Design method of high-inertia double-fed phase modifier system

Abstract

The invention relates to the technical field of generators, in particular to a design method of a high-inertia doubly-fed phase modifier system, which comprises the following steps: determining the working state and energy flow of a high-inertia doubly-fed phase modifier, and extracting technical parameters of each component of the high-inertia doubly-fed phase modifier system according to active power adjusting time and reactive power adjusting capacity of the phase modifier; comprising a rotating speed range of a shaft system, flywheel inertia and motor capacity; according to the inertia and rotating speed range of the flywheel energy storage system, the flywheel rotor diameter, the bearing supporting system and the standby state of the steel flywheel are determined; designing the size of the doubly-fed motor, the pole slot matching and the size of an air gap, and calculating a magnetic circuit; the size comprises the inner diameter and the axial length of the stator of the doubly-fed motor. Aiming at the problems of poor reactive power regulation capability, insufficient inertia and the like of the new energy station, the inertia and energy storage support technology of the new energy station is researched, the grid-connected operation stability and safety of the new energy station are improved, and the reliability of a large power grid is ensured.

Description

Technical Field

[0001] The present application relates to the technical field of generators, and more specifically, to a design method for a high-inertia double-fed phase regulator system. Background Art

[0002] A new energy station is a collection of all equipment below the grid connection point of a wind farm or solar power station that is centrally connected to the power system, including transformers, busbars, lines, converters, energy storage, wind turbines, photovoltaic power generation equipment, reactive power regulation equipment and auxiliary equipment. It should provide a certain amount of inertia support to the system, but in actual applications there is often a lack of inertia, active power and frequency support capabilities.

[0003] The invention patent with publication number CN117856343A discloses a steady-state modeling method for energy storage to assist new energy in providing inertia support through a converter. Construct a control strategy for new energy to provide inertia support through a grid-type converter; construct a model for the inertia support capability of new energy controlled by a grid-type converter; construct a joint control strategy for energy storage to assist new energy in providing inertia support through a grid-type converter; construct a model for the inertia support capability of new energy assisted by energy storage. It can be seen that the patent establishes a steady-state model through the dynamic process of energy storage assisted new energy provided inertia support by controlled by a grid-type converter, so as to consider its inertia support capability in the subsequent dispatch of a high-proportion new energy power system.

[0004] However, the existing phase-converter mainly uses its reactive power support function to achieve grid voltage support. At the same time, the kinetic energy stored in its rotor helps to improve the total inertia of the power system. However, since the rotor inertia of the synchronous phase-converter is too low, it cannot provide sufficient inertia support for the grid. Therefore, the inertia, active power and frequency support capabilities of new energy stations, the improvement of the stability and safety of the grid-connected operation of new energy stations, and ensuring the reliability of the large power grid have become technical issues that need to be solved. Summary of the invention

[0005] In view of this, the present application provides a design method for a high-inertia double-fed phase-converter system to improve the stability and safety of grid-connected operation of new energy stations and ensure the reliability of the large power grid.

[0006] A design method for a high-inertia double-fed phase condenser system, the high-inertia double-fed phase condenser system comprising a double-fed motor, a steel flywheel, a bidirectional inverter, a high-voltage AC bus, an energy storage DC bus and an energy storage device;

[0007] The design method includes determining the working state and energy flow of the high-inertia double-fed phase regulator, and extracting the technical parameters of each component of the high-inertia double-fed phase regulator system according to the actual required active power regulation time and reactive power regulation capacity of the phase regulator, including the speed range of the shaft system, the flywheel inertia and the motor capacity;

[0008] Determine the flywheel rotor diameter, bearing support system and standby status of the steel flywheel according to the actual required inertia and speed range of the flywheel energy storage system;

[0009] The dimensions, pole slot matching, and air gap size of the doubly-fed motor are designed and the magnetic circuit is calculated; the dimensions include the inner diameter and axial length of the stator of the doubly-fed motor.

[0010] In one possible implementation, the method further includes conducting system performance verification;

[0011] This includes verifying whether the overall inertia support capacity, energy support capacity and system efficiency of the high-inertia double-fed phase-converter system meet the active power regulation time and reactive power regulation capacity required by the actual design;

[0012] If not, modify the design of the flywheel energy storage system and the doubly-fed generator, and re-conduct the system performance verification until the overall inertia support capacity, energy support capacity and system efficiency of the high-inertia doubly-fed phase-converter system meet the active power regulation time and reactive power regulation capacity required by the actual design.

