Initial charging method for DC / DC converter station having input series-output parallel structure

Abstract

Disclosed is an initial charging method for a DC / DC converter station having an input series-output parallel structure. The initial charging method for a DC / DC converter station having an input series-output parallel structure, according to an embodiment of the present invention, comprises the steps of: applying auxiliary power to a secondary-side conversion unit of a DC converter in the converter station so as to charge a secondary-side capacitor in the secondary-side conversion unit; sensing a charge amount of voltage of the secondary-side capacitor; charging a primary-side capacitor in a primary-side conversion unit of the DC converter through a transformer in the DC converter, on the basis of a result of the sensing of the charge amount of voltage of the secondary-side capacitor; sensing a charge amount of voltage of the primary-side capacitor; and applying a grid voltage to the converter station on the basis of a result of the sensing of the charge amount of voltage of the primary-side capacitor, wherein in the step of applying the grid voltage, the grid voltage may be applied only when the magnitude of the voltage of the primary-side capacitor is equal to a value obtained by dividing the grid voltage by the number of DC converters in the converter station.

Description

Initial charging method of a DC / DC converter station having an input series-output parallel structure

[0001] The present invention relates to an initial charging method for a DC / DC converter station having an input series-output parallel structure. More specifically, the present invention relates to a method for charging a medium voltage DC / DC converter station having an input series-output parallel structure by connecting an auxiliary power source to the low voltage side.

[0002] To meet the growing global demand for electricity, the need to strengthen and restructure power grids to ensure a stable and sustainable power supply is growing. MVDC / LVDC converter stations, which link medium voltage (MV) DC (MVDC) voltage with low voltage (LV) DC (LVDC) voltage, have a modular structure that connects multiple power electronic building blocks (PEBBs) in series and parallel to convert MVDC voltage to LVDC voltage.

[0003] The MVDC / LVDC converter station can stably produce high output through the input series-output parallel (ISOP: Input Series Output Parallel) structure, and can secure high connectivity and safety by adopting a bidirectional insulated structure.

[0004] However, when an MVDC / LVDC converter station with a series-input-parallel output structure has a high input voltage, applying MVDC input power without initial charging of the input capacitor can result in a very large inrush current, potentially causing converter damage. Therefore, a method for charging the input capacitor is needed to prevent inrush current and converter damage.

[0005] The technical problem of the present invention is to provide an initial charging method of a DC / DC converter station having an input series-output parallel structure.

[0006] Another technical object of the present invention is to provide an initial charging method of a DC / DC converter station capable of limiting inrush current using a separate power supply device.

[0007] Another technical object of the present invention is to provide an initial charging method of a DC / DC converter station that is inexpensive and can reduce the size of the converter station compared to performing charging using a wireless power transmission device.

[0008] The technical problems to be achieved in the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0009] According to one aspect of the present invention, an initial charging method of a DC / DC converter station having an input series-output parallel structure includes the steps of: charging a secondary capacitor in a secondary conversion unit of a DC converter in the converter station by applying auxiliary power to the secondary conversion unit of the DC converter in the converter station; sensing a charge amount of the secondary capacitor voltage; charging a primary capacitor in a primary conversion unit of the DC converter through a transformer in the DC converter based on a result of sensing the charge amount of the secondary capacitor voltage; sensing a charge amount of the primary capacitor voltage; and applying a grid voltage to the converter station based on a result of sensing the charge amount of the primary capacitor voltage, wherein the grid voltage may be applied only when a magnitude of the primary capacitor voltage is equal to a value obtained by dividing the grid voltage by the number of DC converters in the converter station.

[0010] In the initial charging method of the DC / DC converter station, the step of charging the secondary capacitor can charge the secondary capacitor by limiting the inrush current through an initial charging resistor connected in series to the auxiliary power source.

[0011] In the initial charging method of the DC / DC converter station, the step of charging the primary capacitor includes the step of transmitting power from the secondary conversion unit to the primary conversion unit by the transformer when the voltage of the secondary capacitor is equal to the voltage size of the auxiliary power source, and the step of charging the primary capacitor by the transmitted power, and the primary capacitor can be charged by limiting the inrush current through soft switching.

