Phase shift and transformation integrated transformer and control method

Abstract

The invention discloses a phase-shifting and voltage-transformation integrated transformer and a control method. The phase-shifting and voltage-transformation integrated transformer is provided with two cores and five windings, an iron core 1 is provided with a winding 1, a winding 2 and a winding 3, the winding 1 is a high-voltage winding, adopts YN wiring and is provided with a tap, the winding 2 is a low-voltage voltage-regulating winding, is provided with an on-load tap-changer and adopts yn wiring, and the winding 3 is a low-voltage voltage-transformation winding and adopts d wiring; wherein the iron core 2 is provided with a winding 4 and a winding 5, the winding 4 is a low-voltage winding and adopts D wiring, the head end and the tail end of a phase A of the winding 4 are connected to a phase b and a phase c voltage regulating winding of the winding 2, the winding 5 is a high-voltage winding corresponding to the winding 4 and is directly connected to a high-voltage line, and a middle outgoing line of the winding 5 is connected with the head end of the winding 1. According to the transformer, phase shifting of an access line of the winding 5 is achieved by adjusting an on-load tap-changer of the winding 2, and effective adjustment of independent transformation of the winding 3 is achieved by adjusting a tap of the winding 1.

Description

Technical Field

[0001] The invention relates to a phase-shifting and voltage-transforming integrated transformer and a control method, belonging to the technical field of transformers. Background Art

[0002] With the large-scale grid connection of new energy sources, the safety and stability of the power system are beginning to face new challenges. The three characteristics of wind power and photovoltaic power (randomness, intermittency, and volatility) conflict with the need for reliable power supply support for the stable operation of the power grid, which will lead to problems such as frequent changes in line power flow and low transmission efficiency. Therefore, it is necessary to use power flow control methods to adjust the transmission power of the line. The phase-shifting transformer superimposes a suitable voltage phasor on the voltage on the input side of the line, so that the voltage phase difference on both sides of the line changes, thereby achieving the purpose of regulating the line power flow. Compared with other adjustment methods, the phase-shifting transformer has the advantages of low cost and high reliability, and can effectively improve the utilization efficiency of existing power grid lines.

[0003] Traditional phase-shifting transformers only regulate the voltage phase and do not provide stable and adjustable low voltage to power the distribution network load. When there are low-voltage loads around the phase-shifting transformer that need stable power supply, a separate transformer is often required, which will undoubtedly greatly increase the cost. Summary of the invention

[0004] In order to solve the problem of single function of the phase-shifting transformer in the prior art, the present invention provides a phase-shifting and voltage-transforming integrated transformer capable of outputting a stable voltage transformation and a control method.

[0005] In order to achieve the above-mentioned purpose, the technical solution proposed in the present invention is: a phase-shifting transformer integrated transformer, the phase-shifting transformer integrated transformer is a double-core five-winding structure, including iron core 1, iron core 2, winding 1, winding 2, winding 3, winding 4 and winding 5, the iron core 1 cooperates with winding 1, winding 2 and winding 3; the end of winding 1 has a tap; winding 2 is a voltage regulating winding corresponding to winding 1, winding 2 has taps, each tap is connected to an on-load tap changer, and the on-load tap changer has a forward and reverse conversion selector; winding 3 is a transformer winding corresponding to winding 1, and the first and last ends of phase a of winding 3 are connected to the output ends of phase a and phase c. The head and end of winding 3 phase b are connected to the output end of phase b and phase a, and the head and end of winding 3 phase c are connected to the output end of phase c and phase b; the iron core 2 cooperates with winding 4 and winding 5; the head and end of winding 4 phase A are connected to the output end of the positive and negative conversion selector of winding 2 phase b and phase c on-load tap changer, the head and end of winding 4 phase B are connected to the output end of the positive and negative conversion selector of winding 2 phase c and phase a on-load tap changer, the head and end of winding 4 phase C are connected to the output end of the positive and negative conversion selector of winding 2 phase a and phase b on-load tap changer, winding 5 is the high-voltage winding corresponding to winding 4, winding 5 is connected to the high-voltage line, and the middle lead wire is connected to the head end of winding 1.

