A wind-solar complementary based zero-carbon power supply method and system

Abstract

The application discloses a zero-carbon power supply method and system based on wind-solar complementation, relates to the technical field of zero-carbon power supply, and comprises the following steps: acquiring the first control loop bandwidth and the first initial voltage rise rate of a wind turbine generator and the second control loop bandwidth and the second initial voltage rise rate of a photovoltaic converter; determining the voltage build-up starting time delay and the voltage rise slope of the wind turbine generator and the photovoltaic converter based on the parameters, and executing soft start voltage build-up by issuing the voltage build-up starting time delay and the voltage rise slope; determining the frequency offset compensation amount according to the phase difference of the output voltage, and superimposing the frequency offset compensation amount on the voltage reference angle frequency of the lagging equipment; and adjusting the voltage amplitude reference according to the circulating current reactive component on the AC microgrid bus. The application eliminates concurrent field excitation conflicts through heterogeneous characteristic calculation time sequence peak shifting, actively suppresses phase drift and circulating current by combining frequency offset compensation and amplitude reference adjustment, and guarantees smooth transition of the AC microgrid voltage to the rated value.

Description

Technical Field

[0001] This application relates to the field of zero-carbon power supply technology, and in particular to a zero-carbon power supply method and system based on wind-solar hybridization. Background Technology

[0002] When a wind-solar hybrid zero-carbon system performs black-start operation in islanded mode, it relies on the wind turbine and photovoltaic converter to work together to establish the AC microgrid bus voltage. Wind and solar resources are usually available simultaneously, and the wind turbine and photovoltaic converter often perform soft-start voltage building-up processes at the same time.

[0003] However, wind turbines and photovoltaic converters differ fundamentally in hardware topology and control structure. Their control loop bandwidths and initial voltage rise rates also differ. When both wind turbines and photovoltaic converters simultaneously perform soft-start voltage build-up, asynchronous excitation conflicts arise during the establishment of AC voltage amplitude and phase. This asynchronous excitation conflict leads to voltage distortion on the AC microgrid bus, low-frequency oscillations, and severe active and reactive circulating currents.

[0004] Due to the existence of asynchronous excitation conflict, the AC voltage of the AC microgrid can never be stabilized at the rated value, and the wind-solar hybrid zero-carbon system cannot smoothly complete the transition from start-up to steady-state voltage build-up.

[0005] Existing black-start control methods typically focus only on the voltage build-up capability of a single device or employ simple delayed start-up strategies. They fail to deeply analyze the dynamic impact of the differences in control characteristics between wind turbines and photovoltaic converters on the construction of AC microgrid bus voltage. They lack accurate decoupling calculations of voltage build-up timing and active intervention on phase deviation and circulating current components, leading to steady-state voltage build-up failure during the black-start process. Summary of the Invention

[0006] In view of the above-mentioned problems, this application provides a zero-carbon power supply method and system based on wind-solar hybridization, which can solve the problems of AC microgrid voltage distortion and circulating current caused by asynchronous excitation conflict of heterogeneous converters in wind-solar hybridization black start.

[0007] To solve the above-mentioned technical problems, this application adopts the following technical solution: In a first aspect, this application provides a zero-carbon power supply method based on wind-solar hybridization, including: obtaining the first control loop bandwidth and the first initial voltage rise rate of the wind turbine generator and the second control loop bandwidth and the second initial voltage rise rate of the photovoltaic converter. Based on the first control loop bandwidth, the first initial voltage rise rate, the second control loop bandwidth, and the second initial voltage rise rate, the voltage build-up start-up delay and voltage rise slope of the wind turbine and photovoltaic converter are determined. The voltage build-up delay and voltage rise slope are sent to the corresponding wind turbines and photovoltaic converters to perform soft-start voltage build-up. The frequency offset compensation amount is determined based on the phase difference between the output voltages of the wind turbine and the photovoltaic converter, and then the frequency offset compensation amount is superimposed on the voltage reference angular frequency of the lagging device. Adjust the voltage amplitude reference of the corresponding wind turbine and photovoltaic converter based on the circulating reactive component on the AC microgrid bus.

[0008] Preferably, the step of determining the voltage rise delay and voltage ramp of the wind turbine and photovoltaic converter based on the first control loop bandwidth, the first initial voltage rise rate, the second control loop bandwidth, and the second initial voltage rise rate includes: Based on the reciprocal relationship between the bandwidth of the first control loop and the bandwidth of the second control loop, the voltage build-up response hysteresis time of the wind turbine and the photovoltaic converter are determined respectively. The voltage build-up response hysteresis time characterizes the delay characteristics of the converter in responding to the voltage command. The first initial voltage rise rate is compared with the second initial voltage rise rate to determine the time difference between the wind turbine and the photovoltaic converter reaching the rated voltage. Based on the pressure build-up response hysteresis time and time difference, the initial start-up times of wind turbines and photovoltaic converters are staggered to obtain the pressure build-up start-up delay. The staggered arrangement is used to eliminate the asynchronous excitation conflict caused by the simultaneous pressure build-up of the two. Based on the voltage rise time delay correction of the first initial voltage rise rate and the second initial voltage rise rate, the voltage rise slope of the wind turbine and the photovoltaic converter is obtained. The voltage rise slope ensures that both reach the rated voltage amplitude at the same time.

[0009] Preferably, the step of comparing the first initial voltage rise rate with the second initial voltage rise rate to determine the time difference between the wind turbine and the photovoltaic converter reaching the rated voltage includes: Obtain the rated voltage amplitude of the AC microgrid bus, and divide the rated voltage amplitude by the first initial voltage rise rate and the second initial voltage rise rate respectively to determine the first theoretical voltage build-up time and the second theoretical voltage build-up time; The time difference between the first theoretical voltage build-up time and the second theoretical voltage build-up time is calculated to determine the time difference between the wind turbine and the photovoltaic converter reaching the rated voltage. The asynchronous excitation time interval between the wind turbine and the photovoltaic converter is determined by summing the pressure build-up response hysteresis time and the time difference. The asynchronous excitation time interval covers the difference between dynamic response hysteresis and steady-state pressure build-up rate. The asynchronous excitation time interval is used as the voltage build-up start delay and allocated to the device start-up time corresponding to the second initial voltage rise rate, thereby triggering the device corresponding to the second initial voltage rise rate to start the voltage build-up process in advance.

[0010] Preferably, the step of determining the frequency offset compensation amount based on the phase difference between the output voltages of the wind turbine and the photovoltaic converter, and then superimposing the frequency offset compensation amount onto the voltage reference angular frequency of the lagging device, includes: During the soft-start voltage build-up process, the instantaneous amplitude and zero-crossing time of the output voltage of the wind turbine and photovoltaic converter are obtained. The zero-crossing time is used to extract the real-time phase information of the output voltage of the two. The actual phase difference between the output voltage of the wind turbine and the output voltage of the photovoltaic converter is determined based on the zero-crossing time. The actual phase difference characterizes the degree of synchronization misalignment between the two on the AC microgrid bus. The actual phase difference is integrated on the time axis to determine the cumulative phase deviation between the wind turbine and the photovoltaic converter. The cumulative phase deviation reflects the cumulative effect of phase drift during the dynamic voltage build-up process. The accumulated phase deviation is converted into a frequency offset compensation amount, and the frequency offset compensation amount is superimposed on the voltage reference angular frequency of the lagging device. The voltage reference angular frequency of the lagging device is then adjusted to offset the accumulated phase deviation.

[0011] Preferably, determining the actual phase difference between the wind turbine output voltage and the photovoltaic converter output voltage based on the zero-crossing moment includes: By comparing the zero-crossing time of the wind turbine output voltage with the zero-crossing time of the photovoltaic converter output voltage, the leading zero-crossing device and the lagging zero-crossing device are identified. The leading zero-crossing device and the lagging zero-crossing device constitute an asymmetric compensation object. Using the output voltage phase of the leading zero-crossing device as the reference phase, the electrical angle by which the output voltage phase of the lagging zero-crossing device lags behind the reference phase is determined, and the electrical angle is used to quantify the phase mismatch between heterogeneous converters. The electrical angle is taken as the actual phase difference, and the lagging zero-crossing device is identified as the lagging device that needs frequency compensation. Frequency compensation is only performed on the lagging device to block the additional oscillation excitation path. The frequency offset compensation amount of the lagging equipment is determined based on the ratio of the actual phase difference to the time elapsed during soft start-up pressure build-up. The frequency offset compensation amount is dynamically updated over time to adapt to changes in the pressure build-up trajectory.

[0012] Preferably, the step of adjusting the voltage amplitude reference of the corresponding wind turbine and photovoltaic converter based on the circulating reactive power component on the AC microgrid bus includes: The three-phase instantaneous current and three-phase instantaneous voltage on the AC microgrid bus are obtained, and the three-phase instantaneous current and three-phase instantaneous voltage are transformed into an orthogonal rotating coordinate system. The orthogonal rotating coordinate system decouples the active and reactive components. In an orthogonal rotating coordinate system, the reactive current component on the AC microgrid bus is extracted as the circulating reactive component, which directly reflects the degree of voltage amplitude mismatch between heterogeneous converters. The circulating reactive component is compared with the reactive power allowable fluctuation threshold. In response to the circulating reactive component exceeding the reactive power allowable fluctuation threshold, a reactive power adjustment command is generated. The reactive power allowable fluctuation threshold defines the boundary between normal operation and abnormal circulating current. The reactive power adjustment command is converted into a voltage amplitude compensation amount and superimposed on the voltage amplitude reference of the wind turbine and photovoltaic converter, thereby modifying the command source to offset the circulating reactive power component.

