A phase shifting transformer

Abstract

The present application discloses a phase-shifting transformer, including a Sen-type phase shifter and a three-phase isolation transformer connected to each other; the Sen-type phase shifter is used to provide a series compensation voltage for a transmission line, including a three-phase main winding and a three-phase secondary winding; the three-phase main winding includes an A-phase main winding, a B-phase main winding and a C-phase main winding; the three-phase secondary winding includes an A-phase secondary winding, a B-phase secondary winding and a C-phase secondary winding; the three-phase main winding adopts a Y-type connection and is grounded through a neutral point. Through the above-mentioned method, the present application reduces the number of three-phase isolation transformers required; and increases the adjustment range of power flow and phase shift angle; reduces the insulation requirements for the Sen-type phase shifter, making the phase-shifting transformer more suitable for high-voltage power systems.

Description

Technical Field

[0001] The present application relates to the technical field of power transmission lines, and in particular to a phase-shifting transformer. Background Art

[0002] The active power flow transmitted by the AC transmission line is inversely proportional to the line impedance, proportional to the voltage at the head and end of the system, and related to the phase difference of the voltage at the head and end of the system. The uneven distribution of the impedance of the transmission line will cause uneven distribution of the power flow, resulting in overload of some lines, and insufficient utilization of some lines will also reduce the transmission capacity due to insufficient phase difference. Therefore, the existing transmission network urgently needs an effective power flow control device to increase the controllability of the power grid power flow.

[0003] Phase Shifting Transformer (PST) is a power flow control device that can avoid overload and underload of transmission lines or transformer main equipment and improve power supply reliability. By switching the tap of the transformer secondary winding with the on-load tap changer, the output of the series compensation voltage with adjustable phase of 0 to 360° and adjustable amplitude can be realized, thereby realizing the control of the system power flow.

[0004] Compared with traditional phase shifters, Sen-type phase shifters are more flexible in regulating power flow. The 9 secondary windings and on-load tap changers of Sen-type phase shifters are directly connected in series to the transmission system. Figure 1 shown.

[0005] Since the 9 secondary windings and on-load tap changers of the Sen-type phase shifter are directly connected in series to the transmission system, when the system voltage level increases, its insulation cost and difficulty will also increase significantly. Studies have shown that when the voltage level of the power grid is 220kV and above, an additional isolation transformer is required, and the cost advantage of the Sen-type phase shifter will be greatly weakened; in addition, the traditional phase shifter wiring method has a small phase shift angle range and poor power flow regulation ability. Summary of the invention

[0006] The present application provides a phase-shifting transformer to solve the problems of insufficient insulation capacity and poor power flow regulation capability of the Sen-type phase shifter in the prior art when the system voltage level is high.

[0007] To solve the above technical problems, the present application proposes a phase-shifting transformer, comprising a Sen-type phase shifter and a three-phase isolation transformer connected to each other; the Sen-type phase shifter is used to provide a series compensation voltage for a transmission line, comprising a three-phase main winding and a three-phase secondary winding; the three-phase main winding comprises an A-phase main winding, a B-phase main winding and a C-phase main winding; the three-phase secondary winding comprises an A-phase secondary winding, a B-phase secondary winding and a C-phase secondary winding; the three-phase main winding adopts a Y-type connection and is grounded through a neutral point.

[0008] Optionally, the Sen-type phase shifter also includes a first on-load voltage-regulating switch and a second on-load voltage-regulating switch; the first on-load voltage-regulating switch is arranged on the three-phase main winding; and the second on-load voltage-regulating switch is arranged on the three-phase secondary winding.

[0009] Optionally, the A-phase main winding is respectively connected to the A-phase transmission line, the B-phase secondary winding and the neutral point; the B-phase main winding is respectively connected to the B-phase transmission line, the C-phase secondary winding and the neutral point; the C-phase main winding is respectively connected to the C-phase transmission line, the A-phase secondary winding and the neutral point; the A-phase secondary winding is connected to the B-phase transmission line through a three-phase isolation transformer; the B-phase secondary winding is connected to the C-phase transmission line through a three-phase isolation transformer; and the C-phase secondary winding is connected to the A-phase transmission line through a three-phase isolation transformer.

