Power control method and system for alternating-current and direct-current hybrid microgrid

Abstract

The invention discloses an AC-DC hybrid microgrid power control method and system, and the method comprises the steps: measuring the operation state quantity of a system at the kth sampling moment of a current control period, and building an AC-side mathematical model of an interconnection converter according to the operation state quantity; according to the operation state quantity of the interconnected converter, judging the power transmission direction of the interconnected converter; a power prediction model is established, and active power and reactive power prediction values at the k + 1 moment are solved in combination with different switching states; calculating a power reference trajectory, and calculating a cost function value corresponding to each switching state by combining the predicted values of the active power and the reactive power; obtaining cost function values under all switching states, selecting the switching state corresponding to the minimum cost function value, and applying the switching state to the bridge arm switching control of the interconnected converter; and entering a next control period, and repeating the steps. According to the invention, bidirectional power mutual assistance between AC and DC hybrid power grids can be realized in multiple scenes of the flexible interconnection hybrid power grid, and the voltage stability is improved.

Description

Technical Field

[0001] This invention belongs to the field of AC / DC hybrid microgrid power control technology, and particularly relates to an AC / DC hybrid microgrid power control method and system. Background Technology

[0002] The increasing penetration rate of flexible power resources, primarily renewable energy, is significantly impacting the safe and stable operation of distribution networks. The topology of AC / DC interconnected hybrid power grids can efficiently absorb large-scale flexible power resources through coordinated operation on both the AC and DC sides. Therefore, AC / DC interconnected hybrid power grids will become the main form of connecting flexible power resources to distribution networks in the future.

[0003] The flexible interconnection converter (FIC) for hybrid AC / DC grids is a core device for balancing the power of microgrids on both sides. It coordinates and controls AC / DC microgrids, playing a crucial role in maintaining system frequency and voltage stability. Existing interconnection converter power control strategies mostly employ dual-loop tracking in the dq coordinate system to achieve decoupling control of active and reactive power. This is achieved by designing independent control loops for voltage and current and connecting them in series. In dual-loop control, five PI regulation parameters (voltage inner loop, current inner loop, and phase-locked loop) need to be tuned. Parameter tuning is very complex, and the response speed is slow. Furthermore, the coupling effect of the flexible interconnection converter on the AC / DC side amplifies the range of disturbances, especially during off-grid operation, where the flexible interconnection converter can impact the stable operation of the entire system.

[0004] Flexible interconnection converters in AC / DC hybrid power grids require simultaneous regulation of both AC frequency and DC voltage. Traditional voltage source converters (VSCs) that only consider one side are no longer applicable. Existing technologies, such as the literature (“A New Control Strategy for AC / DC Bidirectional Power Converters in AC / DC Hybrid Microgrids,” *Power System Protection and Control*, Tang Lei et al., 2013), (“Cooperative Control Strategy for AC / DC Hybrid Microgrids,” *Power Automation Equipment*, Zhou Wen et al., 2015), (“A Review of Bidirectional Interface Converter Control in AC / DC Hybrid Microgrids,” *Journal of Power Supply*, Wang Xiaosheng et al., 2016), and (“Research on Control Strategy for Bidirectional AC / DC Power Converters in AC / DC Hybrid Microgrids,” *Taiyuan University of Technology*, Liu Jiayi et al., 2014), have proposed bidirectional power control strategies capable of simultaneously regulating both AC frequency and DC voltage by improving traditional droop control equations or studying the coupling relationship between AC frequency and DC voltage. For example, the literature (“Control strategy for virtual synchronous generator in AC / DC bus interface converter of hybrid microgrid”, Proceedings of the CSEE, Li Feng et al., 2019) and the literature (“A dual-adaptivity inertia control strategy for virtual synchronous generator”, IEEE Transactions on Power Systems, Li M et al., 2020) have achieved bidirectional power control between AC and DC microgrids by linking AC frequency and DC voltage based on the per-unit method or from the perspective of energy balance when controlling the microgrid interconnection converter.