[0013] Preferably, the step of converting the reactive power adjustment command into a voltage amplitude compensation amount and adding it to the voltage amplitude reference of the wind turbine and the photovoltaic converter includes: Based on the positive and negative polarities of the circulating reactive power components, the surplus or shortage state of reactive power on the AC microgrid bus is determined. The surplus or shortage state of reactive power indicates the direction of circulating current flow and the strength of voltage support. Based on the surplus and shortage of reactive power, the voltage amplitude compensation is divided into the first amplitude compensation corresponding to the wind turbine and the second amplitude compensation corresponding to the photovoltaic converter. The first amplitude compensation and the second amplitude compensation have opposite adjustment characteristics. The first amplitude compensation amount is added to the initial voltage amplitude reference of the wind turbine, and the second amplitude compensation amount is added to the initial voltage amplitude reference of the photovoltaic converter. The addition operation is performed before the voltage closed-loop control. The summed result is used as the updated voltage amplitude reference and sent to the corresponding wind turbine and photovoltaic converter to perform voltage closed-loop control, correcting the AC microgrid bus voltage to match the rated value.

[0014] Preferably, the step of extracting the reactive current component on the AC microgrid bus as the circulating reactive component in an orthogonal rotating coordinate system includes: The active power and reactive power of the wind turbine and photovoltaic converter in the orthogonal rotating coordinate system are obtained. The active power and reactive power are calculated from their respective output current and voltage coordinate components. The reactive power of the wind turbine generator and the reactive power of the photovoltaic converter are calculated to extract the reactive power difference value, which represents the imbalance between the two in reactive power support. The reactive power difference is divided by the rated voltage amplitude of the AC microgrid bus to obtain the circulating reactive power component. The conversion process maps the power domain difference to the current domain characteristics. The circulating reactive component is low-pass filtered to remove high-frequency switching harmonic interference, resulting in a smooth circulating reactive component used to generate reactive power adjustment commands. The smooth circulating reactive component also blocks high-frequency noise from entering the controller.

[0015] Preferably, the step of adjusting the voltage amplitude reference of the corresponding wind turbine and photovoltaic converter based on the circulating reactive power component on the AC microgrid bus further includes: The fundamental component and total harmonic component of the AC microgrid bus voltage are obtained, and the ratio of the total harmonic component to the fundamental component is determined as the voltage distortion rate. The voltage distortion rate characterizes the degree to which the AC microgrid bus voltage deviates from the sine wave. The voltage distortion rate is compared with the voltage distortion threshold. In response to the voltage distortion rate being greater than the voltage distortion threshold, frequency fine-tuning command and amplitude fine-tuning command are generated. The voltage distortion threshold distinguishes between normal operation and distortion oscillation state. The frequency fine-tuning command is superimposed on the voltage reference angular frequency of the wind turbine and photovoltaic converter to adjust the zero-crossing time of the output voltage of the wind turbine and photovoltaic converter, thereby changing the excitation period of the low-frequency oscillation. The amplitude fine-tuning command is superimposed on the voltage amplitude reference of the wind turbine and photovoltaic converter to adjust the peak and trough deviation of the AC microgrid bus voltage and reduce the amplitude of the active and reactive circulating current components.

[0016] Secondly, this application also provides a zero-carbon power supply system based on wind-solar hybridization, including: a characteristic acquisition module, a time-series slope determination module, a voltage build-up control module, a phase compensation module, and an amplitude adjustment module; The feature acquisition module is used to acquire the first control loop bandwidth and the first initial voltage rise rate of the wind turbine, and the second control loop bandwidth and the second initial voltage rise rate of the photovoltaic converter. The timing slope determination module is used to determine the voltage rise delay and voltage rise slope of the wind turbine and photovoltaic converter based on the first control loop bandwidth, the first initial voltage rise rate, the second control loop bandwidth and the second initial voltage rise rate. The voltage build-up control module is used to send the voltage build-up start-up delay and voltage rise slope to the corresponding wind turbine and photovoltaic converter to perform soft start voltage build-up; The phase compensation module is used to determine the frequency offset compensation amount based on the phase difference between the output voltage of the wind turbine and the photovoltaic converter, and to add the frequency offset compensation amount to the voltage reference angular frequency of the lagging device. The amplitude adjustment module is used to adjust the voltage amplitude reference of the corresponding wind turbine and photovoltaic converter based on the circulating reactive component on the AC microgrid bus.

[0017] Implementing this application has the following beneficial effects: This application precisely calculates the asynchronous excitation time interval and staggers the initial start-up times by quantitatively analyzing the differences in control loop bandwidth and initial voltage rise rate between the wind turbine and the photovoltaic converter, thereby eliminating concurrent excitation conflicts at the source. Simultaneously, based on the zero-crossing moment of the output voltage, the accumulated phase deviation is extracted in real time and converted into a frequency offset compensation amount, which is then superimposed on the voltage reference angular frequency of the lagging device to actively suppress phase drift during the voltage build-up process. Furthermore, by decoupling and extracting the circulating reactive component through an orthogonal rotating coordinate system, reverse adjustment compensation is applied to the voltage amplitude reference of the wind turbine and the photovoltaic converter, eliminating the active and reactive circulating currents caused by voltage amplitude mismatch between heterogeneous converters from the command source. The above three collaborative control methods jointly ensure the smooth and reliable transition of the AC microgrid voltage from black-start excitation to the steady-state rated value, solving the core problem of black-start steady-state voltage build-up failure caused by the lack of refined modeling of the differences in control characteristics of heterogeneous converters in existing technologies. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is an overall flowchart of a zero-carbon power supply method based on wind-solar hybridization involved in this application; Figure 2 This application relates to a flowchart of a heterogeneous converter that converts reactive power adjustment commands into voltage amplitude compensation amounts and superimposes them onto the voltage amplitude references of wind turbines and photovoltaic converters in a zero-carbon power supply method based on wind-solar complementarity. Figure 3 This is a flowchart illustrating the voltage amplitude compensation amount based on the surplus / deficient state of reactive power in a zero-carbon power supply method based on wind-solar hybridization, which is the subject of this application. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0021] This application provides a zero-carbon power supply method and system based on wind-solar hybrid power, including: like Figure 1 The diagram shown is a flowchart of a zero-carbon power supply method based on wind-solar hybridization, including: Step S1: Obtain the first control loop bandwidth and the first initial voltage rise rate of the wind turbine generator, and the second control loop bandwidth and the second initial voltage rise rate of the photovoltaic converter.

[0022] The fundamental differences in hardware topology and control structure between wind turbine generators and photovoltaic converters lead to differences in the bandwidth of the first control loop of the wind turbine generator and the bandwidth of the second control loop of the photovoltaic converter. Furthermore, the first initial voltage rise rate of the wind turbine generator and the second initial voltage rise rate of the photovoltaic converter also differ. If soft-start voltage building is performed directly without obtaining these parameters, asynchronous excitation conflicts will occur when the wind turbine generator and the photovoltaic converter establish AC voltage amplitude and phase, resulting in voltage distortion and low-frequency oscillations on the AC microgrid bus. Therefore, it is essential to obtain these four parameters as the reference inputs for subsequent timing decoupling and slope correction.

[0023] The bandwidth of the first control loop and the first initial voltage rise rate of the wind turbine, as well as the bandwidth of the second control loop and the second initial voltage rise rate of the photovoltaic converter, can be directly read from the controller parameter library of the wind turbine and the photovoltaic converter. Alternatively, a small-amplitude sweep frequency signal can be injected into the voltage control loop of the two types of equipment through a black-box identification method. The loop bandwidth and the initial voltage rise rate can be obtained by fitting the output response. Parameter acquisition can be completed without the need for additional detection hardware, making it compatible with heterogeneous wind and solar converters of different brands and capacities.

[0024] Step S2: Based on the first control loop bandwidth, the first initial voltage rise rate, the second control loop bandwidth, and the second initial voltage rise rate, determine the voltage build-up start-up delay and voltage rise slope of the wind turbine and the photovoltaic converter.

[0025] When wind turbines and photovoltaic converters perform soft-start voltage building up simultaneously, the response hysteresis and voltage building up rate difference prevent them from reaching the rated voltage at the same time, causing asynchronous excitation conflict. Therefore, it is necessary to analyze the differences between the dynamic response and steady-state voltage building up dimensions based on the above four parameters, construct a staggered timing sequence and a corrected slope to ensure that both reach the rated voltage amplitude at the same time, thereby fundamentally eliminating concurrent excitation conflict.

[0026] In some embodiments, determining the voltage rise delay and voltage ramp of the wind turbine and photovoltaic converter based on the first control loop bandwidth, the first initial voltage rise rate, the second control loop bandwidth, and the second initial voltage rise rate includes: Step S21: Based on the reciprocal relationship between the bandwidth of the first control loop and the bandwidth of the second control loop, determine the voltage build-up response hysteresis time of the wind turbine and the photovoltaic converter respectively. The voltage build-up response hysteresis time characterizes the delay characteristics of the converter in responding to the voltage command.

[0027] To accurately quantify the delay characteristics between the received voltage command and the actual output voltage response of wind turbines and photovoltaic converters, this application provides a hysteresis time calculation method based on the reciprocal relationship of the control loop bandwidth, in order to solve the problem of difficulty in measuring the dynamic response differences of heterogeneous converters.

