Combined power flow controller
By designing a combined power flow controller and coordinating the control of phase-shifting transformers and series converters, high-precision power flow regulation and short-circuit current limiting are achieved, solving the problems of high cost and short-circuit current limiting of existing power flow controllers, and improving the economy and flexibility of the power system.
Patent Information
- Application Number
- CN202511405934.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-29
- Publication Date
- 2026-02-10
AI Technical Summary
Existing power flow controllers suffer from high investment costs, large operating losses, and an inability to effectively limit short-circuit current when regulating power flow in the grid. In particular, when facing the increased uncertainty of the power system after the integration of new energy sources into the grid, traditional equipment is unable to meet the requirements for flexible regulation and short-circuit current limitation.
A combined power flow controller is adopted, which combines a phase-shifting transformer, a series converter, and a passive AC fast switch to achieve wide-range, high-precision voltage regulation through coordinated control. It also blocks short-circuit current during short-circuit faults. The controller includes a phase-shifting transformer with a dual-core symmetrical or asymmetrical structure and a voltage source type submodule, which works in conjunction with a passive AC fast switch to limit short-circuit current.
It achieves high-precision power flow control and short-circuit current limiting, reduces equipment costs, and improves the economy and flexibility of the power system, making it suitable for practical engineering applications.
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Figure CN121507760A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of power flow controller, and particularly relates to a combined power flow controller. BACKGROUND
[0002] With the increasing demand for power load, the problems of power transmission corridor power flow congestion and short-circuit current level rising are becoming more and more serious. Especially in recent years, large-scale new energy units are connected to the grid, which requires the power system to operate more flexibly, and the power flow distribution of the power system is therefore more uncertain.
[0003] In engineering practice, the power flow controller is a key device for actively adjusting the power flow of the power grid. The technical route of the existing power flow controller mainly includes electromagnetic power flow controllers represented by phase-shifting transformers and power electronic power flow controllers represented by unified power flow controllers. The former adjusts by controlling the tap position, and the tap position is limited, which belongs to discrete adjustment mode; the voltage adjustment step of the latter is determined by the sub-module capacitor voltage, which is approximately continuous adjustment, but a large number of power electronic switching devices lead to high investment cost and large operation loss.
[0004] In addition, the electromagnetic power flow controller and the unified power flow controller cannot effectively limit the line short-circuit current, and when the short-circuit current level exceeds the standard, a current limiting device needs to be additionally installed.
[0005] Therefore, it is necessary to study a new type of flexible alternating current transmission device which can provide wide-range high-precision power flow control capability, and its manufacturing cost is less than that of the conventional unified power flow controller, and also has short-circuit current limiting capability to improve the economy of the power system. SUMMARY
[0006] The present application provides a combined power flow controller, which has the economic advantages of low cost and large capacity of the electromagnetic power flow controller and the technical advantages of flexible control and rapid response of the power electronic power flow controller, and also limits the short-circuit current by setting a passive AC fast switch, which is an economical and efficient new type of flexible alternating current transmission device, and has engineering practical significance.
[0007] To achieve the above purpose, the technical scheme adopted by the present application is as follows: the combined power flow controller comprises:
[0008] a phase-shifting transformer;
[0009] a series current converter;
[0010] a passive AC fast switch;
[0011] The phase-shifting transformer adopts a double-core symmetric structure or a double-core asymmetric structure, and comprises an excitation transformer unit and a series transformer unit.
[0012] The combined power flow controller comprises a phase-shifting transformer, a series current converter and a passive AC fast switch.
[0013] As an improvement, the primary winding of the excitation transformer unit of the phase-shifting transformer adopts a star connection, and the neutral point is grounded.
[0014] As an improvement, the secondary winding of the excitation transformer unit of the phase-shifting transformer adopts a star connection, and the neutral point is not grounded.
[0015] The secondary winding of the series transformer unit adopts an angular connection, the positive polarity end of each phase secondary winding is connected to the negative polarity end of the adjacent lagging phase secondary winding, and each phase outgoing line is led out from the positive polarity end of the same phase secondary winding.
[0016] The outgoing line of each phase secondary winding of the excitation transformer unit is connected to the outgoing line of the adjacent leading phase secondary winding of the series transformer unit.
[0017] As an improvement, the secondary winding of the excitation transformer unit of the phase-shifting transformer is a voltage regulating winding, and is provided with a load regulating switch.
[0018] As an improvement, each phase of the series current converter comprises at least one voltage source type sub-module, and the output ends of the voltage source type sub-modules are connected in series.
[0019] As an improvement, the voltage source type sub-module adopts a topology structure having a bipolar voltage output capability.
