JP2016101050A - Booster connection box and power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a booster connection box that enables a power conditioner to satisfy an operating continuation requirement in a period of specific accident when voltage momentarily decreases, and to provide a power generation system using the booster connection box.SOLUTION: In a booster connection box 1 that inputs output voltage of a solar cell module to a power condition 2 by boosting it to a target voltage by means of a booster circuit 7, a control section 8, which exerts proportional control and integral control and generates from a target voltage and an output voltage of the booster circuit 7 a boosting control signal to be applied to the booster circuit 7, exerts specific control when output stop of the power condition 2 is detected. In specific control, a boosting control signal is generated using a value obtained by averaging integral values in integral control in a fixed period before the specific control, and this boosting control signal is applied to the booster circuit 7 for a predetermined period. Thus, when a power system 3 resumes from a momentary voltage decrease, a power condition 2 is able to maintain 80% or more of power output before the momentary voltage decrease.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a booster junction box and a power generation system, and more specifically, a booster junction box having a booster function that supplies output voltages of a plurality of power generation units to a power conditioner, and power generation using the booster junction box About the system.

  In recent years, a distributed power source such as a solar power generation system has been rapidly spread. Such a distributed power supply is designed to be disconnected from the power system in the event of a system failure. However, a large number of distributed power supplies can be used in the event of a system disturbance such as an instantaneous voltage drop (for example, an instantaneous power failure with a power failure time of 1 second or less). If the system is disconnected at the same time, the power quality of the system may be reduced (in some cases, causing a large-scale power outage). (Fault Ride Through: hereinafter referred to as “FRT requirement”) is defined, and a power conversion device (power conditioner) of a distributed power source is designed to satisfy this FRT requirement (for example, Patent Documents) 1).

JP 2011-101455 A

  However, such a conventional configuration has the following problems, and improvements have been desired.

  That is, in a photovoltaic power generation system for residential use, a plurality of solar cell modules (a plurality of solar cell modules are connected in series or in parallel) in relation to the installation location of the solar cell module (such as a roof structure on which the solar cell module is installed). May be connected to the inverter.

  FIG. 4 shows an example of a solar power generation system using a plurality of solar cell modules. As shown in FIG. 4, when a plurality of solar cell modules a, a,... Are connected to a power conditioner c, each solar cell module is interposed between the solar cell modules a, a,. A junction box (in the illustrated example, a step-up junction box b) is provided for combining the outputs of a, a,... into a power conditioner c.

  The step-up junction box b is a junction box having a function (step-up function) for supplying the output voltage of each solar cell module a, a,... To the power conditioner c. The connection box b is provided with at least one booster circuit e. Each booster circuit e is provided with a control unit (not shown). This control unit controls the boosting operation of the booster circuit, and the output voltages of the booster circuits e are aligned.

  In such a photovoltaic power generation system to which the booster connection box b is connected, even if the power conditioner c operates so as to satisfy the FRT requirement due to the occurrence of an instantaneous voltage drop in the system d, the booster connection box b Therefore, when the power conditioner c tries to restore the output according to the FRT requirement, there is a possibility that a predetermined output power cannot be obtained.

  The present invention has been made in view of such conventional problems, and the object of the present invention is to provide a booster junction box in which a power conditioner can satisfy a predetermined FRT requirement when an instantaneous voltage drop occurs, and The object is to provide a power generation system using a step-up junction box.

  In order to achieve the above object, a booster junction box according to claim 1 of the present invention is a booster junction box that boosts an output voltage of a power generation unit to a target voltage by a booster circuit and inputs the boosted voltage to a power conditioner. A control unit that performs proportional control and integral control from the target voltage and the output voltage of the booster circuit, and performs boosting control to increase or decrease the duty ratio of a control signal applied to the booster circuit, and the control unit includes: When the output stop of the power conditioner is detected, the control configuration is configured to switch the boost control to a predetermined specific control, and the specific control is performed during a certain period before the integral value in the integral control is switched to the specific control. A control signal is generated by changing the integral value of the integral control to an average value, and this control signal is configured to be given to the booster circuit for a predetermined period. And wherein the Rukoto.

