Power conversion circuit of inverter device, inverter device, and grid-connected operation method thereof

Abstract

The present specification relates to one embodiment of a power conversion circuit, an inverter device, and a grid-connected operation method thereof, the circuit including changeover switches provided at an N-phase terminal and between L2 phase-N phase through which there is output from an inverter to a load, so that an N-phase switching unit is connected to an L2 phase during operation in connection with a grid, and thus the N-phase switching unit and an L2 phase switching unit are alternately operated and a power source is alternately output to the L2 phase.

Description

Power conversion circuit of inverter device, inverter device and grid-connected operation method thereof

[0001] The present invention relates to a power conversion circuit that converts supplied power into alternating current power, an inverter device including the same, and a grid-connected operation method thereof.

[0002] The technology that forms the background of the present invention relates to a power conversion circuit of an inverter device used in an ESS (Energy Storage System).

[0003] Typically, ESS is installed and operated to share peak power consumption, charging when load power consumption is low and discharging when it is high, and to reduce ripple power generated by renewable energy generation. When connected to the grid, ESS receives power from the grid to charge batteries or shares the power consumed by loads during peak loads. Furthermore, ESS is required to function as a distributed power source, independently supplying power to loads in the event of a grid failure (power outage) upon user request. This independent operation function is being applied not only as a replacement for emergency generators but also as a solution for establishing microgrids in isolated areas.

[0004] For residential ESS, single-phase products are the mainstream, except in countries where three-phase outlets are widely available. Topologies commonly used in single-phase ESS include H-Bridge, Totem-pole, and HERIC. As shown in Figure 1, residential ESS customers want to be able to use both 220V and 110V loads in their homes during a power outage. Therefore, ESS developers and manufacturers often configure their products with the Totem-pole topology, which simplifies the implementation of split-phase functionality.

[0005] Figure 1 illustrates a previously proposed single-phase split-phase totem-pole topology circuit. Totem-pole power supplies can generate 220 V AC between phases L1 and L2 and 110 V AC between phases N and L2 during standalone operation. Furthermore, the N phase is often left unused during grid connection, as grid connection via only phase L1 allows for higher power control with lower current. Therefore, the N phase is often designed to be disconnected from the grid during grid connection and connected to phase L1 of the product, allowing for increased capacity.

[0006] Recently, many products have been developed in the residential ESS field that connect PV control to the DC link via a DC-DC converter. However, these DC-coupled ESS systems present challenges in commercializing the totem-pole topology. As PV capacity increases, parasitic capacitance inevitably increases, and the totem-pole topology has sections where the common mode voltage (CMV) across the parasitic capacitor rapidly changes, resulting in increased leakage current.

[0007] FIG. 2, FIG. 3a, and FIG. 3b are graphs and equivalent circuits representing the mechanism by which leakage current occurs in the conventional totem-pole topology. As shown in FIG. 3a and FIG. 3b, the totem-pole topology has L1 performing PWM control and L2 operating in the same manner as the system frequency. Among these, the phase that affects the CMV is L2. At the moment of transition from ① → ② in FIG. 2, the CMV quickly transitions from 0 V to -Vdc voltage, and at this time, the leakage current occurs in proportion to the parasitic capacitance and the rate of change of the voltage. Similarly, in ② → ① in FIG. 2, the CMV quickly transitions from -Vdc to 0 V voltage and generates a peak leakage current. If the parasitic capacitance is small, this leakage current can be ignored, but if the parasitic capacitance of the system is unintentionally increased, such as through PV connection, a leakage current exceeding the specification may occur.

[0008] That is, when implementing a single-phase, two-wire system when connecting to a grid using an existing inverter circuit, there was a limitation that the operation of the inverter and power supply became unstable due to the occurrence of leakage current, etc.

[0009] The present invention aims to improve the limitations of the prior art as described above.

[0010] Accordingly, this specification aims to provide an embodiment in which a single-phase, 3-wire inverter can supply a single-phase, 2-wire power.

[0011] In addition, we aim to provide an embodiment that can reduce leakage current when operating in conjunction with a system.

[0012] In addition, the present invention aims to provide an embodiment in which the operation of a power conversion circuit can be stably performed when operated in conjunction with a system.

[0013] The present invention, which aims to solve the above-described problem, provides a means of solving the problem by switching the connection between the inverter and the load terminal to enable a single-phase, two-wire power supply.

[0014] Specifically, when operating in conjunction with the system, the switching unit of the N phase is connected to the L2 phase, and the switching unit of the N phase and the switching unit of the L2 phase operate alternately and output power alternately to the L2 phase.

[0015] Accordingly, single-phase 2-wire power supply can be achieved with a single-phase 3-wire inverter, making it easy to respond to grid-connected operation conversion.

[0016] The above technical features can be applied and implemented to rectifier circuits, power conversion circuits, converter circuits, inverter circuits, power conversion devices, inverter devices, ESS (Energy Storage System) devices, emergency power devices, etc., and the present specification provides examples of power conversion circuits, inverter devices, and grid-connected operation methods thereof that use the above technical features as a means for solving problems.

[0017] An embodiment of a power conversion circuit of an inverter device using the above technical features as a means for solving a problem includes a link unit for storing DC power, a first conversion unit connected to an L1 phase of a supply target unit and converting the DC power into a first power by a switching operation of at least one pair of switching elements and outputting it to the L1 phase, a second conversion unit connected to an L2 phase of the supply target unit and converting the DC power into a second power by a switching operation of at least one pair of switching elements and outputting it to the L2 phase, and a third conversion unit connected to the L2 phase and an output terminal of the second conversion unit and converting the DC power into a third power by a switching operation of at least one pair of switching elements and outputting it to the L2 phase, wherein the second conversion unit and the third conversion unit alternately output the second power and the third power to the L2 phase.

[0018] The above power conversion circuit may be implemented in an embodiment in which the power supply method is changed from a single-phase, three-wire system to a single-phase, two-wire system.

[0019] In addition, an embodiment of an inverter device using the above technical features as a means for solving a problem includes a link unit storing DC power, a conversion unit including at least three pairs of switching elements, and converting the DC power received from the link unit into power to be supplied to a supply target unit through a switching operation of the three pairs of switching elements, a switching unit switching a connection between the conversion unit and the supply target unit according to an operation method of the inverter device, and a control unit controlling the conversion unit by applying a control signal for controlling a switching operation to the three pairs of switching elements according to the operation method, and controlling the conversion unit by applying a switching signal to the switching unit.

[0020] In an embodiment of the inverter device, the conversion unit includes a first conversion unit that converts the DC power into a first power and outputs it to a first load terminal of the supply target unit, a second conversion unit that converts the DC power into a second power and outputs it to a second or third load terminal of the supply target unit, and a third conversion unit that converts the DC power into a third power and outputs it to the third load terminal, and the conversion unit includes a first conversion unit that connects or disconnects between an output terminal of the second conversion unit and an output terminal of the third conversion unit, and a second conversion unit that connects or disconnects between an output terminal of the second conversion unit and the second load terminal.

[0021] In an embodiment of the inverter device, when the driving method is a linked operation that operates in conjunction with the system, the control unit controls each of the first and second conversion units so that the output terminal of the second conversion unit is separated from the second load terminal and connected to the output terminal of the third conversion unit, and controls the conversion unit so that the second power source and the third power source are output alternately to the third load terminal.

[0022] Meanwhile, an embodiment of a grid-connected operation method of an inverter device using the above technical features as a means for solving a problem is a method for operating an inverter device, including a link unit storing DC power, a first conversion unit connected to an L1 phase of a supply target unit and converting the DC power into a first power by a switching operation of at least one pair of switching elements and outputting it to the L1 phase, a second conversion unit connected to an L2 phase of the supply target unit and converting the DC power into a second power by a switching operation of at least one pair of switching elements and outputting it to the L2 phase, and a third conversion unit connected to an output terminal of the L2 phase and the second conversion unit and converting the DC power into a third power by a switching operation of at least one pair of switching elements and outputting it to the L2 phase, comprising: a step of operating the first conversion unit and the second conversion unit so that the line voltage between the L1 phase and the L2 phase increases from 0 to a predetermined positive voltage; a step of operating the lower switching elements of the first conversion unit and the third conversion unit so that the line voltage increases from the predetermined positive voltage and then decreases to 0; a step of operating the first conversion unit and the second conversion unit so that the It includes a step of decreasing the line voltage from 0 to a constant negative voltage and a step of operating the upper switching elements of the first conversion unit and the third conversion unit so that the line voltage decreases from the constant negative voltage and then increases to 0.

[0023] The embodiments of the power conversion circuit, inverter device and grid-connected operation method thereof as described above are not limited to the above, and may include embodiments described in the specific description to be described below or embodiments that can be inferred / derived from the specific description.

