Energy storage fusion type unified power flow controller topological structure

Abstract

The invention discloses a topological structure of an energy storage fusion type unified power flow controller. The topological structure comprises a boosting transformer T, a parallel transformer T1, a series transformer T2, an energy storage type series converter B-SEC and an energy storage type parallel converter B-SHC. According to the energy storage fusion type unified power flow controller, an extra high-power isolation type direct-current transformer does not need to be connected into a power distribution system, and the power conversion link is reduced; the wooden barrel effect caused by centralized configuration of the energy storage unit and series-parallel connection of the batteries in the low-voltage direct-current bus is avoided, and the equipment capacity ratio is fully utilized; and furthermore, the battery management system is greatly simplified, the self-detection time of the battery cell cluster is shortened, and the dynamic response speed of the whole system is improved. Therefore, the technical problems that in the prior art, the system cost is high, multi-stage operation regulation and control are complex, fault protection cannot meet requirements, and the system response speed is low are solved.

Description

Technical Field

[0001] This invention relates to the field of power flow control technology, and in particular to a unified power flow controller topology with energy storage integration. Background Technology

[0002] Under the "dual carbon" target, the continuous grid connection of large-scale, fluctuating, and intermittent wind and solar renewable energy power plants has made power system operation increasingly complex, posing new challenges to its stable operation. The Unified Power Flow Controller (UPFC) possesses multiple functions, including voltage regulation, impedance compensation, phase angle compensation, and comprehensive power flow regulation, and has become one of the most advanced flexible AC transmission devices available today. With the development of fully controlled power electronic devices, the Modular Multilevel Converter (MMC) can output high power, high voltage, and boasts high reliability and power density, and is now widely used in UPFC system architectures. To better address the power fluctuations and renewable energy consumption issues brought about by large-scale renewable energy grid integration, scholars and research institutions have proposed a UPFC system architecture equipped with a battery energy storage system. This architecture aims to solve the problem of fluctuating power from renewable energy generation flowing into the main grid. The specific system topology is as follows: Figure 4 As shown.

[0003] To address the power output fluctuations of renewable energy power plants and the power flow regulation issues of the transmission system, UPFC (Upgraded Power Controller) devices are connected to the grid connection point of large-scale wind and solar renewable energy power plants. One AC interface of the UPFC series converter is connected to the traditional AC power grid or a remote load; the UPFC parallel converter is connected to the convergence boost connection point of the wind and solar renewable energy power plant; and the battery energy storage system is connected to the UPFC back-to-back common DC bus via a DC transformer. Compared to the common DC bus support typically used by UPFCs, its active power regulation is negligible. Placing an energy storage battery system on the common DC side of the UPFC further enhances its power flow regulation capabilities. When renewable energy power plants experience power mismatch due to excessive or insufficient power generation, the battery energy storage system can absorb or compensate for the energy difference. Furthermore, the energy storage unit can maintain the grid current at the active component of the load current under normal operating conditions, avoiding the increase in feeder current when the power supply voltage drops, eliminating the risk of overcurrent in the grid feeders, and effectively reducing the capacity configuration of the UPFC to a certain extent. Therefore, combining the power flow control capability of UPFC with the energy absorption capability of energy storage systems may create a multifunctional and deeply integrated power transmission equipment.

[0004] However, configuring a centralized battery energy storage system requires an isolated DC transformer and a large number of DC / DC converters to be introduced into the UPFC device, which poses significant challenges to the overall system cost, operation control, and fault protection. Furthermore, while battery energy storage is configured at the low-voltage DC bus port, its capacity is generally limited to below 500kW due to factors such as the battery management system (BMS) and battery pack configuration. Configuring larger capacity battery energy storage at the low-voltage DC port requires expansion through parallel operation of multiple units. However, parallel operation of multiple units leads to complex control systems prone to stability issues and significantly reduces system response speed. Summary of the Invention

[0005] This invention provides a unified power flow controller topology with integrated energy storage to address the problems of high cost, inadequate operation control and fault protection, and low system response speed in existing technologies.

