Static active / reactive power compensator having energy storage system

Abstract

The present invention relates to a static active / reactive power compensator having an energy storage system to simultaneously supply active power and reactive power to a power system. The static active / reactive power compensator of the present invention comprises: a plurality of AC / DC converters which are connected to each other in series and convert an AC voltage supplied from a smart grid into a DC voltage; a plurality of DC / DC converters which are connected in series to the plurality of AC / DC converters and convert the DC voltage of a high voltage outputted from the AC / DC converters into a DC voltage of a relatively low voltage; and an energy storage system (ESS) for storing the DC voltage of the low voltage outputted from each of the plurality of insulated DC / DC converters, wherein the insulated DC / DC converters include a transformer to physically insulate a primary high-voltage side from a secondary low-voltage side.

Description

Stationary active / reactive power compensation device with energy storage device

[0001] The present invention relates to a stationary active / reactive power compensation device (Energy-STATCOM; E-STATCOM) having an energy storage device, and more particularly, to a stationary active / reactive power compensation device configured to simultaneously supply active power and reactive power to a power system by having an energy storage device.

[0002] Reactive power compensation is essential for the stable operation of AC power systems. Therefore, devices such as Static Var Compensation (SVC) and Static Synchronous Compensators (STATCOMs), which leverage the rapid response of power electronic components, are being introduced as circulating reactive power sources in power systems.

[0003] As is well known, the stationary reactive power compensation device (STATCOM) is a type of FACTS (Flexible AC Transmission System) device that is connected to the power grid and is a power electronics-based reactive power compensation device used to increase power transmission capacity and maximize the utilization rate of existing equipment while maintaining the stability and availability of the system.

[0004] These STATCOMs are connected to the main bus of the power system and supply reactive power to the entire power system, thereby increasing the transmission efficiency of active power.

[0005] STATCOM is well described in Patent Publication No. 10-1401038, Patent Publication No. 10-1149203, etc.

[0006] In the case of the existing STATCOM topology, only the function of compensating for reactive power is possible because there is no energy storage device that charges a lot of energy, such as a battery.

[0007] However, in order to compensate for the active power in the existing STATCOM, an energy storage device is required, but since the energy storage device cannot withstand the high-voltage insulation due to the structure of the STATCOM, a new STATCOM topology is required.

[0008] The present invention aims to provide a stationary active / active power compensation device equipped with an energy storage device so as to be capable of compensating not only active power but also reactive power.

[0009] The present invention aims to provide a stationary active / active power compensation device having a structure in which an energy storage device is connected by connecting an insulated DC / DC converter to an existing STATCOM structure.

[0010] The present invention aims to provide a stationary active / reactive power compensation device capable of simultaneously transmitting active power and reactive power to a power system by complementing the shortcomings of existing STATCOMs.

[0011] A stationary active / reactive power compensation device (E-STATCOM) having an energy storage device according to an embodiment of the present invention comprises: a plurality of AC / DC converters that are connected in series with each other and each convert an AC voltage supplied from a smart grid into a DC voltage; a plurality of isolated DC / DC converters that are connected in series with the plurality of AC / DC converters and each convert a high-voltage DC voltage output from the AC / DC converters into a relatively low-voltage DC voltage; and an energy storage device (ESS) that stores a low-voltage DC voltage output from the plurality of isolated DC / DC converters, wherein the isolated DC / DC converters include a transformer and physically insulate a primary high-voltage side and a secondary low-voltage side of the transformer.

[0012] In the present invention, the insulated DC / DC converter outputs high voltage and low current at the input terminal as low voltage and high current at the output terminal.

[0013] In the present invention, the insulated DC / DC converter has a DAB (Dual-Active Bridge) structure.

[0014] In the present invention, the insulated DC / DC converter has a TAB (Triple-Active Bridge) structure.

[0015] In the present invention, active power is generated using the voltage stored in the energy storage device (ESS) and transmitted to the grid.

[0016] A stationary active / active power compensation device (E-STATCOM) having an energy storage device according to an embodiment of the present invention has one or more of the following effects.

[0017] According to the present invention, not only reactive power but also active power can be compensated in a stationary reactive power compensation device.