[0013] In one possible implementation, after determining the diameter of the flywheel rotor of the flywheel energy storage system, the method further includes:

[0014] When the stress properties of the material used in the flywheel rotor reach a limit, the diameter of the flywheel rotor is increased to increase the inertia value of the unit mass of the material.

[0015] In one possible implementation, after determining the flywheel rotor diameter, bearing support system and standby status of the steel flywheel, the method further includes:

[0016] The rotor dynamic balancing method is used to test the size and phase of the rotor imbalance on a balancing machine before the flywheel rotor is put into operation;

[0017] The flywheel rotor is dynamically balanced by removing material from the flywheel rotor or applying balancing weights.

[0018] In one possible implementation, the size design of the doubly-fed motor also includes designing the aspect ratio of the doubly-fed motor to increase the inertia of the rotor of the doubly-fed motor.

[0019] In one possible implementation, the steel flywheel is connected to the doubly-fed motor through a coupling; the stator winding of the doubly-fed motor is directly connected to the power grid, and the rotor winding of the doubly-fed motor is connected to the power grid through a back-to-back bidirectional inverter for AC excitation; the DC output end of the back-to-back bidirectional inverter is connected to the energy storage DC bus; and the energy storage device is connected to the energy storage DC bus through a DC-DC converter.

[0020] In one possible implementation, the electrical part of the doubly-fed motor includes a doubly-fed motor and a back-to-back power converter; the back-to-back power converter includes a rotor-side converter, a DC link, and a grid-side converter.

[0021] In one possible implementation, when power flows from the grid to the rotor winding for excitation, the grid-side converter is a three-phase rectifier, which is used to feed the grid's fixed-frequency AC energy to the DC link after rectification; the DC link completes energy retention and decoupling and then sends it to the rotor-side converter; wherein, the rotor-side converter is an inverter, which is used to send the DC side energy to the rotor winding through three-phase inverter technology.

[0022] In one possible implementation, the steel flywheel is connected to the doubly-fed generator via a coupling; wherein the doubly-fed generator is placed horizontally, the steel flywheel is in the shape of a flat disc, and the diameter of the steel flywheel is greater than the diameter of the stator winding.

[0023] In one possible implementation, the rotor winding of the doubly-fed motor adopts AC excitation to achieve variable speed constant frequency.

[0024] Compared with the prior art, the technical solution provided by this application has the following beneficial effects:

[0025] The high-inertia doubly-fed phase-shifting system and its design method provided in this application realize bidirectional large-range rapid regulation of active power and reactive power, improve the stability and safety of grid-connected operation of new energy stations, ensure the reliability of large power grid operation, and also provide design guidance for future practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0027] Figure 1 A structural schematic diagram of a high-inertia double-fed phase regulator system is provided for Example 1 of the present application.

[0028] Figure 2 A schematic diagram of the structure of a high-inertia double-fed phase regulator provided in Example 1 of the present application.

[0029] Figure 3 This is a flow chart of a design method for a high-inertia double-fed phase-shifting system provided in Example 2 of the present application.

[0030] Figure 4This is a schematic diagram of the structure of a flywheel provided in Example 2 of the present application. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0032] Embodiment 1:

[0033] See also Figures 1-2 , is a structural diagram of a high-inertia double-fed phase condenser system provided in Example 1 of the present application. The high-inertia double-fed phase condenser system includes a double-fed motor, a steel flywheel, a bidirectional inverter, a high-voltage AC bus, an energy storage DC bus and other energy storage devices.

[0034] The steel flywheel is connected to the doubly-fed generator through a coupling, such as Figure 2 As shown in the figure, the doubly-fed machine is placed horizontally, and the flywheel is in the shape of a flat disc, with a diameter larger than the outer diameter of the stator. The stator winding of the doubly-fed machine is directly connected to the grid, and the rotor winding is connected to the grid through a back-to-back bidirectional inverter for AC excitation. The DC output end of the back-to-back bidirectional inverter is connected to the energy storage DC bus. Other energy storage devices are connected to the energy storage DC bus through a DC / DC converter.