[0010] Optionally, the voltage expression of the first end of the transmission line after compensation is:

[0011]

[0012] Among them, U sA1 is the voltage at the first end of the A-phase transmission line after compensation; U sB1 is the voltage at the head end of the B-phase transmission line after compensation; U sC1 is the voltage at the head end of the C-phase transmission line after compensation; U sA , U sB and U sC are the voltage at the first end of the transmission line before compensation; U HVSTA , U HVSTB and U HVSTC are the compensation voltages generated by the Sen-type phase shifter; U b1 is the compensation voltage generated by the B phase main winding; U c2 is the compensation voltage generated by the C phase secondary winding; U c1 is the compensation voltage generated by the C phase main winding; U a2 is the compensation voltage generated by the secondary winding of phase A; U a1 is the compensation voltage generated by the A-phase main winding; U b2 It is the compensation voltage generated by the B phase secondary winding.

[0013] Optionally, the first on-load voltage regulator and the second on-load voltage regulator are switched within the range of 0, ±1, ±2, ..., ±m. By controlling the switching position of the on-load voltage regulator, the series compensation voltage provided by each winding can be adjusted within three ranges: positive, zero, and negative.

[0014] Optionally, when the first on-load voltage regulating switch and the second on-load voltage regulating switch are switched to different positions, the Sen-type phase shifter outputs series compensation voltages of different amplitudes and phases, thereby adjusting the amplitude and phase of the compensated head-end voltage.

[0015] Optionally, the voltage vector output by the Sen-type phase shifter is positively correlated with the adjustment levels m of the first on-load voltage regulating switch and the second on-load voltage regulating switch. Optionally, the adjustment positions of the first on-load voltage regulating switches of the A-phase main winding, the B-phase main winding and the C-phase main winding are the same, and the adjustment positions of the second on-load voltage regulating switches of the A-phase secondary winding, the B-phase secondary winding and the C-phase secondary winding are the same.

[0016] Optionally, the power flow formula at the end of the transmission line is:

[0017] P r =10sinδ+10U HVST sin(δ+θ HVST );

[0018] Q r =10(cosδ-1)+10U HVsT cos(δ+θ HVST );

[0019] Among them, P r is the active power; Q r is the reactive power; δ is the phase difference between the beginning and the end of the transmission line; U HVST ,θ HVST is the amplitude and phase of the compensation voltage vector of the Sen-type phase shifter.

[0020] Optionally, the rated current of the three-phase isolation transformer is related to the rated current of the transmission line, the rated voltage of the three-phase isolation transformer is related to the rated voltage of the transmission line and the no-load phase shift angle of the Sen-type phase shifter; the rated capacity of the three-phase isolation transformer is related to its rated current and rated voltage.

[0021] The present application proposes a phase-shifting transformer, which utilizes a Sen-type phase shifter to provide a portion of the series compensation voltage, thereby reducing the demand for the number of three-phase isolation transformers; by changing the wiring method of the windings, the demand for the number of three-phase isolation transformers is further reduced, and the adjustment range of the power flow and the phase shift angle is increased; so that at the same phase shift angle, the capacity of the phase-shifting transformer is smaller and the cost is lower; by adding a three-phase isolation transformer, the insulation requirements for the Sen-type phase shifter are reduced, making the phase-shifting transformer more suitable for high-voltage power systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the implementation manner will be briefly introduced below. Obviously, the drawings described below are only some implementation manners of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1It is a schematic diagram of the structure of a traditional Sen-type phase shifter;

[0024] Figure 2 It is a structural schematic diagram of an embodiment of a phase-shifting transformer of the present application;

[0025] Figure 3(a) is the compensation voltage U of the A-phase transmission line of this application HVSTA A schematic structural diagram of an embodiment of a corresponding structure;

[0026] FIG3( b ) is a vector diagram of an embodiment of the compensation voltage output by the Sen-type phase shifter of the present application;