[0018] According to the present invention, a stationary active / active power compensation device having a simple structure can be provided because an energy storage device is connected by connecting an insulated DC / DC converter to an existing STATCOM.

[0019] According to the present invention, since high voltage and low voltage are insulated in an insulated DC / DC converter, existing ESS can be applied directly.

[0020] According to the present invention, since it is insulated with an insulated DC / DC converter, it is possible to compensate for active power for a longer period of time.

[0021] According to the present invention, active power and reactive power can be simultaneously transmitted to a power system using an existing STATCOM.

[0022] FIG. 1 is a schematic diagram of an E-STATCOM topology according to an embodiment of the present invention.

[0023] Figure 2 is a detailed configuration diagram of E-STACOM according to an embodiment of the present invention.

[0024] Figure 3 is a configuration diagram of a sub-module for E-STATCOM according to an embodiment of the present invention.

[0025] Figure 4 is a configuration diagram of an insulated DC / DC converter according to an embodiment of the present invention.

[0026] Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. When designating components in each drawing, it should be noted that, where possible, identical components will be given the same reference numerals, even if they appear in different drawings. Furthermore, when describing embodiments of the present invention, detailed descriptions of related known structures or functions will be omitted if they are deemed to hinder understanding of the embodiments of the present invention.

[0027] FIG. 1 is a schematic diagram of an E-STATCOM topology according to an embodiment of the present invention.

[0028] Referring to FIG. 1, a stationary active / active power compensation device (Energy-STATCOM; E-STATCOM) (100) having an energy storage device according to an embodiment of the present invention can be connected to a smart grid (10) via a transformer (20). This smart grid (10) can include, for example, a power plant. The power plant can be a renewable energy power plant.

[0029] E-STATCOM (100) can receive AC power transmitted from a power plant and convert it into DC power. At this time, the voltage of the power transmitted to the load side (not shown) by E-STATCOM (100) can be regulated or reactive power can be supplied or absorbed.

[0030] The E-STATCOM (100) according to the present embodiment may include an AC / DC converter (110), an isolated DC / DC converter (120), and an energy storage system (ESS) (130).

[0031] The AC / DC converter (110) can convert AC voltage transmitted from the smart grid (10) into DC voltage and output it.

[0032] An isolated DC / DC converter (120) can convert high-voltage DC power converted from an AC / DC converter (110) into a relatively lower low-voltage DC voltage.

[0033] An isolated DC / DC converter (120) includes a transformer and can physically insulate the primary high voltage side and the secondary low voltage side of the transformer.

[0034] The E-STATCOM (100) of this embodiment may include a plurality of AC / DC converters (110) and an isolated DC / DC converter (120).

[0035] An AC / DC converter (110) and an isolated DC / DC converter (120) may be submodules constituting an E-STATCOM (100). A plurality of such submodules may be connected in series with each other.

[0036] An energy storage device (ESS) (130) can be connected to a plurality of insulated DC / DC converters (120). The voltage output from the insulated DC / DC converters (120) is stored in the ESS (130).

[0037] ESS (130) can be a rechargeable battery or supercapacitor.

[0038] Figure 2 is a configuration diagram of E-STATCOM according to an embodiment of the present invention.

[0039] Referring to FIG. 2, the sub-module (140) for E-STATCOM (100) according to an embodiment of the present invention may be configured in three phases.

[0040] A plurality of sub-modules (140) may be provided, and these plurality of sub-modules (140) may be connected in series with each other.

[0041] Each submodule (140) may be configured to include an AC / DC converter (110) and an isolated DC / DC converter (120).

[0042] The AC / DC converter (110) converts AC voltage transmitted from the smart grid (10) into DC voltage.

[0043] The isolated DC / DC converter (120) converts high-voltage DC power converted from the AC / DC converter (110) into a relatively lower low-voltage DC voltage.

[0044] An isolated DC / DC converter (120) can insulate the high voltage side of the front end (primary side) and the low voltage side of the rear end (secondary side) of the transformer (124) by using a transformer (124).

[0045] A plurality of insulated DC / DC converters (120) are all connected to an energy storage device (ESS) (130), and the voltage output from each insulated DC / DC converter (120) is stored in the ESS (130).

