Speed change transformation method and system of direct grid-connected synchronous generator set

Abstract

The invention discloses a variable speed transformation method and system of a direct grid-connected synchronous generator set. The method comprises the following steps that a full-power converter is additionally arranged between a synchronous generator and a transformer in an original power generation system, a stator winding of the synchronous generator is connected with a motor side module of the full-power converter, and a power grid side module of the full-power converter is connected with a generator side winding of the transformer; the number of parallel branches and the number of turns of the stator winding are adjusted, so that the adjusted outlet voltage of the synchronous generator is matched with the voltage of the motor side module of the full-power converter; the voltage of the generator side winding of the transformer is matched with the voltage of the power grid side module of the full-power converter, and the voltage of the power grid side winding of the transformer is matched with the voltage of the power grid. The transformed generator set can operate at a variable speed, the operation efficiency of a prime motor and the whole generator set is improved, the operation condition of the original generator set is improved, and the capacity and the operation stability of the generator set are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fixed-speed constant-frequency and variable-speed constant-frequency power generation, and particularly relates to a variable-speed transformation method and system of a direct grid-connected synchronous generator set. BACKGROUND

[0002] The synchronous generator set has been widely applied in energy development such as hydroelectric power generation, wind power generation, thermal power generation, etc. due to its large capacity, adjustable active power and reactive power, etc. However, due to the constraints of power grid frequency and power grid operation, the prime mover driving the direct grid-connected synchronous generator always operates at a synchronous speed, which cannot always be at an optimal speed, thereby leading to deterioration of the working condition of the generator set, reduction of efficiency, and affecting the safe operation of the generator set.

[0003] With the development of current energy development, in order to improve the energy conversion efficiency of the prime mover, variable-speed power generation is widely used in the development of clean energy such as wind power generation, tidal power generation and wave power generation, and the speed of the prime mover will change within a certain range to improve the energy conversion efficiency.

[0004] A variable-speed transformation method of a synchronous generator set is provided in a document (a synchronous generator set system of a doubly-fed asynchronous transformation-ZL201510618876.7), which needs to replace the generator rotor and add a converter, and the transformation has a large amount of engineering. SUMMARY

[0005] The present application provides a variable-speed transformation method and system of a direct grid-connected synchronous generator set, which improves the operation efficiency of the prime mover and the entire generator set, improves the operation condition of the original synchronous generator set, improves the capacity of the generator set, and improves the stability of the operation of the generator set.

[0006] The object of the present application is achieved at least by one of the following technical solutions.

[0007] A variable-speed transformation system of a direct grid-connected synchronous generator set, comprising a synchronous generator, a full-power converter, a transformer and a prime mover and a transmission mechanism thereof;

[0008] The prime mover and the transmission mechanism thereof, the synchronous generator, the full-power converter and the transformer are sequentially connected, and the transformer is externally connected to a power grid.

[0009] The alternating current output by the synchronous generator is sent to the full-power converter for rectification and inversion, then sent to the transformer for voltage transformation, and finally sent to the power grid.

[0010] Further, the synchronous generator comprises a stator winding and a rotor, and the prime mover and the transmission mechanism thereof drive the rotor of the synchronous generator to rotate; the stator winding is connected to the full-power converter.

[0011] Further, the full power converter comprises a motor side module and a grid side module, the stator winding of the synchronous generator is connected with the motor side module, and the transformer is connected with the grid side module.

[0012] Further, the transformer comprises a generator side winding and a grid side winding, the generator side winding is connected with the grid side module of the full power converter, and the grid side winding is connected with the grid.

[0013] Further, the voltage of the synchronous generator outlet matches the voltage of the motor side module of the full power converter, and if not matched, the number of parallel branches and the number of turns of the stator winding of the synchronous generator need to be adjusted.

[0014] Further, the voltage of the generator side winding of the transformer matches the voltage of the grid side module of the full power converter, and the voltage of the grid side winding of the transformer matches the grid voltage.

[0015] Further, in the prime mover and its transmission mechanism, the prime mover is a power equipment for driving the synchronous generator to rotate.

[0016] A variable speed reconstruction method of a direct grid-connected synchronous generator set, comprising the following steps:

[0017] S1, a full power converter is added between the synchronous generator and the transformer in the original power generation system, the stator winding of the synchronous generator is connected with the motor side module of the full power converter, and the grid side module of the full power converter is connected with the generator side winding of the transformer;

[0018] S2, the number of parallel branches and the number of turns of the stator winding are adjusted, so that the outlet voltage of the adjusted synchronous generator matches the voltage of the motor side module of the full power converter;

[0019] S3, the voltage of the generator side winding of the transformer matches the voltage of the grid side module of the full power converter, and the voltage of the grid side winding of the transformer matches the grid voltage.

