Grid-connected system and method based on power sharing of parallelly operated synchronous motor units

Abstract

The application provides a grid-connected system and method based on parallel operation power sharing of synchronous motor units, and relates to the technical field of new energy and power engineering. The system comprises a new energy station power generation system and a parallel synchronous motor unit group, wherein the parallel synchronous motor unit group comprises at least two synchronous motor units with the same electrical parameters and connected in parallel; the first end of the parallel synchronous motor unit group is connected with the new energy station power generation system, and the second end is connected with the power grid. The method comprises connecting one end of all the synchronous motor units to the same power bus and applying excitation current to the motor at the end, and measuring the motor terminal voltage waveform after applying excitation current to the motor at the other end, adjusting the relative mechanical angle of the synchronous motor units according to the measurement results, ensuring that the relative mechanical angles of the motor units are equal, and realizing power sharing among the parallel synchronous motor units. The application can simplify the system structure, reduce the cost, and improve the reliability and flexibility of the new energy grid-connected system.

Description

Technical Field

[0001] This invention relates to the fields of new energy and power engineering technology, and more specifically, to a grid-connected system and method based on the equal distribution of power during parallel operation of synchronous motor units. Background Technology

[0002] With the rapid development of new energy power generation technologies, the installed capacity of new energy plants (such as wind farms and photovoltaic power stations) is constantly increasing. New energy power generation is characterized by intermittency, volatility, and uncertainty, and its large-scale grid connection poses challenges to the stable operation of the power system. To improve the grid connection performance of new energy sources and the stability of the power grid, synchronous motor-generator pairs have been proposed as an effective solution.

[0003] An existing patent (application number CN202011296820.1) proposes a synchronous motor-generator pair for frequency conversion in low-frequency power transmission. The synchronous motor-generator pair mainly consists of a synchronous motor, a synchronous generator, and their auxiliary systems. Connected between the renewable energy plant and the power grid, the synchronous motor-generator pair performs frequency conversion while endowing the renewable energy plant with the characteristics of a traditional synchronous motor, providing inertia and reactive power support for the power system and improving its stability. However, with the continuous increase in the power output of renewable energy plants, the transmission power also increases accordingly. The capacity of a single synchronous motor-generator pair is often insufficient to meet the demand, requiring the use of two or more synchronous motor-generator pairs to transmit power from renewable energy plants.

[0004] When multiple synchronous motor-generator pairs are used, uneven power distribution will severely affect unit operation and reduce unit utilization efficiency. To solve the power distribution problem, such as... Figure 1 As shown, the power generation equipment in a new energy power plant can be grouped according to the capacity of synchronous motor-generator pairs, and each pair can be connected to its respective synchronous motor-generator pair before being connected to the power system. While this method avoids the difficulty of power distribution when two synchronous motor-generator pairs are directly connected in parallel, the connection method reveals that each synchronous motor-generator pair requires a complete electrical circuit, which undoubtedly increases the system's complexity and cost. For situations requiring multiple synchronous motor-generator pairs to transmit power, the system complexity will be further exacerbated, not only increasing equipment investment and operation and maintenance costs but also reducing system reliability and flexibility. Summary of the Invention

[0005] The present invention aims to solve at least one of the aforementioned technical problems existing in the prior art.

[0006] Therefore, the first aspect of the present invention provides a grid-connected system based on the equal distribution of power during parallel operation of synchronous motor units.

[0007] The second aspect of the present invention provides a grid connection method based on the equal distribution of power during parallel operation of synchronous motor units.

[0008] This invention provides a grid-connected system based on power sharing during parallel operation of synchronous motor units, comprising:

[0009] New energy power plant power generation system;

[0010] A parallel synchronous motor group includes at least two synchronous motor units, each synchronous motor unit comprising a synchronous motor and a synchronous generator coaxially connected. The synchronous motors in several synchronous motor units are connected in parallel at a first end, and the synchronous generators in several synchronous motor units are connected in parallel at a second end. The first end of the parallel synchronous motor group is connected to the power generation system of a new energy power station, and the second end of the parallel synchronous motor group is connected to the power grid.