[0027] FIG. 4( a ) is a vector diagram of another embodiment of the compensation voltage output by the Sen-type phase shifter of the present application;

[0028] FIG4( b ) is a vector diagram of the voltage after compensation of the A-phase transmission line of the present application;

[0029] FIG5(a) is a compensation voltage vector diagram output by the Sen-type phase shifter of the present application when m=1;

[0030] FIG5( b ) is a compensation voltage vector diagram output by the Sen-type phase shifter of the present application when m=2;

[0031] FIG5(c) is a compensation voltage vector diagram output by the Sen-type phase shifter of the present application when m=3;

[0032] Figure 6 A schematic diagram of the structure of an embodiment of a power transmission system connected to a phase-shifting transformer in the present application;

[0033] Figure 7 It is a schematic diagram of an embodiment of parameter relationship of a Sen-type phase shifter of the present application;

[0034] Figure 8 It is a schematic diagram of the secondary side phase voltage of the Sen type phase shifter;

[0035] Fig. 9 1 is a schematic structural diagram of an embodiment of a Sen-type phase shifter in the present application taking phase A as an example;

[0036] Fig.10 A schematic diagram of an embodiment of the parameter relationship of a three-phase isolation transformer of the present application;

[0037] Fig.11 It is a schematic diagram of an embodiment of the phase-shifting transformer parameter relationship of the present application. DETAILED DESCRIPTION

[0038] In order to enable those skilled in the art to better understand the technical solution of the present application, a phase-shifting transformer provided by the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0039] The present application proposes a phase-shifting transformer that is more suitable for application at voltage levels of 220 kV and above. The phase-shifting transformer includes a three-phase isolation transformer and a high-voltage Sen-type phase shifter (High-Voltage "Sen" Transformer, HVST) connected to each other.

[0040] Sen type phase shifter, used to provide series compensation voltage for transmission line, includes three-phase main winding and three-phase secondary winding; three-phase main winding includes A phase main winding a1, B phase main winding b1 and C phase main winding c1; three-phase secondary winding includes A phase secondary winding a2, B phase secondary winding b2 and C phase secondary winding c2. The structure of three-phase main winding is similar to autotransformer. Three-phase main winding adopts Y-type connection and is grounded through neutral point.

[0041] See also Figure 2 The Sen-type phase shifter also includes two groups of on-load voltage regulating switches, namely a first on-load voltage regulating switch and a second on-load voltage regulating switch. The first on-load voltage regulating switch is arranged on the three-phase main winding; the second on-load voltage regulating switch is arranged on the three-phase secondary winding.

[0042] In the Sen type phase shifter, the A phase main winding a1 is respectively connected to the A phase transmission line, the B phase secondary winding b2 and the neutral point; the B phase main winding b1 is respectively connected to the B phase transmission line, the C phase secondary winding c2 and the neutral point; the C phase main winding c1 is respectively connected to the C phase transmission line, the A phase secondary winding a2 and the neutral point.

[0043] The A-phase secondary winding a2 is connected to the B-phase transmission line through a three-phase isolation transformer; the B-phase secondary winding b2 is connected to the C-phase transmission line through a three-phase isolation transformer; and the C-phase secondary winding c2 is connected to the A-phase transmission line through a three-phase isolation transformer.

[0044] The voltage U at the first end of the transmission line before compensation sA , U sB , U sC Provide parallel input voltage for the three-phase main winding; the series compensation voltage U generated by the Sen-type phase shifter HVSTA , U HVSTB , U HVSTC It is injected into the transmission line through a three-phase isolation transformer. The voltage at the head end of the transmission line after compensation is U sA1 , U sB1 , U sC1 .

[0045] Furthermore, the B-phase main winding b1 and the C-phase secondary winding c2 are connected in series through an on-load tap changer to provide a series compensation voltage U of the A-phase transmission line. HVSTA The C-phase main winding c1 and the A-phase secondary winding a2 are connected in series through the on-load tap changer to provide the series compensation voltage U of the B-phase transmission line. HVSTBThe A-phase main winding a1 and the B-phase secondary winding b2 are connected in series through the on-load tap changer to provide the series compensation voltage U of the C-phase transmission line. HVSTC .