  In the step-up connection box according to the first aspect, when the control unit detects the output stop of the power conditioner, the control unit switches the step-up control for the step-up circuit to a predetermined specific control. And in this specific control, a control part produces | generates a control signal using the value which averaged the integral value of the fixed period before the output stop of a power conditioner as an integral value of the integral control in the pressure | voltage rise control of a voltage booster circuit. That is, the booster circuit is forcibly returned to the state before the occurrence of the instantaneous voltage drop, and the input power of the power conditioner is quickly increased to the state before the occurrence of the instantaneous voltage drop. Therefore, when the power system returns from the instantaneous voltage drop, the power conditioner can maintain the output power of 80% or more before the instantaneous voltage drop, and can perform an operation satisfying the FRT requirement.

  The step-up junction box according to claim 2 of the present invention is the step-up junction box according to claim 1, wherein the control unit increases the output voltage of the power generation unit, decreases the output current of the power generation unit, or The output stop of the power conditioner is detected based on a decrease in the output power of the power generation unit.

  In the step-up connection box according to claim 2, the control unit of the step-up connection box stops the output of the power conditioner, increases the output voltage of the power generation unit, decreases the output current of the power generation unit, or reduces the output power of the power generation unit. Since the detection is based on a decrease (including a combination of these phenomena), the boost junction box alone (without communication with the inverter) stops the inverter output, and thus the power system instantaneously. A voltage drop can be detected.

  The step-up connection box according to claim 3 of the present invention is the step-up connection box according to claim 1 or 2, wherein the specific control is a period before the duty ratio of the control signal is switched to the specific control, It is limited to be equal to or less than the maximum value of the duty ratio of the control signal in the second fixed period, which is the same period as the fixed period or a different period.

  In the step-up junction box according to claim 3, the duty ratio of the control signal at the time of specific control is limited so as not to exceed the maximum value of the duty ratio of the control signal before the instantaneous voltage drop occurs. Can perform stable MPPT control.

  A power generation system according to a fourth aspect of the present invention is characterized in that a plurality of power generation units and a power conditioner are connected via the step-up connection box according to any one of the first to third aspects. .

  According to the present invention, when the instantaneous voltage drop of the power system, the control unit of the boost junction box detects the output stop of the power conditioner and performs the boost control in preparation for the output return of the power conditioner. When returning from, the power conditioner can perform an operation satisfying the FRT requirement (for example, maintain an output power of 80% or more before the instantaneous voltage drop).

It is a schematic block diagram which shows an example of the solar energy power generation system using the pressure | voltage rise junction box which concerns on this invention. It is a schematic diagram which shows the process of determining the maximum value of the duty ratio of the control signal at the time of the specific control of the same step-up connection box. It is explanatory drawing which shows the relationship between the electric power-voltage characteristic of a solar cell module, and the duty ratio of the control signal with respect to a booster circuit. It is a schematic block diagram which shows an example of the conventional solar power generation system.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration of a photovoltaic power generation system (power generation system) using a boost junction box 1 according to the present invention.

  The solar power generation system shown in FIG. 1 includes a solar cell module (power generation unit) (not shown), a step-up connection box 1, a power conditioner 2, and a power system 3 as main parts. Here, the solar cell module means a module formed by packaging a plurality of solar cells, but the solar cell module in the following description is a solar cell formed by connecting a plurality of solar cell modules in series or in parallel. An array is also included.

  The step-up connection box 1 is a connection box having a step-up function that combines outputs from a plurality of solar cell modules into one and aligns the output voltage of each solar cell module. In the illustrated example, the step-up connection box 1 has a step-up function. This is composed of one main circuit 4 that is not present and three sub-circuits 5 that have a boosting function.