[0011] Among them, the electrical parameters of several synchronous motor units are completely equal;

[0012] Furthermore, among several synchronous motor units, the relative mechanical angle between the stator winding axis of the synchronous motor and the stator winding axis of the synchronous generator remains equal.

[0013] Furthermore, among several synchronous motor units, the relative mechanical angles between the rotors of the synchronous motors and the rotors of the synchronous generators remain equal.

[0014] The grid-connected system based on the power sharing of synchronous motor units operating in parallel according to the above-described technical solution of the present invention may also have the following additional technical features:

[0015] After the new energy power stations are gathered locally, they are connected to the first end of the parallel synchronous motor unit group via a transformer, that is, the synchronous motors in several synchronous motor units are connected in parallel to the motor side bus.

[0016] The generator of the parallel synchronous motor group is connected in parallel to the generator side bus as the second terminal, and is connected to the power grid through a transformer, maintaining the same operating frequency as the power grid frequency.

[0017] In the above technical solution, the new energy power generation system includes offshore wind turbine generators and / or photovoltaic generators.

[0018] This invention provides a grid connection method based on power sharing during parallel operation of synchronous motor units, applicable to a grid connection system based on power sharing during parallel operation of synchronous motor units as described in any of the above technical solutions. The method includes:

[0019] Connect the synchronous generator in each synchronous motor unit to the same power bus, apply the same excitation current to all synchronous generators, and lock the synchronization after reaching the same set speed under the drive of the same power supply.

[0020] Apply excitation current to the synchronous motors in no-load operation and measure the terminal voltage waveform of each synchronous motor;

[0021] Select one synchronous motor unit as the reference group and the rest of the synchronous motor units as the adjustment group. Based on the difference in the terminal voltage waveforms of the synchronous motors measured in the adjustment group and the reference group, obtain the electrical angle lead or lag value of the terminal voltage of the adjustment group relative to the reference group.

[0022] Calculate the mechanical angle deviation of the adjustment group based on the lead or lag value of the terminal voltage electrical angle of the adjustment group relative to the reference group;

[0023] The rotor of the synchronous motor in the adjustment group is rotated relative to the rotor of the synchronous generator according to the mechanical angle deviation value, so that the initial value of the relative angle between the rotors in the adjustment group is equal to the initial value of the relative angle between the rotors in the reference group.

[0024] After the above adjustments are completed, then according to Figure 2 Connect to achieve average power distribution in parallel.

[0025] In the above technical solution, the method for calculating the mechanical angle deviation value of the adjustment group includes:

[0026]

[0027] in, This indicates the mechanical angle deviation value of the adjustment group; This indicates the lead or lag value of the terminal voltage electrical angle of the adjustment group relative to the reference group; This indicates the number of pole pairs in a synchronous motor.

[0028] The present invention provides another grid-connected method based on power sharing in parallel operation of synchronous motor units, applicable to a grid-connected system based on power sharing in parallel operation of synchronous motor units as described in any of the above technical solutions, the method comprising:

[0029] Connect the synchronous motors in each synchronous motor unit to the same power bus, apply the same excitation current to all synchronous motors, and lock the synchronization after they reach the same set speed under the drive of the same power supply.

[0030] Apply excitation current to the synchronous generators in no-load operation and measure the terminal voltage waveform of each synchronous generator;

[0031] Select one synchronous motor unit as the reference group and the rest of the synchronous motor units as the adjustment group. Based on the difference in the terminal voltage waveforms of the synchronous generators measured in the adjustment group and the reference group, obtain the electrical angle lead or lag value of the terminal voltage of the adjustment group relative to the reference group.

[0032] Calculate the mechanical angle deviation of the adjustment group based on the lead or lag value of the terminal voltage electrical angle of the adjustment group relative to the reference group;

[0033] The rotor of the synchronous generator in the adjustment group is rotated relative to the rotor of the synchronous motor according to the mechanical angle deviation value, so that the initial value of the relative angle between the rotors in the adjustment group is equal to the initial value of the relative angle between the rotors in the reference group.

[0034] After the above adjustments are completed, then according to Figure 2 Connect to achieve average power distribution in parallel.

