KR20220100391A - Power Compensation Device integrated Junction Box for Photovoltaic Module - Google Patents

Abstract

A disclosed junction box-integrated output compensation device for a photovoltaic (PV) module according to the present invention comprises: a case in which a bypass diode is embedded; and a thermoelectric module attached to one outer side surface of the case to dissipate heat from the case. Included inside the case are: a sensor unit for sensing the current, voltage, and temperature of the PV module; a DC/DC converter that converts DC power generated from the PV module into step-down or step-up output; and a microcontroller. The microcontroller includes: an MPPT control unit that continuously monitors the current and voltage supplied by the PV module by the sensor unit, and maintains maximum output power by tracking a maximum power point (MPP) of the PV module by using a maximum power point tracking (MPPT) algorithm; and a thermoelectric module control unit that controls the driving of the thermoelectric module.

Description

Power Compensation Device integrated Junction Box for Photovoltaic Module

The present invention relates to a junction box integrated output compensation device for a solar cell module, and more particularly, a junction box connected to a solar cell module to transmit power to the outside and an output compensation device for compensating the output of the solar cell module are integrated. It relates to a junction box-integrated output compensation device for a solar cell module.

A photovoltaic power generation system converts solar energy into electricity and consists of a photovoltaic (PV) module and a power conditioning system (PCS). In order to transmit solar power DC power to the AC power system, a solar inverter, which is a power converter that converts DC to AC, is used. This solar inverter consists of two parts. First, low voltage solar power DC power is used. The function of increasing the voltage to a high voltage suitable for the next stage and controlling the solar module to generate the maximum power is a DC-DC converter part of the front stage that performs MPPT (Maximum Power Ponit Tracking), It is the DC-AC inverter part of the rear stage that converts or transmits the DC power properly boosted in the front stage into AC power according to the power system.

Most solar power generation systems connect multiple PV modules (panels) in series to form a string and convert it into one large-capacity power converter, which lowers the initial installation cost, but may cause shade or pollutants in some PV modules. There is a problem that the amount of power generation rapidly decreases depending on the degree of this. This is because when some PV modules composing the string have a problem and the output (current) is partially reduced, a current bottleneck occurs due to the characteristics of the series-connected circuit and reduces the total current. Eventually, an abnormality in one part spreads to the whole, which greatly reduces the total power generation. A typical case is the partial shading phenomenon in which some modules are shaded in a roof-type PV system installed on the roof of a house or building. In addition, even in normal weather, the angle of light incident on each PV module varies according to the movement of the sun, and this is a similar phenomenon to the module mismatch, which makes a difference in the generation current.

As a representative output compensation technology to solve this problem, there is a micro-inverter method in which one small inverter (micro inverter) is installed per PV module. The micro-inverter does not convert the DC electricity collected from the entire string into a large-capacity DC-AC conversion at once. The micro-inverter installed in each module performs small-capacity DC-AC conversion, then connects the small-output AC to a common parallel circuit and collects it into the power system. It is a distributed system that transmits Since the micro-inverter method uses a dedicated inverter for each individual module, it can have a maximum power point tracking (MPPT) control function per solar cell module, allowing more power generation to occur.

However, micro-inverters are effective in shady places, but micro-inverters installed for each PV module are DC-AC inverters with the same capacity as the panel, and are more expensive and less efficient than DC-DC converters. After all, it is not profitable to install it in all PV modules, so it is only used when space is limited or there is a lot of shade.

In order to solve the disadvantages (economical) of the micro-inverter method, a micro-converter method in which a small-capacity DC-DC converter (DC optimizer) is installed for each PV module has recently been developed. This is a distributed modular structure that uses a microconverter that converts DC-DC for each PV module, performs primary DC boost, and collects each boosted DC power to perform secondary DC-AC conversion. This microconverter method divides the primary DC-DC converter, which was responsible for the maximum output point tracking (MPPT) and boosting in the conventional centralized string inverter structure, into a number of small-capacity modules, making each microconverter, and installing it for each PV module. It is designed to perform maximum output point tracking (MPPT) control according to the module situation. Therefore, similar to the micro-inverter method, the micro-converter installed in each module can control the maximum power point tracking (MPPT), enabling further development. Since a micro-converter is a DC-DC converter, the price is less than half that of a micro-inverter that converts DC-AC, and it has the advantage of excellent efficiency.