[0024] The power conversion circuit, inverter device and grid-connected operation method thereof according to the embodiment have the effect that, when operated in connection with the grid, the switching unit of the N phase is connected to the L2 phase, the switching unit of the N phase and the switching unit of the L2 phase operate alternately and output power alternately to the L2 phase, thereby enabling a single-phase, two-wire power supply to be achieved with a single-phase, three-wire inverter.

[0025] Accordingly, there is an effect that single-phase 2-wire and single-phase 3-wire operation can be performed with a single inverter circuit.

[0026] In addition, there is an effect that allows for linked operation, which is operated in conjunction with the system, and independent operation, which is operated separately from the system, with a simple circuit configuration.

[0027] In addition, since inductance and capacitance are formed at each output terminal during linked operation, there is an effect of reducing leakage current.

[0028] In addition, by controlling the switching operation of each switching unit in response to linked operation, there is an effect that enables power conversion and stable power supply of the inverter.

[0029] The effects according to the embodiment of the power conversion circuit, inverter device and system-connected operation method thereof described above are not limited to those described above, and may also include effects described in the specific description to be described below or effects that can be inferred / derived from the specific description.

[0030] Figure 1 is a circuit diagram of a conventional single-phase split phase totem-pole topology.

[0031] Fig. 2 is a graph showing the voltage change and resulting leakage current of the topology illustrated in Fig. 1.

[0032] Fig. 3a is a circuit diagram showing an equivalent circuit of one section of the graph shown in Fig. 2.

[0033] Fig. 3b is a circuit diagram showing an equivalent circuit of two sections of the graph shown in Fig. 2.

[0034] Fig. 4 is a configuration diagram of a power conversion circuit and inverter device according to an embodiment.

[0035] Fig. 5 is a circuit diagram of a power conversion circuit according to an embodiment.

[0036] Fig. 6 is a circuit diagram showing an example of a modification of a power conversion circuit according to an embodiment.

[0037] Fig. 7 is an exemplary diagram showing the linked operation of a power conversion circuit according to an embodiment.

[0038] Figure 8 is a simplified example of the example shown in Figure 7.

[0039] Fig. 9 is a graph showing the control concept of the conversion unit during linked operation of the power conversion circuit according to the embodiment.

[0040] Fig. 10 is a graph showing voltage changes and resulting leakage current in a power conversion circuit according to an embodiment.

[0041] Fig. 11a is a circuit diagram showing an equivalent circuit of one section of the graph shown in Fig. 10.

[0042] Fig. 11b is a circuit diagram showing an equivalent circuit of two sections of the graph shown in Fig. 10.

[0043] Fig. 11c is a circuit diagram showing an equivalent circuit of three sections of the graph shown in Fig. 10.

[0044] Fig. 11d is a circuit diagram showing an equivalent circuit of four sections of the graph shown in Fig. 10.

[0045] Fig. 12 is a flowchart of a grid-connected operation method of an inverter device according to an embodiment.

[0046] Hereinafter, embodiments disclosed in this specification will be described in detail with reference to the attached drawings. Regardless of the drawing numbers, identical or similar components are given the same reference numbers and redundant descriptions thereof are omitted. In addition, when describing embodiments disclosed in this specification, if it is determined that a specific description of a related known technology may obscure the gist of the embodiments disclosed in this specification, a detailed description thereof is omitted.

[0047] The power conversion circuit according to the embodiment (hereinafter referred to as the conversion circuit) means a power conversion module included in an inverter device that converts power.

[0048] Here, the inverter device may be an inverter used in a power supply device, a power control device, an emergency power device, a distributed power device, a renewable energy generation device, or an ESS (Energy Storage System).

[0049] The above conversion circuit may be a circuit included in the inverter device that converts power supplied from an external power source into AC power and outputs it to a supply target.

[0050] The above conversion circuit may be a circuit that includes a plurality of circuit elements and converts power through the plurality of circuit elements.

[0051] The above conversion circuit can be mounted on one substrate.

[0052] The above conversion circuit (100), as illustrated in FIG. 4, is a circuit included in an inverter device (1000) that converts power supplied from an external power supply source (P) into power to be supplied to a supply target portion (L) and supplies the converted power to the supply target portion (L), and includes a link portion (10), a conversion portion (20), and a switching portion (30).

[0053] The conversion circuit (100) including the link section (10), the conversion section (20) and the switching section (30) may correspond to the inverter section in the inverter device (1000).

[0054] Here, the power supply source (P) may be a battery or a source that supplies direct current power, and the supply target unit (L) may be a load of the inverter device (1000).

[0055] The above conversion circuit (100) may also further include a rectifier that rectifies the power supplied from the power supply source (P).

[0056] Each of the above link unit (10), the conversion unit (20), and the switching unit (30) may include one or more circuit elements.

[0057] For example, the link unit (10) may include a capacitor, the conversion unit (20) may include a switching element, and the switching unit (30) may include a switching switch.

[0058] The specific circuit configuration of the above conversion circuit (100) may be as shown in FIG. 5.

[0059] The above conversion circuit (100) includes the conversion unit (20) including the link unit (10) that stores DC power, as shown in FIGS. 4 and 5, the first conversion unit (21) that converts the DC power into a first power and outputs it to the first load terminal (L1) of the supply target unit (L), the second conversion unit (22) that converts the DC power into a second power and outputs it to the second load terminal (N) or the third load terminal (L2) of the supply target unit (L), and the third conversion unit (23) that converts the DC power into a third power and outputs it to the third load terminal (L2).

[0060] Here, the conversion unit (20) may further include a capacitor unit (24) disposed between the output terminal of the third conversion unit (23) and the lower end of the lower arm switching element (S6) of the third conversion unit (23), including an element having a certain capacitance component.

[0061] The above conversion circuit (100) may also include the conversion unit (30) including the first conversion unit (31) that connects or disconnects between the output terminal of the second conversion unit (22) and the output terminal of the third conversion unit (23) and the second conversion unit (32) that connects or disconnects between the output terminal of the second conversion unit (22) and the second load terminal (N).

[0062] Here, the switching unit (30) may further include a third switching unit (33) that connects or disconnects between the output terminal of the third conversion unit (23) and the capacitor unit (24).

[0063] In the above conversion circuit (100), the first switching unit (31) and the second switching unit (32) operate differently depending on whether they are connected to the system.

[0064] That is, the conversion circuit (100) can be operated by switching the connection with the supply target unit (L) by having the first switching unit (31) and the second switching unit (32) operate differently depending on whether or not they are connected to the system.

[0065] For example, when operating in conjunction with the system, the first switching unit (31) may operate ON, and when operating in isolation from the system, the first switching unit (31) may operate OFF.

[0066] In addition, when operating in conjunction with the system, the second switching unit (32) may operate OFF, and when operating separately from the system, the second switching unit (32) may operate ON.

[0067] Meanwhile, the third switching unit (33) can operate ON when operating in conjunction with the system, and OFF when operating separately from the system.

[0068] The above link unit (10) includes a DC link capacitor, and can smooth and store the power received from the power supply source (P) through the DC link capacitor, and transmit the stored DC power to the conversion unit (20).

[0069] In this case, the DC power can be transmitted to each of the first conversion unit (21) to the third conversion unit (23).

[0070] The above conversion unit (20) may include the first conversion unit (21) connected to the L1 phase of the supply target unit (L), the second conversion unit (22) connected to the N phase or L2 phase of the supply target unit (L), and the third conversion unit (23) connected to the L2 phase of the supply target unit (L).

[0071] Each of the first conversion unit (21) to the third conversion unit (23) includes a plurality of switching elements (S1-S2, S3-S4, S5-S6), and can convert the smooth power received from the link unit (10) into power to be supplied to the supply target unit (L) through the switching operation of the plurality of switching elements (S1-S2, S3-S4, S5-S6) and apply the converted power to the supply target unit (L).

[0072] Here, the switching module may be a switching element included in a power conversion means such as an IGBT, BJT, JFET, or MOSFET.

[0073] The above plurality of switching elements (S1 to S6) can be divided into at least three pairs and form the first conversion unit (21) to the third conversion unit (23), respectively.

[0074] That is, each of the first conversion unit (21) to the third conversion unit (23) may include at least one pair of switching elements (S1-S2, S3-S4, S5-S6).

[0075] Meanwhile, one or more of the first conversion unit (21) to the third conversion unit (23) may include two pairs of switching modules (S1-1-S2-1, S2-1-S2-2), as illustrated in FIG. 6.

[0076] That is, the above conversion unit (20) may be composed of four or more pairs of the plurality of switching elements (S1-S6).

[0077] In this case, as shown in Fig. 6, two pairs of switching elements (S1-1-S2-1, S2-1-S2-2) are included in one converter (21), so that each output terminal can be connected in parallel to output one phase power.

[0078] Each of the first conversion unit (21) to the third conversion unit (23) can convert power of one of the three phases.

