Direct current micro-grid control method and system based on fixed time disturbance observer

Abstract

The invention discloses a direct-current micro-grid control method and system based on a fixed-time disturbance observer, and belongs to the field of power grid control. A fixed-time secondary controller based on the disturbance observer is designed in a single direct-current bus direct-current micro-grid in the presence of disturbance; an unknown external disturbance caused by a power supply and a load is observed by using a disturbance observer, and the unknown disturbance observed by the disturbance observer is adjusted by using a secondary controller, so that the direct current micro-grid system can realize observation and suppression of the unknown disturbance within a fixed time, and control targets of voltage adjustment and current sharing are completed. The anti-interference capability and the dynamic performance of the system are improved, and the stability of the system is ensured.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of power grid control, and more particularly relates to a DC micro-grid control method and system based on a fixed-time disturbance observer. BACKGROUND

[0002] In recent years, with the reform of the energy structure system, micro-grid technology has also entered a new stage of development. DC micro-grid accelerates the integration of renewable energy with its high efficiency, high reliability and scalability, and is increasingly recognized. Renewable energy such as wind power and photovoltaic has the characteristics of randomness and intermittency. Under the framework of DC micro-grid, high proportion of new energy access will bring many unknown disturbances, and changes in the load on the DC bus will also cause system instability, resulting in system instability and slow response speed. Therefore, the stability and fast response requirements of the DC micro-grid system have been widely concerned.

[0003] In order to realize systematic control, the hierarchical control structure of the DC micro-grid is widely used. Droop control is responsible for local voltage and current control to meet operation and stability requirements. The introduction of secondary control solves the problem of voltage control deviation. The introduction of tertiary control realizes the energy distribution and optimization planning of the micro-grid unit. Among them, the realization of voltage regulation and current sharing of micro-grid based on secondary control is a research hotspot at present, but how to design the controller to realize active disturbance rejection and ensure the fast convergence of the system is a difficult problem to be solved. Therefore, it is particularly important for the stable operation of the DC micro-grid to design a kind of secondary controller which can not only realize the suppression of disturbance, but also ensure the fast convergence of the system. SUMMARY

[0004] In view of the above defects or improvement needs of the prior art, the present application provides a DC micro-grid control method and system based on a fixed-time disturbance observer, thereby solving the technical problem that the existing secondary controller is difficult to realize active disturbance rejection and fast convergence.

[0005] To achieve the above purpose, according to the first aspect of the present application, a DC micro-grid control method based on a fixed-time disturbance observer is provided, comprising: S1, in the communication network of the DC micro-grid, for any DC converter i, collecting the and of its neighbor node j, and transferring the locally saved and to the neighbor node j; and are the time intermediate variable and the average current error observation value of the i-th DC converter, and are the time intermediate variable and the average current error observation value of the j-th DC converter; S2, updating the local , , and based on the acquired and by using the preset time-distributed observer; S3, repeating steps S1 and S2 until and are iteratively converged to values that no longer change; S4, updating based on the following formula by using the fixed-time disturbance observer to update based on the updated :

[0006] wherein is the derivative of , and are the observed values of and predicted by the disturbance observer, and are the current error and voltage disturbance at the i-th DC converter, respectively; and are the observed values of and predicted by the disturbance observer, and are the voltage error and load disturbance at the i-th DC converter, respectively; , is a sign function; is the inductance of the line on which the i-th DC converter is connected, N is the total number of DC converters, and represent the admittance load and the capacitance value connected to the DC bus, respectively, , is the droop coefficient corresponding to the i-th DC converter, is the resistance of the line on which the i-th DC converter is connected, is the equilibrium point of the current of the i-th DC converter; the observer gain , , , > 0, and , ; is a switching function based on the observation error, and is represented as follows:

[0007] The observation error is calculated based on the difference between and and the difference between and ; S5, repeating step S4 until both converge to values that no longer change; S6, determining the expected value of the DC bus voltage and the steady-state unit current based on the micro-grid operating state , collecting the bus voltage signal and the output current signal , obtaining the bus voltage error and the unit current error of the i-th DC converter , and calculating the comprehensive error of the i-th DC converter based on the bus voltage error and the unit current error ; S7, based on the convergence value of and the comprehensive error , using a fixed-time secondary controller to calculate the secondary control signal ; S8, repeating steps S6 and S7 until the comprehensive error converges to the target interval, and based on the secondary control signal obtained at the time of convergence controlling the i-th DC converter.