[0012] In the initial charging method of the DC / DC converter station, the step of applying the grid voltage may, when the magnitude of the primary capacitor voltage is smaller than a value obtained by dividing the grid voltage by the number of DC converters in the converter station, boost the primary capacitor voltage through the power transmission by the transformer until the magnitude of the primary capacitor voltage becomes equal to a value obtained by dividing the grid voltage by the number of DC converters in the converter station.

[0013] The features briefly summarized above of the present invention are merely exemplary aspects of the detailed description of the present invention described below and do not limit the scope of the present invention.

[0014] According to the present invention, an initial charging method of a DC / DC converter station having an input series-output parallel structure can be provided.

[0015] Additionally, according to the present invention, a method for initial charging of a DC / DC converter station can be provided that can limit inrush current using a separate power supply device.

[0016] In addition, according to the present invention, a method for initial charging of a DC / DC converter station can be provided that is inexpensive and can reduce the size of the converter station compared to performing charging using a wireless power transmission device.

[0017] The effects that can be obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by a person having ordinary skill in the art to which the present invention belongs from the description below.

[0018] FIG. 1 is a drawing for explaining an auxiliary power source installed in a DC / DC converter station having an input series-output parallel structure according to one embodiment of the present invention.

[0019] FIG. 2 is a drawing for explaining a DC converter according to one embodiment of the present invention.

[0020] FIG. 3 is a diagram illustrating an internal circuit diagram of a DC converter and an auxiliary power source connected thereto according to one embodiment of the present invention.

[0021] FIG. 4 is a drawing for explaining the voltage waveforms of the primary and secondary capacitors when performing the initial charging method according to one embodiment of the present invention.

[0022] FIG. 5 is a flowchart illustrating an initial charging method of a DC / DC converter station having an input series-output parallel structure according to one embodiment of the present invention.

[0023] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0024] In describing embodiments of the present invention, if a detailed description of a known configuration or function is judged to obscure the gist of the present invention, a detailed description thereof will be omitted. Furthermore, portions irrelevant to the description of the present invention in the drawings have been omitted, and similar portions have been designated with similar drawing reference numerals.

[0025] In the present invention, when a component is said to be "connected," "coupled," or "connected" to another component, this may include not only a direct connection but also an indirect connection in which another component exists in between. Furthermore, when a component is said to "include" or "have" another component, unless otherwise specifically stated, this does not exclude the other component, but rather implies that the other component may be included.

[0026] In the present invention, terms such as first, second, etc. are used only for the purpose of distinguishing one component from another component, and do not limit the order or importance between components unless specifically stated otherwise. Therefore, within the scope of the present invention, a first component in one embodiment may be referred to as a second component in another embodiment, and similarly, a second component in one embodiment may be referred to as a first component in another embodiment.

[0027] In the present invention, distinct components are used to clearly illustrate their respective characteristics, and do not necessarily imply that the components are separated. In other words, multiple components may be integrated into a single hardware or software unit, or a single component may be distributed into multiple hardware or software units. Therefore, even if not specifically mentioned, such integrated or distributed embodiments are also included within the scope of the present invention.

[0028] In the present invention, the components described in various embodiments are not necessarily essential components, and some may be optional components. Therefore, embodiments comprising a subset of the components described in one embodiment are also within the scope of the present invention. Furthermore, embodiments that include other components in addition to the components described in various embodiments are also within the scope of the present invention.

[0029] Hereinafter, an initial charging method of a DC / DC converter station having an input series-output parallel structure according to one embodiment of the present invention will be described with reference to each drawing.

[0030] FIG. 1 is a drawing for explaining an auxiliary power source installed in a DC / DC converter station having an input series-output parallel structure according to one embodiment of the present invention.

[0031] Referring to Fig. 1, it can be seen that an MVDC / LVDC converter station that links a medium voltage (MV) DC (MVDC) voltage and a low voltage (LV) DC (LVDC) voltage is configured with a number of power electronic building blocks (PEBBs) connected in series and parallel to convert the MVDC voltage into an LVDC voltage while stably producing a high output. At this time, in Fig. 1, the input side (Vin) may be a medium voltage, and the output side (Vo) may be a low voltage.

