KR20230053447A - power converting apparatus - Google Patents

Abstract

A power converter according to an embodiment of the present invention includes a converter including at least one upper switch and at least one lower switch, and an auxiliary power unit supplying driving power to the upper switch and the lower switch, wherein the auxiliary power converter The power supply unit includes a bootstrap circuit for supplying driving power to the upper switch using first driving power supplying driving power to the lower switch.

Description

Power converting apparatus {power converting apparatus}

The present invention relates to a power conversion device, and more particularly, to a power conversion device operating in multiple operation modes.

Photovoltaic power generation is widely used as an eco-friendly energy generation method to replace existing chemical power generation or nuclear power generation. There are two types of photovoltaic power generation: a stand-alone type in which a battery is connected to a converter, and a linked type in connection with the power grid. It is configured to mutually exchange power with the load grid line.

Solar cell modules have different maximum power points depending on the amount of sunlight and temperature. Module-level power electronics (MLPE) can be used to perform maximum power point tracking (MPPT) control on a module basis to operate the solar cell at its maximum power point. The MLPE converts the power received from the solar cell to track the maximum power point. Depending on the situation, it may be necessary to directly output the input voltage as the output voltage without power conversion.

Therefore, in order to optimize the photovoltaic cell module, a technique for implementing the MLPE to operate in various operating modes is required.

A technical problem to be solved by the present invention is to provide a power converter that operates in multiple operation modes.

In order to solve the above technical problem, a power converter according to an embodiment of the present invention includes a converter including at least one upper switch and at least one lower switch; and an auxiliary power unit supplying driving power to the upper switch and the lower switch, wherein the auxiliary power unit supplies driving power to the upper switch by using a first driving power supplying driving power to the lower switch. Includes a bootstrap circuit.

In addition, the bootstrap circuit may include a capacitor charged by receiving power from the first driving power source; and a diode connected between the first driving power supply and the capacitor, wherein the capacitor is connected to a node between the upper switch and the lower switch, and when the lower switch is turned on, the first driving power supply; A closed loop connected to the diode, the capacitor, and the lower switch is formed to receive power from the first driving power source and charge. When the lower switch is turned off, power is received from the first driving power source and charged. The power may be supplied as the driving power of the upper switch.

In addition, the converter operates in a first mode in which the upper switch and the lower switch are complementaryly conducted at a first frequency, or in a second mode in which the upper switch and the lower switch are complementaryly conducted at a second frequency. And, the first frequency may be different from the second frequency.

Also, the second frequency may be smaller than the first frequency.

Also, the second frequency may be 1/4 or less of the first frequency.

Also, the first frequency may be 20 kHz or higher.

In addition, the second frequency may be set according to the input/output voltage, current, and temperature of the converter.

In addition, a first period in which the upper switch conducts and a second period in which the lower switch conducts is included, and in the converter, in the second mode, a ratio between the first period and the second period is a first ratio and, as for the first ratio, the first interval may be longer than the second interval.

In addition, when the mode is changed, the converter may gradually change the ratio between the first section and the second section.

Also, in the second mode, a difference between a voltage of an input unit of the converter and a voltage of an output unit of the converter may be less than or equal to a first threshold voltage value.

In addition, the converter operates in a third mode in which the lower switch is connected for a first period or more, and when the upper switch is connected between the lower switch and the output (+) terminal, the upper switch operates in the third mode. may be simultaneously connected to the lower switch for the first cycle or longer.

In addition, the converter includes at least one of a buck converter, a boost converter, and a buck boost converter, and in the third mode, only a lower switch of the buck converter is connected, and both an upper switch and a lower switch of the boost converter are connected In the buck-boost converter, both the high-side switch and the low-side switch of the output side may be connected.

In addition, the input unit for receiving the first voltage; and an output unit outputting an output voltage of the converter, wherein the converter operates in a first mode for converting the first voltage into a second voltage or a second mode for outputting the first voltage to the output unit; , The output unit may output the second voltage in the first mode and output the first voltage in the second mode.

In addition, the converter may operate in a third mode generating a bypass path to the output unit, and the output unit may output a third voltage input from an output side in the third mode.

In order to solve the above technical problem, a power converter according to another embodiment of the present invention includes a plurality of power circuits constituting a multi-level, and each power circuit includes the power converter described above.

According to embodiments of the present invention, the power conversion device can be used in multiple operation modes including a power conversion mode, an input/output connection mode, and a bypass mode. An input/output connection mode or a bypass mode can be implemented or enhanced using a power conversion circuit. In operating the power conversion circuit in a power conversion mode or an input/output connection mode, an auxiliary power circuit for supplying driving power to the upper switch and the lower switch can be implemented simply and inexpensively using a bootstrap circuit.

1 is a diagram for explaining maximum power point follow-up control.
2 is a block diagram of a power conversion device according to an embodiment of the present invention.
3 to 11 are views for explaining a power conversion device according to an embodiment of the present invention.
12 is a block diagram including an auxiliary power supply unit of a power converter according to an embodiment of the present invention.
13 to 17 are views for explaining the power converter according to the embodiment of FIG. 12 .
18 is a block diagram of a power converter in which a plurality of power circuits are composed of multi-levels according to an embodiment of the present invention.
19 to 21 are views for explaining the power converter according to the embodiment of FIG. 18 .

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

However, the technical idea of the present invention is not limited to some of the described embodiments, but may be implemented in a variety of different forms, and if it is within the scope of the technical idea of the present invention, one or more of the components among the embodiments can be selectively implemented. can be used in combination or substitution.

In addition, terms (including technical and scientific terms) used in the embodiments of the present invention, unless explicitly specifically defined and described, can be generally understood by those of ordinary skill in the art to which the present invention belongs. It can be interpreted as meaning, and commonly used terms, such as terms defined in a dictionary, can be interpreted in consideration of contextual meanings of related technologies.

