A voltage transformer based on active two-stage inductive voltage divider

Abstract

The present invention discloses a voltage transformer based on an active two-stage inductive voltage divider, comprising a voltage transformer, the primary side of the voltage transformer is connected to a bus, the secondary side of the voltage transformer is connected to a high-accuracy active two-stage inductive voltage divider, the voltage transformer and the high-accuracy active two-stage inductive voltage divider are cascaded to form a high-precision variable ratio voltage transformer, the primary side of the variable ratio voltage transformer is connected to the bus, and the secondary side is connected to a synchronous device. In the device of the present invention, when the bus voltage changes, the rated voltage on the synchronous device system side always remains high-precision constant, and quasi-synchronous grid connection can be accurately and conveniently achieved without frequent manual setting of the rated voltage parameters of the synchronous device.

Description

Technical Field

[0001] The invention belongs to the field of voltage transformer devices, and in particular relates to a voltage transformer based on an active two-stage inductive voltage divider. Background Art

[0002] At present, in the actual production of power plants, the synchronization device plays a vital role in the process of grid-connected power generation. During the synchronous grid-connected process, the synchronization device realizes quasi-synchronous parallel connection by detecting and controlling the amplitude, frequency and phase angle difference of the voltage on the system side and the side to be connected. In actual production, the voltage on the side to be connected sampled by the synchronization device is taken out by the voltage transformer connected to the generator outlet. Since the generator voltage remains unchanged, the rated voltage of the secondary side of the voltage transformer is 100V, that is, the rated voltage of the side to be connected of the synchronization device is 100V; the voltage on the system side sampled by the synchronization device is taken out by the voltage transformer on the bus. However, the voltage of the bus will vary within a certain range in actual operation, and the rated voltage of the primary side of the voltage transformer connected to the bus will also vary, which will cause the rated voltage of the secondary side of the voltage transformer installed on the bus to vary within a certain range, that is, the rated voltage on the system side of the synchronization device cannot always be stably taken as 100V, and will vary with the change of the bus voltage. Therefore, this leads to the frequent setting of the rated voltage on the system side on the synchronization device. When the bus voltage changes, the rated voltage on the system side of the synchronous device must be reset according to the bus voltage. The parameter settings are all adjusted manually, which undoubtedly increases the workload of the operating personnel and increases the probability of errors, which may cause the unit to be unable to connect to the grid normally, affecting the efficiency of the power plant. At the same time, although the existing technology can be applied to voltage transformers with adjustable ratios, there is a problem of low adjustment accuracy under power frequency. The input impedance of the voltage divider will decrease accordingly with the self-inductance impedance of the coil, resulting in a larger error in the voltage divider. When used together with a synchronous device, it will lead to a series of problems such as asynchronous grid connection due to excessive errors, which will also affect the efficiency of the power plant. Summary of the invention

[0003] The object of the present invention is to provide a voltage transformer based on an active two-stage inductive voltage divider, which has the characteristic that the rated voltage value of the synchronous device system side is constant when the bus voltage varies within a certain range.

[0004] The technical solution adopted by the present invention is a voltage transformer based on an active two-stage inductive voltage divider, comprising a voltage transformer, wherein the primary side of the voltage transformer is connected to a bus, and the secondary side of the voltage transformer is connected to a high-accuracy active two-stage inductive voltage divider. The voltage transformer and the high-accuracy active two-stage inductive voltage divider are cascaded to form a high-precision variable ratio voltage transformer, wherein the primary side of the variable ratio voltage transformer is connected to the bus, and the secondary side is connected to a synchronization device.

[0005] The high-precision active two-stage inductive voltage divider has an excitation winding and an auxiliary winding wound in sequence at one end of the same excitation core, and an additional iron core is superimposed on the other end and then a voltage winding is wound.

[0006] The dimensions of the high-accuracy active two-stage inductive voltage divider excitation core are 55mm×75mm×12mm.

[0007] The dimensions of the high accuracy active two-stage inductive voltage divider with additional core are 46mm×84mm×7mm.

[0008] The coefficient of the high-accuracy active two-stage inductive voltage divider is adjustable from 0.95 to 1.06.

