Current balancing method, double-fed converter, wind power generation system and medium

Abstract

The invention discloses a current balancing method, a double-fed converter, a wind power generation system and a medium, and relates to the technical field of converters. And obtaining the voltage difference of the reactor of the doubly-fed converter so as to be counteracted by the voltage of the reactor. The historical voltage compensation value of each phase is determined through the voltage difference value between the modules of each phase and the historical direct current bus voltage value, and accurate voltage control of the converter is achieved. And determining a first gain coefficient of each phase according to the historical voltage compensation value of each phase and the current difference value between the modules of each phase, substituting the final unified gain coefficient and the current phase current value acquired in real time into an output voltage compensation formula, and outputting the current phase voltage compensation value corresponding to the current converter module, thereby realizing voltage compensation and simultaneously realizing the current phase voltage compensation. The current value difference between the doubly-fed converter modules is reduced to a certain extent, the difference between the modules can be actively detected and compensated, and the circulating current is greatly inhibited.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of current transformer, in particular to a current balancing method, a double-fed current transformer, a wind power generation system and a medium. BACKGROUND

[0002] It has become an inevitable technical path to realize system expansion by connecting multiple power modules in parallel to build a larger capacity current transformer system. The machine-side current transformer outputs larger current through parallel connection to drive the motor. Due to the factors such as parameter dispersion of components in each parallel branch, layout asymmetry, and control signal delay difference, the current distribution among the modules is not balanced, which further causes circulating current, local overload and other problems, directly affecting the reliability and operating efficiency of the system.

[0003] Therefore, how to reduce the current difference between the modules and suppress the circulating current in the system to achieve balanced distribution is an urgent problem for those skilled in the art to solve. SUMMARY

[0004] The purpose of the present application is to provide a current balancing method, a double-fed current transformer, a wind power generation system and a medium to solve the problem of poor distribution balance of current among the modules, which further causes circulating current, local overload and other problems, directly affecting the reliability and operating efficiency of the system.

[0005] To solve the above technical problems, the present application provides a current balancing method for a double-fed current transformer module, comprising:

[0006] Obtaining the inter-module current difference of each phase obtained by the historical current value of each phase of the double-fed current transformer module, to determine the inter-module voltage difference of each phase;

[0007] Determine the historical voltage compensation value of each phase based on the inter-module voltage difference of each phase and the historical DC bus voltage value; and determine the first gain coefficient of each phase based on the historical voltage compensation value of each phase and the inter-module current difference of each phase, to determine the final gain coefficient;

[0008] Determine the current phase voltage compensation value corresponding to the current current transformer module according to the final gain coefficient and the current phase current value of the double-fed current transformer module, to add to the control end of the double-fed current transformer to realize current balancing.

[0009] On the one hand, the determination process of the current phase voltage compensation value corresponding to the current current transformer module comprises:

[0010] Obtaining the current dead zone value of the double-fed current transformer module;

[0011] Taking the first current transformer module of the double-fed current transformer module as the current current transformer module, and taking the second current transformer module as another current transformer module;

[0012] The current phase current value of the current converter module is averaged with the current phase current value of another converter module to obtain a first average current value;

[0013] The first average current value is added to the current dead zone value to obtain a first current value;

[0014] The current phase current value of the current converter module is subtracted from the first current value to obtain a second current value;

[0015] The second current value is multiplied by the final gain coefficient to obtain the current phase voltage compensation value corresponding to the current converter module.

[0016] On the other hand, the historical voltage compensation value of each phase is determined based on the inter-module voltage difference of each phase and the historical DC bus voltage value, including:

[0017] The effective value of the phase voltage corresponding to each phase is determined according to the inter-module voltage difference of each phase;

[0018] The maximum value of the line voltage corresponding to each phase is determined according to the effective value of the phase voltage of each phase;

[0019] The historical voltage compensation value of each phase is determined according to the maximum value of the line voltage of each phase and the historical DC bus voltage value.

[0020] On the other hand, the first gain coefficient of each phase is determined according to the historical voltage compensation value of each phase and the inter-module current difference of each phase, including:

[0021] Half of the inter-module current difference of each phase is taken as the first current difference;

[0022] The historical voltage compensation value of each phase is divided by the first current difference to obtain the corresponding first gain coefficient.

[0023] On the other hand, the determination process of the final gain coefficient includes:

[0024] The first gain coefficient of each phase is averaged to obtain the final gain coefficient;

[0025] Or, the maximum first gain coefficient or the minimum first gain coefficient is selected from the first gain coefficient of each phase as the final gain coefficient;

[0026] Or, if the inter-module current difference corresponding to each phase in each phase first gain coefficient is less than the preset current difference, the maximum first gain coefficient in each phase first gain coefficient is selected as the final gain coefficient; if the inter-module current difference corresponding to each phase in each phase first gain coefficient is not less than the preset current difference, the target first gain coefficient corresponding to the inter-module current difference less than the preset current difference is selected from each phase first gain coefficient, and the maximum target first gain coefficient is selected from each target first gain coefficient as the final gain coefficient.

[0027] On the other hand, after determining the final gain coefficient, further comprising:

[0028] Obtaining the first threshold value corresponding to the inter-module current difference of each phase of the double-fed converter module;

[0029] Determining the critical gain coefficient according to the historical voltage compensation value and the first threshold value;

[0030] If the final gain coefficient is greater than the critical gain coefficient, returning to the step of obtaining the inter-module current difference of each phase from the historical current value of each phase of the double-fed converter module;

[0031] If the final gain coefficient is less than or equal to the critical gain coefficient, entering the step of determining the current phase voltage compensation value corresponding to the current converter module according to the final gain coefficient and the current phase current value of the double-fed converter module.

[0032] On the other hand, the determination process of the inter-module voltage difference of each phase comprises:

[0033] Obtaining the reactance inductance of the double-fed converter module and the angular frequency;

[0034] Multiplying the inter-module current difference of each phase, the angular frequency and the reactance inductance to obtain the inter-module voltage difference of each phase.

