Power conversion device

Abstract

A power conversion device according to an embodiment of the present invention comprises: an input unit that receives, as an input, power from a PV module; a power conversion unit that converts the power received as the input from the PV module; and an output unit connected to a battery so as to output power to the battery, wherein the power conversion unit comprises a plurality of switches connected in parallel and operating in an interleaved manner, and the output unit is connected in parallel to another power conversion device.

Description

power conversion device

[0001] The present invention relates to a power conversion device, and more specifically, to a power conversion device that stably converts power from a solar power generation module and outputs it to a battery.

[0002] Solar power generation is becoming widely adopted as an eco-friendly energy source, replacing conventional chemical and nuclear power generation. Solar power generation can be either standalone, with a battery connected to a converter, or grid-connected. Standalone systems typically consist of photovoltaic panels, storage batteries, and power conversion equipment, while grid-connected systems are connected to commercial power sources, enabling the exchange of power with load grid lines.

[0003] Photovoltaic modules have different maximum power points depending on factors such as irradiance and temperature. To operate solar cells at their maximum power point, an optimizer or module-level power electronics (MLPE) can be used to perform maximum power point tracking (MPPT) control on a module-by-module basis.

[0004] When the output of a photovoltaic module is stored in a battery module, if ripple occurs depending on the operation of the optimizer of the photovoltaic module, the battery is affected, so a technology for reducing ripple on the battery module is required.

[0005] The technical problem to be solved by the present invention is to provide a power conversion device that stably converts power from a solar power generation module and outputs it to a battery.

[0006] In order to solve the above technical problem, a power conversion device according to one embodiment of the present invention includes an input unit that receives power from a PV module; a power conversion unit that converts the power received from the PV module; and an output unit that is connected to a battery and outputs power to the battery, wherein the power conversion unit includes a plurality of switches that are connected in parallel and operate in an interleaved manner, and the output unit is connected in parallel with another power conversion device.

[0007] In addition, the power conversion unit may include an input capacitor connected in parallel with the input unit; an output capacitor connected in parallel with the output unit; and a first power conversion unit and a second power conversion unit connected in parallel between the input capacitor and the output capacitor.

[0008] In addition, the first power conversion unit may include a first inductor and a first diode connected in series with the input unit; and a first switch connected in parallel between the first inductor and the first diode, and the second power conversion unit may include a second inductor and a second diode connected in series with the input unit; and a second switch connected in parallel between the second inductor and the second diode.

[0009] Additionally, the first switch and the second switch can be complementarily connected to each other.

[0010] In addition, when the power conversion unit converts power, one of the first switch and the second switch may have a time when the other switch is turned on while the other switch is turned off.

[0011] In addition, it may include a first input current sensing unit that is connected in series with the first inductor and measures an input current applied to the first inductor; a second input current sensing unit that is connected in series with the second inductor and measures an input current applied to the second inductor; an output voltage sensing unit that measures an output voltage of power output to the output unit; and an output current sensing unit that measures an output current of power output to the output unit.

[0012] Additionally, the plurality of switches can be PWM controlled.

[0013] Additionally, it may include a switching unit that is connected in series with the output unit and blocks power output to the output unit.

[0014] Additionally, the output unit may include a power line communication unit that communicates with a battery management device that manages the battery through a power line.

[0015] Additionally, the power conversion unit can operate in a boost mode that boosts the voltage received from the PV module.

[0016] According to embodiments of the present invention, the current ripple delivered to the battery can be minimized by configuring the connection between optimizers of the PV modules in parallel.

[0017] FIG. 1 is a block diagram of a power conversion device according to one embodiment of the present invention.

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

[0019] Figures 3 and 4 illustrate implementation examples of a power conversion device according to an embodiment of the present invention.

[0020] FIG. 5 is a drawing for explaining the connection relationship between a power conversion device according to an embodiment of the present invention and another power conversion device.

[0021] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0022] However, the technical idea of ​​the present invention is not limited to some of the embodiments described, but can be implemented in various different forms, and within the scope of the technical idea of ​​the present invention, one or more of the components between the embodiments can be selectively combined or substituted for use.

[0023] In addition, terms (including technical and scientific terms) used in the embodiments of the present invention may be interpreted as having a meaning that can be generally understood by a person of ordinary skill in the technical field to which the present invention belongs, unless explicitly and specifically defined and described, and terms that are commonly used, such as terms defined in a dictionary, may be interpreted in consideration of the contextual meaning of the relevant technology.

[0024] Additionally, the terms used in the embodiments of the present invention are intended to describe the embodiments and are not intended to limit the present invention.