[0006] The winding 1 is a high voltage winding, adopts YN connection, and each phase winding 1 has a tap of ±m×Δu%, where m is a positive integer and Δu is 1.25.

[0007] The winding 2 is a low voltage regulating winding, which adopts YN connection. The transformation ratio k1 between the winding 1 and the winding 2 is adjusted by changing the position of the on-load tap changer.

[0008] The winding 3 adopts D connection, and the output voltage of the winding 3 is adjusted by changing the tap position of the winding 1.

[0009] The winding 4 is a low voltage winding and adopts D connection.

[0010] A control method for a phase-shifting integrated transformer is specifically as follows: the phase-shifting integrated transformer realizes the phase shift of a winding 5 connected to a line by adjusting the position of a tap of a winding 2 and the position of a forward and reverse conversion selector of an on-load tap changer; and the output voltage of a winding 3 is adjusted by adjusting the tap of a winding 1.

[0011] The magnitude of the phase shift angle α of the phase shift of the winding 5 connected to the line can be calculated by the following formula:

[0012]

[0013] Among them, k1 is the transformation ratio between winding 1 and winding 2, and k2 is the transformation ratio between winding 4 and winding 5.

[0014] When adjusting the winding transformer output through the winding tap, in order to ensure that the phase shift angle α remains unchanged, it is necessary to simultaneously adjust the position of the on-load tap changer of winding 2 to ensure that the value of k1 remains unchanged.

[0015] The beneficial effects of the present invention are:

[0016] The present invention proposes a double-core five-winding phase-shifting transformer and a control method thereof, which can output voltage through winding 3, and adjust the output voltage of winding 3 by adjusting the tap of winding 1, thereby expanding and improving the single function of the current phase-shifting transformer that is only used for phase shifting to achieve power flow control, so that the phase-shifting transformer has both the phase shifting function and the function of providing effective transformer output stable with load, which is of positive significance for ensuring the safe and stable operation of the new energy high-penetration power system and improving the utilization rate of new energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the winding connection diagram of the phase-shifting and voltage-transforming integrated transformer, with lagging phase shifting.

[0018] Figure 2 This is the lagging phase-shifting voltage vector diagram of the phase-shifting and voltage-transforming integrated transformer.

[0019] Figure 3This is the winding connection diagram of the phase-shifting and voltage-transforming integrated transformer, with advanced phase shifting.

[0020] Figure 4 This is the leading phase-shift voltage vector diagram of the phase-shifting and voltage-transforming integrated transformer.

[0021] Figure 5 This is a schematic diagram of voltage regulation of a phase-shifting and voltage-transforming integrated transformer.

[0022] Figure 6 This is a schematic diagram of the application scenario of the phase-shifting and voltage-transforming integrated transformer. DETAILED DESCRIPTION

[0023] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] Example

[0025] like Figure 1 As shown, the three phases of the phase-shifting and voltage-transforming integrated transformer of this embodiment are all provided with a set of double-core five-winding structures, in which the iron core 1 is provided with winding 1, winding 2 and winding 3, and the iron core 2 is provided with winding 4 and winding 5.

[0026] For the five groups of windings, winding 1 is a high-voltage winding, which adopts YN connection, and each phase winding has a tap m±Δu%, where m is a positive integer and Δu is generally 1.25; winding 1 has a tap and the tap is located at the end of the winding, and the three-phase voltage value can be adjusted simultaneously by adjusting the tap position; winding 2 is a low-voltage voltage regulating winding corresponding to winding 1, which adopts yn connection and is equipped with an on-load tap changer. Each tap of the winding is connected to the on-load tap changer. The on-load tap changer has a forward and reverse conversion selector, and the transformation ratio k1 between winding 1 and winding 2 can be adjusted by changing the position of the tap changer; winding 3 is a low-voltage transformer winding corresponding to winding 1, which adopts d connection, and the head and end of winding 3 phase a are connected to the output end of phase a and phase c, the head and end of winding 3 phase b are connected to the output end of phase b and phase a, and the head and end of winding 3 phase c are connected to the output end of phase b and phase a. It is connected to the output end of phase c and phase b. The output voltage of winding 3 can be effectively adjusted by changing the tap position of winding 1 to meet the needs of different loads. Winding 4 is a low-voltage winding and adopts D connection. The head and end of phase A of winding 4 are connected to the output end of the positive and negative conversion selector of the on-load tap changer of winding 2 phase b and phase c, the head and end of phase B of winding 4 are connected to the output end of the positive and negative conversion selector of the on-load tap changer of winding 2 phase c and phase a, and the head and end of phase C of winding 4 are connected to the output end of the positive and negative conversion selector of the on-load tap changer of winding 2 phase a and phase b. The positive and negative change of the phase shift angle can be achieved by simultaneously changing the output of the positive and negative conversion selector of the on-load tap changer of winding 2. Winding 5 is directly connected to the high-voltage winding corresponding to winding 4 of the high-voltage line, and its middle lead wire is connected to the head end of winding 1. The transformation ratio k2 between winding 4 and winding 5 cannot be adjusted.