  The main circuit 4 is a circuit for connecting a solar cell module having a higher output voltage among a plurality of solar cell modules, and the main circuit 4 directly adjusts the output voltage of the solar cell module (without increasing the voltage). ) It is configured to output. In the main circuit 4, a power line connected to the positive electrode (P electrode) of the solar cell module is provided with a backflow prevention diode 6. The diode 6 can also be provided on a power line connected to the negative electrode (N pole) of the solar cell module as shown by the chain line in FIG.

  The sub circuit 5 is a circuit for connecting a solar cell module other than the solar cell module connected to the main circuit 4. The sub circuit 5 includes a booster circuit 7 and a control unit 8 of the booster circuit 7. The input voltage sensor 9 for detecting the input voltage Vin from the solar cell module, the input current sensor 10 for detecting the input current Iin from the solar cell module, and the output voltage sensor 11 for detecting the output voltage Vout of the booster circuit 7 Is provided. Further, in the sub circuit 5, the power line connected to the positive electrode of the solar cell module is provided with a backflow prevention diode 6 as in the main circuit 4.

  The step-up circuit 7 is constituted by a DC / DC converter circuit whose step-up operation is controlled by a step-up control signal (control signal) S given from the control unit 8. The control unit 8 is a control device that controls the boosting operation of the booster circuit 7 and includes a microcomputer (not shown) as a control center. This microcomputer is configured to output a PWM signal as the boost control signal S, and performs boost control of the boost circuit 7 by increasing or decreasing the duty ratio of the PWM signal.

  Specifically, the control unit 8 feedback-controls the booster circuit 7 so that the output voltage Vout of the booster circuit 7 becomes a predetermined target voltage Vt. This feedback control includes proportional control and integral control. In the integral control, past information is integrated. The target voltage Vt in this feedback control is the output voltage of the main circuit 4, so that the output voltage of the solar cell module connected to the sub circuit 5 is the same as that of the solar cell module connected to the main circuit 4. It is designed to match the output voltage. Then, the output side of each power line of the main circuit 4 and the sub circuit 5 is connected in the boost connection box 1 to be combined into one and output from the boost connection box 1 as one output.

  In the present embodiment, the control unit 8 periodically acquires the following data during normal control (when the power system 3 is normal) in relation to the specific control described below, and the acquired data is transmitted to the control unit 8. Is configured to be stored in the internal memory.

A. The section maximum value of the boost control signal S is controlled by the control unit 8 during a normal control, for a predetermined period T1 (specifically, a period set between about 100 milliseconds to 1 second, for example, 100 milliseconds). Each time, the maximum value of the boost control signal S in the period T1, that is, the maximum value of the duty ratio of the PWM signal is calculated, and the calculated value is stored as the section maximum value Smax of the boost control signal S (FIG. 2). (See section Maximum section). The section maximum value Smax is not adopted as the section maximum value Smax when the output of the power conditioner 2 is stopped (when the input voltage Vin increases rapidly in FIG. 2). In storing the section maximum value Smax, an area for storing at least one section maximum value Smax is set in the memory of the control unit 8, and a new section maximum value Smax is calculated. The old data is deleted in order and the new data is overwritten. Here, if the fixed period T1 is too short (for example, less than 100 milliseconds), the pulsation of the duty ratio due to the composite element is ignored, and if it is too long (for example, exceeds 1 second). And) there is a risk that it will not respond to sunshine fluctuations.

B. The integration section average value of the boost control signal S The controller 8 calculates the average of the integration values of the integration control in the period T2 for each predetermined period T2 (second constant period) during normal control. The value is stored as the integral interval average value Sia of the boost control signal S. The fixed period T2 used for calculating the integration interval average value Sia may be different from the fixed period T1, but in the present embodiment, it is set to the same period (T2 = T1) as the fixed period T1. . Further, when storing the integration interval average value Sia, an area for storing at least one integration interval average value Sia is set in the memory of the control unit 8, and a new integration interval average value Sia is calculated. Along with this, old data is deleted in order and new data is overwritten.