[0005] Existing methods for power regulation in islanded hybrid microgrids often face a contradiction between AC frequency optimization and DC voltage optimization due to limitations in the power regulation capabilities of dispatchable flexible resources. The key to improving the control performance of flexible interconnected converters lies in resolving the contradiction between AC and DC control objectives within the constraints of regulation capabilities. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a bidirectional power model predictive control for flexible interconnected converters with flexible resource access. This invention is applicable to AC / DC hybrid power grids to ensure the stability of AC grid frequency and DC grid voltage. Addressing the limitations of traditional interconnected converter control strategies, such as difficult parameter tuning, slow response speed, difficulty in achieving multi-objective optimization, and limited applicability, this invention establishes a discretized mathematical model of the flexible interconnected converter and optimizes the cost function, which includes active and reactive power tracking and switching frequency, to achieve direct power control of the flexible interconnected converter. This invention predicts power over a single long period and uses a finite set solution for the cost function, resulting in lower computational resource requirements. It combines the advantages of strong robustness to parameter changes in PI control and good dynamic characteristics of model predictive control. Furthermore, this invention can adaptively adjust the power flow direction according to operating conditions, effectively achieving bidirectional power mutual assistance between AC and DC hybrid power grids in various scenarios of flexible interconnected hybrid power grids, improving the frequency and voltage stability of the hybrid power grid, and exhibiting smooth control effects and good dynamic performance.

[0007] The present invention adopts the following technical solution.

[0008] This invention proposes a power control method for AC / DC hybrid microgrids, comprising: S1, in the current control cycle... At each sampling time, the operating state variables of the system are measured, and a mathematical model of the AC side of the interconnected converter is established based on the operating state variables; the AC side mathematical model is then converted to... In coordinate system, we obtain The operating state variables of the interconnected converter in the coordinate system are Components in the coordinate system; S2, utilizing runtime state variables in Calculate the AC frequency deviation and DC voltage deviation, and the AC voltage deviation and DC voltage deviation in the coordinate system to determine the power transmission direction of the interconnected converter; S3, different switching states For different interconnected converter AC side voltages, combined with Mathematical model of AC side and power transmission direction in coordinate system, as well as switching state. Based on the corresponding AC side voltage, a power prediction model is established to obtain the active power at time k+1. and reactive power The predicted value; S4, Calculate the active power reference trajectory and reactive power reference trajectory and combined with active power and reactive power The predicted value; combined with active power and reactive power The predicted value is used to calculate each switching state. Corresponding cost function value , the cost function value As an evaluation of the control effect under this switching state; S5, obtain the cost function values ​​for all switching states, and select the minimum cost function value from them. The corresponding switch state is denoted as This was applied to the control of bridge arm switches in interconnected converters. S6, enter the next control cycle, repeat S1~S5.

[0009] Furthermore, in S1, the measured operating state quantities include The three-phase voltage output from the AC side of the converter at any time and current , AC bus three-phase voltage , Frequency of communication at any moment , DC bus voltage at time .

[0010] Furthermore, in S2, the AC frequency deviation, AC voltage deviation, and DC voltage deviation in the operating state variables are normalized; multiple scenarios are described: If the normalized AC frequency deviation equals the DC voltage deviation, and the AC voltage deviation equals the DC voltage deviation, then the interconnected converter does not need to transmit power and is in normal operation. If the normalized AC frequency deviation is greater than the DC voltage deviation, and the AC voltage deviation is greater than the DC voltage deviation, then the interconnected converter transmits active and reactive power to the AC side, which indicates a fault on the AC side. If the normalized AC frequency deviation is less than the DC voltage deviation, and the AC voltage deviation is less than the DC voltage deviation, then the interconnected converter transmits active power to the DC side, which indicates a fault on the DC side.

[0011] Furthermore, in S3, for The mathematical model of the AC side of the interconnected converter in the coordinate system is discretized to obtain the discrete mathematical model of the interconnected converter, as shown in the following equation: ; In the formula: This indicates that at time k+1, the AC side output three-phase current of the converter is at... Two components in the coordinate system; The sampling period; Let k be the DC-side voltage of the converter at time k; This indicates that the three-phase voltage of the AC bus at time k is... Two components in the coordinate system; This indicates the switching state of the three-phase bridge arm of the interconnected converter at time k. Two components in the coordinate system; This refers to the total inductance of the filters and lines between the AC side of the converter and the AC bus.