[0008] According to any one of the above DC micro-grid control methods based on a fixed-time disturbance observer, the expression of the fixed-time secondary controller is:

[0009] wherein, is the secondary control signal, and the controller gain , , is the voltage compensation component under system disturbance calculated based on the convergence values of and .

[0010] According to any one of the above DC micro-grid control methods based on a fixed-time disturbance observer, composed of a disturbance compensation term and an adaptive adjustment term; wherein the disturbance compensation term is based on and ​a main component of voltage compensation under system disturbance calculated by convergence value; an adaptive adjustment term is constructed based on observation error and comprehensive error upper bound for adjusting compensation strength, the adaptive adjustment term is used to offset the influence caused by observation error of the fixed time disturbance observer, and the compensation strength is positively related to the comprehensive error upper bound.

[0011] According to any one of the DC micro-grid control methods based on the fixed time disturbance observer, is calculated based on the following formula:

[0012] the adaptive term is:

[0013] wherein, is a set comprehensive error switching value, is a comprehensive error upper bound.

[0014] According to any one of the DC micro-grid control methods based on the fixed time disturbance observer, the comprehensive error upper bound is updated based on the following formula:

[0015] wherein, is a derivative of is a normal number, , , is a Euclidean norm of .

[0016] According to any one of the DC micro-grid control methods based on the fixed time disturbance observer, the observation error is calculated based on the following formula:

[0017] wherein, is an observation error, and is a preset weight coefficient.

[0018] According to any one of the DC micro-grid control methods based on the fixed time disturbance observer, the local and are updated based on the following formula:

[0019] wherein, and are intermediate variables, is a derivative of derivative of the , denotes a set of neighbor nodes of the i-th DC converter, denotes a weight between the i-th DC converter and the j-th DC converter, is a preset upper bound of convergence time, t is an update time, is a current error of the i-th DC converter at the update time.

[0020] According to a second aspect of the present application, a fixed-time disturbance observer-based DC microgrid control system is provided, comprising: a disturbance observer unit configured to perform: S1, in the communication network of the DC microgrid, for any DC converter i, collecting the and of its neighbor node j, and transmitting the locally saved and to the neighbor node j; and are respectively a time intermediate variable and an average current error observation value of the i-th DC converter, and are respectively a time intermediate variable and an average current error observation value of the j-th DC converter; S2, using a preset time-distributed observer, updating the local and based on the obtained and ; ; S3, repeating steps S1 and S2 until and both converge to values that no longer change; S4, using a fixed-time disturbance observer, updating based on the following formula to update based on the updated :

[0021] wherein, derivative of the , and and are respectively observation values of and predicted by the disturbance observer, and are respectively a current error and a voltage disturbance at the i-th DC converter; and ​For the prediction of the perturbation observer and The observed values, and These are the voltage error and load disturbance at the i-th DC-DC converter, respectively; , It is a symbolic function; Let N be the inductive reactance of the line containing the i-th DC-DC converter, and N be the total number of DC-DC converters. and These represent the admittance load and capacitance value connected to the DC bus, respectively. , Let be the droop coefficient corresponding to the i-th DC-DC converter. Let be the resistance of the line containing the i-th DC-DC converter. This is the current balance point of the i-th DC-DC converter; Observer Gain , , , >0, and , ; It is a switching function based on observation error, expressed as follows:

[0022] The observation error is based on a preset threshold. and The difference between and and The difference between them is calculated. The secondary control unit is used to perform: S5, Repeat step S4 until... All converge to a point where the value no longer changes; S6, Determine the expected value of the DC bus voltage based on the microgrid's operating status. and steady-state unit current Acquire bus voltage signal and output current signal Calculate the bus voltage error The unit current error of the i-th DC-DC converter And based on bus voltage error and unit current error The overall error of the i-th DC-DC converter is calculated. ; S7, based on Convergence value and overall error The secondary control signal is calculated using a fixed-time secondary controller. ; S8. Repeat steps S6 and S7 until the combined error is reached. Converging to the target interval, based on the secondary control signal obtained during convergence. Control the i-th DC-DC converter.