[0020] As an improvement, the combined power flow controller according to claim 1, characterized in that the passive AC fast switch comprises a break module and two current-limiting modules, the break module and the current-limiting modules are connected in series, and the break module is located between the two current-limiting modules.
[0021] As an improvement, the current-limiting module comprises a current-limiting resistor and a fast mechanical switch, and the current-limiting resistor and the fast mechanical switch are connected in parallel.
[0022] As an improvement, the break module comprises a conducting branch, a transfer branch and an energy consumption branch connected in parallel, the conducting branch is provided with a fast mechanical switch, the transfer branch is provided with an inductor and a capacitor connected in series, and the energy consumption branch is provided with a lightning arrester.
[0023] As an improvement, during normal operation, the fast mechanical switches in the current-limiting modules and the break module of the passive AC fast switch are in the closed state, the current-limiting resistor of the current-limiting module and the transfer branch and the energy consumption branch of the break module are bypassed; when the high-voltage AC line fails, the fast mechanical switch in the current-limiting module is opened, the current-limiting resistor is put into operation to limit the amplitude of the short-circuit current, the fast mechanical switch of the break module is opened, and the transfer branch and the energy consumption branch are put into operation to quickly block the short-circuit current.
[0024] The combined power flow controller has the advantages that: through the coordinated control of the phase-shifting transformer and the series current converter, large-range high-precision voltage regulation operation is completed, line power flow flexible control is realized, the passive AC fast switch is provided to realize short-circuit current blocking, and the system short-circuit current level can be effectively limited. BRIEF DESCRIPTION OF DRAWINGS
[0025] Figure 1 FIG. 1 is a structural schematic diagram of the combined power flow controller according to the first embodiment of the present application.
[0026] Figure 2 FIG. 2 is a topological structure schematic diagram of the phase-shifting transformer of the combined power flow controller according to the first embodiment of the present application.
[0027] Figure 3 FIG. 3 is a typical topological schematic diagram of the voltage source type sub-module of the combined power flow controller according to the first embodiment of the present application.
[0028] Figure 4 FIG. 4 is a principle diagram of regulating line power flow of the combined power flow controller according to the first embodiment of the present application.
[0029] Figure 5 FIG. 5 is a topological structure schematic diagram of the passive AC fast switch of the combined power flow controller according to the first embodiment of the present application. DETAILED DESCRIPTION
[0030] The technical solutions of the embodiments of the application are explained and described below, but the following embodiments are only preferred embodiments of the application, not all.
[0031] Referring to Figures 1 to 5 The combined power flow controller of the embodiment of the application comprises:
[0032] The phase-shifting transformer;
[0033] The series current converter;
[0034] The passive AC fast switch;
[0035] The phase-shifting transformer adopts a double-core symmetric structure or a double-core asymmetric structure, and comprises an excitation transformer unit and a series transformer unit.
[0036] The combined power flow controller of the application comprises a phase-shifting transformer, a series current converter and a passive AC fast switch, and a large-range high-precision voltage regulation operation is completed through coordinated control of the phase-shifting transformer and the series current converter, line power flow is flexibly controlled, a short-circuit current is blocked through the passive AC fast switch, and the system short-circuit current level can be effectively limited.
[0037] Embodiment one
[0038] Referring to Figures 1 to 5 The combined power flow controller of the embodiment one of the application comprises:
[0039] The phase-shifting transformer;
[0040] The series current converter;
[0041] The passive AC fast switch;
[0042] The phase-shifting transformer adopts a double-core symmetric structure or a double-core asymmetric structure, and comprises an excitation transformer unit and a series transformer unit.
[0043] Referring to Figure 1, the combined tide controller of the embodiment one of the present application. In the embodiment, the combined tide controller is composed of a phase-shifting transformer, a series current converter and a passive AC fast switch, wherein the phase-shifting transformer adopts a double-core symmetric structure or a double-core asymmetric structure, and the phase-shifting transformer is composed of parallel transformer units (parallel transformers, field transformers) and series transformer units (series transformers). The primary winding of the series transformer unit is connected in series with the series current converter and the passive AC fast switch and then connected to a high-voltage AC line, wherein the phase-shifting transformer is located close to one end of an AC bus, and the passive AC fast switch is located close to one end of an AC outgoing line.