[0079] For example, the first conversion unit (21) can convert the first power corresponding to the L1 phase of the supply target unit (L), the second conversion unit (22) can convert the second power corresponding to the N phase of the supply target unit (L), and the third conversion unit (23) can convert the third power corresponding to the L2 phase of the supply target unit (L).

[0080] The first conversion unit (21) to the third conversion unit (23) can convert the DC power into a supply power by performing a switching operation according to an authorized control signal.

[0081] Here, the control signal may include a PWM control signal.

[0082] These control signals may be signals that are applied to each of the switching elements (S1-S2, S3-S4, S5-S6) included in the first conversion unit (21) to the third conversion unit (23) to control the switching operation of the switching elements (S1-S2, S3-S4, S5-S6).

[0083] The above first conversion unit (21) can be connected to the first load unit (L1) whose output terminal corresponds to the L1 phase of the supply target unit (L).

[0084] The output terminal of the first converter (21) may include one or more elements (21I) having an inductance component.

[0085] That is, the output terminal of the first conversion unit (21) can form a constant inductance corresponding to the element (21I).

[0086] The above element (21I) can be placed at the front end of the first load stage (L1).

[0087] By including one or more of the above elements (21I) in this way, the leakage current of the power output from the first converter (21) can be improved.

[0088] The output terminal of the first converter (21) may also include one or more capacitors or resistors.

[0089] The second conversion unit (22) can be connected to the second load unit (N) whose output terminal corresponds to the N phase of the supply target unit (L) or the third load unit (L2) corresponding to the L2 phase of the supply target unit (L).

[0090] The output terminal of the second converter (22) may include one or more elements (22I) having an inductance component.

[0091] That is, the output terminal of the second converter (22) can form a constant inductance corresponding to the element (22I).

[0092] The above element (22I) can be placed at one end of the first switching unit (31).

[0093] Here, one end of the first conversion unit (31) may be a contact point where the output terminal of the second conversion unit (22) and the first conversion unit (31) are connected.

[0094] Accordingly, inductance can be formed at the output terminal of the second conversion unit (22) regardless of whether the first conversion unit (31) is opened or closed.

[0095] By including one or more of the above elements (22I) in this way, the leakage current of the power output from the second converter (22) can be improved.

[0096] The output terminal of the second converter (22) may also include one or more capacitors or resistors.

[0097] The third conversion unit (23) can be connected to the third load unit (L2) whose output terminal corresponds to the L2 phase of the supply target unit (L).

[0098] The output terminal of the third conversion unit (23) can be formed to have a smaller inductance component than the first conversion unit (21) and the second conversion unit (22).

[0099] That is, the output terminal of the third converter (23) may not include an element having an inductance component.

[0100] The above switching unit (30) may include the first switching unit (31) that connects or disconnects between the second switching unit (22) and the third switching unit (23), the second switching unit (32) that connects or disconnects between the second switching unit (22) and the second load terminal (N), and the third switching unit (33) that connects or disconnects between the output terminal of the third switching unit (23) and the capacitor unit (24).

[0101] The first switching unit (31), the second switching unit (32), and the third switching unit (33) may be switches that switch between opening and closing by operating ON / OFF.

[0102] The first switching unit (31), the second switching unit (32), and the third switching unit (33) may be switches that connect or disconnect two contact points by switching the ON / OFF operation.

[0103] The first switching unit (31), the second switching unit (32), and the third switching unit (33) may be mechanical switches or electronic switches.

[0104] For example, it can be a POWER relay, MOSFET, IGBT, BJT, JFET, MAGNETIC CONTACTOR, or MCCB.

[0105] The first switching unit (31), the second switching unit (32), and the third switching unit (33) may be A-contact switches that are closed when in the ON operation and open when in the OFF operation.

[0106] In addition, the first switching unit (31), the second switching unit (32), and the third switching unit (33) may be B-contact switches that are closed when in the OFF operation and open when in the ON operation.

[0107] Hereinafter, for convenience of explanation, the first switching unit (31), the second switching unit (32), and the third switching unit (33) are described with an example in which the first switching unit (31), the second switching unit (32), and the third switching unit (33) are A-point switches. However, a specific embodiment of the conversion circuit (100) is based on the premise that the first switching unit (31), the second switching unit (32), and the third switching unit (33) may be configured as B-point switches. In this case, whether the first switching unit (31), the second switching unit (32), and the third switching unit (33) are opened or closed can be interpreted in reverse.

[0108] The first switching unit (31) and the second switching unit (32) can operate differently from each other.

[0109] The first switching unit (31) and the second switching unit (32) can operate in opposite directions to each other.

[0110] For example, if one operates ON, the other may operate OFF.

[0111] Accordingly, the first switching unit (31) and the second switching unit (32) can operate as an interlock.

[0112] Additionally, the first switching unit (31) and the third switching unit (33) can operate in the same manner.

[0113] Accordingly, the second switching unit (32) and the third switching unit (33) can operate differently from each other.

[0114] The above first switching unit (31) and the above second switching unit (32) can operate differently depending on whether or not they are connected to the conversion circuit (100) and the system.

[0115] The above first conversion unit (31) can be placed between the output terminal of the second conversion unit (22) and one end of the second conversion unit (32).

[0116] Here, one end of the second switching unit (32) may be connected to the output terminal of the second conversion unit (22).

[0117] Accordingly, the first switching unit (31) can connect or disconnect the output terminal of the second switching unit (22) and the output terminal of the third switching unit (23) regardless of whether the second switching unit (32) is opened or closed.

[0118] The above first switching unit (31) can be closed when in the ON operation and opened when in the OFF operation.

[0119] The above first conversion unit (31) can connect between the output terminal of the second conversion unit (22) and the output terminal of the third conversion unit (23) when the conversion circuit (100) is operated in conjunction with the system.

[0120] The above first conversion unit (31) is turned ON and closed when the conversion circuit (100) is operated in conjunction with the system, thereby connecting the output terminal of the second conversion unit (22) and the output terminal of the third conversion unit (23).

[0121] That is, when the above conversion circuit (100) is operated in conjunction with the system, the first conversion unit (31) is turned ON so that the output terminal of the second conversion unit (22) and the output terminal of the third conversion unit (23) can be connected.

[0122] In this case, the second switching unit (32) may operate in an OFF state opposite to the first switching unit (31) to separate the output terminal of the second conversion unit (22) and the second load terminal (N).

[0123] The above first conversion unit (31) can separate the output terminal of the second conversion unit (22) and the output terminal of the third conversion unit (23) when the conversion circuit (100) is operated separately from the system.

[0124] The above first conversion unit (31) is opened by being turned OFF when the conversion circuit (100) is operated separately from the system, thereby separating the output terminal of the second conversion unit (22) and the output terminal of the third conversion unit (23).

[0125] That is, when the conversion circuit (100) is operated separately from the system, the first switching unit (31) may be turned OFF to separate the output terminal of the second conversion unit (22) and the output terminal of the third conversion unit (23).

[0126] In this case, the second switching unit (32) may operate in an ON state opposite to the first switching unit (31) to connect the output terminal of the second conversion unit (22) and the second load terminal (N).

[0127] The second switching unit (32) can be placed between one end of the first switching unit (31) and the second load end (N).

[0128] Here, one end of the first conversion unit (31) may be connected to the output terminal of the second conversion unit (22).

[0129] Accordingly, the second switching unit (32) can connect or disconnect the output terminal of the second conversion unit (22) and the second load terminal (N) depending on whether the first switching unit (31) is opened or closed.

[0130] The above second switching unit (32) can be closed when in the ON operation and opened when in the OFF operation.

[0131] The second conversion unit (32) can separate the output terminal of the second conversion unit (22) and the second load terminal (N) when the conversion circuit (100) is operated in conjunction with the system.

[0132] The second switching unit (32) can be opened by turning OFF when the conversion circuit (100) is operated in conjunction with the system, thereby separating the output terminal of the second conversion unit (22) and the second load terminal (N).

[0133] That is, when the conversion circuit (100) is operated in conjunction with the system, the second switching unit (32) may be turned OFF to separate the output terminal of the second conversion unit (22) and the second load terminal (N).

[0134] In this case, the first switching unit (31) may operate in an ON state opposite to the second switching unit (32) to connect the output terminal of the second switching unit (22) and the output terminal of the third switching unit (23).

[0135] The second conversion unit (32) can connect the output terminal of the second conversion unit (22) and the second load terminal (N) when the conversion circuit (100) is operated separately from the system.

[0136] The second switching unit (32) can be connected between the output terminal of the second switching unit (22) and the second load terminal (N) by being turned ON and closed when the conversion circuit (100) is operated separately from the system.

[0137] That is, when the conversion circuit (100) is operated separately from the system, the second switching unit (31) is turned ON so that the output terminal of the second conversion unit (22) and the second load terminal (N) can be connected.

[0138] In this case, the first switching unit (31) may operate in an OFF state opposite to the second switching unit (32) to separate the output terminal of the second switching unit (22) and the output terminal of the third switching unit (23).