[0028] Furthermore, the bandwidth of the first control loop of the wind turbine and the bandwidth of the second control loop of the photovoltaic converter are obtained. The control loop bandwidth characterizes the frequency band range of the system for tracking commands. The bandwidth value is directly proportional to the response speed, and the reciprocal of the bandwidth is the basic time constant of the system response to commands.

[0029] The reciprocal of the bandwidth of the first control loop is determined as the voltage build-up response hysteresis time of the wind turbine, and the reciprocal of the bandwidth of the second control loop is determined as the voltage build-up response hysteresis time of the photovoltaic converter.

[0030] In this embodiment, the bandwidth of the first control loop is denoted as... The bandwidth of the second control loop is denoted as The pressure build-up response hysteresis time of wind turbine units equal The reciprocal of the voltage build-up response hysteresis of the photovoltaic converter equal The reciprocal of the voltage build-up response hysteresis. The voltage build-up response hysteresis directly reflects the inherent delay characteristics of the converter hardware and control loop, and serves as a fundamental component for subsequent calculations of the asynchronous excitation time interval.

[0031] Step S22: Compare the first initial voltage rise rate with the second initial voltage rise rate to determine the time difference between the wind turbine and the photovoltaic converter reaching the rated voltage. The time difference reflects the difference in the voltage build-up rate between the two.

[0032] Because the initial voltage rise rate of wind turbines and photovoltaic converters differs, even if the voltage build-up process starts simultaneously, there will inevitably be a deviation in the time when they reach the rated voltage. This deviation is one of the core reasons for asynchronous excitation conflict. Therefore, it is necessary to compare the initial voltage rise rate to quantify the time difference.

[0033] In some embodiments, comparing the first initial voltage rise rate with the second initial voltage rise rate to determine the time difference between the wind turbine and the photovoltaic converter reaching the rated voltage includes: Step S221: Obtain the rated voltage amplitude of the AC microgrid bus, divide the rated voltage amplitude by the first initial voltage rise rate and the second initial voltage rise rate respectively, and determine the first theoretical voltage build-up time and the second theoretical voltage build-up time.

[0034] In this embodiment of the application, after obtaining the rated voltage amplitude of the AC microgrid bus, the theoretical voltage build-up time of the wind turbine and the photovoltaic converter is output according to the ratio of the rated voltage amplitude to the initial voltage rise rate.

[0035] Accordingly, the rated voltage amplitude of the AC microgrid bus is read from the AC microgrid control system parameter library, and the first initial voltage rise rate of the wind turbine and the second initial voltage rise rate of the photovoltaic converter are extracted.

[0036] Specifically, the ratio of the rated voltage amplitude to the first initial voltage rise rate is calculated, and this ratio is determined as the first theoretical voltage build-up time of the wind turbine. The ratio of the rated voltage amplitude to the second initial voltage rise rate is calculated, and this ratio is determined as the second theoretical voltage build-up time of the photovoltaic converter. The rated voltage amplitude is denoted as... The first initial voltage rise rate is denoted as The second initial voltage rise rate is denoted as First theory pressure build-up time equal and The ratio of the second theoretical pressure build-up time equal and The ratio of the first theoretical voltage build-up time to the second theoretical voltage build-up time represents the theoretical time span required for a wind turbine and a photovoltaic converter to rise from zero voltage to the rated voltage amplitude under the condition of no time delay correction and maintaining the initial rate of rise.

[0037] Step S222: Perform a difference calculation on the first theoretical voltage build-up time and the second theoretical voltage build-up time to determine the time difference between the wind turbine and the photovoltaic converter reaching the rated voltage. The time difference is used as the reference input for timing decoupling.

[0038] In detail, the difference between the first theoretical pressure build-up time and the second theoretical pressure build-up time is calculated to construct a mathematical model that quantifies the difference in steady-state pressure build-up rate between wind turbines and photovoltaic converters.

[0039] In other words, the absolute value of the difference operation directly reflects the difference in the speed of voltage build-up between the two. The larger the difference, the more significant the speed difference, and the greater the amount of timing shifting required.

[0040] Step S223: The pressure build-up response hysteresis time and the time difference are accumulated to determine the asynchronous excitation time interval between the wind turbine and the photovoltaic converter. The asynchronous excitation time interval covers the difference between dynamic response hysteresis and steady-state pressure build-up rate.

[0041] Furthermore, the occurrence of asynchronous excitation conflict depends not only on the difference in steady-state voltage build-up rate, but also on the influence of the dynamic response hysteresis of the control loop, and the two have an additive effect in the time dimension.

[0042] Specifically, the dynamic hysteresis difference is extracted by calculating the difference between the voltage build-up response hysteresis time of the wind turbine and the photovoltaic converter. This dynamic hysteresis difference is then accumulated with the time difference, and the accumulated result is determined as the asynchronous excitation time interval between the wind turbine and the photovoltaic converter. This asynchronous excitation time interval comprehensively covers the differences in dynamic response hysteresis and steady-state voltage build-up rate throughout the entire process from receiving the command to voltage establishment, characterizing the time span of asynchronous overlap between the actual output voltages of the two devices, thus providing a precise time interval basis for peak-shifting startup.

[0043] Step S224: The asynchronous excitation time interval is used as the voltage build-up start delay and allocated to the device start-up time corresponding to the second initial voltage rise rate, thereby triggering the device corresponding to the second initial voltage rise rate to start the voltage build-up process in advance.

[0044] Furthermore, the asynchronous excitation time interval is used as the pressure build-up start delay, and the allocation object and triggering logic of the delay are determined.

[0045] Furthermore, by comparing the magnitudes of the first and second initial voltage rise rates, devices with slower voltage build-up rates, i.e., devices with smaller initial voltage rise rates, are identified as compensation targets that require early initiation of the voltage build-up process.

[0046] Specifically, the asynchronous excitation time interval is superimposed on the startup time of the device with a smaller initial voltage rise rate, so that the device with a slower voltage build-up rate enters the soft-start voltage build-up process earlier, while the device with a faster voltage build-up rate maintains the original startup time or delays the startup, thereby widening the voltage build-up trajectory of the two on the time axis and avoiding asynchronous excitation conflict between the two during the voltage rise phase.

[0047] Specifically, in this embodiment, the asynchronous excitation time interval is denoted as... The first initial voltage rise rate is denoted as The second initial voltage rise rate is denoted as ,like Less than Then The start-up time allocated to the photovoltaic converter is equal to the initial set start-up time minus... ;like Less than Then The actual start-up time of the wind turbine is equal to the initial set start-up time minus the set start-up time. In other words, by allocating the voltage build-up start-up delay to slower devices, the slower devices can make up for their speed disadvantage by utilizing the time lead, thus laying the timing foundation for reaching the rated voltage at the same time.

[0048] Step S23: Based on the pressure build-up response hysteresis time and time difference, the initial start-up times of the wind turbine and photovoltaic converter are staggered to obtain the pressure build-up start-up delay. The staggered arrangement is used to eliminate the asynchronous excitation conflict caused by the simultaneous pressure build-up of the two.

[0049] Specifically, in this application, the pressure build-up start-up delay calculated based on the pressure build-up response hysteresis time and the time difference is used as an offset to apply to the initial start-up time of one of the devices, so that the wind turbine and the photovoltaic converter no longer start pressure build-up at the same time, but have a deliberately designed timing difference.

[0050] In one alternative implementation, the logic of staggered scheduling is to strictly set the timing difference to cover the voltage build-up start-up delay that encompasses the dynamic and steady-state differences, thereby causing the voltage build-up trajectories of the two to be staggered on the time axis, eliminating the interaction interference between the two during the excitation process. In other words, staggered scheduling achieves timing decoupling, ensuring that, given the objective existence of heterogeneous characteristics between wind turbines and photovoltaic converters, concurrent excitation conflicts are eliminated through peak-shifting scheduling in the time dimension.

[0051] Step S24: Correct the first initial voltage rise rate and the second initial voltage rise rate according to the voltage rise delay to obtain the voltage rise slope of the wind turbine and the photovoltaic converter. The voltage rise slope ensures that both reach the rated voltage amplitude at the same time.

[0052] In order to transform the abstract timing decoupling logic into a voltage rise command that the converter can directly execute, this application provides a mapping rule based on the voltage build-up start-up delay to correct the initial voltage rise rate.

[0053] It is understandable that the voltage rise slope is not a fixed hardware parameter, but a control command parameter that is dynamically calculated based on the timing peak-shaving requirements.

[0054] Specifically, the target synchronous arrival time of the wind turbine and the photovoltaic converter is obtained. This time is equal to the theoretical voltage build-up time of the faster device plus its initial start-up time. Based on the target synchronous arrival time and the actual start-up time with the allocated voltage build-up start-up delay, the required voltage rise rate is recalculated.

[0055] To be more easily understood, the ratio of the rated voltage amplitude to the target voltage build-up time is determined as the corrected voltage rise slope, where the target voltage build-up time is equal to the target synchronous arrival time minus the actual start-up time.

[0056] In this application, the voltage rise slope can be calculated as follows: ; in, This is the corrected voltage rise slope; This is the rated voltage amplitude; To arrive at the target time simultaneously; This refers to the actual start-up time. Through the above mapping rules, the timing staggered peak requirements are transformed into slope adjustment commands, ensuring that the wind turbine and photovoltaic converter perform voltage build-up according to their respective voltage rise slopes, ultimately reaching the rated voltage amplitude precisely at the same time, completing a smooth transition.