[0035] To solve the above technical problems, the application also provides a double-fed converter, comprising a first machine-side converter and a second machine-side converter;

[0036] The control end of the first machine-side converter is connected with a first reactor, a controller and a double-fed induction generator; the control end of the second machine-side converter is connected with a second reactor, the controller and the double-fed induction generator; wherein the controller is used to execute the steps of the current balancing method of the double-fed converter module to reduce the current difference between the double-fed converter modules;

[0037] The first end and the second end of each of the first machine-side converter and the second machine-side converter are connected to the two ends of a DC bus capacitor;

[0038] The two ends of the direct current bus capacitor are connected with the first end and the second end of the grid-side converter; the control end of the grid-side converter is connected with the first end of the third reactor; the second end of the third reactor is connected with the first end of the first switch and the first end of the first resistor; the second end of the first switch is connected with the first end of the first circuit breaker; the second end of the first resistor is connected with the first end of the second switch; the second end of the second switch and the second end of the first circuit breaker are both connected with the first end of the second circuit breaker; the second end of the second circuit breaker is connected with the first end of the step-up transformer;

[0039] The double-fed induction generator is connected with the first end of the third switch; the second end of the third switch is connected with the first end of the third circuit breaker; the second end of the third circuit breaker is connected with the second end of the step-up transformer;

[0040] The third end of the step-up transformer is connected with the first end of the fourth circuit breaker; the second end of the fourth circuit breaker is connected with the external power grid.

[0041] To solve the above technical problems, the application further provides a wind power generation system, comprising:

[0042] a memory for storing a computer program;

[0043] a processor for executing the computer program to realize the steps of the current equalization method of the double-fed converter module.

[0044] To solve the above technical problems, the application further provides a computer readable storage medium, wherein the computer readable storage medium stores a computer program, and the computer program is executed by a processor to realize the steps of the current equalization method of the double-fed converter module.

[0045] The application provides a current equalization method of a double-fed converter module. Firstly, the inter-module current difference of each phase is obtained by the historical current value of each phase of the double-fed converter module, so as to determine the inter-module voltage difference of each phase. The essence is to obtain the voltage difference of the reactor of the double-fed converter, so as to be offset by the voltage of the reactor. Secondly, the historical voltage compensation value of each phase is determined based on the inter-module voltage difference of each phase and the historical DC bus voltage value. In order to compensate the voltage difference applied to the two reactors, the output voltage needs to be compensated. Therefore, the historical voltage compensation value of each phase is determined based on the inter-module voltage difference of each phase and the historical DC bus voltage value, so as to realize accurate control voltage of the converter. Thirdly, the first gain coefficient of each phase is determined according to the historical voltage compensation value of each phase and the inter-module current difference of each phase. The historical voltage compensation value itself reflects the voltage output margin of the converter, and the corresponding gain coefficient can dynamically adjust the compensation granularity according to the voltage output margin, so as to avoid insufficient compensation or excessive oscillation. Then, the final unified gain coefficient is determined by the first gain coefficient of each phase. The first gain coefficients of the inter-modules of different phases are different, and the parameters of each phase need to be called separately, which may cause control confusion. In the application, the unified gain coefficient makes the control logic simple and avoids phase imbalance, thereby improving the stability of the system as a whole. Finally, the final unified gain coefficient and the current phase current value collected in real time are substituted into the output voltage compensation formula, and the current phase voltage compensation value corresponding to the current converter module is output, so as to realize voltage compensation and reduce the current value difference between the double-fed converter modules to a certain extent. The difference between the modules can be actively detected and compensated, and the (especially zero sequence) circulating current is greatly inhibited. Since the additional loss caused by the circulating current is eliminated, and each module works near the optimal efficiency point, the average operating efficiency of the system in a wide power range is effectively improved. Overall, the compensation calculation by software reduces the requirement for component tolerance and the cost of components.

[0046] In addition, the application also provides a double-fed converter, a wind power generation system and a computer readable storage medium, which have the same beneficial effects as the current equalization method of the double-fed converter module described above. BRIEF DESCRIPTION OF DRAWINGS

[0047] In order to more clearly illustrate the embodiments of the application, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creating labor.

[0048] Figure 1 A flowchart of the current equalization method of the double-fed converter module provided in the embodiments of the application;

[0049] Figure 2A schematic diagram of a double-mode double-fed current converter control strategy provided for an embodiment of the present application;

[0050] Figure 3 A power cycle platform topology provided for an embodiment of the present application;

[0051] Figure 4 A schematic diagram of phase current values of a K=0 opportunity side module provided for an embodiment of the present application;

[0052] Figure 5 A schematic diagram of phase current values of a K=0.00003 opportunity side module provided for an embodiment of the present application;

[0053] Figure 6 A schematic diagram of phase current values of a K=0.00004 opportunity side module provided for an embodiment of the present application;

[0054] Figure 7 A schematic diagram of phase current values of a K=0.00006 opportunity side module provided for an embodiment of the present application;

[0055] Figure 8 A schematic diagram of phase current values of a K=0.00008 opportunity side module provided for an embodiment of the present application;

[0056] Figure 9 A structural schematic diagram of a double-fed current converter provided for an embodiment of the present application;

[0057] Figure 10 A structural diagram of a current equalization device of a double-fed current converter module provided for an embodiment of the present application;

[0058] Figure 11 A structural diagram of a wind power generation system provided for an embodiment of the present application. DETAILED DESCRIPTION

[0059] The technical solutions in the embodiments of the present application will be described clearly and completely below with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0060] The core of the present application is to provide a current equalization method, a double-fed current converter, a wind power generation system and a medium, to solve the problem of poor distribution balance of current among modules, which further causes circulating current, local overload and other problems, and directly affects the reliability and operation efficiency of the system.

[0061] In order to make the person in this technical field better understand the scheme of the present application, the present application is further described in detail below in combination with the drawings and specific embodiments.

[0062] With the transformation of global energy structure towards clean and low-carbon, wind power as the main force of renewable energy is rapidly developing towards large-scale and high-efficiency. Under this background, the single capacity of doubly-fed induction generator (DFIG) continues to rise in order to capture more wind energy and reduce the cost of electricity. However, the significant increase of wind turbine capacity poses unprecedented challenges to the power level and operation reliability of the core electric energy conversion unit - converter.