[0032] The converter station illustrated in Fig. 1 may be composed of a plurality of DC converters that convert a voltage distributed from a high-voltage input voltage (Vin) into DC-DC. Since the input sides are connected in series, the input voltage value of each DC converter may be a value obtained by dividing the input voltage (Vin) by the number of DC converters (n, where n is a natural number). In addition, since the output sides are connected in parallel, the output voltage values ​​of each DC converter may all be the same.

[0033] Referring to Fig. 1, it can be confirmed that an auxiliary power source (100) is connected to the output section (low voltage side) of the nth (n is a natural number) DC converter. It can be confirmed that the voltage source of the auxiliary power source has a voltage value of Vaux and is connected in series with a resistor.

[0034] FIG. 2 is a drawing for explaining a DC converter according to one embodiment of the present invention.

[0035] The DC converter illustrated in FIG. 2 may be a converter corresponding to one of the plurality of DC converters illustrated in FIG. 1. Referring to FIG. 2, a schematic diagram of the DC converter is illustrated, and the DC converter may include a primary conversion unit that converts a distributed DC input voltage into a first AC voltage, a transformation unit including a transformer that converts the first AC voltage into a second AC voltage according to a turns ratio of a multi-winding transformer, a secondary conversion unit that converts the second AC voltage back into a DC output voltage, and an upper control unit that controls the overall operation of the DC converter.

[0036] FIG. 3 is a diagram illustrating an internal circuit diagram of a DC converter and an auxiliary power source connected thereto according to one embodiment of the present invention.

[0037] Referring to FIG. 3, a specific internal circuit diagram of the DC converter in FIG. 2 described above is illustrated. The DC converter may include, in addition to a primary-side conversion unit and a secondary-side conversion unit, a primary-side control power supply unit (210), a primary-side sensing unit (220), a secondary-side control power supply unit (310), and a secondary-side control unit (320). At this time, an auxiliary power supply (100) may be applied to the secondary-side control power supply unit (310).

[0038] The upper control unit described in Fig. 2 can be divided into a primary sensing unit (220) and a secondary control unit (320) to ensure insulation, and information required for control can be shared using optical communication.

[0039] The primary sensing unit (220) may include a primary control power unit (210) that converts the voltage of the primary capacitor to supply control power. Alternatively, the primary control power unit (210) may not be included in the primary sensing unit (220) but may exist separately.

[0040] The secondary control unit (320) may include a secondary control power unit (310) that converts the voltage of the secondary capacitor to supply control power. At this time, the secondary control power unit (310) may convert the auxiliary voltage value (Vaux) of the auxiliary power source (100) to supply control power to the secondary capacitor. Alternatively, the secondary control power unit (310) may not be included in the secondary control unit (320) and may exist separately.

[0041] The auxiliary power source (100) may be included within the DC converter according to one embodiment of the present invention, or may be separately located externally. The auxiliary power source (100) may be composed of a battery, a power converter, or a transformer, and may include a resistor for limiting inrush current and at least one switch. The auxiliary power source (100) may be connected to a secondary port of the DC converter (Port 2 or Port 4 in FIG. 3), and may be connected to both ports or to only one port.

[0042] An initial charging method of a DC / DC converter station having an input series-output parallel structure according to one embodiment of the present invention may include a step of charging a secondary capacitor (STEP 1), a step of charging a primary capacitor through switching (STEP 2), and a step of connecting an MVDC system and disconnecting an auxiliary power source (STEP 3).

[0043] In the step of charging the secondary capacitor (STEP 1), power is supplied to the secondary control power supply (310) through the auxiliary power supply (100), and the secondary control unit (320) can be activated. At this time, the inrush current is limited through the initial charging resistor connected in series to the auxiliary power supply (100), so that the secondary capacitor can be charged.