[0035] The high-inertia doubly-fed phase regulator provided in the embodiment of the present application is designed by utilizing the advantages of adjustable excitation of the doubly-fed motor rotor and variable speed constant frequency power generation. The doubly-fed motor rotor adopts AC excitation, which can easily achieve variable speed constant frequency and flexibly adjust active power and reactive power.

[0036] The electrical part of the doubly-fed machine consists of two parts: the doubly-fed machine and the back-to-back power converter. The back-to-back power converter can be divided into three parts: the rotor-side converter, the DC link, and the grid-side converter. When power flows from the grid to the rotor winding for excitation, the grid-side converter is a three-phase rectifier, which feeds the grid's fixed-frequency AC energy to the DC link after rectification, and the DC link is sent to the rotor-side converter after energy retention and decoupling. The rotor-side converter is an inverter, which sends the DC-side energy to the three-phase rotor winding through three-phase inverter technology, generating a rotating three-phase synthetic magnetomotive force in space, thereby inducing magnetomotive force in the stator armature and completing energy conversion.

[0037] The characteristics of the doubly-fed motor are that its stator winding and rotor winding are both connected to the power grid. The stator winding is directly connected to the power grid, and the rotor winding is connected to the power grid through a back-to-back bidirectional inverter for AC excitation. The rotor winding can also feed energy to the power grid. The doubly-fed motor is controlled by the inverter for voltage matching, synchronization and phase control, and is quickly connected to the grid with basically no current shock. Since the rotor of the doubly-fed motor adopts AC voltage excitation, it has a flexible operation mode, with the characteristics of variable speed constant frequency operation, wide range of reactive power regulation, and generator-motor mode operation.

[0038] The high-inertia doubly-fed phase-shifting system provided in the present application is composed of a doubly-fed motor, a coupling and a steel flywheel. It will have reactive, inertia and active support capabilities at the same time, and realize a large-range and rapid two-way regulation of active power and reactive power, thereby improving the stability and safety of the grid-connected operation of new energy stations and ensuring the reliability of large power grid operation.

[0039] Embodiment 2:

[0040] See also Figure 3 , is a design method for a high inertia doubly-fed phase condenser system provided in Example 2 of the present application. Its main steps include: analysis of the high inertia doubly-fed phase condenser system, design of the flywheel energy storage system, electromagnetic design of the doubly-fed motor and system performance verification.

[0041] The analysis of the high-inertia doubly-fed phase-converter system described in this application studies and analyzes the working state and energy flow of the high-inertia doubly-fed phase-converter, and extracts the technical parameters of each component of the system according to actual requirements. Among them, the above-mentioned actual requirements include the active power adjustment time and reactive power adjustment capacity of the phase-converter. Based on the actual required active power adjustment time and reactive power adjustment capacity of the phase-converter, the technical parameters of each component of the high-inertia doubly-fed phase-converter system are extracted, including the speed range of the shaft system, the flywheel inertia and the motor capacity.

[0042] The design of the flywheel energy storage system described in this application includes researching and analyzing the rotor design, bearing support design, and efficiency improvement design of the flywheel energy storage system according to the requirements for the flywheel energy storage system in actual requirements. Among them, the requirements for the flywheel energy storage system in actual requirements include the inertia and speed range of the flywheel energy storage system.

[0043] The rotor design of the flywheel energy storage system includes the design of the flywheel rotor diameter of the steel flywheel. The rotor design is mainly based on the rotor speed and the material used for the flywheel rotor. After the material stress properties are used to the limit, the rotor diameter should be increased as much as possible to increase the inertia value of the unit mass material. Since most of the inertia of the cylinder is distributed on the outermost ring, removing the weight of the center of the cylinder can improve the material utilization rate.

[0044] See also Figure 4, is a schematic diagram of the structure of a flywheel provided in Example 2 of the present application. The flywheel adopts the form of internal holes to reduce the weight of the flywheel.

[0045] Bearing support is particularly important for flywheel systems. Flywheels are heavy and rotate at high speeds. By exploring the impact of different support systems on the performance of flywheel systems, a safe, reliable and economical support solution is comprehensively selected.