[0012] Furthermore, in S3, based on the determination result of the power transmission direction of the interconnected converter, the predicted value of the interconnected converter power is obtained. The power prediction model is shown in the following equation: ; ; In the formula: , These represent the predicted active and reactive power values ​​of the interconnected converter at time k+1, respectively. and These represent the three-phase output currents on the AC side of the converter at time k+1. Two components in the coordinate system; and These represent the three-phase voltages of the AC bus at time k+1, respectively. Two components in the coordinate system.

[0013] Furthermore, in S4, the active power reference trajectory of the interconnected converter... Set it to the following form: ; In the formula, This represents the normalized AC frequency deviation. This is the normalized DC voltage deviation; This is the proportional control coefficient. This is the integral control coefficient.

[0014] Furthermore, in S4, the cost function is constructed as shown in the following equation. : ; In the formula, For active power reference trajectory, , These represent the predicted active and reactive power values ​​of the interconnected converter at time k+1, respectively. For reactive power reference trajectory, , , These are the weighting coefficients for active power, reactive power, and the number of switching operations, respectively. This represents the sum of the number of switching actions from the previous control moment to the current control moment.

[0015] This invention also proposes an AC / DC hybrid microgrid power control system, including an AC-side mathematical model construction module, a power transmission direction determination module, a power prediction module, a cost function value calculation module, and an action module: The mathematical model construction module on the communication side, in the current control cycle, At each sampling time, the operating state variables of the system are measured, and a mathematical model of the AC side of the interconnected converter is established based on the operating state variables. The power transmission direction determination module determines the power transmission direction of the interconnected converter based on the operating status parameters of the interconnected converter. The power prediction module establishes a power prediction model, taking into account different switching states. Solve for the active power at time k+1. and reactive power The predicted value; The cost function value calculation module calculates the power reference trajectory. and combined with active power and reactive power The predicted value is used to calculate each switching state. Corresponding cost function value ; The action module obtains the cost function values ​​for all on / off states and selects the minimum cost function value from them. The corresponding switch state is denoted as This is applied to the control of bridge arm switches in interconnected converters.

[0016] Furthermore, the power prediction module also includes a discrete mathematical model building unit for interconnected converters and a power prediction model building unit; In the discrete mathematical model construction unit, the mathematical model construction module for the AC side... The mathematical model of the communication side in the coordinate system is discretized.

[0017] Furthermore, the AC / DC hybrid microgrid power control system described herein must run in each control cycle and iterate repeatedly to achieve optimal control.

[0018] The present invention also proposes a terminal, including a processor and a storage medium: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to perform the steps of the method described in any of the preceding descriptions.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention can realize the stable operation of flexible interconnected hybrid power grids in multiple scenarios, such as AC side faults, DC side faults, and normal operation. The operating conditions are judged based on the deviation values ​​of the corresponding quantities on the AC and DC sides, and the power flow direction is adaptively adjusted.

[0020] 2. This invention establishes a discretized mathematical model of the interconnected converter through principle derivation, designs a multi-objective cost function that takes into account both AC side frequency optimization and DC side voltage optimization, and achieves coordinated control of AC and DC sides through rolling optimization, thereby improving the dynamic response capability of the interconnected converter.

[0021] 3. This invention optimizes the cost function in each sampling period and uses finite set solution to obtain the switching input of the flexible interconnected converter. It has low computational resource requirements, does not require complex parameter tuning, and combines the advantages of strong robustness of PI control to parameter changes and good dynamic characteristics of model predictive control. Attached Figure Description

[0022] Figure 1 This is a diagram of the flexible interconnected hybrid power grid topology of the present invention; Figure 2 This is a flowchart of the model predictive control of the present invention; Figure 3 This is the flexible interconnected converter topology of the present invention; Figure 4 These are the simulation results of this invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0024] Example 1 This invention proposes a power control method for AC / DC hybrid microgrids. For example... Figure 1 The diagram shows a flexible interconnected hybrid power grid topology. The AC microgrid and DC microgrid are flexibly interconnected through a flexible interconnection converter (FIC). Power can flow bidirectionally on both the AC and DC sides. The operation mode of the hybrid power grid, whether it is connected to the grid or off-grid, is determined by the closing and opening of the switches.