[0063] Limited by the single capacity and heat dissipation capability of current mainstream power semiconductor devices (such as insulated gate bipolar transistor (IGBT)), the traditional converter topology using a single power module has reached its physical limit in power level, making it difficult to meet the power transmission demand of megawatt-level and above wind power systems. Therefore, by connecting multiple power modules in parallel to build a larger capacity variable system, it has become an inevitable technical path to realize system expansion. In doubly-fed wind power systems, energy is mainly fed into the grid through the stator side, while the power transmitted through the rotor side is about 25%-30% of the total capacity of the system, so the expansion of the grid-side converter is usually not needed. However, with the increase of unit capacity, the rotor excitation current increases significantly, and the machine-side converter becomes the bottleneck of system power transmission, which must be expanded in parallel. However, in actual engineering, it faces serious current sharing challenges. Due to the dispersion of device parameters, layout asymmetry and control signal delay differences in each parallel branch, it is difficult to achieve natural balanced distribution of current among modules, which further leads to circulating current, local overload and other problems, directly affecting the reliability and operation efficiency of the system.

[0064] Due to manufacturing tolerances, material property dispersion, and installation processes, the parasitic parameters (mainly resistance and inductance) of filter reactors, connection busbars, cables, and other elements in each parallel branch inevitably differ. In addition, the slight asymmetry of printed circuit board (PCB) layout and the dispersion of IGBT switching characteristics lead to impedance mismatch of current loops among modules. This inherent impedance asymmetry directly leads to inconsistent current flowing through each module in both transient and steady states, resulting in harmful circulating current within the system.

[0065] If the current difference between modules is large, a series of negative effects will be triggered: first, uneven current distribution means that some modules will be running long-term overload, bearing more than the design margin of the electrical stress and thermal stress, leading to the junction temperature rise, significantly accelerating the device aging, and even causing permanent thermal damage due to local overheating. Second, the existence of circulating current itself does not do useful work, but it will generate additional conduction and switching loss inside the system, reducing the overall operating efficiency. More seriously, this uneven working condition will significantly increase the system failure rate, threatening the safety and reliability of the entire power generation system, and increasing the operating cost of the whole life cycle due to potential frequent maintenance.

[0066] In actual engineering applications, due to the discreteness of reactor parameters in parallel branches, PCB layout differences, and inconsistent manufacturing processes, the impedance of the current loop between modules is difficult to be completely symmetrical. This impedance difference will lead to uneven current distribution between modules, and then trigger internal circulating current in the system.

[0067] If this uneven current phenomenon is not effectively suppressed, it will significantly increase the current stress and thermal stress of power devices, not only affecting the overall operating efficiency of the system, but also possibly causing local overheating due to long-term overload of some modules, accelerating device aging and even causing thermal damage. In addition, uneven current distribution will also cause electrical stress concentration, increase the risk of module failure, and seriously threaten the reliability and service life of the converter system.

[0068] To solve the "circulating current" and "uneven load" problems caused by parameter differences, different aging levels, uneven heat dissipation, etc. in the parallel operation of multiple converter power modules in large-capacity doubly-fed wind power generation systems (usually above megawatt level), so as to improve the reliability, efficiency and power density of the entire power generation system.

[0069] Static uneven current: Even in a stable power generation state, the output current of each power module will be inconsistent due to the existence of small tolerances in the parameters of its components (such as IGBT turn-on voltage drop and filter inductance value). Long-term operation will cause some modules to be long-term overloaded, accelerating aging.

[0070] Dynamic uneven current: During dynamic processes such as wind speed changes and grid voltage fluctuations, the response speed and control delay of each module will be different, leading to serious uneven distribution of instantaneous current, and even triggering overcurrent protection, threatening system safety.

[0071] Zero-sequence circulating current: This is one of the most difficult problems in multi-module parallel operation. Due to the potential difference between parallel points, internal circulating current that does not flow through the grid load will be generated between modules. This circulating current will: increase the current stress of switching devices and magnetic elements; reduce system efficiency, as energy is wasted in internal circulation; cause current waveform distortion.

[0072] Therefore, the current balancing method of the dual-fed converter module provided in the application can solve the above technical problems.

[0073] Figure 1 A flowchart of the current balancing method of the dual-fed converter module provided in the embodiment of the application is shown in Figure 1 The method comprises the following steps.

[0074] S11: obtaining the inter-module current difference of each phase obtained by the historical current value of each phase of the dual-fed converter module, to determine the inter-module voltage difference of each phase;

[0075] S12: determining the historical voltage compensation value of each phase based on the inter-module voltage difference of each phase and the historical DC bus voltage value, and determining the first gain coefficient of each phase based on the historical voltage compensation value of each phase and the inter-module current difference of each phase, to determine the final gain coefficient;

[0076] S13: determining the current phase voltage compensation value corresponding to the current converter module based on the final gain coefficient and the current phase current value of the dual-fed converter module, to be added to the control end of the dual-fed converter to realize current balancing.

[0077] Specifically, Figure 2 A schematic diagram of the dual-module dual-fed converter control strategy provided in the embodiment of the application is shown in Figure 2 The power outer ring generates a current signal to the current loop, and the current loop generates a voltage signal to generate a modulation wave to the machine-side multi-module converter. Since the voltage modulation signal given to the dual-module converter in the control is the same, considering the difference existing in the hardware loop, the module current will be uneven, and then circulating current is generated. Therefore, in order to suppress the uneven distribution of the module current, compensation needs to be made on the control strategy.

[0078] First, the phase of the power grid is tracked by a phase-locked loop as a synchronous reference for control. Then, the deviation between the target value and the actual value of active power and reactive power is calculated by a proportional-integral (PI) regulator to obtain the corresponding active current target and reactive current target. The deviation between the current target and the actual current is converted into a voltage target by another layer of PI regulator. Then, the feedforward signal of the grid voltage (to offset the influence of grid fluctuation) is superimposed, combined with the phase of the phase-locked loop, and input into a pulse width modulation (PWM) module to generate a driving signal. Finally, the switching device of the converter is controlled to achieve the effect of stable output target power.

[0079] The inter-module current difference of each phase between the two converter modules is determined based on the historical current values of each phase in step S11. The historical current values are collected, and a gain coefficient is obtained based on the historical data to determine the corresponding output voltage compensation value in real time subsequently. The collection period of the historical current values is synchronized for each phase to avoid interference caused by source parameter collection, thereby preventing the accuracy of the output voltage compensation value from being reduced.

[0080] The purpose of determining the inter-module voltage difference of each phase between the two converter modules is to determine the voltage difference based on the collected current values. When the two modules are connected in parallel, if the current is uneven, the voltage drop on the reactor will change with the current. By determining the inter-module voltage difference of each phase, subsequent compensation can be performed to avoid meaningless circulating current between the modules and prevent overloading and burning of a certain module. By calculating the voltage drop on the reactor and the voltage difference between the two modules, the essence is to utilize the voltage drop of the reactor by adjusting the module voltage to ultimately achieve current sharing. The current difference between the modules can be offset by the voltage drop of the reactor, and the current of the two modules becomes more balanced as the voltage drop on the reactor changes with the current.

