Modular hybrid transformer voltage regulation method, system, device, and medium

Abstract

The application discloses a modular hybrid transformer voltage regulation method, system, device and medium, and relates to the technical field of power electronics. The method comprises the following steps: acquiring a line voltage at a system grid connection point containing a modular hybrid transformer; acquiring fan side power fluctuation data according to the line voltage at the system grid connection point; calculating an upper limit of fan side reactive power output according to the fan side power fluctuation data; judging whether a feasible solution exists for an optimal compensation voltage calculation model, if the first judgment result is yes, the feasible solution is used as a compensation voltage instruction value, if the first judgment result is no, a compensation voltage instruction value is calculated by using a same-phase compensation method; and the compensation voltage instruction value is input into a converter module in the modular hybrid transformer to complete voltage regulation. The application can solve the problem of grid connection point voltage fluctuation and relieve the problem of fan side reactive power output exceeding the limit.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a modular hybrid transformer voltage regulation method, system, device, and medium. Background Technology

[0002] In recent years, the randomness of the power supply side and the uncertainty of the load side after the large-scale wind turbines are connected to the grid have combined to make the problems of high and low voltage exceeding the limit prominent, and the voltage fluctuations are frequent, making the voltage flow regulation of the grid more difficult. Regulations require wind farms to have low voltage ride-through capability, that is, when the voltage at the wind farm's grid connection point drops, the wind turbines do not disconnect from the grid and continue to provide reactive power support for the grid to restore normal operation.

[0003] Existing voltage regulation devices in the power grid, such as on-load tap changers and voltage regulating transformers, have slow regulation speeds and lack continuous voltage regulation capabilities. This may lead to further voltage reductions in other areas due to reactive power deficits, failing to meet the requirements of wind power grid-connected systems for rapid, continuous, and flexible voltage regulation. Solid-state transformers can achieve rapid and flexible adjustment of output voltage, as well as the measurement and reshaping of system impedance. However, in actual transmission networks, there is almost no possibility of power flow reversal, and they are expensive, have poor overload capacity, and low reliability, making them unsuitable for widespread use in wind power grid-connected systems. Unified power flow controllers, while possessing power support capabilities and the ability to directly compensate for voltage and reactive power, rely on series transformers for insulation, resulting in large footprints and excessively high costs.

[0004] Therefore, a device and regulation method are needed to solve the problems of grid connection voltage fluctuations and generator-side reactive power output exceeding limits. Summary of the Invention

[0005] The purpose of this invention is to provide a modular hybrid transformer voltage regulation method, system, equipment, and medium to solve the problem of voltage fluctuation at the grid connection point and alleviate the problem of excessive reactive power output on the generator side.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A modular hybrid transformer voltage regulation method includes:

[0008] Obtain the line voltage at the grid connection point of the system containing the hybrid transformer;

[0009] The power fluctuation data on the wind turbine side is obtained based on the line voltage at the grid connection point of the system.

[0010] Calculate the upper limit of reactive power output on the wind turbine side based on the power fluctuation data on the wind turbine side;

[0011] Determine whether the optimal compensation voltage calculation model has a feasible solution to obtain the first determination result; the feasible solution is obtained by solving the optimal compensation voltage calculation model based on the upper limit of reactive power output on the wind turbine side, the power fluctuation data on the wind turbine side, and the voltage fluctuation data at the system grid connection point.

[0012] If the first judgment result is yes, then the feasible solution is used as the compensation voltage command value;

[0013] If the first judgment result is negative, the compensation voltage command value is calculated using the same phase compensation method;

[0014] The compensation voltage command value is input into the converter module of the modular hybrid transformer to complete the voltage regulation.

[0015] Optionally, the power fluctuation data on the wind turbine side is obtained based on the line voltage at the grid connection point of the system, specifically including:

[0016] Determine whether voltage fluctuations occur at the grid connection point of the system, and obtain a second determination result;

[0017] If the second judgment result is yes, then obtain the power fluctuation data on the wind turbine side;

[0018] If the second judgment result is negative, then the voltage regulation ends.

