Dynamic event-triggered distributed quadratic control method and device with preset time convergence

Abstract

The application discloses a dynamic event-triggered distributed secondary control method and device with preset time convergence. The application introduces time-varying gain acting on the integrator input of the voltage recovery channel and the current sharing channel, so that the integral rate is adaptively increased with time, the voltage recovery error and the current sharing error are driven to converge in a preset convergence time, and the convergence time is irrelevant to the initial conditions of the system. A double-layer dynamic event-triggering mechanism composed of a state triggering layer and an energy triggering layer is designed. The state triggering layer introduces an idle factor relaxation mechanism to adaptively adjust the triggering threshold, and the energy triggering layer captures the continuous small amplitude drift by accumulating error energy. The triggering threshold is adaptively adjusted by means of time-varying gain and dynamic auxiliary variables, so that the communication frequency automatically follows the convergence process. The application significantly reduces the communication overhead while ensuring the control accuracy, and is suitable for the distributed secondary control scene of a bandwidth-limited direct-current microgrid.

Description

Technical Field

[0001] This invention belongs to the field of distributed control technology for microgrids, specifically relating to a dynamic event-triggered distributed secondary control method and device with preset time convergence. Background Technology

[0002] With the increasing penetration of renewable energy and the rapid development of power electronics technology, DC microgrids have become an important platform for distributed generation (DG) integration. Distributed secondary control achieves global consistency through information exchange between neighbors, offering significant advantages and becoming a research hotspot in the control field in recent years. However, existing distributed secondary control methods still have limitations in terms of convergence performance and communication efficiency. The convergence process theoretically requires a long time, and periodic communication wastes communication resources. These shortcomings cause DC microgrids to converge too slowly when facing rapid changes such as load abrupt changes, leading to problems such as voltage exceeding limits. Therefore, there is an urgent need for a control method that simultaneously satisfies both communication efficiency and convergence speed.

[0003] Traditional convergence methods typically employ asymptotic convergence, but this approach struggles to guarantee the dynamic response of microgrids, thus impacting system reliability. To improve convergence speed, finite-time consistency control (FTCH) has been introduced into the microgrid domain, using nonlinear protocols to bring the system to a convergent state within a finite timeframe. However, the upper bound of FTCH convergence depends on initial system conditions, failing to guarantee a uniform response speed and exhibiting significant control input jitter. Fixed-time control (PCC) relaxes the dependence on initial conditions, offering greater robustness, but remains highly dependent on system parameters. Preset-time convergence (PTC), by introducing a time-varying function, can be pre-set, resolving the dependence of finite-time convergence on initial states. Currently, PTC has demonstrated superior performance in distributed optimization and automotive control, but existing solutions primarily target static optimization scheduling or single dynamic systems. Research on its application in voltage-current coupling dynamic regulation in distributed secondary control of DC microgrids is relatively limited, and studies on co-designing PTC with integrators in voltage recovery and current sharing channels within microgrid secondary control are even rarer.

[0004] Another key challenge in distributed control lies in communication efficiency. Traditional consensus protocols require each distributed generation (DG) to exchange information with its neighbors in every control cycle, exacerbating data collisions and latency risks in bandwidth-constrained communication networks, resulting in significant communication overhead. Event-triggered control (ETC) only communicates when the system meets triggering conditions, reducing communication frequency while maintaining good control performance. However, most event-triggered methods are based on asymptotic or finite-time convergence, with triggering thresholds independent of the system's convergence process. Furthermore, triggering criteria are often based on single-layer instantaneous errors, making it difficult to capture the cumulative effect of continuous small drifts, which affects the final convergence accuracy. While some existing studies combine PTC and ETC, their triggering mechanisms remain single-layer structures and lack differentiated threshold adjustment strategies for the different convergence characteristics of voltage recovery and current sharing in microgrid secondary control. Therefore, how to coordinate the design of event-triggered control with convergence time and construct a two-layer triggering architecture that can simultaneously respond to instantaneous deviations and cumulative errors, allowing the communication frequency to adaptively adjust according to the convergence process, remains a pressing issue. Summary of the Invention

[0005] To address the problems of uncontrollable convergence speed, convergence time dependence on initial system conditions, and excessive communication resource consumption caused by periodic communication in distributed secondary control of DC microgrids, this invention provides a dynamic event-triggered distributed secondary control method with preset time convergence. This method aims to ensure that the voltage recovery error and current sharing error of the DC microgrid converge within a pre-specified time and are independent of the initial system conditions. It achieves a coordinated design of preset time convergence and dynamic event triggering, enabling the communication frequency to adaptively adjust according to the convergence process, and significantly reducing communication overhead while ensuring the control accuracy of voltage recovery and current sharing.