[0046] The series compensation voltages provided by the A-phase main winding a1, the B-phase main winding b1, the C-phase main winding c1, the A-phase secondary winding a2, the B-phase secondary winding b2 and the C-phase secondary winding c2 are respectively denoted as U a1 , U b1 , U c1 , U a2 , U b2 , U c2 , the voltage expression of the first end of the transmission line after compensation is:

[0047]

[0048] By adjusting the position of the on-load tap changer, the series compensation voltage provided by the A-phase main winding a1, the B-phase main winding b1, the C-phase main winding c1, the A-phase secondary winding a2, the B-phase secondary winding b2 and the C-phase secondary winding c2 can be adjusted.

[0049] Among them, the first on-load voltage regulator of the A-phase main winding a1, the B-phase main winding b1 and the C-phase main winding c1 needs to be adjusted to the same position, and the second on-load voltage regulator of the A-phase secondary winding a2, the B-phase secondary winding b2 and the C-phase secondary winding c2 also needs to be adjusted to the same position. Only in this way can the compensated system head-end voltage U sA1 , U sB1 , U sC1 Only in this way can the three-phase voltage be kept balanced.

[0050] It should be noted that the positions of the on-load voltage regulators between the three-phase main winding "a1-b1-c1" and the three-phase secondary winding "a2-b2-c2" can be different, that is, the positions of the first on-load voltage regulator and the second on-load voltage regulator can be different, so that voltages of different amplitudes can be provided to the three-phase main winding and the three-phase secondary winding, and series compensation voltages of different amplitudes and phases can be superimposed.

[0051] In order to see the wiring method of the phase-shifting transformer more clearly, please refer to Figure 3(a) and set the compensation voltage U HVSTA The B-phase main winding b1 and the C-phase secondary winding c2 provide the series compensation voltage U of the A-phase transmission line. HVSTA , series compensation voltage U HVSTAIt is injected into the transmission line through a three-phase isolation transformer. The two on-load voltage regulators are switched in the range of (0, ±1, ±2, ..., ±m). By controlling the switching position of the two on-load voltage regulators, the series compensation voltage provided by the B-phase main winding b1 and the C-phase secondary winding c2 can be adjusted in the positive, zero, and negative ranges. Therefore, the compensation voltage amplitude and phase obtained after superposition are adjustable. Figure 3(b) shows the compensation voltage vector diagram output by the Sen-type phase shifter when the adjustment level m=1.

[0052] Since the compensation voltage output by the Sen-type phase shifter is three-phase symmetrical, the following will use the compensation voltage U of the A-phase transmission line as an example. HVSTA Taking the output of the Sen-type phase shifter as an example, the distribution characteristics of the compensation voltage vector under different adjustable levels are analyzed, and the power flow regulation area of ​​the Sen-type phase shifter under different voltage phase differences at the beginning and end of the transmission line is calculated.

[0053] The tap switching position of the main winding b1 of phase B is denoted as k b , the tap switching position of the C phase secondary winding c2 is recorded as k c When the tap switching position is at ±m, the amplitude of the output voltage of the B-phase main winding b1 and the C-phase secondary winding c2 is the maximum output voltage of a single secondary winding of the Sen-type phase shifter, also known as the rated voltage of the secondary winding of the Sen-type phase shifter, expressed as U sN express.

[0054] The phase of the output voltage of the Sen-type phase shifter relative to the voltage at the head end of the transmission line is denoted by θ HVST . Still analyzing the case where the adjustment level m = 1, that is, k b and k c It can take values ​​between (0, ±1). The vector diagram of the compensation voltage output by the Sen-type phase shifter and the voltage vector diagram of the A-phase transmission line after compensation are shown in Figure 4(a) and Figure 4(b), and the corresponding voltage vector table is shown in Table 1.