[0057] For example, in a black start scenario for an AC microgrid, the rated voltage amplitude of the AC microgrid bus... The first control loop bandwidth of the wind turbine is 311V. The first initial voltage rise rate is 100Hz. The second control loop bandwidth of the photovoltaic converter is 500V / s. The second initial voltage rise rate is 200Hz. The voltage is 300V / s. First, calculate the voltage build-up response hysteresis time and the hysteresis time of the wind turbine. equal The hysteresis time of the photovoltaic converter is 0.01s. equal It is 0.005s. Next, the theoretical pressure build-up time is calculated; the first theoretical pressure build-up time for the wind turbine is... equal The second theoretical voltage build-up time of the photovoltaic converter is 0.622s. equal The value is 1.037s. The time difference is obtained by performing a difference calculation on the theoretical pressure build-up time. equal The absolute value is -0.415s. The difference in pressure build-up response hysteresis is calculated as follows: The value is 0.005s. The asynchronous excitation time interval is obtained by summing the hysteresis difference and the time difference. equal The initial voltage rise rate of the photovoltaic converter (PV converter) is 300V / s, which is less than that of the wind turbine (500V / s). Therefore, the 0.42s voltage build-up delay is allocated to the PV converter. Assuming the original start-up time is 0s, the PV converter starts at -0.42s. Subsequently, the voltage rise rate is adjusted, and the target synchronous arrival time is set to the wind turbine's arrival time of 0.622s. The wind turbine's voltage rise rate is maintained at 500V / s, and the target voltage build-up time for the PV converter is... The time is 1.042s, and the corrected voltage rise slope is... The voltage is approximately 298.5V / s. Ultimately, the wind turbine and photovoltaic converter perform soft start according to the corrected slope and time delay, effectively eliminating concurrent excitation conflicts and ensuring stable voltage establishment.

[0058] Step S3: The voltage build-up delay and voltage rise slope are sent to the corresponding wind turbine and photovoltaic converter to perform soft-start voltage build-up.

[0059] After determining the voltage build-up start-up delay and voltage rise slope, the above control parameters need to be sent to the corresponding physical devices. After receiving the updated instructions, the wind turbine and photovoltaic converter adjust their internal PWM modulation strategies according to the new start-up time and slope, control the switching timing and duty cycle of the power devices, and thus output a voltage waveform that meets the timing decoupling requirements, and execute the soft-start voltage build-up process.

[0060] Step S4: Determine the frequency offset compensation amount based on the phase difference between the output voltages of the wind turbine and the photovoltaic converter, and then add the frequency offset compensation amount to the voltage reference angular frequency of the lagging device.

[0061] Although concurrent excitation conflicts are eliminated through timing stagger, the phase of the output voltage of the wind turbine and the photovoltaic converter may still drift during the dynamic process of soft start voltage build-up, leading to synchronization mismatch. Therefore, it is necessary to actively compensate the frequency according to the phase difference to correct the phase drift and ensure the frequency stability and synchronization of the AC microgrid bus voltage.

[0062] In some embodiments, determining the frequency offset compensation amount based on the phase difference between the output voltages of the wind turbine and the photovoltaic converter, and then superimposing the frequency offset compensation amount onto the voltage reference angular frequency of the lagging device, includes: Step S41: During the soft-start voltage build-up process, the instantaneous amplitude and zero-crossing time of the output voltage of the wind turbine and the photovoltaic converter are obtained. The zero-crossing time is used to extract the real-time phase information of the output voltage of the two.

[0063] Specifically, during the soft-start voltage build-up process, the instantaneous amplitude and zero-crossing time of the output voltage are key attributes characterizing the voltage waveform.

[0064] Among them, the instantaneous amplitude reflects the energy of the voltage at a specific point in time, and its value ranges from 0 to the rated voltage amplitude; the zero crossing moment reflects the time point at which the voltage waveform crosses from the negative polarity to the positive polarity, and its value range is continuously updated as the voltage build-up process progresses.

[0065] It should be noted that both the instantaneous amplitude and the zero-crossing time are obtained by sampling with a high-speed voltage sensor at a sampling rate of no less than 10kHz to ensure the accuracy of phase extraction.

[0066] Step S42: Determine the actual phase difference between the wind turbine output voltage and the photovoltaic converter output voltage based on the zero-crossing time. The actual phase difference characterizes the degree of synchronization misalignment between the two on the AC microgrid bus. The difference in the zero-crossing time of the output voltage of the wind turbine and the photovoltaic converter directly reflects the phase asynchrony between the two. It is necessary to determine the actual phase difference based on the zero-crossing time in order to quantify the degree of synchronization misalignment and guide subsequent compensation operations.

[0067] In some embodiments, determining the actual phase difference between the wind turbine output voltage and the photovoltaic converter output voltage based on the zero-crossing time includes: Step S421: Compare the zero-crossing time of the wind turbine output voltage with the zero-crossing time of the photovoltaic converter output voltage to determine the leading zero-crossing device and the lagging zero-crossing device. The leading zero-crossing device and the lagging zero-crossing device constitute an asymmetric compensation object.

[0068] Preferably, after receiving the zero-crossing moments of the wind turbine and the photovoltaic converter within the same cycle, the leading and lagging relationship is determined by comparing the time sequence.

[0069] In some optional implementations, the zero-crossing time of the wind turbine output voltage is subtracted from the zero-crossing time of the photovoltaic converter output voltage. If the difference is positive, it indicates that the zero-crossing time of the wind turbine is earlier than that of the photovoltaic converter, and the wind turbine is determined to be a leading zero-crossing device and the photovoltaic converter is a lagging zero-crossing device. If the difference is negative, the photovoltaic converter is determined to be a leading zero-crossing device and the wind turbine is a lagging zero-crossing device.

[0070] It is understandable that the leading zero-crossing device and the lagging zero-crossing device together constitute the asymmetric compensation object. That is, the subsequent compensation operation is only performed on the lagging device, rather than adjusting both at the same time. This selection logic avoids the additional oscillations caused by bidirectional adjustment and ensures the uniqueness and certainty of the compensation direction.

[0071] Step S422: Using the output voltage phase of the leading zero-crossing device as the reference phase, determine the electrical angle by which the output voltage phase of the lagging zero-crossing device lags behind the reference phase, and quantify the phase mismatch between heterogeneous converters by the electrical angle.

[0072] Specifically, the output voltage phase of the leading zero-crossing device is set as the zero-degree reference, a unified reference coordinate system is constructed, and the absolute phase of the lagging zero-crossing device is converted into a relative electrical angle deviation.

[0073] In other words, the calculation of the electrical angle abandons the dependence on absolute time scale and uses a relative comparison method to extract the mismatch. In specific implementation, the time difference between the leading zero-crossing time and the lagging zero-crossing time is calculated, and the product of the time difference and the rated electrical angular velocity is determined as the electrical angle.

[0074] In an optional embodiment, the above electrical angle can be calculated as follows: ; In the formula, Electrical degrees, measured in radians; The rated frequency for the AC microgrid; For the time of crossing zero ahead of time; This refers to the time of the zero-crossing with lag. Specifically, the electrical angle... The phase mismatch between heterogeneous converters is quantified. A positive value indicates that the lagging device is behind the reference phase. This value directly maps the physical quantity of synchronization mismatch caused by phase drift on the AC microgrid bus, and serves as the core input basis for frequency offset compensation.

[0075] Step S423: The electrical angle is used as the actual phase difference, and the lag zero-crossing device is identified as the lag device that needs frequency compensation. Frequency compensation is only performed on the lag device to block the additional oscillation excitation path.

[0076] When there is an electrical angle deviation, if the frequency of both the leading and lagging devices is adjusted at the same time, it will cause the frequencies of both devices to fluctuate simultaneously, resulting in system power oscillation.

[0077] If the frequency of the leading equipment is reduced to wait for the lagging equipment, the overall frequency of the AC microgrid will deviate from the rated value, affecting load stability.

[0078] Therefore, it is necessary to execute unidirectional compensation logic based on the existence of electrical angle deviation and the identification results of the lagging device.

[0079] Specifically, the electrical angle is used as the actual phase difference, and the lagging zero-crossing device is locked as the only frequency compensation object. Frequency compensation is only performed on the lagging device, that is, the voltage reference angular frequency of the lagging device is increased to make its phase catch up with the leading device quickly.

[0080] Furthermore, the operation of frequency compensation only for lagging equipment blocks the additional oscillation excitation path, avoids positive feedback oscillation caused by bidirectional adjustment, and ensures that the AC microgrid frequency maintains a unilaterally stable dynamic characteristic during the compensation process.

[0081] Step S424: Based on the ratio of the actual phase difference to the time elapsed during soft-start pressure build-up, determine the frequency offset compensation amount for the lagging equipment. The frequency offset compensation amount is dynamically updated over time to adapt to changes in the pressure build-up trajectory.

[0082] This application relates to the precise calculation of frequency offset compensation. It should be noted that the phase deviation accumulates gradually during the voltage build-up dynamic process. Therefore, the compensation amount must be related to the time process. If a fixed compensation amount is used, overcompensation may occur in the initial stage, causing overshoot, and undercompensation may occur in the final stage, leading to steady-state error.

