Improved method for constructing steady-state voltage source model of electromagnetic hybrid power flow controller

Abstract

The invention provides a method for constructing a steady-state voltage source model of an improved electromagnetic hybrid power flow controller, and the method comprises the steps: forming the steady-state voltage source model of the improved electromagnetic hybrid power flow controller based on the topology of the improved electromagnetic hybrid power flow controller; the series connection part of the Sen transformer is composed of an equivalent voltage source and an internal impedance, the parallel connection part of the Sen transformer is a controlled current source, and discrete adjustment of injection voltage is completed by adjusting the position of a tap; a serial connection part of the rotary power flow controller is composed of a controlled ideal voltage source and a controlled internal impedance, a parallel connection branch is a controlled current source, and continuous adjustment of voltage injected into a line is completed by changing the magnitude of alpha 1 and alpha 2. The series connection part of the improved electromagnetic hybrid power flow controller is the sum of series connection line voltage vectors of the Sen transformer and the rotary power flow controller, and any continuous regulation voltage vector in a large range is formed. Finally, the method can achieve the effective control of the power flow of the high-voltage-grade power transmission line.

Description

Technical Field

[0001] The invention belongs to the field of power transmission and distribution network flow control, and in particular relates to a method for constructing a steady-state voltage source model of an improved electromagnetic hybrid power flow controller. Background Art

[0002] The "Sen" transformer is a three-phase four-winding transformer based on transformer tap control technology, including one primary winding and three secondary windings. The primary winding is star-connected and connected to the line bus in parallel. The three secondary windings of each phase are connected in series to the three-phase circuit through a voltage regulating switch, which can realize discrete regulation of the injected line voltage. However, existing research has mostly focused on circuit topology and control methods, and there is little steady-state modeling of the "Sen" transformer.

[0003] The main body of the "Sen" transformer is a three-phase four-winding transformer structure, so it shows high reliability and low cost, but its adjustment accuracy depends on the number of tap switches, and the response time is limited by the tap switches. Therefore, it shows the disadvantages of poor control accuracy and slow response speed during the power flow control process.

[0004] The rotating power flow controller is a flexible AC power transmission device based on a rotating phase-shifting transformer. It has the advantages of simple control method, harmonic-free output and high reliability. Existing research shows that it can flexibly control the line compensation voltage without being affected by the line current, thus providing a new method for economical, flexible and frequent control of power systems.

[0005] Taking into account the advantages of the "Sen" transformer and the rotating power flow controller, a hybrid power flow controller topology based on a large-capacity "Sen" transformer and a small-capacity rotating power flow controller is proposed. Its electromagnetic structure has the advantages of low cost, no harmonics and high reliability. By injecting a voltage vector with a size and direction that is continuously adjustable 360° into the line, continuous decoupling control of the line power is achieved. Summary of the invention

[0006] The purpose of the present invention is to provide an improved electromagnetic hybrid power flow controller topology structure and a method for constructing a steady-state voltage source model in view of the deficiencies of the above-mentioned prior art. The topology structure allows the rotating power flow controller and the "Sen" transformer to share the primary side excitation winding. At this time, the electromagnetic hybrid power flow controller is a three-phase five-winding structure, which saves the cost of the isolation transformer on the parallel side of the rotating power flow controller, and at the same time, it makes the rotating power flow controller and the "Sen" transformer have an electromagnetic connection. The secondary sides of the two devices are connected in series to the transmission line to complete the power control of the transmission line; at the same time, under the background of determining the capacity of the "Sen" transformer and the rotating power flow controller, a steady-state voltage source model based on the electromagnetic hybrid power flow controller is proposed.

[0007] The technical solution of the present invention is an electromagnetic hybrid power flow controller topology structure based on a large-capacity "Sen" transformer and a small-capacity rotating power flow controller. The "Sen" transformer includes a closed iron core magnetic circuit, a primary excitation winding, a secondary series winding, and an on-load voltage-changing tap changer; the primary excitation winding of the "Sen" transformer is star-connected and connected in parallel to the system's delivery busbar, and each phase on the secondary side is composed of three tapped windings and a matching power electronic switch assembly TP.

[0008] The topological structure of the rotary power flow controller is composed of two sets of rotary phase-shifting transformers, which are characterized by including a main circuit and controller, a servo motor, a measuring transformer, an electric control switch, a turbine, a worm, a housing, accessories, etc., in which the primary winding of the rotary phase-shifting transformer is connected in parallel to the line to transfer electric energy and the secondary winding voltage is connected in series to the line;

[0009] Topology of electromagnetic hybrid power flow controller In order to make up for the high cost of rotary power flow controller and the deficiency of discrete regulation of “Sen” transformer, a topology of electromagnetic hybrid power flow controller is proposed and a steady-state voltage source model is constructed.