[0006] According to one aspect of the present invention, a dynamic event-triggered distributed secondary control method with preset time convergence is provided, comprising: each distributed generation unit acquiring local terminal voltage and output current in each sampling period and calculating weighted current; calculating time-varying gain based on the current time and preset parameters, wherein the time-varying gain is determined by secondary control activation time, preset convergence time, scaling exponent, and saturation upper bound; calculating composite measurement error and determining whether to trigger communication based on the composite measurement error and a two-layer dynamic event triggering mechanism composed of a state triggering layer and an energy triggering layer; if triggered, sending local weighted current information to neighboring nodes and updating local held value; otherwise, maintaining the held value sent last time; introducing the time-varying gain into the secondary control protocol to construct a voltage correction quantity composed of a voltage recovery channel and a current sharing channel, wherein the time-varying gain simultaneously acts on the integrator input of the voltage recovery channel and the current sharing channel, causing the integration rate to increase adaptively with time; sending the voltage correction quantity to the local control layer, combining it with droop control output to generate a corrected voltage reference value, driving each distributed generation unit to restore the terminal voltage to the rated value within a preset convergence time and distribute the load current according to the droop coefficient ratio.

[0007] As a further technical solution, the composite measurement error is constructed as follows: for any node's neighboring nodes, the measurement error of the neighbor weighted current is defined as the difference between the neighbor's actual current and the value held at the last trigger moment; the composite measurement error is constructed by combining the current measurement error and the normalized voltage deviation according to the weighting coefficient.

[0008] As a further technical solution, the state triggering layer is designed as follows: a neighbor inconsistency metric is defined, and a logarithmic preset time decay function is introduced to make the state triggering threshold monotonically decrease with the preset time process; a relaxation mechanism is introduced, defining an idle factor determined by the relaxation coefficient and the idle counter, increasing the triggering threshold when the idle counter accumulates to a set value, and decreasing the triggering threshold when the idle counter is cleared; and a state triggering condition is constructed by combining dynamic auxiliary variables and inconsistency coupling coefficients, triggering communication when the composite measurement error exceeds the triggering threshold.

[0009] As a further technical solution, the energy triggering layer is designed as follows: define the cumulative error energy, accumulate the composite measurement error according to the sampling period; couple the energy threshold with the time-varying gain, and introduce the historical trigger frequency ratio determined by the number of cumulative triggers; construct the energy triggering condition: increase the energy triggering threshold when the historical trigger frequency ratio increases; decrease the energy triggering threshold when the historical trigger frequency ratio decreases; and reset the accumulator to zero after energy triggering.

[0010] As a further technical solution, the dual-layer dynamic event triggering mechanism is as follows: the combined event triggering conditions are constructed by integrating the state triggering layer and the energy triggering layer. If the distributed generation unit meets any triggering condition, communication is triggered; otherwise, the previously received data is maintained and no communication is performed.

[0011] As a further technical solution, the dynamic auxiliary variable is updated according to the following rules: when triggered, the dynamic auxiliary variable is updated to the product of the current composite measurement error and the reset proportional coefficient, and the larger value is taken compared with the strictly positive definite lower bound; when not triggered, the dynamic auxiliary variable is updated to the value after linear decay according to the decay coefficient, and the larger value is taken compared with the strictly positive definite lower bound.

[0012] As a further technical solution, the time-varying gain is applied simultaneously to the integrator inputs of the voltage recovery channel and the current averaging channel, so that the voltage recovery error and the current averaging error converge within a preset convergence time, and the convergence time is independent of the initial conditions of the system.

[0013] According to one aspect of the present invention, a dynamic event-triggered distributed secondary control device with preset time convergence is provided, applied to a DC microgrid, comprising: a local measurement module for acquiring the local terminal voltage and output current of each distributed generation unit in each sampling period, and calculating the weighted current; a time-varying gain calculation module for calculating the time-varying gain based on the current time and preset parameters, wherein the time-varying gain is determined by the secondary control activation time, the preset convergence time, the scaling exponent, and the saturation upper bound; and a dual-layer dynamic event triggering module for calculating the composite measurement error and determining whether to trigger based on a dual-layer dynamic event triggering mechanism consisting of a state triggering layer and an energy triggering layer. Communication; if triggered, the local weighted current information is sent to neighboring nodes and the local held value is updated; otherwise, the held value sent last time is maintained; a secondary control protocol module is used to introduce the time-varying gain into the secondary control protocol to construct a voltage correction quantity consisting of a voltage recovery channel and a current sharing channel, wherein the time-varying gain acts on the integrator input of both the voltage channel and the current channel; a local control interface module is used to send the voltage correction quantity to the local control layer, combine it with the droop control output to generate a corrected voltage reference value, drive each distributed generation unit to restore the terminal voltage to the rated value within a preset convergence time and distribute the load current according to the droop coefficient ratio.

[0014] As a further technical solution, in the dual-layer dynamic event triggering module: the state triggering layer is configured to: define a neighbor inconsistency metric, introduce a logarithmic preset time decay function to make the state triggering threshold monotonically decrease with the preset time process; introduce an idle factor determined by a relaxation coefficient and an idle counter, increase the triggering threshold when the idle counter accumulates to a set value, and decrease the triggering threshold when the idle counter is cleared; and construct state triggering conditions by combining dynamic auxiliary variables and inconsistency coupling coefficients; the energy triggering layer is configured to: define accumulated error energy, accumulate composite measurement errors according to the sampling period, couple the energy threshold with the time-varying gain, and introduce the historical triggering frequency ratio determined by the accumulated triggering count to construct energy triggering conditions; the dual-layer dynamic event triggering module combines the state triggering layer and the energy triggering layer to form a combined event triggering condition, and the distributed generation unit triggers communication when any triggering condition is met.