[0023] According to a third aspect of the present invention, an electronic device is provided, comprising: a computer-readable storage medium and a processor; The computer-readable storage medium is used to store executable instructions; The processor is configured to read executable instructions stored in the computer-readable storage medium and execute the method as described in the first aspect.

[0024] According to a fourth aspect of the invention, a computer-readable storage medium is provided, the computer-readable storage medium storing computer instructions for causing a processor to perform the method as described in the first aspect.

[0025] According to a fifth aspect of the invention, a computer program product is provided, comprising a computer program or instructions that, when executed by a processor, implement the method as described in the first aspect.

[0026] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects: By designing a fixed-time secondary controller based on a disturbance observer in a single-DC bus DC microgrid under disturbance conditions, the disturbance observer is used to observe unknown external disturbances caused by the power supply and load. The secondary controller is used to adjust the unknown disturbances observed by the disturbance observer, enabling the DC microgrid system to observe and suppress unknown disturbances within a fixed time, and to achieve the control objectives of voltage regulation and current sharing. This improves the system's disturbance rejection capability and dynamic performance, and ensures the system's stability.

[0027] As a preferred approach, an adaptive compensation term for system disturbances is introduced into the secondary controller. This can compensate for the interference caused by system disturbances to the system voltage and current, and further improve the anti-interference capability of DC microgrid control methods and systems.

[0028] As a preferred solution, the adaptive compensation is designed to consist of a disturbance compensation term and an adaptive adjustment term. The disturbance compensation term provides the main voltage compensation component under system disturbance, while the adaptive adjustment term provides the voltage compensation gain value based on the observation error. This enhances the secondary controller's ability to compensate for unknown disturbances while avoiding overcompensation and chattering. Attached Figure Description

[0029] Figure 1A schematic diagram of the control architecture of a DC microgrid system provided in an embodiment of the present invention; Figure 2 A schematic diagram of a DC microgrid control method provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of a DC microgrid control system provided in an embodiment of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0031] This invention provides a DC microgrid control method based on a fixed-time disturbance observer, comprising: S1, In the communication network of a DC microgrid, for any DC converter i, the data of its neighboring node j are collected. and and save locally and Pass it to neighbor node j; and Let be the time intermediate variable and the average current error observation value of the i-th DC-DC converter, respectively. and These are the time intermediate variable and the average current error observation value of the j-th DC-DC converter, respectively; S2, using a pre-defined time-distributed observer, based on the acquired... , , and Update local and ; S3, Repeat steps S1 and S2 until... and All iterations converge until the value no longer changes; S4, using a fixed-time perturbation observer, updates based on the following formula. Based on the updated renew :

[0032] in, for The derivative, and These are the predictions of the disturbance observer. and The observed values, and These are the current error and voltage disturbance at the i-th DC-DC converter, respectively; and For the prediction of the perturbation observer and The observed values, and These are the voltage error and load disturbance at the i-th DC-DC converter, respectively; , It is a symbolic function; Let N be the inductive reactance of the line containing the i-th DC-DC converter, and N be the total number of DC-DC converters. and These represent the admittance load and capacitance value connected to the DC bus, respectively. , Let be the droop coefficient corresponding to the i-th DC-DC converter. Let be the resistance of the line containing the i-th DC-DC converter. This is the current balance point of the i-th DC-DC converter; Observer Gain , , , >0, and , ; It is a switching function based on observation error, expressed as follows:

[0033] The observation error is based on a preset threshold. and The difference between and and The difference between them is calculated. S5, Repeat step S4 until... All converge to a point where the value no longer changes; S6, Determine the expected value of the DC bus voltage based on the microgrid's operating status. and steady-state unit current Acquire bus voltage signal and output current signal Calculate the bus voltage error The unit current error of the i-th DC-DC converter And based on bus voltage error and unit current error The overall error of the i-th DC-DC converter is calculated. ; S7, based on Convergence value and overall error The secondary control signal is calculated using a fixed-time secondary controller. ; S8. Repeat steps S6 and S7 until the combined error is reached. Converging to the target interval, based on the secondary control signal obtained during convergence. Control the i-th DC-DC converter.