[0046] Figure 3 is a configuration diagram of a sub-module for E-STATCOM according to an embodiment of the present invention.

[0047] Referring to FIG. 3, a sub-module (140) for E-STATCOM (100) according to an embodiment of the present invention may be configured to include an AC / DC converter (110) and an isolated DC / DC converter (120).

[0048] The AC / DC converter (110) may include an AC / DC rectifier (111) and a link capacitor (112).

[0049] The AC / DC rectifier (111) can rectify high-voltage AC power transmitted from the smart grid (10) and convert it into high-voltage DC power. The high-voltage DC power can be transmitted to the insulated DC / DC converter (120) at the subsequent stage or charged into the link capacitor (112).

[0050] An isolated DC / DC converter (120) may be configured to include a primary DC / DC converter (121), a transformer (122), a secondary DC / DC converter (123), and an output capacitor (124).

[0051] The primary side DC / DC converter (121) is the primary side of the insulated DC / DC converter (120) and can generate a high-voltage DC voltage at high frequency.

[0052] The secondary side DC / DC converter (123) and output capacitor (124) can convert high frequency back into low voltage DC voltage as the secondary side of the insulated DC / DC converter (120).

[0053] In this way, the insulated DC / DC converter (120) converts high-voltage direct current into low-voltage direct current.

[0054] A high-frequency transformer (122) may be placed between the front and rear stages of an isolated DC / DC converter (120). This is to isolate the high-voltage side of the front stage (the primary side of the transformer) and the low-voltage side of the rear stage (the secondary side of the transformer) of the isolated DC / DC converter (120).

[0055] The AC / DC converter (110) connected to the smart grid (10) is connected in series with the insulated DC / DC converter (120), and since the AC / DC converter (110) and the insulated DC / DC converter (120) are composed of semiconductor transformers, initial charging of the link capacitor (112) provided in the AC / DC converter (110) and the output capacitor (124) provided in the insulated DC / DC converter (120) is required for stable operation.

[0056] Meanwhile, the submodule (140) may include a controller (not shown) for controlling the operation of the AC / DC converter (110) and the DC / DC converter (120).

[0057] At this time, the controller can control the operation of the AC / DC converter (110) and the DC / DC converter (120) by operating the switches provided inside the AC / DC converter (110) and the DC / DC converter (120), respectively.

[0058] The low-voltage DC voltage output from the insulated DC / DC converter (120) is provided to each energy storage device (ESS) (130) and stored in the ESS (130).

[0059] At this time, an important feature of the present invention is that the insulated DC / DC converter (120) physically insulates the high voltage side of the AC / DC converter (110) at the front end and the low voltage side of the ESS (130) at the rear end.

[0060] This means that the voltage stored in the link capacitor (112) is high voltage, and the voltage stored in the ESS (130) is low voltage. Both sides are physically isolated by an insulated DC / DC converter (120).

[0061] In this embodiment, the isolated DC / DC converter (120) may include a DC / DC converter of the DAB (Dual-Active Bridge) type or the TAB (Triple-Active Bridge) type. These DABs and TABs are described in FIG. 4.

[0062] ESS (130) receives and stores DC voltage converted from multiple insulated DC / DC converters (120). The storage capacity of ESS (130) will be determined according to the capacity of MMC (110).

[0063] In the case of the E-STATCOM (100) of the present invention configured as described above, the AC section connects multiple sub-modules (140) in series to create a high voltage, and the low-voltage DC section connects the output of an insulated DC / DC converter (120) in parallel to the ESS (130).

[0064] Through this structure, reactive power can be generated by controlling the high voltage of the DC link of the sub-module (140) in the same way as the existing STATCOM, and active power can be generated through the energy stored in the ESS (130).

[0065] In addition, in the case of the E-STATCOM (100) of the present invention, since the ESS (130) is connected at low voltage, there is no need to consider high insulation performance, and by configuring the ESS (130) as a large capacity, there is a great advantage in that power can be transmitted for a long period of time.

[0066] Figure 4 is a configuration diagram of an insulated DC / DC converter according to an embodiment of the present invention.

[0067] Referring to FIG. 4, in the case of a semiconductor transformer such as an AC / DC converter (110) according to the present invention, the structure of the internal sub-module (140) can be combined in various ways.