[0015] According to one aspect of the present invention, an electronic device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the preset time convergence dynamic event-triggered distributed secondary control method.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. A time-varying gain is introduced and applied simultaneously to the integrator input of both the voltage recovery channel and the current averaging channel, so that the integration rate increases adaptively with time. This drives the voltage recovery error and the current averaging error to converge together within a pre-specified convergence time, and the convergence time is independent of the initial system conditions, thus achieving controllability of the convergence speed. 2. A two-layer dynamic event triggering mechanism consisting of a state triggering layer and an energy triggering layer is designed: The state triggering layer introduces an idle factor relaxation mechanism, which adaptively increases the triggering threshold to suppress redundant communication in steady state and promptly decreases the triggering threshold to ensure response sensitivity during disturbances; The energy triggering layer captures continuous small-amplitude drifts through accumulated error energy to compensate for the shortcomings of instantaneous triggering; The triggering threshold is adaptively adjusted by using time-varying gain and dynamic auxiliary variables, so that the communication frequency automatically follows the convergence process, significantly reducing communication overhead; 3. The preset time convergence and the two-layer dynamic event triggering are designed in a coordinated manner, so that the trigger threshold and the convergence process are correlated. This overcomes the limitation that the threshold and the convergence process are independent in traditional event triggering. At the same time, through the combined architecture of "instantaneous deviation detection" and "cumulative drift capture", the robustness of the system to rapidly changing scenarios such as load mutation is improved while ensuring control accuracy. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a diagram of the microgrid structure in an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the control objectives and problems in an embodiment of the present invention; Figure 3 This is a diagram of the preset time convergence secondary control protocol in an embodiment of the present invention; Figure 4 This is a diagram of the dynamic event triggering mechanism under a preset time in an embodiment of the present invention; Figure 5 This is a flowchart illustrating the controller in an embodiment of the present invention. Detailed Implementation

[0019] It should be noted that: Given the current technological background, there is an urgent need to propose a novel distributed secondary control method for DC microgrids that can effectively address the dual challenges of uncontrollable convergence speed and wasted communication resources. This method should achieve coordinated design of convergence time and event triggering mechanisms, improving the voltage recovery and current distribution regulation capabilities of DC microgrids under rapidly changing scenarios such as load abrupt changes. To this end, this invention proposes a dynamic event-triggered distributed secondary control method with preset convergence time. By introducing a time-varying function (time-varying gain) to improve the secondary control gain, voltage recovery and current distribution converge within a specified time and are independent of initial conditions. Furthermore, combined with a two-layer dynamic event triggering mechanism consisting of a state triggering layer and an energy triggering layer, the communication frequency is adaptively adjusted according to the convergence process. This effectively solves the problems of long convergence processes, communication redundancy caused by periodic communication, and the independence of trigger thresholds from the convergence process in traditional constant gain methods.

[0020] The terms “comprising” and “having”, and any variations thereof, in the specification, claims, and accompanying drawings of this invention are intended to cover a non-exclusive inclusion, such as a process, method, system, product, or apparatus that includes a series of steps or units, not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In addition, the technical features of the various embodiments or individual embodiments provided by the present invention can be arbitrarily combined to form new technical solutions. Such combinations are not bound by the order of steps and / or structural composition patterns, but must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0022] This invention primarily utilizes the preset-time convergence theory and a distributed dynamic event-triggered control strategy to improve the convergence performance and communication efficiency of distributed secondary control in DC microgrids. It proposes a preset-time convergence dynamic event-triggered distributed secondary control method. This invention fully leverages the adjustability of time-varying functions for convergence time by simultaneously applying time-varying gains to both the voltage recovery channel and the current sharing channel, achieving convergence within a specified time. For bandwidth-constrained scenarios, a two-layer dynamic event triggering mechanism is designed, using time-varying functions to adaptively adjust the trigger threshold, thereby achieving synergy between preset-time convergence and event triggering. The control effect obtained through this invention is more precise, effectively improving the convergence speed of DC microgrids under scenarios such as load mutations, and significantly reducing communication overhead.

[0023] The method provided by this invention can be implemented using computer simulation software technology (such as Simulink / RTlab). The microgrid structure diagram in the embodiments of this invention is shown below. Figure 1 As shown.

[0024] In modeling and setting control objectives for a DC microgrid, this invention first establishes an islanded DC microgrid topology model consisting of four distributed generation units (DGs). Each DG is connected to a common DC bus via a DC / DC converter and supplies power to the local load through line impedance. An electrical dynamic model for each DG is then established, including the dynamic relationship between the filter inductor current and the output voltage. Next, droop control is employed at the primary control layer. By introducing a virtual impedance, the output voltage decreases linearly with the load current, obtaining a local voltage reference value. At the local control layer, a voltage-current dual-loop PI structure is used. The outer loop generates a current reference based on voltage error, and the inner loop generates the duty cycle based on current error, treating them as an ideal tracking element. Finally, the control objective is set: to restore the terminal voltage of all DGs to their rated values ​​within a preset convergence time T, and to distribute the load current to each DG according to the droop coefficient ratio.