[0046] In addition, since the flywheel energy storage system works in a standby state for a long time, its efficiency in the standby state is also one of the parameters that must be considered.

[0047] Due to processing and manufacturing errors, it is difficult for the center of mass and the center of rotation of the flywheel rotor to completely coincide, resulting in the rotor being subjected to the centrifugal force caused by the rotation of the unbalanced mass, i.e., the mass imbalance force. In order to avoid the problem of excessive vibration caused by the unbalanced mass of the flywheel rotor and ensure the stable operation of the flywheel energy storage system within a wide speed range, certain technical means are needed to eliminate or reduce the unbalanced mass of the flywheel rotor.

[0048] Specifically, a rotor dynamic balancing method is used to test the size and phase of the rotor imbalance on a balancing machine before the rotor is put into operation, and the flywheel rotor is dynamically balanced by removing part of the flywheel rotor material or adding balancing blocks.

[0049] The electromagnetic design of the doubly-fed motor includes: the size design, pole-slot matching design, air gap size design, magnetic circuit calculation, etc.

[0050] As the whole system tends to have large inertia, the size determines the space size and material usage of the motor, which has an impact on the weight, cost, and even its performance and reliability. Among them, the size of the doubly-fed motor includes the inner diameter and axial length of the doubly-fed motor stator.

[0051] In order to make the inertia of the doubly-fed motor rotor as large as possible, the size design also needs to take into account the aspect ratio of the motor. The aspect ratio of the motor is selected according to the actual application scenario. In this application, since the motor is placed horizontally, the motor outer diameter is larger.

[0052] The pole-slot combination has a decisive influence on many performance characteristics of the motor and needs to be carefully selected in combination with the specific working conditions of the doubly-fed motor.

[0053] The air gap is the area where the motor transfers energy, and has a great impact on the cost and efficiency of the motor. For a doubly-fed motor, a smaller air gap length is beneficial to enhancing the motor power density, but due to manufacturing and process limitations, the air gap length cannot be set too small. A larger air gap length is beneficial to production and processing, reducing manufacturing costs, but it will increase magnetic energy loss and reduce motor performance.

[0054] Carry out system performance verification, including whether the overall inertia support capacity of the system, the energy support capacity of the system, the efficiency of the system, etc. meet the standards, and design the system layout, system support connection, etc. It should be noted that meeting the standards means meeting the two parameter requirements of active power adjustment time and reactive power adjustment capacity required by the actual design, which is determined according to different application scenarios. Failure to meet the standards means that the design of the motor and flywheel system is unreasonable, and the electromagnetic design of the motor and the flywheel need to be modified until the requirements are met.

[0055] Specifically, it is necessary to verify whether the overall inertia support capacity, energy support capacity and system efficiency of the high-inertia doubly-fed phase-converter system can meet the active power regulation time and reactive power regulation capacity required by the actual design.

[0056] If not, modify the design of the flywheel energy storage system and the doubly-fed generator, and re-conduct the system performance verification until the overall inertia support capacity, energy support capacity and system efficiency of the high-inertia doubly-fed phase-converter system meet the active power regulation time and reactive power regulation capacity required by the actual design.

[0057] The design method of the high inertia double-fed phase condenser system proposed in this application provides important design guidance for future practical applications. This design method has the following beneficial effects:

[0058] 1. Improve system stability: By designing high-inertia double-fed phase regulators, the system can show stronger stability when facing grid fluctuations or failures. The high-inertia design enables the phase regulator to absorb and release energy more effectively during the dynamic process, reducing grid oscillations, thereby improving the operating stability and reliability of the entire power system.

[0059] 2. Optimize reactive power control: The double-fed control strategy adopted by the double-fed phase-converter enables it to flexibly adjust reactive power output. In the power system, the balance of reactive power is crucial to voltage stability and power quality. This design method optimizes the double-fed control strategy so that the phase-converter can respond to the system reactive power demand more accurately, achieve precise control of reactive power, and improve power quality.

[0060] 3. Reduce operating costs: This design method fully considers the economic efficiency of the phase-shifting machine, and achieves efficient energy conversion and energy-saving operation through reasonable structural design and control strategy optimization. This helps to reduce the operating costs of the phase-shifting machine and improve the economic benefits of the power system.

