Power conversion device

Abstract

A power conversion device according to an embodiment of the present invention comprises: an input unit connected to a PV module; a voltage distribution unit for distributing a voltage between both ends of the input unit; an offset voltage unit for adding an offset voltage to the voltage input from the voltage distribution unit; and a control unit for using the output of the offset voltage unit to determine whether the input unit and the PV module are reversely connected.

Description

power conversion device

[0001] The present invention relates to a power conversion device, and more specifically, to a reverse connection detection circuit that detects reverse connection and a power conversion device including the same.

[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 control maximum power point tracking (MPPT) at the module level and convert and output power.

[0004] Solar power conversion devices receive DC voltage generated by solar panels as input and convert it into the desired form of power. DC voltage has positive and negative polarities, and reversing the polarity can damage the product. Technology is needed to prevent this reverse wiring.

[0005] The technical problem to be solved by the present invention is to provide a reverse wiring detection circuit that detects reverse wiring and a power conversion device including the same.

[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 connected to a PV module; a voltage distribution unit that distributes voltage across both ends of the input unit; an offset voltage unit that adds an offset voltage to the voltage input from the voltage distribution unit; and a control unit that determines whether the input unit and the PV module are reversely connected using an output of the offset voltage unit.

[0007] In addition, the control unit can determine that the connection between the input unit and the PV module is reversed when the output of the offset voltage unit is lower than or equal to the offset voltage.

[0008] In addition, the voltage distribution unit connects both ends of the input unit and includes a first resistor, a second resistor, and a third resistor connected in series, and can output a first voltage of the first resistor and the second resistor.

[0009] Additionally, the offset voltage unit may include a differential amplifier that adds the offset voltage of the first voltage source to the first voltage output from the voltage distribution unit.

[0010] In addition, the offset voltage section includes a fourth resistor connected to a first node between the first resistor and the second resistor; a fifth resistor connected to a second node between the second resistor and the third resistor; a differential amplifier in which the fourth resistor is connected to a (-) input terminal and the fifth resistor is connected to a (+) input terminal; a sixth resistor and a first voltage power supply connected to a (+) input terminal of the differential amplifier; and a seventh resistor connecting an output terminal of the differential amplifier and the (-) input terminal, wherein the first voltage power supply can input the offset voltage to the differential amplifier.

[0011] Additionally, it may include an insulating section that insulates between the offset voltage section and the control section.

[0012] Additionally, the insulating portion may include an insulating amplifier.

[0013] In addition, the control unit can stop the operation of the power conversion device when it determines that the connection between the input unit and the PV module is reversed.

[0014] In addition, the control unit can provide a reverse connection notification to the upper controller when it determines that the connection between the input unit and the PV module is reversed.

[0015] Additionally, it may include an insulating section that insulates between the offset voltage section and the control section.

[0016] In order to solve the above technical problem, a reverse connection detection circuit according to an embodiment of the present invention includes a plurality of resistors that connect both ends of an input section and are connected in series; and an offset voltage section that receives a first voltage of at least one resistor among the plurality of resistors and adds an offset voltage, and applies an output of the offset voltage section to a control section that determines whether or not a reverse connection has occurred.

[0017] In addition, the plurality of resistors include a first resistor, a second resistor, and a third resistor connected in series, and the offset voltage unit includes: a fourth resistor connected to a first node between the first resistor and the second resistor; a fifth resistor connected to a second node between the second resistor and the third resistor; a differential amplifier in which the fourth resistor is connected to a (-) input terminal and the fifth resistor is connected to a (+) input terminal; a sixth resistor and a first voltage supply connected to a (+) input terminal of the differential amplifier; and a seventh resistor connecting an output terminal of the differential amplifier and the (-) input terminal, wherein the first voltage supply can input the offset voltage to the differential amplifier.

[0018] According to embodiments of the present invention, reverse wiring can be detected using a simple circuit consisting of only an op-amp and a few resistors. This circuit configuration reduces circuit costs and utilizes existing sensing circuits, eliminating additional losses. Since negative voltage sensing is possible with only a slight offset voltage, there is no significant loss in voltage resolution.

[0019] Figure 1 is a block diagram of a power conversion device according to one embodiment of the present invention.