[0081] In step S12, the historical voltage compensation value of each phase is determined based on the inter-module voltage difference of each phase and the historical DC bus voltage value. The essence is that the voltage difference value accounts for the proportion of the DC bus voltage, which can avoid output distortion caused by excessive compensation amplitude. The first gain coefficient of each phase is determined based on the historical voltage compensation value of each phase and the inter-module current difference of each phase. Regarding the inter-module current difference, half of it is used, which is equivalent to taking the ideal current sharing current (the average of the two module currents) as the reference to directly link the adjustment amplitude of the voltage compensation value and the degree of current imbalance. The larger the current difference, the more appropriate the compensation effort corresponding to the first gain coefficient, which can quickly pull the current back to the balanced state. It is also about correcting the voltage around the middle value of the two module currents.

[0082] In step S12, the final gain coefficient is determined. It should be noted that the gain coefficients of different modules are the same, but the gain coefficients of different phases are different. Therefore, the first gain coefficient of each phase needs to be processed here to match the gain coefficient of each phase and avoid excessive current difference between the two modules. The processing process can be randomly selected, or the maximum value or minimum value can be selected, or the average value can be used. No limitation is made here, and it can be set according to the actual situation.

[0083] In step S13, the current phase voltage compensation value corresponding to the current converter module is determined according to the final gain coefficient and the current phase current value of the double-fed converter module. Here, the voltage compensation formula is called, and the gain coefficient and the current phase current value are substituted into the formula to obtain the current phase voltage compensation value corresponding to the current converter module. In this application, the control coefficient is used to obtain the current phase voltage compensation value corresponding to the current converter module. The control coefficient is used to obtain the current phase voltage compensation value corresponding to the current converter module.

[0084] The current balancing method of the double-fed converter module provided by the embodiment of the application first obtains the inter-module current difference of each phase through the historical current values of each phase of the double-fed converter module, so as to determine the inter-module voltage difference of each phase. The essence is to obtain the voltage difference of the reactor of the double-fed converter so as to be offset by the voltage of the reactor. Secondly, the historical voltage compensation value of each phase is determined based on the inter-module voltage difference of each phase and the historical DC bus voltage value. In order to compensate for the voltage difference applied to the two reactors, the output voltage needs to be compensated. Therefore, the historical voltage compensation value of each phase is determined based on the inter-module voltage difference of each phase and the historical DC bus voltage value, so as to realize precise control voltage of the converter. Thirdly, the first gain coefficient of each phase is determined according to the historical voltage compensation value of each phase and the inter-module current difference of each phase. The historical voltage compensation value itself reflects the voltage output margin of the converter, and the corresponding gain coefficient can dynamically adjust the compensation granularity according to the voltage output margin, so as to avoid insufficient compensation or excessive oscillation. Then, the final unified gain coefficient is determined through the first gain coefficient of each phase. The first gain coefficients of the inter-modules of different phases are different, and the parameters of each phase need to be called separately, which may cause control confusion. In this application, the unified gain coefficient makes the control logic simple and avoids phase imbalance, thereby improving the stability of the system as a whole. Finally, the final unified gain coefficient and the real-time collected current phase current value are substituted into the output voltage compensation formula, and the current phase voltage compensation value corresponding to the current converter module is output, so as to realize voltage compensation and reduce the current value difference between the double-fed converter modules to a certain extent. The difference between the modules can be actively detected and compensated, and the circulating current (especially the zero sequence circulating current) is greatly suppressed. Since the additional loss caused by the circulating current is eliminated, and each module works near the optimal efficiency point, the average operating efficiency of the system in a wide power range is effectively improved. Overall, through the compensation calculation of the software, the requirement for the tolerance of the components is reduced, and the cost of the components is also reduced.

[0085] In some embodiments, the determination process of the inter-module voltage difference of each phase includes:

[0086] The reactor inductance value and the angular frequency of the double-fed converter module are obtained.

[0087] The inter-module voltage difference of each phase is obtained by multiplying the inter-module current difference of each phase, the angular frequency and the reactor inductance value.

[0088] Specifically, the formula is as follows:

[0089] ;

[0090] wherein, is the current difference between the modules of each phase, is the angular frequency, is the inductor inductance.

[0091] Taking the first module of phase A as an example, assuming that the current deviation is 100 A and the inductor inductance is 30 uH, the voltage difference u corresponding to the current deviation at this time is calculated as follows: .

[0092] The voltage difference between the two modules is essentially to actively adjust the module output voltage, so that the voltage drop difference of the inductor offsets the current difference, thereby achieving current sharing.

[0093] The determination process of the voltage difference between the modules of each phase provided in the embodiment is obtained by the voltage drop law of the inductor, and the inherent characteristics that the inductor current change will produce voltage drop are used, without additional complex devices, and the circulating current between the modules can be suppressed only by voltage difference adjustment, which simplifies the hardware design and can accurately balance the current. The voltage drop of the inductor and the current are real-time related, the voltage difference adjustment can quickly respond to the current change (when the current difference appears, the voltage drop difference immediately reflects), and the inductance characteristics of the inductor can also buffer the current fluctuation, avoiding the system from appearing shock, so that the current sharing process is fast and stable.

[0094] In some embodiments, the historical voltage compensation value of each phase is determined based on the voltage difference between the modules of each phase and the historical DC bus voltage value, including:

[0095] determining the corresponding phase voltage effective value according to the voltage difference between the modules of each phase;

[0096] determining the corresponding line voltage maximum value according to the phase voltage effective value of each phase;

[0097] determining the historical voltage compensation value of each phase according to the line voltage maximum value of each phase and the historical DC bus voltage value.

[0098] Specifically, the determination formula of the historical voltage compensation value is as follows:

[0099] ;

[0100] wherein, is the line voltage maximum value, is the historical DC bus voltage value, is the historical voltage compensation value. ​

[0101] In the above formula, the line voltage maximum value needs to be linked with the effective value of the phase voltage, and the voltage difference between the modules is in the form of the phase voltage. In combination with the above example, the corresponding historical voltage compensation value is:

[0102] .