[0034] Specifically, this embodiment of the invention first establishes a control model for a single-DC-bus DC microgrid and proposes control objectives. Among them, such as... Figure 1 As shown, the DC microgrid system adopts a hierarchical control structure. Considering a microgrid with multiple DC converters connected in parallel to a single DC bus, for the first... A DC-DC converter, the DC power supply voltage is , and These represent the output voltage and current, respectively. This indicates the voltage of the DC bus. Each DC-DC converter performs droop control and secondary control, and the reference output voltage of the DC-DC converter is... ,in This represents the expected value of the DC bus voltage. The droop coefficient is... This is the secondary control signal for the DC-DC converter, used to restore the reference voltage to the desired value, resulting in the reference voltage. The input voltage and current are controlled by a dual-loop control system. Voltage and current closed-loop PI controls generate PWM signals that control the DC-DC converter's on / off states. Because the dual-loop control allows the converter's output voltage to quickly track its reference value, i.e. Then the output voltage can be expressed as:

[0035] Considering the resistance of transmission lines The existence of [something] allows one to obtain [something]. The bus voltage can be further expressed as:

[0036] The above equations reveal the relationship between the voltage bus and the local secondary control signal, laying the foundation for constructing a DC microgrid model. The following section discusses... Figure 1 The DC microgrid system shown is modeled as follows:

[0037] in, , The inductive reactance of the line where DC converter i is located. and These represent the admittance load and capacitance value connected to the DC bus, respectively. To further simplify the system and introduce disturbances, we set... and The equilibrium points are respectively and ,in The equilibrium point is the reference value. According to the current relationship, we can obtain Define the total voltage error. and the Current error of each converter After adding a disturbance, the system can be represented as:

[0038] in , , , , , and For unknown disturbances in the system that need to be observed by an observer, This can be viewed as a disturbance in the voltage caused by fluctuations in the input of new energy power. It can be viewed as a load disturbance caused by load changes. Dimension is , This represents the number of DC-DC converters.

[0039] For a single-DC bus DC microgrid under disturbances, precise voltage regulation and current distribution cannot be achieved within the convergence time. Therefore, the actual control objectives of the DC microgrid system are: 1) to maintain the DC bus voltage within a sufficiently small neighborhood of the target value under disturbances; and 2) to maintain the current distribution between converters within a sufficiently small neighborhood of the target ratio, i.e.:

[0040]

[0041] in, To shorten the convergence time, For the desired scaling parameter, and It is an infinitesimal normal number related to the perturbation.

[0042] Based on this, embodiments of the present invention provide a disturbance observer to calculate the observed values ​​of unknown disturbances at the DC bus and load end.

[0043] Specifically, such as Figure 2As shown, in order to estimate the average output current error, a preset time-distributed observer is first used for each DC-DC converter to observe the average current error. It should be noted that the time-distributed observer here can be any existing observer capable of observing the average current error over a fixed time period; this embodiment of the invention does not specifically limit this. In some embodiments, the first... The average current error observation value of each DC-DC converter unit is The preset time-distributed observer can be designed as follows:

[0044] in, For the i-th DC-DC converter, for The derivative, As an intermediate variable, And observer gain For positive integers, Indicates the first The set of neighboring nodes of each converter. This represents the weight between the i-th DC-DC converter and the j-th DC-DC converter. Let be the average current error observation value of the i-th DC-DC converter. It can be represented as:

[0045] Where t is the update time. To update the current error of the DC-DC converter at time i, It is a symbolic function. Set an upper bound for the convergence time of the observer. Based on the definition of time convergence, this observer can... Convergence is achieved within a certain time frame, i.e. It is possible Observations were made within a certain timeframe.