[0019] Optionally, the expression for the reactive power output on the wind turbine side is:

[0020]

[0021] Among them, Q g For reactive power output on the wind turbine side, V sag For the line voltage after the drop, I L For line current, The power factor angle on the wind turbine side after the fall.

[0022] Optionally, the expression for the optimal compensation voltage calculation model is:

[0023] min|V m |

[0024]

[0025] Among them, V m For the MMC-HT compensation voltage amplitude, V L V is the line voltage before the voltage drop. sag The line voltage after the voltage drop, Δθ sag β is the voltage drop angle of the line, β is the phase angle of the MMC-HT compensation voltage, and S is the voltage drop angle of the line. mmc_max For converter capacity, Q g maxQ represents the upper limit of the reactive power output of the wind turbine. g min This represents the lower limit of reactive power output of the wind turbine.

[0026] The present invention also provides a modular hybrid transformer voltage regulation system, comprising:

[0027] The grid connection point line voltage acquisition module is used to acquire the line voltage at the grid connection point of a system containing a hybrid transformer;

[0028] The wind turbine-side power fluctuation data acquisition module is used to acquire wind turbine-side power fluctuation data based on the line voltage at the grid connection point of the system.

[0029] The calculation module is used to calculate the upper limit of reactive power output on the wind turbine side based on the power fluctuation data on the wind turbine side;

[0030] The first judgment module is used to determine whether there is a feasible solution to the optimal compensation voltage calculation model and obtain the first judgment result; the feasible solution is obtained by solving the optimal compensation voltage calculation model based on the upper limit of reactive power output on the wind turbine side, the power fluctuation data on the wind turbine side, and the voltage fluctuation data at the system grid connection point.

[0031] The first compensation voltage determination module is used to determine the feasible solution as the compensation voltage command value if the first determination result is yes.

[0032] The second compensation voltage determination module is used to calculate the compensation voltage command value using the same-phase compensation method if the first determination result is negative.

[0033] The voltage regulation module is used to input the compensation voltage command value into the converter module of the modular hybrid transformer to complete the voltage regulation.

[0034] Optionally, the wind turbine-side power fluctuation data acquisition module specifically includes:

[0035] The second judgment unit is used to determine whether voltage fluctuation occurs at the grid connection point of the system, and to obtain a second judgment result.

[0036] The acquisition unit is used to acquire power fluctuation data on the wind turbine side if the second judgment result is yes;

[0037] The termination unit is used to terminate voltage regulation if the second determination result is negative.

[0038] Optionally, the expression for the reactive power output on the wind turbine side is:

[0039]

[0040] Among them, Q g For reactive power output on the wind turbine side, V sag For the line voltage after the drop, IL For line current, The power factor angle on the wind turbine side after the fall.

[0041] Optionally, the expression for the optimal compensation voltage calculation model is:

[0042] min|V m |

[0043]

[0044] Among them, V m For the MMC-HT compensation voltage amplitude, V L V is the line voltage before the voltage drop. sag The line voltage after the voltage drop, Δθ sag β is the voltage drop angle of the line, β is the phase angle of the MMC-HT compensation voltage, and S is the voltage drop angle of the line. mmc_max For converter capacity, Q g max Q represents the upper limit of the reactive power output of the wind turbine. g min This represents the lower limit of reactive power output of the wind turbine.

[0045] The present invention also provides an electronic device, comprising:

[0046] One or more processors;

[0047] A storage device on which one or more programs are stored;

[0048] When the one or more programs are executed by the one or more processors, the one or more processors cause the one or more processors to perform the method as described.

[0049] The present invention also provides a computer storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the method as described.