[0020] Further, in step S1, the original power generation system comprises a synchronous generator, a transformer, and a prime mover and its transmission mechanism;

[0021] The prime mover and its transmission mechanism drive the rotor of the synchronous generator to rotate, the stator winding of the synchronous generator is connected with the generator side winding of the transformer, and the grid side winding of the transformer is connected with the grid.

[0022] Further, in step S3, the transformer is replaced or the generator side winding of the transformer is adjusted, so that the voltage of the generator side winding of the adjusted or replaced transformer matches the voltage of the grid side module of the full power converter, and the voltage of the grid side winding of the transformer matches the grid voltage.

[0023] Compared with the prior art, the application has the following advantages and effects:

[0024] The application is simple and easy to implement.

[0025] The application retains most of the devices and components of the original synchronous generator system, only adds a full-power converter, adjusts the number of parallel branches and the number of turns of the stator winding of the original synchronous generator, and replaces or adjusts the generator-side winding of the transformer, so that the modification of the original power generation system is small and the modification cost is low.

[0026] As described above, the technical means of the application is simple and easy to implement, and the synchronous generator is operated at different speeds, and the power output by the synchronous generator is sent to the transformer and the power grid through the full-power converter. Since the stator winding of the synchronous generator is no longer directly connected to the power grid, the speed of the synchronous generator is no longer restricted by the frequency of the power grid, and the speed of the prime mover driving the synchronous generator can be adjusted according to the operating condition, so that the prime mover always operates in the high-efficiency region, improves the operating efficiency of the prime mover and the entire power generation system, improves the operating condition of the original synchronous generator set, and improves the stability of the generator set operation. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The figure is a structure diagram of the power generation system before the embodiment of the application is modified.

[0028] Figure 2 The figure is a structure diagram of the power generation system after the embodiment of the application is modified.

[0029] Figure 3 The figure is a parallel branch structure diagram of the stator winding before the embodiment of the application is modified.

[0030] Figure 4 The figure is a parallel branch structure diagram of the stator winding after the embodiment of the application is modified.

[0031] Figure 5 The figure is a coil turn number diagram before the embodiment of the application is modified.

[0032] Figure 6 The figure is a coil turn number diagram after the embodiment of the application is modified. DETAILED DESCRIPTION

[0033] The application purpose of the application will be described in further detail below in combination with the drawings and specific embodiments, and the embodiments cannot be described one by one here, but the implementation manner of the application is not limited to the following embodiments.

[0034] Embodiment:

[0035] A variable-speed modification method of a direct grid-connected synchronous generator set, comprising the following steps:

[0036] S1, as Figure 2As shown, a full-power converter B is added between the synchronous generator A and the transformer C in the original power generation system. The stator winding A1 of the synchronous generator A is connected to the motor side module B1 of the full-power converter B, and the grid side module B2 of the full-power converter B is connected to the generator side winding C1 of the transformer C.

[0037] like Figure 1 As shown, the original power generation system includes a synchronous generator A, a transformer C, a prime mover, and its transmission mechanism D;

[0038] The prime mover and its transmission mechanism D drive the rotor of the synchronous generator A to rotate. The stator winding A1 of the synchronous generator A is connected to the generator-side winding C1 of the transformer C, and the grid-side winding C2 of the transformer C is connected to the power grid.

[0039] In this embodiment, a three-phase synchronous generator with a rated voltage of 6.3kV is connected to the power grid through a 6.3kV / 35kV three-phase transformer. Figure 3 As shown, the generator stator winding parameters are: double-layer lap winding, 324 stator slots, 60 poles, with 5 poles and 9 slots forming a group, totaling 12 groups, 2 parallel branches, and 6 groups connected in series in each branch. Figure 5 As shown, each coil has 4 turns. The low-voltage winding of the transformer consists of 12 coils connected in series. The full-power converter has a generator-side voltage of 1200V and a grid-side voltage of 1200V.

[0040] S2. Adjust the number of parallel branches and turns of stator winding A1 so that the output voltage of the adjusted synchronous generator A matches the voltage of the motor side module B1 of the full power converter B.

[0041] In this embodiment, as Figure 4 As shown, adjust the number of parallel branches and turns of stator winding A1. Adjust the number of parallel branches to 12, keeping the number of turns unchanged, or adjust the number of parallel branches to 6, as shown. Figure 6 The number of turns is adjusted to 2 at the end of the coil by short-circuiting and opening the circuit. The adjusted output voltage of synchronous generator A matches the voltage of motor side module B1 of full power converter B.

[0042] S3. Replace transformer C or adjust the generator-side winding C1 of transformer C so that the voltage of the generator-side winding C1 of the adjusted or replaced transformer C matches the voltage of the grid-side module B2 of the full-power converter B, and the voltage of the grid-side winding C2 of transformer C matches the grid voltage.

