Power conversion device

Abstract

A power conversion device according to one embodiment of the present invention comprises: an input unit for receiving a voltage generated in a photovoltaic power generation panel; a power conversion unit for converting an input voltage input into the input unit; the output unit is used for outputting the converted voltage to a system or a load; and a voltage discharge unit connected to the input unit to discharge the input voltage.

Description

Technical Field

[0001] The present invention relates to a power conversion device, and more particularly, to a power conversion device and a photovoltaic power generation system capable of rapidly reducing voltage when abnormal voltage occurs. Background Art

[0002] Photovoltaic power generation is an eco-friendly way of energy generation, widely used to replace existing chemical power generation or nuclear power generation. Photovoltaic power generation can be a stand-alone type in which the battery is connected to a converter or a connection type in which it is connected to the grid. Stand-alone power generation is generally composed of solar cells, storage batteries, and power conversion devices, while the grid connection system is configured to be connected to a commercial power source so that power can be exchanged with the load grid line.

[0003] In the event of a fire or other abnormality in a photovoltaic panel, the voltage must be reduced to below a certain level within a short period of time to protect workers from electric shock and other causes during subsequent processing. This requires a technology that can detect abnormal voltage and safely reduce the voltage. Summary of the invention Technical Topics

[0004] The technical problem to be solved by the present invention is to provide a power conversion device and a photovoltaic power generation system which can quickly reduce the voltage when an abnormal voltage occurs. Technical Solution

[0005] According to one embodiment of the present invention, a power conversion device includes: an input unit for receiving a voltage generated in a photovoltaic power generation panel; a power conversion unit for converting an input voltage input into the input unit; an output unit for outputting the converted voltage to a system or a load; and a voltage discharge unit connected to the input unit to discharge the input voltage.

[0006] Furthermore, an input unit is connected to the MLPE to receive an input voltage, and the MLPE optimizes the voltage of the photovoltaic power generation panel.

[0007] Furthermore, the input voltage is a first DC voltage, wherein the power conversion unit may include: a DC-DC converter unit that converts the first DC voltage into a second DC voltage; and an inverter unit that converts the second DC voltage into a first AC voltage.

[0008] Furthermore, the power conversion device may include a control unit which operates the voltage discharge unit according to a state of the input voltage.

[0009] In addition, the control unit monitors the input voltage, and when the input voltage is lower than the first voltage, may shut down the operation of the power conversion unit and operate the voltage discharge unit.

[0010] Furthermore, the voltage discharge unit may include: a switch unit which is turned on when the input voltage is lower than the first voltage; and a resistance element which discharges the input voltage to be lower than the second voltage according to the operation of the switch unit.

[0011] In addition, the voltage discharge unit may include an RSD execution unit which performs a rapid shutdown (RSD) on the input voltage.

[0012] In order to solve the above technical problems, a photovoltaic power generation system according to one embodiment of the present invention includes: at least one photovoltaic power generation panel; and a power conversion module, which converts the voltage generated by the photovoltaic power generation panel and outputs the voltage to a power grid or a load, wherein the power conversion module includes: an input unit, which receives the voltage generated by the photovoltaic power generation panel; a power conversion unit, which converts the input voltage input to the input unit; an output unit, which outputs the converted voltage to the power grid or the load; and a voltage discharge unit, which is connected to the input unit to discharge the input voltage.

[0013] Furthermore, the photovoltaic power generation system includes a MLPE which optimizes a voltage of the photovoltaic power generation panel, wherein an input unit is connected to the MLPE to receive an input voltage.

[0014] In addition, the power conversion module may include a control unit which operates the voltage discharge unit according to a state of the input voltage.

[0015] In addition, the control unit may monitor the input voltage, and when the input voltage is lower than the first voltage, shut down the operation of the power conversion unit and operate the voltage discharge unit. Beneficial Effects

[0016] According to an embodiment of the present invention, the inverter itself monitors and performs RSD operations without adding a module configured as a separate accessory for RSD operations or intercommunication with MLPE, thereby achieving intercommunication with the PV array and MLPE, thereby facilitating system compatibility and PVRSS certification. In addition, since the RSD function is performed in the inverter, there is no need to perform functional safety separately in the MLPE, thereby reducing the time, manpower and cost required to perform functional safety. In addition, since RSD operation does not require separate communication, component CI effect occurs, and system compatibility is good not only with PV arrays without PLC communication but also with MLPEs that do not apply Sunspec, and can respond to system compatibility certification. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a block diagram of a power conversion apparatus according to an embodiment of the present invention.