[0025] AC microgrids contain two Adjustable power supplies DG1, DG2 and one with droop control The controlled, non-adjustable power supply DG3, the DC microgrid contains two Adjustable power supplies with droop control DG4, DG5 and one The uncontrolled power supply DG6.

[0026] Flexible interconnected converter topology such as Figure 2 The diagram shows a voltage source converter (VSC), where: , ( These represent the three-phase voltage and current output from the AC side of the converter, respectively. ( () represents the three-phase voltage of the AC bus. The total inductance of the filters and lines between the AC side of the converter and the AC bus. For DC filter capacitors, Let be the DC-side voltage of the converter; let be the DC-side current of the converter. The active power exchanged between AC and DC microgrids is denoted as .

[0027] The flowchart of model predictive control is as follows: Figure 2 As shown, model predictive control iteratively solves for the predicted power value for the next cycle based on the current operating state of the system and the control command in each control cycle. The switching state that minimizes the cost function is then used as the control output to act on the interconnected converter, achieving optimal bidirectional power control.

[0028] S1, in the current control cycle... At each sampling time, the operating state variables of the system are measured, and a mathematical model of the AC side of the interconnected converter is established based on the operating state variables; the AC side mathematical model is then converted to... In coordinate system, we obtain The operating state variables of the interconnected converter in the coordinate system are Components in the coordinate system; The system's operational state variables include The three-phase voltage output from the AC side of the converter at any time and current , AC bus three-phase voltage , Frequency of communication at any moment , DC bus voltage at time .

[0029] by Figure 3 The inverter direction shown is the positive power direction. Taking the positive power direction as the reference direction, the AC side mathematical model of the hybrid power grid flexible interconnection converter is established as shown in the following formula.

[0030] ; In the formula: The switching status of the three-phase bridge arm of the interconnected converter ( = a, b, c), = 1 indicates the first The upper bridge arm is conducting, and the lower bridge arm is turning off; = 0 indicates the first The upper bridge arm is turned off, and the lower bridge arm is turned on.

[0031] To facilitate decoupled control of the active and reactive power of the interconnected converter, a Clark transformation is applied to the AC side mathematical model of the flexible interconnected converter in the hybrid power grid, converting the three-phase current and voltage data to... In coordinate system: ; get The interconnected converter model in the coordinate system is shown in the following equation.

[0032] ; In the formula: , These represent the three-phase output voltage and current of the converter on the AC side, respectively. Two components in the coordinate system; Indicates the three-phase voltage of the AC bus at Two components in the coordinate system; Indicates the switching state of the three-phase bridge arm of the interconnected converter. Two components in the coordinate system; This refers to the total inductance of the filters and lines between the AC side of the converter and the AC bus.

[0033] S2, utilizing runtime state variables in The components in the coordinate system are used to calculate the AC frequency deviation and DC voltage deviation, and the AC voltage deviation and DC voltage deviation to determine the power transmission direction of the interconnected converter.

[0034] To achieve global power distribution in a hybrid AC / DC microgrid, the flexible interconnected converter should regulate the bidirectional power between the AC and DC microgrids, balancing and compensating for AC frequency deviation and DC voltage deviation, as well as AC voltage deviation and DC voltage deviation, so that the normalized AC frequency and AC voltage deviation values ​​are equal to the DC voltage deviation value, i.e., satisfying the following condition: ; In the formula, This represents the normalized AC frequency deviation. This is the normalized DC voltage deviation; This represents the normalized AC voltage deviation. This represents the difference between the normalized AC frequency deviation and the DC voltage deviation. This represents the difference between the normalized AC voltage deviation and the DC voltage deviation.

