Hybrid transformer module, system and method applied to flexible interconnection scene

Abstract

The invention relates to the technical field of electric power transmission, in particular to a hybrid transformer module, system and method applied to a flexible interconnection scene. According to the scheme, the technical problem that all power cannot flow between two nodes is solved, a new solution is provided for flexible interconnection requirements, and a new scene is provided for application of the hybrid transformer.

Description

Technical Field

[0001] The present invention relates to the field of electric power transmission technology, and in particular to a hybrid transformer module, system and method for use in flexible interconnection scenarios. Background Art

[0002] As the main way to achieve power transmission and power mutual assistance between nodes and busbars in the power grid, flexible interconnection plays an important role in the intelligentization of power grid and power electronics. The current way to realize the flexible interconnection function is mainly through a power electronic transformer composed of back-to-back converters with a capacity consistent with the transmission power between two nodes or with a certain margin. However, the existing converter structure has many problems such as high equipment cost, heat dissipation difficulty, and complex control, and it is impossible to achieve the flow of all power between two nodes. Summary of the invention

[0003] In order to solve the technical problem that it is impossible to realize the flow of all power between two nodes, according to the demand scenario of flexible interconnection scenario, the present invention provides a hybrid transformer module, system and method applied to the flexible interconnection scenario.

[0004] In a first aspect, an embodiment of the present invention provides a hybrid transformer module applied to a flexible interconnection scenario, comprising a double-winding electromagnetic transformer, a first converter, and a second converter;

[0005] The AC side of the first converter is connected to one end of one winding of the double-winding electromagnetic transformer, and the other end of the one winding forms a first node, the AC side of the second converter is connected to one end of the other winding of the double-winding electromagnetic transformer, and the other end of the other winding forms a second node, and the first converter and the second converter are connected via a DC bus;

[0006] If the forward active power needs to flow in the forward flow direction, the first converter is switched to the rectification mode, and the second converter is switched to the inverter mode, so as to perform forward vector compensation on the winding voltage of the double-winding electromagnetic transformer, thereby constructing a forward phase angle difference between the winding voltages, thereby controlling the forward active power to flow in the forward flow direction through forward converter capacity adjustment, wherein the forward flow direction is from the first node to the second node;

[0007] If reverse active power is required to flow in a reverse direction, the first converter is switched to inverter mode and the second converter is switched to rectification mode to perform reverse vector compensation on the winding voltage of the dual-winding electromagnetic transformer, thereby constructing a reverse phase angle difference between the winding voltages, thereby controlling the reverse active power to flow in a reverse direction by adjusting the capacity of the reverse converter, wherein the reverse flow direction is from the second node to the first node.

[0008] Preferably, one side winding and the other side winding of the dual-winding transformer are both connected in a Y-connected manner with a neutral point disconnected.

[0009] Preferably, it includes:

[0010] The rectification mode adopts double closed-loop control of outer loop control of the converter AC side voltage and the converter DC side voltage and inner loop control of the current;

[0011] The inverter mode adopts double closed-loop control of outer loop control of active power output by the converter and voltage on the AC side of the converter and inner loop control of current.

[0012] Preferably, both the forward active power and the reverse active power adopt an active power calculation function, and the active power calculation function is:

[0013]

[0014] Among them, P is the active power that needs to be transmitted; V1 is the first node voltage; V2 is the second node voltage; θ is the phase angle difference between the winding voltages; and X is the total impedance of the hybrid transformer module.

[0015] Preferably, the converter AC side voltage function is:

[0016]

[0017] The V CON is the reference value of the output voltage on the AC side of the converter; wherein the voltage on the AC side of the converter will produce a phase difference of 0°-θ / 2.

[0018] Preferably, the forward converter capacity and the reverse converter capacity both adopt a converter capacity function, and the converter capacity function is:

[0019]

[0020] The P * con is the converter capacity.