On the other hand, the minimum structure of a solar cell is called a cell, and a form in which a plurality of solar cells are electrically connected is called a PV module. Such a PV module is generally composed of an array structure formed by connecting solar cells in series using a ribbon having conductivity on a module substrate. In addition, the solar cell module is provided with a terminal box (junction box) equipped with connection terminals for collecting power generated from each solar cell string through a conductive bus bar and transmitting it to the power converter.

In this way, an output compensator such as a micro-converter and a junction box are separately provided, and a technology provided in a single junction box has been recently introduced for miniaturization and management efficiency of the device.

Republic of Korea Patent Publication No. 10-1408855 (Registered on Jun. 11, 2014) Republic of Korea Patent Publication No. 10-2017-0118384 (published on October 25, 2017)

The present invention has been devised in view of the above points, and an object of the present invention is to provide a junction box-integrated output compensation device for a solar cell module that integrates a junction box and an output compensation device.

A junction box-integrated output compensation device for a solar cell module according to the present invention for achieving the above object relates to a junction box-integrated output compensation device respectively connected to a solar cell (PV) module, comprising: a case in which a bypass diode is embedded; a thermoelectric module attached to an outer side of the case to dissipate heat from the case; a sensor unit provided inside the case to sense the current, voltage, and temperature of the PV module; a DC/DC converter provided inside the case to change the DC power generated from the PV module to be step-down or step-up and output; The sensor unit continuously monitors the current and voltage supplied by the PV module and uses the Maximum Power Point Tracking (MPPT) algorithm to determine the maximum power point (MPP: Maximun Power Point) of the PV module. a microcontroller including an MPPT control unit to follow and maintain the maximum output power, and a thermoelectric module control unit to control driving of the thermoelectric module; and an optimization control unit for controlling the DC/DC converter to change a duty cycle of the DC/DC converter in real time so as to output a voltage corresponding to the maximum power point tracked by the MPPT control unit. . Here, the MPPT control unit tracks the maximum power point by comparing and analyzing the current and voltage at the maximum power point previously output by the MPPT control unit and the current and current at the DC/DC converter input terminal measured by the phase sensor unit. do.

In addition, the temperature sensor includes a first temperature sensor for detecting the temperature of the PV module, and a second temperature sensor for detecting the temperature inside the case, the microcontroller is the temperature value sensed from the first temperature sensor is set When it exceeds the reference value, it is determined that there is an abnormality and transmits a control command to the converter control unit, further comprising an abnormal state detection unit to turn off a switch in the DC/DC converter to block the operation of the internal circuit, the thermoelectric The module control unit receives the temperature information of the inside of the case from the second temperature sensor and controls to cool the case when the temperature is higher than a set temperature or to maintain a constant temperature inside the case.

Meanwhile, according to the present invention, it further includes a parameter DB in which an optimal voltage value for outputting the maximum power point per current for each temperature is stored, wherein the MPPT control unit detects the current sensor, the voltage sensor, and the first temperature sensor. An optimal voltage value corresponding to the sensed value is extracted from the parameter DB unit.

According to the junction box-integrated output compensation device for a solar cell module according to the present invention, it is possible to pursue miniaturization and cost reduction of the solar power generation system by integrating the output compensation device into the junction box, and also the thermoelectric module on the outside of the junction box case By attaching the junction box, it is possible to effectively dissipate heat when the junction box case becomes high due to the driving of the bypass diode, which has the effect of increasing the efficiency of the PV module.

1 is a schematic view of a junction box-integrated output compensation device for a solar cell module according to an embodiment of the present invention;
2 is a block diagram of a junction box-integrated output compensation device for a solar cell module according to an embodiment of the present invention;
3 and 4 are diagrams for explaining IV and PV characteristics of the solar cell module and tracking of the maximum tracking point of the MPPT control unit.