[0055] Table 1 Sen-type phase shifter output voltage vector and corresponding line head voltage after compensation (m=1)

[0056]

[0057] It can be seen from Figure 4(a) and Figure 4(b) and Table 1 that when the two groups of on-load tap-changing switches of the Sen-type phase shifter are switched to different positions, the Sen-type phase shifter can output compensation voltages of different amplitudes and phases, thereby adjusting the amplitude and phase of the compensated line head-end voltage.

[0058] Furthermore, when the number of adjustment stages m increases, the voltage vectors that can be output by the Sen-type phase shifter will also increase. Figure 5(a) to Figure 5(c)Shown is a compensation voltage vector diagram output by the Sen-type phase shifter when m=1, m=2 and m=3.

[0059] The tap switching position of the B phase main winding b1 and the C phase secondary winding c2 can be set in (0, ±1, ±2, ..., ±m). When the tap position is switched at ±m, the amplitude of the output voltage of the B phase main winding b1 or the C phase secondary winding c2 is U sN , as shown in Figure 5. b1step and U c2step They represent the voltage vector between adjacent taps of the B-phase main winding b1 and the C-phase secondary winding c2, and the amplitude of the voltage vector is represented by U step If it is expressed, then:

[0060] U step =|U b1step |=|U c2step |=U sN / m……(2)

[0061] When m=1, the Sen-type phase shifter can output 9 voltage vectors (including the zero vector), and its output voltage vector diagram and the corresponding compensated system voltage are shown in FIG4 and Table 1.

[0062] When m=2, the Sen-type phase shifter can output 25 voltage vectors (including the zero vector), and its output voltage vector diagram is shown in Figure 5(b). b =-2, k c = 1, the output voltage vector of the Sen-type phase shifter is the vector U in Figure 5(b). HVST1 As shown, the voltage at the head end of the line after compensation is the vector U in the figure. 1 shown.

[0063] When m=3, the Sen-type phase shifter can output 49 voltage vectors (including the zero vector), and its output voltage vector diagram is shown in Figure 5(c). b =1, k c = -3, the output voltage vector of the Sen-type phase shifter is the vector U in Figure 5(c). HVST2 As shown, the voltage at the head end of the line after compensation is the vector U in the figure. 2 shown.

[0064] By analogy, when the on-load voltage regulator is adjustable in ±m levels, the number of voltage vectors M that the Sen-type phase shifter can output is:

[0065] M=(2m+1) 2 ……(3)

[0066] The compensation voltage output by the Sen-type phase shifter can be calculated as:

[0067] U HVSTA =k b U b1step +k c U c2step ……(4)

[0068] The voltage vector output by the Sen-type phase shifter is positively correlated with the adjustment levels m of the first on-load voltage regulator and the second on-load voltage regulator: when the adjustment levels increase, the number M of compensation voltage vectors that the Sen-type phase shifter can output will increase, and the voltage adjustment accuracy will also increase accordingly. Therefore, the adjustment level of the Sen-type phase shifter can be designed according to actual adjustment needs.

[0069] Figure 6 : is a schematic diagram of the structure of an embodiment of a power transmission system connected to a phase-shifting transformer of the present application, wherein the compensation function of the phase-shifting transformer is represented by a voltage vector U HVST Indicates that the magnitude of the voltage vector is U HVST , the phase is θ HVST .

[0070] The two ends of the transmission line are simplified to an ideal single-machine infinite system. Before compensation, the voltage at the head end of the system is represented by Us, with an amplitude of Us and a phase of 0°. The voltage at the end of the system is represented by Ur, with an amplitude of Ur and a phase of -δ, that is, the phase difference between the head and the end of the system is δ. After passing through the phase-shifting transformer, the voltage vector at the head end of the system is represented by U s1 Indicates that its amplitude is U s1 , at this time the phase difference between the beginning and the end of the system is δ 1 Ignoring the resistance and capacitance of the transmission line, the equivalent reactance of the transmission line is X L express.