[0021] Preferably, the vector relationship function of the voltage is:

[0022] V grid1 =V T1 +V con1

[0023] V grid2 =V T2 +V con2

[0024] Among them, the Vgrid1 is the bus voltage of the power grid connected to the first node, and the Vgrid2 is the bus voltage of the power grid connected to the second node; the VT1 is the inter-winding voltage on one side of the double-winding electromagnetic transformer, and the VT2 is the inter-winding voltage on the other side of the double-winding electromagnetic transformer; VCON1 is the AC side voltage of the first converter, and VCON2 is the AC side voltage of the second converter.

[0025] On the other hand, the present invention also provides a hybrid transformer system applied to a flexible interconnection scenario, including:

[0026] Based on the above hybrid transformer module, the single-phase hybrid transformer system includes:

[0027] The AC side of the first converter is connected to one end of one winding of a double-winding electromagnetic transformer, and the other end of one winding forms a first node, and the first node is connected to a first single-phase power grid bus. The AC side of the second converter is connected to one end of the other winding of the double-winding electromagnetic transformer, and the other end of the other winding forms a second node, and the second node is connected to a second single-phase power grid bus. The first converter and the second converter are connected via a DC bus.

[0028] On the other hand, the present invention also provides a hybrid transformer system applied to a flexible interconnection scenario, including:

[0029] Based on the above hybrid transformer module, the three-phase hybrid transformer system includes:

[0030] The AC side of the first converter is connected to one end of one winding of a double-winding electromagnetic transformer, and the other end of one winding forms a first node, and the first node is connected to a first three-phase power grid bus. The AC side of the second converter is connected to one end of the other winding of the double-winding electromagnetic transformer, and the other end of the other winding forms a second node, and the second node is connected to a second three-phase power grid bus. The first converter and the second converter are connected via a DC bus.

[0031] On the other hand, the present invention also provides a hybrid transformer method applied to a flexible interconnection scenario, including:

[0032] Based on the above hybrid transformer module, the hybrid transformer method includes:

[0033] If the forward active power needs to flow in the forward flow direction, the first converter is switched to the rectification mode, and the second converter is switched to the inverter mode, so as to perform forward vector compensation on the winding voltage of the double-winding electromagnetic transformer, thereby constructing a forward phase angle difference between the winding voltages, thereby controlling the forward active power to flow in the forward flow direction through forward converter capacity adjustment, wherein the forward flow direction is from the first node to the second node;

[0034] If reverse active power is required to flow in a reverse direction, the first converter is switched to inverter mode and the second converter is switched to rectification mode to perform reverse vector compensation on the winding voltage of the dual-winding electromagnetic transformer, thereby constructing a reverse phase angle difference between the winding voltages, thereby controlling the reverse active power to flow in a reverse direction by adjusting the capacity of the reverse converter, wherein the reverse flow direction is from the second node to the first node. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a topological structure diagram of an embodiment of the present invention;

[0036] Figure 2 is a schematic diagram of the forward active power flow of an embodiment of the present invention;

[0037] Figure 3 is a schematic diagram of reverse active power flow according to an embodiment of the present invention;

[0038] Figure 4 is a single-phase topological structure diagram of an embodiment of the present invention;

[0039] Figure 5 is a three-phase topological structure diagram of an embodiment of the present invention;

[0040] Figure 6 is a control block diagram of a converter in a rectifier mode according to an embodiment of the present invention;

[0041] Figure 7 is a control block diagram of a converter in an inverter mode according to an embodiment of the present invention;

[0042] Figure 8 is a voltage vector relationship diagram of an embodiment of the present invention;

[0043] Fig. 9 is a corresponding AC side voltage phase diagram of the first converter and the second converter in an embodiment of the present invention;

[0044] Fig.10 is an AC side active power diagram corresponding to the first converter and the second converter of the embodiment of the present invention;

[0045] Fig.11 is a power diagram between a first node and a second node in an embodiment of the present invention;

[0046] Fig.12 This is a comparison diagram of the power between the first node and the second node and the converter power in an embodiment of the present invention. DETAILED DESCRIPTION

[0047] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0048] Figure 1 FIG. 1 is a topological structure diagram according to an embodiment of the present invention. Figure 1 As shown, the embodiment of the present invention includes a hybrid transformer module applied to a flexible interconnection scenario, including a double-winding electromagnetic transformer TRA100, a first converter CON101 and a second converter CON102;