[0139] In addition, the third switching unit (33) can operate differently depending on whether it is connected to the conversion circuit (100) and the system.

[0140] The third conversion unit (33) may be placed between the output terminal of the third conversion unit (23) and one end of the capacitor unit (24).

[0141] The above third switching unit (33) can be closed when in ON operation and opened when in OFF operation.

[0142] The third conversion unit (33) can connect the output terminal of the third conversion unit (23) and the capacitor unit (24) when the conversion circuit (100) is operated in conjunction with the system.

[0143] The third switching unit (33) is turned ON and closed when the conversion circuit (100) is operated in conjunction with the system, thereby connecting the output terminal of the third conversion unit (23) and one end of the capacitor unit (24).

[0144] That is, when the above conversion circuit (100) is operated in conjunction with the system, the first switching unit (31) is turned ON so that the output terminal of the third conversion unit (23) and one end of the capacitor unit (24) can be connected.

[0145] The third conversion unit (33) can separate the output terminal of the third conversion unit (23) and one end of the capacitor unit (24) when the conversion circuit (100) is operated separately from the system.

[0146] The third switching unit (33) is turned OFF and opened when the conversion circuit (100) is operated separately from the system, thereby separating the output terminal of the third conversion unit (23) and one end of the capacitor unit (24).

[0147] That is, when the conversion circuit (100) is operated separately from the system, the third switching unit (33) is turned OFF, so that the output terminal of the third conversion unit (23) and one end of the capacitor unit (24) can be separated.

[0148] In this way, when the conversion circuit (100) is operated separately from the system, as shown in FIG. 5, the first conversion unit (31) may be turned OFF to separate the output terminal of the second conversion unit (22) and the output terminal of the third conversion unit (23), the second conversion unit (32) may be turned ON to connect the output terminal of the second conversion unit (23) and the second load terminal (N), and the third conversion unit (33) may be turned OFF to separate the output terminal of the third conversion unit (23) and one end of the capacitor unit (24).

[0149] Accordingly, the power output from the second conversion unit (22) is induced to the second load stage (N) through the element (22I) and the second conversion unit (32), so that power can be supplied to the first load stage (L1), the second load stage (N), and the third load stage (L2).

[0150] Accordingly, when the above-mentioned conversion circuit (100) is operated separately from the system, single-phase, three-wire operation can be performed by operating the first load stage (L1), the second load stage (N), and the third load stage (L2).

[0151] In this case, the load can be driven by being connected to the first load stage (L1) and the second load stage (N), the second load stage (N) and the third load stage (L2), or the first load stage (L1) and the third load stage (L2).

[0152] Meanwhile, the voltage between the first load stage (L1) and the third load stage (L2) may correspond to 1.8 to 2.2 times the voltage between either the first load stage (L1) or the third load stage (L2) and the second load stage (N).

[0153] For example, if the voltage between one of the first load stage (L1) and the third load stage (L2) and the second load stage (N) is 110 V, the voltage between the first load stage (L1) and the third load stage (L2) may be 220 V.

[0154] That is, when the above conversion circuit (100) is operated in conjunction with the system, power can be supplied to a 110 V load and a 220 V load in a single-phase, three-wire manner.

[0155] Accordingly, in the case where the system is connected to the system and the system is operated while bearing a load of 110 V, and the system is operated separately from the system due to an abnormality in the system, the conversion circuit (100) may be converted to a single-phase, three-wire system and bear a load of 110 V.

[0156] In addition, when the conversion circuit (100) is operated in conjunction with the system, as shown in FIG. 7, the first conversion unit (31) may be turned ON to connect the output terminal of the second conversion unit (22) and the output terminal of the third conversion unit (23), the second conversion unit (32) may be turned OFF to separate the output terminal of the second conversion unit (23) and the second load terminal (N), and the third conversion unit (33) may be turned ON to connect the output terminal of the third conversion unit (23) and one end of the capacitor unit (24).

[0157] Accordingly, the power output from the second conversion unit (22) is induced to the output terminal of the third conversion unit (23) through the element (22I) and the first conversion unit (31), and power is not induced to the second load unit (N), so that power can be supplied to the first load unit (L1) and the third load unit (L2).

[0158] Accordingly, when the above-mentioned conversion circuit (100) is operated in conjunction with the system, single-phase, two-wire operation can be performed by operating the first load stage (L1) and the third load stage (L2).

[0159] In this case, the load can be driven by being connected to the first load stage (L1) and the third load stage (L2) and supplied with power.

[0160] Meanwhile, the voltage between the first load stage (L1) and the third load stage (L2) may correspond to 1.8 to 2.2 times the voltage between either the first load stage (L1) or the third load stage (L2) and the second load stage (N).

[0161] For example, if the voltage between one of the first load stage (L1) and the third load stage (L2) and the second load stage (N) is 110 V, the voltage between the first load stage (L1) and the third load stage (L2) may be 220 V.

[0162] That is, when the above conversion circuit (100) is operated in conjunction with the system, power can be supplied to a 220 V load in a single-phase, two-wire manner.

[0163] In this way, the conversion circuit (100) can switch between single-phase two-wire and single-phase three-wire power supply by having the first conversion unit (31) and the second conversion unit (32) switch operations differently depending on whether or not they are connected to the system.

[0164] Accordingly, it becomes possible to selectively operate single-phase 2-wire and single-phase 3-wire in one inverter circuit, and with a simple circuit configuration, it becomes easy to switch between linked operation in which operation is performed in connection with the system and independent operation in which operation is performed separately from the system, and appropriate operation corresponding to each of the linked operation (single-phase 2-wire) and the independent operation (single-phase 3-wire) can be performed.

[0165] Below, a specific embodiment of the conversion circuit (100) when operated in conjunction with a system is described.

[0166] When the conversion circuit (100) is simplified to operate in conjunction with the system as illustrated in Fig. 7, it can be as illustrated in Fig. 8.

[0167] The above-described conversion circuit (100) that operates in conjunction with the system includes the link unit (10) that stores DC power, the first conversion unit (21) that is connected to the L1 phase and converts the DC power into the first power through a switching operation of at least one pair of switching elements (S1-S2) and outputs it to the L1 phase, the second conversion unit (22) that is connected to the L2 phase and converts the DC power into the second power through a switching operation of at least one pair of switching elements (S3-S4) and outputs it to the L2 phase, and the third conversion unit (23) that is connected to the L2 phase and an output terminal of the second conversion unit (22) and converts the DC power into the third power through a switching operation of at least one pair of switching elements (S5-S6) and outputs it to the L2 phase.

[0168] In the above conversion circuit (100), the second conversion unit (22) and the third conversion unit (23) alternately output the second power and the third power to the L2 phase.

[0169] That is, when operating in conjunction with the system, the second conversion unit (22) and the third conversion unit (23) can operate alternately.

[0170] For example, when the switching elements (S3-S4) of the second conversion unit (22) operate, the switching elements (S5-S6) of the third conversion unit (23) do not operate, so that the second power can be applied to the L2 phase, and when the switching elements (S3-S4) of the second conversion unit (22) do not operate, the switching elements (S5-S6) of the third conversion unit (23) operate, so that the third power can be applied to the L2 phase.

[0171] In the above first conversion unit (21), a certain inductance component can be formed between the output terminal and the L1 phase.

[0172] The above first conversion unit (21) may include an inductor having a certain inductance component between the output terminal and the L1 phase.

[0173] The second conversion unit (22) may have a constant inductance component formed between the output terminal and the output terminal of the third conversion unit (23).

[0174] The second conversion unit (22) may include an inductor having a certain inductance component between the output terminal and the output terminal of the third conversion unit (23).

[0175] In the third conversion unit (23), a certain capacitance component can be formed between the output terminal and the lower end of the lower arm switching element (S6).

[0176] The third conversion unit (23) may include a capacitor having a certain capacitance component between the output terminal and the lower end of the lower arm switching element (S6).

[0177] In this case, the capacitor may correspond to the capacitor section (24).

[0178] Meanwhile, the capacitor unit (24) can be connected to the output terminal of the third conversion unit (23) by the third conversion unit (33).

[0179] Accordingly, the power flowing through the L2 phase may be affected by the inductance formed at the output terminal of the second conversion unit (22) and the capacitance formed at the output terminal of the third conversion unit (23).

[0180] In this way, by connecting the capacitor unit (24) to the output terminal of the third converter unit (23), the leakage current can be reduced by the capacitance of the capacitor unit (24).

[0181] The principle of reducing leakage current is explained in more detail in the embodiment of the inverter device (1000) described below.

[0182] The second conversion unit (22) and the third conversion unit (23) may not operate when one of them operates.

[0183] Accordingly, the second conversion unit (22) and the third conversion unit (23) operate complementarily so that the second power and the third power can be output alternately on the L2 phase.

[0184] The second conversion unit (22) and the third conversion unit (23) can operate with different switching patterns.