  The power conditioner 2 is a power converter for connecting the DC power output from the booster connection box 1 to the power system 3, and is a DC / DC that boosts the voltage of the DC power input from the booster connection box 1. DC converter 20, DC / AC inverter 21 that converts DC power boosted by DC / DC converter 20 into AC power that can be linked to power system 3, and a display unit that displays the operation status of power conditioner 2 22 and a PC control unit 23 that controls the operation of each unit of the power conditioner 2 as main units. In the figure, reference numeral 24 denotes a backflow prevention diode, and reference numeral 25 denotes a DC link capacitor for connecting the DC / DC converter 20 and the DC / AC inverter 21.

  Since the configuration of the power conditioner 2 is well known, a detailed description thereof is omitted here, but the PC control unit 23 shown in the present embodiment disconnects the power conditioner 2 when the power system 3 is disturbed. FRT requirements (FRT requirements shown in “system interconnection rules” stipulated by the Japan Electric Association) are set to meet the requirements.

  Next, the operation of the step-up junction box 1 when the output of the power conditioner 2 is stopped according to the FRT requirement in the photovoltaic power generation system configured as described above will be described.

  In the step-up connection box 1 shown in this embodiment, when the output of the power conditioner 2 is stopped, each control unit 8 of the step-up connection box 1 stops the output by any one of the following methods (1) to (3). Alternatively, detection and determination are performed by a combination of the methods shown in (1) to (3). The detection values of the sensors shown in the following explanations (1) to (3) are all section average values every 100 milliseconds, and the data to be compared is separated by about 1 second (that is, about 1 second). The average value of the section (previously detected) is used.

(1) Abrupt increase in input voltage Vin The control unit 8 stops the output of the power conditioner 2 when the input voltage Vin (that is, the output voltage of the solar cell module) increases beyond a predetermined threshold value XVin. It is determined that The threshold value XVin in this determination is determined based on the voltage-current (V-I) characteristics of the solar cell module. The threshold value XVin is stored in the control unit 8 in advance.

(2) Abrupt decrease in input current Iin The control unit 8 stops the output of the power conditioner 2 when the input current Iin (that is, the output current of the solar cell module) decreases beyond a predetermined threshold value XIin. It is determined that The threshold value XIin in this determination is also determined based on the voltage-current characteristics of the solar cell module, and the value is stored in the control unit 8 in advance.

(3) Abrupt decrease in input power Pin The control unit 8 stops the output of the power conditioner 2 when the input power Pin (that is, the output power of the solar cell module) decreases beyond a predetermined threshold value XPin. It is determined that The threshold value XPin in this determination is determined based on the FRT requirement. For example, when the minimum ratio of the FRT requirement is 54.7% of the decrease from the phase voltage 95V to 52V, it is set to be less than about 60%. The value of the threshold value XPin is also stored in the control unit 8 in advance.

  Then, when each control unit 8 detects the output stop of the power conditioner 2 by the methods (1) to (3), each control unit 8 then determines the integration interval average value as the integration value of the integration control. A boost control signal S is generated using Sia, and the generated boost control signal S is supplied to the booster circuit 7. That is, the control unit 8 performs control (specific control) for forcibly changing the duty ratio of the boost control signal S to the state before the output of the power conditioner 2 is stopped, and the boost circuit 7 is controlled in this specific control state. The boosting operation is performed to increase the input power at once.

  Further, during the execution of the specific control, each control unit 8 limits the duty ratio of the boost control signal S so that the boost control signal S does not exceed the section maximum value Smax. That is, in the power-voltage (P-V) characteristic of the solar cell module, as shown in FIG. 3, the output power increases from the open end to the maximum power point (MPP) due to the increase of the duty ratio of the boost control signal S. However, if the maximum power point is exceeded, the duty ratio increases and the output power decreases. And if the output voltage of the solar cell module is too close to 0V, it may take time to reach the maximum power point. Therefore, each control unit 8 restricts the output voltage of the solar cell module from approaching 0V by limiting the duty ratio of the boost control signal S.