[0049] The AC side of the first converter CON101 is connected to one end of a winding TRAP1001 on one side of the double-winding electromagnetic transformer, and the other end of the winding on one side forms a first node POS1, the AC side of the second converter CON102 is connected to one end of a winding TRAS1001 on the other side of the double-winding electromagnetic transformer, and the other end of the winding on the other side forms a second node POS2, and the first converter CON101 and the second converter CON102 are connected via a DC bus;

[0050] like Figure 2 As shown, if the forward active power needs to flow in the forward flow direction, the first converter CON101 is switched to the rectification mode, and the second converter CON102 is switched to the inverter mode, so as to perform forward vector compensation on the winding voltage of the double-winding electromagnetic transformer TRA100, and then construct the forward phase angle difference between the winding voltages, so as to control the forward active power to flow in the forward flow direction through the forward converter capacity adjustment, wherein the forward flow direction is from the first node POS1 to the second node POS2;

[0051] like Figure 3 As shown, if reverse active power is required to flow in a reverse flow direction, the first converter CON101 is switched to the inverter mode and the second converter CON102 is switched to the rectifier mode to perform reverse vector compensation on the winding voltage of the dual-winding electromagnetic transformer TRA100, thereby constructing a reverse phase angle difference between the winding voltages, thereby controlling the reverse active power to flow in a reverse flow direction through reverse converter capacity adjustment, wherein the reverse flow direction is from the second node POS2 to the first node POS1.

[0052] According to one embodiment of the present invention, Figure 1 As shown, one side winding and the other side winding of the double-winding transformer are both connected in a Y-connected manner with a neutral point disconnected.

[0053] According to one embodiment of the present invention, Figure 4 , 5 As shown, including:

[0054] The rectification mode adopts double closed-loop control of outer loop control of the converter AC side voltage and the converter DC side voltage and inner loop control of the current;

[0055] The inverter mode adopts double closed-loop control of outer loop control of active power output by the converter and voltage on the AC side of the converter and inner loop control of current.

[0056] According to one embodiment of the present invention, Figure 6-Figure 12 As shown, both the forward active power and the reverse active power use an active power calculation function, and the active power calculation function is:

[0057]

[0058] Among them, P is the active power that needs to be transmitted; V1 is the voltage of the first node POS1; V2 is the voltage of the second node POS2; θ is the phase angle difference between the winding voltages; and X is the total impedance of the hybrid transformer module.

[0059] According to one embodiment of the present invention, Figure 6-Figure 12 As shown, the voltage function of the AC side of the converter is:

[0060]

[0061] The V CON is the reference value of the output voltage on the AC side of the converter; wherein the voltage on the AC side of the converter will produce a phase difference of 0°-θ / 2.

[0062] According to one embodiment of the present invention, Figure 6-Figure 12 As shown, the forward converter capacity and the reverse converter capacity both adopt a converter capacity function, and the converter capacity function is:

[0063]

[0064] The P * con is the converter capacity.

[0065] According to one embodiment of the present invention, Figure 6-Figure 12 As shown, the vector relationship function of the voltage is:

[0066] V grid1 =V T1 +V con1

[0067] V grid2 =V T2 +V con2

[0068] Wherein, the Vgrid1 is the bus voltage of the power grid connected to the first node POS1, and the Vgrid2 is the bus voltage of the power grid connected to the second node POS2; T1is the voltage between the windings TRAP1001 on one side of the double-winding electromagnetic transformer, the V T2 is the voltage between the other winding TRAS1001 of the double-winding electromagnetic transformer; V CON1 is the AC side voltage of the first converter CON101, V CON2 is the AC side voltage of the second converter CON102.