[0020] Figures 2 and 3 are block diagrams of a power conversion device according to an embodiment of the present invention.

[0021] Figures 4 and 5 illustrate circuit diagrams of a power conversion device according to an embodiment of the present invention.

[0022] Figure 6 illustrates the measurement results of a power conversion device according to one embodiment of the present invention.

[0023] Figure 7 is a block diagram of a reverse wiring detection circuit according to one embodiment of the present invention.

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

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] A variation according to the present embodiment may include some components of each embodiment and some components of other embodiments. That is, a variation may include one embodiment among various embodiments, but may omit some components and include some components of the corresponding other embodiment. Or, the opposite may be true. The features, structures, effects, etc. to be described in the embodiments are included in at least one embodiment, and are not necessarily limited to just one embodiment. Furthermore, the features, structures, effects, etc. exemplified in each embodiment can be combined or modified in other embodiments by a person having ordinary skill in the art to which the embodiments belong. Therefore, the contents related to such combinations and modifications should be interpreted as being included within the scope of the embodiments.

[0033] Fig. 1 is a block diagram of a power conversion device according to an embodiment of the present invention. Figs. 2 and 3 are block diagrams of a power conversion device according to an embodiment of the present invention, Figs. 4 and 5 illustrate circuit diagrams of a power conversion device according to an embodiment of the present invention, and Fig. 6 illustrates measurement results of a power conversion device according to an embodiment of the present invention.

[0034] A power conversion device (100) according to an embodiment of the present invention is composed of an input unit (110), a voltage distribution unit (120), an offset voltage unit (130), and a control unit (140), and may include an insulation unit (150), a power conversion unit (not shown), and an output unit (not shown).

[0035] A power conversion device (100) according to an embodiment of the present invention is a power conversion device that receives power from a PV module (200), converts it, and outputs it. The PV module (200) may include an MLPE (Module-Level Power Electronics). Alternatively, it may include an optimizer. The power conversion device (100) according to an embodiment of the present invention may be a DC-DC converter or inverter that receives power from the PV module (200). Alternatively, it may include another power conversion device that receives power, converts it, and outputs it.

[0036] The input unit (110) receives power. The input unit (110) is connected to the PV module (200) and can receive power from the PV module (200).

[0037] A PV module (200) is a photovoltaic module, and may be a module that converts power generated by a photovoltaic panel or a photovoltaic panel into power suitable for a load or battery. It may be expressed as a solar module, solar power generation module, etc. A PV panel includes multiple cell strings. A solar cell that performs solar power generation may be expressed as a cell string unit in which multiple cells are connected in series.

[0038] A cell string may include at least one cell, and when including multiple cells, the multiple cells may be connected in series. The cell string may be a solar cell string including solar cells. The solar cell string may form a photovoltaic (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 are used to 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 that can receive a lot of sunlight, on the exterior walls of buildings, on rooftops, etc., and generate power using sunlight. In this case, the solar cells may be formed as BIPV (Building Integrated Photovoltaics) that are formed integrally with the building.

[0039] 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)

[0040] An optimizer can control the operation of a solar cell at its maximum power point (MPP), which is the operating point where the solar cell produces the maximum power under each condition. 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 can be the power when the voltage is approximately 80% of the maximum voltage, rather than the maximum voltage. Since this maximum power point continuously changes depending on the magnitude of the voltage and current generated by the photovoltaic panel, the point where the maximum power point can occur must be continuously searched. In other words, in order to track the maximum power, rather than the maximum voltage, the magnitude of the voltage and current can be varied to achieve the maximum power. In other words, the voltage can be reduced and the current can be increased in the direction of increasing power, or the voltage can be increased and the current can be reduced.

[0041] The power input to the input unit (110) can be converted and output by the power conversion unit. The power conversion unit can supply power to the grid via an energy storage system (ESS) including a battery or an inverter through the output unit. A DC-Link can be connected to the output unit.

[0042] The power input to the input unit (110) is direct current power, has (+) and (-) polarities, and the input unit (110) must be connected with the PV module (200) with the correct polarity. At this time, if the (+) input terminal and the (-) input terminal of the input unit (110) are connected in reverse polarity, damage to internal components may occur. In order to prevent such reverse connection, the presence of reverse connection must be detected. To this end, the power conversion device (100) according to an embodiment of the present invention may include a configuration capable of detecting reverse connection.