[0018] Figure 2 is a block diagram of a power conversion apparatus according to an embodiment of the present invention.

[0019] Figure 3 is a block diagram of a power conversion device according to a comparative example of the present invention.

[0020] Figure 4 and Figure 5 is a block diagram of a power conversion apparatus according to an embodiment of the present invention.

[0021] Figure 6 An application example of the voltage discharge circuit according to the embodiment of the present invention is shown.

[0022] Figure 7 is a diagram for explaining voltage discharge according to an embodiment of the present invention.

[0023] Figure 8 is a block diagram of a photovoltaic power generation system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0025] However, the technical idea of ​​the present invention is not limited to some embodiments to be described, but can be implemented in various forms, and within the scope of the technical idea of ​​the present invention, one or more of the constituent elements can be selectively combined or replaced between the embodiments.

[0026] In addition, unless explicitly defined and described, the terms (including technical terms and scientific terms) used in the embodiments of the present invention may be interpreted as meanings that can be generally understood by those skilled in the art, and commonly used terms such as terms defined in dictionaries may be interpreted in consideration of the contextual meaning of the relevant technology.

[0027] In addition, the terms used in this specification are used to describe the embodiments and are not intended to limit the present invention. In this specification, unless otherwise specified in a phrase, a singular form may include a plural form, and when described as "at least one (or more than one) of A and B and C", one or more of all combinations that can be combined with A, B and C may be included.

[0028] Furthermore, when describing the components of the embodiments of the present invention, terms such as first, second, A, B, (a), (b), etc. may be used.

[0029] These terms are only intended to distinguish a component from other components, and these terms do not limit the nature, order, or sequence of the components.

[0030] Furthermore, when a component is described as being “connected,” “coupled” or “interconnected” to other components, the component is not only directly connected, coupled or interconnected to the other components but may also include a situation where another component is “connected,” “coupled” or “interconnected” between the other components.

[0031] Furthermore, in the case of describing that it is formed or disposed “on” or “below” each component, the meaning of “on” or “below” includes not only the case where the two components are directly in contact, but also the case where one or more other components are formed or disposed between the two components. Furthermore, when expressed as “on” or “below”, it may include not only the meaning of the upward direction based on one component, but also the meaning of the downward direction.

[0032] The modified embodiment according to the present embodiment may include some components of each embodiment and some components of other embodiments. That is, the modified embodiment may include one embodiment in various embodiments, but some components may be omitted and some components of other corresponding embodiments may be included. Alternatively, it may be the opposite. The features, structures, effects, etc. described in the embodiments are included in at least one embodiment and are not necessarily limited to one embodiment. In addition, the features, structures, effects, etc. exemplified in each embodiment may be combined or modified and implemented in other embodiments by a person of ordinary skill in the art to which the embodiments belong. Therefore, the content related to such combination and modification should be interpreted as being included in the scope of the embodiments.

[0033] Figure 1 is a block diagram of a power conversion device according to an embodiment of the present invention; Figure 2 is a block diagram of a power conversion device according to an embodiment of the present invention; Figure 3 is a block diagram of a power conversion device according to a comparative example of the present invention; Figure 4 and Figure 5 is a block diagram of a power conversion device according to an embodiment of the present invention; Figure 6 An application example of a voltage discharge circuit according to an embodiment of the present invention is shown; and Figure 7 is a diagram for explaining voltage discharge according to an embodiment of the present invention.

[0034] The power conversion device 110 according to one embodiment of the present invention is composed of an input unit 111 , a power conversion unit 112 , a voltage discharge unit 114 , and may include an output unit 113 and a control unit 115 .

[0035] The power conversion device 110 according to the embodiment of the present invention may be an inverter. In a photovoltaic power generation system, it may be an inverter that receives voltage from the photovoltaic power generation panel 120 or the MLPE 140 and converts the voltage required by the system (grid) 130 or a load (not shown).