[0069] At the same time, if Figure 5 As shown, the present invention also provides a hybrid transformer system applied to a flexible interconnection scenario, including:

[0070] Based on the above hybrid transformer module, the single-phase hybrid transformer system includes:

[0071] The AC side of the first converter CON101 is connected to one end of a winding TRAP1001 on one side of the dual-winding electromagnetic transformer, and the other end of the winding on one side forms a first node POS1, and the first node POS1 is connected to the first single-phase power grid bus. The AC side of the second converter CON102 is connected to one end of a winding TRAS1001 on the other side of the dual-winding electromagnetic transformer, and the other end of the winding on the other side forms a second node POS2, and the second node POS2 is connected to the second single-phase power grid bus. The first converter CON101 and the second converter CON102 are connected via a DC bus.

[0072] At the same time, if Figure 6 As shown in the figure, the hybrid transformer system applied to the flexible interconnection scenario includes:

[0073] Based on the above hybrid transformer module, the three-phase hybrid transformer system includes:

[0074] The AC side of the first converter CON101 is connected to one end of a winding TRAP1001 on one side of a double-winding electromagnetic transformer, and the other end of the winding on one side forms a first node POS1, and the first node POS1 is connected to a first three-phase power grid bus. The AC side of the second converter CON102 is connected to one end of a winding TRAS1001 on the other side of the double-winding electromagnetic transformer, and the other end of the winding on the other side forms a second node POS2, and the second node POS2 is connected to a second three-phase power grid bus. The first converter CON101 and the second converter CON102 are connected via a DC bus.

[0075] At the same time, if Figure 2 , 3 As shown, the hybrid transformer method applied to the flexible interconnection scenario includes:

[0076] Based on the above hybrid transformer module, the hybrid transformer method includes:

[0077] If the forward active power needs to flow in the forward flow direction, the first converter CON101 is switched to the rectification mode, and the second converter CON102 is switched to the inverter mode, so as to perform forward vector compensation on the winding voltage of the double-winding electromagnetic transformer TRA100, thereby constructing a forward phase angle difference between the winding voltages, thereby controlling the forward active power to flow in the forward flow direction through the forward converter capacity adjustment, wherein the forward flow direction is from the first node POS1 to the second node POS2;

[0078] If reverse active power is required to flow in a reverse flow direction, the first converter CON101 is switched to the inverter mode and the second converter CON102 is switched to the rectifier mode to perform reverse vector compensation on the winding voltage of the dual-winding electromagnetic transformer TRA100, thereby constructing a reverse phase angle difference between the winding voltages, thereby controlling the reverse active power to flow in a reverse flow direction through reverse converter capacity adjustment, wherein the reverse flow direction is from the second node POS2 to the first node POS1.

[0079] Combine the following Figure 1 , 2 , 3. The working principle of the hybrid transformer module shown in the embodiment is explained.

[0080] like Figure 1 As shown, the hybrid transformer module includes a double-winding electromagnetic transformer, a first converter and a second converter; wherein the hybrid transformer module also includes a first node, i.e., the other end of one side winding of the double-winding electromagnetic transformer, one end of one side winding of the double-winding electromagnetic transformer is connected to the AC side of the first converter, and at the same time, the hybrid transformer module also includes a second node, i.e., the other end of the other side winding of the double-winding electromagnetic transformer, one end of the other side winding of the double-winding electromagnetic transformer is connected to the AC side of the second converter, and finally the first converter is connected to the second converter via a DC bus. The hybrid transformer composed of the above structure is used as a Typical partial power conversion power electronic equipment is mainly composed of traditional electromagnetic transformers and power electronic converters. The core idea is that the back-to-back converter is connected in series or in parallel with the winding of the transformer, and the port voltage and power of the hybrid transformer are adjusted by a small part of the power output by the converter. The main functions of the hybrid transformer include power management, reactive power compensation, distributed power supply access, and new energy grid connection. The hybrid transformer applied to the flexible interconnection scenario and the new hybrid transformer topology adapted to the scenario and the corresponding control method proposed in the present invention can drive the full power flowing between the two nodes with the partial power flowing through the power electronic converter, so as to realize the functional requirements of flexible interconnection.