[0006] In view of this, the first aspect of the present invention provides a unified power flow controller topology with energy storage integration, including: a step-up transformer T, a parallel transformer T1, a series transformer T2, an energy storage series converter B-SEC, and an energy storage parallel converter B-SHC;

[0007] The port of the low-voltage side winding of the step-up transformer T is connected to the low-voltage AC bus, and the port of the high-voltage side winding of the step-up transformer T is connected to the high-voltage AC bus.

[0008] The port of the high-voltage winding of the parallel transformer T1 is connected to the port of the low-voltage winding of the step-up transformer T.

[0009] The AC side port of the energy storage parallel converter B-SHC is connected to the low-voltage winding port of the parallel transformer T1; the energy storage parallel converter B-SHC and the energy storage series converter B-SEC are connected back-to-back; the DC side of the energy storage parallel converter B-SHC and the DC side of the energy storage series converter B-SEC are provided with capacitor support.

[0010] The high-voltage winding of the series transformer T2 is connected in series with the high-voltage AC bus, and the port of the low-voltage winding of the series transformer T2 is connected to the AC side port of the energy storage series converter B-SEC; and a bypass switch is connected in parallel to the high-voltage winding of the series transformer T2 for controlling the series transformer. On / off of the high-voltage side winding.

[0011] Optionally, the step-up transformer T includes: three high-voltage side windings W A W B WC and three low-voltage side windings W a W b W c Furthermore, the high-voltage side leads out three-phase ports A, B, and C, which are connected to the high-voltage AC bus. The low-voltage side leads out three-phase ports A3, B3, and C3, which are connected to the low-voltage AC bus.

[0012] Optionally, the parallel transformer T1 includes: three high-voltage side windings W A1 W B1 W C1 and three low-voltage side windings W a1 W b1 W c1 ;

[0013] The high-voltage side winding of phase A of the parallel transformer T1 includes... , Two ports, the B-phase high-voltage side winding includes , Two ports, the C-phase high-voltage side winding includes , Two ports, and three ports , as well as The connection forms the midpoint; simultaneously, the high-voltage side winding W of the parallel transformer T1 A1 same name The high-voltage winding W of the parallel transformer T1 is connected to port A3. B1 same name The high-voltage winding W of the parallel transformer T1 is connected to port B3. C1 same name With port Connected;

[0014] The A-phase low-voltage side winding of the parallel transformer T1 includes , Two ports, B-phase low-voltage side winding includes , Two ports, C-phase low-voltage side winding includes , Two ports, and three ports , as well as Connecting them forms the midpoint.

[0015] Optionally, the energy storage parallel converter B-SHC and the energy storage series converter B-SEC are connected back-to-back, specifically:

[0016] The DC side port V of the energy storage parallel converter B-SHC dc1+The DC side port V of the energy storage series converter B-SEC dc2+ Connected; the DC side port V of the energy storage parallel converter E-SHC dc1- With the DC side port V of the energy storage series converter E-SEC dc2- Connected.

[0017] Optionally, the AC side of the energy storage parallel converter B-SHC includes three ports: A4, B4, and C4, wherein port A4 is connected to the low-voltage winding W of the parallel transformer T1. a1 same name Connected, port B4 is connected to the low-voltage winding W of the parallel transformer T1. b1 same name Connected, port C4 is connected to the low-voltage winding W of the parallel transformer T1. c1 same name Connected;

[0018] The energy storage type series converter B-SEC includes three ports: A5, B5, and C5. Port A5 is connected to the low-voltage winding W of the series transformer T2. a2 same name Connected, port B5 is connected to the low-voltage winding W of series transformer T2. b2 same name Connected, port C5 is connected to the low-voltage winding W of the series transformer T2. c2 same name Connected;

[0019] A capacitor is connected in parallel between the DC side of the energy storage parallel converter B-SHC and the DC side of the energy storage series converter B-SEC.