[0050] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0051] This invention obtains the line voltage at the grid connection point of a system containing a modular hybrid transformer; obtains power fluctuation data on the wind turbine side based on the line voltage at the grid connection point; calculates the upper limit of reactive power output on the wind turbine side based on the power fluctuation; determines whether the optimal compensation voltage calculation model has a feasible solution, and obtains a first judgment result; the feasible solution is obtained by solving the optimal compensation voltage calculation model based on the upper limit of reactive power output on the wind turbine side, the power fluctuation data on the wind turbine side, and the voltage fluctuation data at the grid connection point; if yes, the feasible solution is used as the compensation voltage command value; if not, the compensation voltage command value is calculated using the in-phase compensation method; the compensation voltage command value is input into the converter module of the modular hybrid transformer to complete the voltage regulation function. By inputting the optimal compensation voltage command value into the converter of the modular hybrid transformer, the power flow distribution on the line is adjusted, thereby solving the grid connection point voltage fluctuation problem and alleviating the problem of excessive reactive power output on the turbine side. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0053] Figure 1 This is a structural diagram of a modular hybrid transformer device;

[0054] Figure 2 This is a schematic diagram of a system circuit model containing MMC-HT;

[0055] Figure 3 This is a diagram showing the relationship between electrical quantities.

[0056] Figure 4 Electrical diagram for when a voltage drop occurs on the load side

[0057] Figure 5 Circuit diagram of a wind turbine grid connection system;

[0058] Figure 6 The waveform diagrams of the compensation voltage on the load side before and after the compensation and the MMC-HT compensation voltage are shown.

[0059] Figure 7 Figures showing the reactive power output of the fan side under different voltage regulation methods;

[0060] Figure 8 Flowchart of a modular hybrid transformer voltage regulation method;

[0061] Figure 9 This is a schematic diagram illustrating the practical application of a modular hybrid transformer voltage regulation method. Detailed Implementation

[0062] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0063] The purpose of this invention is to provide a modular hybrid transformer voltage regulation method, system, equipment, and medium to solve the problem of voltage fluctuation at the grid connection point and alleviate the problem of excessive reactive power output on the generator side.

[0064] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0065] like Figure 8 and Figure 9 As shown, the present invention provides a modular hybrid transformer voltage regulation method, which is applied to, for example... Figure 1 The diagram shows a modular hybrid transformer device (MMC-HT), illustrated using a single-phase view as an example. The device includes: a passive section: a three-winding transformer; and an active section: a modular multilevel back-to-back voltage source converter.

[0066] In the passive three-winding transformer, the primary winding uses a star connection, while the secondary and auxiliary windings use a Y connection. The secondary winding is used to transmit electrical energy between the two systems, and the tertiary winding serves as an auxiliary winding to achieve energy exchange with the converter.

[0067] In the modular multilevel back-to-back voltage source converter of the active section, the rectifier-side converter, directly connected to the auxiliary winding, draws energy from the AC system to maintain the DC-side voltage and provides the necessary active power to the inverter-side converter. The inverter-side converter is connected in series between the end of the star-connected winding of the main transformer and the neutral point. While maintaining the original transformer grounding point, it can superimpose a voltage vector V∠θ with controllable amplitude and phase on the original winding voltage, allowing the voltage on both sides of the transformer to be quickly and continuously adjusted according to demand. It also reduces the insulation requirements of the converter to a certain extent. The inverter-side converter has the function of full-power four-quadrant operation and has the function of active and reactive power support.

[0068] The present invention provides a modular hybrid transformer voltage regulation method applicable to wind power grid connection scenarios, specifically a voltage regulation method for a hybrid transformer (HT) device based on a modular multilevel converter (MMC) converter, comprising:

[0069] Step 101: Obtain the line voltage at the grid connection point of the system containing the hybrid transformer.

[0070] Step 102: Obtain power fluctuation data on the wind turbine side based on the line voltage at the grid connection point of the system.

[0071] Step 102 specifically includes: determining whether voltage fluctuations occur at the grid connection point of the system, and obtaining a second determination result; if the second determination result is yes, then acquiring power fluctuation data on the wind turbine side; if the second determination result is no, then ending voltage regulation.