[0035] During normal operation, the AC frequency, voltage, and DC voltage are all at their rated values, and the difference between the two sets of predicted power distribution rates is 0. When a fault occurs on the AC side, the AC frequency and voltage drop rapidly, while the DC voltage remains unchanged for a short period. >0, >0, needs to be minimized as much as possible. and To bring it closer to 0, a flexible interconnected converter is needed to transfer active and reactive power to the AC side to stabilize the AC frequency and voltage. When a fault occurs on the DC side, the DC voltage drops rapidly, and the AC frequency remains unchanged for a short period. <0, <0, in order to make it approach 0, the flexible interconnected converter needs to transmit active power to the DC side to stabilize the DC voltage.

[0036] By normalizing the AC frequency deviation, AC voltage deviation, and DC voltage deviation, the relative changes of each parameter can be better compared, thereby determining the direction of power transmission. This method can effectively reduce errors under different operating conditions, enabling the system to respond quickly under different fault scenarios. After normalization, deviations can be reasonably controlled, improving the robustness of the system, ensuring coordination between AC and DC power grids in multiple scenarios, and ensuring the stability of the power grid.

[0037] S3, different switching states For different interconnected converter AC side voltages, combined with Mathematical model of AC side and power transmission direction in coordinate system, as well as switching state. Based on the corresponding AC side voltage, a power prediction model is established to obtain the active power at time k+1. and reactive power The predicted value.

[0038] Three-phase switch status There are 8 different combinations, each corresponding to a different AC side voltage of the interconnected converter. If the voltage vector is expressed by the following formula, the correspondence between the switching state and the voltage vector is shown in Table 1.

[0039] ; In the formula, Represents the voltage vector. , Representing voltage vectors respectively exist Components in the coordinate system.

[0040] Table 1 Switching states and voltage vectors

[0041] Using the first-order forward difference method to The interconnected converter model in the coordinate system is discretized to obtain the discrete mathematical model of the interconnected converter, as shown in the following equation: ; In the formula: This indicates that at time k+1, the AC side output three-phase current of the converter is at... Two components in the coordinate system; The sampling period; Let k be the DC-side voltage of the converter at time k; This indicates that the three-phase voltage of the AC bus at time k is... Two components in the coordinate system; This indicates the switching state of the three-phase bridge arm of the interconnected converter at time k. Two components in the coordinate system; This refers to the total inductance of the filters and lines between the AC side of the converter and the AC bus.

[0042] Interconnected converters regulate the power interaction between AC and DC microgrids by controlling their own power direction and magnitude. Based on instantaneous power theory, the predicted power of the interconnected converter can be obtained. The power prediction model is shown in the following equation: ; ; In the formula: , These represent the predicted active and reactive power values ​​of the interconnected converter at time k+1, respectively. and These represent the three-phase output currents on the AC side of the converter at time k+1. Two components in the coordinate system; and These represent the three-phase voltages of the AC bus at time k+1, respectively. The two components in the coordinate system can be obtained using the quadratic Lagrange interpolation formula: ; In the formula, , Representing the three-phase voltages of the AC bus at times k-1 and k-2 respectively. Quantity, , Representing the three-phase voltages of the AC bus at times k-1 and k-2 respectively. Quantity.

[0043] By discretizing the AC-side mathematical model of the interconnected converter, its dynamic behavior can be accurately described, resulting in more precise power prediction. Discretization enables the system to calculate more accurate power values ​​in each sampling period, thereby improving the precision of power control. This method makes real-time control more feasible, optimizes power flow, and enhances the grid's response speed and control accuracy in various scenarios.

[0044] S4, Calculate the active power reference trajectory and reactive power reference trajectory and combined with active power and reactive power The predicted value; combined with active power and reactive power The predicted value is used to calculate each switching state. Corresponding cost function value , the cost function value This serves as an evaluation of the control effectiveness under this switching state.

[0045] Active power reference trajectory of flexible interconnected converter It can be set in the following form: ; In the formula, This represents the normalized AC frequency deviation. This is the normalized DC voltage deviation; This is the proportional control coefficient. This is the integral control coefficient.