[0043] The input unit (110) may include a connector capable of preventing a connection line, thereby preventing a reverse connection in hardware, or a diode may be connected to the input unit (110) in the forward direction to block the flow of power when connected in the reverse direction, or a sensor that measures bidirectional current may be used to determine a reverse connection when a negative current flows. If a reverse connection is detected, the power may be cut off, an alarm may be transmitted to an external controller, and the operation of the power conversion device may be stopped.

[0044] However, when the PV lead-in line is manufactured by the installer, it is difficult to apply a reverse-connection prevention connector, and when a diode is applied, power corresponding to the product of the diode's forward voltage and current is lost, and when measuring bidirectional current, half of the sensing area is an area that is not normally used, which may result in a loss in sensing resolution.

[0045] In another embodiment of the present invention, a power conversion device (100) uses a reverse connection detection circuit (300) to detect reverse connection by applying a voltage sensing circuit that detects the voltage of an input unit (110).

[0046] The input unit (110) is connected to the PV module (200), and the voltage distribution unit (120) distributes the voltage across the input unit (110). The voltage distribution unit (120) can be connected in parallel with the power conversion unit to the input unit (110). When the voltage of the input unit (110) is directly used for reverse connection detection, since the magnitude of the voltage input to the input unit (110) is large, the capacitance of the elements must also be large. Therefore, by distributing the voltage and using the voltage reduced at a certain ratio, it can be used for reverse connection detection.

[0047] The voltage distribution unit (120) connects both ends of the input unit (110) and may include a plurality of resistors connected in series. The plurality of resistors may include two or more resistors, and may include three or more resistors. The plurality of resistors may include a first resistor (121), a second resistor (122), and a third resistor (123). The first resistor (121) may be connected to the (-) input terminal of the input unit (110), the third resistor (123) may be connected to the (+) input terminal, and the second resistor (122) may be connected between the first resistor (121) and the third resistor (123).

[0048] By connecting the resistors in series, the voltage can be distributed to each resistor using the law of voltage division, and the first voltage of the first resistor (121) and the second resistor (122) can be output. The first resistor (121) is connected to the (-) input terminal, and the voltage output at the node between the first resistor (121) and the second resistor (122) can be the voltage applied to both terminals of the first resistor (121). The first resistor (121) is connected between the first resistor (121) and the third resistor (123), and the voltage output at the node between the second resistor (122) and the third resistor (123) can be the voltage applied to the first resistor (121) and the second resistor (122).

[0049] The offset voltage unit (130) can add an offset voltage to the voltage input from the voltage distribution unit (120). When the voltage is input by being connected in a reverse connection, the magnitude of the voltage input to the input unit (110) and detected can have a (-) value, and when the control unit (140) cannot determine the (-) value or determines the (-) voltage, half of the sensing area is not normally used when measuring the bidirectional current, so that the sensing resolution can be prevented from being damaged. In other words, the reverse connection can be determined only with the (+) voltage without the (-) voltage. To this end, the offset voltage unit (130) can use the offset voltage to increase the voltage sensed when the voltage of the PV module (200) is 0 V by the offset voltage so that it can be used to determine the reverse connection.

[0050] The offset voltage unit (130) may include a differential amplifier (131) to utilize the offset voltage. Using the differential amplifier (131), the offset voltage of the first voltage source (132) may be applied to the first voltage output from the voltage distribution unit (120).

[0051] The offset voltage unit (130) may include a fourth resistor (R4), a fifth resistor (R5), a differential amplifier (131), a sixth resistor (R6), a first voltage source (132), and a seventh resistor (R7). As shown in FIGS. 4 and 5, a voltage distribution unit (120), an offset voltage unit (130), an insulation unit (150), and a control unit (140) may be connected.