[0020] Optionally, the series transformer T2 includes: W A2 W B2 W C2 Three high-voltage side windings and W a2 W b2 W c2 Three low-voltage side windings;

[0021] Among them, the high-voltage side winding W A2 Connected in series with the A-phase AC busbar, the high-voltage side winding W B2 Connected in series with the B-phase AC busbar, the high-voltage side winding W C2 Connected in series with the C-phase AC busbar;

[0022] The high-voltage winding W of the series transformer T2 A2 W B2 W C2 Both ends are equipped with high-voltage side bypass switches Sa S b S c ;

[0023] The low-voltage side winding of phase A of the series transformer T2 includes , Two ports, B-phase low-voltage side winding includes , Two ports, C-phase low-voltage side winding includes , Two ports, of which , , The three ports are connected to form the midpoint of the low-voltage side winding.

[0024] Optionally, the high-voltage windings of the step-up transformer T are connected in a Yn-type connection, and the low-voltage windings are connected in a Δ-type connection.

[0025] Optionally, the connection between the high-voltage windings of the parallel transformer T1 is a Yn-type connection, and the connection between the low-voltage windings of the parallel transformer T1 is a Yn-type connection.

[0026] Optionally, the low-voltage windings of the series transformer T2 are connected in a Yn-type connection.

[0027] Optionally, the control of the series transformer The switching of the high-voltage side winding includes:

[0028] When the bypass switch is open, the energy storage series converter B-SEC is connected in series with the grid side; when the bypass switch is closed, the energy storage series converter B-SEC is bypassed.

[0029] As can be seen from the above technical solutions, the present invention has the following advantages:

[0030] This invention provides a unified power flow controller topology with integrated energy storage, eliminating the need for additional high-power isolated DC transformers connected to the power distribution system, thus reducing power conversion stages. It also avoids the bottleneck effect caused by centralized energy storage units on the low-voltage DC bus and battery series-parallel connections, fully utilizing the equipment's capacity. Furthermore, the battery management system is significantly simplified, the cell cluster self-detection time is shortened, and the overall system's dynamic response speed is improved. This solves the technical problems of existing technologies, such as high system cost, complex multi-level operation and control, inadequate fault protection, and low system response speed. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This invention provides a unified power flow controller topology with integrated energy storage.

[0033] Figure 2 An operation scheme for an energy storage-integrated UPFC system is provided in this embodiment of the invention;

[0034] Figure 3 This is a schematic diagram of an energy storage series converter and an energy storage parallel converter topology provided in an embodiment of the present invention;

[0035] Figure 4 This is a diagram of the existing UPFC system architecture with a battery energy storage system. Detailed Implementation

[0036] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0037] Please see Figure 1 and Figure 2 The energy storage integrated unified power flow controller topology provided in this embodiment of the invention includes: a step-up transformer T, a parallel transformer T1, a series transformer T2, an energy storage series converter B-SEC, and an energy storage parallel converter B-SHC.

[0038] in:

[0039] The low-voltage side winding of the step-up transformer T is connected to the low-voltage AC bus, and the high-voltage side winding of the step-up transformer T is connected to the high-voltage AC bus.

[0040] In one embodiment, the step-up transformer T includes: three high-voltage side windings W A W B W C and three low-voltage side windings W a W b W cFurthermore, the high-voltage side has three-phase ports A, B, and C connected to the high-voltage AC bus, and the low-voltage side has three-phase ports A3, B3, and C3 connected to the low-voltage AC bus. The high-voltage windings of the step-up transformer T are connected in a Yn-type configuration, and the low-voltage windings are connected in a Δ-type configuration.

[0041] in:

[0042] The high-voltage winding of the parallel transformer T1 is connected to the low-voltage winding of the step-up transformer T.