[0103] The determination process of the historical voltage compensation value of each phase provided by the embodiment can avoid output distortion caused by excessively large compensation amplitude (exceeding the upper limit of the bus voltage), and can also avoid being unable to balance the module current due to excessively small compensation. The process is not limited by the specific value of the bus voltage (for example, the bus voltage of a converter of different power levels is different), and can adapt the same set of compensation logic to double-module converters of different specifications, thereby reducing the adaptation cost of the control program.

[0104] In some embodiments, the first gain coefficient of each phase is determined according to the historical voltage compensation value of each phase and the inter-module current difference of each phase, including:

[0105] Half of the inter-module current difference of each phase is taken as the first current difference;

[0106] The historical voltage compensation value of each phase is divided by the first current difference to obtain the corresponding first gain coefficient.

[0107] Specifically, the inter-module current difference of each phase is divided by 2, which is equivalent to taking the ideal current sharing current (the average of the two module currents) as the reference, so that the adjustment amplitude of the voltage compensation value is directly linked with the degree of current imbalance— the greater the current difference, the more appropriate the corresponding compensation effort, which can quickly pull the current back to the balanced state. The formula is as follows:

[0108] ;

[0109] wherein, is the A-phase current value of the first converter module, is the A-phase current value of the second converter module, is the inter-module current difference, is the first current difference, is the historical voltage compensation value.

[0110] The greater the current difference is, the greater the denominator is, and the corresponding voltage compensation amplitude will adapt to the imbalance degree, avoiding the problem that small current difference uses large compensation to cause oscillation, or large current difference uses small compensation to adjust imbalance, so that the current sharing adjustment is more accurate. The denominator takes half of the current difference between the modules of each phase, and is calculated based on the average current (ideal current sharing value) of the two modules to compensate, so that the voltage of a certain module does not suddenly jump, and the current of the current deviation module can be smoothly adjusted to the average value, reducing the risk of device overload due to sudden current change. When debugging, only the actual working condition needs to be adjusted , so that the current fluctuation under different loads can be adapted without frequent modification of the control logic.

[0111] The determination process of the first gain coefficient provided in the embodiment modifies the voltage around the intermediate value of the current of the two modules, so that the compensation voltage of a certain module does not suddenly jump, and the current of the current deviation module can be smoothly adjusted to the average value, reducing the risk of device overload caused by current fluctuation. The voltage compensation and current imbalance are accurately corresponding, which not only efficiently adjusts the current, but also protects the device.

[0112] In some embodiments, the determination process of the final gain coefficient includes:

[0113] The first gain coefficients of each phase are averaged to obtain the final gain coefficient;

[0114] Alternatively, the maximum first gain coefficient or the minimum first gain coefficient in the first gain coefficients of each phase is selected as the final gain coefficient;

[0115] Alternatively, if the current difference between the modules corresponding to each phase in the first gain coefficients of each phase is less than the preset current difference, the maximum first gain coefficient in the first gain coefficients of each phase is selected as the final gain coefficient; if the current difference between the modules corresponding to each phase in the first gain coefficients of each phase is not less than the preset current difference, the target first gain coefficients corresponding to the current difference between the modules of each phase less than the preset current difference are selected from the first gain coefficients of each phase, and the maximum target first gain coefficient is selected from the target first gain coefficients as the final gain coefficient.

[0116] Specifically, the converter has three phases, so the first gain coefficients of the three phases may be different. In order to determine the optimal gain coefficient, different first gain coefficients are processed here to select the optimal gain coefficient. The final gain coefficient can be obtained by averaging. It can also be randomly selected, and the maximum or minimum first gain coefficient can also be selected from a plurality of first gain coefficients. Alternatively, if the current difference between the modules corresponding to each phase in the first gain coefficients of each phase is less than the preset current difference, it means that all of them meet the setting condition and do not exceed the upper limit current difference, so the maximum first gain coefficient is selected.

[0117] In the case that the inter-module current difference corresponding to each phase in the first gain coefficient of each phase is not less than the preset current difference, it indicates that there is still part of the inter-module current difference that does not meet the set condition and exceeds the upper limit current difference. In this case, the target first gain coefficient corresponding to the set condition needs to be screened out. The maximum target first gain coefficient is selected from the target first gain coefficients as the final gain coefficient.

[0118] The embodiment provided in the present application determines the final gain coefficient from the plurality of first gain coefficients, improves the accuracy of the gain coefficient, narrows the difference between the final gain coefficients of each phase, and reduces the current difference between the modules.

[0119] In some embodiments, after determining the final gain coefficient, the method further comprises:

[0120] obtaining a first threshold value corresponding to the inter-module current difference of each phase of the double-fed converter module;

[0121] determining a critical gain coefficient according to the historical voltage compensation value and the first threshold value;

[0122] if the final gain coefficient is greater than the critical gain coefficient, returning to the step of obtaining the inter-module current difference of each phase obtained from the historical current value of each phase of the double-fed converter module;

[0123] if the final gain coefficient is less than or equal to the critical gain coefficient, entering the step of determining the current phase voltage compensation value corresponding to the current converter module according to the final gain coefficient and the current phase current value of the double-fed converter module.

[0124] Specifically, in the determination of the final gain coefficient, it is considered that the smaller the parameter is, the smaller the adjustment effect is, and the larger the parameter is, the stronger the adjustment effect is, but at the same time, current spikes will occur. Therefore, in actual application, the adjustment should be from small to large, and the value should not be directly set to prevent the control from being affected by the excessive adjustment. The compensation limit U0lim will affect the compensation effect. When the compensation is limited, the compensation effect will be poor; but if no appropriate limiting is added, the compensation will be too large to affect the modulation wave itself, thereby causing other problems. Considering that the maximum inter-module current deviation of a 10MW double-fed unit is 125A, a 1 times margin is set, at this time the compensation U is 0.0005, and therefore it is recommended that the upper limit be set to 0.0005.

[0125] In addition, considering the upper limit setting, the upper limit is taken as the first threshold value, and the upper limit gain coefficient (critical gain coefficient) can be determined according to the historical voltage compensation value and the first threshold value. If the final gain coefficient is greater than the critical gain coefficient, it indicates that the current gain coefficient setting is unreasonable, and a new final gain coefficient needs to be determined by reacquiring.

[0126] If the final gain coefficient is less than or equal to the critical gain coefficient, a subsequent step can be performed to obtain the current phase voltage compensation value corresponding to the current converter module.