[0043] In this embodiment, as Figure 6As shown, the low-voltage side winding of the transformer is adjusted, 12 wire cakes connected in series are adjusted to form a group by connecting 2 wire cakes in series, and 6 groups are connected in parallel, so that the voltage of the generator side winding C1 of the adjusted or replaced transformer C is matched with the voltage of the grid side module B2 of the full-power converter B, and the voltage of the grid side winding C2 of the transformer C is matched with the grid voltage.

[0044] As described above, the application can be better implemented.

[0045] The embodiments of the application are not limited to the above examples, and any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principles of the application shall be equivalent replacement modes and shall be included in the protection scope of the application.

Claims

1. A variable speed retrofit system for a direct grid- connected synchronous generator set, characterized by, The synchronous generator (A), the full-power converter (B), the transformer (C) and the prime mover and its transmission mechanism (D) are connected in sequence. The prime mover and its transmission mechanism (D), the synchronous generator (A), the full-power converter (B) and the transformer (C) are connected in sequence, and the transformer (C) is externally connected to the power grid. The alternating current output by the synchronous generator (A) is sent to the full-power converter (B) for rectification and inversion, then to the transformer (C) for voltage transformation, and finally to the power grid.

2. A variable speed retrofit system for a direct grid- connected synchronous generator set according to claim 1, characterized in that, The synchronous generator (A) includes a stator winding (A1) and a rotor, and the prime mover and its transmission mechanism (D) drive the rotor of the synchronous generator (A) to rotate; the stator winding (A1) is connected to the full-power converter (B).

3. A variable speed retrofit system for a direct grid- connected synchronous generator set according to claim 2, characterized in that, The full-power converter (B) includes a motor-side module (B1) and a grid-side module (B2), the stator winding (A1) of the synchronous generator (A) is connected to the motor-side module (B1), and the transformer (C) is connected to the grid-side module (B2).

4. A variable speed retrofit system for a direct grid- connected synchronous generator set according to claim 3, characterized in that, The transformer (C) includes a generator-side winding (C1) and a grid-side winding (C2), the generator-side winding (C1) is connected to the grid-side module (B2) of the full-power converter (B), and the grid-side winding (C2) is connected to the power grid.

5. A variable speed retrofit system for a direct grid- connected synchronous generator set according to claim 4, wherein, The voltage at the outlet of the synchronous generator (A) matches the voltage of the motor-side module (B1) of the full-power converter (B), and if it does not match, the number of parallel branches and the number of turns of the stator winding (A1) of the synchronous generator (A) need to be adjusted.

6. A variable speed retrofit system for a direct grid- connected synchronous generator set according to claim 4, wherein, The voltage of the generator-side winding (C1) of the transformer (C) matches the voltage of the grid-side module (B2) of the full-power converter (B), and the voltage of the grid-side winding (C2) of the transformer (C) matches the voltage of the power grid.

7. A variable speed retrofit system for a direct grid- connected synchronous generator set according to claim 1, wherein, In the prime mover and its transmission mechanism (D), the prime mover is a power device that drives the synchronous generator (A) to rotate.

8. A method of variable speed retrofitting of a direct grid- connected synchronous generator set, characterized in that, The method comprises the following steps: S1, adding a full-power converter (B) between the synchronous generator (A) and the transformer (C) in the original power generation system, connecting the stator winding (A1) of the synchronous generator (A) to the motor-side module (B1) of the full-power converter (B), and connecting the grid-side module (B2) of the full-power converter (B) to the generator-side winding (C1) of the transformer (C); S2, adjusting the number of parallel branches and the number of turns of the stator winding (A1) so that the voltage at the outlet of the adjusted synchronous generator (A) matches the voltage of the motor-side module (B1) of the full-power converter (B); S3, matching the voltage of the generator-side winding (C1) of the transformer (C) with the voltage of the grid-side module (B2) of the full-power converter (B), and matching the voltage of the grid-side winding (C2) of the transformer (C) with the voltage of the power grid.

9. The variable speed retrofit method and system of a direct grid- connected synchronous generator set of claim 8, wherein, In step S1, the original power generation system includes a synchronous generator (A), a transformer (C) and a prime mover and its transmission mechanism (D); The prime mover and its transmission mechanism (D) drive the rotor of the synchronous generator (A) to rotate, the stator winding (A1) of the synchronous generator (A) is connected to the generator-side winding (C1) of the transformer (C), and the grid-side winding (C2) of the transformer (C) is connected to the power grid.

10. The variable speed retrofit method and system of a direct grid- connected synchronous generator set of claim 8, wherein, In step S3, the transformer (C) is replaced or the generator-side winding (C1) of the transformer (C) is adjusted, so that the voltage of the generator-side winding (C1) of the adjusted or replaced transformer (C) matches the voltage of the network-side module (B2) of the full-power converter (B), and the voltage of the network-side winding (C2) of the transformer (C) matches the grid voltage.

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