[0044] Referring to Figure 2 , the topological structure diagram of the phase-shifting transformer of the embodiment one of the present application. In the diagram, one end of the primary and secondary winding of the transformer is a positive polarity end, and the other end is a negative polarity end. The primary winding of the field transformer unit of the phase-shifting transformer adopts a star connection, and the neutral point is grounded. The connection mode of the outgoing line end of each phase with the primary winding of the series transformer unit is related to the structure of the phase-shifting transformer. When the phase-shifting transformer adopts a double-core symmetric structure, the outgoing line end of each phase of the primary winding of the field transformer unit is connected with the intermediate tap of the primary winding of the same phase of the series transformer unit, as shown in (a). When the phase-shifting transformer adopts a double-core asymmetric structure, the outgoing line end of each phase of the primary winding of the field transformer unit of the phase-shifting transformer is connected with the positive polarity end of the primary winding of the same phase of the series transformer unit, as shown in (b). Figure 2 Figure 2
[0045] The secondary winding of the field transformer unit of the phase-shifting transformer adopts a star connection, and the neutral point is not connected to electricity. The secondary winding of the series transformer unit adopts an angular connection, the positive polarity end of each phase of the secondary winding is connected with the negative polarity end of the adjacent lagging phase of the secondary winding, and the outgoing line end of each phase is led out from the positive polarity end of the same phase of the secondary winding. Specifically, the positive polarity end of the secondary winding a phase of the series transformer unit is connected with the negative polarity end of the secondary winding b phase, the positive polarity end of the secondary winding b phase is connected with the negative polarity end of the secondary winding c phase, and the positive polarity end of the secondary winding c phase is connected with the negative polarity end of the secondary winding a phase; the outgoing line end of the secondary winding a, b and c phases of the series transformer unit is led out from the positive polarity end of the secondary winding a, b and c phases, respectively.
[0046] The outgoing line end of each phase of the secondary winding of the field transformer unit is connected with the outgoing line end of the adjacent leading phase of the secondary winding of the series transformer unit. Specifically, the outgoing line end of the secondary winding a phase of the field transformer unit is connected with the outgoing line end of the secondary winding c phase of the series transformer unit, the outgoing line end of the secondary winding b phase of the field transformer unit is connected with the outgoing line end of the secondary winding a phase of the series transformer unit, and the outgoing line end of the secondary winding c phase of the field transformer unit is connected with the outgoing line end of the secondary winding b phase of the series transformer unit.
[0047] The secondary winding of the excitation transformer unit of the phase-shifting transformer is a voltage regulating winding, and a load voltage regulating switch is arranged.
[0048] Referring to Figure 3 , the voltage source type sub-module typical topology diagram of the embodiment one of the application. In this embodiment, each phase of the series current converter is composed of at least one voltage source type sub-module, and the output ends of each voltage source type sub-module are connected in series. The sub-module needs to adopt a topology with bipolar voltage output capability, and its typical representatives are Figure 3 (1) full-bridge sub-module shown in the figure or Figure 3 (2) clamped double sub-module shown in the figure.
[0049] Referring to Figure 4 , the principle diagram of the combined power flow controller regulating line power flow of the embodiment one of the application, which uses a double-core asymmetric phase-shifting transformer for principle illustration. In the figure is the initial voltage phasor of the installation point of the combined power flow controller, is the node voltage target phasor obtained through power flow optimization calculation, and represent the output voltage phasor boundary. After receiving instruction, the combined power flow controller first realizes large step voltage regulation through the on-load voltage regulating switch (tap) of the phase-shifting transformer, and then realizes small step voltage regulation through the switching of each phase sub-module of the series current converter. In steady state, the output voltage phasor of the series current converter leads or lags the line current phasor by 90°, and each phase sub-module of the series current converter does not absorb or release active power from the outside to maintain the stability of the sub-module capacitor voltage.
[0050] Referring to Figure 5 , the topological structure schematic diagram of the passive AC fast switch of the embodiment one of the application. In this embodiment, the passive AC fast switch includes a switching module and two current limiting modules, and the switching module and the current limiting modules are connected in series, and each of the two ends of the switching module is provided with a current limiting module. The current limiting module includes a current limiting resistor and a fast mechanical switch, and the two ends of the current limiting resistor are connected in parallel with the fast mechanical switch. The switching module includes a conduction branch, a transfer branch and an energy consumption branch connected in parallel, wherein the conduction branch is provided with a fast mechanical switch, the transfer branch is provided with a series inductor and a capacitor, and the energy consumption branch is provided with a lightning arrester. During normal operation, the fast mechanical switches in the current limiting modules and the switching module of the passive AC fast switch are in the closed state, and the current limiting resistor of the current limiting module and the transfer branch and the energy consumption branch of the switching module are bypassed; when a high-voltage AC line fault occurs, the fast mechanical switch in the current limiting module is opened, and the current limiting resistor is put into operation to limit the short-circuit current peak value, and the fast mechanical switch of the switching module is opened, and the transfer branch and the energy consumption branch are put into operation to quickly block the short-circuit current.