[0025] In this specification, the singular may also include the plural unless specifically stated otherwise in the phrase, and when it is described as “A and / or at least one (or more) of B, C”, it may include one or more of all combinations that can be combined with A, B, C.

[0026] Additionally, in describing components of embodiments of the present invention, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only intended to distinguish the components from other components, and are not intended to limit the nature, order, or sequence of the components.

[0027] And, when a component is described as being 'connected', 'coupled', or 'connected' to another component, it may include not only cases where the component is 'connected', 'coupled', or 'connected' directly to the other component, but also cases where the component is 'connected', 'coupled', or 'connected' by another component between the component and the other component.

[0028] Additionally, when described as being formed or arranged "above" or "below" each component, "above" or "below" includes not only cases where the two components are in direct contact with each other, but also cases where one or more other components are formed or arranged between the two components. Furthermore, when expressed as "above" or "below," the meaning may include not only the upward direction but also the downward direction based on one component.

[0029] Fig. 1 is a block diagram of a power conversion device according to an embodiment of the present invention. Fig. 2 is a block diagram of a power conversion device according to an embodiment of the present invention. Figs. 3 and 4 illustrate implementation examples of a power conversion device according to an embodiment of the present invention. Fig. 5 is a diagram for explaining a connection relationship between a power conversion device according to an embodiment of the present invention and other power conversion devices.

[0030] A power conversion device (100) according to an embodiment of the present invention is composed of an input unit (110), a power conversion unit (120), and an output unit (130), and may include a first power conversion unit, a second power conversion unit, an input voltage sensing unit (111), a first input current sensing unit (141), a second input current sensing unit (142), an output current sensing unit (131), an output voltage sensing unit (132), a switching unit (133), a power line communication unit (134), etc.

[0031] A power conversion device (100) according to an embodiment of the present invention is a power conversion device that converts power output from a PV module (211) and outputs it to a battery (220), and may be an optimizer of the PV module (211). A solar power generation system can be configured together with a PV module (211), a battery (220), and an inverter (not shown).

[0032] The input unit (101) is connected to the PV module (211) and receives power from the PV module (211).

[0033] The PV module (211) generates electricity through solar power generation using sunlight. The PV module (211) may include a PV panel.

[0034] A PV panel may include multiple cell strings. A solar cell that generates solar power can be expressed as a cell string unit, which is a series-connected cell string. A cell string may include at least one cell, and when it includes multiple cells, the cells may be series-connected. A cell string may be a solar cell string that includes solar cells. A solar cell string may form a PV panel. A PV panel may also be referred to as a solar panel or solar power generation panel. Solar cells generate solar power (PV) by utilizing the photovoltaic effect. The photovoltaic effect is the emission of electrons when light above a certain frequency strikes a specific metal material. A pn ​​junction is formed using a p-type semiconductor and an n-type semiconductor, and the electrons generated by the photovoltaic effect generate current, thereby generating power. Solar cells are formed using silicon or other materials and may be formed in a wafer form. Solar cells are located in fields, exterior walls of buildings, or rooftops where they can receive plenty of sunlight, and generate power using sunlight. At this time, the solar cells can be formed into BIPV (building-integrated photovoltaics) that are formed as an integral part of the building.

[0035] The power conversion unit (120) can convert power input from the PV module (211). The power conversion unit (120) can convert power input from the PV module (211) into power having a voltage required to charge the battery (220). The power conversion unit (120) can be an optimizer of the PV module (211), and as an optimizer, can perform maximum power point tracking (MPPT) so that the power output from the PV module (211) becomes maximum power.

[0036] Since the amount of power generated from a single solar cell is insufficient to be utilized by a load or power system, power suitable for utilization can be generated by connecting multiple solar cells in series to form a solar cell string instead of a single solar cell. A solar cell string can be a basic unit for generating power. A photovoltaic panel can be formed by forming multiple cell strings, which are basic units, into a panel. Solar cells have different voltage-current characteristics depending on the amount of sunlight, temperature, etc., and the maximum power point (MPP) also changes. (Generated power = Voltage X Current)

[0037] An optimizer optimizes the output power of a string of cells so that the solar cells operate at the maximum power point (MPP), which is the operating point where the solar cells produce the most power under each condition. The optimizer may include module-level power electronics (MLPE). This is called maximum power point tracking (MPPT), and MPPT can be used to improve the efficiency of solar power generation. In solar power generation, depending on the characteristics of the relationship between current and voltage and the relationship between voltage and power, the maximum power may not be the maximum voltage, but rather the power when the voltage is approximately 80% of the maximum voltage. Since this maximum power point continuously changes depending on the magnitude of the voltage and current generated by the PV panel, the point where the maximum power point can occur must be continuously searched. In other words, in order to track the maximum power, not the maximum voltage, the magnitude of the voltage and current can be varied to achieve the maximum power. That is, the voltage can be reduced and the current increased in the direction of increasing power, or the voltage can be increased and the current can be reduced.