[0081] like Figure 2 , 3As shown, at the same time, based on the above structure, this case includes two power transfer requirements. The first one is that the forward active power flows in the forward flow direction. The forward flow direction refers to from the first node to the second node. Under this transfer requirement, the first converter needs to be switched to the rectification mode and the second converter needs to be switched to the inverter mode. The purpose of this design is to perform forward vector compensation on the winding voltage of the double-winding electromagnetic transformer, and then construct a forward phase angle difference between the winding voltages, and finally realize the control of the forward active power to flow in the forward flow direction through the forward converter capacity adjustment. At the same time, based on the above structure, the second transfer requirement of this case is reverse The active power flows in the reverse flow direction, which refers to the direction from the second node to the first node. Under this transmission requirement, the first converter needs to be switched to the inverter mode and the second converter needs to be switched to the rectifier mode. The purpose of this design is to perform reverse vector compensation on the winding voltage of the dual-winding electromagnetic transformer, thereby constructing a reverse phase angle difference between the winding voltages, thereby controlling the reverse active power to flow in the reverse flow direction through reverse converter capacity adjustment. Based on the above design, the hybrid transformer mainly includes at least one dual-winding electromagnetic transformer and two converters. According to the power flow direction, the first converter works in the rectifier mode. The first converter works in the current flow mode, and the second converter works in the inverter mode, and vice versa; the power electronic converter working in the rectification mode is connected in series with the windings on one side of the dual-winding electromagnetic transformer, and the power electronic converter working in the inverter mode is connected in series with the windings on the other side of the dual-winding electromagnetic transformer; the condition for the flow of active power in the power grid is that there is a phase difference between the two nodes, and the active power will flow from the node with a leading phase to the node with a lagging phase; the basic function of the power electronic converter working in the rectification mode and the power electronic converter working in the inverter mode is to perform vector compensation on the winding voltage of the dual-winding electromagnetic transformer to construct the phase angle difference between the two winding voltages, thereby And realize the flow of active power; for the control strategy of the power electronic converter working in the rectification mode and the power electronic converter working in the inverter mode, there is no essential difference between the rectifier and the inverter, which can also be called the converter working in the rectification mode and the converter working in the inverter mode. The specific working modes of the two converters are related to the power direction that needs to be transmitted between the two nodes. If the power needs to be transmitted from the left end node (Vgrid1) to the right end node (Vgrid2), the left end converter works in the rectification mode and the right end converter works in the inverter mode. If the power flow direction is opposite, the right end converter is inverted and the left end converter is rectified;

[0082] The two windings of the double-winding transformer are both connected in a Y-connected manner with a neutral point disconnected. The AC sides of the two converters are connected in series with the transformer windings, and the two converters are connected via a DC bus.

[0083] like Figure 6 , 8As shown, the above structures all adopt double closed-loop control. The outer loop of the rectifier controls the voltage amplitude on the AC side and the voltage on the DC side, and adopts the current inner loop control. The inverter controls the active power and the voltage amplitude on the AC side output by the power electronic converter working in the rectifier mode and the power electronic converter working in the inverter mode, and adopts the current inner loop control;

[0084] In summary, the beneficial effect of this case is that compared with the traditional full-power power electronic conversion, this case adopts partial power power electronic conversion. The power electronic devices are low in cost, high in equipment reliability, simple to control, the power flowing through the converter is small, the heat generated is small, and the heat is easy to dissipate. It provides a new solution for flexible interconnection needs and a new scenario for the application of hybrid transformers.

[0085] Combine the following Figure 8-Figure 12 The working principle of the hybrid transformer module shown in the embodiment is explained.

[0086] As shown Figure 8-Figure 12 As shown, this case includes four groups of functions, namely the first group: active power calculation function, the second group: converter AC side voltage function, the third group: converter capacity function, and the fourth group: voltage vector relationship function. Based on the above four groups of formulas, we have:

[0087] By KVL:

[0088] V grid1 =V T1 +V con1

[0089] V grid2 =V T2 +V con2

[0090] V grid1 ,V grid2 are the grid voltages on both sides, and their angles are assumed to be 0°. con2 The angle is θ. Since the capacity of the power electronic converter working in the rectification mode and the power electronic converter working in the inverter mode are the same, but the current direction is opposite, V con1 The angle is automatically balanced to -θ. Substituting it into the equation, the angle of voltage difference between the two windings of the double-winding electromagnetic transformer is 2θ, which creates conditions for the flow of active power.