[0185] For example, the second conversion unit (22) may operate in a pattern according to a PWM signal, and the third conversion unit (23) may operate in a pattern according to a turn-on / turn-off signal.

[0186] Meanwhile, the first conversion unit (21) can operate even when either the second conversion unit (22) or the third conversion unit (23) is not operating.

[0187] For example, when the second conversion unit (22) operates and the third conversion unit (23) does not operate and the second power is output to the L2 phase, and when the second conversion unit (22) does not operate and the third conversion unit (23) operates and the third power is output to the L2 phase, the first conversion unit (21) operates and the first power can be output to the L1 phase.

[0188] That is, the first conversion unit (21) can be operated continuously to output the first power to the L1 phase.

[0189] Accordingly, an AC voltage can be applied between the L1 phase and the L2 phase.

[0190] Meanwhile, the first conversion unit (21) to the third conversion unit (23) may be operated in a plurality of sections divided according to the voltage change between the L1 phase and the L2 phase.

[0191] Here, the plurality of sections may be sections that divide one cycle of voltage between the L1 phase and the L2 phase.

[0192] The above multiple sections can be divided into, for example, four sections.

[0193] In this case, the plurality of sections can be divided into two sections when the voltage between the L1 phase and the L2 phase corresponds to a positive voltage and two sections when the voltage between the L1 phase and the L2 phase corresponds to a negative voltage.

[0194] The above first conversion unit (21) can operate for one cycle of the voltage between the L1 phase and the L2 phase.

[0195] The above first conversion unit (21) can cause the upper arm switching element (S1) and the lower arm switching element (S2) to operate.

[0196] When the first conversion unit (21) operates in each of the plurality of sections, the switching elements (S1-S2) of the first conversion unit (21) may cause the upper arm switching element (S1) and the lower arm switching element (S2) to operate.

[0197] The second conversion unit (22) can operate in at least one of a section in which the voltage between the L1 phase and the L2 phase increases from 0 to a certain amount and a section in which the voltage decreases.

[0198] Preferably, the second conversion unit (22) can operate in each section in which the voltage between the L1 phase and the L2 phase increases by a certain amount from 0 and decreases.

[0199] In this case, the third conversion unit (23) may not operate in each section in which the voltage between the L1 phase and the L2 phase increases by a certain amount from 0 and decreases.

[0200] Accordingly, in a section where the voltage between the L1 phase and the L2 phase increases by a certain amount from 0 and a section where the voltage decreases, the second power may be output to the L2 phase, and the second power may not be output to the L2 phase.

[0201] The above second conversion unit (22) can cause the upper arm switching element (S3) and the lower arm switching element (S4) to operate.

[0202] When the second conversion unit (22) operates in each of the sections in which the voltage between the L1 phase and the L2 phase increases by a certain amount from 0 and decreases, the switching elements (S3-S4) of the second conversion unit (22) may operate as the upper-arm switching element (S3) and the lower-arm switching element (S4).

[0203] The third conversion unit (23) can operate in at least one of a section in which the voltage between the L1 phase and the L2 phase increases from a certain positive voltage and then decreases to 0, and a section in which the voltage between the L1 phase and the L2 phase decreases from a certain negative voltage and then increases to 0.

[0204] Preferably, the third converter (23) can operate in each of a section in which the voltage between the L1 phase and the L2 phase increases from a certain positive voltage and then decreases to 0, and a section in which the voltage between the L1 phase and the L2 phase decreases from a certain negative voltage and then increases to 0.

[0205] In this case, the second conversion unit (22) may not operate in each of a section in which the voltage between the L1 phase and the L2 phase increases from a certain positive voltage and then decreases to 0, and a section in which the voltage between the L1 phase and the L2 phase decreases from a certain negative voltage and then increases to 0.

[0206] Accordingly, in a section where the voltage between the L1 phase and the L2 phase increases from a certain positive voltage and then decreases to 0, and in a section where the voltage between the L1 phase and the L2 phase decreases from a certain negative voltage and then increases to 0, the third power source may be output to the L2 phase, and the second power source may not be output to the L2 phase.

[0207] The above third conversion unit (23) can operate either the upper arm switching element (S5) or the lower arm switching element (S6).

[0208] The third conversion unit (23) may operate the lower arm switching element (S6) during a period in which the voltage between the L1 phase and the L2 phase is +, and may operate the upper arm switching element (S5) during a period in which the voltage between the L1 phase and the L2 phase is -.

[0209] That is, in the third conversion unit (23), during a section in which the voltage between the L1 phase and the L2 phase increases from a certain positive voltage and then decreases to 0, the upper arm switching element (S5) may not operate and the lower arm switching element (S6) may operate, and during a section in which the voltage between the L1 phase and the L2 phase decreases from a certain negative voltage and then increases to 0, the upper arm switching element (S5) may operate and the lower arm switching element (S6) may not operate.

[0210] The specific operation of the above-described conversion unit (20) will be described in more detail in the description of the inverter device (1000) described below.

[0211] When operating in conjunction with the system in this way, the conversion circuit (100) in which the second conversion unit (22) and the third conversion unit (23) are connected to the L2 phase is included in the inverter device (1000) as shown in FIG. 4 and can be controlled by the control unit (200) of the inverter device (1000).

[0212] The inverter device (1000) may be a device that supplies power to the supply target unit (L), including the conversion circuit (100) and the control unit (200), as shown in FIG. 4.

[0213] The inverter device (1000) includes an inverter unit (100) (conversion circuit) including the link unit (10) storing DC power, the conversion unit (20) converting the DC power received from the link unit (10) into power to be supplied to the supply target unit (L) by the switching operation of the three pairs of switching elements (S1-S2, S3-S4, S5-S6), and the switching unit (30) switching the connection between the conversion unit (20) and the supply target unit (L) according to the operation mode of the inverter device (1000), and a control signal for controlling the switching operation to the three pairs of switching elements (S1-S2, S3-S4, S5-S6) according to the operation mode to control the conversion unit (20), and a switching signal for controlling the switching unit (30) to operate the conversion unit (30). It includes the above control unit (200) that controls.

[0214] Here, the conversion unit (20) includes the first conversion unit (21), the second conversion unit (22), and the third conversion unit (23), and the conversion unit (30) includes the first conversion unit (31) that connects or disconnects between the output terminal of the second conversion unit (22) and the output terminal of the third conversion unit (23), and the second conversion unit (32) that connects or disconnects between the output terminal of the second conversion unit (22) and the second load terminal (N).

[0215] In this case, each of the output terminal of the first conversion unit (21) and the output terminal of the second conversion unit (22) may include an element having a constant inductance component.

[0216] In addition, the conversion unit (20) further includes the capacitor unit (24) which is arranged between the output terminal of the third conversion unit (23) and the lower end of the lower arm switching element (S6) of the third conversion unit (23), including an element having a certain capacitance component, and the conversion unit (30) may further include the third conversion unit (33) which connects or disconnects the output terminal of the third conversion unit (23) and one end of the capacitor unit (24).

[0217] That is, the inverter unit (100) may be the conversion circuit (100) described above, and the inverter device (1000) may be a device including the inverter unit (100) and the control unit (200) that controls power conversion of the inverter unit (100).

[0218] The above control unit (200) may be a control device formed as a circuit module that is separable from the inverter unit (100).

[0219] That is, each of the inverter unit (100) and the control unit (200) can be formed in the form of separate modules.

[0220] The above control unit (200) may also be a control module included in the inverter unit (100).

[0221] The above control unit (200) can control the inverter unit (100) by applying a control signal to the inverter unit (100).

[0222] The above control unit (200) can control the inverter unit (100) by controlling the control signal applied to the inverter unit (100).

[0223] The control unit (200) controls the switching operation of the conversion unit (20) by applying a control signal for controlling the switching operation to the conversion unit (20), and controls the switching operation of the conversion unit (30) by applying a switching signal for controlling the switching operation to the conversion unit (30), thereby controlling the power conversion and supply of the inverter unit (100).

[0224] The above control unit (200) can control each of the first conversion unit (21) to the third conversion unit (23) included in the conversion unit (20).

[0225] That is, the control unit (200) can control the switching operation of each of the first conversion unit (21) to the third conversion unit (23) by applying a control signal to each of the first conversion unit (21) to the third conversion unit (23).

[0226] The above control unit (200) can also control each of the first switching unit (31) and the second switching unit (32) included in the switching unit (30).

[0227] That is, the control unit (200) can control the switching operation of each of the first switching unit (31) and the second switching unit (23) by applying a switching signal to each of the first switching unit (31) and the second switching unit (32).

[0228] In this way, in the inverter device (1000) including the inverter unit (100) and the control unit (200), the first switching unit (31) and the second switching unit (32) can operate differently from each other.

[0229] The first switching unit (31) and the second switching unit (32) can operate in an OFF state when one of them is in an ON state.