[0036] The input unit 111 receives a voltage generated by the photovoltaic power generation panel 120 or is connected to the MLPE 140 that optimizes the voltage of the photovoltaic power generation panel and receives a voltage from the MLPE 140. The solar cell module of the photovoltaic power generation panel 120 has different maximum power points according to the amount of sunshine, temperature, etc. In order to operate the solar cell at the maximum power point, a module-level power electronic device (MLPE) that performs maximum power point tracking (MPPT) control in units of modules may be used. The power converter connected to the photovoltaic power generation panel 120 on which the MLPE 140 is mounted receives a voltage through the MLPE 140.

[0037] The power conversion unit 112 converts the input voltage input to the input unit 111. It converts the input voltage into a voltage required by the power grid 130 or the load. The power conversion unit 112 may be an inverter. The power conversion unit 112 may convert the input voltage, which is a first DC voltage, into a first AC voltage. The first AC voltage may be the rated voltage of the power grid 130 or a voltage suitable for the load. Here, the load may be a device driven by using a voltage generated by a photovoltaic power generation panel. For example, it may be a device in a building or home where a photovoltaic power generation panel is installed.

[0038] The power conversion unit 112 may include a DC-DC converter unit 116 and an inverter unit 117. The DC-DC converter unit 116 may convert a first DC voltage into a second DC voltage. Here, the input voltage input to the input unit 111 is a first DC voltage, and the DC-DC converter unit may convert the first DC voltage into a second DC voltage. The first DC voltage may vary according to the power generation level of the photovoltaic power generation panel 120 or according to the maximum power point tracking of the MLPE 140. The second DC voltage may be the rated voltage of the power grid 130 or a voltage suitable for the load. Here, the load may be a battery, and the second DC voltage may be the rated voltage of the battery.

[0039] The inverter unit 117 may convert the second DC voltage into a first AC voltage. The inverter unit 117 may convert the second DC voltage after voltage level conversion by the DC-DC converter unit into a first AC voltage according to the voltage form of the grid 130 so that it can be output to the grid 130. Since the grid 130 uses AC voltage, the DC voltage must be changed into AC voltage and output.

[0040] When the battery is connected between the DC-DC converter unit 116 and the inverter unit 117, not only is there a path for directly outputting the voltage generated in the DC-DC converter unit 116 to the grid 130 through the inverter unit 117, but the battery can also be charged with the voltage generated in the DC-DC converter unit 116, and when necessary, the voltage of the battery can be converted by the inverter unit 117 and output to the grid 130. Thus, efficient power supply can be achieved.

[0041] The output unit 113 may output the voltage converted by the power conversion unit 112 to the grid 130 or the load. The output unit 113 includes a switch unit and is connected to any one of the grid 130 or the load to output the voltage converted by the power conversion unit 112.

[0042] The voltage discharge unit 114 is connected to the input unit 111 and discharges the input voltage. When a normal range of the input voltage is input to the input unit 111, the voltage discharge unit 114 does not work, and when an abnormal range of the input voltage is input to the input unit 111, the voltage discharge unit 114 works to quickly discharge the input voltage. The voltage discharge unit 114 monitors the input voltage input to the input unit 111, and can discharge the input voltage when the input voltage range is abnormal.

[0043] When a fire or other abnormality occurs in the photovoltaic power generation panel 120, the voltage level of the input voltage decreases, and therefore, when an input voltage of an abnormal range is input, the voltage discharge unit 114 operates to quickly discharge the voltage of the photovoltaic power generation panel 120. When a fire occurs, workers such as firefighters can approach the photovoltaic power generation panel, but there may be a risk of electric shock due to the high residual voltage. The voltage discharge unit 114 can quickly reduce the residual voltage of the photovoltaic power generation panel 120 to eliminate the risk of electric shock.

