 outputs a command for setting the resistance value to the minimum value to the resistance control unit 14, and the resistance control unit 14 sets the resistance value to the minimum value (step S06). When the resistance value of the variable resistor 6 is the lowest value, the input current value is equal to or less than the current reference value L and the input voltage value is equal to or less than the voltage reference value L for a predetermined time or longer (Yes in step S07), the variable resistor 6 End control. When this is not satisfied, the process returns to step S05 (No in step S07).

[Second operation]
Next, the second operation will be described with reference to FIG. The second operation is an operation when a backflow current is generated in the photovoltaic power generation system. Here, the reverse flow means that a current flows to the solar cell string 1. The backflow occurs when a voltage level difference occurs between the solar cell strings 1. For example, when the power conditioner 4 stops due to an inspection or when the power conditioner 4 detects an abnormality, a voltage difference is generated between the solar cell strings 1 due to uneven solar radiation, or the power conditioner 4 Even when the solar cell string 1 is in operation, the solar radiation amount suddenly increases in some solar cell strings 1 and the voltage rises from the other solar cell strings 1.

  A plurality of paths can be considered as a path through which the reverse current flows. For example, a path that flows from one solar cell string 1 in one connection box 2 to another solar cell string 1 in the connection box 2, another connection from the solar cell string 1 in the connection box 2 to the current collection box 3. A path flowing to the solar cell string 1 in the box 2, a path flowing from the solar cell string 1 in the connection box 2 to the current collection box 3, the power conditioner 4, the other current collection box 3, and the solar cell string 1 in the other connection box 2. Etc.

  When such a backflow current is generated, the solar cells of the solar cell string 1 are damaged, and the cells are deteriorated. Therefore, the damage to the solar battery cell is suppressed by performing the operation as shown in FIG. The description of the same points as the first operation is omitted. However, the voltage need not be measured.

  As shown in FIG. 4, the calculation unit 13 compares the input current value with a preset backflow reference value L (step S11), and determines whether the input current value exceeds the backflow reference value L (step S11). S12). In addition, when the current flowing in the direction from the solar cell string 1 to the power conditioner 4 is positive, exceeding the reference value means that the current value is lower than the reference value. In other words, it means that the absolute value of the input current value exceeds the absolute value of the backflow reference value L when backflow occurs.

  When the backflow reference value L is not exceeded (No in step S12), the process returns to step S02. On the other hand, when exceeding the backflow reference value L (Yes in step S12), the calculation unit 13 issues a command to change the resistance value of the variable resistor 6 so that the input current value does not exceed the backflow reference value L. Output to. That is, a command for increasing the resistance value of the variable resistor 6 is output. The resistance control unit 14 changes the resistance value of the variable resistor 6 to R (> minimum value Rmin) based on the received command (step S13).

  Next, the time is measured by a timer, and the resistance value R is maintained until a predetermined time elapses when the input current value does not exceed the backflow reference value L. When the predetermined time has elapsed, the calculation unit 13 outputs a command for setting the resistance value to the minimum value to the resistance control unit 14, and the resistance control unit 14 sets the resistance value to the minimum value (step S14). When the resistance value of the variable resistor 6 is the lowest value and the input current value does not exceed the backflow reference value L for a predetermined time (Yes in step S15), the control of the variable resistor 6 is terminated. When not satisfying this, it returns to Step S13 (No of Step S15).

[Third operation]
The third operation will be described with reference to FIG. The third operation is an operation when an abnormality occurs in the solar power generation system. The description of the same points as the first operation is omitted.

  The calculation unit 13 performs a comparison determination between each input measurement value and each reference value H. That is, the input current value is compared with the current reference value H and the backflow reference value H, the input voltage value is compared with the voltage reference value H (step S21), and the input measurement value is any one of the reference values H. Is determined (step S22). When the input measurement value exceeds any of the reference values H (Yes in step S22), the calculation unit 13 outputs a command for opening the contact of the switch 7 to the contact control unit 15 to perform contact control. The contact of the switch 7 is opened by the part 15 (step S23). On the other hand, when the input measurement value does not exceed any reference value H (No in step S22), the process returns to step S21.