[0010] The topological structure of the electromagnetic hybrid power flow controller is based on the "Sen" transformer, with an additional primary winding on the secondary side, forming a three-phase five-winding main structure, in which the primary winding is a parallel winding; the first three windings on the secondary side are the "Sen" transformer windings; the fourth winding on the secondary side is the secondary winding of the rotating power flow controller; finally, the secondary winding of the "Sen" transformer and the secondary winding of the rotating power flow controller are directly connected to the line in series or connected to the transmission line through a series transformer at a high voltage level, thereby realizing effective power control of the transmission line. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is the topological structure diagram of the electromagnetic hybrid power flow controller.

[0012] Figure 2 Schematic diagram of the rotary power flow controller

[0013] Figure 3 Detailed wiring diagram of the rotating power flow controller in the electromagnetic hybrid power flow controller topology

[0014] Figure 4 The equivalent circuit of the primary parallel side of the "Sen" transformer

[0015] Figure 5 The equivalent circuit of the secondary series side of the "Sen" transformer

[0016] Figure 6 The equivalent circuit diagram of the rotary power flow controller is

[0017] Figure 7Simplified circuit diagram for electromagnetic hybrid power flow controller DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] See also Figure 1 The electromagnetic hybrid power flow controller topology diagram in the figure can be used to obtain the equivalent circuit of the primary parallel side of the "Sen" transformer as follows: Figure 4 As shown, according to Kirchhoff's voltage law, the relationship between the electrical quantities on the primary side is:

[0020]

[0021] Where U sA , U sB , U sC is the system sending end voltage; I Ash , I Bsh , I Csh , is the parallel side current of the system; Z Ash , Z Bsh , Z Csh is the leakage impedance and excitation impedance of the primary winding,

[0022] Under the premise of ensuring the three-phase symmetry of the compensation voltage, the position relationship of each secondary winding tap satisfies:

[0023]

[0024] See also Figure 5 , we can get the equivalent circuit diagram of the secondary series measurement of the "Sen" transformer, and its detailed relationship can be expressed as:

[0025]

[0026] Where U STA , U STB , U STC I is the voltage component of the “Sen” transformer connected in series to the line; As1 , I Bs1 , I Cs1 k is the line current after connecting to the electromagnetic hybrid power flow controller; a , k b , k c They are the tap positions of each phase in the primary, secondary and tertiary windings of the secondary side of the "Sen" transformer; Z S"Sen" is the internal impedance of the secondary winding of the transformer converted to the secondary side, where U Ash , U Bsh , U Csh , and I As1 , I Bs1 , I Cs1 The derivation process is as follows.

[0027] Assuming an ideal ST, the active and reactive power emitted or absorbed by the parallel side of the ST is equal to the active and reactive power absorbed or emitted by the series side, so:

[0028]

[0029] From KCL, we can know that:

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037] in

[0038]

[0039] At this time, on the parallel excitation energy-taking side, there are:

[0040]

[0041] In the line series measurement:

[0042]

[0043] At this time there are:

[0044]

[0045]

[0046] At this point, the simplified circuit model of the "Sen" transformer can be obtained as follows Figure 5 As shown, the series part consists of an equivalent voltage source and internal impedance, and the parallel part is a controlled current source. The discrete adjustment of the injected voltage is completed by adjusting the tap position.

[0047] U ST =T ST U s +Z ST I s

[0048] The equivalent circuit of electromagnetic hybrid power flow controller is as follows: Figure 7 As shown, k d is the transformation ratio of the secondary winding of the "Sen" transformer; k is the voltage transformation ratio of the two sets of rotating phase-shifting transformers; I smh I is the current on the parallel side of the quaternary winding of the "Sen" transformer; m is the primary current of the rotary power flow controller; Z mh is the leakage impedance and excitation impedance of the primary quaternary winding of the "Sen" transformer; Z m The impedance of the secondary quaternary winding of the "Sen" transformer and the rotary power flow controller calculated to the primary side; Z RPST is calculated to the secondary impedance of the rotating phase-shifting transformer; α1 and α2 are the stator and rotor voltage phase shift angles of the two rotating phase-shifting transformers respectively.