[0072] Step 103: Calculate the upper limit of reactive power output on the wind turbine side based on the power fluctuation on the wind turbine side.

[0073] The expression for the reactive power output on the wind turbine side is:

[0074]

[0075] Among them, Q g For reactive power output on the wind turbine side, V sag For the line voltage after the drop, I L For line current, The power factor angle after the fall.

[0076] Step 104: Determine whether the optimal compensation voltage calculation model has a feasible solution to obtain a first determination result; the feasible solution is obtained by solving the optimal compensation voltage calculation model based on the upper limit of reactive power output on the wind turbine side, the power fluctuation data on the wind turbine side, and the voltage fluctuation data at the system grid connection point. If the first determination result is yes, proceed to step 105. If the first determination result is no, proceed to step 106.

[0077] Step 105: The feasible solution is used as the compensation voltage command value.

[0078] Step 106: Calculate the compensation voltage command value using the in-phase compensation method.

[0079] Step 107: Input the compensation voltage command value into the converter module of the modular hybrid transformer to complete the voltage regulation.

[0080] The expression for the optimal compensation voltage calculation model is as follows:

[0081] min|V m |

[0082]

[0083] Among them, V m For the MMC-HT compensation voltage amplitude, V L V is the line voltage before the voltage drop. sag The line voltage after the voltage drop, Δθ sag β is the voltage drop angle of the line, β is the phase angle of the MMC-HT compensation voltage, and S is the voltage drop angle of the line. mmc_max For converter capacity, Q g max Q represents the upper limit of the reactive power output of the wind turbine. g min This represents the lower limit of reactive power output of the wind turbine.

[0084] The process of determining the optimal compensation voltage calculation model includes the following steps:

[0085] Step 1: Establish a circuit model based on a modular multilevel hybrid transformer system, and analyze the voltage compensation principle of MMC-HT and its impact on line power flow.

[0086] Based on its structure Figure 1 It can be seen that the principle of voltage regulation by this device is as follows:

[0087]

[0088] This is the voltage at the transformer's output side. This is the voltage at the primary winding port. N1 represents the voltage at the secondary winding port, N2 represents the number of turns in the primary and secondary windings, respectively, and k1 represents the transformer turns ratio. This is the compensation voltage for MMC-HT.

[0089] To analyze its power flow characteristics in the system, a system circuit model containing MMC-HT is established as follows: Figure 2 Electrical quantity relationships are as follows Figure 3 The main function of this device is to inject a controllable voltage vector V into the line. m ∠θ is used to compensate for line voltage and regulate line power flow. When voltage fluctuations occur at the load-side nodes, the MMC-HT compensation amount and the electrical relationship between the line node voltages are as follows: Figure 4 The injected voltage can be regarded as a voltage source synchronized with the AC base frequency. When the current on the line passes through this voltage source, it exchanges power with the power grid. Among them, the common power is provided by the power source, and the reactive power is provided by the rectifier side itself.

[0090] Based on the MMC-HT structure and voltage regulation principle, the voltage relationship can be expressed as follows:

[0091]

[0092] Load-side voltage, Here, is the voltage on the power supply side, and j is a complex unit. The flow through the line can be represented as:

[0093]

[0094] X is the grid voltage. r This is the load-side reactance.

[0095] Active power P output from the power supply side g Reactive power Q g It can be represented as:

[0096]

[0097] This is the power factor angle on the power supply side.

[0098] From the above expression, it can be seen that in a constant load system, when the voltage compensation value V m When θ changes, the power distribution relationship between the power supply side and the MMC-HT also changes. Therefore, when performing compensation, it is necessary to consider the system circuit parameters, especially the power supply side power capacity, to select an appropriate voltage compensation value V. m , θ.