Also, terms used in the embodiments of the present invention are for describing the embodiments and are not intended to limit the present invention.

In this specification, the singular form may also include the plural form unless otherwise specified in the phrase, and when described as "at least one (or more than one) of A and (and) B and C", A, B, and C are combined. may include one or more of all possible combinations.

In addition, in describing the components of the embodiment of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are only used to distinguish the component from other components, and the term is not limited to the nature, order, or order of the corresponding component.

And, when a component is described as being 'connected', 'coupled', or 'connected' to another component, the component is directly 'connected', 'coupled', or 'connected' to the other component. In addition to the case, it may include cases where the component is 'connected', 'combined', or 'connected' due to another component between the component and the other component.

In addition, when it is described as being formed or disposed on the "upper (above)" or "lower (below)" of each component, "upper (above)" or "lower (below)" means that two components are directly connected to each other. It includes not only contact, but also cases where one or more other components are formed or disposed between two components. In addition, when expressed as "upper (above)" or "lower (down)", the meaning of not only an upward direction but also a downward direction may be included based on one component.

Modifications according to this embodiment may include some configurations of each embodiment and some configurations of other embodiments. That is, the modified example may include one embodiment among various embodiments, but some components may be omitted and some configurations of other corresponding embodiments may be included. Or, it may be the other way around. Features, structures, effects, etc. to be described in the embodiments are included in at least one embodiment, and are not necessarily limited to only one embodiment. Furthermore, the features, structures, and effects illustrated in each embodiment can be combined or modified with respect to other embodiments by those skilled in the art in the field to which the embodiments belong. Therefore, contents related to these combinations and variations should be interpreted as being included in the scope of the embodiments.

A power conversion device according to an embodiment of the present invention may be a device that converts power generated from a photovoltaic panel into power suitable for a load or a battery. A photovoltaic cell performing photovoltaic power generation may be expressed in a cell string unit in which a plurality of cells are connected in series.

A cell string may include at least one or more cells, and when including a plurality of cells, the plurality of cells may be connected in series. The cell string may be a solar cell string including solar cells. A string of photovoltaic cells may form a solar panel. Photovoltaic cells generate photovoltaic (PV) power by using the photoelectric effect. The photoelectric effect is the emission of electrons when light of a certain frequency or higher hits a specific metal material. A pn junction is formed using a p-type semiconductor and an n-type semiconductor, and electric power is generated by using electrons generated by the photoelectric effect to generate current. generate A solar cell is formed using silicon or the like and may be formed in a wafer form. The photovoltaic cell is located in a field that can receive sunlight well, an outer wall of a building, or a rooftop, and generates electric power using sunlight. At this time, the photovoltaic cell may be formed of BIPV (building-integrated photovoltaic power generation) formed integrally with the building.

Since the size of the power generated by one solar cell is not enough to be used in a load or power system, a plurality of solar cells are connected in series to form a solar cell string. It can generate power of suitable size. A string of solar cells may be a basic unit for generating electrical power. A solar power generation panel may be formed by forming a plurality of cell strings, which are basic units, into a panel. As shown in FIG. 1 , solar cells have different voltage-current characteristics depending on the amount of sunlight, temperature, and the like, and the maximum power point (MPP) is also varied. (generated power = voltage X current) The power conversion device controls the solar cell to operate at the maximum power point (MPP), which is the operating point at which the solar cell has the maximum power under each condition. This is referred to as Maximum Power Point Tracking (MPPT), and efficiency of photovoltaic power generation can be increased by using Maximum Power Point Tracking. In photovoltaic power generation, depending on the characteristics of the relationship between current and voltage and voltage and power, the maximum power may be about 80% of the maximum voltage, not the maximum voltage. Since such a maximum power point continuously changes according to the magnitude of the voltage and current generated by the solar panel, it is necessary to continuously find a point where the maximum power point can be generated. That is, in order to follow the maximum power rather than the maximum voltage, the magnitudes of the voltage and current may be varied so as to reach the maximum power. That is, the voltage may be decreased and the current may be increased, or the voltage may be increased and the current may be decreased in the direction of increasing power.

In order to perform maximum power point tracking for a plurality of cell strings, individual control for each cell string may be required. For example, if a foreign substance obstructs light reception or is shaded in a specific cell string, the degree of power generation may be different from that of other cell strings, so that not only the operation mode of converting the power output from the cell string, but also the operation other than power conversion is performed. may be needed It may be necessary to directly output the power output from the cell string without converting it, or to bypass the corresponding cell string. For each situation, a device capable of multiple operation modes capable of operating in a mode most suitable for power output from each cell string is required.

In order to operate in the most suitable mode for each situation, the power conversion device according to an embodiment of the present invention includes a power conversion mode (first mode), an input/output connection mode (second mode), and a bypass mode (third mode). It can operate in multiple modes. In addition to the power conversion mode, the input/output connection mode, and the bypass mode, other operation modes may be further included according to design.

2 is a block diagram of a power conversion device according to an embodiment of the present invention, and FIGS. 3 to 11 are diagrams for explaining the power conversion device according to an embodiment of the present invention.

The power conversion device 100 according to an embodiment of the present invention is composed of an input unit 110, a power conversion unit 120, an output unit 130, an input/output connection unit 140, and a bypass unit 150, It may include a monitoring unit, an auxiliary power unit, a temperature sensor, a control unit, a coupling circuit, and a wireless transceiver.

The input unit 110 receives a first voltage. The input unit 110 may be connected to the cell string to receive a first voltage.