[0044] The voltage discharge unit 114 may include: a switch unit 1141, which is turned on when the input voltage is lower than the first voltage; and a resistor 1142, which discharges the input voltage to a second voltage or lower voltage according to the operation of the switch unit. When the input voltage is within a normal range (i.e., higher than the first voltage), the voltage discharge unit 114 does not operate, and when the input voltage becomes lower than the first voltage, the switch unit 1141 is turned on, the resistor 1142 is connected to the input unit 111, and the input voltage of the input unit 111 is quickly discharged to the second voltage or lower voltage through the resistor 1142, thereby reducing the voltage of the photovoltaic power generation panel 120 connected to the input unit 111 to a safe range. When the input voltage becomes lower than the second voltage, the operation of the voltage discharge unit 114 can be turned off, and the input voltage can be monitored.

[0045] For example, the first voltage may be 35V, and the second voltage may be 30V. When the photovoltaic power generation panel 120 operates normally, the input voltage may be 80V, and when the input voltage drops from 80V to 35V or less due to a fire or the like, the switch unit 1141 is turned on so that the resistance element 1142 is connected to the input unit 111, and the voltage of the input unit 111 can be quickly reduced to 30V or less. At this time, the voltage of the input unit 111 can be reduced to 30V or less within 10 seconds or 30 seconds. The switch unit 1141 may include one or more FETs or MOSFETs, and may include various switching elements such as BJTs. The resistance element 1142 may include one or more resistors. According to the discharge speed of the resistance element 1142, it is determined whether it can be discharged below the second voltage within the first time, and the resistance value of the resistance element 1142 may vary according to the required safety specifications.

[0046] The voltage discharge unit 114 may include an RSD execution unit 118 that performs a rapid shutdown (RSD) on the input voltage. Rapid shutdown (RSD) is a safety function that can quickly reduce the voltage when an abnormality occurs. During normal operation, the RSD operates in a standby or sleep mode, and when an abnormality occurs, it operates in an operation or wake-up mode to quickly reduce the voltage.

[0047] The control unit 115 may operate the voltage discharge unit 114 according to the state of the input voltage. The control unit 115 may be a microcontroller unit (MCU) of the power conversion device 110. The control unit 115 may monitor the input voltage input to the input unit 111, and control the power conversion unit to convert the input voltage into a voltage suitable for the grid 130 or the load. Here, the power conversion unit 112 may include at least one switching element, and the control unit 115 may control the on / off duty ratio of the switching element to convert the input voltage. The control unit 115 may control Figure 4 The DC-DC converter unit 116 and the inverter unit 117. When an input voltage within a normal range is input, the DC-DC converter unit 116 and the inverter unit 117 may be controlled to convert the first DC voltage into the second DC voltage and convert the second DC voltage into the first AC voltage.

[0048] The control unit 115 monitors the input voltage, and if the input voltage is lower than the first voltage, shuts down the operation of the power conversion unit 112 and operates the voltage discharge unit 114. If an input voltage of an abnormal range lower than the first voltage is input, the control unit 115 shuts down the operation of the power conversion unit 112 to protect the power conversion device 110 and the grid 130, and operates the voltage discharge unit 114 to protect the photovoltaic power generation panel 120 or the MLPE 140. The control unit 115 turns on the switch unit 1141 of the voltage discharge unit 114 to connect the input unit 111 and the resistance element 1142 to discharge the input voltage.

[0049] When the input voltage becomes higher than the first voltage again, the control unit 115 may turn off the operation of the voltage discharge unit 114 and monitor the input voltage. At this time, the control unit 115 may operate the power conversion unit 112.

[0050] Since the control unit 115 and the voltage discharge unit 114 are built into a single power conversion device 110, monitoring information about the input voltage being input to the input unit 111 can be directly shared, and voltage discharge can be performed even if communication with the outside is cut off, thereby ensuring stability. In addition, the inverter itself monitors and performs RSD operation without adding a module configured with a separate accessory for RSD operation or intercommunication with MLPE, so that it can be interlocked with the PV array and MLPE, making it easy to perform system compatibility and PVRSS certification, and since the RSD function is performed in the inverter, there is no need to perform functional safety separately in the MLPE, and accordingly, the time, manpower and cost required to perform functional safety can be reduced. In addition, since RSD operation does not require separate communication, component CI effect occurs, and system compatibility is good not only with PV arrays without PLC communication but also with MLPEs without applying Sunspec, and can respond to system compatibility certification.