[1-4. effect]
(1) The current / voltage suppressing device 5 of the present embodiment is a device provided in a DC circuit between the photovoltaic power generation unit S having a plurality of solar battery strings 1 and the power conditioner 4, and the current of the DC circuit A current measuring unit 11 for measuring the voltage, a voltage measuring unit 12 for measuring the voltage of the DC circuit, a variable resistor 6 provided in series with the DC circuit, a resistance control unit 14 for changing the resistance value of the variable resistor 6, And a calculation unit 13 having a set current reference value and voltage reference value. The calculation unit 13 is configured so that the current value measured by the current measurement unit 11 exceeds the current reference value L or the voltage measurement unit 12. When the voltage value measured in (1) exceeds the voltage reference value L, a command to change the resistance value of the variable resistor 6 is output to the resistance control unit 14.

  Thereby, even when a transient phenomenon due to a sudden increase in solar radiation intensity or the like occurs, the resistance of the DC circuit can be increased so that the measured current value and voltage value are lower than each reference value L. Overcurrent and overvoltage can be prevented and the DC circuit can be protected. Therefore, it is possible to avoid a situation where the fuse is blown and the power generation is stopped, and to realize a reduction in operation cost and an improvement in productivity.

  In particular, in the past, it was possible to control the input power with a power conditioner, but since the power was already concentrated, it was not possible to control each path of the DC circuit. However, by providing the current / voltage suppressing device of this embodiment in at least one of the connection box 2, the current collection box 3, and the power conditioner 4 of the DC circuit, protection is possible for each path of the DC circuit.

(2) The computing unit 13 further has a preset reverse flow reference value L, and if the input current value exceeds the preset reverse flow reference value L, the command is given to increase the resistance value of the variable resistor 6 The data is output to the control unit 14. Thereby, even if a backflow current is generated in the solar cells of the solar cell string 1, the resistance of the DC circuit can be increased, so that the deterioration of the solar cells due to the backflow current can be suppressed. Moreover, since it is not necessary to stop the operation of the solar power generation system, productivity can be increased.

(3) The DC circuit includes a switch 7 provided closer to the solar cell string 1 than the variable resistor 6, and a contact control unit 15 that controls opening and closing of the contact of the switch 7, and the calculation unit 13 includes: The second current reference value H, the second voltage reference value H, and the second backflow reference value H are further included, and any one of the input current value and the input voltage value is the second current reference value H, the second current reference value H, and the second current reference value H. When the voltage reference value H of 2 or the second backflow reference value H is exceeded, a command to open the contact of the switch 7 is output to the contact control unit 15, and the contact control unit 15 responds to the command to open. Based on this, the switch 7 was opened. Thereby, even if it is a case where a circuit short circuit and a ground fault generate | occur | produce, protection of each apparatus of a photovoltaic power generation system is attained.

[2. Second Embodiment]
[2-1. Constitution]
The second embodiment will be described with reference to FIGS. The second embodiment is the same as the basic configuration of the first embodiment. In the following, only differences from the first embodiment will be described, and the same parts as those in the first embodiment will be denoted by the same reference numerals and detailed description thereof will be omitted.

  FIG. 6 is an overall configuration diagram of the current-voltage suppressing device according to the second embodiment. The second embodiment is different from the first embodiment in the configuration of a switch, a variable resistor, and a calculation unit. That is, two switches 7a and 7b are provided in series in each path of the DC circuit, and these switches 7a and 7b are provided in parallel to each other. The variable resistor 6 is connected in parallel with the switch 7a, and is connected in series with the switch 7b. The switches 7 a and 7 b are connected to the contact control unit 15 and the contact state confirmation unit 16.

  When the input current value exceeds the preset current reference value L or when the input voltage value exceeds the preset voltage reference value L, the calculation unit 13 closes the switch 7b in the contact control unit 15. A command for setting the state is output, and then a command for increasing the resistance value of the variable resistor 6 is output to the resistance control unit 14.

  Further, when the input current value exceeds the preset reverse flow reference value L, the calculation unit 13 outputs a command to close the switch 7b to the contact control unit 15, and then the resistance value of the variable resistor 6 Is output to the resistance control unit 14. When either the input current value or the input voltage value exceeds the current reference value H, the voltage reference value H, or the reverse flow reference value H, the calculation unit 13 connects the contacts of the switches 7a and 7b to the contact control unit 15. A command to open is output.

[2-2. Action]
The operation of the current / voltage suppressing device 51 of this embodiment will be described with reference to FIGS. The operation of the current / voltage suppressing device 51 is independent in each path, and the operation in one path will be described below. In the initial state, the resistance value of the variable resistor 6 is set to the minimum value Rmin.