[0035] In the above technical solution, the method for calculating the mechanical angle deviation value of the adjustment group includes:

[0036]

[0037] in, This indicates the mechanical angle deviation value of the adjustment group; This indicates the lead or lag value of the terminal voltage electrical angle of the adjustment group relative to the reference group; This represents the number of pole pairs of a synchronous generator.

[0038] In summary, due to the adoption of the above-mentioned technical features, the beneficial effects of the present invention are:

[0039] Based on the grid connection system and method proposed in this invention, which is based on the power sharing of synchronous motor units in parallel operation, it is possible to reliably share active power when synchronous motor units with the same electrical parameters are in parallel operation, thereby maximizing the total power transmission after the synchronous motor units are in parallel.

[0040] Specifically, based on the system and method of this invention, when connecting new energy sources to the grid, new energy power plants, such as wind turbines and photovoltaic units, do not need to be grouped by capacity. This improves the networking flexibility and operational freedom of new energy power plant units, reduces the networking cost of new energy power plant units, and increases the utilization rate of new energy power plant units.

[0041] The present invention can effectively reduce the number of circuits in power transmission lines, save the land occupied by cables and cable corridors, and thus reduce the cost of power transmission lines.

[0042] By maximizing the total power transmission of the synchronous motor units after parallel connection, the reliability and operational flexibility of the parallel system of multiple synchronous motor units are effectively improved.

[0043] Additional aspects and advantages of the invention will become apparent in the following description or may be learned by practice of the invention. Attached Figure Description

[0044] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0045] Figure 1 This is a schematic diagram of the structure of the new energy field after it is grouped and connected to the grid by synchronous motor units.

[0046] Figure 2 This is a schematic diagram of a grid-connected system based on the power sharing of synchronous motor units operating in parallel, according to an embodiment of the present invention.

[0047] Figure 3 This is a phasor diagram of synchronous motor unit operation in one embodiment of the present invention;

[0048] Figure 4 This is one of the schematic diagrams of rotor relative angle adjustment connection in a grid connection method based on the power sharing of synchronous motor units in parallel operation according to an embodiment of the present invention;

[0049] Figure 5 This is a schematic diagram of the terminal voltage waveform of the synchronous motor in a grid connection method based on the power sharing of synchronous motor units in parallel operation according to an embodiment of the present invention.

[0050] Figure 6 This is the second schematic diagram of rotor relative angle adjustment connection in a grid connection method based on the power sharing of synchronous motor units in parallel operation according to an embodiment of the present invention;

[0051] Figure 7 This is a schematic diagram of the terminal voltage waveform of the synchronous generator in a grid connection method based on the power sharing of synchronous motor units in parallel operation according to an embodiment of the present invention. Detailed Implementation

[0052] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0053] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0054] The following reference Figures 2 to 7 This describes a grid-connected system and method based on the equal distribution of power during parallel operation of synchronous motor units, provided by some embodiments of the present invention.

[0055] Some embodiments of this application provide a grid-connected system based on the equal distribution of power in parallel operation of synchronous motor units.

[0056] like Figure 2 As shown, the first embodiment of the present invention proposes a grid-connected system based on the equal distribution of power in parallel operation of synchronous motor units, which includes at least a new energy power generation system and a group of parallel synchronous motor units.

[0057] It is understandable that new energy power plants can be wind farms, photovoltaic power plants, etc. In this disclosure, a parallel connection of a wind farm and a photovoltaic power plant is used as an example for specific explanation. That is, the power generation system of a new energy power plant includes several wind turbine generators and several photovoltaic power generation devices. Figure 2 (As shown) After being collected locally, it is connected to the first end of the parallel synchronous motor group via a long-distance transmission system.

[0058] A parallel synchronous motor group includes at least two synchronous motor units (i.e., the synchronous motor-generator pair mentioned above). Each synchronous motor unit includes a synchronous motor and a synchronous generator connected in series. The synchronous motors in several synchronous motor units are connected in parallel to the first end of the parallel synchronous motor group, and the synchronous generators in several synchronous motor units are connected in parallel to the second end of the parallel synchronous motor group. The first end of the parallel synchronous motor group is connected to the power generation system of the new energy power station, and the second end of the parallel synchronous motor group is connected to the power grid.