[0099] Step 2: Taking into account the reactive power capacity of the wind turbine units and the capacity of the converter itself in the system, establish an optimal compensation voltage calculation model to obtain the amplitude and phase angle of the optimal compensation voltage for the MMC-HT. The model is established as follows:

[0100] GB / T 19963-2011, "Technical Regulations for Wind Farm Connection to Power Systems," requires that the reactive power source of a wind farm includes wind turbine generators and reactive power compensation devices. The inherent reactive power regulation capacity of the wind turbine generators should be fully utilized. When their reactive power capacity cannot meet the needs of grid voltage regulation, reactive power compensation devices should be installed. Therefore, to ensure the reliable operation of the wind farm and meet the requirements for the safe and stable operation of the wind farm's substation, the reactive power regulation capacity and capability of the generator units themselves should be fully utilized first. Demands beyond this capacity can be provided by hybrid transformers with reactive power compensation functions. Therefore, when designing the MMC-HT capacity configuration and compensation scheme, the reactive power capacity of the wind turbine generators must first be obtained.

[0101] Taking a doubly-fed induction generator (DFIG) as an example, assuming the maximum current of the rotor-side converter is I... rmax The upper and lower limits of the reactive power output on the stator side can be obtained as follows:

[0102]

[0103] Among them, u s X is the voltage at the fan port. s For stator reactance, X m For the magnetizing reactance, I rmax P is the maximum allowable current of the rotor-side converter. s This is the active power output on the stator side.

[0104] The operating range of reactive power of the grid-side converter of a doubly-fed induction generator (DFIG) is mainly limited by its own capacity. Therefore, the upper and lower limits of the reactive power output on the rotor side are:

[0105]

[0106] S cmax For the capacity of the grid-side converter, P c It outputs reactive power to the grid-side converter.

[0107] The reactive power provided by the static var compensator with capacitance C in the wind farm The upper and lower limits of the reactive power delivered by the doubly-fed induction generator (DFIG) to the grid are as follows:

[0108]

[0109] According to equation (4), when the voltage drops, the reactive power generated by the wind turbine is:

[0110]

[0111] V sag This refers to the line voltage after the voltage drop. I is the power factor angle on the wind turbine side after the drop. L The line current is where,

[0112]

[0113] To compensate for the power factor angle on the load side, Δθ sag β is the voltage drop angle of the line, and β is the phase angle of the MMC-HT compensation voltage.

[0114] The upper and lower limits of reactive power output on the wind turbine side are:

[0115] Q g min ≤Q g ≤Q g max (10)

[0116] Combining equations (8) and (9), the limitation of the reactive power capacity of the wind turbine side on the MMC-HT compensation voltage angle can be expressed as:

[0117]

[0118] The relationship between the converter's output power and its output voltage is expressed as follows:

[0119]

[0120] For I L The conjugate form of S mmc S represents the converter output power. mmc_max For the converter capacity, we have:

[0121]

[0122] Right now:

[0123]

[0124] According to the Law of Cosines, we can obtain:

[0125]

[0126] V L This is the line voltage before the voltage drop.

[0127] The limitation of converter body capacity on compensation angle can be expressed as:

[0128]

[0129] In summary, the optimal compensation voltage calculation model that takes into account both the wind farm and the regulation capability of the MMC-HT can be established as follows:

[0130] min|V m |

[0131]

[0132] When a voltage drop occurs on the load side, the optimal voltage compensation amplitude and phase angle can be obtained by acquiring the required state variables in the system using the above formula. Considering that when the voltage drop is too large and exceeds the adjustment range of the MMC-HT, since the in-phase compensation method can compensate for the voltage amplitude to the maximum extent within its capacity range, in order to raise the load side voltage as much as possible, the in-phase compensation method should be used for adjustment at this time. That is, the voltage phase angle of the current line is directly selected as the compensation voltage angle of the MMC-HT, and the difference between the initial voltage and the voltage drop amplitude is selected as the compensation voltage amplitude of the MMC-HT.

[0133] Step 3: Verify the proposed MMC-HT optimal voltage compensation scheme in the wind power grid-connected system simulation model and its ability to alleviate the problem of reactive power output exceeding the limit on the turbine side, and improve the voltage stability at the grid connection point.