The operation of the present embodiment is roughly divided into three as in the first embodiment. 7 to 9 are first to third operation flowcharts. Description of operations similar to those of the first embodiment will be omitted as appropriate.
[First operation]
The first operation will be described with reference to FIG. 7. First, the control device 10 acquires the contact state of the switches 7 a and 7 b by the contact state confirmation unit 16, and the switch 7 a is closed. It is confirmed whether 7b is an open state (step S31). If this is not the case, the switch 7a is closed and the switch 7b is opened via the contact state confirmation unit 16, the calculation unit 13, and the contact control unit 15, and the process returns to step S31.

  Next, the current measuring unit 11 and the voltage measuring unit 12 measure the current value and the voltage value using the current measuring instrument 8 and the voltage measured value 9 (Step S32), and the measured current value and voltage value are calculated by the calculating unit 13. Output to. The computing unit 13 compares the input current value and voltage value with the current reference value L and voltage reference value L (step S33), and determines whether the current reference value L or the voltage reference value L is exceeded (step S33). S34).

  If any reference value L is not exceeded (No in step S34), the process returns to step S32. On the other hand, when any one of the reference values L is exceeded (Yes in step S34), the calculation unit 13 outputs a command to close the switch 7b to the contact control unit 15. The contact control unit 15 closes the switch 7b based on this command (step S35), and the contact state confirmation unit 16 confirms the closed state of the switch 7b. If it cannot be confirmed (No in step S36), The process returns to step S37. If the closed state of the switch 7b can be confirmed (Yes in step S36), the confirmed signal is output to the calculation unit 13, and the calculation unit 13 outputs a command to open the switch 7a to the contact control unit 15.

  The contact control unit 15 opens the switch 7a (step S37), and the contact state confirmation unit 16 confirms the open state of the switch 7a. If it cannot be confirmed (No in step S38), the process returns to step S37. . If the open state of the switch 7a is confirmed (Yes in step S38), the contact state confirmation unit 16 outputs the confirmed signal to the calculation unit 13, and the calculation unit 13 has an input current value equal to or less than the current reference value L. And a command to increase the resistance value of the variable resistor 6 is output to the resistance control unit 14 so that the input voltage value is equal to or less than the voltage reference value L, and the resistance control unit 14 sets the resistance value to R based on the command. (> Minimum value Rmin) (Step S39).

  Further, the time is measured by a timer, and the resistance value R is maintained until a predetermined time elapses when the input current value is equal to or less than the current reference value L and the input voltage value is equal to or less than the voltage reference value L. When the predetermined time has elapsed, the arithmetic unit 13 outputs a command for setting the resistance value to the minimum value to the resistance control unit 14, and the resistance control unit 14 sets the resistance value to the minimum value (step S 40). When the resistance value of the variable resistor 6 is the lowest value, the input current value becomes equal to or less than the current reference value L and the input voltage value becomes equal to or less than the voltage reference value L for a predetermined time or longer (Yes in step S41), the process proceeds to step S42. . When this condition is not satisfied (No in step S41), the process returns to step S40.

  In step S42, the arithmetic unit 13 outputs a command for closing the switch 7a to the contact control unit 15, and the switch 7a is closed based on this command (step S42). The contact state confirmation part 16 confirms the closed state of the switch 7a, and if it cannot confirm (No of step S43), it will return to step S42. If the closed state of the switch 7a is confirmed (Yes in step S43), the contact state confirmation unit 16 outputs the confirmed signal to the calculation unit 13, and the calculation unit 13 instructs the switch 7b to be in an open state. Is output to the contact control unit 15. The contact control unit 15 opens the switch 7b based on this command (step S44), and the contact state confirmation unit 16 confirms the open state of the switch 7b, and if not confirmed (No in step S45), step. Return to S44. If the open state of the switch 7b can be confirmed (Yes in step S45), the process ends.

[Second operation]
Next, the second operation will be described with reference to FIG. The second operation is an operation when a backflow current is generated in the photovoltaic power generation system. Since the second operation is the same as the first operation in the basic operation, a redundant description will be omitted as appropriate, and different points will be described.

  As shown in FIG. 8, steps S31 and S32 are the same as the first operation. Subsequent to step S32, the calculation unit 13 compares the input current value with the backflow reference value L (step S51), and determines whether the input current value exceeds the backflow reference value L (step S52). If the backflow reference value L is not exceeded (No in step S52), the process returns to step S32. On the other hand, when exceeding the backflow reference value L (Yes of step S52), it progresses to step S35. Steps S35 to S38 are the same as the first operation.