[0059] Figure 2 A schematic diagram of parallel operation of a parallel synchronous motor unit group with multiple synchronous motor units is shown. The number of synchronous motor units connected in parallel can be set based on the power output of the renewable energy plant and the upper capacity limit of the synchronous motor units. At a minimum, the sum of the upper capacity limits of several synchronous motor units should be greater than the total power output of the renewable energy plant connected, and a margin requirement should be met. This disclosure primarily uses a parallel synchronous motor unit group with two synchronous motor units as an example for illustration.

[0060] More specifically, the parallel synchronous motor unit group also includes a motor-side bus and a generator-side bus. The motor-side bus serves as the first end of the parallel synchronous motor unit group, with synchronous motors from several synchronous motor units connected in parallel to the motor-side bus; the generator-side bus serves as the second end of the parallel synchronous motor unit group, with synchronous generators from several synchronous motor units connected in parallel to the generator-side bus.

[0061] In some embodiments, the long-distance transmission system includes a step-up transformer, a transmission cable, and a step-down transformer.

[0062] The step-up transformer has a first terminal and a second terminal. The first terminal of the step-up transformer is connected to the collection terminal of several new energy power generation systems. The step-up transformer steps up the voltage at its first terminal to a first voltage level. The transmission cable has a first terminal and a second terminal. The first terminal of the transmission cable is connected to the second terminal of the step-up transformer. The step-down transformer has a first terminal and a second terminal. The first terminal of the step-down transformer is connected to the second terminal of the transmission cable. The second terminal of the step-down transformer is connected to the first terminal of the parallel synchronous motor group of the power sharing device. The step-down transformer steps down the voltage at its first terminal to a second voltage level.

[0063] The power frequency step-up transformer has a first terminal and a second terminal. The first terminal of the power frequency step-up transformer is connected to the second terminal of the parallel synchronous motor group of the power sharing device, and the second terminal of the power frequency step-up transformer is connected to the power grid. The power frequency step-up transformer steps up the voltage of its first terminal to the power grid voltage level and maintains the same operating frequency as the power grid. The power grid frequency is usually 50Hz or 60Hz.

[0064] It should be noted that long-distance transmission systems are primarily suitable for the grid connection needs of distant offshore wind farms. Furthermore, due to the requirements of long-distance power transmission, long-distance transmission systems typically employ low-frequency, high-voltage transmission methods (e.g., 15-20Hz). Based on the above configuration, such as... Figure 2 As shown, the offshore wind farms do not need to be grouped. After being gathered at sea, they are directly connected to the land-side bus via the offshore low-frequency step-up transformer and submarine cable. Then, after being gathered to the motor-side bus via the low-frequency step-down transformer, they drive synchronous motors M1 and M2. The synchronous motors drive synchronous generators G1 and G2 connected coaxially, and are connected to the power frequency grid via the power frequency step-up transformer.

[0065] Figure 3 The operating phasor diagram of the synchronous motor unit is shown, with the axis of the A-phase winding of the synchronous motor and the axis of the A-phase winding of the synchronous generator as references.

[0066] Specifically, the operation analysis of the synchronous motor unit is as follows.

[0067] The active power output of the synchronous generator and synchronous motor in each synchronous motor unit is as follows:

[0068]

[0069]

[0070] in, This represents the active power output of the synchronous generator; This represents the excitation electromotive force of a synchronous generator; This indicates the voltage of the synchronous generator side bus. This represents the synchronization reactance of a synchronous generator; Indicates the power angle of a synchronous generator; This indicates the active power output of the synchronous motor; This represents the magnetizing electromotive force of a synchronous motor. This indicates the bus voltage on the synchronous motor side; This represents the synchronous reactance of a synchronous motor; Indicates the power angle of a synchronous motor;

[0071] The power angles of synchronous generators and synchronous motors are:

[0072]

[0073]

[0074] in, This indicates the number of pole pairs of a synchronous generator; The mechanical angle of a synchronous generator; Electrical angle representing the voltage at the synchronous generator side bus; Electrical angle representing the voltage at the busbar on the synchronous motor side; Indicates the number of pole pairs of a synchronous motor; The mechanical angle of a synchronous motor;