[0043] In one embodiment, the parallel transformer T1 includes: three high-voltage side windings W A1 W B1 W C1 and three low-voltage side windings W a1 W b1 W c1 Among them, the high-voltage side winding of phase A of the parallel transformer T1 includes , Two ports, the B-phase high-voltage side winding includes , Two ports, the C-phase high-voltage side winding includes , Two ports, and three ports , as well as The midpoint is formed by the connection; simultaneously, the high-voltage winding W of the parallel transformer T1... A1 same name The high-voltage winding W of the parallel transformer T1 is connected to port A3. B1 same name The high-voltage winding W of the parallel transformer T1 is connected to port B3. C1 same name With port Connected; the low-voltage side winding of phase A of the parallel transformer T1 includes , Two ports, B-phase low-voltage side winding includes , Two ports, C-phase low-voltage side winding includes , Two ports, and three ports , as well as The connection forms the midpoint. Specifically, the high-voltage windings of the parallel transformer T1 are connected in a Yn-type configuration, as are the low-voltage windings.

[0044] in:

[0045] The AC side port of the energy storage parallel converter B-SHC is connected to the low-voltage winding port of the parallel transformer T1; the energy storage parallel converter B-SHC and the energy storage series converter B-SEC are connected back-to-back; the DC side of the energy storage parallel converter B-SHC and the DC side of the energy storage series converter B-SEC are equipped with capacitor support.

[0046] In one embodiment, the DC-side port V of the energy storage parallel converter B-SHC dc1+ With the DC side port V of the energy storage series converter B-SEC dc2+ Phase connection; DC side port V of the energy storage type parallel converter E-SHC dc1- With the DC side port V of the energy storage series converter E-SEC dc2- The energy storage parallel converter B-SHC has three AC ports: A4, B4, and C4. Port A4 is connected to the low-voltage winding W of the parallel transformer T1. a1 same name Connected, port B4 is connected to the low-voltage winding W of parallel transformer T1. b1 same name Connected, port C4 is connected to the low-voltage winding W of parallel transformer T1. c1 same name Connected; the energy storage type series converter B-SEC includes three ports: A5, B5, and C5. Among them, port A5 is connected to the low-voltage winding W of the series transformer T2. a2 same name Connected, port B5 is connected to the low-voltage winding W of series transformer T2. b2 same name Connected, port C5 is connected to the low-voltage winding W of series transformer T2. c2 same name A capacitor is connected in parallel between the DC side of the energy storage parallel converter B-SHC and the DC side of the energy storage series converter B-SEC; when the bypass switch is open, the energy storage series converter B-SEC is connected in series with the grid side; when the bypass switch is on, the energy storage series converter B-SEC is bypassed. Please refer to [link to relevant documentation]. Figure 1 and Figure 3 .

[0047] in:

[0048] The high-voltage winding of series transformer T2 is connected in series with the high-voltage AC bus, and the port of the low-voltage winding of series transformer T2 is connected to the AC side port of energy storage series converter B-SEC; and a bypass switch is connected in parallel to the high-voltage winding of series transformer T2 for controlling the series transformer. On / off of the high-voltage side winding.

[0049] In one embodiment, the series transformer T2 includes: W A2 W B2 W C2 Three high-voltage side windings and W a2 W b2 W c2 Three low-voltage side windings; of which, the high-voltage side winding W A2 Connected in series with the A-phase AC busbar, the high-voltage side winding W B2 Connected in series with the B-phase AC busbar, the high-voltage side winding W C2 Connected in series with the C-phase AC busbar; the high-voltage side winding W of the series transformer T2 A2 W B2 W C2 Both ends are equipped with high-voltage side bypass switches S a S b S c The low-voltage side winding of phase A of series transformer T2 includes... , Two ports, B-phase low-voltage side winding includes , Two ports, C-phase low-voltage side winding includes , Two ports, of which , , The three ports are connected to form the midpoint of the low-voltage side winding. The connection method between the low-voltage side windings of the series transformer T2 is a Yn type connection.