[0009] The bus voltage variation range is 330kV (1±2﹡2.5%).

[0010] The present invention has the following beneficial effects:

[0011] The variable ratio adjustable voltage transformer for the synchronization device of the present invention is formed by cascading the voltage transformer and the high-accuracy active two-stage inductive voltage divider to form a variable ratio adjustable voltage transformer; the variable ratio adjustable voltage transformer for the synchronization device can achieve that when the bus voltage changes, the rated voltage on the system side of the synchronization device always remains constant with high precision, and quasi-synchronous grid connection can be accurately and conveniently achieved without frequent manual setting of the rated voltage parameters of the synchronization device. In addition, the high-accuracy active two-stage inductive voltage divider itself has the characteristic of high accuracy, and by compensating the voltage on the leakage impedance of the excitation winding, the input impedance of the voltage divider is increased by hundreds of times at the power frequency to achieve the effect of improving the accuracy of the voltage divider. Therefore, the present invention will show high-precision performance in voltage conversion accuracy compared with ordinary voltage transformers. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of the structure of the voltage transformer with adjustable ratio for the synchronization device of the present invention;

[0013] In the figure, 1. busbar, 2. voltage transformer, 3. high-accuracy active two-stage inductive voltage divider, 4. ratio-adjustable voltage transformer, 5. synchronization device. DETAILED DESCRIPTION

[0014] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the examples given are not intended to limit the present invention.

[0015] A voltage transformer based on an active two-stage inductive voltage divider comprises a voltage transformer 2, wherein the primary side of the voltage transformer 2 is connected to a bus 1, the secondary side of the voltage transformer 2 is connected to a high-accuracy active two-stage inductive voltage divider 3, the voltage transformer 2 and the high-accuracy active two-stage inductive voltage divider 3 are cascaded to form a high-precision variable ratio voltage transformer 4, the primary side of the variable ratio voltage transformer 4 is connected to the bus, and the secondary side is connected to a synchronization device 5.

[0016] The high-precision active two-stage inductive voltage divider 3 has an excitation winding and an auxiliary winding wound in sequence at one end of the same excitation core, and a voltage winding wound after an additional iron core is superimposed at the other end.

[0017] The dimensions of the high-accuracy active two-stage inductive voltage divider 3 excitation core are 55mm×75mm×12mm.

[0018] The dimensions of the additional core of the high-accuracy active two-stage inductive voltage divider 3 are 46 mm×84 mm×7 mm.

[0019] The coefficient of the high-accuracy active two-stage inductive voltage divider 3 is adjustable in the range of 0.95 to 1.06.

[0020] The voltage variation range of bus 1 is 330kV (1±2﹡2.5%).

[0021] The variable ratio voltage transformer for the synchronization device of the present invention has a main body of a voltage transformer 2; it also includes a high-accuracy active two-stage inductive voltage divider 3; the voltage transformer 2 and the high-accuracy active two-stage inductive voltage divider 3 are electrically connected in sequence. The voltage transformer 2 and the high-accuracy active two-stage inductive voltage divider 3 are cascaded to form a high-accuracy variable ratio voltage transformer 4. The primary side of the voltage transformer 2 is connected to the bus; the secondary side of the voltage transformer 2 and the high-accuracy active two-stage inductive voltage divider 3 are cascaded to form a high-accuracy variable ratio voltage transformer 4; the secondary side of the variable ratio voltage transformer 4 is connected to the synchronization device 5; the voltage on the secondary side of the variable ratio voltage transformer 4 is used as the voltage sampled by the system side of the synchronization device 5.

[0022] like Figure 1 As shown, the variable ratio voltage transformer 4 of the present invention is composed of a voltage transformer 2 connected to a bus 1 and a high-precision active two-stage inductive voltage divider 3 connected to the secondary side of the voltage transformer 2. The variable ratio voltage transformer 4 has its primary side connected to the bus 1 and its secondary side connected to a synchronization device 5.

[0023] Among them, the high-accuracy active two-stage inductive voltage divider 3 is different from the general two-stage inductive voltage divider in that the error of the voltage divider is large when it is in a low-frequency working state. The invention adopts a high-accuracy active two-stage inductive voltage divider. Compared with the two-stage voltage divider, its innovation lies in the design of auxiliary winding and active electronic compensation circuit, which significantly improves the accuracy of the inductive voltage divider.