The above objects, features and other advantages of the present invention will become more apparent by describing preferred embodiments of the present invention in detail with reference to the accompanying drawings. Hereinafter, a junction box-integrated output compensation device for a solar cell module according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 and 2 , the junction box integrated output compensation device for a solar cell module according to an embodiment of the present invention is a case 100 installed on one side of the PV module 10 so as to be connected to the PV module 10 . And, the thermoelectric module 200 attached to one side of the case, the bypass diode 102 respectively installed inside the case 100 , the sensor unit 110 , the DC/DC converter 140 , and the microcontroller 130 . , a converter control unit 140 and a communication unit 150 .

The case 100 is mounted on one side, for example, the back side of the PV module. The inside of the case 100 may be sealed using silicon or the like to prevent moisture penetration of circuit elements. The case 100 is provided with an input terminal so that the conductive line of the solar cell can be connected to a bypass diode 102 to be described later, and an output terminal is provided to output the converted DC power to the outside.

Meanwhile, high heat is generated from the bypass diode 102 or the like during operation of the junction box, and the generated heat may reduce the efficiency of a specific solar cell arranged at a position where the case 100 is attached. In order to prevent this, a heat dissipation plate such as a corrugated structure is conventionally provided in a junction box, but optimal heat dissipation may not be achieved only with the heat dissipation plate having a specific structure.

Therefore, according to the present invention, the thermoelectric module 200 for temperature control is attached to one side of the case so that heat is efficiently dissipated.

The thermoelectric module 200 is attached to one side of the case 100 and serves to radiate heat from the case 100 . As described above, high heat is generated from the bypass diode 102 or the like during operation of the junction box, and the generated heat may reduce the efficiency of a specific solar cell arranged at a position where the case 100 is attached. In the present invention, to prevent this, the heat absorbing surface of the thermoelectric module 200 is disposed to contact the case 100 to cool (dissipate heat) the case 100 . The thermoelectric module 200 is supplied with power by a power supply not shown.

The bypass diode 102 is connected to the PV module 10 and operates in a short-circuit mode to short or open the bypass line when power is supplied, and open to open the bypass line when the power is cut off. mode to operate. That is, the bypass diode prevents a reverse current between the solar cell strings. The number of bypass diodes 102 may vary depending on the number of solar cell strings constituting the PV module, and the detailed configuration and operation of such bypass diodes are widely known in the prior art and are not related to the gist of the present invention. A detailed description will be omitted.

The sensor unit 110 is connected to both ends of the bypass diodes to sense the current and voltage of the PV module. The voltage sensor 114 and the current sensor 112 may be realized by various technologies, for example, using a very low resistance or using a current (voltage) probe.

Meanwhile, the sensor unit 110 may further include a temperature sensor. The temperature sensor is provided in the connection part with the PV module 10 in the case 100, the first temperature sensor 116 for detecting the temperature of the PV module 10, and the case 100 for detecting the temperature inside A second temperature sensor 118 is provided.

Information on the current, voltage, and temperature falsely sensed by the sensor unit 110 is transmitted to the microcontroller 130 . This current and voltage data can be used for system monitoring purposes. And, the temperature data, particularly the temperature data of the PV module, indicates a kind of failure and problem of the PV module, and also acts as a coefficient of output power production.

Also not shown. The sensor unit 110 may further include a sensor for measuring the voltage and current at the output terminal of the DC/DC converter 120 .

The DC/DC converter 140 outputs the DC power generated in the PV module 10 by step-down or step-up. For example, the DC/DC converter 140 may be a buck converter circuit, a boots converter circuit, a buck-boost converter circuit, an N-buck converter circuit, or the like. Since the type and operation of the DC/DC converter are widely known in the prior art and are not related to the gist of the present invention, a detailed description thereof will be omitted.

The microcontroller 130 includes an MPPT control unit 132 , an abnormal state detection unit 134 , and a thermoelectric module control unit 136 .

The MPPT control unit 132 continuously monitors the current and voltage supplied by the PV module 10 and uses the Maximum Power Point Tracking (MPPT) algorithm to the maximum power point ( MPP:Maximun Power Point) to keep the maximum output power. The MPPT algorithm may use all common algorithms, such as, for example, a Perturb and Observe (P&O) algorithm, an Incremental Conductance (IC) algorithm, and the like.