[0083] In detail, the actual phase difference at the current moment and the time elapsed from the start of soft-start voltage build-up to the current moment are extracted, and the ratio of the actual phase difference to the time elapsed is calculated. This ratio represents the rate of phase change that needs to be compensated per unit time, i.e., the frequency offset.

[0084] In one implementation, the aforementioned frequency offset compensation amount can be obtained through the following specific calculation method: ; In the formula, This is the frequency offset compensation amount; The current actual phase difference, in radians; This refers to the time elapsed during soft-start voltage build-up. In other words, it represents the frequency offset compensation amount. It updates dynamically over time to adapt to changes in the pressure build-up trajectory. In the initial stage, when the time length is short but the phase difference has not accumulated to a large extent, it provides reasonable compensation to start. In the later stage, when the phase difference shrinks and the time length increases, it automatically attenuates the compensation amount to prevent overcompensation.

[0085] Step S43: Integrate the actual phase difference on the time axis to determine the cumulative phase deviation between the wind turbine and the photovoltaic converter. The cumulative phase deviation reflects the cumulative effect of phase drift during dynamic voltage build-up.

[0086] In a preferred implementation, the instantaneous value of the actual phase difference is integrated on the time axis to obtain an index reflecting the total phase drift during the entire pressure build-up period.

[0087] Specifically, in this embodiment, the actual phase difference is continuously integrated using an integrator, and the integration result is the cumulative phase deviation. The cumulative phase deviation not only includes the current instantaneous phase mismatch but also covers the superposition of historical drift, reflecting the cumulative effect of phase drift during dynamic voltage build-up.

[0088] It should be noted that the cumulative phase deviation eliminates the interference of instantaneous measurement noise, extracts the monotonic trend term of phase drift, provides a more stable control input basis for subsequent frequency compensation, and avoids the controller from over-responding to transient fluctuations.

[0089] Step S45: Convert the accumulated phase deviation into a frequency offset compensation amount, and add the frequency offset compensation amount to the voltage reference angular frequency of the lagging device to adjust the voltage reference angular frequency of the lagging device to offset the accumulated phase deviation.

[0090] In some optional implementations, the logic of converting the accumulated phase deviation into a frequency offset compensation amount is based on the calculus relationship between frequency and phase. The accumulation of phase deviation is essentially caused by frequency offset, so eliminating the accumulated phase deviation requires frequency adjustment.

[0091] In other words, choosing the cumulative phase deviation as the basis for frequency compensation eliminates the controller jitter that may be caused by using the instantaneous phase difference as a reference, because the instantaneous phase difference contains high-frequency components.

[0092] Specifically, the accumulated phase deviation is multiplied by the gain parameter of the proportional-integral controller to convert it into a frequency offset compensation amount. According to the embodiments of this application, the frequency offset compensation amount is superimposed on the voltage reference angular frequency of the lagging device, adjusting the voltage reference angular frequency of the lagging device so that the output voltage frequency of the lagging device is slightly higher than the rated frequency for a short period of time, thereby quickly offsetting the accumulated phase deviation and achieving precise phase tracking and synchronization.

[0093] For example, in an AC microgrid voltage construction scenario, the rated frequency is 50Hz, the wind turbine is a leading zero-crossing device, and the photovoltaic converter is a lagging zero-crossing device. Within a certain calculation cycle, the zero-crossing time of the wind turbine output voltage is obtained as 0.02005s, and the zero-crossing time of the photovoltaic converter output voltage is obtained as 0.02015s, with a time difference of 0.0001s. The electrical angle is then calculated. equal Approximately 0.0314 radians. Since the photovoltaic converter is a lagging device, 0.0314 radians is used as the actual phase difference, and frequency compensation is only applied to the photovoltaic converter. The current soft-start voltage build-up time is set. Calculate the frequency offset compensation amount for a time interval of 0.5s. equal The frequency is 0.0628Hz. This 0.0628Hz is superimposed on the voltage reference angular frequency of the photovoltaic converter, meaning the reference angular frequency starts from... Adjusted to This prompts the photovoltaic converter to catch up with the phase. If a phase jump occurs, the actual phase difference changes abruptly by 3.5 radians, which is greater than... Then subtract the accumulated phase deviation. The compensation amount was calculated after correcting it to 0.7168 radians, effectively avoiding reverse compensation. Through the above operations, active suppression and precise compensation of phase drift were achieved.

[0094] Step S5: Adjust the voltage amplitude reference of the corresponding wind turbine and photovoltaic converter according to the circulating reactive component on the AC microgrid bus.

[0095] In addition to phase drift, the mismatch in output voltage amplitude between wind turbines and photovoltaic converters will generate circulating reactive components on the AC microgrid bus, resulting in voltage waveform distortion and reactive power loss. Therefore, it is necessary to extract the circulating reactive components and adjust the voltage amplitude reference accordingly to actively suppress the circulating current and ensure voltage quality.

[0096] In some embodiments, adjusting the voltage amplitude reference of the corresponding wind turbine and photovoltaic converter based on the circulating reactive power component on the AC microgrid bus includes: Step S51: Obtain the three-phase instantaneous current and three-phase instantaneous voltage on the AC microgrid bus, transform the three-phase instantaneous current and three-phase instantaneous voltage to an orthogonal rotating coordinate system, and decouple the active and reactive components in the orthogonal rotating coordinate system.

[0097] The AC quantities in the three-phase stationary coordinate system are converted into DC quantities in the orthogonal rotating coordinate system. Further, the three-phase instantaneous current and voltage on the AC microgrid bus are acquired. A Clarke transform is performed on the three-phase instantaneous current and voltage to convert the three-phase stationary coordinate system into a two-phase stationary coordinate system. Then, a Park transform is performed to convert the two-phase stationary coordinate system into an orthogonal rotating coordinate system that rotates synchronously with the grid's angular frequency. Specifically, in the orthogonal rotating coordinate system, the AC quantities are decoupled into active and reactive components. The active component corresponds to the d-axis component, representing the flow of active power; the reactive component corresponds to the q-axis component, representing the exchange of reactive power. In other words, through the orthogonal rotating coordinate system transformation, complex AC signal processing is transformed into simple DC signal control, providing a standard orthogonal decoupled data source for the accurate extraction of the circulating reactive component.

[0098] Step S52: In the orthogonal rotating coordinate system, extract the reactive current component on the AC microgrid bus as the circulating reactive component. The circulating reactive component directly reflects the degree of voltage amplitude mismatch between heterogeneous converters.

[0099] The reactive current component on the AC microgrid bus is a direct manifestation of voltage amplitude mismatch between heterogeneous converters, and this component must be accurately extracted as a feedback signal for circulating current suppression.

[0100] In some embodiments, extracting the reactive current component from the AC microgrid bus as the circulating reactive component in an orthogonal rotating coordinate system includes: Step S521: Obtain the active power and reactive power of the wind turbine and photovoltaic converter in the orthogonal rotating coordinate system. The active power and reactive power are calculated from their respective output current and voltage coordinate components.

[0101] This application relates to the calculation of power characteristics, meaning that the assessment of the system's reactive power state must be based on a minimal set of information. It should be noted that missing active power will prevent the distinction between reactive power consumed by the load and reactive power consumed by circulating current; conversely, missing reactive power will prevent the direct quantification of circulating current magnitude. Specifically, the d-axis output current, q-axis output current, d-axis output voltage, and q-axis output voltage of the wind turbine are obtained in an orthogonal rotating coordinate system. Using the power calculation formula, the product of the d-axis output voltage and the q-axis output current, plus the product of the q-axis output voltage and the d-axis output current, is used to determine the reactive power of the wind turbine. Similarly, the reactive power of the photovoltaic converter is calculated. In some embodiments, the reactive power of the wind turbine is denoted as... The reactive power of the photovoltaic converter is denoted as Both are calculated from their respective output current and voltage coordinate components using instantaneous power theory, ensuring the real-time nature and accuracy of the calculation results.

[0102] Step S522: In the orthogonal rotating coordinate system, the reactive current component on the AC microgrid bus is extracted as the circulating reactive component. The circulating reactive component directly reflects the degree of voltage amplitude mismatch between heterogeneous converters.

[0103] Specifically, the circulating reactive power component, as a key indicator of the degree of voltage amplitude mismatch between heterogeneous converters, is derived from calculations based on the difference in reactive power between wind turbines and photovoltaic converters. It should be noted that the physical meaning of the circulating reactive power component lies in characterizing the reactive current flowing between the two due to unequal voltage amplitudes; this current does not perform external work but only circulates internally. In one embodiment, the reactive power difference value is denoted as... ,Will Dividing by the rated voltage amplitude of the AC microgrid bus yields the circulating reactive power component. In other words, the larger the value of the circulating reactive power component, the greater the difference in output voltage amplitude between the wind turbine and the photovoltaic converter, and the greater the amplitude compensation adjustment required. Specifically, using the circulating reactive power component as a feedback variable for amplitude adjustment achieves a mapping from the power domain to the current domain, allowing the controller's input to directly reflect the actual circulating current state at the electrical physical connection points, thus improving the targeted nature of the control response.

[0104] Step S523: Calculate the difference between the reactive power of the wind turbine and the reactive power of the photovoltaic converter, and extract the reactive power difference value. The reactive power difference value represents the imbalance between the two in terms of reactive power support.