[0091] Assume that the voltages of the two nodes are V1∠0 and V2∠0, the active power to be transmitted is P, and the total impedance of the line and the double-winding electromagnetic transformer is X.

[0092]

[0093] The relationship between θ and other conditions can be obtained. The AC side voltage of the power electronic converter working in the rectification mode and the power electronic converter working in the inverter mode will have a phase difference of θ / 2 with 0°. The vector relationship of the voltage is as follows: Figure 8 As shown:

[0094]

[0095] The output voltage reference values ​​of the power electronic converter working in the rectification mode and the power electronic converter working in the inverter mode can be obtained; after normalization:

[0096]

[0097] The capacity of the power electronic converter working in the rectification mode and the power electronic converter working in the inverter mode can be obtained;

[0098] For example, 50 MV power is transmitted between two nodes in a 200 KV power grid. The AC side voltage output by the power electronic converter working in the rectification mode and the power electronic converter working in the inverter mode is 10∠±98°KV, and the output active power is 2.8 MV; Vgrid1 and Vgrid2 are both 200 KV power grid busbars, and their a, b, and c three-phase outgoing lines are all connected to a three-phase double-winding electromagnetic transformer. The left and right windings of the three-phase double-winding electromagnetic transformer are both Y-connected, and the neutral point is disconnected. The power electronic converter working in the rectification mode on the left side and the left winding of the three-phase double-winding electromagnetic transformer are connected in series, and the AC side voltage is Vcon1. The power electronic converter working in the inverter mode on the right side and the right winding of the three-phase double-winding electromagnetic transformer are connected in series, and the AC side voltage is Vcon2, where:

[0099] V grid1 =V T1 +V con1

[0100] V grid2 =V T2 +V con2

[0101] The capacity of the above two converters is 2.8MVA;

[0102]

[0103] When Vcon2 is 10∠98°KV and Vcon1 is 10∠-98°, the amplitude of the winding voltage VT1 and VT2 of the three-phase double-winding electromagnetic transformer is the same, but the phase of VT1 is ahead of VT2 by about 32°, which creates conditions for the flow of active power. The active power flows from the left to the right, which is determined by:

[0104]

[0105] The active power is 50MW, which means that the 2.8MVA capacity of the circulator leverages the 50MW power flow between the two nodes.

[0106] like Fig. 9 As shown, the AC side voltage phase of the power electronic converter working in the rectifier mode and the power electronic converter working in the inverter mode; when the inverter outputs an AC voltage of a specified phase, the rectifier AC side voltage and the inverter AC side voltage are in opposite phase;

[0107] like Fig.10 As shown, the AC side active power of the power electronic converter working in the rectification mode and the power electronic converter working in the inverter mode;

[0108] like Fig.11 and Fig.12 As shown in the simulation, the power between the two nodes drives a power flow of about 50MW between the two nodes with 2.8MW of power flowing through the power electronic converter working in the rectification mode and the power electronic converter working in the inverter mode.

[0109] Combine the following Figure 4 The working principle of the hybrid transformer system shown in the embodiment is described.

[0110] like Figure 4 As shown, based on the above hybrid transformer module, the first node is connected to the first single-phase grid bus, and the second node is connected to the second single-phase grid bus. Through the above structure, a single-phase hybrid transformer system is formed, thereby providing a topological structure for single-phase power transmission.

[0111] Combine the following Figure 5 The working principle of the hybrid transformer system shown in the embodiment is described.

[0112] like Figure 5 As shown, based on the above hybrid transformer module, the first node is connected to the first three-phase grid bus, and the second node is connected to the second three-phase grid bus. Through the above structure, a three-phase hybrid transformer system is formed, thereby providing a topological structure for three-phase power transmission.

[0113] Combine the following Figure 1 , 2 , 3. The working principle of the hybrid transformer module shown in the embodiment is explained.