The power converter 120 converts the first voltage into a second voltage. When the first voltage is input to the input unit, the power conversion unit 120 converts the first voltage into a second voltage according to the power conversion mode. The first voltage may be higher or lower than the second voltage. The power converter 120 may convert the input first voltage into a second voltage higher than the first voltage or into a second voltage lower than the first voltage. Alternatively, the first current may be converted into the second current. Here, the first current may be higher or lower than the second current. The power conversion unit 120 may include a converter for converting power.

The output unit 130 outputs the output voltage of the power conversion unit 120 . The output unit 130 outputs the second voltage that is converted and output by the power conversion unit 120 .

In a power conversion mode in which maximum power point tracking is performed on the received power and power is converted, power conversion is performed through the input unit 110 , the power conversion unit 120 , and the output unit 130 . Maximum power point tracking is performed so that the power of the cell string to which the input unit 110 is connected becomes the maximum power.

The input/output connection unit 140 connects the input unit 110 to the output unit 130 . In order to perform the input/output connection mode in which the input voltage is directly transmitted to the output side without converting according to circumstances, the input/output connection unit 140 connects the input unit 110 and the output unit 130 in the input/output connection mode. For example, when some of the cell strings generate a lower voltage than other cell strings due to shading, etc., in order to reduce loss and increase efficiency by reducing the voltage difference between each cell string, the voltage of the other cell strings It is necessary to output as it is without power conversion. At this time, the input/output connection unit 140 connects the input unit 110 and the output unit 130 to perform the input/output connection mode. The first voltage received in the input/output connection mode is output as it is, and the voltage output from the output unit 130 becomes the first voltage of the input unit 110.

The bypass unit 150 creates a bypass path in the output unit 130 that bypasses the power conversion unit 120 or the input/output connection unit 140 . In order to bypass the power conversion unit 120 and the input/output connection unit 140 as well as the input/output connection mode that outputs the input voltage as it is without performing power conversion, a bypass path is provided so that the output unit 130 is connected only to the output side. It can operate in bypass mode that creates Bypass mode discharges the output voltage of the power converter or maintains it below a preset voltage or 0 V. In the bypass mode, the bypass unit 150 creates a bypass path in the output unit 130 to prevent current input from the output unit 130 from flowing to the power conversion unit 120 .

For example, when the current of the output unit 130 is greater than the current of the input unit 110, the bypass unit 150 may provide a bypass path for the current corresponding to the difference. For example, when a failure occurs in a photovoltaic module including a cell string or there is no input current input to the power converter because the input unit is not connected, the bypass unit 150 establishes a bypass path for the output current. can provide In particular, when a hot-spot occurs in the photovoltaic module, the bypass unit 150 provides a detour path for the output current to lower the current value flowing through the photovoltaic module, thereby suppressing heat generation. Through this, when the photovoltaic module forcibly conducts a current greater than the outputable current, it is possible to prevent an increase in heat generation due to an increase in impedance of the photovoltaic module.

The output unit 130 outputs the first voltage, the second voltage, the output unit 130 according to the operation of the power conversion unit 120, the input/output connection unit 140, or the bypass unit 150 operating according to the respective modes. Alternatively, the third voltage input from the output side is output. That is, in the power conversion mode, the second voltage output from the power conversion unit 120 is output, and in the input/output connection mode, the first voltage that is directly connected to the input unit 110 and received by the input unit 110 is output as it is, and In the pass mode, regardless of the voltage of the power conversion unit 120 or the input unit 110, the third voltage input to the output side is output.

The power conversion unit 120, the input/output connection unit 140, and the bypass unit 150 can be operated by a control unit, and the control unit sends a control signal to operate in the most appropriate mode according to information such as input/output voltage, current, and temperature. Can be sent to each configuration. In addition, it may operate in a corresponding mode according to a control signal from an external controller or a user's input.

As shown in FIG. 3, the power converter 100 according to an embodiment of the present invention bypasses the power converter 120 and the power converter 120 and connects the input and output units. 140), and a bypass circuit 150 that creates a bypass path in the output unit 130 by connecting both ends of the output terminal. The input/output connection unit 140 is a kind of bypass circuit that bypasses or bypasses the power conversion unit 120, but is referred to as an input/output connection unit 140 or a contactor in order to differentiate it from the bypass unit 150. do.

As shown in FIG. 4 , the power converter 100 according to an embodiment of the present invention may include various components to operate in multiple operation modes.

An auxiliary power supply for generating auxiliary power using the voltage of the input unit 110 or the voltage of the output unit 130 may be included. The auxiliary power unit may receive one or more of the voltages of the input unit or the output unit of the power conversion device to generate single or multiple power sources. The generated power may be a voltage commonly used by semiconductor devices, such as 3.3V, 5V, or 12V. Some power supplies may have a potential floating on the ground of the power converter. The auxiliary power unit may be composed of a single or multiple power conversion circuits. For example, at least one of a fly-back converter, a buck converter, a boost converter, a linear regulator, and a charge pump, or a combination thereof may consist of

A monitoring circuit may measure at least one of a current of the input unit 110 , a voltage of the input unit 110 , a current of the output unit 130 , and a voltage of the output unit 130 .

The memory may include non-volatile memory for storing information. Physical/software identification information, monitoring correction information, failure history, and the like may be stored in the memory.

A thermal sensor for measuring temperature may be included. The temperature sensor may measure the temperature of the power converter. In particular, the temperature sensor can measure the temperature of a magnetic component such as a MOFSET, a diode, a power semiconductor device, a transformer, or an inductor, or the temperature of a nearby region in a contact or non-contact manner.

The control circuit may control each component of the power converter by using the power converter and information received from the outside. At this time, according to the circuit of the power conversion unit 120, an additional current detection circuit for detecting the current of the inductor included in the power conversion unit 120 may be used. The control unit may activate a protection function based on the detected voltage, current, and temperature information. For example, when overvoltage or overcurrent is detected, a specific parameter may be limited or the operation of the power converter may be stopped. In addition, when overheating is detected, output power of the power converter may be lowered or stopped.