[0105] In this application, the calculation process of reactive power difference is encapsulated into a power domain differential module. In other words, the system backend automatically encapsulates and hides the complex internal coordinate component multiplication and addition / subtraction logic, simplifying the input operation of the front-end reactive power regulation. Accordingly, the backend receives reactive power data from the wind turbine and photovoltaic converter in an orthogonal rotating coordinate system, automatically performs subtraction, subtracting the reactive power of the photovoltaic converter from the reactive power of the wind turbine, and outputs the reactive power difference value. It should be noted that the reactive power difference value characterizes the imbalance in reactive power support between the two; a positive value indicates that the wind turbine generates more reactive power than the photovoltaic converter, and a negative value indicates the opposite. Understandably, through automated encapsulation, external calls only need to focus on the polarity and magnitude of the difference value, without needing to intervene in the underlying voltage and current cross-product operations, reducing the design complexity of the control logic.

[0106] Step S524: Divide the reactive power difference value by the rated voltage amplitude of the AC microgrid bus to obtain the circulating reactive component. The conversion process maps the power domain difference to the current domain characteristics.

[0107] In some instances, to eliminate uncertainties in the mapping of power domain differences to current domain characteristics and ensure predictable circulating reactive power components even under microgrid voltage fluctuations, a standardized conversion mechanism based on the rated voltage amplitude was designed. It's important to understand that actual voltage fluctuations can lead to unstable power-to-current conversion ratios; therefore, a constant rated voltage amplitude is used as the denominator. In other words, the reactive power difference is divided by the rated voltage amplitude of the AC microgrid bus to obtain the circulating reactive power component, eliminating the impact of transient voltage fluctuations on the circulating current calculation. It should be noted that low-pass filtering is applied to the circulating reactive power component to remove high-frequency switching harmonic interference, resulting in a smooth circulating reactive power component and blocking high-frequency noise from entering the controller. Through standardized conversion and filtering, the stability and predictability of the circulating reactive power component are ensured, laying the foundation for generating reliable reactive power adjustment commands.

[0108] Step S53: Compare the circulating reactive component with the reactive power allowable fluctuation threshold. In response to the circulating reactive component exceeding the reactive power allowable fluctuation threshold, generate a reactive power adjustment command. The reactive power allowable fluctuation threshold defines the boundary between normal operation and abnormal circulating current.

[0109] In a preferred implementation, the criteria for determining whether a condition is met are clearly defined, i.e., the basis for setting the reactive power allowable fluctuation threshold. Specifically, in this embodiment, the reactive power allowable fluctuation threshold is set based on the reactive power demand of the load carried by the AC microgrid bus and the rated capacity of the converter, typically set to 5% of the converter's rated reactive power capacity. Further, the absolute value of the circulating reactive power component is compared with the reactive power allowable fluctuation threshold. If the absolute value of the circulating reactive power component is greater than the threshold, the circulating current is determined to be in an abnormal state, and a reactive power adjustment command is generated. If the absolute value of the circulating reactive power component is less than or equal to the threshold, the circulating current is determined to be within the normal operating range, and no reactive power adjustment command is generated. In other words, the reactive power allowable fluctuation threshold strictly defines the boundary between normal operation and abnormal circulating current, avoiding frequent triggering of adjustments within the normal fluctuation range and ensuring the stability of the control system.

[0110] Step S54: Convert the reactive power adjustment command into a voltage amplitude compensation amount and add it to the voltage amplitude reference of the wind turbine and photovoltaic converter to modify the command source to offset the circulating reactive power component.

[0111] After the reactive power adjustment command is generated, it needs to be converted into a specific voltage amplitude compensation amount and superimposed on the control source of the converter. By adjusting the voltage reference value, the output voltage amplitude is changed, thereby actively offsetting the circulating reactive power component.

[0112] like Figure 2 As shown, the step of converting the reactive power adjustment command into a voltage amplitude compensation amount and adding it to the voltage amplitude reference of the wind turbine and photovoltaic converter includes: Step S541: Determine the surplus or shortage state of reactive power on the AC microgrid bus based on the positive and negative polarities of the circulating reactive power components. The surplus or shortage state of reactive power indicates the direction of circulating current flow and the strength of voltage support.

[0113] In a preferred implementation, the general rules for polarity determination and state mapping are followed, meaning the positive or negative polarity of the circulating reactive power component directly corresponds to the surplus or deficit of reactive power. It should be noted that when the circulating reactive power component is positive, it indicates that the wind turbine is injecting reactive power into the photovoltaic converter, resulting in a reactive power surplus on the photovoltaic converter side; when it is negative, it indicates reverse flow. Understandably, under certain extreme operating conditions, the polarity may fluctuate at high frequencies. In such cases, hysteresis comparison logic is introduced as a special case. Specifically, a hysteresis width is set. When the circulating reactive power component falls from positive polarity into the hysteresis width, the original positive polarity determination is maintained until it falls below zero, at which point it flips to a negative polarity determination. This ensures the stability of the state mapping and avoids adjustment oscillations caused by frequent switching near zero.

[0114] Step S542: Based on the surplus or shortage of reactive power, the voltage amplitude compensation is divided into a first amplitude compensation for the corresponding wind turbine and a second amplitude compensation for the corresponding photovoltaic converter. The first amplitude compensation and the second amplitude compensation have an inverse adjustment characteristic.

[0115] like Figure 3 As shown, when reactive power is in excess, the voltage amplitude on that side needs to be reduced to decrease reactive power output, while the voltage amplitude on the opposite side needs to be increased to absorb reactive power. When reactive power is in deficit, the operation is reversed. If both are adjusted in the same direction, circulating current cannot be eliminated; if only one side is adjusted, the overall voltage level of the microgrid will deviate from the rated value. Therefore, branch assignment operation needs to be performed based on the reactive power surplus / deficit state. Specifically, when it is determined that there is reactive power surplus on the wind turbine side, the first amplitude compensation amount of the corresponding wind turbine is set to a negative value, and the second amplitude compensation amount of the corresponding photovoltaic converter is set to a positive value, with their absolute values ​​being equal; when it is determined that there is reactive power deficit on the wind turbine side, the first amplitude compensation amount is set to a positive value, and the second amplitude compensation amount is set to a negative value. Furthermore, the first amplitude compensation amount and the second amplitude compensation amount have an inverse adjustment characteristic, ensuring that the balance of the overall voltage amplitude of the AC microgrid bus is maintained while eliminating circulating current.

[0116] Step S543: Add the first amplitude compensation amount to the initial voltage amplitude reference of the wind turbine, and add the second amplitude compensation amount to the initial voltage amplitude reference of the photovoltaic converter. The addition operation is performed before the voltage closed-loop control.

[0117] In this embodiment, after obtaining the first and second amplitude compensation values, the compensation values ​​are strictly superimposed onto the reference command according to the timing sequence to ensure the continuity and coherence between actions. Accordingly, the first amplitude compensation value is added to the initial voltage amplitude reference of the wind turbine, and the second amplitude compensation value is added to the initial voltage amplitude reference of the photovoltaic converter. Specifically, the addition operation is performed before voltage closed-loop control; that is, the updated voltage amplitude reference is used as the input setpoint for the closed-loop controller. The closed-loop controller adjusts the PWM modulation wave according to the new setpoint, thereby controlling the switching state of the power devices. In detail, by intervening in compensation before closed-loop control, the high gain and fast response characteristics of the closed-loop controller are utilized, enabling the amplitude compensation command to be accurately tracked and executed, ensuring the dynamic performance of circulating current suppression.

[0118] Step S544: The summed result is used as the updated voltage amplitude reference and sent to the corresponding wind turbine and photovoltaic converter to perform voltage closed-loop control and correct the AC microgrid bus voltage to match the rated value.

[0119] In this embodiment, before the adjustment operation, the voltage amplitude references for the wind turbine and photovoltaic converter are initial settings. Due to heterogeneous characteristics, the actual output voltage amplitude deviates, resulting in a large circulating reactive component on the AC microgrid bus, causing the bus voltage to deviate from the rated value. After the adjustment operation, the updated voltage amplitude reference includes compensation, and the closed-loop control output changes accordingly. The difference in actual output voltage amplitude is reduced, the circulating reactive component is canceled out, and the bus voltage comes close to the rated value. In other words, by comparing the system states before and after the adjustment, the updated voltage amplitude reference directly corrects the converter's output behavior, eliminating the original deviation. Accordingly, the updated voltage amplitude reference is sent to the corresponding wind turbine and photovoltaic converter to perform voltage closed-loop control. The controller adjusts the reactive component in the output current to change the output voltage amplitude, stabilizing the AC microgrid bus voltage near the rated value, thus effectively suppressing circulating current and improving voltage quality. In some optional implementations, the proportional gain parameter of the closed-loop controller is set according to the circulating current attenuation rate requirement to ensure that the circulating current reactive component is suppressed to within the allowable fluctuation threshold within 3 power frequency cycles.

[0120] For example, in a wind-solar hybrid zero-carbon system, the rated voltage of the AC microgrid bus is 311V, the reactive power output of the wind turbine is 1000Var, and the reactive power output of the photovoltaic converter is 600Var, resulting in a reactive power difference of 400Var. Dividing 400Var by 311V yields a circulating reactive power component of approximately 1.286A. A reactive power fluctuation threshold of 0.5A is set. Since 1.286A is greater than 0.5A, a reactive power adjustment command is generated. Based on polarity determination, the wind turbine side has excess reactive power, so the first amplitude compensation is set to -5V, and the second amplitude compensation is set to +5V. The initial voltage amplitude reference of the wind turbine (311V) is added to -5V, resulting in an updated reference of 306V; the initial reference of the photovoltaic converter (311V) is added to +5V, resulting in an updated reference of 316V. After the closed-loop control is executed, the wind turbine reduces reactive power output, the photovoltaic converter increases reactive power output, the circulating current decreases rapidly, and the bus voltage is maintained near the rated value of 311V, effectively solving the circulating current problem caused by amplitude mismatch.