[0075] in:

[0076]

[0077]

[0078] in, Indicates the rotation angle of the motor rotor; Indicates time; This represents the angular velocity of the synchronous motor unit, which can be understood as... It is the time derivative of the rotation angle of the motor rotor. Since the stators of the synchronous motor and the synchronous generator in the synchronous motor unit are in a fixed relative position and the rotors are coaxial, they have the same angular velocity. This represents the moment of inertia of the synchronous motor unit; This indicates the electromagnetic power of the synchronous motor; This represents the electromagnetic power of the synchronous generator.

[0079] Based on the above analysis, since several synchronous generator units are connected in parallel, the synchronous generator side bus voltage of all synchronous generator units... Equal, synchronous motor side bus voltage Equal electrical angle of the synchronous motor side bus voltage Equal, and the electrical angle of the synchronous generator side bus voltage. equal.

[0080] To ensure an even power distribution among all synchronous motor units, the following two points must be guaranteed:

[0081] 1. Several synchronous generator units have completely identical electrical parameters; that is, when the excitation current of the synchronous generator is the same, the excitation electromotive force of the synchronous generator in each synchronous generator unit is the same. Equal, synchronous reactance of synchronous generator Equal; when the excitation current of the synchronous motors is the same, the excitation electromotive force of the synchronous motors in each synchronous motor unit is equal. Equal, synchronous reactance of synchronous motor equal.

[0082] 2. The power angle of each synchronous motor during the operation of several synchronous motor units. Keeping them equal, the power angle of each synchronous generator To maintain equality, it is necessary to ensure that the mechanical angles of the synchronous motors in several synchronous motor units are equal. Keeping them equal, the mechanical angles of the synchronous generators in several synchronous motor units The relative mechanical angles in the several synchronous motor units remain equal, and the relative mechanical angles are the relative angles between the synchronous motor rotor and the synchronous generator rotor in each synchronous motor unit.

[0083] More specifically, since the mechanical angles of the synchronous motor, the mechanical angles of the synchronous generator, and the relative mechanical angles within the synchronous motor unit are all mechanical angles, as long as their initial angles are the same, the equality of the mechanical angles of the synchronous motors, the equality of the mechanical angles of the synchronous generators, and the equality of the relative mechanical angles within the synchronous motor unit will always hold true during operation.

[0084] Based on the above configuration, the power can be evenly distributed when multiple synchronous motor units are running in parallel, thereby maximizing the total power transmission of the parallel synchronous motor units.

[0085] Other embodiments of the present invention provide a grid connection method based on power sharing in parallel operation of synchronous motor units, which is applied to a grid connection system based on power sharing in parallel operation of synchronous motor units as described in any of the above embodiments. The method uses the parameters of one of the synchronous motor units as a standard and mechanically adjusts the initial value of the relative mechanical angle to make the electrical parameters of the synchronous motor units completely identical, thereby achieving power sharing in parallel operation of multiple synchronous motor units. Specifically, the method includes the following steps S11-S15.

[0086] S11. Connect the synchronous generators in each synchronous motor unit to the same power bus, apply the same excitation current to all synchronous generators, and after reaching the same set speed under the drive of the same power supply, lock the synchronization. Figure 4 As shown.

[0087] S12. Apply excitation current to the synchronous motors in no-load operation and measure the terminal voltage waveform of each synchronous motor. Figure 4 In this example, we will use a system consisting of two synchronous motor units, labeled 1# and 2#. The terminal voltage of 1# is the terminal voltage of synchronous motor M1 in 1# synchronous motor unit. Similarly, the terminal voltage of 2# is the terminal voltage of synchronous motor M2 in 2# synchronous motor unit. The waveforms of the terminal voltages of the two synchronous motors are shown below. Figure 6 As shown.

[0088] S13. Select one synchronous motor unit as the reference group and the rest of the synchronous motor units as the adjustment group. Based on the difference in the terminal voltage waveforms of the synchronous motors measured in the adjustment group and the reference group, obtain the electrical angle lead or lag value of the terminal voltage of the adjustment group relative to the reference group.