[0025] Specifically, define L i and C i For filter inductors and capacitors; i L V is the inductor current; i V is the output voltage of DG. in,i It is a DC input voltage source; d c,i For duty cycle control signal; i i This refers to the output current injected by the DG into the bus. Consider an islanded DC microgrid system consisting of N DGs, with the following topology: Figure 1 As shown. Each DG is connected to a common DC bus via a DC / DC converter and supplies power to the local load through the line impedance. The electrical dynamics of the i-th DG (i=1,2,...,N) can be represented as follows: ; .

[0026] Define V nom The set rated voltage; r d,i v is the droop coefficient of the i-th DG; ref,i This is the local voltage reference value after droop control processing. In the primary control layer, each DG uses droop control to achieve initial power distribution. Droop control introduces a virtual impedance to make the output voltage decrease linearly with the load current, thereby achieving power balance among DGs under conditions without communication. The droop control of the i-th DG can be expressed as follows: .

[0027] Define K pv K iv For voltage loop proportional and integral gain; K pi K ii For the current loop proportional and integral gain, i ref Let be the reference current, and s be the Laplace transform complex frequency domain operator. The dynamic response of the dual-loop controller is much faster than the time scale of the secondary control; here, it is considered an ideal tracking element. Droop control, while achieving power distribution, introduces bus voltage deviation, which requires compensation from the secondary control layer. The local controller employs a voltage-current dual-loop structure. The outer loop uses voltage error as input and generates a current reference through a PI controller; the inner loop uses current error as input and generates the duty cycle through a PI controller. This process can be expressed by the following equation: .

[0028] The implementation of distributed secondary control relies on communication between DGs. Here, the communication topology of the microgrid is modeled as an undirected graph G=(V,E), where V={1,2,...,N} is a set of nodes, and each node corresponds to a DG unit. Let be the set of edges, and each edge corresponds to a communication connection.

[0029] Define the adjacency matrix A = [a ij ]∈R N×N The degree matrix D = diag(d1, d2, ..., d N ),in Let be the degree of node i. The graph Laplacian matrix is ​​defined as: .

[0030] For the DG topology considered in this invention, its communication adjacency matrix A can be represented by the following formula: .

[0031] To ensure the convergence of the distributed consensus protocol, the communication graph G must satisfy the following connectivity conditions: Lemma 1: For a connected undirected graph G, its graph Laplacian matrix L is a positive semi-definite matrix, and its eigenvalues ​​can be arranged as λ1 < λ2 ≤ ... ≤ λ N The second smallest eigenvalue, λ², representing the algebraic connectivity, is greater than zero and determines the convergence rate of the consensus protocol.

[0032] Lemma 2: For any vector x, we have Where N is the total number of DG units, T is the matrix transpose flag, and the quadratic form of the Laplace matrix satisfies the following conditions: .

[0033] definition The convergence time is preset, and ε is an acceptable steady-state error for convergence. Unlike traditional asymptotic convergence methods, the above control objective should be within a certain time frame. The internal convergence is achieved.

[0034] The control objectives and problems described in the embodiments of the present invention are as follows: Figure 2 As shown, the distributed secondary control of a DC microgrid needs to achieve the following two control objectives simultaneously: 1) Compensate for the voltage deviation introduced by the droop control, so that the terminal voltage of all DGs returns to the rated value, i.e. ; 2) The load current is distributed among each DG according to the droop coefficient ratio, i.e. .

[0035] Define δ(t) as the compensation term for the secondary control. The control voltage after the secondary control layer intervenes can then be expressed as follows: .

[0036] Define k sc,v and k sc,iGain for voltage recovery and current equalization; g ij This represents the voltage consistency weight. Traditional distributed secondary control protocols employ a constant gain design, and its general form can be expressed by the following equation: .

[0037] The constant gain described above can guarantee that the control error asymptotically converges to zero under the condition that the communication graph is connected, but it cannot guarantee that convergence will be completed within a finite time. At the same time, this design requires each DG to exchange information with its neighbors in every sampling period, which will cause communication redundancy in bandwidth-limited communication networks.

[0038] Therefore, this invention mainly designs a distributed secondary control protocol and a corresponding communication strategy to achieve the following objectives: 1) The voltage recovery and current sharing objectives are achieved within a preset time, and the convergence time is independent of the initial system conditions; 2) Communication between DGs is triggered only when necessary, and the communication frequency is adaptively adjusted according to the convergence process; 3) The event-triggered mechanism does not produce Zeno behavior, and the system is stable in the Lyapunov sense.

[0039] In this embodiment of the invention, a preset time-convergence secondary control protocol is as follows: Figure 3 As shown.