The controller detects various parameters, controls power circuits, communicates with external equipment, and stores information. Signals input from the monitoring unit can be recognized by ADC (analog digital converter), and power circuits can be controlled by outputting PWM or GPIO. In addition, based on the signal input from the monitoring unit, the power circuit may be controlled to follow an operating point at which power supplied from the PV module is maximized. Based on the signal detected by the monitoring unit, overvoltage and overcurrent protection functions may be implemented, and information may be transmitted and received by communicating with an external device. A wired method and a wireless method may be used as a communication means. In the case of a wired method, an additional terminal for connecting a cable for communication may be provided, and in the case of a wireless method, a wireless transceiver for communication may be additionally provided. In the case of using PLC (Power Line Communication), a coupling circuit may be additionally provided to the (+) terminal or (-) terminal of the output terminal. The transmission information may include a parameter detected in the power converter, failure status and failure history, physical/software identification information, correction information of a monitoring circuit, and the like. A capacitor for removing noise may be additionally used between the (+) terminal and the (-) terminal of the power circuit.

The power converter 120 may include a converter including at least one upper switch and at least one lower switch. Power conversion is performed by controlling the on/off of the upper and lower switches. In this case, the upper switch and the lower switch may be complementary to each other. Each switch may be controlled with a turn-on time, that is, a constant duty ratio. Here, the duty ratio means an on-in ratio within a certain period, and is also referred to as a fertilization ratio. Each switch may be a switching element that operates by receiving driving power, and the switching element may be a semiconductor switching element such as FET, MOSFET, or IGBT.

The power converter 120 may include a DC-DC converter, and at this time, may include at least one of a buck converter, a boost converter, and a buck boost converter. As shown in FIG. 5(A), the power conversion unit 120 may be implemented as a buck converter configured of an upper switch, a lower switch, and an inductor to lower a voltage. At this time, the input current can be converted into a high current. Also, as shown in FIG. 5(B) , it may be implemented as a boost converter configured of an inductor, an upper switch, and a lower switch to increase voltage. At this time, the input current may be converted into a low current. Also, as shown in FIG. 5(C) , it may be implemented as a buck boost converter configured of a first high-side switch, a first low-side switch, an inductor, a second high-side switch, and a second low-side switch to lower or increase a voltage. Capacitors may be connected in parallel to input and output terminals of each converter.

The input/output connection unit 140 may include a switching element connecting the input unit 110 and the output unit 130 to each other. The input/output connection unit 140 outputs the input voltage and current to the output unit 130 without converting them by connecting the input unit 110 and the output unit 130 . At this time, a mechanical switching element such as a relay or a semiconductor switching element such as a MOSFET or a diode may be used singly or in combination as the switching element. The input/output connection unit 140 may include an inductor and a capacitor for noise reduction.

The input/output connection unit 140 may include at least one of one MOSFET including a body diode having a cathode connected to the input unit 110 and two MOSFETs serially connected to a common source or common drain. As shown in FIG. 6, the input/output connection unit 140 may be implemented with various switching elements. When implemented as a mechanical switch as shown in FIG. 6(A) or as a MOSFET including a body diode as shown in FIG. It may be connected between the parts 130. In addition, when implemented with two MOSFETs, they can be serially connected to a common source as shown in FIG. 6(C) or serially connected to a common drain as shown in FIG. 6(D). Stability can be increased by connecting two MOSFETs in series with a common source or common drain.

The bypass unit 150 may include a switching element connecting the (+) terminal and the (-) terminal of the output unit 130 . In this case, the bypass unit 150 may include at least one of a MOSFET including a diode having a cathode connected to the (+) terminal of the output unit and a body diode having a cathode connected to the (+) terminal of the output unit. The bypass unit 150 connects the (+) terminal and the (-) terminal of the output unit 130 so that current flows from the (-) terminal to the (+) terminal in order to form a path to the output terminal. It should be. To this end, as shown in FIG. 7 , a diode or a body diode may be included. As shown in FIG. 7 (A), the cathode is implemented as a diode connected to the (+) terminal of the output unit, or as shown in FIG. 7 (B), the cathode includes a body diode connected to the (+) terminal of the output unit. It may be implemented as a MOSFET, or a MOSFET including a diode and a body diode may be connected in parallel as shown in FIG. 7(C), or a diode and a switching element of another type may be connected in parallel as shown in FIG. 7(D).

As described above, according to the operation of the power conversion unit 120, the input/output connection unit 140, and the bypass unit 150, the power conversion device operates in multiple operation modes of power conversion mode, input/output connection mode, and bypass mode. can Through this, it is possible to operate in the most suitable mode according to the situation.

In allowing the power converter 100 to operate in multiple operation modes, the converter may be implemented to operate in multiple operation modes of a power conversion mode, an input/output connection mode, and a bypass mode. To this end, the converter includes at least one high-side switch and at least one low-side switch.

The converter has a first mode (power conversion mode) in which the first voltage received by the input unit 110 is converted into a second voltage, a second mode in which the first voltage is output to the output unit 130 (input/output connection mode), It can operate in a third mode (bypass mode) generating a bypass path in the output unit 130 . The output unit 130 outputs the second voltage in the power conversion mode, the first voltage in the input/output connection mode, and the third voltage input from the output side in the bypass mode according to the operation of the converter according to each mode. can

The converter may convert the first voltage into the second voltage by complementary conduction of the upper switch and the lower switch in a power conversion mode. The power conversion mode is a general operation of the converter, and the upper switch and the lower switch are conducted at a duty ratio according to the voltage or current of the power to be converted, and accordingly, the input first voltage is converted into the second voltage.