[0134] The structure of the MMC-HT wind power grid connection system is as follows: Figure 5As shown, the doubly-fed induction generator (DFIG) wind turbine generator set consists of six 4*1.5MW wind turbines. It is connected to node 4 of the IEEE standard three-machine nine-node power grid via a 0.69 / 35kV transformer, transmission line, and a parallel capacitor reactive power compensator at the turbine terminals, through an MMC-HT transformer with a transformation ratio of 35 / 220 / 20kV. When wind speed changes cause voltage fluctuations at the turbine output port or when a transient fault occurs in the power grid, the MMC-HT utilizes the proposed optimal voltage compensation method to regulate the system voltage and provide reactive power support to maintain grid connection point voltage stability and reduce reactive power output on the turbine side.

[0135] In the simulation model, during normal operation, the wind turbine injects 30MW of active power and 5Mvar of reactive power into the system, and each node maintains its rated voltage. A sudden wind speed change is set at 0.1s, lasting for 0.1s, during which the voltage at the turbine port drops by approximately 10%. At this time, the MMC-HT performs voltage compensation on the line. According to equation (7) and the voltage drop level, the upper limit of the reactive power output of the wind turbine at this time can be calculated to be 4.3Mvar. To allow for a certain margin, the actual reactive power output of the wind turbine is set to not exceed 90% of the upper limit of reactive power output at this time, i.e., 3.82Mvar. According to equation (17), the optimal voltage compensation is 13∠5°kV. Figure 6 (a) and Figure 6 (b) shows the voltage waveforms at the grid connection point before and after compensation, indicating that the compensation function of MMC-HT can effectively maintain the stability of the grid connection point voltage when the voltage output of the wind turbine fluctuates.

[0136] The proposed scheme is compared with the on-load tap-changing transformer scheme and the classic in-phase tap-changing scheme in terms of reactive power output demand on the wind turbine side. The changes in reactive power output on the wind turbine side during system operation under the three different compensation schemes are as follows: Figure 7 As shown in Table 1, the reactive power output on the wind turbine side during the compensation process is as follows.

[0137] Table 1 Reactive power output on the wind turbine side under different compensation schemes

[0138] On-load tap changing transformer voltage regulation 5.58 In-phase voltage regulation 4.85 The method proposed in this invention regulates voltage 3.80

[0139] Figure 7 Table 1 and other data demonstrate that the proposed MMC-HT voltage compensation method effectively solves the problem of wind turbine reactive power exceeding limits during voltage dip compensation, and maintains voltage stability at the grid connection point.

[0140] This invention utilizes a hybrid transformer topology based on modular converters, extending its application beyond traditional low-voltage distribution networks. This effectively increases the voltage level of the device and broadens its application scenarios. Compared to traditional on-load tap-changing transformers, it is more suitable for renewable energy grid-connected systems, effectively solving voltage fluctuation problems at the grid connection point and mitigating reactive power output exceeding limits on the generator side.

[0141] The present invention also provides a modular hybrid transformer voltage regulation system, comprising:

[0142] The grid connection point line voltage acquisition module is used to acquire the line voltage at the grid connection point of a system containing a hybrid transformer.

[0143] The wind turbine-side power fluctuation data acquisition module is used to acquire wind turbine-side power fluctuation data based on the line voltage at the grid connection point of the system.

[0144] The calculation module is used to calculate the upper limit of reactive power output on the wind turbine side based on the power fluctuation data on the wind turbine side.

[0145] The first judgment module is used to determine whether there is a feasible solution to the optimal compensation voltage calculation model and obtain the first judgment result; the feasible solution is obtained by solving the optimal compensation voltage calculation model based on the upper limit of reactive power output on the wind turbine side, the power fluctuation data on the wind turbine side, and the voltage fluctuation data at the system grid connection point.

[0146] The first compensation voltage determination module is used to determine the feasible solution as the compensation voltage command value if the first determination result is yes.

[0147] The second compensation voltage determination module is used to calculate the compensation voltage command value using the in-phase compensation method if the first determination result is negative.