[0027] The control method of the phase-shifting and voltage-transforming integrated transformer in this embodiment is as follows: Figure 1 When the option switch of the on-load tap changer of winding 2 is at the plus sign, a lagging phase shift angle α and a stable transformer output are formed, and its voltage vector diagram is as follows: Figure 2 As shown;

[0028] Figure 1 In the figure, the two ends of the high-voltage coils of each phase of winding 5 are respectively connected to the head end UsA1, UsB1, UsC1 of the three-phase transmission line and the end UsA2, UsB2, UsC2 of the line, and the tap in the middle of the winding is connected to the head end of winding 1, and the voltage at the tap is UAL, UBL, UCL. The phase difference α between the voltage at the head end of the three-phase transmission line and the corresponding phase voltage at the end of the line is the phase shift angle. The vector difference between the head end of the transmission line and the tap in the middle of the winding is: ΔUA, ΔUB, ΔUC. That is: The same is true for B and C; the three-phase output voltage of winding 3 is Ua, Ub, and Uc. Figure 1-5 The vector names correspond to the same physical quantity.

[0029] Voltage combination Figure 3 When the option switch of the on-load tap changer of winding 2 is at the minus position, an advanced phase shift angle α and a stable transformer output are formed. The voltage vector diagram is as follows: Figure 4 As shown. Combined Figure 1 Figure 2 Figure 3 Figure 4 It can be seen that by changing the tap position of winding 2 and the position of the option switch, the magnitude and positive and negative of the phase shift angle can be effectively adjusted, where the magnitude is determined by the formula Calculated; however, in the process of adjusting the phase shift, the output voltage of winding 3 does not change. When the output voltage of winding 3 needs to be adjusted to adapt to its load change, it is achieved by adjusting the tap of winding 1, as shown in the following example: Figure 5 As shown, when the tap position decreases, it is equivalent to increasing the number of turns of winding 1, thereby increasing k1, and the output voltage of winding 3 increases. Similarly, when the tap position increases, it is equivalent to reducing the number of turns of winding 1, thereby reducing k1, and the output voltage of winding 3 decreases. At this moment, in order to ensure that the phase shift angle α remains unchanged, it is necessary to adjust the position of the on-load tap changer of winding 2 at the same time to ensure that the size of k1 remains unchanged.

[0030] The phase shift control method and transformer output voltage adjustment method of the above-mentioned phase-shifting transformer can realize automatic control of the tap position of winding 1 and the position and direction of the tap switch of winding 2 by sensing the output of each winding of the transformer and using computational programming, thereby realizing closed-loop precise automatic control.

[0031] Application Examples

[0032] This example illustrates the application of the integrated transformer and control method of the invention in combination with a specific application scenario. Figure 6 As shown in the figure, a large number of renewable energy sources are connected to the two 220kV substations. Due to the intermittent and random nature of renewable energy power generation, the load on the 220kV main transformer is unbalanced, affecting the safe and stable operation of the system and the effective absorption of renewable energy. The closed-loop operation can be achieved through the 110kV busbar, and the main transformer load can be balanced by connecting a mobile transformer and through reasonable control. At the same time, it provides a stable transformer energy supply function for energy-consuming enterprises to improve the level of local absorption of renewable energy. For this scenario, the voltage level of the integrated transformer can be designed as 110 / 110 / 10kV, that is, the voltage level is the 110kV phase shift part of winding 1 through low voltage winding 2 winding 4 to winding 5, and the phase shift angle can be selected as ±10°, with a step difference of 1°, according to the penetration of new energy and the comprehensive fluctuation of load; the voltage level is the 110kV transformer power supply part of winding 1 to the 10kV transformer power supply part of winding 3, and the transformer part forms a YNd11 wiring method, and the tap of winding 1 adopts ±8×1.25%, which meets the specification requirements of the State Grid 110kV general transformer. Figure 6 In the application scenario shown, the integrated transformer can be used to shift phases to achieve power flow adjustment for 110kV closed-loop operation, balance the loads of two 220kV main transformers, and provide a stable 10kV power supply voltage for energy-consuming enterprises through voltage transformation.