[0127] The final gain coefficient provided by the embodiment limits the critical gain coefficient in the case encountered in actual application, so as to ensure the adjustment effect and reduce the influence of current peak.

[0128] In some embodiments, the process of determining the current phase voltage compensation value corresponding to the current converter module includes:

[0129] obtaining a current dead zone value of the double-fed converter module;

[0130] taking the first converter module of the double-fed converter module as the current converter module and taking the second converter module as another converter module;

[0131] performing mean value processing on the current phase current value of the current converter module and the current phase current value of another converter module to obtain a first average current value;

[0132] performing addition processing on the first average current value and the current dead zone value to obtain a first current value;

[0133] performing subtraction processing on the current phase current value of the current converter module and the first current value to obtain a second current value;

[0134] performing multiplication processing on the second current value and the final gain coefficient to obtain the current phase voltage compensation value corresponding to the current converter module.

[0135] Specifically, the formula is as follows:

[0136]

[0137] wherein, , is the current phase current value of the current converter module, is the current phase current value of another converter module, is the first average current value, is the current dead zone value of the double-fed converter module, is the first current value, is the second current value, is the final gain coefficient.

[0138] Taking the A-phase first converter module as an example, ; wherein, is the A-phase current value of the current converter module, is the A-phase current value of another converter module.

[0139] ​Figure 3 A power cycle platform topology provided by the embodiment of the application is shown in FIG. 1. Figure 3 The measured converter is tested and verified. Figure 4 A schematic diagram of the current values of each phase of the K=0 machine-side module provided by the embodiment of the application is shown in FIG. 2. Figure 4 In the diagram, the numbers 1, 2, 3 and 4 represent the first machine-side module A phase, the second machine-side module A phase, the first machine-side module B phase and the second machine-side module B phase respectively. When the gain coefficient K is 0, the effective value difference of the machine-side module A current is 20.1 A, and the effective value difference of the machine-side module B current is 62.4 A.

[0140] Figure 5 A schematic diagram of the current values of each phase of the K=0.00003 machine-side module provided by the embodiment of the application is shown in FIG. 3. Figure 5 When the gain coefficient K is 0.00003, the effective value difference of the machine-side module A current is 10.8 A, and the effective value difference of the machine-side module B current is 50.3 A.

[0141] Figure 6 A schematic diagram of the current values of each phase of the K=0.00004 machine-side module provided by the embodiment of the application is shown in FIG. 4. Figure 6 When the gain coefficient K is 0.00004, the effective value difference of the machine-side module A current is 9.4 A, and the effective value difference of the machine-side module B current is 48.1 A.

[0142] Figure 7 A schematic diagram of the current values of each phase of the K=0.00006 machine-side module provided by the embodiment of the application is shown in FIG. 5. Figure 7 When the gain coefficient K is 0.00006, the effective value difference of the machine-side module A current is 6.9 A, and the effective value difference of the machine-side module B current is 44.2 A.

[0143] Figure 8 A schematic diagram of the current values of each phase of the K=0.00008 machine-side module provided by the embodiment of the application is shown in FIG. 6. Figure 8 When the gain coefficient K is 0.00008, the effective value difference of the machine-side module A current is 0.9 A, and the effective value difference of the machine-side module B current is 33.7 A. As the gain coefficient increases, the uneven current degree between the modules decreases.

[0144] The determination process of the current phase voltage compensation value corresponding to the current converter module provided by the embodiment ensures that the current borne by each power module is highly consistent through high-precision static and dynamic current sharing control. This avoids early failure caused by long-term overload of individual modules, thereby significantly prolonging the service life of the entire converter system.

[0145] After the final gain coefficient is obtained, the current phase voltage compensation value corresponding to the current converter module is obtained through the compensation formula. The thermal stress of power devices (IGBT) and magnetic elements (reactors) is reduced, the failure caused by overheating is reduced, and the reliability of long-term operation of the system is improved. Improve the overall efficiency of the system: due to the elimination of the additional loss caused by circulating current, and make each module work near the optimal efficiency point, the average operating efficiency of the system in a wide power range is effectively improved, which directly increases the power generation income of the wind farm. Improve the quality of output power: balanced load and controlled circulating current make the total output current waveform of the parallel system smoother and the total harmonic distortion (THD) lower, meeting or even better than the stringent requirements of the power grid on power quality. Excellent dynamic response performance: the algorithm can quickly adjust the output of each module during dynamic processes such as wind speed mutation or grid voltage disturbance, prevent dynamic uneven flow and overshoot current, ensure system stability, and enhance the adaptability of the fan to complex working conditions. Reduce the stringent requirements for consistency of components: the traditional scheme needs to strictly select components with high parameter consistency to ensure current sharing. Through the "intelligent" compensation of the algorithm, the tolerance requirements for components (such as IGBT, inductor) are reduced, thereby reducing the procurement cost and manufacturing difficulty.

[0146] Further, the application also provides a double-fed converter, Figure 9 A structural schematic diagram of a double-fed converter provided by an embodiment of the application is shown in Figure 9 As shown, the double-fed converter includes a first machine-side converter 1 and a second machine-side converter 2.

[0147] The control end of the first machine-side converter 1 is connected with a first reactor L1, a controller 3 and a double-fed induction generator DFIG; the control end of the second machine-side converter 2 is connected with a second reactor L2, the controller 3 and the double-fed induction generator DFIG; wherein the controller 3 is used to execute the steps of the current equalization method of the double-fed converter module described above, so as to reduce the current difference between the double-fed converter modules.

[0148] The first end and the second end of the first machine-side converter 1 and the second machine-side converter 2 are respectively connected to the two ends of a DC bus capacitor C1.

[0149] The first end and the second end of the grid-side converter 4 are connected to both ends of the direct current bus capacitor C1; the control end of the grid-side converter 4 is connected to the first end of the third reactor L3; the second end of the third reactor L3 is connected to the first end of the first switch K1 and the first end of the first resistor R1; the second end of the first switch K1 is connected to the first end of the first circuit breaker QF1; the second end of the first resistor R1 is connected to the first end of the second switch K2; the second end of the second switch K2 and the second end of the first circuit breaker QF1 are both connected to the first end of the second circuit breaker QF2; the second end of the second circuit breaker QF2 is connected to the first end of the step-up transformer T1;

[0150] The third switch K3 is connected to the double-fed induction generator DFIG; the second end of the third switch K3 is connected to the first end of the third circuit breaker QF3; the second end of the third circuit breaker QF3 is connected to the second end of the step-up transformer T1;

[0151] The third end of the step-up transformer T1 is connected to the first end of the fourth circuit breaker QF4; the second end of the fourth circuit breaker QF4 is connected to the external power grid.