[0040] Define t0 as the activation time of the secondary control; The preset convergence time is p; the scaling exponent is μ. max This serves as the upper bound for saturation, preventing numerical overflow. Traditional distributed quadratic control protocols employ constant gain, which only guarantees asymptotic convergence of the control error. To achieve controllable convergence time, a time-varying function μ(t) is introduced to dynamically process the control gain. This process can be expressed by the following equation: .

[0041] Define i use,i Let be the weighted current of the i-th DG. The weighted current value of neighbor j, updated via an event-triggered mechanism, is maintained constant by a zero-order hold between two triggers. Introducing μ(t) into the secondary control protocol, the modified voltage correction δ(t) consists of two parts: a voltage recovery channel and a current sharing channel. ; The time-varying function μ(t) acts simultaneously on the integrator inputs of both voltage and current channels, causing the integration rate to increase adaptively with time, thereby enabling the system to converge within a preset time, and the convergence time is independent of the initial conditions of the system.

[0042] The dynamic event triggering mechanism under a preset time in this embodiment of the invention is shown in the diagram below. Figure 4 As shown.

[0043] Traditional distributed secondary control requires each distributed generation (DG) to share its weighted current information with its neighbors in every sampling period, which imposes a heavy burden on bandwidth-constrained communication networks. To address this, this paper designs a dynamic event-triggered communication mechanism combined with a time-varying function μ(t), constructed from a state-triggered layer and an energy-triggered layer. The DG updates and communicates only when the triggering condition is met; otherwise, it retains the previously received data.

[0044] Define ε i Let i be the measurement error of the i-th DG on the weighted current of its neighbors. n1 and i n2 The actual current of the neighboring node. and This is the value held at the time of the last trigger.

[0045] First, define the composite measurement error required for the trigger criterion. For the two neighbors of node i, define the measurement error of the neighbor weighted current as follows: .

[0046] Define ε v,i For the normalized voltage deviation, σ i and σ v This is the weighting factor for current error and voltage deviation.

[0047] The composite measurement error can then be expressed as follows: ; .

[0048] The state triggering layer designs the trigger threshold as a monotonically decreasing function to achieve adaptive matching between communication frequency and convergence process, and defines the neighbor inconsistency metric as: .

[0049] Define ρ∈[0,1] as the decay rate parameter. In the initial stage of secondary control activation, the threshold remains at the original level, and the system performs coarse adjustment with sparse communication. When it approaches the preset time, γ(t) decays smaller, the threshold tightens, and the communication frequency is automatically increased to ensure convergence accuracy.

[0050] Then, a logarithmic preset time decay function is introduced: .

[0051] Define z as the relaxation coefficient; n q This is an idle counter; when the system remains in a steady state for a long time without any sudden events, n... qAs the number of cases continues to grow, the threshold is relaxed accordingly to further suppress redundant communication; once a certain condition occurs, n q The threshold is immediately reset to zero, tightening and forming a self-regulating loop.

[0052] Furthermore, a relaxation mechanism is introduced, defining the idle factor as: .

[0053] Define α as the inconsistency coupling coefficient. When the composite measurement error R... i When the threshold on the right is exceeded, the state trigger condition is met, and node i initiates communication. This is combined with the dynamic auxiliary variable η. i The state triggering conditions are defined as follows: .

[0054] Let h be the sampling period. The state triggering layer, based on instantaneous error judgment, may miss the accumulation of continuous small drifts. Therefore, this invention designs an accumulated energy triggering layer as a complementary mechanism. The accumulated error energy is defined as: .

[0055] Define n t This is the cumulative number of triggers. The energy threshold is also coupled to μ(t), and a communication frequency sensing mechanism is introduced, defining the historical trigger frequency ratio as: .

[0056] Define ξ0 as the baseline energy threshold. The energy triggering condition is defined as follows: .

[0057] μ(t) tightens the energy threshold over a preset time period, requiring more frequent communication at the end of convergence to eliminate residual errors. This mechanism dynamically adjusts based on the trigger frequency: the threshold widens when triggers are frequent to suppress excessive communication during transient periods; the threshold tightens when triggers are sparse to maintain the detection of new disturbances. After energy triggering, the accumulator ξ... i Reset to zero.

[0058] Define κ as the reset ratio coefficient when triggered; k η The rate of exponential decay; η min It is a strictly positive definite lower bound, and greater than 0. In this case, the dynamic auxiliary variable η... i An adaptive baseline is provided for the trigger threshold, and its update rules are as follows: ; Combining the state trigger layer and the energy trigger layer, the combined event triggering condition for the i-th DG is defined as follows: ; In other words, DG will trigger communication as long as either of the above two conditions is met; otherwise, it will maintain the data received last time and will not communicate.

[0059] The controller process in this embodiment of the invention is as follows: Figure 5 As shown in the figure. The method provided in this embodiment of the invention mainly consists of a physical layer, a local control layer, and a distributed secondary control layer.