  If the open state of the switch 7a is confirmed in step S38 (Yes in step S38), the contact state confirmation unit 16 outputs the confirmed signal to the calculation unit 13, and the calculation unit 13 determines that the input current value is a reverse flow reference. A command for increasing the resistance value of the variable resistor 6 is output to the resistance control unit 14 so as not to exceed the value L. Then, the resistance control unit 14 changes the resistance value of the variable resistor 6 to R (> minimum value Rmin) based on the received command (step S53), and proceeds to step S40 as in the first operation. When the resistance value of the variable resistor 6 is the lowest value and the input current value becomes the backflow reference value L or less for a predetermined time or more (Yes in Step S54), the process proceeds to Steps S42 to S45 that are the same as the first operation. When this condition is not satisfied (No in step S54), the process returns to step S40.

[Third operation]
The third operation will be described with reference to FIG. The third operation is an operation when an abnormality occurs in the solar power generation system. The description of the same points as the first operation is omitted.

  The calculation unit 13 performs a comparison determination between each input measurement value and each reference value H. That is, the input current value is compared with the current reference value H and the backflow reference value H, the input voltage value is compared with the voltage reference value H (step S61), and the input measurement value is any one of the reference values H. Is determined (step S62). When the input measurement value exceeds any of the reference values H (Yes in step S62), the calculation unit 13 outputs a command to open the contact of the switch 7a to the contact control unit 15 to perform contact control. The contact of the switch 7a is opened by the part 15 (step S63). On the other hand, when the input measurement value does not exceed any reference value H (No in step S62), the process returns to step S32.

[2-3. effect]
(1) The current / voltage suppressing device 51 of the present embodiment includes switches 7a and 7b provided in series and in parallel with each other in a DC circuit, and a contact control unit 15 that controls these contacts. In parallel with the switch 7a and in series with the switch 7b, the calculation unit 13 is connected to the contact point when the input current value exceeds the current reference value L or when the input voltage value exceeds the voltage reference value L. The controller 15 has a first command for closing the switch 7b, a second command for opening the switch 7a after the first command, and a larger resistance value of the variable resistor 6 after the second command. The contact control unit 15 closes the switch 7b based on the first command, opens the switch 7a based on the second command, and the resistance control unit 14 Based on the third command, the resistance value of the variable resistor 6 is increased.

  By switching to such a variable resistance circuit capable of feedback control, the following effects can be obtained. That is, when power is generated with current flowing through the variable resistor 6, energy loss occurs due to the variable resistor 6, but when a transient phenomenon occurs due to a sudden increase in solar radiation intensity, etc., the open / close connected in series with the variable resistor 6 Since the container 7b is closed, productivity can be improved.

  For example, if the switch 7a is closed and the switch 7b is opened, and then the switch 7b is also opened, power is not supplied to the power conditioner 4, and the power conditioner 4 is stopped and continuous power generation is performed. It may not be possible. However, according to the present embodiment, by closing the switch 7b, it is possible to disperse the current burden while continuing power generation. Further, since the switch 7a is opened after the switch 7b is closed, the impedance can be increased in the circuit, overcurrent and overvoltage can be prevented, and the DC circuit can be protected. Therefore, it is possible to avoid a situation where the fuse is blown and the power generation is stopped, and to realize a reduction in operation cost and an improvement in productivity.

(2) When the input current value exceeds the preset backflow reference value L, the calculation unit 13 performs a first command for causing the contact control unit 15 to close the switch 7b, and opening / closing after the first command. A second command to open the device 7a and a third command to increase the resistance value of the variable resistor 6 after the second command, and the contact control unit 15 to close the switch 7b, The resistor 7a is opened, and the resistance control unit 15 increases the resistance value of the variable resistor 6 based on the third command. Thereby, deterioration of the photovoltaic cell due to the backflow current can be suppressed. Moreover, since it is not necessary to stop the operation of the solar power generation system, productivity can be increased.

(3) The computing unit 13 causes the contact control unit 15 to switch the switches 7a and 7b when either the input current value or the input voltage value exceeds the current reference value H, the voltage reference value H, or the backflow reference value H. The contact control unit 15 opens the switches 7a and 7b based on the command to open. Thereby, even if it is a case where a circuit short circuit and a ground fault generate | occur | produce, protection of each apparatus of a photovoltaic power generation system is attained.

[3. Third Embodiment]
The third embodiment will be described with reference to FIG. The third embodiment is the same as the basic configuration of the second embodiment. In the following, only differences from the second embodiment will be described, and the same parts as those of the second embodiment will be denoted by the same reference numerals and detailed description thereof will be omitted.