[0114] Based on the above hybrid transformer module, this module also provides a hybrid transformer method, which adopts:

[0115] Based on the above structure, this case includes two power transfer requirements. The first one is that the forward active power flows in the forward flow direction. The forward flow direction refers to from the first node to the second node. Under this transfer requirement, the first converter needs to be switched to the rectification mode and the second converter needs to be switched to the inverter mode. The purpose of this design is to perform forward vector compensation on the winding voltage of the double-winding electromagnetic transformer, and then construct a forward phase angle difference between the winding voltages, and finally realize the control of the forward active power to flow in the forward flow direction through the forward converter capacity adjustment. At the same time, based on the above structure, the second transfer requirement of this case is that the reverse active power flows in the reverse flow direction. The reverse flow direction refers to the direction from the second node to the first node. Under this transmission requirement, the first converter needs to be switched to the inverter mode and the second converter needs to be switched to the rectifier mode. The purpose of this design is to perform reverse vector compensation on the winding voltage of the dual-winding electromagnetic transformer, thereby constructing a reverse phase angle difference between the winding voltages, thereby controlling the reverse active power to flow in the reverse direction through reverse converter capacity regulation. Based on the above design, the hybrid transformer mainly includes at least one dual-winding electromagnetic transformer and two converters. According to the power flow direction, the first converter works in the rectifier mode and the second converter works in the inverter mode, and vice versa. Of course; the power electronic converter working in the rectification mode with the windings on one side of the dual-winding electromagnetic transformer in series, and the power electronic converter working in the inverter mode with the windings on the other side of the dual-winding electromagnetic transformer in series; the condition for the flow of active power in the power grid is that there is a phase difference between the two nodes, and the active power will flow from the node with advanced phase to the node with lagging phase; the basic function of the power electronic converter working in the rectification mode and the power electronic converter working in the inverter mode is to perform vector compensation on the winding voltage of the dual-winding electromagnetic transformer to construct the phase angle difference between the two winding voltages, thereby realizing the flow of active power; for the power electronic converter working in the rectification mode The control strategy of the power electronic converter working in the inverter mode, there is no essential difference between the rectifier and the inverter, which can also be called a converter working in the rectification mode and a converter working in the inverter mode. The specific working modes of the two converters are related to the power direction that needs to be transmitted between the two nodes. If power needs to be transmitted from the left end node (Vgrid1) to the right end node (Vgrid2), the left end converter works in the rectification mode and the right end converter works in the inverter mode. If the power flow direction is opposite, the right end converter is inverted and the left end converter is rectified. This case provides a new solution for the flexible interconnection needs and a new scenario for the application of hybrid transformers.

[0116] The various embodiments of the present invention are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments.

[0117] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more features.

[0118] The protection scope of the present invention is not limited to the above-mentioned embodiments. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the scope and spirit of the present invention. If these changes and modifications fall within the scope of the claims of the present invention and their equivalents, the present invention is intended to include these changes and modifications.

Claims

1. A hybrid transformer module applied to flexible interconnection scenarios, characterized in that: It includes a double-winding electromagnetic transformer, a first converter and a second converter; The AC side of the first converter is connected to one end of one winding of the double-winding electromagnetic transformer, and the other end of the one winding forms a first node, the AC side of the second converter is connected to one end of the other winding of the double-winding electromagnetic transformer, and the other end of the other winding forms a second node, and the first converter and the second converter are connected via a DC bus; If the forward active power needs to flow in the forward flow direction, the first converter is switched to the rectification mode, and the second converter is switched to the inverter mode, so as to perform forward vector compensation on the winding voltage of the double-winding electromagnetic transformer, thereby constructing a forward phase angle difference between the winding voltages, thereby controlling the forward active power to flow in the forward flow direction through forward converter capacity adjustment, wherein the forward flow direction is from the first node to the second node; If reverse active power is required to flow in a reverse direction, the first converter is switched to inverter mode and the second converter is switched to rectification mode to perform reverse vector compensation on the winding voltage of the dual-winding electromagnetic transformer, thereby constructing a reverse phase angle difference between the winding voltages, thereby controlling the reverse active power to flow in a reverse direction by adjusting the capacity of the reverse converter, wherein the reverse flow direction is from the second node to the first node.