[0046] To observe unknown disturbances, this invention proposes a fixed-time disturbance observer based on an extended state observer. This observer can observe disturbances within a fixed time period and improve the dynamic performance of the system, enabling rapid and accurate estimation of unknown disturbances caused by voltage fluctuations and load disturbances that are difficult to measure directly in the operation of a DC microgrid. The design concept of this disturbance observer is to treat disturbances as implicit and extended states of the system, and to construct an extended state model using voltage, current, and neighboring node information. Let... The fixed-time perturbation observer can then be designed as follows:

[0047] in, for The derivative, The initial value is 0; and These are the predictions of the disturbance observer. and The observed values, and These are the current error and voltage disturbance at the i-th DC-DC converter, respectively; and For the prediction of the perturbation observer and The observed values, and Let be the voltage error and load disturbance at the i-th DC-DC converter, respectively. This is the gain of the observer. ,in The observer gain, which is greater than the upper bound of the perturbation, can be a value preset in simulation and experiment. Select... and , It is a sufficiently small positive value, and , . It is a switching function based on observation error, expressed as follows:

[0048] in The observation error is based on a preset threshold. and The difference between and and The difference between them is calculated. In some embodiments, the observation error can be calculated based on the following formula:

[0049] in, For observation error, and These are preset weighting coefficients.

[0050] When the absolute value of the observation error is greater than the above threshold, then When the observation error is less than this threshold, then Because this perturbation observer incorporates a fixed-time term. Based on the definition of fixed-time convergence, this observer can converge within a fixed time. The inner convergence is achieved, that is It is possible Observations were made within a certain timeframe.

[0051] It can be seen that the observation error feedback term of the perturbation observer is designed as follows: The form of a double power function structure, containing higher-order power terms. With lower power terms The combination of higher-order terms plays a dominant role when the error is large, rapidly reducing large deviations, while lower-order terms dominate when the error is small, ensuring a smooth transition and avoiding oscillations as the system approaches zero. This design allows the observation error to decrease rapidly throughout the convergence process and remain stable in the terminal region, achieving fixed-time convergence. Fixed-time means that regardless of the initial error, the observation error can converge to near zero within a pre-set time, independent of initial conditions, thus providing a deterministic response speed for the system. Secondly, to further improve the dynamic performance and robustness of the perturbation observation, this embodiment introduces a time-varying gain function into the fixed-time perturbation observer. and symbolic function terms .in, Used for dynamic adjustment of the observer gain, when the initial system error is large. Setting it to 1 provides higher-order terms to accelerate error convergence; when the error drops below the threshold, Setting it to 0 provides a low-order term to prevent high-frequency chattering and noise amplification. To suppress the upper bound effect of unknown disturbances and ensure the boundedness of observation errors, this embodiment of the invention introduces a sign function term in the design of the fixed-time disturbance observer. As an anti-disturbance compensation mechanism, the gain coefficient of this term is adjusted so that its amplitude is greater than the upper limit of the disturbance, thereby achieving active compensation for unknown disturbances. The term consistently generates a correction force in a constant direction when observation errors exist, enabling the system to overcome disturbances and maintain convergence towards zero under arbitrary initial conditions. In summary, this invention introduces a double-power function structure, a switching function, and a sign function term into the fixed-time disturbance observer, ensuring fast convergence and system robustness.

[0052] The specific steps for perturbation observation based on the aforementioned preset time-distributed observer and fixed-time perturbation observer include: In the communication network of a DC microgrid, for any DC converter i, the data of its neighboring node j are collected. and and save locally and Pass it to neighbor node j; Using the aforementioned time-distributed observer, based on the acquired , , and Update local and Specifically, this can be combined with local information. and and collected and The information is used to calculate the error, and the result is obtained. and And then update and ; Repeat the above two steps until... and The iterations converge until the value no longer changes, thus obtaining... The convergence value is used for calculation by the fixed-time perturbation observer; Fixed-time disturbance observer based on Including parameters such as observer gain, it is possible to construct and calculate ; where, when the switching function When it is 1, by Superscript terms dominate; when switching functions When it is 0, by Superscript item is dominant; Repeat the previous step until... The iterations converge until the value no longer changes.

[0053] The fixed-time perturbation observer designed above can be used in time The system achieves convergence within a short time frame. Its fixed-time design enhances the dynamic performance of the system, enabling it to quickly track changes in disturbances and suppress their impact on the system through the controller.

[0054] Subsequently, the expected value of the DC bus voltage is determined based on the microgrid's operating status. and steady-state unit current Acquire bus voltage signal and output current signal Calculate the bus voltage error The unit current error of the i-th DC-DC converter And based on bus voltage error and unit current error The overall error of the i-th DC-DC converter is calculated. .

[0055] Among them, for the first For each DC-DC converter, establish a combined error of bus voltage error and unit current error:

[0056] in , . Unit current, Let be the steady-state unit current, where and All are provided by three levels of control signals.