[0038] In addition to tracking the maximum power point for the PV module, the power conversion unit (120) can convert the power received from the PV module (211) into power having a voltage required to charge the battery (220). The battery module does not include a separate DC-DC converter, and the power converted by the power conversion unit (120) can be directly applied through the output unit (130). The power conversion unit (120) may be a boost converter that increases the voltage.

[0039] The output unit (130) is connected to the battery (220) and outputs power to the battery (220). The battery (220) can receive power and be charged. The battery (220) may include a battery management system (BMS) that manages the battery status.

[0040] It may include a control unit (not shown) for controlling the power conversion unit (120). Or, it may control by receiving a command from an external controller. The control unit may measure input current, output voltage, output current, etc., and receive data including status information from the PV module (211), battery (220), inverter, external controller, load, etc., and control each component so that power input from the PV module (211) can be output to the battery (220). The control unit may include one or more processors and may further include a memory, and it is obvious that the functions of the control unit or the functions of other components may be implemented in software or hardware.

[0041] The output unit (130) may be connected in parallel with another power conversion device (232). The other power conversion device (232) may receive power from the corresponding PV module (212), convert it, and be connected to the battery (220). Here, the other power conversion device (232) may be an optimizer of the PV module (212). That is, the PV module and the optimizer, which is a power conversion device, may be connected in parallel to supply power to the battery (220). When a plurality of power conversion devices are connected in parallel to each other to convert power input from the PV module and output it to the battery (220), the power conversion devices connected in parallel may operate individually or simultaneously. Each power conversion device connected in parallel includes a switching operation during power conversion, and at this time, current ripple may occur, and since each power conversion device is directly connected to the battery (220), the ripple may have a great impact on the lifespan of the battery (220).

[0042] In converting the power input from the PV module (211) and outputting it to the battery (220), the power conversion device (100) according to the embodiment of the present invention may include a plurality of switches that are connected in parallel and operate in an interleaved manner. The power conversion unit (120) may be configured as an interleaved circuit to minimize ripple within the power conversion device. As shown in Fig. 2, the power conversion unit (120) configures two paths that are connected in parallel, and includes a first switch (121) and a second switch (122) that are connected in parallel to each path, and the first switch (121) and the second switch (122) operate in an interleaved manner, thereby reducing the change in the current output from the output unit (130), thereby reducing the current ripple. The power conversion unit (120) may be an interleaved boost converter that boosts the voltage in an interleaved manner.

[0043] The power conversion unit (120) may include an input capacitor (123), an output capacitor (124), a first power conversion unit, and a second power conversion unit.

[0044] The input capacitor (123) may be connected in parallel with the input unit (110). The input capacitor (123) may be a smoothing capacitor that stabilizes the voltage of the power input from the PV module (211).

[0045] The output capacitor (124) may be connected in parallel with the output unit (130). The output capacitor (124) may be a smoothing capacitor that stabilizes the voltage output from the power conversion unit (120).

[0046] It may include a first power conversion unit and a second power conversion unit connected in parallel between an input capacitor (123) and an output capacitor (124).

[0047] The first power conversion unit and the second power conversion unit can operate in an interleaved manner to minimize current ripple.

[0048] The first power conversion unit may include a first inductor (125), a first diode (126), and a first switch (121). The first inductor (125) and the first diode (126) may be connected in series between the input unit (110) and the output unit (130). The first inductor (125) may be connected in parallel with the input capacitor (123), and a first diode (126) may be connected in series to a rear end of the first inductor (125). The rear end of the first diode (126) may be connected in parallel with an output capacitor (124).

[0049] The first switch (121) may be connected in parallel between the first inductor (125) and the first diode (126). One end of the first switch may be connected to the node between the first inductor (125) and the first diode (126), and the other end may be connected to ground.