[0230] That is, when the first switching unit (31) operates ON, the second switching unit (32) operates OFF, and when the first switching unit (31) operates OFF, the second switching unit (32) operates ON.

[0231] The above control unit (200) can control the operation of each of the first switching unit (31) and the second switching unit (32) so that the first switching unit (31) and the second switching unit (32) operate differently from each other.

[0232] For example, when an ON operation signal is applied to the first switching unit (31), an OFF operation signal is applied to the second switching unit (32), so that the first switching unit (31) and the second switching unit (32) can be controlled to operate in opposite directions.

[0233] The above control unit (200) can control the operation of the conversion unit (20) and the switching unit (30) differently when the driving method corresponds to linked driving in which the driving method is operated in conjunction with the system and when the driving method corresponds to independent driving in which the driving method is operated separately from the system.

[0234] For example, when the above-mentioned linked operation is applicable, the operation control of the conversion unit (20) and the switching unit (30) may be controlled in mode A, and when the above-mentioned independent operation is applicable, the operation control of the conversion unit (20) and the switching unit (30) may be controlled in mode B, which is different from mode A.

[0235] The above control unit (200) can control the operation of the conversion unit (20) in the first control mode while the driving method corresponds to the linked driving.

[0236] Here, the first control mode may be any type of PWM control mode that controls the switching operation of the conversion unit (20).

[0237] The above first control mode may be, for example, an L2N PWM control mode.

[0238] The above control unit (200) can control the operation of the conversion unit (20) in a second control mode different from the first control mode while the driving method corresponds to the independent driving.

[0239] Here, the second control mode may be any one type of the PWM control mode except the first control mode.

[0240] The second control mode may be, for example, a Split Phase PWM control mode.

[0241] Accordingly, the switching operation of the above-mentioned conversion unit (20) during the linked operation and the switching operation during the independent operation can be performed differently from each other.

[0242] That is, the above conversion unit (20) can perform different switching operations depending on whether the above linked operation or the above independent operation is performed.

[0243] The above control unit (200) can control the first conversion unit (31) so that the output terminal of the second conversion unit (22) and the output terminal of the third conversion unit (23) are separated when the driving method is the independent driving.

[0244] The above control unit (200) can separate the output terminal of the second conversion unit (22) and the output terminal of the third conversion unit (23) by controlling the operation of the first conversion unit (31) to OFF while the driving method corresponds to the independent driving.

[0245] That is, in the case of the independent operation, the control unit (200) can control the first switching unit (31) to operate OFF as shown in FIG. 5.

[0246] The above control unit (200) can control the first conversion unit (31) so that the output terminal of the second conversion unit (22) and the output terminal of the third conversion unit (23) are connected when the driving method is the linked driving.

[0247] The above control unit (200) can control the operation of the first conversion unit (31) to ON while the driving method corresponds to the linked driving, thereby connecting the output terminal of the second conversion unit (22) and the output terminal of the third conversion unit (23).

[0248] That is, in the case of the linked operation, the control unit (200) can control the first switching unit (31) to operate ON as shown in FIG. 7.

[0249] Accordingly, the first conversion unit (31) may be turned OFF as shown in FIG. 5 when the inverter device (1000) is driven in the independent operation mode to separate the output terminal of the second conversion unit (22) and the output terminal of the third conversion unit (23), and may be turned ON as shown in FIG. 7 when the inverter device (1000) is driven in the linked operation mode to connect the output terminal of the second conversion unit (22) and the output terminal of the third conversion unit (23).

[0250] The above control unit (200) can control the second conversion unit (32) so that the output terminal of the second conversion unit (22) and the second load terminal (N) are connected when the driving method is the independent driving.

[0251] The above control unit (200) can control the operation of the second switching unit (32) to ON while the driving method corresponds to the independent driving, thereby connecting the output terminal of the second conversion unit (22) and the second load terminal (N).

[0252] That is, in the case of the independent operation, the control unit (200) can control the second switching unit (32) to operate ON as shown in FIG. 5.

[0253] The above control unit (200) can control the second conversion unit (32) so that the output terminal of the second conversion unit (22) and the second load terminal (N) are separated when the driving method is the linked driving.

[0254] The above control unit (200) can separate the output terminal of the second conversion unit (22) and the second load terminal (N) by controlling the operation of the second switching unit (32) to OFF while the driving method corresponds to the linked driving.

[0255] That is, in the case of the linked operation, the control unit (200) can control the second switching unit (32) to operate OFF as shown in FIG. 7.

[0256] Accordingly, the second switching unit (32) may be turned ON as shown in FIG. 5 when the inverter device (1000) is driven in the independent operation mode to connect the output terminal of the second switching unit (22) and the second load terminal (N), and may be turned OFF as shown in FIG. 6 when the inverter device (1000) is driven in the linked operation mode to separate the output terminal of the second switching unit (22) and the second load terminal (N).

[0257] The above control unit (200) can control the third conversion unit (33) so that the output terminal of the third conversion unit (23) and one end of the capacitor unit (24) are separated when the driving method is the independent driving.

[0258] The above control unit (200) can separate the output terminal of the third conversion unit (23) and one end of the capacitor unit (24) by controlling the operation of the third conversion unit (33) to OFF while the driving method corresponds to the independent driving.

[0259] That is, in the case of the independent operation, the control unit (200) can control the third switching unit (33) to operate OFF as shown in FIG. 5.

[0260] The above control unit (200) can control the third conversion unit (33) so that the output terminal of the third conversion unit (23) and one end of the capacitor unit (24) are connected when the driving method is the linked driving.

[0261] The above control unit (200) can control the operation of the third switching unit (33) to ON while the driving method corresponds to the linked driving, thereby connecting the output terminal of the third conversion unit (23) and one end of the capacitor unit (24).

[0262] That is, in the case of the linked operation, the control unit (200) can control the third switching unit (33) to operate ON as shown in FIG. 7.

[0263] Accordingly, the third conversion unit (33) may be turned OFF as shown in FIG. 5 when the inverter device (1000) is driven in the independent operation mode, thereby separating the output terminal of the third conversion unit (23) and one end of the capacitor unit (24), and may be turned ON as shown in FIG. 7 when the inverter device (1000) is driven in the linked operation mode, thereby connecting the output terminal of the third conversion unit (23) and one end of the capacitor unit (24).

[0264] The control unit (200) as described above controls each of the first conversion unit (31) and the second conversion unit (32) so that the output terminal of the second conversion unit (22) is separated from the second load terminal (N) and connected to the output terminal of the third conversion unit (23), in the case of the linked operation that operates in conjunction with the system, and controls the conversion unit (20) so that the second power source and the third power source are output alternately to the third load terminal (L2), thereby providing a single-phase, two-wire power supply.

[0265] Hereinafter, the specific process of controlling the conversion unit (200) during the linked operation will be described with reference to FIGS. 9 to 11.

[0266] The control unit (200) can control the conversion unit (20) in the order of the first switching mode (MODE 1) to the fourth switching mode (MODE 4) set to different operation patterns for each cycle (T) of the line voltage between the L1 phase and the L2 phase, as illustrated in FIGS. 9 and 10.

[0267] Here, the first switching mode (MODE 1) to the fourth switching mode (MODE 4) may be control modes that control the switching operation of the conversion unit (20) in each of the four sections that divide one cycle (T) of the line voltage into.

[0268] That is, the control unit (200) divides one period (T) of the line voltage into a first section, a second section, a third section, and a fourth section, and controls the conversion unit (20) in the first section with the first switching mode (MODE 1), in the second section with the second switching mode (MODE 2), in the third section with the third switching mode (MODE 3), and in the fourth section with the fourth switching mode (MODE 4).

[0269] Each of the first switching mode (MODE 1) to the fourth switching mode (MODE 4) can be set to control the conversion unit (20) differently.

[0270] Accordingly, the conversion unit (20) can perform switching operations differently for each of the first to fourth sections.

[0271] The above first switching mode (MODE 1) may be a control mode of the first section.

[0272] The above first section may be a section in which the line voltage increases from 0 to a constant positive voltage (+Vx) in the above one cycle (T).

[0273] The above first switching mode (MODE 1) may be a mode in which a pulse-shaped control signal is applied to each of the first conversion unit (21) and the second conversion unit (22) while the line voltage increases from 0 to a constant positive voltage (+Vx), and no control signal is applied to the third conversion unit (23).

[0274] That is, in the first section, the switching elements (S1-S2) of the first conversion unit (21) and the switching elements (S3-S4) of the second conversion unit (22) may operate, and the switching elements (S5-S6) of the third conversion unit (23) may not operate.

[0275] Accordingly, during the first section, the first power can be output to the L1 phase, and the second power can be output to the L2 phase.

[0276] The above second switching mode (MODE 2) may be a control mode of the second section.

[0277] The second section may be a section in which the line voltage increases from a constant positive voltage (+Vx) to a maximum positive voltage and then decreases to 0 in the one cycle (T).