[0050] This invention provides an energy storage-integrated unified power flow controller topology. A step-up transformer T increases the input voltage to a suitable level to meet the operational requirements of subsequent equipment. The parallel transformer T1 primarily functions to exchange and regulate reactive power, flexibly injecting or absorbing reactive power into the grid based on its operating status, thereby improving voltage quality and grid stability. The series transformer T2 works in conjunction with the energy storage-type series converter B-SEC, achieving precise control of active and reactive power by altering the equivalent impedance of the transmission line. The energy storage-type series converter B-SEC possesses rapid power response capabilities, quickly adjusting its output power according to the system's real-time demands. When power fluctuations occur in the transmission line, the energy storage-type series converter B-SEC can promptly release stored energy into the line or absorb excess energy from the line, effectively suppressing power fluctuations and improving the power transmission capacity of the transmission line. The energy storage-type parallel converter B-SHC, in conjunction with the parallel transformer T1, can store excess energy in the system on the one hand, and release the stored energy when the system needs it on the other hand, providing emergency support for the power grid.

[0051] Through the coordinated operation of its components, the energy storage-integrated unified power flow controller of this invention enables flexible and efficient control of power grid flow, improving grid operating efficiency and stability, and adapting to different grid operating conditions. More importantly, it eliminates the need for additional high-power isolated DC transformers connected to the distribution system, reducing power conversion stages; it also avoids the bottleneck effect caused by centralized configuration of energy storage units on the low-voltage DC bus and battery series-parallel connections, fully utilizing the equipment's capacity rate; furthermore, the battery management system is significantly simplified, cell self-detection time is shortened, and the dynamic response speed of the entire system is improved. This solves the problems of high cost, inadequate operation control and fault protection, and low system response speed found in existing technologies.

[0052] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A unified power flow controller topology with energy storage integration, characterized in that, include: Step-up transformer T, parallel transformer T1, series transformer T2, energy storage series converter B-SEC, and energy storage parallel converter B-SHC; The port of the low-voltage side winding of the step-up transformer T is connected to the low-voltage AC bus, and the port of the high-voltage side winding of the step-up transformer T is connected to the high-voltage AC bus. The port of the high-voltage winding of the parallel transformer T1 is connected to the port of the low-voltage winding of the step-up transformer T. The AC side port of the energy storage parallel converter B-SHC is connected to the low-voltage winding port of the parallel transformer T1; the energy storage parallel converter B-SHC and the energy storage series converter B-SEC are connected back-to-back; the DC side of the energy storage parallel converter B-SHC and the DC side of the energy storage series converter B-SEC are provided with capacitor support. The high-voltage winding of the series transformer T2 is connected in series with the high-voltage AC bus, and the port of the low-voltage winding of the series transformer T2 is connected to the AC side port of the energy storage series converter B-SEC; and a bypass switch is connected in parallel to the high-voltage winding of the series transformer T2 for controlling the series transformer. On / off of the high-voltage side winding.

2. The energy storage-integrated unified power flow controller topology according to claim 1, characterized in that, The step-up transformer T includes: three high-voltage side windings W A W B W C and three low-voltage side windings W a W b W c Furthermore, the high-voltage side leads out three-phase ports A, B, and C, which are connected to the high-voltage AC bus. The low-voltage side leads out three-phase ports A3, B3, and C3, which are connected to the low-voltage AC bus.