[0089] S14. Calculate the mechanical angle deviation of the adjustment group based on the lead or lag value of the terminal voltage electrical angle of the adjustment group relative to the reference group.

[0090] In some embodiments, the method for calculating the mechanical angle deviation value of the adjustment group includes:

[0091]

[0092] in, This indicates the mechanical angle deviation value of the adjustment group; This indicates the lead or lag value of the terminal voltage electrical angle of the adjustment group relative to the reference group; This indicates the number of pole pairs in a synchronous motor.

[0093] S15. Adjust the rotation of the rotor of the synchronous motor in the adjustment group relative to the rotor of the synchronous generator according to the mechanical angle deviation value, so that the initial value of the mechanical angle of the adjustment group is equal to the initial value of the mechanical angle of the reference group.

[0094] Specifically, such as Figure 5 As shown, taking the No. 1 synchronous motor unit as the reference group, it can be seen that the electrical angle of the synchronous motor terminal voltage of the No. 2 synchronous motor unit is relatively ahead, and the measured electrical angle lead value is... Then the mechanical angle deviation (lead value) of the No. 2 synchronous motor unit is: Therefore, the rotor of the synchronous motor in the No. 2 synchronous motor unit is rotated in the opposite direction to the rotor of the synchronous generator. Then, connect and fix the rotor shaft. If the No. 2 synchronous motor unit is used as the reference group, the terminal voltage of the synchronous motor in the No. 1 synchronous motor unit is relatively lagging behind. Therefore, the rotor of the synchronous motor in the No. 1 synchronous motor unit should be rotated in the positive direction of rotation relative to the rotor of the synchronous generator. Then, connect and fix the rotor shaft.

[0095] After the above rotational adjustment, it is necessary to return to step S11 and remeasure the terminal voltage waveform of the synchronous motor until the electrical angle of the terminal voltage between the reference group and the adjustment group is either leading or lagging by a certain value. This means that the initial relative angles of the rotors of the two synchronous motor units are equal. By then putting the synchronous motor units into operation, the active power of the system can be evenly distributed at all times.

[0096] Other embodiments of the present invention provide another grid-connected method based on power sharing in parallel operation of synchronous motor units, which is applied to the grid-connected system based on power sharing in parallel operation of synchronous motor units as described in any of the above embodiments. The method uses the parameters of one of the synchronous motor units as a standard and mechanically adjusts the initial value of the relative mechanical angle to make the electrical parameters of the synchronous motor units completely identical, thereby achieving power sharing when multiple synchronous motor units are running in parallel. Specifically, the method includes the following steps S21-S25.

[0097] S21. Connect the synchronous motors in each synchronous motor unit to the same power bus, apply the same excitation current to all synchronous motors, and after they reach the same set speed under the drive of the same power supply, lock the synchronization. Figure 6 As shown.

[0098] S22. Apply excitation current to the synchronous generators in no-load operation and measure the terminal voltage waveform of each synchronous generator. Figure 6 In this example, we will use a system consisting of two synchronous generator units, labeled 1# and 2#. The terminal voltage of generator #1 is the terminal voltage of synchronous generator G1 in generator #1. Similarly, the terminal voltage of generator #2 is the terminal voltage of synchronous generator G2 in generator #2. The waveforms of the terminal voltages of the two synchronous generators are shown below. Figure 7 As shown.

[0099] S23. Select one synchronous motor unit as the reference group and the rest of the synchronous motor units as the adjustment group. Based on the difference in the terminal voltage waveforms of the synchronous generators measured in the adjustment group and the reference group, obtain the electrical angle lead or lag value of the terminal voltage of the adjustment group relative to the reference group.

[0100] S24. Calculate the mechanical angle deviation of the adjustment group based on the lead or lag value of the terminal voltage electrical angle of the adjustment group relative to the reference group.

[0101] In some embodiments, the method for calculating the mechanical angle deviation value of the adjustment group includes:

[0102]

[0103] in, This indicates the mechanical angle deviation value of the adjustment group; This indicates the lead or lag value of the terminal voltage electrical angle of the adjustment group relative to the reference group; This represents the number of pole pairs of a synchronous generator.