The converter may output the first voltage to the output unit by keeping the upper switch turned on and the lower switch turned off in the input/output connection mode. In the input/output connection mode, the input unit 110 and the output unit 130 are directly connected. At this time, the upper switch is connected between the input unit 110 and the output unit 130, the upper switch is kept on, and the lower switch is turned off to maintain a state in which the input unit 110 and the output unit 130 are connected. do.

As shown in FIG. 8 , when the converter is implemented as a buck converter, a boost converter, and a buck-boost converter, the input unit and the output unit can be directly connected by keeping only the upper switch turned on in the input/output connection mode. As shown in FIG. 8(A), in the buck converter, a path is formed through the input unit 110, the high-side switch, the inductor, and the output unit 130, so that the first voltage of the input unit 110 is output to the output unit 130 without power conversion. do. As shown in FIG. 8(B), in the boost converter, a path is formed through the input unit 110, the inductor, the high-side switch, and the output unit 130, so that the first voltage of the input unit 110 is output to the output unit 130 without power conversion. do. As shown in FIG. 8(C), in the buck boost converter, a path is formed through the input unit 110, the first high-side switch, the inductor, the second high-side switch, and the output unit 130, so that the first voltage of the input unit 110 is generated without power conversion. It is output to the output unit 130. The inductor located on the input/output connection path can perform the function of a filter for reducing noise, so that power can be transmitted more stably.

At this time, it may include a switching element that connects the input unit 110 and the output unit 130 in the input/output connection mode and is connected in parallel with the converter. An input/output connection mode may be implemented by connecting the converter and the input/output connection unit 140 in parallel. Since the converter and the input/output connection unit 140 each form an input/output connection path, current stress and heat generation of the device can be reduced. As shown in FIG. 9, switching elements such as MOSFETs including body die diagrams are connected in parallel to the input and output terminals of the buck converter (A), the boost converter (B), and the buck boost converter (C) to form a plurality of input/output connection paths. can

When operating in the bypass mode, the converter may control on/off of the upper switch or the lower switch to form a bypass path in the output unit 130 according to the type of converter.

In bypass mode, if the converter is a buck converter, only the low-side switch is connected, if it is a boost converter, both the high-side switch and low-side switch are connected, and if it is a buck-boost converter, both the output side high-side switch and low-side switch are connected, respectively, Paths can be created. As shown in FIG. 10 (A), in the buck converter, only the lower switch is connected, and a bypass path is formed with the output (-) terminal, the lower switch, the inductor, and the output (+) terminal, and input to the output (-) terminal. The voltage to be is output to the output unit 130 as it is. As shown in FIG. 10(B), the boost converter has a bypass path formed by the (-) terminal of the output unit, the lower switch, the upper switch, and the (+) terminal of the output unit, so that the voltage input to the (-) terminal of the output unit is output as it is. It is output to unit 130. As shown in FIG. 10(C), in the buck boost converter, a bypass path is formed with the (-) terminal of the output part, the second lower switch, the second upper switch, and the (+) terminal of the output part, and the input is input to the (-) terminal of the output part. The voltage to be is output to the output unit 130 as it is. At this time, the first upper switch should be turned off, but the first lower switch may be selectively turned on and off. When the first lower switch is turned on, an additional bypass path may be formed by the (−) terminal of the output unit, the first lower switch, the inductor, the second upper switch, and the (+) terminal of the output unit.

In this case, in the bypass mode, a switching element connecting a (+) terminal and a (-) terminal of the output unit and connected in parallel with the converter may be included. A bypass mode may be implemented by connecting the converter and the bypass unit 150 in parallel. Since the converter and the bypass unit 150 each form a bypass path, current stress and heat generation of the device can be reduced. As shown in FIG. 11 , a plurality of bypass paths may be formed by connecting switching elements such as diodes in parallel to input and output terminals of the buck converter A, the boost converter B, and the buck boost converter C.

In operating a converter including at least one upper switch and at least one lower switch in a power conversion mode, an input/output connection mode, and a bypass mode, the converter comprises the upper switch and the lower switch during a first period in the power conversion mode. A connection state of a switch may be changed at least once, only the upper switch may be connected for the first period or more in an input/output connection mode, and the lower switch may be connected for the first period or more in a bypass mode. When the upper switch is connected between the lower switch and the output (+) terminal, the upper switch may be simultaneously connected to the lower switch for the first period or longer in the bypass mode. When the power converter 100 is implemented as a converter and operates in each mode, the operation time of each switch of the converter may vary according to the operation mode.

When the power conversion unit 120, the input/output connection unit 140, and the bypass unit 150 operate, they operate according to the operation of each component, but when the converter operates in the first to third modes, each switch Operating time varies.

In the power conversion mode, the power conversion unit 120 operates and provides an output value different from an input value (eg, voltage or current). For example, an input value with low current and high voltage can be converted into an output value with low voltage and high current. The reverse is also possible. In the power conversion unit 120 implemented as a converter, the conduction state of the upper switch and the lower switch is changed at least once during the first cycle, which is a switching cycle. Here, the first period may be variable. For example, the first cycle may be set according to the detected voltage, current, temperature, and the like. A switching operation is performed with a set duty within the first period to convert power.

In the input/output connection mode, the input/output connection unit 140 operates and provides the same output value as the input value. For example, the input current and the output current may be the same. When the power converter 120 is implemented as a converter, the converter may replace the function of the input/output connector 140 or may be connected in parallel with the input/output connector 140 to operate. In the input/output connection mode, the upper switch needs to be connected, and the upper switch can maintain a conduction state for a longer period than the first period.