[0051] The combination type tide flow controller has the advantages that the phase-shifting transformer, the series current converter and the passive AC fast switch are arranged, the wide-range high-precision voltage regulation operation is completed through the coordinated control of the phase-shifting transformer and the series current converter, the line tide flow is flexibly controlled, the short-circuit current is blocked through the passive AC fast switch, the system short-circuit current level can be effectively limited, the function is strong, the economy is good, and the combination type tide flow controller has the application value in the actual engineering construction.
[0052] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited to this. Those skilled in the art should understand that the present application includes but is not limited to the above specific embodiments. Any modification that does not deviate from the functional and structural principles of the present application will be included in the scope of the claims.
Claims
1. A combined power flow controller, characterized in that: The combined power flow controller includes: Phase-shifting transformer; Series converter; Passive AC quick switch; The phase-shifting transformer adopts a dual-core symmetrical structure or a dual-core asymmetrical structure. The phase-shifting transformer includes an excitation transformer unit and a series transformer unit. The primary winding of the series transformer unit is connected in series with the series converter and the passive AC fast switch and then connected to the high-voltage AC line.
2. The combined power flow controller according to claim 1, characterized in that: The primary winding of the excitation transformer unit of the phase-shifting transformer adopts a star connection and is grounded on the neutral point side; When the phase-shifting transformer adopts a dual-core symmetrical structure, the output terminals of each phase of the primary winding of the excitation transformer unit are connected to the intermediate taps of the primary windings of the same phase of the series transformer unit. When the phase-shifting transformer adopts a dual-core asymmetric structure, the output terminals of each phase of the primary winding of the excitation transformer unit are connected to the positive polarity terminals of the primary winding of the series transformer unit.
3. The combined power flow controller according to claim 1, characterized in that: The secondary winding of the excitation transformer unit of the phase-shifting transformer adopts a star connection and the neutral point is not grounded; The secondary windings of the series transformer unit are connected in a delta configuration. The positive polarity of each phase secondary winding is connected to the negative polarity of the adjacent lagging phase secondary winding, and the output terminals of each phase are led out from the positive polarity of the same phase secondary winding. Each phase output terminal of the secondary winding of the excitation transformer unit is connected to the adjacent leading phase output terminal of the secondary winding of the series transformer unit.
4. The combined power flow controller according to claim 1, characterized in that: The secondary winding of the excitation transformer unit of the phase-shifting transformer is a voltage regulating winding and is equipped with an on-load tap changer; When adjusting the transmission power of a line, the combined power flow controller first performs coarse adjustment by adjusting the on-load tap changer of the phase-shifting transformer, and then performs fine adjustment by controlling the output voltage of the series converter. Under steady-state conditions, the output voltage phasor of the series converter leads or lags the line current phasor by 90°.
5. The combined power flow controller according to claim 1, characterized in that: Each phase of the series converter includes at least one voltage source submodule, and the output terminals of each voltage source submodule are connected in series.
6. The combined power flow controller according to claim 5, characterized in that: The voltage source type submodule adopts a topology with bipolar voltage output capability.
7. The combined power flow controller according to claim 1, characterized in that: The passive AC fast switch includes one on / off module and two current limiting modules. The on / off module and the current limiting modules are connected in series, and the on / off module is located between the two current limiting modules.
8. The passive AC fast switch according to claim 7, characterized in that: The current limiting module includes a current limiting resistor and a fast mechanical switch, with the current limiting resistor connected in parallel with the fast mechanical switch.
9. The passive AC fast switch according to claim 8, characterized in that: The switching module includes a conducting branch, a transfer branch, and an energy-consuming branch connected in parallel. The conducting branch is equipped with a fast mechanical switch, the transfer branch is equipped with an inductor and a capacitor connected in series, and the energy-consuming branch is equipped with a surge arrester.
10. The combined power flow controller according to claim 9, characterized in that: During normal operation, the fast mechanical switches in the current limiting module and the switching module of the passive AC fast switch are both in the closed state, and the current limiting resistor of the current limiting module and the transfer branch and energy consumption branch of the switching module are bypassed. When a fault occurs in a high-voltage AC line, the fast mechanical switch in the current limiting module is disconnected, the current limiting resistor is engaged to limit the short-circuit current amplitude, the fast mechanical switch in the switching module is disconnected, and the transfer branch and energy-consuming branch are engaged to quickly block the short-circuit current.