[0051] exist Figure 3In a comparative example, in which an RSD module that discharges the voltage is formed in the MLPE instead of the inverter, the inverter 12 receives the voltage from the MLPE 11 and monitors the RSD condition 14 by monitoring the input voltage. Since the RSD module 13 is formed in the MLPE 11 instead of the inverter 12, an additional accessory installation is required for each MLPE 11. In addition, when an RSD condition occurs, in order to send the RSD condition to the RSD module 13, the RSD condition must be sent through PLC communication using the input power line of the inverter 12; in this case, there may be problems such as susceptibility to PLC noise, and if a separate communication is used, high costs may be incurred. In addition, since the MLPE 11 and the inverter 12 are interconnected to perform the RSD operation, there may be limitations in compatibility with other products, and UL certification may be required through a PVRSS compatibility test that verifies compatibility. In addition, when RSD is performed in the MLPE, there may be problems with development cycle, manpower, and cost due to functional safety performance.

[0052] However, the power conversion device 110 according to the embodiment of the present invention performs RSD condition monitoring and RSD operation within a single device, so that it can quickly process RSD condition response without communication noise or installation of additional accessories.

[0053] The voltage discharge unit 114 can be used as Figure 6 The circuit shown in the figure is used to implement this. Figure 6 As shown, the voltage discharge unit 114 may include a plurality of resistors, switching elements and capacitors. The input terminal includes a MOSFET Q1 connected to the input terminal via a resistor R7, the source of Q1 is connected to a node connecting R7 and R5, and R12 and R3 may be connected to the node in parallel. R12 and R14 are connected, and the node between R12 and R14 may be connected to the gate of Q1 via a Zener diode U1. R3 is connected between the source and gate of Q1, and a diode D1 may be connected to the drain of Q1. D1 connects the drain of R1 and Q1, and R1 may be connected to the base of D1 and BJT Q5. The collector of Q5 is connected to R8. Capacitor C2 may be connected to the node between D1 and R1. R14, U1, and C2 may be grounded at one end. Diode D3 is connected in parallel with R7 at the input terminal, and D3 may be connected to R8.

[0054] The input terminal can be connected to a MOSFET Q3 connected in parallel with R7. R13 and R2 are connected in parallel to a node between the input terminal and Q3, R13 and R17 are connected, and the node between R13 and R17 can be connected to the gate of Q3 via a Zener diode U3. R2 can be connected between the source and gate of Q3, and a diode D2 can be connected to the drain of Q1. D2 connects the drain of Q3 and R6, and R6 can be connected to D2 and the base of BJT Q2. The collector of Q2 is connected to R10, and R10 can be connected between Q2 and D3. Capacitor C3 can be connected to a node between D2 and R6. One end of R17, U3, and C3 can be grounded. The emitter of Q2 can be connected to the collector of Q6, and the collector of Q5 can be connected to the base of Q6. R4 and capacitor C1 can be connected in parallel at a node between Q2 and Q6. According to the input voltage, Q1 to Q6 can be turned on, and the input voltage of the input unit can be quickly discharged through R1 to R17 and C1 to C3.

[0055] The control unit 115 may turn on Q1 or Q3 by applying a gate voltage to the gate. The control unit 115 monitors the input voltage, and when the input voltage falls within an abnormal voltage range, turns on Q1 or Q3 to quickly discharge the input voltage.

[0056] As described above, by operating the voltage discharge unit 114 built into the power conversion device 110 , it is possible to quickly reduce the voltage when an abnormality occurs. Figure 7 The output voltage of the MLPE 140 and the output voltage of the DC-DC converter unit 116 according to an embodiment of the present invention are shown. When the output voltage of the MLPE 140, which is the input voltage of the power conversion device 110, is equal to or higher than the first voltage 35V, it can be confirmed that the device operates normally, and when the output voltage of the MLPE 140 becomes lower than 35V, the voltage decreases to 0V due to the discharge of the voltage discharge unit 114. Thereafter, when the output voltage of the MLPE 140 becomes higher than 35V again, it can be confirmed that the device operates normally.

[0057] Figure 8 is a block diagram of a photovoltaic power generation system 200 according to an embodiment of the present invention. Figure 8 A detailed description of each component of the photovoltaic power generation system 200 corresponds to Figures 1 to 7 A detailed description of the power conversion device is given below, and therefore, any repeated description will be omitted below.