[0057] Based on the output of the perturbation observer The convergence value and the above-mentioned comprehensive error By utilizing the observed values ​​of voltage error and current error from a fixed-time two-stage controller, and combining the combined voltage and current errors, a two-stage control signal is calculated to compensate for the aforementioned errors caused by system disturbances. It should be noted that any fixed-time secondary controller can be used to calculate the secondary control signal here, and this embodiment of the invention does not specifically limit this. By repeating the above steps of error calculation and secondary control signal calculation, the comprehensive error is calculated. The convergence is achieved to the target interval, thus enabling the use of the secondary control signal obtained during convergence. Control the i-th DC-DC converter to achieve active disturbance rejection and ensure rapid system convergence.

[0058] In some embodiments, due to the presence of disturbances, disturbance rejection design can be incorporated into the secondary control to further enhance disturbance rejection capability. For example... Figure 2 As shown, a fixed-time two-stage controller can be designed as follows:

[0059] in, Let i be the inductive reactance of the line containing the i-th DC-DC converter, and let the controller gain be... , N is the total number of DC-DC converters. and These represent the admittance load and capacitance value connected to the DC bus, respectively. , Let be the droop coefficient corresponding to the i-th DC-DC converter. Let be the resistance of the line containing the i-th DC-DC converter. This is the current balance point of the i-th DC-DC converter; For based on and The voltage compensation component under system disturbance is obtained by calculating the convergence value, which is used to compensate for the interference caused by system disturbance to system voltage and current.

[0060] As can be seen, the aforementioned secondary controller mainly consists of two parts: a fixed-time feedback term and an adaptive compensation term. and The two terms are fixed-time feedback terms, consistent with the design principle of the disturbance observer. They achieve rapid convergence when the error is large and smooth approximation when the error is small through a combination of low-order and high-order powers, ensuring that the system state converges within the predetermined time bound. This is because a fixed-time term is added to this secondary controller. Based on the definition of fixed-time convergence, the designed fixed-time two-stage controller can achieve convergence within a fixed time. If convergence is achieved, then combining the previous perturbation observer can... If convergence is achieved within a certain time, then the system can achieve convergence within a fixed time. It converges within a certain time frame, that is: .

[0061] Adaptive compensation term This is a voltage compensation component calculated based on voltage and load disturbances observed by a disturbance observer, used to compensate for the interference caused by system disturbances to system voltage and current. Through effective control and active compensation of the upper bound of the disturbance, the comprehensive error is ensured to converge to a small neighborhood within a fixed time, achieving fast and deterministic bus voltage recovery and output current sharing control.

[0062] In other embodiments, to further optimize the compensation performance of the secondary controller for system disturbances, It can consist of a disturbance compensation term and an adaptive adjustment term; wherein, the disturbance compensation term is based on and The voltage compensation principal component under system disturbance is obtained by calculating the convergence value. The adaptive adjustment term is constructed based on the observation error and the comprehensive error upper bound used for online adjustment of the compensation intensity. The adaptive adjustment term is used to offset the influence caused by the observation error of the fixed-time disturbance observer, and the compensation intensity is positively correlated with the comprehensive error upper bound. Specifically, the adaptive adjustment term dynamically modifies the compensation gain according to the error. When the observation error is large, the voltage compensation gain value automatically increases, thereby enhancing the compensation capability of the secondary controller for unknown disturbances. When the observation error approaches zero, the voltage compensation gain value gradually decreases to avoid overcompensation and chattering.

[0063] In some embodiments, It is calculated based on the following formula:

[0064] Adaptive terms for:

[0065] in, The set comprehensive error switching value, This is the upper bound of the overall error.

[0066] In other embodiments, the comprehensive error upper bound The update can be based on the following formula:

[0067] in, for The derivative, The initial value is 0. For positive integers, , for The Euclidean norm.

[0068] In summary, the method provided by this invention, by designing a fixed-time secondary controller based on a disturbance observer in a single-DC bus DC microgrid under disturbance conditions, utilizes the disturbance observer to observe unknown external disturbances caused by the power supply and load, and uses the secondary controller to adjust for the unknown disturbances observed by the disturbance observer. This enables the DC microgrid system to observe and suppress unknown disturbances within a fixed time, and to achieve the control objectives of voltage regulation and current sharing, thereby improving the system's disturbance rejection capability and dynamic performance, and ensuring the system's stability.