[0050] The first power conversion unit can convert power by including a first inductor (125), a first diode (126), a first switch (121), and an output capacitor (124). When the first switch (121) is turned on, a path for current to flow through the first inductor (125) and the first switch (121) is formed, so that the current flowing through the first inductor (125) increases, and when the first switch (121) is turned off, the current flowing through the first inductor (125) is output to the output side via the first diode (126), thereby allowing a voltage higher than the input voltage to be output. The current flowing through the first inductor (125) can charge the output capacitor (124). Afterwards, when the first switch (121) is turned on again, the voltage charged in the output capacitor (124) is blocked from being applied in the reverse direction by the first diode (126) and is output to the output side, so that it can operate as a boost converter. The first diode (126) can form a current path during boost operation and can be replaced with a MOSFET including the diode. The first switch (121) can perform a PWM operation following maximum power point tracking control for the PV module (211). That is, the first switch (121) can perform an on / off operation so that the power output from the PV module (211) is maximized.

[0051] The second power conversion unit may include a second inductor (127), a second diode (128), and a second switch (122). The second inductor (127) and the second diode (128) may be connected in series between the input unit (110) and the output unit (130). The second inductor (127) may be connected in parallel with the input capacitor (123), and a second diode (128) may be connected in series to a rear end of the second inductor (127). The rear end of the second diode (128) may be connected in parallel with the output capacitor (124).

[0052] The second switch (122) may be connected in parallel between the second inductor (127) and the second diode (128). One end of the second switch may be connected to the node between the second inductor (127) and the second diode (128), and the other end may be connected to ground.

[0053] The second power conversion unit can convert power by including a second inductor (127), a second diode (128), a second switch (122), and an output capacitor (124). When the second switch (122) is turned on, a path for current to flow through the second inductor (127) and the second switch (122) is formed, so that the current flowing through the second inductor (127) increases, and when the second switch (122) is turned off, the current flowing through the second inductor (127) is output to the output side via the second diode (128), thereby allowing a voltage higher than the input voltage to be output. The current flowing through the second inductor (127) can charge the output capacitor (124). Afterwards, when the second switch (122) is turned on again, the voltage charged in the output capacitor (124) is blocked from being applied in the reverse direction by the second diode (128) and is output to the output side, so that it can operate as a boost converter. The second diode (128) can form a current path during boost operation and can be replaced with a MOSFET including the diode. The second switch (122) can perform a PWM operation according to maximum power point tracking control for the PV module (211). That is, the second switch (122) can perform an on / off operation so that the power output from the PV module (211) is maximized.

[0054] The first power conversion unit and the second power conversion unit can be connected in parallel. That is, the first power conversion unit including the first inductor (125), the first diode (126), and the first switch (121) and the second power conversion unit including the second inductor (127), the second diode (128), and the second switch (122) can be connected in parallel.

[0055] As described above, the first switch (121) or the second switch (122) performs an on-off operation when performing a boost operation, and when the switch is turned off from an on state, the change in the current output to the output side increases, which may cause ripple.

[0056] In order to minimize ripple, the first power conversion unit and the second power conversion unit are connected in parallel, and the first switch (121) and the second switch (122) can be complementarily conducted with each other. When the power conversion unit (120) converts power, the time may include a time when one of the first switch (121) and the second switch (122) is turned on and the other switch is turned off. Since the first switch (121) and the second switch (122) are complementarily conducted, the first power conversion unit and the second power conversion unit can operate in an interleaved manner, and through this, the time when the current output to the power conversion unit (120) is cut off can be minimized, thereby reducing the change in the current and minimizing the current ripple.

[0057] In order to monitor the input and output of power, an input voltage sensing unit (111), a first input current sensing unit (141), a second input current sensing unit (142), an output voltage sensing unit (132), and an output current sensing unit (131) may be included.

[0058] The input voltage sensing unit (111) is connected to the input unit (110) and can measure the voltage input from the PV module (211). As shown in FIGS. 3 and 4, in the implemented embodiment, the input voltage sensing unit (111) can be configured as a voltage sensor.

[0059] The input current can flow through two paths formed by the first power conversion unit and the second power conversion unit, and may include a first input current sensing unit (141) and a second input current sensing unit (142). The first input current sensing unit (141) is connected in series with the first inductor (125) to measure the input current applied to the first inductor (125), and the second input current sensing unit (142) is connected in series with the second inductor (127) to measure the input current applied to the second inductor (127). As shown in FIGS. 3 and 4 , in an implemented embodiment, the first input current sensing unit (141) and the second input current sensing unit (142) may be configured as current sensors.

[0060] The output voltage sensing unit (132) measures the output voltage of the power converted in the power conversion unit (120) and output to the output unit (130), and the output current sensing unit (131) can measure the output current of the power converted in the power conversion unit (120) and output to the output unit (130). As shown in FIGS. 3 and 4, in the implemented embodiment, the output voltage sensing unit (132) may be configured as a voltage sensor, and the output current sensing unit (131) may be configured as a current sensor.