[0044] In the step of charging the primary capacitor through switching (STEP 2), when the voltage of the secondary capacitor is charged to be the same as the voltage size of the auxiliary power source (100), the primary capacitor can be charged through power transfer from the secondary side to the primary side through the transformer. That is, power can be transferred to the primary side conversion unit through the secondary side conversion unit, and at this time, charging can be performed while limiting the inrush current of the primary side through soft switching. When the voltage charging of the primary side capacitor is completed, the primary side sensing unit (220) is turned on, so that the DC converter can be controlled. At this time, when the voltage size of the primary side capacitor is smaller than the voltage size obtained by dividing the input voltage by the number of DC converters, additional power transfer control can be performed. This allows for additional charging to occur until the voltage of the primary capacitor becomes equal to the voltage obtained by dividing the input voltage by the number of DC converters through the boosting of the primary capacitor voltage. When the charging of the primary capacitor is finally completed, the sum of the input voltages of multiple DC converters connected in series can become equal to the magnitude of the MVDC input voltage.

[0045] In the MVDC system connection and auxiliary power disconnection step (STEP 3), if the primary capacitor charging is finally completed as a result of the above STEP 2, the converter station can be connected to the MVDC system because no current flows even if the MVDC input voltage is connected, and thus the MVDC system can be connected. When the MVDC system is connected to the converter station, power transmission from the secondary side can be stopped, and also, the auxiliary power (100) can be disconnected so that power can be transmitted from the input side to the output side.

[0046] FIG. 4 is a drawing for explaining the voltage waveforms of the primary and secondary capacitors when performing the initial charging method according to one embodiment of the present invention.

[0047] In the graph shown in Fig. 4, the voltage of the primary capacitor is shown as a solid line, and the voltage of the secondary capacitor is shown as a dashed-dotted line.

[0048] STEP 1, STEP 2, and STEP 3 illustrated in FIG. 4 may refer to each step described in FIG. 3. Referring to FIG. 4, it can be confirmed that in STEP 1, charging of the secondary capacitor begins at 0.1 seconds, and the voltage of the secondary capacitor increases.

[0049] Additionally, when STEP 2 arrives after 0.5 seconds, charging of the primary capacitor can begin. At this time, although charging of the primary capacitor is initially completed, it can be confirmed that primary voltage boosting has occurred because the voltage magnitude of the primary capacitor is smaller than the voltage magnitude obtained by dividing the input voltage by the number of DC converters.

[0050] In addition, when the charging of the primary capacitor is finally completed and 1.5 seconds have passed, STEP 3 can be performed. At this time, when the MVDC system is connected to the converter station, the auxiliary power supply (100) can be disconnected. Referring to Fig. 4, it can be confirmed that the voltage of the secondary capacitor decreases again when the auxiliary power supply (100) is disconnected. At this time, the charging of the secondary capacitor through the auxiliary power supply (100), disconnection of the auxiliary power supply (100), and connection to the MVDC system can be operations performed from the upper control unit described in Fig. 2.

[0051] FIG. 5 is a flowchart illustrating an initial charging method of a DC / DC converter station having an input series-output parallel structure according to one embodiment of the present invention. The contents described with respect to FIGS. 1 to 4 can also be applied to FIG. 5.

[0052] An initial charging method of a DC / DC converter station having an input series-output parallel structure according to one embodiment of the present invention may include a step (S101) in which an auxiliary power source (100) is applied to a secondary-side conversion unit of a DC converter in the converter station to charge a secondary-side capacitor. At this time, the step S101 may be performed by limiting an inrush current through an initial charging resistor connected in series to the auxiliary power source (100). The step S101 may be performed through an upper control unit.

[0053] And, when power is supplied to the secondary control power supply (310) through the auxiliary power supply (100) and the secondary control unit (320) is activated, the charge amount of the secondary capacitor voltage can be sensed through the secondary control unit (320) (S102).

[0054] In addition, based on the sensing result of step S102, the primary capacitor can be charged through the transformer (S103). At this time, in step S103, when the voltage of the secondary capacitor is the same as the voltage size of the auxiliary power source, power is transferred from the secondary conversion unit to the primary conversion unit by the transformer, and the primary capacitor can be charged by the transferred power. In addition, step S103 can charge the primary capacitor by limiting the inrush current through soft switching.