[0058] The photovoltaic power generation system 200 according to an embodiment of the present invention includes: at least one photovoltaic power generation panel 120; and a power conversion module 110, which converts the voltage generated by the photovoltaic power generation panel 120 and outputs the voltage to the power grid 130 or the load. The power conversion module 110 may include: an input unit 111, which receives the voltage generated by the photovoltaic power generation panel 120; a power conversion unit 112, which converts the input voltage input to the input unit 111; an output unit 113, which outputs the converted voltage to the power grid 130 or the load; and a voltage discharge unit 114, which is connected to the input unit 111 and discharges the input voltage.

[0059] The photovoltaic power generation panel 120 may include a MLPE 140 that optimizes a voltage, the input unit 111 may be connected to the MLPE 140 to receive an input voltage, and the power conversion module 110 may include a control unit 115 that operates a voltage discharge unit 114 according to a state of the input voltage.

[0060] The control unit 115 monitors the input voltage, and if the input voltage is lower than the first voltage, shuts down the operation of the power conversion unit 112 and operates the voltage discharge unit 114 .

[0061] The features, structures, effects, etc. described in the above embodiments are included in at least one embodiment and are not necessarily limited to one embodiment. In addition, the features, structures, effects, etc. exemplified in each embodiment can be combined or modified by a person of ordinary skill in the art to which the embodiment belongs and implemented in other embodiments. Therefore, the contents related to such combinations and modifications should be interpreted as being included in the scope of the embodiments.

[0062] Those skilled in the art associated with the present embodiment will appreciate that the above description can be implemented in a modified form without departing from its essential characteristics. Therefore, the disclosed method should be considered from an illustrative rather than a restrictive perspective. The scope of the present invention is represented by the claims, rather than by the above description, and all differences within the scope equivalent thereto should be interpreted as included in the present invention.

Claims

1. A power conversion device, comprising: an input unit receiving a voltage generated from the photovoltaic power generation panel; a power conversion unit configured to convert an input voltage input to the input unit; an output unit that outputs the converted voltage to a system or a load; and A voltage discharge unit is connected to the input unit and is configured to discharge the input voltage.

2. The power conversion device according to claim 1, in, The input unit is connected to a module-level power electronic device MLPE to receive the input voltage, and the MLPE optimizes the voltage of the photovoltaic power generation panel.

3. The power conversion device according to claim 1, in, The input voltage is a first DC voltage, and Wherein, the power conversion unit comprises: A DC-DC converter unit configured to convert the first DC voltage into a second DC voltage; and The inverter unit is configured to convert the second DC voltage into a first AC voltage.

4. The power conversion device according to claim 1, comprising: A control unit is configured to operate the voltage discharge unit according to a state of the input voltage.

5. The power conversion device according to claim 4, in, The control unit monitors the input voltage, and when the input voltage is lower than a first voltage, shuts down the operation of the power conversion unit and operates the voltage discharge unit.

6. The power conversion device according to claim 1, in, The voltage discharge unit comprises: a switch unit configured to be turned on when the input voltage is lower than a first voltage; and The resistor element discharges the input voltage to below a second voltage according to the operation of the switch unit.

7. The power conversion device according to claim 1, in, The voltage discharge unit includes a rapid shutdown RSD execution unit, and the RSD execution unit performs rapid shutdown on the input voltage.

8. A photovoltaic power generation system, comprising: at least one photovoltaic panel; as well as a power conversion module configured to convert the voltage generated by the photovoltaic power generation panel and output the voltage to a system or a load, Wherein, the power conversion module comprises: an input unit, receiving a voltage generated by the photovoltaic power generation panel; a power conversion unit configured to convert an input voltage input to the input unit; an output unit that outputs the converted voltage to a system or a load; and A voltage discharge unit is connected to the input unit and is configured to discharge the input voltage.

9. The photovoltaic power generation system according to claim 8, comprising: The module-level power electronic device MLPE is configured to optimize the voltage of the photovoltaic panel, The input unit is connected to the MLPE to receive the input voltage.

10. The photovoltaic power generation system according to claim 9, in, The power conversion module includes a control unit that operates the voltage discharge unit according to a state of the input voltage.

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