[0069] The DC microgrid control system based on a fixed-time disturbance observer provided by the present invention will be described below. The DC microgrid control system based on a fixed-time disturbance observer described below can be referred to in correspondence with the DC microgrid control method based on a fixed-time disturbance observer described above.

[0070] This invention provides a DC microgrid control system based on a fixed-time disturbance observer, such as... Figure 3 As shown, it includes: Disturbance observation unit 310 is used to perform: S1, In the communication network of a DC microgrid, for any DC converter i, the data of its neighboring node j are collected. and and save locally and Pass it to neighbor node j; and Let be the time intermediate variable and the average current error observation value of the i-th DC-DC converter, respectively. and These are the time intermediate variable and the average current error observation value of the j-th DC-DC converter, respectively; S2, using a pre-defined time-distributed observer, based on the acquired... , , and Update local and ; S3, Repeat steps S1 and S2 until... and All iterations converge until the value no longer changes; S4, using a fixed-time perturbation observer, updates based on the following formula. Based on the updated renew :

[0071] in, for The derivative, and These are the predictions of the disturbance observer. and The observed values, and These are the current error and voltage disturbance at the i-th DC-DC converter, respectively; and For the prediction of the perturbation observer and The observed values, and These are the voltage error and load disturbance at the i-th DC-DC converter, respectively; , It is a symbolic function; Let N be the inductive reactance of the line containing the i-th DC-DC converter, and N be the total number of DC-DC converters. and These represent the admittance load and capacitance value connected to the DC bus, respectively. , Let be the droop coefficient corresponding to the i-th DC-DC converter. Let be the resistance of the line containing the i-th DC-DC converter. This is the current balance point of the i-th DC-DC converter; Observer Gain , , , >0, and , ; It is a switching function based on observation error, expressed as follows:

[0072] The observation error is based on a preset threshold. and The difference between and and The difference between them is calculated. The secondary control unit 320 is used to perform: S5, Repeat step S4 until... All converge to a point where the value no longer changes; S6, Determine the expected value of the DC bus voltage based on the microgrid's operating status. and steady-state unit current Acquire bus voltage signal and output current signal Calculate the bus voltage error The unit current error of the i-th DC-DC converter And based on bus voltage error and unit current error The overall error of the i-th DC-DC converter is calculated. ; S7, based on Convergence value and overall error The secondary control signal is calculated using a fixed-time secondary controller. ; S8. Repeat steps S6 and S7 until the combined error is reached. Converging to the target interval, based on the secondary control signal obtained during convergence. Control the i-th DC-DC converter.

[0073] The system provided in this invention, by designing a fixed-time secondary controller based on a disturbance observer in a single DC bus DC microgrid under disturbance conditions, utilizes the disturbance observer to observe unknown external disturbances caused by the power supply and load, and uses the secondary controller to adjust for the unknown disturbances observed by the disturbance observer. This enables the DC microgrid system to observe and suppress unknown disturbances within a fixed time, and to achieve the control objectives of voltage regulation and current sharing, thereby improving the system's disturbance rejection capability and dynamic performance, and ensuring the system's stability.

[0074] Based on any of the above embodiments, the expression for the fixed-time secondary controller is:

[0075] in, For secondary control signals, controller gain , , For based on and The voltage compensation component under system disturbance is obtained by calculating the convergence value.

[0076] Based on any of the above embodiments It consists of a disturbance compensation term and an adaptive adjustment term; wherein, the disturbance compensation term is based on and The convergence value is used to calculate the voltage compensation principal component under system disturbance; the adaptive adjustment term is constructed based on the observation error and the comprehensive error upper bound for online adjustment of the compensation intensity. The adaptive adjustment term is used to offset the influence caused by the observation error of the fixed-time disturbance observer, and the compensation intensity is positively correlated with the comprehensive error upper bound.

[0077] Based on any of the above embodiments It is calculated based on the following formula:

[0078] Adaptive terms for:

[0079] in, The set comprehensive error switching value, This is the upper bound of the overall error.