[0152] Specifically, the machine-side converter outputs greater current in parallel to drive the motor. In the power generation link, the fan blades capture wind energy to rotate and drive the double-fed induction generator (DFIG) to operate - the stator of the DFIG is directly connected to the step-up transformer, and the rotor is connected to the double-mode machine-side converter (machine-side converter 1 / 2 in parallel, improving power capacity). In the power conversion link, the machine-side converter (AC / DC): rectifies the AC power output by the DFIG rotor into DC power, while adjusting the speed, active / reactive power of the generator. The DC bus capacitor: stabilizes the DC voltage output by the machine-side converter as an energy buffer pool; the grid-side converter (AC / DC): inverts the DC power of the DC bus into AC power that meets the requirements of the power grid, while controlling the stability of the DC bus voltage, and delivering power to the power grid.

[0153] Through the connection relationship of the buffer resistor (first resistor) and the second switch, when the converter starts, the buffer resistor is first connected to the circuit to limit the impact current, and after the DC bus voltage is stable, the second switch is closed to short-circuit the buffer resistor.

[0154] The remaining switches and circuit breakers control the on-off of each link and quickly disconnect the protection equipment in case of failure. The step-up transformer increases the medium / low voltage (such as 10.2kV) output by the generator / converter to high voltage (such as 35kV) of the power grid, reduces power transmission loss, and finally connects to the external power grid through the fourth circuit breaker. The double-mode machine-side converter improves the power handling capacity, and the switches and resistors ensure the safe and stable operation of the system.

[0155] For the introduction of the double-fed converter module provided by the application, please refer to the above method embodiments, and the application will not be described here. It has the same beneficial effects as the current balancing method of the double-fed converter module described above.

[0156] The above detailed description of the current balancing method of the double-fed converter module corresponds to each embodiment, on the basis of which the application also discloses a current balancing device of the double-fed converter module corresponding to the above method, Figure 10 The structure diagram of the current balancing device of the double-fed converter module provided by the embodiment of the application is shown in FIG. 1. Figure 10 As shown in the figure, the current balancing device of the double-fed converter module comprises:

[0157] The acquisition module 11 is configured to acquire the inter-module current difference of each phase obtained by the historical current value of each phase of the double-fed converter module, so as to determine the inter-module voltage difference of each phase.

[0158] The first determination module 12 is configured to determine the historical voltage compensation value of each phase based on the inter-module voltage difference of each phase and the historical DC bus voltage value, and determine the first gain coefficient of each phase according to the historical voltage compensation value of each phase and the inter-module current difference of each phase, so as to determine the final gain coefficient.

[0159] The second determination module 13 is configured to determine the current phase voltage compensation value corresponding to the current converter module according to the final gain coefficient and the current phase current value of the double-fed converter module, so as to be added to the control end of the double-fed converter to realize current balancing.

[0160] Since the embodiments of the device part correspond to the above embodiments, the embodiments of the device part will be described with reference to the above method embodiments, and will not be described here.

[0161] For the introduction of the current balancing device of the double-fed converter module provided by the application, please refer to the above method embodiments, and the application will not be described here. It has the same beneficial effects as the current balancing method of the double-fed converter module described above.

[0162] Figure 11 The structure diagram of the wind power generation system provided by the embodiment of the application is shown in FIG. 2. Figure 11 As shown in the figure, it comprises:

[0163] The memory 21 is configured to store the computer program.

[0164] The processor 22 is configured to execute the computer program to realize the steps of the current balancing method of the double-fed converter module.

[0165] The processor 22 can include one or more processing cores, such as a 4-core processor, an 8-core processor, etc. The processor 22 can be implemented in at least one of a hardware form of a digital signal processor (DSP), a field-programmable gate array (FPGA), a programmable logic array (PLA), etc. The processor 22 can also include a main processor and a coprocessor. The main processor is a processor for processing data in a wake-up state, also referred to as a central processing unit (CPU). The coprocessor is a low-power processor for processing data in a standby state. In some embodiments, the processor 22 can be integrated with a graphics processing unit (GPU) for rendering and drawing content required to be displayed by a display screen. In some embodiments, the processor 22 can further include an artificial intelligence (AI) processor for processing computing operations related to machine learning.

[0166] The memory 21 can include one or more computer-readable storage media that can be non-transitory. The memory 21 can further include a high-speed random access memory, and a nonvolatile memory such as one or more disk storage devices, flash storage devices. In the present embodiment, the memory 21 is at least used to store a computer program 211, wherein the computer program is loaded and executed by the processor 22, and can implement the related steps of the current balancing method of the double-fed current converter module disclosed in any of the preceding embodiments. In addition, the resources stored by the memory 21 can further include an operating system 212 and data 213, etc., and the storage manner can be temporary storage or permanent storage. The operating system 212 can include Windows, Unix, Linux, etc. The data 213 can include, but is not limited to, data related to the current balancing method of the double-fed current converter module, etc.

[0167] In some embodiments, the system can further include a display screen 23, an input / output interface 24, a communication interface 25, a power supply 26, and a communication bus 27.

[0168] Those skilled in the art can understand that the structure shown in the above embodiments does not constitute a limitation on the system, and can include more or fewer components than those shown in the drawings. Figure 11 The structure shown in the above embodiments does not constitute a limitation on the system, and can include more or fewer components than those shown in the drawings.

[0169] The processor 22 implements the current balancing method of the double-fed converter module provided by any of the above embodiments by calling instructions stored in the memory 21.

[0170] For the wind power generation system provided by the present application, refer to the above method embodiments, and the present application will not be repeated here, which has the same beneficial effects as the above current balancing method of the double-fed converter module.

[0171] Further, the present application also provides a computer readable storage medium, and the computer readable storage medium stores a computer program, and the computer program is executed by the processor 22 to implement the steps of the above current balancing method of the double-fed converter module.

[0172] It can be understood that if the method in the above embodiments is implemented in the form of a software function unit and sold or used as an independent product, it can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application essentially or the part that contributes to the prior art or the whole or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, and executes all or part of the steps of the methods of the various embodiments of the present application. The foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and various media that can store program codes.