3. The energy storage-integrated unified power flow controller topology according to claim 2, characterized in that, The parallel transformer T1 includes: three high-voltage side windings W A1 W B1 W C1 and three low-voltage side windings W a1 W b1 W c1 ; The high-voltage side winding of phase A of the parallel transformer T1 includes... , Two ports, the B-phase high-voltage side winding includes , Two ports, the C-phase high-voltage side winding includes , Two ports, and three ports , as well as The connection forms the midpoint; simultaneously, the high-voltage side winding W of the parallel transformer T1 A1 same name The high-voltage winding W of the parallel transformer T1 is connected to port A3. B1 same name The high-voltage winding W of the parallel transformer T1 is connected to port B3. C1 same name With port Connected; The A-phase low-voltage side winding of the parallel transformer T1 includes , Two ports, B-phase low-voltage side winding includes , Two ports, C-phase low-voltage side winding includes , Two ports, and three ports , as well as Connecting them forms the midpoint.

4. The energy storage-integrated unified power flow controller topology according to claim 3, characterized in that, The energy storage parallel converter B-SHC and the energy storage series converter B-SEC are connected back-to-back, specifically: The DC side port V of the energy storage parallel converter B-SHC dc1+ The DC side port V of the energy storage series converter B-SEC dc2+ Connected; the DC side port V of the energy storage parallel converter E-SHC dc1- With the DC side port V of the energy storage series converter E-SEC dc2- Connected.

5. The energy storage-integrated unified power flow controller topology according to claim 4, characterized in that, The AC side of the energy storage parallel converter B-SHC includes three ports: A4, B4, and C4. Port A4 is connected to the low-voltage winding W of the parallel transformer T1. a1 same name Connected, port B4 is connected to the low-voltage winding W of the parallel transformer T1. b1 same name Connected, port C4 is connected to the low-voltage winding W of the parallel transformer T1. c1 same name Connected; The energy storage type series converter B-SEC includes three ports: A5, B5, and C5. Port A5 is connected to the low-voltage winding W of the series transformer T2. a2 same name Connected, port B5 is connected to the low-voltage winding W of series transformer T2. b2 same name Connected, port C5 is connected to the low-voltage winding W of the series transformer T2. c2 same name Connected; A capacitor is connected in parallel between the DC side of the energy storage parallel converter B-SHC and the DC side of the energy storage series converter B-SEC.

6. The energy storage-integrated unified power flow controller topology according to claim 5, characterized in that, The series transformer T2 includes: W A2 W B2 W C2 Three high-voltage side windings and W a2 W b2 W c2 Three low-voltage side windings; Among them, the high-voltage side winding W A2 Connected in series with the A-phase AC busbar, the high-voltage side winding W B2 Connected in series with the B-phase AC busbar, the high-voltage side winding W C2 Connected in series with the C-phase AC busbar; The high-voltage winding W of the series transformer T2 A2 W B2 W C2 Both ends are equipped with high-voltage side bypass switches S a S b S c ; The low-voltage side winding of phase A of the series transformer T2 includes , Two ports, B-phase low-voltage side winding includes , Two ports, C-phase low-voltage side winding includes , Two ports, of which , , The three ports are connected to form the midpoint of the low-voltage side winding.

7. The energy storage-integrated unified power flow controller topology according to claim 1 or 2, characterized in that, The high-voltage windings of the step-up transformer T are connected in a Yn-type connection, and the low-voltage windings are connected in a Δ-type connection.

8. The energy storage-integrated unified power flow controller topology according to claim 1 or 3, characterized in that, The high-voltage windings of the parallel transformer T1 are connected in a Yn-type configuration, and the low-voltage windings of the parallel transformer T1 are also connected in a Yn-type configuration.

9. The energy storage-integrated unified power flow controller topology according to claim 1 or 6, characterized in that, The low-voltage windings of the series transformer T2 are connected in a Yn-type configuration.

10. The energy storage-integrated unified power flow controller topology according to claim 1, characterized in that, The control of the series transformer The switching of the high-voltage side winding includes: When the bypass switch is open, the energy storage series converter B-SEC is connected in series with the grid side; when the bypass switch is closed, the energy storage series converter B-SEC is bypassed.

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