[0278] The above second switching mode (MODE 2) may be a mode in which a pulse-type control signal is applied to the first conversion unit (21), no control signal is applied to the second conversion unit (22), and a control signal of a certain level is applied to one switching element (S6) of the third conversion unit (23) while the line voltage decreases from a certain positive voltage (+Vx) to 0.

[0279] That is, in the second section, the switching elements (S1-S2) of the first conversion unit (21) and one switching element (S6) of the third conversion unit (23) may operate, and the switching elements (S3-S4) of the second conversion unit (22) may not operate.

[0280] Accordingly, during the second section, the first power can be output to the L1 phase, and the third power can be output to the L2 phase.

[0281] The above third switching mode (MODE 3) may be a control mode of the third section.

[0282] The third section may be a section in which the line voltage decreases from 0 to a constant negative voltage (-Vx) in the one cycle (T).

[0283] The third switching mode (MODE 3) may be a mode in which a pulse-shaped control signal is applied to each of the first conversion unit (21) and the second conversion unit (22) while the line voltage decreases from 0 to a constant negative voltage (-Vx), and no control signal is applied to the third conversion unit (23).

[0284] That is, in the third section, the switching elements (S1-S2) of the first conversion unit (21) and the switching elements (S3-S4) of the second conversion unit (22) may operate, and the switching elements (S5-S6) of the third conversion unit (23) may not operate.

[0285] Accordingly, during the third section, the first power can be output to the L1 phase, and the second power can be output to the L2 phase.

[0286] The above fourth switching mode (MODE 4) may be a control mode of the fourth section.

[0287] The fourth section may be a section in which the line voltage decreases from a constant negative voltage (-Vx) to a minimum negative voltage and then increases to 0 in the one cycle (T).

[0288] The fourth switching mode (MODE 4) may be a mode in which a pulse-type control signal is applied to the first conversion unit (21), no control signal is applied to the second conversion unit (22), and a control signal of a certain level is applied to one switching element (S5) of the third conversion unit (23) while the line voltage increases from a certain negative voltage (-Vx) to 0.

[0289] That is, in the fourth section, the switching elements (S1-S2) of the first conversion unit (21) and one switching element (S5) of the third conversion unit (23) may operate, and the switching elements (S3-S4) of the second conversion unit (22) may not operate.

[0290] Accordingly, during the fourth section, the first power can be output to the L1 phase, and the third power can be output to the L2 phase.

[0291] The above control unit (200) can control the operation of the conversion unit (20) by applying a control signal to the conversion unit (20) in the order of the first switching mode (MODE 1) to the fourth switching mode (MODE 4) during one cycle (T) of the line voltage.

[0292] Accordingly, the conversion unit (20) can be controlled and operated in the order of the first switching mode (MODE 1) to the fourth switching mode (MODE 4) during one cycle (T) of the line voltage.

[0293] Hereinafter, the specific operation of the conversion unit (20) in each section as shown in Fig. 9 and the resulting voltage change will be described.

[0294] First, the offset voltage for outputting the line voltage in each section can be calculated as in [Mathematical Formula 1] below.

[0295] [Mathematical Formula 1]

[0296] Mode 1:

[0297] Mode 2:

[0298] Mode 3:

[0299] Mode 4:

[0300] The command voltage of the first conversion unit (21) corresponding to the above L1 phase can be calculated as in [Mathematical Formula 2] below.

[0301] [Equation 2]

[0302]

[0303] The command voltage of the second converter (22) corresponding to the above N phase can be calculated as in [Mathematical Formula 3] below.

[0304] [Equation 3]

[0305] Mode 1, 3:

[0306] Mode 2, 4:

[0307] The command voltage of the third converter (23) corresponding to the above L2 phase can be calculated as in [Mathematical Formula 4] below.

[0308] [Equation 4]

[0309] Mode 1, 3:

[0310] Mode 2, 4:

[0311] As in the above [Mathematical Formula 3] and [Mathematical Formula 4], the second power output from the second conversion unit (22) and the third power output from the third conversion unit (23) can be controlled by an offset voltage.

[0312] As in the above [Mathematical Formula 2] to the above [Mathematical Formula 4], the difference between the voltage on L1 and the voltage on L2 appears as Vref in all modes, so the output voltage appears as the same voltage as Vref.

[0313] In addition, the first conversion unit (21) corresponding to the L1 phase performs continuous PWM operation, the second conversion unit (22) corresponding to the N phase performs PWM operation only near the zero crossing, and the third conversion unit (23) corresponding to the L2 phase performs On / Off operation at the same frequency as the frequency of the command voltage.

[0314] In Mode 2 and Mode 4 of Fig. 9, the second conversion unit (22) performs only a turn-off operation, not a PWM complementary operation. In Mode 2, the lower arm switching element (S6) of the third conversion unit (23) is turned on instead of the lower arm switching element (S4) of the second conversion unit (22), and in Mode 4, the upper arm switching element (S5) of the third conversion unit (23) is turned on instead of the upper arm switching element (S3) of the second conversion unit (22).

[0315] Figures 10 and 11 (a to d) are graphs and equivalent circuits expressing the mechanism by which leakage current occurs in the conversion circuit (100).

[0316] As illustrated in Fig. 10, in Mode 3, both the L1 phase and the N phase are controlled by a reference voltage having a ramp slope, and the parasitic capacitance is slowly charged. At this time, since the leakage current flows in proportion to the rate of change of the parasitic capacitance voltage, a lower leakage current is observed compared to the existing technique. In addition, in Mode 1, the L1 phase and the N phase are also controlled by a reference voltage having a ramp slope in the opposite direction to Mode 3, and the parasitic capacitance is slowly discharged.

[0317] That is, when capacitance is formed between the negative terminal of the link unit (10) and the output terminal of the third converter unit (23), the leakage current can be improved.

[0318] Meanwhile, as shown in FIGS. 11b and 11d, in Mode 2 and Mode 4, control is performed through the L1 phase and the L2 phase in the same manner as in the mode analysis of the existing Totem-pole topology as shown in FIGS. 3a and 3b, but as shown in FIGS. 11a and 11c, control is performed through the L1 phase and the N phase (the second conversion unit) in Mode 1 and Mode 3.

[0319] In this way, the embodiment of the inverter device (1000) in which the control unit (200) controls the inverter unit (100) to perform the linked operation may be implemented as an embodiment of a linked operation method of the inverter device (hereinafter referred to as the operation method).

[0320] The above driving method may be implemented in a manner in which the control unit (200) of the inverter device (1000) controls the inverter unit (100).

[0321] The above driving method may also be implemented in a manner in which the converter (20) operates for one cycle of the line voltage.

[0322] The above driving method is a method in which the inverter device (1000) including the link unit (10) and the first conversion unit (21) to the third conversion unit (23) is operated in conjunction with the system, and as illustrated in FIG. 12, the first conversion unit (21) and the second conversion unit (22) operate to increase the line voltage between the L1 phase and the L2 phase from 0 to a constant positive voltage (+Vx) (S10), the lower switching element (S6) of the first conversion unit (21) and the third conversion unit (23) operates to increase the line voltage from the constant positive voltage (+Vx) and then decrease to 0 (S20), the first conversion unit (21) and the second conversion unit (22) operate to decrease the line voltage from 0 to a constant negative voltage (-Vx) (S30), and the upper switching of the first conversion unit (21) and the third conversion unit (23) The device (S5) operates and includes a step (S40) in which the line voltage decreases from the constant negative voltage (-Vx) and then increases to 0.

[0323] That is, the inverter device (1000) operates in the following order: during one cycle (T) of the line voltage, the first conversion unit (21) and the second conversion unit (22) operate so that the line voltage between the L1 phase and the L2 phase increases from 0 to a constant positive voltage (+Vx) (S10); the lower switching element (S6) of the first conversion unit (21) and the third conversion unit (23) operates so that the line voltage increases from the constant positive voltage (+Vx) and then decreases to 0 (S20); the first conversion unit (21) and the second conversion unit (22) operate so that the line voltage decreases from 0 to a constant negative voltage (-Vx) (S30); and the upper switching element (S5) of the first conversion unit (21) and the third conversion unit (23) operates so that the line voltage decreases from the constant negative voltage (-Vx) and then increases to 0 (S40). Can be.

[0324] Here, the output terminals of the first conversion unit (21) and the second conversion unit (22) may have a constant inductance component formed, and the output terminal of the third conversion unit (23) may have a constant capacitance component formed.

[0325] The step (S10) in which the first conversion unit (21) and the second conversion unit (22) operate to increase the line voltage between the L1 phase and the L2 phase from 0 to a constant positive voltage (+Vx) may be an operation step of the conversion unit (20) according to the first switching mode (Mode 1).

[0326] The step (S20) in which the lower switching element (S6) of the first conversion unit (21) and the third conversion unit (23) operates so that the line voltage increases from the constant positive voltage (+Vx) and then decreases to 0 may be an operation step of the conversion unit (20) according to the second switching mode (Mode 2).