[0061] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0062] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0063] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A design method for a high inertia double-fed phase condenser system, characterized in that: The high-inertia double-fed phase condenser system includes a double-fed generator, a steel flywheel, a bidirectional inverter, a high-voltage AC bus, an energy storage DC bus and an energy storage device; The design method comprises: determining the working state and energy flow of the high-inertia double-fed phase regulator, and extracting the technical parameters of each component of the high-inertia double-fed phase regulator system according to the actual required active power regulation time and reactive power regulation capacity of the phase regulator, including the speed range of the shaft system, the flywheel inertia and the motor capacity; Determine the flywheel rotor diameter, bearing support system and standby status of the steel flywheel according to the actual required inertia and speed range of the flywheel energy storage system; The dimensions, pole slot matching, and air gap size of the doubly-fed motor are designed and the magnetic circuit is calculated; the dimensions include the inner diameter and axial length of the stator of the doubly-fed motor.

2. The design method of a high inertia double-fed phase condenser system according to claim 1, characterized in that: The method also includes conducting system performance verification; This includes verifying whether the overall inertia support capacity, energy support capacity and system efficiency of the high-inertia double-fed phase-converter system meet the active power regulation time and reactive power regulation capacity required by the actual design; If not, modify the design of the flywheel energy storage system and the doubly-fed generator, and re-conduct the system performance verification until the overall inertia support capacity, energy support capacity and system efficiency of the high-inertia doubly-fed phase-converter system meet the active power regulation time and reactive power regulation capacity required by the actual design.

3. The design method of a high inertia double-fed phase condenser system according to claim 1, characterized in that: After determining the flywheel rotor diameter of the flywheel energy storage system, the method further includes: When the stress properties of the material used in the flywheel rotor reach a limit, the diameter of the flywheel rotor is increased to increase the inertia value of the unit mass of the material.

4. The design method of a high inertia double-fed phase condenser system according to claim 1, characterized in that: After determining the flywheel rotor diameter, bearing support system, and standby status of the steel flywheel, the method further includes: The rotor dynamic balancing method is used to test the size and phase of the rotor imbalance on a balancing machine before the flywheel rotor is put into operation; The flywheel rotor is dynamically balanced by removing material from the flywheel rotor or applying balancing weights.

5. The design method of a high inertia double-fed phase condenser system according to claim 1, characterized in that: The size design of the doubly-fed generator also includes designing the aspect ratio of the doubly-fed generator to increase the inertia of the rotor of the doubly-fed generator.

6. The design method of a high inertia double-fed phase condenser system according to claim 1, characterized in that: The steel flywheel is connected to the doubly-fed motor through a coupling; the stator winding of the doubly-fed motor is directly connected to the power grid, and the rotor winding of the doubly-fed motor is connected to the power grid through a back-to-back bidirectional inverter for AC excitation; the DC output end of the back-to-back bidirectional inverter is connected to the energy storage DC bus; the energy storage device is connected to the energy storage DC bus through a DC-DC converter.

7. The design method of a high inertia double-fed phase condenser system according to claim 6, characterized in that: The electrical part of the doubly-fed motor includes a doubly-fed motor and a back-to-back power converter; the back-to-back power converter includes a rotor-side converter, a DC link, and a grid-side converter.

8. The design method of a high inertia double-fed phase condenser system according to claim 6, characterized in that: When power flows from the grid to the rotor winding for excitation, the grid-side converter is a three-phase rectifier, which is used to feed the grid's fixed-frequency AC energy to the DC link after rectification; the DC link is sent to the rotor-side converter after completing energy retention and decoupling; wherein, the rotor-side converter is an inverter, which is used to send the DC side energy to the rotor winding through three-phase inverter technology.

9. The design method of a high inertia double-fed phase condenser system according to claim 6, characterized in that: The steel flywheel is connected to the doubly-fed generator through a coupling; wherein the doubly-fed generator is placed horizontally, the steel flywheel is in the shape of a flat disc, and the diameter of the steel flywheel is greater than the diameter of the stator winding.

10. The design method of a high inertia double-fed phase condenser system according to claim 6, characterized in that: The rotor winding of the double-fed motor adopts AC excitation to achieve variable speed constant frequency.

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