[0052] The fourth resistor (R4) is connected to the first node between the first resistor (121) and the second resistor (122), the fifth resistor (R5) is connected to the second node between the second resistor (122) and the third resistor (123), and the differential amplifier (131) may have the fourth resistor (R4) connected to the (-) input terminal and the fifth resistor (R5) connected to the (+) input terminal. The sixth resistor (R6) and the first voltage supply (132) are connected to the (+) input terminal of the differential amplifier so that the offset voltage of the first voltage supply can be applied to the differential amplifier (131). The seventh resistor (R7) may form a feedback path by connecting the output terminal and the (-) input terminal of the differential amplifier (131). The output of the differential amplifier (131) can be applied to the MCU ADC (analog to digital converter), which is the control unit (140), through the isolation amplifier (isolation op-amp), which is the insulation unit (150).

[0053] The offset voltage unit (130) applies the offset voltage of the first voltage source (132) to the first voltage output from the voltage distribution unit (120), so that when the voltage of the PV module (200) is 0 V, the value output from the offset voltage unit (130) becomes the offset voltage, and when the voltage input to the input unit (110) is a (-) voltage due to reverse connection, the value output from the offset voltage unit (130) can have a (+) voltage value from 0 to the offset voltage. Through this, whether or not there is reverse connection can be determined reliably.

[0054] The control unit (140) can determine whether the input unit (110) and the PV module (200) are reversed by using the output of the offset voltage unit (130). When the voltage of the PV module (200) is 0 V, the value output from the offset voltage unit (130) becomes the offset voltage, and when the voltage input to the input unit (110) is a (-) voltage due to reverse connection, the value output from the offset voltage unit (130) has a (+) voltage value from 0 to the offset voltage. Therefore, the control unit (140) can determine whether the reverse connection is present by using the output of the offset voltage unit (130).

[0055] The control unit (140) may determine that the output of the offset voltage unit (130) is normal if it is equal to or greater than the offset voltage, and may determine that it is reversed if it is between 0 and less than the offset voltage. Alternatively, the control unit (140) may determine that the output of the offset voltage unit (130) is normal if it is equal to or greater than the offset voltage, and may determine that it is reversed if it is between 0 and less than the offset voltage. Alternatively, the control unit (140) may determine that the output of the offset voltage unit (130) is normal if it is equal to or greater than the offset voltage, and may determine that it is reversed if it is equal to or greater than the offset voltage.

[0056] When the control unit (140) determines that the connection between the input unit (110) and the PV module (200) is reversed, the operation of the power conversion device (100) can be stopped. When reversed, damage to internal components may occur, so the power conversion operation can be stopped and power input to the input unit (110) can be blocked. When the control unit (140) determines that reversed connection is present, the control unit (140) can provide a reverse connection notification to the upper controller. By transmitting reverse connection information externally, the operator can reconnect the connection normally.

[0057] An insulation unit (150) may be included to insulate between the offset voltage unit (130) and the control unit (140). The input unit (110) may be supplied with main power, and the control unit (140) may operate as an auxiliary power source. Since the input unit (110) side and the control unit (140) side may have different reference potentials, insulation may be required. For this purpose, an insulation unit (150) may be included between the offset voltage unit (130) and the control unit (140). If the offset voltage unit (130) and the control unit (140) use the same reference potential, the insulation unit (150) may not be included.

[0058] The isolation unit (150) may include an isolation amplifier (151). The isolation amplifier (151) is an isolation OP-amp, which is an amplifier in which there is no electrical connection between the signal circuit and other circuits, including the ground. By using the isolation amplifier (151), the offset voltage unit (130) and the control unit (140) can be insulated.

[0059] The result of detecting reverse wiring using offset voltage may be as shown in Fig. 6. When the voltage (Pvin) input from the PV module (200) is -100 to 450 V, the output voltage (Vdc_out) of the reverse wiring detection circuit applied to the control unit (140) may be 0 to 1.2 V. The voltage (Pvin) having a (-) value may mean that reverse wiring has occurred. The magnitude of the voltage sensed through the voltage divider can be reduced, and reverse wiring can be detected using only the (+) voltage using the offset voltage. That is, when the control unit (140) detects a voltage between 0 and the offset voltage as the voltage of the input unit (110), it can be determined as reverse wiring.