[0104] S25. Adjust the rotation of the rotor of the synchronous generator in the adjustment group relative to the rotor of the synchronous motor according to the mechanical angle deviation value, so that the initial value of the mechanical angle of the adjustment group is equal to the initial value of the mechanical angle of the reference group.

[0105] Specifically, such as Figure 7 As shown, taking the No. 1 synchronous generator unit as the reference group, it can be seen that the electrical angle of the generator terminal voltage of the No. 2 synchronous generator unit is relatively ahead, and its electrical angle lead value is measured to be... Then the mechanical angle deviation (lead value) of the No. 2 synchronous motor unit is: Therefore, the rotor of the synchronous generator in the No. 2 synchronous motor unit is rotated in the opposite direction to the rotor of the synchronous motor. Then, connect and fix the rotor shaft. If the No. 2 synchronous motor unit is used as the reference group, the terminal voltage of the synchronous generator of the No. 1 synchronous motor unit is relatively lagging behind. Therefore, the rotor of the synchronous generator in the No. 1 synchronous motor unit should be rotated in the positive direction of rotation relative to the rotor of the synchronous motor. Then, connect and fix the rotor shaft.

[0106] After the above rotational adjustment, it is necessary to return to step S21 and remeasure the synchronous generator terminal voltage waveform until the electrical angle of the terminal voltage between the reference group and the adjustment group is either leading or lagging by a certain value. This means that the initial relative angles of the rotors of the two synchronous motor units are equal. By then putting the synchronous motor units into operation, the active power of the system can be evenly distributed at all times.

[0107] In this specification, the illustrative expressions of the terms used do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0108] Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention shall be included within the scope of protection of this invention.

Claims

1. A grid-connected method based on power sharing of parallel operation of synchronous machine units, characterized in that, The application is applied to a grid-connected system based on parallel operation of synchronous motor units for power sharing, and the system comprises: a new energy station power generation system; a parallel synchronous motor unit group comprising at least two synchronous motor units, the synchronous motor units comprising coaxially connected synchronous motors and synchronous generators, the synchronous motors in the synchronous motor units being connected in parallel to a first end of the parallel synchronous motor unit group, the synchronous generators in the synchronous motor units being connected in parallel to a second end of the parallel synchronous motor unit group, the first end of the parallel synchronous motor unit group being connected to the new energy station power generation system, and the second end of the parallel synchronous motor unit group being connected to a power grid; wherein the electrical parameters of the synchronous motor units are completely equal; furthermore, the relative mechanical angles between the stator winding axes of the synchronous motors and the stator winding axes of the synchronous generators in the synchronous motor units are kept equal; furthermore, the relative mechanical angles between the rotors of the synchronous motors and the rotors of the synchronous generators in the synchronous motor units are kept equal; the method comprises: connecting the synchronous generators in each synchronous motor unit to the same power supply bus, applying the same size of excitation current to all the synchronous generators, and locking the synchronous generators after reaching the same set speed under the driving of the same power supply; applying excitation current to the synchronous motors in the idle state, and measuring the terminal voltage waveform of each synchronous motor; selecting one synchronous motor unit as a reference group and the rest as an adjustment group, obtaining the leading or lagging value of the terminal voltage electrical angle of the adjustment group relative to the reference group according to the difference between the terminal voltage waveforms of the synchronous motors in the adjustment group and the reference group; calculating the mechanical angle deviation value of the adjustment group according to the leading or lagging value of the terminal voltage electrical angle of the adjustment group relative to the reference group; rotating the rotor of the synchronous motor in the adjustment group relative to the rotor of the synchronous generator to make the initial value of the relative angle of the rotor of the adjustment group equal to the initial value of the relative angle of the rotor of the reference group according to the mechanical angle deviation value.

2. The grid-connected method based on parallel operation of synchronous machine units for power sharing according to claim 1, characterized in that, The several new energy station power generation systems are coupled to the first end of the power sharing device after being collected locally and transmitted through a long-distance transmission system.