  FIG. 10 is an overall configuration diagram of the current-voltage suppressing device according to the third embodiment. The third embodiment is different from the second embodiment in that a current collector 61 is provided on the power conditioner 4 side. The current / voltage suppressing device 52 of the present embodiment is connected to a plurality of paths of the DC circuit, and the current collector 61 aggregates the currents input to the current / voltage suppressing device 52 and outputs them to the outside. In other words, the ratio of the input path to the output path to the current / voltage suppressing device 52 is N: 1 (N is an integer of 2 or more), and the device 52 is connected to the outside through one fuse H.

  The current collector 61 is a power line connected to each path. The outside of the output destination is the current collection box 3 when the current / voltage suppressing device 52 is provided in the connection box 2. Moreover, when the current-voltage suppression apparatus 52 is provided in the current collection box 3, it is a power conditioner 4, and when it is provided in the power conditioner 4, it is an electric power system. Since the current collector 61 is provided, the input current can be collected, so that the number of connected circuits can be reduced.

[4. Fourth Embodiment]
The fourth embodiment will be described with reference to FIG. The fourth embodiment is the same as the basic configuration of the third embodiment. In the following, only differences from the third embodiment will be described, and the same parts as those in the third embodiment will be denoted by the same reference numerals and detailed description thereof will be omitted.

  FIG. 11 is an overall configuration diagram of a current-voltage suppressing device according to the fourth embodiment. The fourth embodiment is different from the fourth embodiment in that the measured current value and voltage value and the state of the contacts of the switches 7a and 7b are stored, and such information is stored in, for example, the photovoltaic power generation system. It is a point transmitted to an external device such as a monitoring device.

  Specifically, the control device 10 of the current / voltage suppressing device 53 includes a storage unit 17 and a communication unit 18. The storage unit 17 is connected to the current measurement unit 11, the voltage measurement unit 12, the calculation unit 13, and the contact state confirmation unit 16, and the measured current value and voltage value, and the contact state of the switches 7a and 7b are displayed. Store at predetermined time intervals. This time interval can be set as appropriate.

  The communication unit 18 is configured by wire or wireless, is connected to the calculation unit 13, and transmits the current value and voltage value stored in the storage unit 17 read by the calculation unit 13 to an external device. In addition, the communication unit 18 notifies an alarm that notifies an abnormality when any of the current value and the voltage value exceeds the current reference value H, the voltage reference value H, or the backflow reference value H. This determination is performed by the calculation unit 13. That is, when it is determined that either the current value or the voltage value exceeds the current reference value H, the voltage reference value H, or the backflow reference value H, the calculation unit 13 stores the current stored for a predetermined time from the storage unit 17. The value, the voltage value, and the contact state are read, and the information is transmitted to the external device to the communication unit 18.

  According to the present embodiment, since the measured current value and voltage value are transmitted to the external device, the solar power generation system can be monitored from the outside. Further, even when an abnormality occurs, an alarm is issued and each measurement value and contact information are transmitted. Therefore, it is easy to take measures by performing analysis or the like, and the operation of the solar power generation system can be facilitated.

[5. Other Embodiments]
In the present specification, a plurality of embodiments according to the present invention have been described. However, these embodiments are presented as examples and are not intended to limit the scope of the invention. The above embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof as well as included in the scope and gist of the invention.

  For example, the current collector 61, the storage unit 17, and the communication unit 18 of the third and fourth embodiments are added to the second embodiment in which two switches 7a and 7b are provided in one path. However, a configuration added to the first embodiment in which one switch 7 is provided in one path is also included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Solar cell string 1G ... Solar cell string group 2 ... Connection box 3 ... Current collection box 4 ... Power conditioner 5, 51, 52, 53 ... Current voltage suppression apparatus 6 ... Variable resistance 7, 7a, 7b ... Switch 8 ... Current measuring instrument 9 ... Voltage measuring instrument 10 ... Control device 11 ... Current measuring unit 12 ... Voltage measuring unit 13 ... Calculating unit 14 ... Resistance control unit 15 ... Contact control unit 16 ... Contact state confirmation unit 17 ... Storage unit 18 ... Communication Unit 61 ... Current collecting unit H ... Fuse S ... Solar power generation unit SW ... Switch T ... DC / AC converter

Claims (11)