[0071] The power transmitted by the transmission line to the end is S r , where active power and reactive power are represented by P r , Qr represents, Figure 6 The terminal power calculation formula of the system can be obtained as follows:

[0072]

[0073] When there is no phase-shifting transformer compensation, that is, the output voltage of the phase-shifting transformer is U HVST = 0, the power transmitted by the transmission line to the end is S r0 , where active power and reactive power are represented by P r0 , Q r0 The terminal power calculation formula of the system is:

[0074]

[0075] The expressions of the system head and terminal voltage and the compensation voltage of the phase-shifting transformer are:

[0076]

[0077] Substituting equation (7) into equation (5) and equation (6) respectively, we can obtain the active and reactive power at the end of the transmission system after installing the phase-shifting transformer:

[0078]

[0079]

[0080] When there is no phase-shifting transformer compensation device, the active and reactive power at the end of the system is:

[0081]

[0082]

[0083] From equations (8) to (11), it can be obtained that the adjustment amount of the phase-shifting transformer on the active and reactive power at the end of the system is:

[0084]

[0085]

[0086] When the system is determined, the amplitude of the voltage at the beginning and end of the system, the phase difference, and the reactance of the transmission line will not change, that is, Us, Ur, δ and X in the formula L Keep constant. The phase of the output voltage of the phase-shifting transformer is θ HVST Adjustable from 0 to 360°, output voltage amplitude U HVST exist Adjustable. By adjusting the tap switching position of the phase-shifting transformer, the amplitude and phase of the output voltage of the phase-shifting transformer can be adjusted, thereby flexibly adjusting the active and reactive power flows at the end of the system.

[0087] System voltage U s =U r =1p.u., assuming that the equivalent reactance of the transmission line is X L =0.1pu.

[0088] Substituting into equation (8) and equation (9), the system terminal power flow formula can be obtained as follows:

[0089] P r =10sinδ+10U HVST sin(δ+θ HVST )……(14)

[0090] Q r=10(cosδ-1)+10U HVST cos(δ+θ HVST )……(15)

[0091] Since the on-load tap changer is adjusted step by step, the power flow adjustment point of the phase-shifting transformer is also discrete. When the adjustment level m of the phase-shifting transformer is increased, the power flow adjustment accuracy of the phase-shifting transformer will increase accordingly. sN When the phase-shifting transformer is used, the power flow regulation range of the phase-shifting transformer will be expanded. This is the principle of power flow regulation by the phase-shifting transformer.

[0092] The phase-shifting transformer can output discrete voltage vectors within a 360° range. Depending on the number of adjustment levels, the voltage value output by the phase-shifting transformer is also different. The more adjustment levels there are, the more voltage vectors the phase-shifting transformer can control, and the more accurate the voltage control is. In practical applications, the adjustment level of the phase-shifting transformer can be designed according to the system adjustment needs and the allowable error range.

[0093] according to Figure 7 Determine the parameters of the Sen-type phase shifter:

[0094] According to the calculation of high-voltage line power flow demand, assuming that the no-load phase shift angle of the Sen-type phase shifter is θ, Figure 8 The voltage regulation characteristic (M = 3) can be obtained as follows: the secondary side voltage U′ of the Sen-type phase shifter N2 :

[0095]

[0096]

[0097] Taking into account the influence of line resistance and phase shifter leakage impedance in actual power flow regulation, a certain margin is left for the expansion of the regulation range of the ring network by the phase shifter for future line reconstruction and capacity expansion. The rated value of the secondary side voltage (phase voltage) of the Sen-type phase shifter is:

[0098] U N2 = kU′ N2 ……(18)

[0099] In the formula, k is the margin coefficient, which can usually be taken as 1.05~1.2.

[0100] Taking phase A as an example, the structure of the Sen-type phase shifter and the main electrical parameters required for design are as follows: Fig. 9 shown.