[0060] The specific control steps are as follows: S1: Perform local measurements. Each DG measures its local terminal voltage and output current in each sampling period and calculates the weighted current. S2: The system calculates the time-varying gain μ(t) based on the current simulation time and preset parameters; S3: Calculate the composite measurement error R i The system considers factors such as state thresholds and energy thresholds, and makes trigger judgments. If a trigger occurs, updates and communication are performed; otherwise, the previous values ​​are retained. S4: Introduce μ(t) into the secondary control protocol, and obtain the modified amount δ(t) by adding the voltage recovery channel and the current equalization channel; S5: The voltage correction value δ(t) is combined with the droop control output to generate the corrected voltage reference value; S6: The voltage-current dual-loop PI controller of the local controller generates a duty cycle signal to drive the DC / DC converter.

[0061] Steps 1-6 above are executed cyclically in each sampling period. The communication in step 3 only occurs when the trigger condition is met. The neighbor information used by the current sharing channel in step 4 uses the previous held value when no trigger is triggered.

[0062] In this embodiment, after the system powers on, it first samples and collects the voltage and current data of each DG in real time, and then completes the preset time convergence adjustment based on the time base gain. This is done within a set finite time period. As the gain of the current and voltage channels increases, the recovery process accelerates until convergence. The current is evenly distributed, and the bus voltage deviation quickly falls into the controllable residual range. After the convergence phase, the system enters a steady state, the power of each distributed unit is precisely evenly distributed, and the bus voltage is stably maintained at the rated value.

[0063] By using a control framework that coordinates preset time convergence and dynamic event triggering, the convergence of voltage recovery and current distribution in DC microgrids within a specified time is achieved, and the communication frequency is adaptively adjusted according to the convergence process. This provides an effective technical solution for distributed control of DC microgrids in environments with limited bandwidth and rapid load changes.

[0064] Based on the same inventive concept as the aforementioned method embodiments, this invention also provides a preset time-convergence dynamic event-triggered distributed secondary control device for DC microgrids, comprising the following modules: The local measurement module is configured locally in each distributed generation unit. It is used to collect the local terminal voltage and output current of each distributed generation unit in each sampling period, calculate the weighted current based on the output current, and provide the collected and calculated data to other modules as input.

[0065] The time-varying gain calculation module is used to calculate the time-varying gain based on the current system running time and preset parameters. The preset parameters include the secondary control activation time, the preset convergence time, the scaling exponent, and the saturation upper bound. This module starts timing after the secondary control is activated, determines the evolution process of the time-varying gain based on the preset convergence time, controls the rate of increase of the gain based on the scaling exponent, and limits the maximum value of the gain through the saturation upper bound to prevent numerical overflow.

[0066] The dual-layer dynamic event triggering module is used to calculate composite measurement errors and determine whether to trigger communication based on a dual-layer dynamic event triggering mechanism consisting of a state triggering layer and an energy triggering layer. This module comprises two parts: a state triggering layer and an energy triggering layer.

[0067] The state triggering layer is configured as follows: a neighbor inconsistency metric is defined, and a logarithmic preset time decay function is introduced to make the state triggering threshold monotonically decrease over a preset time period; an idle factor determined by a relaxation coefficient and an idle counter is introduced, which increases the triggering threshold to reduce triggering sensitivity when the idle counter accumulates to a set value, and decreases the triggering threshold to increase triggering sensitivity when the idle counter is cleared; and a state triggering condition is constructed by combining dynamic auxiliary variables and inconsistency coupling coefficients, triggering communication when the composite measurement error exceeds the triggering threshold.

[0068] The energy triggering layer is configured to: define the accumulated error energy, accumulate the composite measurement error according to the sampling period; couple the energy threshold with the time-varying gain, and introduce the historical trigger frequency ratio determined by the number of accumulated triggers; increase the energy trigger threshold when the historical trigger frequency ratio increases, and decrease the energy trigger threshold when the historical trigger frequency ratio decreases; and reset the accumulator to zero after energy triggering.

[0069] The dual-layer dynamic event triggering module combines the state triggering layer and the energy triggering layer to form a combined event triggering condition. When any triggering condition is met, the distributed generation unit will trigger communication, send the local weighted current information to the neighboring nodes and update the local held value; if no condition is met, the held value sent last time will be maintained and no communication will be performed.

[0070] The secondary control protocol module is used to introduce the time-varying gain into the secondary control protocol to construct a voltage correction quantity consisting of a voltage recovery channel and a current balancing channel. The time-varying gain simultaneously acts on the integrator inputs of both the voltage recovery channel and the current balancing channel, causing the integration rates of both channels to adaptively increase over time.

[0071] The local control interface module is used to send the voltage correction amount to the local control layer, combine it with the droop control output, generate the corrected voltage reference value, drive each distributed generation unit to restore the terminal voltage to the rated value within a preset convergence time and distribute the load current according to the droop coefficient ratio.

[0072] The specific working principle, signal flow and parameter settings of each module in this device can be found in the detailed description in the foregoing method embodiments, and will not be repeated in this embodiment.