A current-voltage suppressing device provided in a DC circuit between a photovoltaic power generation unit having a plurality of solar battery strings and a power conditioner,
A current measuring unit for measuring the current of the DC circuit;
A voltage measuring unit for measuring the voltage of the DC circuit;
A variable resistor provided in series with the DC circuit;
A resistance control unit for changing a resistance value of the variable resistor;
An arithmetic unit having a preset current reference value and voltage reference value;
With
When the current value measured by the current measurement unit exceeds the current reference value, or when the voltage value measured by the voltage measurement unit exceeds the voltage reference value, the calculation unit A current-voltage suppressing device that outputs a command to change a resistance value to the resistance control unit.   The arithmetic unit further has a preset reverse flow reference value, and outputs a command to increase the resistance value of the variable resistor to the resistance control unit when the current value exceeds the reverse flow reference value. The current-voltage suppressing device according to 1. In the DC circuit, a switch provided on the solar cell string side than the variable resistor,
A contact controller for controlling the opening and closing of the contacts of the switch;
With
The computing unit further includes a second current reference value greater than the current reference value, a second voltage reference value greater than the voltage reference value, and a second backflow reference value greater than the backflow reference value, When either the current value or the voltage value exceeds the second current reference value, the second voltage reference value, or the second backflow reference value, the contact point of the switch is connected to the contact control unit. Command to open
The current voltage suppression device according to claim 2, wherein the contact control unit opens the switch based on the command to open. A first switch and a second switch provided in series and in parallel with each other in the DC circuit;
A contact control unit for controlling contacts of the first switch and the second switch;
With
The variable resistor is connected in parallel with the first switch and in series with the second switch,
The computing unit is
When the current value exceeds the current reference value, or when the voltage value exceeds the voltage reference value, the first command to close the second switch in the contact control unit,
A second command to open the first switch after the first command;
A third command for increasing the resistance value of the variable resistor after the second command;
The contact control unit closes the second switch based on the first command, opens the first switch based on the second command,
The current-voltage suppressing device according to claim 1, wherein the resistance control unit increases a resistance value of the variable resistor based on the third command. A first switch and a second switch provided in series and in parallel with each other in the DC circuit;
A contact control unit for controlling contacts of the first switch and the second switch;
With
The variable resistor is connected in parallel with the first switch and in series with the second switch,
The calculation unit further includes a preset reverse flow reference value, and when the current value exceeds the reverse flow reference value, a first command to close the second switch to the contact control unit When,
A second command to open the first switch after the first command;
A third command for increasing the resistance value of the variable resistor after the second command;
The contact control unit closes the second switch based on the first command, opens the first switch based on the second command,
The current-voltage suppressing device according to claim 1, wherein the resistance control unit increases a resistance value of the variable resistor based on the third command. The computing unit further includes a second current reference value greater than the current reference value, a second voltage reference value greater than the voltage reference value, and a second backflow reference value greater than the backflow reference value, When one of the current value and the voltage value exceeds the second current reference value, the second voltage reference value, or the second backflow reference value, the contact controller is provided with the first opening / closing. A command to open the contact of the switch and the second switch,
The current voltage suppression device according to claim 5, wherein the contact control unit opens the first switch and the second switch based on the command to open. A storage unit for storing current values and voltage values measured by the current measurement unit and the voltage measurement unit;
A communication unit that communicates with an external device;
With
The current / voltage suppressing device according to claim 1, wherein the communication unit transmits a current value and a voltage value stored in the storage unit. A contact state confirmation unit for confirming an open state or a closed state of the contact of the switch;
The storage unit stores a state of the contact,
The communication unit notifies an abnormality when either the current value or the voltage value exceeds the second current reference value, the second voltage reference value, or the second backflow reference value. The current voltage suppression device according to claim 7, wherein the state of the contact stored in the storage unit is transmitted to the external device. A storage unit for storing current values and voltage values measured by the current measurement unit and the voltage measurement unit;
A communication unit that communicates with an external device;
With
The current / voltage suppressing device according to claim 4, wherein the communication unit transmits a current value and a voltage value stored in the storage unit. A contact state confirmation unit for confirming an open state or a closed state of contacts of the first switch and the second switch;
The storage unit stores contact states of the first switch and the second switch,
The communication unit notifies an abnormality when either the current value or the voltage value exceeds the second current reference value, the second voltage reference value, or the second backflow reference value. The current voltage suppression device according to claim 9, wherein the state of the contact stored in the storage unit is transmitted to the external device.   The current-voltage suppressing device according to any one of claims 1 to 10, further comprising a current collector that collects current input to each path of the DC path and outputs the current to the outside.

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