[0049] Ignoring the transformer excitation current, the following relationship can be obtained according to the traditional transformer analysis method:

[0050] U rotor =k d (U s -I smh Z smh )-I m Z m

[0051] U RPFC =U stator1 +U stator1 +2I s1 Z RPST

[0052] I s =I s1 +I smh

[0053] Reference Figure 5 , then the stator and rotor voltages of the two rotating phase-shifting transformers satisfy the following relationship:

[0054]

[0055] Let δ = (α1-α1) / 2, You can get:

[0056]

[0057] Based on the electromagnetic induction theorem, assuming an ideal rotating phase-shifting transformer, the active and reactive power emitted or absorbed by the parallel side of the rotating phase-shifting transformer is equal to the active and reactive power absorbed or emitted by the series side, so

[0058] U Rotor I m * =U Stator I s1 *

[0059] The primary current I of the "Sen" transformer can be calculated smh , the primary current I of the rotary power flow controller m , system line current I s1 They are:

[0060]

[0061] Then the injected voltage generated by the rotating power flow controller can be calculated as:

[0062] U RPFC =T RPFC U s +Z RPFC I s

[0063]

[0064] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A method for constructing a steady-state voltage source model of an improved electromagnetic hybrid power flow controller, characterized in that: include: Based on the improved electromagnetic hybrid power flow controller topology, the constructed model includes the "Sen" transformer steady-state voltage source model and the rotating power flow controller steady-state voltage source model, forming an improved electromagnetic hybrid power flow controller steady-state voltage source model; The "Sen" transformer comprises a closed iron core magnetic circuit, a primary excitation winding, a secondary series winding, and an on-load voltage tap changer; the primary excitation winding of the "Sen" transformer is star-connected and connected in parallel to the system's delivery busbar, and each phase of the secondary side consists of three tapped windings and a matching power electronic switch assembly TP; The topological structure principle diagram of the "Sen" transformer is used to establish an equivalent circuit of the primary parallel side and an equivalent circuit of the secondary series side, and then derive the mathematical relationship between various electrical quantities based on the equivalent circuit diagram; The simplified circuit model of the "Sen" transformer can be obtained through the topological structure principle diagram of the "Sen" transformer, so as to achieve discrete adjustment of the injected voltage by adjusting the tap position; The topological structure of the rotating power flow controller is composed of two sets of rotating phase-shifting transformers, and is characterized in that it includes a main circuit and controller in which the primary winding of the rotating phase-shifting transformer is connected in parallel to the line to transfer electric energy and the secondary winding voltage is connected in series to the line, a turbine, a measuring transformer, an electric control switch, a turbine, a worm, a housing, accessories, etc.; The rotating power flow controller obtains energy from the rotor side of the rotating phase-shifting voltage regulator in parallel; then the relative angular displacement of the primary and secondary (stator and rotor) winding axes is changed by using the induction voltage regulation principle, and while completing the power transfer between the primary and secondary through magnetic field induction, the secondary winding voltage phase is adjusted (relative to the primary voltage phase), and then the secondary winding is directly connected in series to the line or the end of the line; The equivalent circuit diagram is established based on the topological structure principle diagram of the rotary power flow controller, and then the mathematical relationship between various electrical quantities on the rotary power flow controller side is derived according to the equivalent circuit diagram; The simplified circuit model of the rotating power flow controller can realize continuous regulation of the injected voltage by adjusting the positions of the stator and rotor voltage phase shift angle taps α1 and α2 of the two rotating power flow controllers; The topological structure of the electromagnetic hybrid power flow controller adds a winding on the secondary side on the basis of the "Sen" transformer, forming a three-phase five-winding main structure, in which the primary side winding is a parallel winding; the first three windings on the secondary side are the "Sen" transformer windings; the fourth winding on the secondary side is the secondary winding of the rotating power flow controller; finally, the secondary winding of the "Sen" transformer and the secondary winding of the rotating power flow controller are directly connected to the line in series or connected to the transmission line through a series transformer at a high voltage level, thereby realizing effective power control of the transmission line.

2. The steady-state voltage source model of the electromagnetic hybrid power flow controller according to claim 1 is characterized in that: First, the equivalent circuit diagram of the "Sen" transformer and the rotary power flow controller is mathematically analyzed; The equivalent circuit of the primary parallel side of the "Sen" transformer has the following relationship: Where U sA , U sB , U sC is the system sending end voltage; I Ash , I Bsh , I Csh is the parallel side current of the system; Z Ash , Z Bsh , Z Csh is the leakage impedance and excitation impedance of the primary winding; The equivalent circuit of the secondary series side of the "Sen" transformer has the following relationship: Where U STA , U STB , U STC is the voltage component of ST connected in series to the circuit; I As1 ,I Bs1 ,I Cs1 k is the line current after connecting to the electromagnetic hybrid power flow controller; a , k b , k c They are the tap positions of each phase in the primary, secondary and tertiary windings of the secondary side of the "Sen" transformer; Z s "Sen" is the internal impedance of the secondary winding of the transformer converted to the secondary side; The injection voltage generated by the rotating power flow controller satisfies the following relationship: U RPFC =T RPFC U s +Z RPFC I s In the formula

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