In the bypass mode, the bypass unit 150 operates to provide an electrical path between the (-) terminal and the (+) terminal of the output unit. For example, when the output current of the power circuit is greater than the current input from the PV module, the bypass circuit can provide a conduction path for the current corresponding to the difference. For example, when there is no input current in the power circuit due to a PV module failure or non-connection, the bypass circuit can provide an output current conduction path. When a hot-spot occurs in the PV module, the bypass unit 150 provides a detour path for the output current to lower the current value flowing through the PV module, thereby suppressing heat generation of the PV module. Through this, when a current larger than the outputable current of the PV module is forcibly conducted, it is possible to prevent an increase in heat generation due to an increase in the impedance of the PV module. When the power conversion unit 120 is implemented as a converter, the converter may replace the function of the bypass unit 150 or be connected in parallel with the bypass unit 150 to operate. In the bypass mode, the connection between the (-) terminal and the (+) terminal of the output unit should be maintained, and the lower switch may maintain the conduction state of the switching element for a longer time than the first period. If the converter is a buck converter, only the lower switch maintains conduction for a longer period of time than the first cycle, the converter is a boost converter, and both the upper switch and the lower switch maintain conduction for a longer period of time than the first cycle, and the converter is a buck-boost converter In this case, the second upper switch and the second lower switch may maintain conduction for a longer period than the first period.

An operation mode of the power converter 100 may be set based on a parameter detected by a monitoring unit or a temperature sensor. Also, an operation mode may be set based on information received from the outside through communication. In addition to the three operating modes, additional modes can be added as needed. For example, additional modes for power converter protection may be used. When the mode is changed, a transient section may exist, and it may be defined as a separate mode if necessary.

12 is a block diagram including an auxiliary power supply unit of a power converter according to an embodiment of the present invention. The power converter 200 may include a converter 210 including at least one upper switch 211 and at least one lower switch 212, the upper switch 211 and the lower switch 212 It may include an auxiliary power supply unit 220 for supplying driving power to. At this time, the auxiliary power supply unit 220 uses the first driving power supply 221 for supplying driving power to the lower switch 212 to provide a bootstrap circuit 222 for supplying driving power to the upper switch 211. include Here, only the configuration for supplying driving power to the upper switch 211 and the lower switch 212 of the converter 210 will be mainly described, and the auxiliary power unit 220 is the upper switch 211 and the lower switch 211 of the converter 210. It goes without saying that auxiliary power can be supplied to components other than the switch 212 .

The auxiliary power unit 220 supplies driving power to the upper switch 211 and the lower switch 212 of the converter 210 . Each switch may be a switching element that operates by receiving driving power, and requires auxiliary power to operate each switch. The switching element may be a semiconductor switching element such as a Si or SiC-based MOSFET, GaN HEMT, or IGBT.

The auxiliary power unit 220 may supply auxiliary power to the upper switch 211 using an isolated converter instead of the bootstrap circuit 222 . At this time, the auxiliary power unit includes a primary circuit receiving a voltage of at least one output terminal among output terminals of a plurality of cell strings, an insulated converter outputting a voltage to the first secondary circuit according to the voltage of the primary circuit, and the insulation and a plurality of first secondary circuits supplying driving power to each of the upper switches of the plurality of converters by using a voltage output from the converter. In this case, driving power may be supplied to the upper switch independently of whether the lower switch operates.

The power converter 100 according to the embodiment of FIG. 12 can simply supply driving power to the upper switch 211 using the bootstrap circuit 222 . To this end, the auxiliary power unit 220 generates driving power to be supplied to the upper switch 211 using the first driving power supply 221 for supplying driving power to the lower switch 212 and the first driving power supply 221 A bootstrap circuit 222 is included. When the upper switch 211 and the lower switch 212 are implemented as MOSFETs, as shown in FIG. 13 , driving power must be supplied to a gate driver (driving circuit) that supplies a driving voltage to the gate. The gate driver supplies a gate voltage to the gate of each switch according to a driving signal of a control unit such as an MCU or a PWM controller. Here, a PWM signal having a 3.3V or 5V level may be used as the driving signal.

As shown in FIG. 13 , when the converter 210 is a buck converter, in the case of a low side switch, the source terminal may be directly connected to the negative electrode of the first driving power source, so that the auxiliary power source may be directly used during driving. However, since the source terminal of the upper switch is not directly connected to the negative electrode of the first driving power source, the gate driver cannot directly use the auxiliary power source. Therefore, a separate driving power source must be generated by using it through a bootstrap circuit.

As shown in FIG. 14, even if the converter 210 is a boost converter (A) or a buck-boost converter (B), it includes a high-side switch. can include

The bootstrap circuit 222 includes a capacitor charged by receiving power from the first driving power source 221; and a diode connected between the first driving power source 221 and the capacitor. Here, the capacitor is connected to a node between the upper switch 211 and the lower switch 212, and when the lower switch 212 is turned on, the first driving power supply 221, the diode, and the capacitor , and a closed loop connected to the lower switch 212 is formed to receive power from the first driving power source 221 to be charged, and when the lower switch 212 is turned off, the first driving power source 221 ), the charged power can be supplied as the driving power of the upper switch 211.

As shown in FIG. 15 , the bootstrap circuit 222 may include a diode 223 and a capacitor 224 . The capacitor 224 has one end connected to the first driving power source 221 through a diode 223 and the other end connected to the node 225 between the upper switch 211 and the lower switch 212. When the lower switch 212 is turned on, a closed loop connected to the first driving power supply 221, the diode 223, the capacitor 224, and the lower switch 212 is formed, and the first driving power supply 221 It is charged by receiving power. At this time, the upper switch 211 is turned off, and the capacitor 224 is only charged.

Thereafter, when the lower switch 212 is turned off, the lower switch 212 is opened so that a loop connected to the first driving power source 221, the diode 223, the capacitor 224, and the lower switch 212 is formed. When the connection is disconnected, a closed loop of the capacitor 224 and the upper switch 211 is formed, and the power charged in the capacitor 224 is discharged and supplied as the driving power of the upper switch 211.