[0073] Based on the same inventive concept as the foregoing method embodiments, this invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. The memory stores the computer program and related data, and the processor executes the computer program. When the processor executes the computer program, it implements the preset-time convergence dynamic event-triggered distributed secondary control method as described in any of the foregoing method embodiments.

[0074] Specifically, when the processor executes the program, it performs the following functions: controls each distributed generation unit to acquire local terminal voltage and output current and calculate weighted current in each sampling period; calculates time-varying gain based on the current time and preset parameters, wherein the time-varying gain is determined by the secondary control activation time, preset convergence time, scaling exponent, and saturation upper bound; calculates composite measurement error and determines whether to trigger communication based on a two-layer dynamic event triggering mechanism consisting of a state triggering layer and an energy triggering layer; if triggered, sends the local weighted current information to neighboring nodes and updates the local hold value; otherwise, maintains the hold value sent last time; introduces the time-varying gain into the secondary control protocol to construct a voltage correction quantity consisting of a voltage recovery channel and a current sharing channel, wherein the time-varying gain simultaneously acts on the integrator input of the voltage recovery channel and the current sharing channel; sends the voltage correction quantity to the local control layer, combines it with the droop control output to generate a corrected voltage reference value, and drives each distributed generation unit to restore the terminal voltage to the rated value within a preset convergence time and distribute the load current according to the droop coefficient ratio.

[0075] The electronic device can be a local controller for the distributed generation unit (DG) or a higher-level control device independent of each DG. It interacts with the control systems of each DG via wired or wireless communication to achieve centralized collaborative control calculation and command issuance. The specific execution steps of the processor can be referred to the aforementioned method embodiments, and will not be repeated in this embodiment.

[0076] The electronic device can take the form of an industrial-grade embedded controller, industrial control computer, edge computing gateway or cloud server, etc. The specific selection is determined according to the scale, real-time requirements and deployment environment of the DC microgrid, and all of them are within the protection scope of this invention.

[0077] Those skilled in the art will understand that all or part of the steps of the above method embodiments can be implemented by hardware related to computer program instructions. The computer program can be stored in a computer-readable storage medium. When the program is executed, it performs the steps of the above method embodiments. The aforementioned storage medium includes various media that can store program code, such as ROM, RAM, magnetic disk, or optical disk.

[0078] In summary, the present invention provides a dynamic event-triggered distributed secondary control method with preset time convergence, which is suitable for solving problems such as uncontrollable convergence speed, excessive consumption of communication resources, and inability of communication frequency to adaptively match convergence requirements in the distributed secondary control of DC microgrids. First, a time-varying gain function is introduced to improve the traditional uniform secondary control gain. This time-varying function acts simultaneously on the integrator inputs of both the voltage recovery channel and the current averaging channel, causing the integration rate to increase adaptively with time. This ensures that the voltage recovery error and the current averaging error converge within a pre-specified time, and the convergence time is independent of the system's initial conditions. Second, a two-layer dynamic event triggering mechanism consisting of a state triggering layer and an energy triggering layer is designed. The state triggering layer sets the trigger threshold as a function that monotonically decreases with a preset time progression and introduces an idle factor relaxation mechanism. The energy triggering layer uses accumulated error energy as the criterion and introduces a communication frequency sensing mechanism. Both layers use a time-varying function to achieve adaptive adjustment of the trigger threshold. Then, a dynamic auxiliary variable is used as the adaptive baseline for the trigger threshold, allowing the communication frequency to automatically follow the convergence process. The threshold is tightened at the end of convergence to ensure convergence accuracy. Finally, communication between DGs only occurs when the triggering conditions are met; otherwise, the previously received data is retained, thereby reducing redundant communication. This invention can effectively improve the convergence performance of distributed secondary control in DC microgrids, and significantly reduce communication overhead while ensuring the accuracy of voltage recovery and current sharing control, providing technical support for distributed control of DC microgrids in bandwidth-constrained scenarios.

[0079] 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 them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A distributed secondary control method triggered by a dynamic event with preset convergence time, characterized in that, include: Each distributed generation unit acquires its local terminal voltage and output current in each sampling period and calculates the weighted current; The time-varying gain is calculated based on the current time and preset parameters. The time-varying gain is determined by the secondary control activation time, the preset convergence time, the scaling exponent, and the upper bound of saturation. Calculate the composite measurement error, and determine whether to trigger communication based on the composite measurement error and the two-layer dynamic event triggering mechanism consisting of a state triggering layer and an energy triggering layer. If triggered, the local weighted current information is sent to neighboring nodes and the local held value is updated; otherwise, the held value sent last time is maintained. The time-varying gain is introduced into the secondary control protocol to construct a voltage correction quantity consisting of a voltage recovery channel and a current equalization channel. The time-varying gain simultaneously acts on the integrator inputs of both the voltage recovery channel and the current equalization channel, causing the integration rate to adaptively increase over time. The state triggering layer is designed as follows: Define a neighbor inconsistency metric and introduce a logarithmic preset time decay function so that the state trigger threshold decreases monotonically over a preset time period. A relaxation mechanism is introduced, defining an idle factor determined by a relaxation coefficient and an idle counter. When the idle counter accumulates to a set value, the trigger threshold is increased, and when the idle counter is cleared, the trigger threshold is decreased. By combining dynamic auxiliary variables and inconsistency coupling coefficients, state triggering conditions are constructed to trigger communication when the composite measurement error exceeds the triggering threshold. The energy triggering layer is designed as follows: Define the cumulative error energy, and accumulate the composite measurement error according to the sampling period; This couples the energy threshold with the time-varying gain and introduces a historical trigger frequency ratio determined by the cumulative number of triggers; The voltage correction value is sent to the local control layer, and a corrected voltage reference value is generated by combining the droop control output. This drives each distributed generation unit to restore the terminal voltage to the rated value within a preset convergence time and distribute the load current according to the droop coefficient ratio.