[0055] When the voltage of the primary capacitor is charged and the voltage charging of the primary capacitor is completed, the primary sensing unit (220) can be activated, and the primary sensing unit (220) can sense the charge amount of the primary capacitor (S104).

[0056] As a result of the sensing of the above S104, if the magnitudes of the primary capacitor voltage and the secondary capacitor voltage are not the same, the primary capacitor voltage charging can be performed again. At this time, only when the magnitudes of the primary capacitor voltage and the secondary capacitor voltage are the same and the magnitude of the primary capacitor voltage is equal to the value obtained by dividing the system voltage by the number of DC converters in the converter station, the auxiliary power source (100) is disconnected by opening the switch by the upper control unit, and the MVDC system can be input (S105).

[0057] If the magnitude of the primary capacitor voltage is less than a value obtained by dividing the grid voltage by the number of DC converters in the converter station, the primary capacitor voltage can be boosted through the power transmission by the transformer until the magnitude of the primary capacitor voltage becomes equal to a value obtained by dividing the grid voltage by the number of DC converters in the converter station.

[0058] While the exemplary methods of the present invention are presented as a series of operations for clarity of description, this is not intended to limit the order in which the steps are performed, and individual steps may be performed simultaneously or in different orders, if desired. To implement a method according to the present invention, additional steps may be included in addition to the exemplified steps, some steps may be excluded and the remaining steps may be included, or some steps may be excluded and additional steps may be included.

[0059] The various embodiments of the present invention are not intended to list all possible combinations, but rather to illustrate representative aspects of the present invention, and the matters described in the various embodiments may be applied independently or in combinations of two or more.

[0060] In addition, various embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof. In the case of hardware implementation, it may be implemented by one or more ASICs (Application Specific Integrated Circuits), DSPs (Digital Signal Processors), DSPDs (Digital Signal Processing Devices), PLDs (Programmable Logic Devices), FPGAs (Field Programmable Gate Arrays), general processors, controllers, microcontrollers, microprocessors, etc.

[0061] The scope of the present invention includes software or machine-executable instructions (e.g., operating systems, applications, firmware, programs, etc.) that cause operations according to the methods of various embodiments to be executed on a device or a computer, and a non-transitory computer-readable medium having such software or instructions stored thereon and executable on the device or computer.

Claims

1. In the initial charging method of a DC / DC converter station having an input series-output parallel structure, A step of charging a secondary capacitor in the secondary conversion unit by applying auxiliary power to the secondary conversion unit of the DC converter in the converter station; A step of sensing the charge amount of the secondary capacitor voltage; A step of charging a primary capacitor in a primary conversion section of the DC converter through a transformer in the DC converter based on the sensing result of the charge amount of the secondary capacitor voltage; A step of sensing the charge amount of the primary capacitor voltage; and A step of applying grid voltage to the converter station based on the sensing result of the charge amount of the primary capacitor voltage, The step of applying the above system voltage is: Characterized in that the grid voltage is applied only when the magnitude of the primary capacitor voltage is equal to the value of the grid voltage divided by the number of DC converters in the converter station. Initial charging method of DC / DC converter station.

2. In paragraph 1, The step of charging the secondary capacitor is: Characterized in that the secondary capacitor is charged by limiting the inrush current through an initial charging resistor connected in series to the auxiliary power source. Initial charging method of DC / DC converter station.

3. In paragraph 1, The step of charging the primary capacitor is: If the voltage of the secondary capacitor is the same as the voltage size of the auxiliary power supply, A step of transmitting power from the secondary side conversion unit to the primary side conversion unit by the transformer; and A step of charging the primary capacitor by the transmitted power is included, It is characterized by charging the primary capacitor by limiting the inrush current through soft switching. Initial charging method of DC / DC converter station.

4. In paragraph 3, The step of applying the above system voltage is: If the magnitude of the primary capacitor voltage is less than the value obtained by dividing the grid voltage by the number of DC converters in the converter station, Characterized in that the primary capacitor voltage is boosted until the magnitude of the primary capacitor voltage becomes equal to a value obtained by dividing the grid voltage by the number of DC converters in the converter station through the power transmission by the transformer. Initial charging method of DC / DC converter station.

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