[0148] The voltage regulation module is used to input the compensation voltage command value into the converter module of the modular hybrid transformer to complete the voltage regulation.

[0149] As an optional implementation, the wind turbine-side power fluctuation data acquisition module specifically includes:

[0150] The second judgment unit is used to determine whether voltage fluctuations occur at the grid connection point of the system, and to obtain a second judgment result.

[0151] The acquisition unit is used to acquire power fluctuation data on the wind turbine side if the second judgment result is yes.

[0152] The termination unit is used to terminate voltage regulation if the second determination result is negative.

[0153] As an optional implementation, the expression for the reactive power output on the wind turbine side is:

[0154]

[0155] Among them, Q g For reactive power output on the wind turbine side, V sag For the line voltage after the drop, I L For line current, The power factor angle on the wind turbine side after the fall.

[0156] As an optional implementation, the expression for the optimal compensation voltage calculation model is:

[0157] min|V m |

[0158]

[0159] Among them, V m For the MMC-HT compensation voltage amplitude, V L V is the line voltage before the voltage drop. sag The line voltage after the voltage drop, Δθ sag β is the voltage drop angle of the line, β is the phase angle of the MMC-HT compensation voltage, and S is the voltage drop angle of the line. mmc_max For converter capacity, Q g max Q represents the upper limit of the reactive power output of the wind turbine. g min This represents the lower limit of reactive power output of the wind turbine.

[0160] The present invention also provides an electronic device, comprising: one or more processors; a storage device having one or more programs stored thereon; wherein, when the one or more programs are executed by the one or more processors, the one or more processors perform the method as described.

[0161] The present invention also provides a computer storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the method as described.

[0162] When the grid connection voltage fluctuates or drops due to faults, wind power systems are required to have a fast and accurate dynamic response. Hybrid Transformer (HT) combines the high overload capacity of electromagnetic transformers with the flexible and rapid adjustment of power electronic equipment. It can perform smooth voltage regulation and has advantages such as rapid response, low mechanical loss, and low cost. Combined with modular multilevel converter topology and its control strategy, it can effectively improve the application voltage level of the device. Designing the optimal compensation voltage method for this device in the system can effectively alleviate the problem of reactive power output exceeding the limit on the turbine side. Integrating a hybrid transformer into the wind power grid connection system to replace the on-load tap changer can effectively, quickly, and accurately address voltage quality problems caused by grid connection voltage fluctuations and effectively improve the voltage stability of the grid connection point.

[0163] This invention relates to a voltage regulation method that uses a hybrid transformer to output optimal compensation voltage to the power flow distribution on the line, based on the actual state of the wind power system and taking into account the reactive power capacity of the wind turbine and the capacity of the converter itself. This method can alleviate the problem of reactive power output exceeding the limit on the turbine side. The compensation function of this device was realized by establishing a system power flow model containing the hybrid transformer and an independent dual-loop control system for the rectifier and inverter converters. System-level simulation verification of wind power grid connection shows that the hybrid transformer can significantly improve the low voltage ride-through capability of wind turbines and the voltage stability at the grid connection point in wind power grid connection.

[0164] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0165] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A modular hybrid transformer voltage regulation method, characterized in that, include: Obtain the line voltage at the grid connection point of the system containing the hybrid transformer; The power fluctuation data on the wind turbine side is obtained based on the line voltage at the grid connection point of the system. Calculate the upper limit of reactive power output on the wind turbine side based on the power fluctuation data on the wind turbine side; The first judgment result is obtained by determining whether the optimal compensation voltage calculation model has a feasible solution; the feasible solution is obtained by solving the optimal compensation voltage calculation model based on the upper limit of reactive power output on the wind turbine side, the power fluctuation data on the wind turbine side, and the voltage fluctuation data at the system grid connection point; the expression of the optimal compensation voltage calculation model is: in, For MMC-HT compensation voltage amplitude, This refers to the line voltage before the voltage drop. This refers to the line voltage after the voltage drop. This refers to the voltage drop angle of the line. For MMC-HT compensation voltage phase angle, For converter capacity, This represents the upper limit of the reactive power output of the wind turbine. The lower limit of reactive power output of the wind turbine. For line current, The power factor angle on the wind turbine side after the drop; If the first judgment result is yes, then the feasible solution is used as the compensation voltage command value; If the first judgment result is negative, the compensation voltage command value is calculated using the same phase compensation method; The compensation voltage command value is input into the converter module of the modular hybrid transformer to complete the voltage regulation.