2. The method for distributed secondary control triggered by a dynamic event with preset time convergence according to claim 1, characterized in that, The composite measurement error is constructed as follows: For any node's neighboring nodes, the measurement error of the neighbor weighted current is defined as the difference between the neighbor's actual current and the value held at the last trigger moment; By combining the current measurement error and the normalized voltage deviation, a composite measurement error is constructed using weighting coefficients.

3. The method for distributed secondary control triggered by a dynamic event with preset time convergence according to claim 1, characterized in that, The energy triggering layer also includes: Construct energy triggering conditions: increase the energy triggering threshold when the historical triggering frequency ratio increases; decrease the energy triggering threshold when the historical triggering frequency ratio decreases. The accumulator will be reset to zero after the energy is triggered.

4. The method for distributed secondary control triggered by a dynamic event with preset time convergence according to claim 1, characterized in that, The dual-layer dynamic event triggering mechanism is as follows: the combined event triggering conditions are constructed by integrating the state triggering layer and the energy triggering layer. If the distributed generation unit meets any of the triggering conditions, communication is triggered; otherwise, the previously received data is maintained and no communication is performed.

5. The method for distributed secondary control triggered by a dynamic event with preset time convergence according to claim 1, characterized in that, The dynamic auxiliary variable is updated according to the following rules: when triggered, the dynamic auxiliary variable is updated to the product of the current composite measurement error and the reset proportional coefficient, and the larger value is taken compared with the strictly positive definite lower bound; when not triggered, the dynamic auxiliary variable is updated to the value after linear decay according to the decay coefficient, and the larger value is taken compared with the strictly positive definite lower bound.

6. The method for distributed secondary control triggered by a dynamic event with preset time convergence according to claim 1, characterized in that, The time-varying gain is applied simultaneously to the integrator inputs of both the voltage recovery channel and the current averaging channel, enabling the voltage recovery error and the current averaging error to converge within a preset convergence time, and the convergence time is independent of the initial system conditions.

7. A dynamically triggered distributed secondary control device with preset time convergence, applied to a DC microgrid, characterized in that, include: The local measurement module is used to acquire the local terminal voltage and output current of each distributed generation unit in each sampling period, and to calculate the weighted current. The time-varying gain calculation module is used to calculate the time-varying gain based on the current time and preset parameters. The time-varying gain is determined by the secondary control activation time, the preset convergence time, the scaling exponent and the upper bound of saturation. The dual-layer dynamic event triggering module is used to calculate the composite measurement error and determine whether to trigger communication based on the dual-layer dynamic event triggering mechanism consisting of the state triggering layer and the energy triggering layer. If triggered, the local weighted current information is sent to neighboring nodes and the local held value is updated; otherwise, the held value sent last time is maintained. The secondary control protocol module is used to introduce the time-varying gain into the secondary control protocol and construct a voltage correction quantity consisting of a voltage recovery channel and a current sharing channel, wherein the time-varying gain acts on the integrator input of both the voltage channel and the current channel simultaneously. The local control interface module is used to send the voltage correction amount to the local control layer, combine it with the droop control output to generate a corrected voltage reference value, drive each distributed generation unit to restore the terminal voltage to the rated value within a preset convergence time and distribute the load current according to the droop coefficient ratio. In the dual-layer dynamic event triggering module: The state triggering layer is configured as follows: define a neighbor inconsistency metric, introduce a logarithmic preset time decay function to make the state triggering threshold monotonically decrease with the preset time process; introduce an idle factor determined by the relaxation coefficient and the idle counter, increase the triggering threshold when the idle counter accumulates to a set value, and decrease the triggering threshold when the idle counter is cleared; and construct the state triggering conditions by combining dynamic auxiliary variables and inconsistency coupling coefficient. The energy triggering layer is configured to: define the cumulative error energy, accumulate the composite measurement error according to the sampling period, couple the energy threshold with the time-varying gain, and introduce the historical triggering frequency ratio determined by the cumulative triggering number to construct the energy triggering condition; The dual-layer dynamic event triggering module integrates the state triggering layer and the energy triggering layer to form a combined event triggering condition. The distributed generation unit will trigger communication when it meets any of the triggering conditions.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the preset time convergence dynamic event-triggered distributed secondary control method as described in any one of claims 1 to 6.

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