[0046] To achieve tracking control of active and reactive power reference values ​​by the flexible interconnected converter, a cost function as shown in the following equation is constructed. : ; In the formula, , These represent the predicted active and reactive power values ​​of the interconnected converter at time k+1, respectively. The reactive power reference trajectory is calculated using the same method as the active power reference trajectory. same, , , These are the weighting coefficients for active power, reactive power, and number of switch switching operations, respectively. This represents the sum of the number of switching actions from the previous control moment to the current control moment.

[0047] By calculating reference trajectories for active and reactive power and combining them with predicted values ​​for optimized control, a more precise power control strategy can be achieved. This method can dynamically adjust the power reference trajectory according to actual operating conditions, thereby enabling the power grid to maintain efficient and stable operation under varying load conditions. Real-time adjustment and accurate calculation of the reference trajectory make power regulation more rational, avoiding energy waste caused by over-adjustment and improving the system's energy efficiency and stability.

[0048] S5, obtain the cost function values ​​for all switching states, and select the minimum cost function value from them. The corresponding switch state is denoted as This is applied to the control of bridge arm switches in interconnected converters.

[0049] Optimized control can be achieved by calculating the cost function values ​​under different switching states and selecting the switching state corresponding to the minimum value. This process effectively reduces energy loss during control and improves the system's dynamic response capability. By evaluating the cost function of different switching states, it can be ensured that the system always adopts the optimal control strategy in each control cycle, thereby achieving more efficient and smooth power control and improving the stability and reliability of the power grid.

[0050] S6, in the next control cycle Repeat S1~S5.

[0051] Example 2 The purpose of this embodiment is to experimentally verify the AC / DC hybrid microgrid power control method described in Embodiment 1. A system was built in MATLAB / Simulink as follows: Figure 1 The simulation model of the hybrid microgrid shown is illustrated. The simulation system parameters are shown in Table 2.

[0052] Table 2 System Parameters

[0053] The effectiveness of the proposed control strategy was verified through simulation under load changes on both sides of the AC / DC microgrid. The verification scenario was set as follows: at the start of the simulation, the load in both the AC and DC microgrids was 0.3MW, and DG1 and DG2 each output 0.3MW. At this time, the source and load in the AC / DC microgrid were balanced, and the AC frequency and DC voltage were controlled at their rated values. A fault occurred on the AC side at 2 seconds, a fault occurred on the DC side at 4 seconds, and the AC side fault was resolved at 6 seconds. The simulation results are as follows. Figure 4 As shown.

[0054] Example 3 This invention also provides a power control system for an AC / DC hybrid microgrid, comprising an AC-side mathematical model construction module, a power transmission direction determination module, a power prediction module, a cost function value calculation module, and an action module: The mathematical model construction module on the communication side, in the current control cycle, At each sampling time, the operating state variables of the system are measured, and a mathematical model of the AC side of the interconnected converter is established based on the operating state variables. The power transmission direction determination module determines the power transmission direction of the interconnected converter based on the operating status parameters of the interconnected converter. The power prediction module establishes a power prediction model, taking into account different switching states. Solve for the active and reactive power at time k+1. and The predicted value; The cost function value calculation module calculates the power reference trajectory. And combine active power and reactive power and The predicted value is used to calculate each switching state. Corresponding cost function value ; The action module obtains the cost function values ​​for all on / off states and selects the minimum cost function value from them. The corresponding switch state is denoted as This is applied to the control of bridge arm switches in interconnected converters.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A power control method for AC / DC hybrid microgrids, characterized in that, include: S1, in the current control cycle... The system's operating state variables are measured at each sampling time, and a mathematical model of the AC side of the interconnected converter is established based on these variables. The AC side mathematical model is then converted to... In coordinate system, we obtain Operating state variables in coordinate system Components in the coordinate system; S2, using the running state variables in The components in the coordinate system are used to determine the power transmission direction of the interconnected converter; S3, combined with... Based on the AC side mathematical model and power transmission direction in the coordinate system, as well as the different AC side voltages corresponding to different switching states, a power prediction model is established to obtain the predicted values ​​of active and reactive power at time k+1; S4, the active power reference trajectory and reactive power reference trajectory are calculated, and the cost function value corresponding to each switching state is calculated; S5, the cost function values ​​of all switching states are obtained, and the switching state corresponding to the minimum cost function value is selected and applied to the bridge arm switching control of the interconnected converter; S6, the next control cycle is entered, and S1~S5 are repeated.