  Then, after the control unit 8 determines that the output of the power conditioner 2 is stopped, the specific control is performed for a predetermined period T3 (for example, about 1.5 seconds), and then each control unit 8 Then, the restriction on the boost control signal S is released, and the normal control is started. Here, the predetermined period T3 is set according to the FRT requirement.

  Thus, in the photovoltaic power generation system according to the present invention, when the control unit 8 detects the output stop of the power conditioner, the boost control is switched to the specific control, and the boost circuit 7 is in a state before the occurrence of the instantaneous voltage drop. The power is forcibly returned, and the input power of the power conditioner 2 quickly increases to the state before the instantaneous voltage drop occurs. Therefore, when the power system returns from the instantaneous voltage drop, the power conditioner 2 can maintain 80% or more of output power before the instantaneous voltage drop, and can perform an operation satisfying the FRT requirement. .

  The above-described embodiment shows a preferred embodiment of the present invention, and the present invention is not limited to this, and various design changes can be made within the scope of the invention.

  For example, in the above-described embodiment, the case where a solar cell module is used as the power generation unit has been described. However, the power generation unit may be configured by a power generation device that generates DC power, for example, a solar cell such as a wind power generation device. It is also possible to configure with a power generation unit other than the module.

  In the above-described embodiment, the boost junction box 1 uses a circuit that does not have a boost function as the main circuit 4a. However, the main circuit 4a can also have a boost function. That is, the main circuit 4a can be provided with the booster circuit 7, the control unit 8, the input voltage sensor 9, the input current sensor 10, and the output voltage sensor 11. When the main circuit 4 has a boosting function as described above, the boosting operation of the boosting circuit 7 of the main circuit 4 is stopped.

  In the above-described embodiment, the case where the booster connection box 1 is configured by one main circuit 4 and three subcircuits 5 has been described. However, the booster connection box 1 includes at least one subcircuit. 5 (a circuit having a boosting function) may be provided, and the number of the sub-circuits 5 can be changed as appropriate.

1 Booster Connection Box 2 Power Conditioner 3 Power System 4 Main Circuit 5 Subcircuit 6, 24 Diode 7 Booster Circuit 8 Control Unit 9 Input Voltage Sensor 10 Input Current Sensor 11 Output Voltage Sensor 20 DC / DC Converter 21 DC / AC Inverter 22 Display unit 23 PC control unit

Claims (4)

In the boosting junction box that boosts the output voltage of the power generation unit to the target voltage by the booster circuit and inputs the boosted voltage to the power conditioner.
From the target voltage and the output voltage of the booster circuit, a proportional control and an integral control are performed, and a control unit that performs boost control to increase or decrease the duty ratio of a control signal applied to the booster circuit,
The control unit includes a control configuration that switches the boost control to a predetermined specific control when detecting an output stop of the power conditioner,
The specific control generates a control signal by changing the integral value in the integral control to a value obtained by averaging the integral value of the integral control in a certain period before switching to the specific control. A step-up junction box comprising control provided to the step-up circuit. The control unit detects an output stop of the power conditioner based on an increase in output voltage of the power generation unit, a decrease in output current of the power generation unit, or a decrease in output power of the power generation unit. The step-up junction box according to claim 1. The specific control is a period before the duty ratio of the control signal is switched to the specific control, and is the same as or different from the predetermined period, and the maximum duty ratio of the control signal in the second constant period 3. The step-up junction box according to claim 1, wherein the step-up junction box is limited to be equal to or less than a value.   A power generation system, wherein a plurality of power generation units and a power conditioner are connected via the step-up connection box according to any one of claims 1 to 3.

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