[0061] The output section (130) side may include a switching section (133) or a communication section.

[0062] The switching unit (133) is connected in series with the output unit (130) and can block power from being output from the output unit (130).

[0063] When detecting that an abnormality has occurred in the PV module (211) or the like from the values ​​measured by the input voltage sensing unit (111), the first input current sensing unit (141), or the second input current sensing unit (142), the control unit can turn off the switching unit (133) to block the power output. Alternatively, an abnormality in the PV module (211) can be detected using an abnormality detection unit such as an arc sensor. At this time, an arc or the like can be detected. Here, an arc is a gas insulation breakdown phenomenon that generates current through a non-conductive medium such as air, and when an arc occurs, a lot of heat is generated, which poses a risk of fire or the like. The occurrence of an arc or the like can be detected by including an arc sensor or the like.

[0064] The switching unit (133) can perform an RSD (Rapid Shut Down) function by quickly shutting off the output when an abnormality occurs. The switching unit (133) can include a power relay.

[0065] The communication unit can perform communication with the battery management device that manages the battery (220) or the outside. The communication unit can include a power line communication unit (134) that performs communication through the power line of the output unit (130). The power line communication unit (134) can perform PLC (Power Line Communication) that performs communication using the power line. Alternatively, communication can be performed through other wired or wireless communication. The communication unit can perform communication with the battery management device through wired or wireless communication such as CAN communication or RS-485. The communication unit can perform monitoring by transmitting input / output voltage and current, power, and status information to the outside, and can receive commands such as on / off and output amount control and transmit them to the control unit to control the switch or switching unit (133) of the power conversion unit (120).

[0066] The power conversion device (100) according to an embodiment of the present invention, as shown in FIG. 5, is connected to a PV module (211), performs maximum power point tracking control for the PV module (211), and converts power input from the PV module (211) and outputs it to a battery (220). Other power conversion devices (232, 233), which are respectively connected to other PV modules (212, 213), may be connected in parallel to the battery (220). In order to minimize the influence of current ripple due to the switching operation of the power conversion devices on the lifespan of the battery (220) by connecting multiple power conversion devices in parallel, the power conversion unit (120) may include an interleaved circuit. Through this, the current ripple transmitted to the battery can be minimized by configuring the connection between optimizers of the PV modules in parallel.

[0067] Those skilled in the art will appreciate that the present invention can be implemented in modified forms without departing from the essential characteristics of the above-described description. Therefore, the disclosed methods should be considered illustrative rather than restrictive. The scope of the present invention is set forth in the claims, not the foregoing description, and all differences within the scope equivalent thereto should be construed as being encompassed by the present invention.

Claims

1. Input section that receives power from the PV module; A power conversion unit that converts power received from the PV module; and Includes an output unit that is connected to a battery and outputs power to the battery, The above power conversion unit, Comprising a plurality of switches connected in parallel and operating in an interleaved manner, The above output unit is a power conversion device connected in parallel with another power conversion device.

2. In paragraph 1, The above power conversion unit, An input capacitor connected in parallel with the above input section; an output capacitor connected in parallel with the above output section; and A power conversion device including a first power conversion unit and a second power conversion unit connected in parallel between the input capacitor and the output capacitor.

3. In paragraph 2, The above first power conversion unit, A first inductor and a first diode connected in series with the input section; and A first switch is included, which is connected in parallel between the first inductor and the first diode, The above second power conversion unit, a second inductor and a second diode connected in series with the input section; and A power conversion device comprising a second switch connected in parallel between the second inductor and the second diode.

4. In paragraph 3, A power conversion device in which the first switch and the second switch are complementarily connected to each other.

5. In paragraph 3, When the above power conversion unit converts power, A power conversion device having a time when one of the first switch and the second switch is turned on and the other switch is turned off.

6. In paragraph 3, A first input current sensing unit connected in series with the first inductor and measuring an input current applied to the first inductor; A second input current sensing unit connected in series with the second inductor and measuring an input current applied to the second inductor; An output voltage sensing unit for measuring the output voltage of the power output to the above output unit; and A power conversion device including an output current sensing unit that measures the output current of power output to the above output unit.

7. In paragraph 1, The above plurality of switches are PWM controlled power conversion devices.

8. In paragraph 1, A power conversion device including a switching unit connected in series with the output unit to block power output to the output unit.

9. In paragraph 1, A power conversion device including a power line communication unit that performs communication with a battery management device that manages the battery through a power line of the output unit.

10. In paragraph 1, The above power conversion unit, A power conversion device that operates in boost mode to boost the voltage received from the PV module.

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