As shown in FIG. 16, even if the converter 210 is a boost converter (A) or a buck-boost converter (B), the driving power of the upper switch 211 is the first driving power 221 of the corresponding lower switch 212 and It can be supplied using the bootstrap circuit 222.

That is, in order to supply driving power to the upper switch 211 using the bootstrap circuit 222, the capacitor must be charged. Therefore, it is impossible to continuously conduct the upper switch without operating the lower switch, and the output voltage of the bootstrap must be maintained by conducting the lower switch even for a short time.

That is, the driving power of the upper switch 211 is dependent on the on/off operation of the corresponding lower switch 212 . If a sufficient time for the low side switch 212 to be turned on is not secured, a sufficient voltage level cannot be maintained because the power supplied through the bootstrap circuit 222 is less than the power consumed by the gate driver. In addition, the half-bridge structure does not turn on the upper switch 211 and the lower switch 212 at the same time to prevent a short-circuit that can cause circuit damage called a shoot-through condition. , Due to this, when the driving power of the upper switch 211 is generated using the bootstrap circuit 222, there is a restriction in continuously conducting the upper switch 211.

Therefore, in order for the converter 210 receiving driving power from the auxiliary power supply unit 220 including the bootstrap circuit 222 to operate in the input/output connection mode, the first period in which the upper switch 211 is conducting is maintained as long as possible. However, the second section in which the lower switch 212 is conducting must be included. Through this, the converter 210 provides the same output value as the input value in the first section, and charges the driving power of the upper switch 211 through the bootstrap circuit 222 in the second section.

The converter 210 may operate so that the ratio between the first section and the second section becomes a first ratio in the input/output connection mode. Here, in the first ratio, the first interval may be longer than the second interval. The first ratio may be set to a preset value according to the specifications of the converter 210 . Here, the ratio of the second section may be set to a minimum ratio for charging the capacitor 224 in order to supply driving power to the upper side switch 211 . For example, the second interval may be set to 1% and the first interval to 99%. Alternatively, it may be set to 0.1% of the second interval and 99.9% of the first interval.

Also, the first ratio between the first section and the second section may be variable. For example, when the mode is changed to suppress an inrush current generated in the bootstrap circuit 222, the ratio of the first section to the second section may be gradually increased or decreased.

A first ratio may be set such that a difference between a voltage of an input unit of the converter 210 and a voltage of an output unit of the converter 210 is equal to or less than a first threshold voltage value in the input/output connection mode. The first threshold voltage value may be preset or set by a user. The first threshold voltage value may be within an error range. The first ratio may be calculated and applied so that the difference between the voltages of the input unit and the output unit is within a preset error range. The first ratio may be calculated and set through simulation or calculation.

In the converter 210, the upper switch 211 and the lower switch 212 conduct complementary conduction at a first frequency in the power conversion mode, and the upper switch 211 and the lower switch 212 conduct in the input/output connection mode. may be conducted complementary to the second frequency.

A second frequency at which the first period and the second period are repeated in the input/output connection mode may be different from the first frequency that is the switching frequency of the switching element in the power conversion mode.

In the power conversion mode, it operates at a first frequency having a high frequency to reduce the ripple of voltage/current generated in the power conversion process or to reduce the size of passive elements such as inductors/transformers/capacitors. For example, the first frequency may use a frequency of 20 kHz or higher, which is higher than a human audible frequency.

On the other hand, in the input/output connection mode, there are few restrictions on voltage/current ripple and the size of passive elements. Therefore, there is no need to use a high frequency, and operation can be performed with a second frequency having a low frequency. As the second frequency is lowered, the frequency of switching loss occurring during the on-off process of the switching element decreases, so that an effect of increasing efficiency due to reduction in switching loss can be expected. In order to sufficiently secure a switching loss reduction effect, the second frequency may be 1/4 times or less than the first frequency. For example, the first frequency may be 20 kHz to 100 kHz, and the second frequency may be 0.001 Hz to 10 kHz or less.

Here, the second frequency may be set according to the input/output voltage, current, and temperature of the converter. In addition, a jittering function may be used to reduce electromagnetically generated noise, and a frequency other than 20 to 20 kHz may be used as the second frequency to avoid audible frequencies.

As shown in FIG. 17, in the input/output connection mode (A), the first period conducting the upper switch 211 operates longer than the second period conducting the lower switch 212, and the first period and the second period are repeated. The second frequency may operate lower than the first frequency of the power conversion mode (B). Also, it can be seen that the ratio of the first section is longer in the input/output connection mode (A) than in the power conversion mode (B). In this way, by operating differently according to the operating mode, the converter 210 can operate in multiple operating modes.

18 is a block diagram of a power conversion device in which a plurality of power circuits are configured in multi-levels according to an embodiment of the present invention, and FIGS. 19 to 21 are diagrams for explaining the power conversion device according to the embodiment of FIG. 18 .

A detailed description of each of the power circuits 310 to 330 of the power converter 300 in which the plurality of power circuits 310 to 330 are composed of multi-levels is the power converter 100 of FIGS. 2 to 11 and FIG. 12 to the power conversion device 200 of FIG. 17, a redundant description thereof will be omitted.

The plurality of power circuits 310 to 330 are multi-level, and may be individually connected to cell strings constituting a photovoltaic module. Each power circuit may be module-level power electronics (MLPE). As shown in FIG. 19, the power converter may be connected to other power converters in a multi-level manner and output power to an inverter or a load.