[0327] The step (S30) in which the first conversion unit (21) and the second conversion unit (22) operate to reduce the line voltage from 0 to a constant negative voltage (-Vx) may be an operation step of the conversion unit (20) according to the third switching mode (Mode 3).

[0328] The step (S40) in which the upper switching element (S5) of the first conversion unit (21) and the third conversion unit (23) operates so that the line voltage decreases from the constant negative voltage (-Vx) and then increases to 0 may be an operation step of the conversion unit (20) according to the fourth switching mode (Mode 4).

[0329] The operation of the conversion unit (20) according to these steps S10 to S40 and the resulting voltage change may be as shown in FIGS. 9 to 11.

[0330] The above driving method can start (SS) when one cycle (T) of the line voltage starts, and end (SE) when one cycle (T) of the line voltage ends.

[0331] The above driving method can be performed by repeating steps S10 to S40 each time one cycle (T) of the line voltage is completed.

[0332] That is, after the above S40 step, when one cycle (T) of the line voltage is completed, the process is performed again from the S10 step, and the next cycle (T+1) can be performed (S10->S20->S30->S40->S10-> ......).

[0333] Accordingly, in the above driving method, the start step (SS) may correspond to the S40 step, and the end step (SE) may correspond to the S10 step.

[0334] So far, the above-described conversion circuit (100), the above-described inverter device (1000), and the above-described driving method have been described in detail, but the described embodiments may be modified in various ways without departing from the scope of the present invention. In addition, the scope of the present invention should not be limited to the described embodiments, but should be determined by the claims described below as well as equivalents thereof.

Claims

1. In the power conversion circuit of an inverter device that operates in conjunction with a grid, Link unit that stores DC power; A first conversion unit connected to the L1 phase of the supply target unit, converting the DC power into a first power by a switching operation of at least one pair of switching elements and outputting the converted DC power to the L1 phase; A second conversion unit connected to the L2 phase of the supply target unit, converting the DC power into a second power through a switching operation of at least one pair of switching elements and outputting the converted DC power to the L2 phase; and A third conversion unit is connected to the output terminal of the L2 phase and the second conversion unit, and converts the DC power into a third power by a switching operation of at least one pair of switching elements and outputs it to the L2 phase. The second conversion unit and the third conversion unit are, A power conversion circuit of an inverter device characterized in that the second power source and the third power source are output crosswise on the L2.

2. In paragraph 1, The above first conversion unit, A power conversion circuit of an inverter device, characterized in that a constant inductance component is formed between the output terminal and the L1 phase.

3. In paragraph 1, The above second conversion unit, A power conversion circuit of an inverter device, characterized in that a constant inductance component is formed between the output terminal and the output terminal of the third conversion unit.

4. In paragraph 1, The third conversion unit is, A power conversion circuit of an inverter device characterized in that a constant capacitance component is formed between the output terminal and the lower end of the lower arm switching element.

5. In paragraph 1, The second conversion unit and the third conversion unit are, A power conversion circuit of an inverter device characterized in that when one of the circuits operates, the other does not operate.

6. In paragraph 5, The second conversion unit and the third conversion unit are, A power conversion circuit of an inverter device characterized by operating with different switching patterns.

7. In paragraph 5, The above first conversion unit, A power conversion circuit of an inverter device characterized in that it operates even when either of the second conversion unit and the third conversion unit does not operate.

8. In paragraph 5, The above second conversion unit, A power conversion circuit of an inverter device characterized in that it operates in at least one of a section in which the voltage between the L1 phase and the L2 phase increases from 0 to a certain amount and a section in which the voltage decreases.

9. In paragraph 5, The third conversion unit is, A power conversion circuit of an inverter device characterized in that either an upper-arm switching element or a lower-arm switching element operates.

10. In paragraph 9, The third conversion unit is, A power conversion circuit of an inverter device, characterized in that the lower arm switching element operates during a period in which the voltage between the L1 phase and the L2 phase is +, and the upper arm switching element operates during a period in which the voltage between the L1 phase and the L2 phase is -.

11. Link section for storing DC power; A conversion unit including at least three pairs of switching elements, which converts the DC power received from the link unit into power to be supplied to the supply target unit through the switching operation of the three pairs of switching elements; A switching unit that switches the connection between the conversion unit and the supply target unit according to the driving method; and In an inverter device, the inverter device includes a control unit that controls the conversion unit by applying a control signal for controlling a switching operation to the three pairs of switching elements according to the driving method, and a control unit that controls the conversion unit by applying a switching signal to the conversion unit. The above conversion part, A first conversion unit that converts the DC power into a first power source and outputs it to a first load terminal of the supply target unit; A second conversion unit that converts the DC power into a second power and outputs it to the second load terminal or the third load terminal of the supply target unit; and It includes a third conversion unit that converts the DC power into a third power and outputs it to the third load terminal, The above switching part is, A first switching unit that connects or disconnects the output terminal of the second switching unit and the output terminal of the third switching unit; and It includes a second switching unit that connects or disconnects between the output terminal of the second switching unit and the second load terminal, The above control unit, If the above driving method is a linked driving method that operates in conjunction with the system, An inverter device characterized in that the first conversion unit and the second conversion unit are controlled so that the output terminal of the second conversion unit is separated from the second load terminal and connected to the output terminal of the third conversion unit, and the conversion unit is controlled so that the second power source and the third power source are output alternately to the third load terminal.

12. In paragraph 11, Each of the output terminal of the first conversion unit and the output terminal of the second conversion unit, An inverter device characterized by including an element having a constant inductance component.

13. In paragraph 11, The above conversion part, Further comprising a capacitor section disposed between the output terminal of the third conversion section and the lower end of the lower arm switching element of the third conversion section, including an element having a constant capacitance component; The above switching part is, Further comprising a third conversion unit that connects or disconnects between the output terminal of the third conversion unit and the capacitor unit, The above control unit, In the case of the above linked driving, An inverter device characterized in that the third conversion unit is further controlled so that the output terminal of the third conversion unit and the capacitor unit are connected.

14. In paragraph 11, The above control unit, In the case of the above linked driving, An inverter device characterized in that the converter is controlled in the order of the first switching mode to the fourth switching mode, which are set to different operation patterns, for each cycle of the line voltage between the first load stage and the third load stage.

15. In paragraph 14, The above first switching mode is, An inverter device characterized in that the mode is such that a pulse-shaped control signal is applied to each of the first conversion unit and the second conversion unit while the line voltage increases from 0 to a certain positive voltage, and no control signal is applied to the third conversion unit.

16. In paragraph 14, The above second switching mode is, An inverter device characterized in that the mode is such that a pulse-shaped control signal is applied to the first conversion unit, no control signal is applied to the second conversion unit, and a control signal of a certain level is applied to one switching element of the third conversion unit while the line voltage decreases from a certain positive voltage to 0.

17. In paragraph 14, The third switching mode is: An inverter device characterized in that the mode is such that a pulse-shaped control signal is applied to each of the first conversion unit and the second conversion unit while the line voltage decreases from 0 to a certain negative voltage, and no control signal is applied to the third conversion unit.

18. In paragraph 14, The above fourth switching mode is, An inverter device characterized in that the mode is such that a pulse-shaped control signal is applied to the first conversion unit, no control signal is applied to the second conversion unit, and a control signal of a certain level is applied to one switching element of the third conversion unit while the line voltage increases from a certain negative voltage to 0.

19. Link section for storing DC power; A first conversion unit connected to the L1 phase of the supply target unit, converting the DC power into a first power by a switching operation of at least one pair of switching elements and outputting the converted DC power to the L1 phase; A second conversion unit connected to the L2 phase of the supply target unit, converting the DC power into a second power through a switching operation of at least one pair of switching elements and outputting the converted DC power to the L2 phase; and In a method for grid-connected operation of an inverter device, including a third conversion unit connected to the output terminal of the L2 phase and the second conversion unit, converting the DC power into a third power by a switching operation of at least one pair of switching elements and outputting it to the L2 phase, A step in which the first conversion unit and the second conversion unit operate so that the line voltage between the L1 phase and the L2 phase increases from 0 to a certain positive voltage; A step in which the lower switching elements of the first conversion unit and the third conversion unit operate so that the line voltage increases from the constant positive voltage and then decreases to 0; A step in which the first conversion unit and the second conversion unit operate to reduce the line voltage from 0 to a certain negative voltage; and A method for grid-connected operation of an inverter device, characterized in that it includes a step in which the upper switching elements of the first conversion unit and the third conversion unit operate so that the line voltage decreases from the constant negative voltage and then increases to 0.

20. In paragraph 19, The output terminals of the first conversion unit and the second conversion unit are A certain inductance component is formed, The output terminal of the third converter is A method for grid-connected operation of an inverter device characterized in that a constant capacitance component is formed.

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