[0101] Sen type phase shifter primary rated voltage (phase voltage) rated value U N1 Pick:

[0102]

[0103] Assume the rated current of the line is I N , so the secondary rated current of the Sen-type phase shifter is N2 :

[0104] I N2 =I N ……(20)

[0105] Therefore, the capacity S of the low-voltage side (secondary side) of the Sen-type phase shifter is S2 :

[0106]

[0107] Therefore, the capacity of the Sen-type phase shifter is S N :

[0108] S N =S N2 ……(twenty two)

[0109] Sen type phase shifter high voltage side winding (non-common winding) rated current I N1 :

[0110]

[0111] Rated current I of the common line group of Sen type phase shifter N1-2 :

[0112] I N1-2 =I N1 +I N2 ……(twenty four)

[0113] according to Fig.10 Determine the parameters of the three-phase isolation transformer:

[0114] The rated current of the three-phase isolation transformer is the line rated current I 隔离 Right now:

[0115] I 隔离 =I N ……(25)

[0116] The rated phase voltage of the three-phase isolation transformer is the maximum compensation voltage U of the phase-shifting transformer. 隔离 :

[0117]

[0118] Due to the existence of the isolation transformer leakage reactance, the phase shift angle and voltage amplitude under no-load condition are larger than those under load. Therefore, in terms of equipment selection, the voltage amplitude under no-load condition should be 2U 隔离 To determine the capacity S of the three-phase isolation transformer 隔离 .

[0119]

[0120] The maximum number of voltage regulation levels n max You can choose according to actual needs.

[0121] according to Fig.11 Determine the winding core cross-sectional area, number of coil turns and wire diameter of the Sen-type phase shifter:

[0122] The structure of the windings in the Sen-type phase shifter can be the same, wherein the number of turns of the winding coil is related to its input and output voltages, output power, and cross-sectional area of ​​the silicon steel sheet.

[0123] In the winding with a frequency of 50HZ, there are:

[0124]

[0125]

[0126]

[0127] Among them, S is the cross-sectional area of ​​the winding core; P is the active power of the winding; N is the number of turns of the winding; B is the magnetic permeability of the silicon steel sheet. The magnetic permeability of small and medium-sized sets is selected between 6000 and 12000H / m. The magnetic permeability of today's silicon steel sheets is generally around 10000H / m, so 10000H / m is taken; D is the wire diameter, I is the winding current, and δ is the current density, which is generally 2 to 3A / m2, and 2.5A / m2 is taken here.

[0128] Usually, during design, the maximum efficiency of the winding is often designed to be in the range of 50% to 60% of the rated load of the winding to improve the use efficiency of the winding. Therefore, the general power load is about 50% to 60% of the winding capacity.

[0129] The capacity of the winding is calculated in volt-amperes, while the load is calculated in watts. There is a power factor difference between the two. Considering that the actual line is not a pure resistive load, a power factor of 0.8 is usually considered.

[0130] From this, the cross-sectional area of ​​the winding core, the number of coil turns and the wire diameter are:

[0131] The core cross-sectional area, primary and secondary coil turns and wire diameter of the Sen-type phase shifter are:

[0132]

[0133]

[0134]

[0135]

[0136]

[0137]

[0138] Similarly, the core cross-sectional area, primary and secondary coil turns, and wire diameter of the three-phase isolation transformer are:

[0139]

[0140]

[0141]

[0142]

[0143] In summary, the present application proposes a phase-shifting transformer, which utilizes a Sen-type phase shifter to provide a portion of the series compensation voltage, thereby reducing the demand for the number of three-phase isolation transformers; by changing the wiring method of the windings of the Sen-type phase shifter, the demand for the number of three-phase isolation transformers and on-load tap-changing switches is further reduced, and the adjustment range of the power flow and phase shift angle is increased; so that under the same phase shift angle, the capacity of the phase-shifting transformer is smaller and the cost is lower; by adding a three-phase isolation transformer, the insulation requirements for the windings of the Sen-type phase shifter and the on-load tap-changing switches are reduced, making the phase-shifting transformer more suitable for high-voltage power systems.