The MPPT control unit 132 may track the maximum power point by comparing and analyzing voltages and currents at the input terminal and the output terminal of the DC/DC converter 120 with each other. In this case, a separate sensor for measuring the voltage and current of the output terminal of the DC/DC converter 120 should be further provided.

However, according to an embodiment of the present invention, the MPPT control unit 132 stores information such as power, current, voltage, etc. of the maximum power point previously output by the MPPT control unit, and the stored previous information and the sensor unit 110 . The maximum power point can be tracked by comparing and analyzing the current voltage and current at the input terminal of the DC/DC converter 120 measured by the current sensor 112 and the voltage sensor 114 of the .

3 schematically shows the characteristics of a current versus voltage curve (solid line portion) in a solar cell, and FIG. 4 shows the curves for three different temperature conditions. Here, the temperature may correspond to the insolation condition. In addition, the dotted line indicates a power scale curve corresponding to each curve, and is determined by the product of voltage and current.

Referring to FIG. 4 , it can be seen that, for all temperature conditions, when the voltage is increased to a certain extent, the current rapidly drops. As the current value drops, the power scale also drops sharply. In order to increase the output efficiency of the PV module, it is necessary to track the maximum power point in the graph of the figure and control so that the corresponding voltage can be output from the output terminal. The maximum power point corresponds to the point where the product of the sensed voltage and current is greatest.

When the detection value of the temperature sensor (first temperature sensor) exceeds a predetermined reference value, the abnormal state detection unit 134 determines that there is an abnormality and transmits a control command to the converter control unit 140 , and the DC/DC converter 120 ) to block the operation of the internal circuit by turning off the switch in the internal circuit to block the power transmission to the outside or to block the operation of the PV module.

The thermoelectric module controller 136 controls the temperature of the thermoelectric module 200 . The thermoelectric module control unit 136 receives the temperature information of the inside of the case from the second temperature sensor 118 and controls to cool the case when the temperature is higher than a set temperature or to maintain a constant temperature inside the case. As described above, the case 100 may be maintained at a constant temperature by the thermoelectric module 200 and the thermoelectric module controller 136 . Therefore, it is possible to prevent the efficiency of the solar cell at a specific location from being reduced due to the high heat generated by the existing bypass diode or the like.

The converter control unit 140 controls the DC/DC converter 120 to output a voltage corresponding to the maximum power point according to the maximum power point followed by the MPPT control unit 132 . That is, the converter control unit 140 transmits a duty cycle control signal to the DC/DC converter 120 according to the maximum power point calculated by the MPPT control unit 132 to adjust the output voltage.

On the other hand, when the junction box integrated output compensation device according to the embodiment of the present invention is formed integrally with the PV module 10, it may be referred to as a MIC (Modul Integrated Converter) circuit. In addition, in the junction box integrated output compensation device, some components except for the DC/DC converter may be implemented as a system on chip (SOC).

The communication unit 150 serves to transmit various types of sensing data of the sensor unit 110 to an external control server. Such transmitted information enables real-time monitoring and analysis of the PV module 10 . Here, each junction box case has a unique ID, thereby facilitating identification and individual monitoring and individual maintenance of the PV module.

The operation of the junction box-integrated output compensation device for a solar cell module according to an embodiment of the present invention having the above structure will be described as follows.

First, the voltage sensor and the current sensor of the sensor unit 110 continuously sense the current and voltage values of the PV module. This information is transmitted to the MPPT control unit 132, the MPPT control unit 132 tracks the maximum power point from the sensed current and voltage values, and the converter control unit 140 is the maximum power point tracked by the MPPT control unit 132. The output of the DC/DC converter 120 is controlled so that a corresponding voltage is output.

Here, when the detected value of the temperature sensor exceeds the reference value, the converter control unit 140 may turn off the DC/DC converter 120 .

In the case of such an embodiment, it corresponds to a configuration in which the maximum power point is directly searched from the real-time sensed voltage and current values.

Another embodiment of searching for a maximum power point using pre-stored DB information will be described.