2. The AC / DC hybrid microgrid power control method according to claim 1, characterized in that: In S1, the measured operating state quantities include The three-phase voltage output from the AC side of the converter at any time and current , AC bus three-phase voltage , Frequency of communication at any moment , DC bus voltage at time .

3. The AC / DC hybrid microgrid power control method according to claim 1, characterized in that: In S2, the AC frequency deviation, AC voltage deviation, and DC voltage deviation in the operating status variables are normalized; multiple scenarios are described: If the normalized AC frequency deviation equals the DC voltage deviation, and the AC voltage deviation equals the DC voltage deviation, then the interconnected converter does not need to transmit power and is in normal operation. If the normalized AC frequency deviation is greater than the DC voltage deviation, and the AC voltage deviation is greater than the DC voltage deviation, then the interconnected converter transmits active and reactive power to the AC side, which indicates a fault on the AC side. If the normalized AC frequency deviation is less than the DC voltage deviation, and the AC voltage deviation is less than the DC voltage deviation, then the interconnected converter transmits active power to the DC side, which indicates a fault on the DC side.

4. The AC / DC hybrid microgrid power control method according to claim 1, characterized in that: In S3, the predicted power value of the interconnected converter is obtained by combining the judgment result of the power transmission direction of the interconnected converter. The power prediction model is shown in the following formula: ； ； In the formula: , These represent the predicted active and reactive power values ​​of the interconnected converter at time k+1, respectively. and These represent the three-phase output currents on the AC side of the converter at time k+1. Two components in the coordinate system; and These represent the three-phase voltages of the AC bus at time k+1. Two components in the coordinate system.

5. The AC / DC hybrid microgrid power control method according to claim 1, characterized in that: In S4, the active power reference trajectory of the interconnected converter. Set it to the following form: ； In the formula, This represents the normalized AC frequency deviation. This is the normalized DC voltage deviation; This is the proportional control coefficient. This is the integral control coefficient.

6. A power control method for an AC / DC hybrid microgrid according to claim 1 or 5, characterized in that: In S4, the cost function is constructed as shown in the following equation. : ； In the formula, For active power reference trajectory, , These represent the predicted active and reactive power values ​​of the interconnected converter at time k+1, respectively. For reactive power reference trajectory, , , These are the weighting coefficients for active power, reactive power, and the number of switching operations, respectively. This represents the sum of the number of switching actions from the previous control moment to the current control moment.

7. A power control system for a hybrid AC / DC microgrid, comprising an AC-side mathematical model construction module, a power transmission direction determination module, a power prediction module, a cost function value calculation module, and an action module, characterized in that: The mathematical model construction module on the communication side, in the current control cycle, At each sampling time, the operating state variables of the system are measured, and a mathematical model of the AC side of the interconnected converter is established based on the operating state variables. The power transmission direction determination module determines the power transmission direction of the interconnected converter based on the operating status parameters of the interconnected converter. The power prediction module establishes a power prediction model, taking into account different switching states. Solve for the active power at time k+1. and reactive power The predicted value; The cost function value calculation module calculates the power reference trajectory. and combined with active power and reactive power The predicted value is used to calculate each switching state. The corresponding cost function value ; The action module obtains the cost function values ​​for all on / off states and selects the minimum cost function value from them. The corresponding switch state is denoted as This is applied to the control of bridge arm switches in interconnected converters.

8. The AC / DC hybrid microgrid power control system according to claim 7, characterized in that: The power prediction module also includes a discrete mathematical model building unit for interconnected converters and a power prediction model building unit; In the discrete mathematical model construction unit, the mathematical model construction module for the AC side... The mathematical model of the communication side in the coordinate system is discretized.

9. The AC / DC hybrid microgrid power control system according to claim 7, characterized in that: The aforementioned AC / DC hybrid microgrid power control system operates in each control cycle, iterating repeatedly to achieve optimal control.

10. A terminal, comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to perform the steps of the method according to any one of claims 1-6.

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