[0024] Specifically, when the high-accuracy active two-stage inductive voltage divider 3 used in the present invention works in a low-frequency state, the coil self-inductance impedance is reduced, so that the input impedance of the voltage divider is correspondingly reduced, resulting in a larger error of the voltage divider. The high-accuracy active two-stage inductive voltage divider uses auxiliary windings and active electronic circuits to compensate for the voltage on the leakage impedance of the exciting winding without increasing the iron core of the voltage divider, so that the input impedance of the voltage divider can be increased by hundreds of times at the power frequency, thereby improving the input impedance of the voltage divider and solving the problem of increased voltage ratio error due to reduced coil inductance at low frequencies. Thereby improving the accuracy of the inductive voltage divider.

[0025] The size of the excitation core is 55mm×75mm×12mm (inner diameter×outer diameter×height). After the excitation winding and the auxiliary winding are wound in sequence, an additional core with a size of 46mm×84mm×7mm is superimposed, and then the voltage winding is wound. Compared with the power frequency two-stage inductive voltage divider, the volume of the high-accuracy active two-stage inductive voltage divider is significantly reduced; and according to the requirements of the present invention, its voltage ratio is adjustable within the range of 0.95~1.06.

[0026] The rated voltage of the bus 1 is 330 kV. According to the gear of the main transformer, the voltage variation range of the bus 1 is 330 kV (1±2﹡2.5%).

[0027] If the bus voltage is 330 kV, the coefficient of the high-accuracy active two-stage inductive voltage divider 3 is 1;

[0028] If the bus voltage is 321.75 kV, the coefficient of the high-accuracy active two-stage inductive voltage divider 3 is 1.0256410256;

[0029] If the bus voltage is 313.5 kV, the coefficient of the high-accuracy active two-stage inductive voltage divider 3 is 1.0526315789;

[0030] If the bus voltage is 338.25 kV, the coefficient of the high-accuracy active two-stage inductive voltage divider 3 is 0.9756097561;

[0031] If the bus voltage is 346.5 kV, the coefficient of the high-accuracy active two-stage inductive voltage divider 3 is 0.9523809524; and so on.

[0032] The use of the adjustable ratio voltage transformer 4 in the synchronous parallel operation makes it unnecessary for the synchronization device 5 to frequently change parameter information, and increases the conversion accuracy, making the operation more accurate, convenient and safe, improving the safety and accuracy of the quasi-synchronous parallel operation, and ensuring the safe and stable operation of the equipment.

[0033] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A voltage transformer based on an active two-stage inductive voltage divider, It is characterized in that The invention comprises a voltage transformer (2), wherein the primary side of the voltage transformer (2) is connected to a busbar (1), the secondary side of the voltage transformer (2) is connected to a high-accuracy active two-stage inductive voltage divider (3), the voltage transformer (2) and the high-accuracy active two-stage inductive voltage divider (3) are cascaded to form a high-precision variable ratio voltage transformer (4), the primary side of the variable ratio voltage transformer (4) is connected to the busbar, and the secondary side is connected to a synchronization device (5); The coefficient of the high-accuracy active two-stage inductive voltage divider (3) is adjustable in the range of 0.95 to 1.06; The voltage variation range of the busbar (1) is 330 kV (1±2*2.5%).

2. A voltage transformer based on an active two-stage inductive voltage divider as claimed in claim 1, It is characterized in that The high-accuracy active two-stage inductive voltage divider (3) has an excitation winding and an auxiliary winding wound in sequence at one end of the same excitation core, and a voltage winding wound after an additional iron core is superimposed at the other end.

3. A voltage transformer based on an active two-stage inductive voltage divider as claimed in claim 1, It is characterized in that The size of the exciting core of the high-accuracy active two-stage inductive voltage divider (3) is 55 mm×75 mm×12 mm.

4. A voltage transformer based on an active two-stage inductive voltage divider as claimed in claim 1, It is characterized in that The dimensions of the additional iron core of the high-accuracy active two-stage inductive voltage divider (3) are 46 mm×84 mm×7 mm.

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