[0121] In some embodiments, the step of adjusting the voltage amplitude reference of the corresponding wind turbine and photovoltaic converter based on the circulating reactive power component on the AC microgrid bus further includes: Step S6: Obtain the fundamental component and total harmonic component of the AC microgrid bus voltage. Determine the ratio of the total harmonic component to the fundamental component as the voltage distortion rate. The voltage distortion rate characterizes the degree to which the AC microgrid bus voltage deviates from the sine wave.

[0122] To transform the abstract degree of voltage distortion into a concrete and calculable technical indicator, this application provides a voltage distortion rate calculation method based on frequency domain decomposition to address the difficulty in quantifying voltage waveform quality. Furthermore, using a Fast Fourier Transform algorithm, the time-domain sampled signal of the AC microgrid bus voltage is decomposed into the frequency domain. The voltage component corresponding to the fundamental frequency is extracted as the fundamental component, and the absolute value of the sum of all high-frequency components other than the fundamental component is taken as the total harmonic component. It is easily understood that the ratio of the total harmonic component to the fundamental component is determined as the voltage distortion rate. According to the embodiments of this application, the voltage distortion rate... It can be calculated in the following way: ; In the formula, For total harmonic components; This refers to the fundamental frequency component. The voltage distortion rate directly characterizes the degree to which the AC microgrid bus voltage deviates from a sine wave. A higher value indicates more severe distortion, providing a precise quantitative basis for subsequent judgment on whether frequency and amplitude fine-tuning is necessary.

[0123] Step S7: Compare the voltage distortion rate with the voltage distortion threshold. If the voltage distortion rate is greater than the voltage distortion threshold, generate a frequency fine-tuning command and an amplitude fine-tuning command. The voltage distortion threshold distinguishes between normal operation and distortion oscillation state.

[0124] In a preferred embodiment, the criteria for determining success or failure of the execution step are clearly defined. It should be noted that the voltage distortion threshold is set based on the load's tolerance to power quality, typically set to 5%. Specifically, in this embodiment, the real-time calculated voltage distortion rate is compared with the 5% threshold. If the voltage distortion rate is greater than 5%, it is determined to be a distortion oscillation state, which is an execution failure state, requiring the generation of frequency and amplitude fine-tuning commands to trigger active damping. If the voltage distortion rate is less than or equal to 5%, it is determined to be a normal operating state, which is an execution success state, and no fine-tuning command is generated. That is, the voltage distortion threshold strictly distinguishes between normal operation and distortion oscillation states, ensuring that fine-tuning commands only intervene when the waveform is severely distorted, avoiding excessive intervention in the system's steady-state operation.

[0125] Step S8: The frequency fine-tuning command is superimposed on the voltage reference angular frequency of the wind turbine and photovoltaic converter to adjust the zero-crossing time of the output voltage of the wind turbine and photovoltaic converter, thereby changing the excitation period of the low-frequency oscillation.

[0126] Preferably, when fine-tuning is required, a unique output command, namely a frequency fine-tuning command, needs to be selected and locked from multiple candidate adjustment parameters. In some optional specific embodiments, the generation logic of the frequency fine-tuning command is based on the principle of disrupting the synchronization of low-frequency oscillations, that is, changing the oscillation period through a small frequency offset. It is understood that if only one side of the frequency is adjusted, it may cause a new phase loss of synchronization. Therefore, the frequency fine-tuning command is simultaneously superimposed on the voltage reference angular frequency of the wind turbine and the photovoltaic converter, and the command signs are opposite, so that the frequency on one side increases slightly and the frequency on the other side decreases slightly. In other words, according to the embodiments of this application, the frequency fine-tuning command is superimposed on the voltage reference angular frequency, adjusting the zero-crossing time of the output voltage, changing the excitation period of the low-frequency oscillation, thereby breaking the original oscillation positive feedback mechanism and achieving rapid suppression of low-frequency oscillations.

[0127] Step S9: The amplitude fine-tuning command is superimposed on the voltage amplitude reference of the wind turbine and photovoltaic converter to adjust the peak and trough deviation of the AC microgrid bus voltage and reduce the amplitude of the active and reactive circulating current components.

[0128] In some embodiments, the execution of amplitude fine-tuning commands follows the difference elimination rules under general technical scenarios. For example, when the AC microgrid bus voltage exhibits distortion with excessively high peaks or excessively low troughs, the conventional approach is to smooth out amplitude fluctuations by adjusting reactive power output. Specifically, in this embodiment, amplitude fine-tuning commands are superimposed on the voltage amplitude references of the wind turbine and photovoltaic converter. Based on the deviation direction of the peaks and troughs, the voltage amplitude references are corrected; if the peaks are too high, the amplitude reference is reduced; if the troughs are too low, the amplitude reference is increased. Furthermore, through the intervention of amplitude fine-tuning commands, the peak and trough deviations of the AC microgrid bus voltage are adjusted, reducing the amplitude of the active and reactive circulating current components, thereby damping oscillations in the amplitude dimension. Combined with frequency fine-tuning commands, this achieves dual active suppression of voltage distortion and low-frequency oscillations.

[0129] For example, in the later stages of black start in a wind-solar hybrid zero-carbon system, the AC microgrid bus voltage exhibits low-frequency oscillations and distortion. The AC microgrid bus voltage signal is acquired, and the fundamental component is obtained through FFT decomposition. 310V, total harmonic component Calculate the voltage distortion rate for a voltage of 25V. for The voltage distortion rate was approximately 8.06%. Since 8.06% exceeded the 5% voltage distortion threshold, the system was determined to be in a distorted oscillation state, generating frequency and amplitude fine-tuning commands. The frequency fine-tuning command was superimposed on the reference angular frequency, increasing the wind turbine's angular frequency by 0.2 rad / s and decreasing the photovoltaic converter's angular frequency by 0.2 rad / s. This altered the excitation period of the low-frequency oscillation, causing the phase difference between their output voltages to break down. Simultaneously, a high voltage peak was detected, so the amplitude fine-tuning command was superimposed on the voltage amplitude reference, decreasing both the wind turbine and photovoltaic converter's amplitude references by 2V, reducing the circulating current component amplitude. After several cycles of adjustment, the total harmonic component decreased to 10V, and the voltage distortion rate dropped to 3.2%, below the threshold, allowing the system to return to normal operation.

[0130] This embodiment also provides a zero-carbon power supply system based on wind-solar hybridization, including: The feature acquisition module is used to acquire the first control loop bandwidth and the first initial voltage rise rate of the wind turbine generator and the second control loop bandwidth and the second initial voltage rise rate of the photovoltaic converter. The timing slope determination module is used to determine the voltage rise delay and voltage rise slope of the wind turbine and photovoltaic converter based on the first control loop bandwidth, the first initial voltage rise rate, the second control loop bandwidth and the second initial voltage rise rate. The voltage build-up control module is used to send the voltage build-up start-up delay and voltage rise slope to the corresponding wind turbine and photovoltaic converter to perform soft start voltage build-up; The phase compensation module is used to determine the frequency offset compensation amount based on the phase difference between the output voltage of the wind turbine and the photovoltaic converter, and to superimpose the frequency offset compensation amount onto the voltage reference angular frequency of the lagging device. The amplitude adjustment module is used to adjust the voltage amplitude reference of the corresponding wind turbine and photovoltaic converter based on the circulating reactive component on the AC microgrid bus.

[0131] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A zero-carbon power supply method based on wind-solar hybridization, characterized in that, include: The bandwidth of the first control loop of the wind turbine and the first initial voltage rise rate are obtained, as well as the bandwidth of the second control loop of the photovoltaic converter and the second initial voltage rise rate. Based on the first control loop bandwidth, the first initial voltage rise rate, the second control loop bandwidth, and the second initial voltage rise rate, the voltage build-up start-up delay and voltage rise slope of the wind turbine and photovoltaic converter are determined. The voltage build-up delay and voltage rise slope are sent to the corresponding wind turbines and photovoltaic converters to perform soft-start voltage build-up. The frequency offset compensation amount is determined based on the phase difference between the output voltages of the wind turbine and the photovoltaic converter, and then the frequency offset compensation amount is superimposed on the voltage reference angular frequency of the lagging device. Adjust the voltage amplitude reference of the corresponding wind turbine and photovoltaic converter based on the circulating reactive component on the AC microgrid bus.

2. The zero-carbon power supply method based on wind-solar hybridization as described in claim 1, characterized in that: The determination of the voltage rise delay and voltage ramp of the wind turbine and photovoltaic converter based on the first control loop bandwidth, the first initial voltage rise rate, the second control loop bandwidth, and the second initial voltage rise rate includes: Based on the reciprocal relationship between the bandwidth of the first control loop and the bandwidth of the second control loop, the voltage build-up response hysteresis time of the wind turbine and the photovoltaic converter are determined respectively. The voltage build-up response hysteresis time characterizes the delay characteristics of the converter in responding to the voltage command. The first initial voltage rise rate is compared with the second initial voltage rise rate to determine the time difference between the wind turbine and the photovoltaic converter reaching the rated voltage. Based on the pressure build-up response hysteresis time and time difference, the initial startup times of wind turbines and photovoltaic converters are staggered to obtain the pressure build-up startup delay. The voltage rise slopes of the wind turbine and photovoltaic converter are obtained by correcting the first and second initial voltage rise rates based on the voltage rise delay during the start-up phase.