[0068] For example, since the AC / DC converter (110) and the insulated DC / DC converter (120) are directly connected, the structure of the sub-module (140) is configured as a bidirectional insulated ISOP (P (Input Series-Output Parallel) structure so that the input terminal of the insulated DC / DC converter (120) generates high voltage and low current, and the output terminal generates low voltage and high current.

[0069] In Fig. 4, (a) is a DAB type insulated DC / DC converter with a bidirectional insulated ISOP structure, and (b) is a TAB type insulated DC / DC converter with a bidirectional insulated ISOP structure.

[0070] Referring to (a) of Fig. 4, a primary DC / DC converter (121) is formed by connecting a plurality of semiconductor switch elements (21) in a bridge form to form a primary input terminal, and is connected to a secondary DC / DC converter (123) of an output terminal through a transformer (122). Similarly, the secondary DC / DC converter (123) is formed by connecting a plurality of semiconductor switches (21) in a bridge form.

[0071] Accordingly, the insulated DC / DC converter (120) is configured as a DAB type. At this time, in the case of the insulated DC / DC converter (120) of the DAB type, there is one bridge on the primary side of the transformer (122).

[0072] Referring to (b) of Fig. 4, a primary DC / DC converter (121) is formed by connecting a plurality of semiconductor switch elements (21) in the form of two bridges to form a primary input terminal, and is connected to a secondary DC / DC converter (123) of an output terminal through a transformer (122). The secondary DC / DC converter (123) is formed by connecting a plurality of semiconductor switches (21) in the form of one bridge.

[0073] Accordingly, the insulated DC / DC converter (120) is configured as a TAB type. At this time, in the case of the insulated DC / DC converter (120) of the TAB type, there are two bridges on the primary side of the transformer (122).

[0074] In the case of the DAB type, since there is only one primary bridge, there may be a limit to increasing the internal pressure of the submodule depending on the internal pressure of the semiconductor switch element.

[0075] In contrast, the TAB type implements the primary side with two bridges in series, so that a higher voltage can be generated even if the withstand voltage of the semiconductor switch element is low. This has the advantage of reducing the number of sub-modules of a semiconductor transformer such as an MMC compared to the DAB type.

[0076] Therefore, in the embodiment of the present invention, the insulated DC / DC converter (120) can be implemented as a DAT type, but for the above reasons, it is more preferable to implement it as a TAB type.

[0077] In fact, when using the same power semiconductor module on the primary side in an isolated DC / DC converter (120), the TAB type can have an advantage in terms of higher power density and price by reducing the number of sub-modules by half compared to the DAB type. However, this is limited to cases where the capacity of the power module on the secondary side can transmit more than twice the capacity of the primary power module.

[0078] Although embodiments of the present invention have been described with reference to the attached drawings, the present invention is not limited to the above embodiments, but can be manufactured in various different forms. Those skilled in the art to which the present invention pertains will understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential characteristics of the present invention. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

Claims

1. Multiple AC / DC converters that are connected in series with each other and each convert AC voltage supplied from the smart grid into DC voltage; A plurality of isolated DC / DC converters, each connected in series to the plurality of AC / DC converters and converting a high-voltage DC voltage output from the AC / DC converters into a relatively low-voltage DC voltage; It includes an energy storage device (ESS) that stores low-voltage DC voltages output from each of the above-mentioned multiple insulated DC / DC converters, The above-mentioned isolated DC / DC converter is a static active / reactive power compensation device that includes a transformer and physically insulates the primary high-voltage side and the secondary low-voltage side of the transformer.

2. In claim 1, The above-mentioned insulated DC / DC converter is a stationary active / reactive power compensation device that outputs high voltage and low current at the input terminal as low voltage and high current at the output terminal.

3. In claim 1, The above-mentioned isolated DC / DC converter is a stationary active / reactive power compensation device having a DAB (Dual-Active Bridge) structure.

4. In claim 1, The above-mentioned isolated DC / DC converter is a stationary active / reactive power compensation device having a TAB (Triple-Active Bridge) structure.

5. In claim 1, A stationary active / reactive power compensation device that generates active power using the voltage stored in the above energy storage device (ESS) and transmits it to the grid.

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