3. The grid-connected method of claim 2, wherein, The long-distance transmission system comprises: a step-up transformer having a first end and a second end, the first end of the step-up transformer being coupled to the collection end of the several new energy station power generation systems, and the step-up transformer being configured to step up the voltage at the first end to a first voltage level; a transmission cable having a first end and a second end, the first end of the transmission cable being coupled to the second end of the step-up transformer; a step-down transformer having a first end and a second end, the first end of the step-down transformer being coupled to the second end of the transmission cable, the second end of the step-down transformer being coupled to the first end of the power sharing device, and the step-down transformer being configured to step down the voltage at the first end to a second voltage level.

4. The grid-connected method of claim 3, wherein, The power sharing device further comprises: a motor side bus as the first end of the power sharing device, and the synchronous motors in the synchronous motor units being connected in parallel to the motor side bus; a generator side bus as the second end of the power sharing device, and the synchronous generators in the synchronous motor units being connected in parallel to the generator side bus.

5. The grid-connected method of claim 1, wherein, Further comprising: The power frequency step-up transformer has a first end and a second end, the first end of the power frequency step-up transformer is coupled with the second end of the power sharing device, the second end of the power frequency step-up transformer is coupled with the power grid, the power frequency step-up transformer steps up the voltage at the first end to the voltage level of the power grid, and maintains the same working frequency as the power grid.

6. The grid-connected method of claim 1, wherein, The new energy station power generation system comprises a wind turbine generator set and / or a photovoltaic generator set.

7. The grid-connected method of claim 1, wherein, The method for calculating the mechanical angle deviation value of the adjustment group comprises: wherein, represents a mechanical angle deviation value of the adjustment group; represents a mechanical voltage angle lead or lag value of the adjustment group relative to the reference group; represents a pole pair number of the synchronous motor.

8. A grid-connected method based on power sharing of parallel operation of synchronous motor units, applied to a grid-connected system based on power sharing of parallel operation of synchronous motor units, characterized in that, The system comprises: A new energy station power generation system; A parallel synchronous motor group comprising at least two synchronous motor groups, the synchronous motor group comprising a synchronous motor and a synchronous generator coaxially connected, the synchronous motors in the plurality of synchronous motor groups being connected in parallel to a first end of the parallel synchronous motor group, the synchronous generators in the plurality of synchronous motor groups being connected in parallel to a second end of the parallel synchronous motor group, the first end of the parallel synchronous motor group being connected to the new energy station power generation system, and the second end of the parallel synchronous motor group being connected to the power grid; wherein the electrical parameters of the plurality of synchronous motor groups are completely equal; further wherein the relative mechanical angle between the stator winding axis of the synchronous motor and the stator winding axis of the synchronous generator in the plurality of synchronous motor groups is equal; further wherein the relative mechanical angle between the rotor of the synchronous motor and the rotor of the synchronous generator in the plurality of synchronous motor groups is equal; The method comprises: connecting the synchronous motor in each synchronous motor group to the same power bus, applying the same size of excitation current to all synchronous motors, and locking the synchronization after reaching the same set speed under the driving of the same power supply; applying excitation current to the synchronous generator in the no-load operation state, and measuring the terminal voltage waveform of each synchronous generator; selecting one synchronous motor group as a reference group and the remaining synchronous motor groups as adjustment groups, obtaining the terminal voltage electrical angle leading value or lag value of the adjustment groups relative to the reference group according to the difference between the terminal voltage waveforms of the synchronous generators in the adjustment groups and the reference group; calculating the mechanical angle deviation value of the adjustment groups according to the terminal voltage electrical angle leading value or lag value of the adjustment groups relative to the reference group; rotating the rotor of the synchronous generator in the adjustment group relative to the rotor of the synchronous motor in the adjustment group according to the mechanical angle deviation value, so that the initial value of the rotor relative angle of the adjustment group is equal to the initial value of the rotor relative angle of the reference group.

9. The grid-connected method of claim 8, wherein, The method for calculating the mechanical angle deviation value of the adjustment group comprises: wherein, represents a mechanical angle deviation value of the adjustment group; represents a mechanical voltage angle lead or lag value of the adjustment group relative to the reference group; represents a pole pair number of the synchronous generator.

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