3. The zero-carbon power supply method based on wind-solar hybridization as described in claim 2, characterized in that: The step of comparing the first initial voltage rise rate with the second initial voltage rise rate to determine the time difference between the wind turbine and the photovoltaic converter reaching the rated voltage includes: Obtain the rated voltage amplitude of the AC microgrid bus, and divide the rated voltage amplitude by the first initial voltage rise rate and the second initial voltage rise rate respectively to determine the first theoretical voltage build-up time and the second theoretical voltage build-up time; The time difference between the first theoretical voltage build-up time and the second theoretical voltage build-up time is calculated to determine the time difference between the wind turbine and the photovoltaic converter reaching the rated voltage. The asynchronous excitation time interval between the wind turbine and the photovoltaic converter is determined by summing the pressure build-up response hysteresis time and the time difference. The asynchronous excitation time interval covers the difference between dynamic response hysteresis and steady-state pressure build-up rate. The asynchronous excitation time interval is used as the voltage build-up start delay and allocated to the device start-up time corresponding to the second initial voltage rise rate, thereby triggering the device corresponding to the second initial voltage rise rate to start the voltage build-up process in advance.

4. The zero-carbon power supply method based on wind-solar hybridization as described in claim 1, characterized in that: The step of determining the frequency offset compensation amount based on the phase difference between the output voltages of the wind turbine and the photovoltaic converter, and then superimposing the frequency offset compensation amount onto the voltage reference angular frequency of the lagging device, includes: During the soft-start voltage build-up process, the instantaneous amplitude and zero-crossing time of the output voltage of the wind turbine and photovoltaic converter are obtained; The actual phase difference between the wind turbine output voltage and the photovoltaic converter output voltage is determined based on the zero-crossing time. The actual phase difference is integrated on the time axis to determine the cumulative phase deviation between the wind turbine and the photovoltaic converter. The cumulative phase deviation reflects the cumulative effect of phase drift during the dynamic voltage build-up process. The accumulated phase deviation is converted into a frequency offset compensation amount, and the frequency offset compensation amount is superimposed on the voltage reference angular frequency of the lagging device. The voltage reference angular frequency of the lagging device is then adjusted to offset the accumulated phase deviation.

5. The zero-carbon power supply method based on wind-solar hybridization as described in claim 4, characterized in that: The determination of the actual phase difference between the wind turbine output voltage and the photovoltaic converter output voltage based on the zero-crossing time includes: By comparing the zero-crossing time of the wind turbine output voltage with the zero-crossing time of the photovoltaic converter output voltage, the leading zero-crossing device and the lagging zero-crossing device are identified. The leading zero-crossing device and the lagging zero-crossing device constitute an asymmetric compensation object. Using the output voltage phase of the leading zero-crossing device as the reference phase, the electrical angle by which the output voltage phase of the lagging zero-crossing device lags behind the reference phase is determined, and the electrical angle is used to quantify the phase mismatch between heterogeneous converters. The electrical angle is taken as the actual phase difference, and the lagging zero-crossing device is identified as the lagging device that needs frequency compensation. Frequency compensation is only performed on the lagging device to block the additional oscillation excitation path. The frequency offset compensation amount of the lagging equipment is determined based on the ratio of the actual phase difference to the time elapsed during soft start-up pressure build-up. The frequency offset compensation amount is dynamically updated over time to adapt to changes in the pressure build-up trajectory.

6. The zero-carbon power supply method based on wind-solar hybridization as described in claim 1, characterized in that: The adjustment of the voltage amplitude reference for the corresponding wind turbine and photovoltaic converter based on the circulating reactive power component on the AC microgrid bus includes: The three-phase instantaneous current and three-phase instantaneous voltage on the AC microgrid bus are obtained, and the three-phase instantaneous current and three-phase instantaneous voltage are transformed into an orthogonal rotating coordinate system. The orthogonal rotating coordinate system decouples the active and reactive components. In an orthogonal rotating coordinate system, the reactive current component on the AC microgrid bus is extracted as the circulating reactive component, which directly reflects the degree of voltage amplitude mismatch between heterogeneous converters. The circulating reactive component is compared with the reactive power allowable fluctuation threshold. In response to the circulating reactive component exceeding the reactive power allowable fluctuation threshold, a reactive power adjustment command is generated. The reactive power allowable fluctuation threshold defines the boundary between normal operation and abnormal circulating current. The reactive power adjustment command is converted into a voltage amplitude compensation amount and superimposed on the voltage amplitude reference of the wind turbine and photovoltaic converter, thereby modifying the source of the command to offset the circulating reactive power component.

7. The zero-carbon power supply method based on wind-solar hybridization as described in claim 6, characterized in that: The process of converting reactive power adjustment commands into voltage amplitude compensation amounts and adding them to the voltage amplitude references of wind turbines and photovoltaic converters includes: Based on the positive and negative polarities of the circulating reactive power components, the surplus or shortage state of reactive power on the AC microgrid bus is determined. The surplus or shortage state of reactive power indicates the direction of circulating current flow and the strength of voltage support. Based on the surplus and shortage of reactive power, the voltage amplitude compensation is divided into the first amplitude compensation corresponding to the wind turbine and the second amplitude compensation corresponding to the photovoltaic converter. The first amplitude compensation and the second amplitude compensation have opposite adjustment characteristics. The first amplitude compensation amount is added to the initial voltage amplitude reference of the wind turbine, and the second amplitude compensation amount is added to the initial voltage amplitude reference of the photovoltaic converter. The addition operation is performed before the voltage closed-loop control. The summed result is used as the updated voltage amplitude reference and sent to the corresponding wind turbine and photovoltaic converter to perform voltage closed-loop control, correcting the AC microgrid bus voltage to match the rated value.

8. The zero-carbon power supply method based on wind-solar hybridization as described in claim 6, characterized in that: The step of extracting the reactive current component from the AC microgrid bus as the circulating reactive component in an orthogonal rotating coordinate system includes: The active power and reactive power of the wind turbine and photovoltaic converter in the orthogonal rotating coordinate system are obtained. The active power and reactive power are calculated from their respective output current and voltage coordinate components. The reactive power difference between the wind turbine generator and the photovoltaic converter is calculated, and the reactive power difference value is extracted. The reactive power difference is divided by the rated voltage amplitude of the AC microgrid bus to obtain the circulating reactive component. The conversion process maps the power domain difference to the current domain characteristics. The circulating reactive component is low-pass filtered to remove high-frequency switching harmonic interference, resulting in a smooth circulating reactive component used to generate reactive power adjustment commands. The smooth circulating reactive component also blocks high-frequency noise from entering the controller.

9. The zero-carbon power supply method based on wind-solar hybridization as described in claim 6, characterized in that: Before adjusting the voltage amplitude reference of the corresponding wind turbine and photovoltaic converter based on the circulating reactive power component on the AC microgrid bus, the following steps are also included: The fundamental component and total harmonic component of the AC microgrid bus voltage are obtained, and the ratio of the total harmonic component to the fundamental component is determined as the voltage distortion rate. The voltage distortion rate characterizes the degree to which the AC microgrid bus voltage deviates from the sine wave. The voltage distortion rate is compared with the voltage distortion threshold. In response to the voltage distortion rate being greater than the voltage distortion threshold, frequency fine-tuning command and amplitude fine-tuning command are generated. The voltage distortion threshold distinguishes between normal operation and distortion oscillation state. The frequency fine-tuning command is superimposed on the voltage reference angular frequency of the wind turbine and photovoltaic converter to adjust the zero-crossing time of the output voltage of the wind turbine and photovoltaic converter, thereby changing the excitation period of the low-frequency oscillation. The amplitude fine-tuning command is superimposed on the voltage amplitude reference of the wind turbine and photovoltaic converter to adjust the peak and trough deviation of the AC microgrid bus voltage and reduce the amplitude of the active and reactive circulating current components.

10. A zero-carbon power supply system based on wind-solar hybridization, employing the zero-carbon power supply method based on wind-solar hybridization as described in any one of claims 1 to 9, characterized in that, include: The feature acquisition module is used to acquire the first control loop bandwidth and the first initial voltage rise rate of the wind turbine generator and the second control loop bandwidth and the second initial voltage rise rate of the photovoltaic converter. The timing slope determination module is used to determine the voltage rise delay and voltage rise slope of the wind turbine and photovoltaic converter based on the first control loop bandwidth, the first initial voltage rise rate, the second control loop bandwidth and the second initial voltage rise rate. The voltage build-up control module is used to send the voltage build-up start-up delay and voltage rise slope to the corresponding wind turbine and photovoltaic converter to perform soft start voltage build-up; The phase compensation module is used to determine the frequency offset compensation amount based on the phase difference between the output voltage of the wind turbine and the photovoltaic converter, and to superimpose the frequency offset compensation amount onto the voltage reference angular frequency of the lagging device. The amplitude adjustment module is used to adjust the voltage amplitude reference of the corresponding wind turbine and photovoltaic converter based on the circulating reactive component on the AC microgrid bus.

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