[0060] A simple circuit consisting of an op-amp and a few resistors can be used to detect reverse wiring. This circuit configuration reduces circuit costs and utilizes existing voltage sensing circuits, eliminating additional losses. Since negative voltage sensing is possible with only a slight offset voltage, there's no significant loss in voltage resolution.

[0061] Fig. 7 is a block diagram of a reverse connection detection circuit according to an embodiment of the present invention. A detailed description of each component of Fig. 7 corresponds to the detailed description of the power conversion device of Figs. 1 to 6, and thus, redundant descriptions will be omitted below. A reverse connection detection circuit (300) according to an embodiment of the present invention may include a voltage distribution unit (120) and an offset voltage unit (130). A reverse connection detection circuit (300) according to an embodiment of the present invention includes an offset voltage unit (130) that connects both ends of an input unit (110), receives a first voltage of at least one resistor among a plurality of resistors connected in series, and adds an offset voltage, and can apply an output of the offset voltage unit (130) to a control unit (140) that determines whether or not a reverse connection occurs.

[0062] The plurality of resistors include a first resistor (121), a second resistor (122), and a third resistor (123) connected in series, and the first voltage source (132) can input an offset voltage to the differential amplifier (131).

[0063] The offset voltage unit (130) may include a fourth resistor (R4), a fifth resistor (R5), a differential amplifier (131), a sixth resistor (R6), a first voltage source (132), and a seventh resistor (R7). The fourth resistor (R4) may be connected to a first node between the first resistor (121) and the second resistor (122), the fifth resistor (R5) may be connected to a second node between the second resistor (122) and the third resistor (123), and the differential amplifier (131) may have the fourth resistor (R4) connected to a (-) input terminal and the fifth resistor (R5) connected to a (+) input terminal. The sixth resistor (R6) and the first voltage source (132) may be connected to the (+) input terminal of the differential amplifier so that an offset voltage of the first voltage source can be applied to the differential amplifier (131). The seventh resistor (R7) can form a feedback path by connecting the output terminal and the (-) input terminal of the differential amplifier (131). The output of the differential amplifier (131) can be applied to the MCU ADC (analog to digital converter), which is the control unit (140), through the isolation amplifier (isolation op-amp), which is the insulation unit (150).

[0064] 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 connected to the PV module; A voltage distribution unit that distributes the voltage at both ends of the input unit; An offset voltage unit that adds an offset voltage to the voltage input from the voltage distribution unit; and A power conversion device including a control unit that determines whether the input unit and the PV module are reverse-connected using the output of the offset voltage unit.

2. In paragraph 1, The above control unit, A power conversion device that determines that the connection between the input unit and the PV module is reversed when the output of the offset voltage unit is lower than or equal to the offset voltage.

3. In paragraph 1, The above voltage distribution unit is, Connecting both ends of the above input section, and including a first resistor, a second resistor, and a third resistor connected in series, A power conversion device that outputs the first voltage of the first resistor and the second resistor.

4. In paragraph 3, The above offset voltage section is, A power conversion device including a differential amplifier that adds an offset voltage of a first voltage source to the first voltage output from the voltage distribution unit.

5. In paragraph 4, The above offset voltage section is, A fourth resistor connected to the first node between the first resistor and the second resistor; A fifth resistor connected to the second node between the second resistor and the third resistor; A differential amplifier in which the fourth resistor is connected to the (-) input terminal and the fifth resistor is connected to the (+) input terminal; A sixth resistor and a first voltage source connected to the (+) input terminal of the above differential amplifier; and Including a seventh resistor connecting the output terminal of the above differential amplifier and the (-) input terminal, The above first voltage source is a power conversion device that inputs the above offset voltage to the differential amplifier.

6. In paragraph 1, A power conversion device including an insulation section that insulates between the offset voltage section and the control section.

7. In paragraph 6, The above insulating part is a power conversion device including an insulating amplifier.

8. In paragraph 1, The above control unit, A power conversion device that stops the operation of the power conversion device when the connection between the input part and the PV module is judged to be reversed.

9. In paragraph 1, The above control unit, A power conversion device that provides a reverse connection notification to an upper controller when the connection between the above input unit and the PV module is judged to be reversed.

10. In paragraph 1, A power conversion device including an insulation section that insulates between the offset voltage section and the control section.

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