To this end, the separate parameter DB unit (not shown) is included.

An optimal voltage value for outputting a maximum power point per current for each temperature is previously stored in the parameter DB unit. That is, the parameter DB unit stores the same content as in the graph of FIG. 4 .

In this case, the MPPT control unit 132 extracts an optimum voltage value corresponding to the sensed values from the voltage sensor, the current sensor, and the first temperature sensor from the parameter DB unit. Thereafter, the converter control unit 140 controls to output the extracted optimal voltage value from the output terminal. For example, if the currently sensed temperature and current values are known, the corresponding current and voltage curves can be found, and the optimal voltage value for this curve (for example, the voltage value corresponding to the point P corresponding to the maximum power point) ) can be extracted.

The operation of the junction box-integrated output compensation device for a solar cell module according to another embodiment of the present invention as described above is as follows. First, the voltage and current sensor senses the current and voltage values of the PV module 10 . And, the first temperature sensor senses the temperature value of the PV module 10 . Thereafter, the MPPT control unit 132 extracts the optimum voltage value corresponding to the sensing values sensed by the voltage and current sensors and the temperature sensor from the parameter DB unit. Next, the converter control unit 140 controls the DC/DC converter 140 to output the extracted optimal voltage value from the output terminal. Of course, when the detected value of the temperature sensor exceeds the reference value, the switch built in the DC/DC converter 140 may be turned off.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to the specific embodiments described above. That is, a person of ordinary skill in the art to which the present invention pertains can make numerous changes and modifications to the present invention without departing from the spirit and scope of the appended claims, and all such appropriate changes and modifications are possible. Equivalents are to be considered as falling within the scope of the present invention.

10. PV module 100. Case
102. Bypass diode 110. Sensor unit
112. Current sensor 114. Voltage sensor
116. First temperature sensor 118. Second temperature sensor
120. DC/DC converter 130. Microcontroller
132. MPPT control unit 134. Abnormal state detection unit
136. Thermoelectric module control unit 140. Optimization control unit

Claims (3)

It relates to a junction box-integrated output compensation device connected to each solar cell (PV) module,
a case in which a bypass diode is built-in;
a thermoelectric module attached to an outer side of the case to dissipate heat from the case;
a sensor unit provided inside the case to sense the current, voltage, and temperature of the PV module;
a DC/DC converter provided inside the case to change the DC power generated from the PV module to be step-down or step-up and output;
The sensor unit continuously monitors the current and voltage supplied by the PV module and uses the Maximum Power Point Tracking (MPPT) algorithm to determine the maximum power point (MPP: Maximun Power Point) of the PV module. a microcontroller including an MPPT control unit to follow and maintain the maximum output power, and a thermoelectric module control unit to control driving of the thermoelectric module; and,
An optimization control unit for controlling to change the duty cycle of the DC/DC converter in real time so that the DC/DC converter outputs a voltage corresponding to the maximum power point tracked by the MPPT control unit;
The MPPT control unit compares and analyzes the current and voltage at the maximum power point previously output by the MPPT control unit and the current and current at the DC/DC converter input terminal measured by the phase sensor unit to track the maximum power point. Junction box integrated output compensation device for solar cell module, characterized in that.
The method of claim 1,
The temperature sensor includes a first temperature sensor for detecting the temperature of the PV module, and a second temperature sensor for detecting the temperature inside the case,
When the temperature value sensed by the first temperature sensor exceeds a set reference value, the microcontroller determines that there is an abnormality and sends a control command to the converter control unit to turn off a switch in the DC/DC converter to turn off the internal circuit Further comprising an abnormal state detection unit to block the operation of,
The thermoelectric module control unit receives the temperature information of the inside of the case from the second temperature sensor and controls to cool the case when the temperature is higher than a set temperature, or to control the inside of the case to maintain a constant temperature. All-in-one output compensation device.
3. The method of claim 2,
It further includes a parameter DB in which the optimum voltage value for outputting the maximum power point per current for each temperature is stored;
The MPPT control unit extracts an optimum voltage value corresponding to the sensed values sensed from the current sensor, the voltage sensor, and the first temperature sensor from the parameter DB unit.

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