[0144] It is to be understood that the specific embodiments described herein are only used to explain the present application, rather than to limit the present application. In addition, for ease of description, only some structures related to the present application are shown in the accompanying drawings, rather than all structures. The step numbers used in the text are also only for the convenience of description and are not used as a limitation on the order in which the steps are executed. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0145] The terms "first", "second", etc. in this application are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

[0146] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0147] The above are only implementation methods of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A phase-shifting transformer, characterized in that: It includes a Sen-type phase shifter and a three-phase isolation transformer connected to each other; The Sen-type phase shifter is used to provide a series compensation voltage for a power transmission line, and includes a three-phase main winding and a three-phase secondary winding; the three-phase main winding includes an A-phase main winding, a B-phase main winding and a C-phase main winding; the three-phase secondary winding includes an A-phase secondary winding, a B-phase secondary winding and a C-phase secondary winding; the three-phase main winding adopts a Y-type connection and is grounded through a neutral point; The A-phase main winding is respectively connected to the A-phase transmission line, the B-phase secondary winding and the neutral point; the B-phase main winding is respectively connected to the B-phase transmission line, the C-phase secondary winding and the neutral point; the C-phase main winding is respectively connected to the C-phase transmission line, the A-phase secondary winding and the neutral point; The A-phase secondary winding is connected to the B-phase transmission line through the three-phase isolation transformer; the B-phase secondary winding is connected to the C-phase transmission line through the three-phase isolation transformer; the C-phase secondary winding is connected to the A-phase transmission line through the three-phase isolation transformer; The Sen-type phase shifter further includes a first on-load voltage-regulating switch and a second on-load voltage-regulating switch; the first on-load voltage-regulating switch is arranged on the three-phase main winding; the second on-load voltage-regulating switch is arranged on the three-phase secondary winding; wherein: When the first on-load tap-changing switch and the second on-load tap-changing switch are switched to different positions, the Sen-type phase shifter outputs series compensation voltages of different amplitudes and phases, so that the amplitude and phase of the compensated head-end voltage can be adjusted; wherein the expression of the compensated head-end voltage of the transmission line is: ； in, is the voltage at the first end of the A-phase transmission line after compensation; is the voltage at the first end of the B-phase transmission line after compensation; is the voltage at the head end of the C-phase transmission line after compensation; , and are respectively the head-end voltages of the transmission line before compensation; , and are the compensation voltages generated by the Sen-type phase shifter is the compensation voltage generated by the B-phase main winding; is the compensation voltage generated by the C-phase secondary winding; is the compensation voltage generated by the C-phase main winding; is the compensation voltage generated by the A-phase secondary winding; is the compensation voltage generated by the A phase main winding is the compensation voltage generated by the B-phase secondary winding.

2. The phase-shifting transformer according to claim 1, characterized in that: The first on-load voltage regulating switch and the second on-load voltage regulating switch are switched in the range of 0, ±1, ±2, ..., ±m. By controlling the switching position of the on-load voltage regulating switch, the series compensation voltage provided by each winding can be adjusted in three ranges: positive, zero, and negative.

3. The phase-shifting transformer according to claim 1, characterized in that: The voltage vector output by the Sen-type phase shifter is positively correlated with the regulation levels m of the first on-load voltage regulating switch and the second on-load voltage regulating switch.

4. The phase-shifting transformer according to claim 3, characterized in that: The adjustment positions of the first on-load voltage-regulating switches of the A-phase main winding, the B-phase main winding and the C-phase main winding are the same, and the adjustment positions of the second on-load voltage-regulating switches of the A-phase secondary winding, the B-phase secondary winding and the C-phase secondary winding are the same.

5. The phase-shifting transformer according to claim 4, characterized in that: The power flow formula at the end of the transmission line is: ； ； in, is the active power; is the reactive power; is the phase difference between the beginning and the end of the transmission line; , is the amplitude and phase of the compensation voltage vector of the Sen-type phase shifter.

6. The phase-shifting transformer according to claim 5, characterized in that: The rated current of the three-phase isolation transformer is related to the rated current of the transmission line, and the rated voltage of the three-phase isolation transformer is related to the rated voltage of the transmission line and the no-load phase shift angle of the Sen-type phase shifter; the rated capacity of the three-phase isolation transformer is related to its rated current and rated voltage.

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