2. The hybrid transformer module according to claim 1, characterized in that: The one side winding and the other side winding of the double-winding transformer are both connected in a Y-connected manner with a neutral point disconnected.

3. The hybrid transformer module according to claim 1, characterized in that: include: The rectification mode adopts double closed-loop control of outer loop control of the converter AC side voltage and the converter DC side voltage and inner loop control of the current; The inverter mode adopts double closed-loop control of outer loop control of active power output by the converter and voltage on the AC side of the converter and inner loop control of current.

4. The hybrid transformer module according to claim 1, characterized in that: The forward active power and the reverse active power both use an active power calculation function, and the active power calculation function is: Among them, P is the active power that needs to be transmitted; V1 is the first node voltage; V2 is the second node voltage; θ is the phase angle difference between the winding voltages; and X is the total impedance of the hybrid transformer module.

5. The hybrid transformer module according to claim 1, characterized in that: The voltage function of the converter AC side is: The V CON is the reference value of the output voltage on the AC side of the converter; wherein the voltage on the AC side of the converter will produce a phase difference of 0°-θ / 2.

6. The hybrid transformer module according to claim 1, characterized in that: The forward converter capacity and the reverse converter capacity both adopt a converter capacity function, and the converter capacity function is: The P * con is the converter capacity.

7. The hybrid transformer module according to claim 1, characterized in that: The vector relationship function of the voltage V grid1 =V T1 +V con1 V grid2 =V T2 +V con2 Wherein, the Vgrid1 is the bus voltage of the first grid node, and the Vgrid2 is the bus voltage of the second grid node; T1 is the voltage between windings on one side of the double-winding electromagnetic transformer, V T2 is the voltage between the windings on the other side of the double-winding electromagnetic transformer; V CON1 is the AC side voltage of the first converter, V CON2 is the AC side voltage of the second converter.

8. A hybrid transformer system applied to a flexible interconnection scenario, characterized in that: include: Based on the hybrid transformer module according to claim 1 to claim 7, the single-phase hybrid transformer system comprises: The AC side of the first converter is connected to one end of one winding of a double-winding electromagnetic transformer, and the other end of one winding forms a first node, and the first node is connected to a first single-phase power grid bus. The AC side of the second converter is connected to one end of the other winding of the double-winding electromagnetic transformer, and the other end of the other winding forms a second node, and the second node is connected to a second single-phase power grid bus. The first converter and the second converter are connected via a DC bus.

9. A hybrid transformer system applied to a flexible interconnection scenario, characterized in that: include: Based on the hybrid transformer module according to claim 1 to claim 7, the three-phase hybrid transformer system includes: The AC side of the first converter is connected to one end of one winding of a double-winding electromagnetic transformer, and the other end of one winding forms a first node, and the first node is connected to a first three-phase power grid bus. The AC side of the second converter is connected to one end of the other winding of the double-winding electromagnetic transformer, and the other end of the other winding forms a second node, and the second node is connected to a second three-phase power grid bus. The first converter and the second converter are connected via a DC bus.

10. A hybrid transformer method applied to a flexible interconnection scenario, characterized in that: include: Based on the hybrid transformer module according to claim 1 to claim 7, the hybrid transformer method comprises: If the forward active power needs to flow in the forward flow direction, the first converter is switched to the rectification mode, and the second converter is switched to the inverter mode, so as to perform forward vector compensation on the winding voltage of the double-winding electromagnetic transformer, thereby constructing a forward phase angle difference between the winding voltages, thereby controlling the forward active power to flow in the forward flow direction through forward converter capacity adjustment, wherein the forward flow direction is from the first node to the second node; If reverse active power is required to flow in a reverse direction, the first converter is switched to inverter mode and the second converter is switched to rectification mode to perform reverse vector compensation on the winding voltage of the dual-winding electromagnetic transformer, thereby constructing a reverse phase angle difference between the winding voltages, thereby controlling the reverse active power to flow in a reverse direction by adjusting the capacity of the reverse converter, wherein the reverse flow direction is from the second node to the first node.

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