The plurality of power circuits 310 to 330 may be connected in a cascode to form a multilevel. Here, the cascode refers to a form in which output stages are connected in multiple stages, and output stages of the power circuit are piled up according to the cascode connection to form multi-levels. Multi-level refers to a structure in which the output signals of each power circuit are combined and output as one signal. At this time, the (-) terminal of the output terminal of the power circuit of the upper level is sequentially connected to the (+) terminal of the output terminal of the power circuit of the neighboring lower level, and the output of the power circuit of the highest level to the output of the power circuit of the lowest level is combined output as a single signal.

In addition, as shown in FIG. 20, a plurality of power circuits may be connected to a plurality of pairs of output terminals of one photovoltaic panel to configure multi-levels. At this time, input terminals input to the power conversion device 300 may be a plurality of pairs, but output terminals may be a single pair according to the connection of a multi-level power circuit.

Each power circuit (310 to 330) includes a power conversion unit, an input/output connection unit, and a bypass unit and operates in multiple operation modes of power conversion mode, input/output connection mode, and bypass mode, or power conversion mode, input/output connection mode, and a converter operating in a bypass mode. The operation mode of each of the power circuits 310 to 330 may have an independently determined mode, or all may operate in the same mode in some cases.

A multi-level bypass unit 340 generating a bypass path bypassing the entirety of the plurality of power circuits 310 to 330 at the multi-level output stage may be included. Instead of individually bypassing each of the power circuits 310 to 330, the multi-level bypass unit 340 creates a path bypassing all of the plurality of power circuits constituting the multi-level.

In addition, a multi-level monitoring unit for monitoring output terminals of the entire plurality of power circuits as well as individual monitoring units for monitoring input and output terminals of the plurality of power circuits may be included.

In addition, as shown in FIG. 21 , an auxiliary power unit for supplying driving power to the plurality of power circuits 310 to 330 may be included. At this time, each of the power circuits 310 to 330 includes a converter including at least one upper switch and at least one lower switch, and the driving power supplied to each power circuit 310 to 330 is the driving power of the lower switch. , driving power can be supplied to the upper switch using the bootstrap circuit.

Each of the power circuits 310 to 330 may be configured as a buck converter, and functions of a power conversion mode, an input/output connection mode, and a bypass mode may be implemented by the buck converter. A driving circuit is connected to each switching element included in the converter, and the driving circuit controls a conduction state of the switching element. The driving power of the lower switch is supplied through an auxiliary power circuit, and the driving power of the upper switch is generated through a bootstrap circuit. When the power circuit is operated in the input/output connection mode, it may include a first section in which the upper switch is conducted for a long time and a second section in which the lower switch is conducted for a short time. In this case, the second frequency repeating the first period and the second period may be lower than the first frequency, which is a switching frequency in the power conversion mode.

Those skilled in the art related to this embodiment will be able to understand that it can be implemented in a modified form within a range that does not deviate from the essential characteristics of the above description. Therefore, the disclosed methods are to be considered in an illustrative rather than a limiting sense. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the equivalent scope will be construed as being included in the present invention.

Claims (15)

a converter comprising at least one high-side switch and at least one low-side switch; and
An auxiliary power unit supplying driving power to the upper switch and the lower switch,
The auxiliary power unit,
and a bootstrap circuit supplying driving power to the upper switch using first driving power supplying driving power to the lower switch. According to claim 1,
The bootstrap circuit,
a capacitor charged by receiving power from the first driving power source; and
A diode connected between the first driving power source and the capacitor;
the capacitor,
connected to a node between the upper switch and the lower switch;
When the lower switch is turned on, a closed loop connected to the first driving power source, the diode, the capacitor, and the lower switch is formed to receive power from the first driving power source and charge;
When the lower switch is turned off, the power converter receives power from the first driving power source and supplies the charged power to the driving power source of the upper switch. According to claim 1,
The converter is
Operates in a first mode in which the upper switch and the lower switch are complementaryly conducted at a first frequency, or in a second mode in which the upper switch and the lower switch are complementaryly conducted at a second frequency;
The first frequency is different from the second frequency. According to claim 3,
The second frequency is less than the first frequency power converter. According to claim 3,
The second frequency is 1/4 or less of the first frequency. According to claim 3,
The first frequency is 20 kHz or more. According to claim 3,
The second frequency is set according to the input/output voltage, current, and temperature of the converter. According to claim 3,
A first period in which the upper switch conducts and a second period in which the lower switch conducts,
The converter is
In the second mode, the ratio between the first section and the second section is operated to be a first ratio;
The first ratio is a power conversion device in which the first section is longer than the second section. According to claim 8,
The converter is
When the mode is changed, the power conversion device gradually changes the ratio of the first section and the second section. According to claim 3,
In the second mode, the difference between the voltage of the input unit of the converter and the voltage of the output unit of the converter is equal to or less than a first threshold voltage value. According to claim 1,
The converter is
Operating in a third mode in which the lower switch is connected for a first period or more;
When the upper switch is connected between the lower switch and the output (+) terminal, the upper switch is simultaneously connected to the lower switch for more than the first cycle in the third mode. According to claim 11,
the converter includes at least one of a buck converter, a boost converter, and a buck boost converter;
In the third mode,
The buck converter has only a low switch connected, the boost converter has both an upper switch and a low switch connected, and the buck boost converter has both an output high switch and a low switch connected. According to claim 1,
an input unit receiving a first voltage; and
An output unit for outputting an output voltage of the converter,
The converter is
Operating in a first mode for converting the first voltage into a second voltage or a second mode for outputting the first voltage to the output unit;
the output unit,
The power conversion device for outputting the second voltage in the first mode and outputting the first voltage in the second mode. According to claim 13,
The converter operates in a third mode for generating a bypass path in the output unit,
The output unit outputs a third voltage input from an output side in the third mode. Including a plurality of power circuits constituting a multi-level,
A multi-level power converter comprising the power converter according to any one of claims 1 to 14 in each of the power circuits.

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