[0173] For the computer readable storage medium provided by the present application, refer to the above method embodiments, and the present application will not be repeated here, which has the same beneficial effects as the above current balancing method of the double-fed converter module.

[0174] The above provides a current balancing method, a double-fed converter, a wind power generation system and a medium. The embodiments in the specification are described in a progressive manner, and each embodiment mainly describes the differences from other embodiments. For the device disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and the related parts are described in the method part. It should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, the present application can be improved and modified, and these improvements and modifications also fall within the protection scope of the present application.

[0175] It also needs to be explained that in the present specification, the relational terms such as first and second and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

Claims

1. A current balancing method for a doubly-fed converter module, characterized in that, include: The inter-module current difference of each phase is obtained from the historical current values ​​of each phase of the doubly fed converter module, so as to determine the inter-module voltage difference of each phase. The historical voltage compensation value for each phase is determined based on the inter-module voltage difference and the historical DC bus voltage value. The first gain coefficient of each phase is determined based on the historical voltage compensation value of each phase and the current difference between modules of each phase, so as to determine the final gain coefficient. Based on the final gain coefficient and the current phase current value of the doubly-fed converter module, the current phase voltage compensation value corresponding to the current converter module is determined and added to the control terminal of the doubly-fed converter to achieve current balance.

2. The current balancing method for a doubly-fed converter module according to claim 1, characterized in that, The process of determining the current phase voltage compensation value corresponding to the current converter module includes: Obtain the current dead zone value of the doubly fed converter module; The first converter module of the doubly fed converter module is used as the current converter module, and the second converter module is used as another converter module. The first average current value is obtained by averaging the current phase current value of the current converter module with the current phase current value of another converter module. The first average current value is obtained by adding the first current dead zone value to the first current value. The second current value is obtained by subtracting the current phase current value of the current converter module from the first current value. The second current value is multiplied by the final gain coefficient to obtain the current phase voltage compensation value corresponding to the current converter module.

3. The current balancing method for a doubly-fed converter module according to claim 1, characterized in that, The historical voltage compensation value for each phase is determined based on the inter-module voltage difference and the historical DC bus voltage value, including: The effective value of the corresponding phase voltage is determined based on the voltage difference between the modules of each phase; The maximum line voltage is determined based on the effective value of the phase voltage of each phase; The historical voltage compensation value for each phase is determined based on the maximum line voltage of each phase and the historical DC bus voltage value.

4. The current balancing method for a doubly-fed converter module according to claim 3, characterized in that, The first gain coefficient for each phase is determined based on the historical voltage compensation value of each phase and the inter-module current difference of each phase, including: Half of the current difference between the modules of each phase is taken as the first current difference. The corresponding first gain coefficient is obtained by dividing the historical voltage compensation value of each phase by the first current difference.

5. The current balancing method for a doubly-fed converter module according to claim 4, characterized in that, The final process for determining the gain coefficient includes: The final gain coefficient is obtained by averaging the first gain coefficient of each phase. Alternatively, the largest or smallest first gain coefficient among the first gain coefficients of each phase can be selected as the final gain coefficient. Alternatively, if the inter-module current difference in each phase is less than the preset current difference in the first gain coefficient of each phase, then the largest first gain coefficient in the first gain coefficient of each phase is selected as the final gain coefficient; if the inter-module current difference in each phase is not less than the preset current difference in the first gain coefficient of each phase, then the target first gain coefficients corresponding to the inter-module current difference in each phase being less than the preset current difference are selected from the first gain coefficients of each phase, and the largest target first gain coefficient in the target first gain coefficients is selected as the final gain coefficient.

6. The current balancing method for a doubly-fed converter module according to claim 1, characterized in that, After determining the final gain coefficient, the following steps are also included: Obtain the first threshold corresponding to the inter-module current difference of each phase of the doubly fed converter module; The critical gain coefficient is determined based on historical voltage compensation values ​​and the first threshold. If the final gain coefficient is greater than the critical gain coefficient, then return to the step of obtaining the inter-module current difference value of each phase obtained from the historical current value of each phase of the doubly fed converter module. If the final gain coefficient is less than or equal to the critical gain coefficient, then proceed to the step of determining the current phase voltage compensation value corresponding to the current converter module based on the final gain coefficient and the current phase current value of the doubly fed converter module.

7. The current balancing method for a doubly-fed converter module according to claim 1, characterized in that, The process of determining the voltage difference between modules in each phase includes: Obtain the reactor inductance and angular frequency of the doubly fed converter module; The inter-module voltage difference of each phase is obtained by multiplying the inter-module current difference, angular frequency, and reactor inductance value.

8. A doubly-fed converter, characterized in that, Including the first-side converter and the second-side converter; The control terminal of the first generator-side converter is connected to the first reactor, the controller, and the doubly-fed induction generator; the control terminal of the second generator-side converter is connected to the second reactor, the controller, and the doubly-fed induction generator; wherein, the controller is used to execute the steps of the current balancing method for the doubly-fed converter module according to any one of claims 1 to 7, so as to reduce the current difference between the doubly-fed converter modules; The first terminal and the second terminal of the first machine-side converter and the second machine-side converter are respectively connected to the two ends of the DC bus capacitor; The two ends of the DC bus capacitor are connected to the first and second ends of the grid-side converter; the control end of the grid-side converter is connected to the first end of the third reactor; the second end of the third reactor is connected to the first end of the first switch and the first end of the first resistor; the second end of the first switch is connected to the first end of the first circuit breaker; the second end of the first resistor is connected to the first end of the second switch; the second end of the second switch and the second end of the first circuit breaker are both connected to the first end of the second circuit breaker; the second end of the second circuit breaker is connected to the first end of the step-up transformer. The doubly-fed induction generator is connected to the first terminal of the third switch; the second terminal of the third switch is connected to the first terminal of the third circuit breaker; the second terminal of the third circuit breaker is connected to the second terminal of the step-up transformer. The third terminal of the step-up transformer is connected to the first terminal of the fourth circuit breaker; the second terminal of the fourth circuit breaker is connected to the external power grid.

9. A wind power generation system, characterized in that, include: Memory, used to store computer programs; A processor, configured to implement the current balancing method for a doubly fed converter module as described in any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the current balancing method for a doubly fed converter module as described in any one of claims 1 to 7.

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