[0033] The technical solutions of the present invention are not limited to the above-mentioned embodiments, and any technical solutions obtained by equivalent replacement methods fall within the scope of protection required by the present invention.

Claims

1. A phase-shifting and voltage-transforming integrated transformer, characterized in that: The phase-shifting transformer is a double-core five-winding structure, including iron core 1, iron core 2, winding 1, winding 2, winding 3, winding 4 and winding 5. The iron core 1 cooperates with winding 1, winding 2 and winding 3; the end of winding 1 has a tap; winding 2 is the voltage regulating winding corresponding to winding 1, and winding 2 With tap , each tap is connected to an on-load tap changer, and the on-load tap changer has a forward and reverse conversion selector; winding 3 is a transformer winding corresponding to winding 1, the head and end of winding 3 phase a are connected to the output end of phase a phase c, the head and end of winding 3 phase b are connected to the output end of phase b phase a, and the head and end of winding 3 phase c are connected to the output end of phase c phase b; the iron core 2 cooperates with winding 4 and winding 5; the head and end of winding 4 phase A are connected to the output end of the on-load tap changer of winding 2 phase b phase c, the head and end of winding 4 phase B are connected to the output end of the on-load tap changer of winding 2 phase c phase a, the head and end of winding 4 phase C are connected to the output end of the on-load tap changer of winding 2 phase a phase b, and the winding 5 is a high-voltage winding corresponding to winding 4. Winding 5 is connected to the high-voltage line, and the middle lead wire is connected to the head end of winding 1.

2. The phase-shifting and voltage-transforming integrated transformer according to claim 1, characterized in that: The winding 1 is a high voltage winding, adopts YN connection, and each phase winding 1 has a tap of ±m×Δu%, where m is a positive integer and Δu is 1.

25.

3. The phase-shifting and voltage-transforming integrated transformer according to claim 2, characterized in that: The winding 2 is a low voltage regulating winding, which adopts YN connection. The transformation ratio k1 between the winding 1 and the winding 2 is adjusted by changing the position of the on-load tap changer.

4. The phase-shifting and voltage-transforming integrated transformer according to claim 3, characterized in that: The winding 3 adopts D connection, and the output voltage of the winding 3 is adjusted by changing the tap position of the winding 1.

5. The phase-shifting and voltage-transforming integrated transformer according to claim 4, characterized in that: The winding 4 is a low voltage winding and adopts D connection.

6. A control method for the phase-shifting and voltage-transforming integrated transformer according to any one of claims 1 to 5, characterized in that: The phase-shifting transformer achieves phase shift of the winding 5 access line by adjusting the position of the tap of the winding 2 and the position of the forward and reverse conversion selector of the on-load tap changer; and adjusts the output voltage of the winding 3 by adjusting the tap of the winding 1.

7. The control method of the phase-shifting and voltage-transforming integrated transformer according to claim 6, characterized in that: The magnitude of the phase shift angle α of the phase shift of the winding 5 connected to the line can be calculated by the following formula: Among them, k1 is the transformation ratio between winding 1 and winding 2, and k2 is the transformation ratio between winding 4 and winding 5.

8. The control method of a phase-shifting and voltage-transforming integrated transformer according to claim 7, characterized in that: When adjusting the winding transformer output through the winding tap, in order to ensure that the phase shift angle α remains unchanged, it is necessary to simultaneously adjust the position of the on-load tap changer of winding 2 to ensure that the value of k1 remains unchanged.

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