2. The modular hybrid transformer voltage regulation method according to claim 1, characterized in that, The power fluctuation data on the wind turbine side is obtained based on the line voltage at the grid connection point of the system, specifically including: Determine whether voltage fluctuations occur at the grid connection point of the system, and obtain a second determination result; If the second judgment result is yes, then obtain the power fluctuation data on the wind turbine side; If the second judgment result is negative, then the voltage regulation ends.

3. The modular hybrid transformer voltage regulation method according to claim 1, characterized in that, The expression for the reactive power output on the wind turbine side is: in, For reactive power output on the wind turbine side, This refers to the line voltage after the voltage drop. For line current, The power factor angle on the wind turbine side after the fall.

4. A modular hybrid transformer voltage regulation system, characterized in that, include: The grid connection point line voltage acquisition module is used to acquire the line voltage at the grid connection point of a system containing a hybrid transformer; The wind turbine-side power fluctuation data acquisition module is used to acquire wind turbine-side power fluctuation data based on the line voltage at the grid connection point of the system. The calculation module is used to calculate the upper limit of reactive power output on the wind turbine side based on the power fluctuation data on the wind turbine side; The first judgment module is used to determine whether the optimal compensation voltage calculation model has a feasible solution and obtain a first judgment result; the feasible solution is obtained by solving the optimal compensation voltage calculation model based on the upper limit of reactive power output on the wind turbine side, the power fluctuation data on the wind turbine side, and the voltage fluctuation data at the system grid connection point; the expression of the optimal compensation voltage calculation model is: in, For MMC-HT compensation voltage amplitude, This refers to the line voltage before the voltage drop. This refers to the line voltage after the voltage drop. This refers to the voltage drop angle of the line. For MMC-HT compensation voltage phase angle, For converter capacity, This represents the upper limit of the reactive power output of the wind turbine. The lower limit of reactive power output of the wind turbine. For line current, The power factor angle on the wind turbine side after the drop; The first compensation voltage determination module is used to determine the feasible solution as the compensation voltage command value if the first determination result is yes. The second compensation voltage determination module is used to calculate the compensation voltage command value using the same-phase compensation method if the first determination result is negative. The voltage regulation module is used to input the compensation voltage command value into the converter module of the modular hybrid transformer to complete the voltage regulation.

5. The modular hybrid transformer voltage regulation system according to claim 4, characterized in that, The wind turbine-side power fluctuation data acquisition module specifically includes: The second judgment unit is used to determine whether voltage fluctuation occurs at the grid connection point of the system, and to obtain a second judgment result. The acquisition unit is used to acquire power fluctuation data on the wind turbine side if the second judgment result is yes; The termination unit is used to terminate voltage regulation if the second determination result is negative.

6. The modular hybrid transformer voltage regulation system according to claim 4, characterized in that, The expression for the reactive power output on the wind turbine side is: in, For reactive power output on the wind turbine side, This refers to the line voltage after the voltage drop. For line current, The power factor angle on the wind turbine side after the fall.

7. An electronic device, characterized in that, include: One or more processors; A storage device on which one or more programs are stored; When the one or more programs are executed by the one or more processors, the one or more processors cause the one or more processors to implement the method as described in any one of claims 1 to 3.

8. A computer storage medium, characterized in that, It stores a computer program thereon, wherein the computer program, when executed by a processor, implements the method as described in any one of claims 1 to 3.

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