[0080] Based on any of the above embodiments, the comprehensive error upper bound is... The update is based on the following formula:

[0081] in, for The derivative, For positive integers, , for The Euclidean norm.

[0082] Based on any of the above embodiments, the observation error is calculated using the following formula:

[0083] in, For observation error, and These are preset weighting coefficients.

[0084] Based on any of the above embodiments, the local and It is updated based on the following formula:

[0085] in, and As an intermediate variable, for The derivative, , Let represent the set of neighboring nodes of the i-th DC-DC converter. This represents the weight between the i-th DC-DC converter and the j-th DC-DC converter. As a preset upper bound for the convergence time, t is the update time. This is to update the current error of the DC-DC converter at time i.

[0086] This invention provides an electronic device, including: a computer-readable storage medium and a processor; The computer-readable storage medium is used to store executable instructions; The processor is configured to read executable instructions stored in the computer-readable storage medium and execute the method as described in any of the above embodiments.

[0087] This invention provides a computer-readable storage medium storing computer instructions that cause a processor to perform the method described in any of the above embodiments.

[0088] This invention provides a computer program product, including a computer program or instructions, which, when executed by a processor, implement the method described in any of the above embodiments.

[0089] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A fixed-time perturbation observer-based DC microgrid control method, characterized in that, Comprising: S1, in the communication network of the DC microgrid, for any DC converter i, collecting its neighbor node j's and and delivering the locally saved and to the neighbor node j; and are the time intermediate variable and the average current error observation value of the i-th DC converter, respectively, and are the time intermediate variable and the average current error observation value of the j-th DC converter, respectively. S2, using the preset time-distributed observer, updating the local , , and and ;​ S3, repeating steps S1 and S2 until and both iteratively converge to values that no longer change; S4, update using the fixed-time disturbance observer based on the following equation to be based on the updated update : wherein, is derivative of and are the observed values of and predicted by the disturbance observer, and are the current error and voltage disturbance at the ith DC converter, respectively; and are the observed values of and predicted by the disturbance observer, and are the voltage error and load disturbance at the ith DC converter, respectively; , is a sign function; is the inductance of the line where the ith DC converter is connected, N is the total number of DC converters, and represent the admittance load and the capacitance value connected to the DC bus, respectively, , is the droop coefficient corresponding to the ith DC converter, is the resistance of the line where the ith DC converter is connected, is the equilibrium point of the current of the ith DC converter; observer gain , , , > 0, and , ; is an observation error-based switching function, expressed as follows: For a preset threshold value, the observation error is calculated based on the difference between and and the difference between and ; S5, repeat step S4 until both converge to values that no longer change; S6, determining a desired value of the DC bus voltage according to the micro-grid operation state and a steady-state unit current , collecting a bus voltage signal and an output current signal , obtaining a bus voltage error and a unit current error of the i-th DC converter , and calculating a comprehensive error of the i-th DC converter based on the bus voltage error and the unit current error ;​ S7, based on the convergence value and the integrated error a secondary control signal is calculated using a fixed-time secondary controller ; S8, repeat steps S6 and S7 until the integrated error converges to the target interval, based on the secondary control signal obtained at the time of convergence control the i-th DC converter.

2. The fixed-time perturbation observer-based DC microgrid control method of claim 1, wherein, The expression of the fixed-time secondary controller is: wherein, is a secondary control signal, controller gain , , is a voltage compensation component under system disturbance calculated based on and convergent values.

3. The fixed-time perturbation observer-based DC microgrid control method of claim 2, wherein, comprises a disturbance compensation term and an adaptive adjustment term; wherein the disturbance compensation term is calculated based on and a main voltage compensation component under system disturbance, and the adaptive adjustment term is constructed based on the observation error and an integrated error upper bound for adjusting the compensation strength, the adaptive adjustment term is used to offset the influence caused by the observation error of the fixed-time disturbance observer, and the compensation strength is positively related to the integrated error upper bound.

4. The fixed-time perturbation observer-based DC microgrid control method of claim 3, wherein, is calculated based on the following formula: Adaptive term Is: wherein is a set overall error switching value, is an overall error upper bound.

5. The fixed-time perturbation observer-based DC microgrid control method of claim 4, wherein, comprehensive error upper bound is updated based on the following equation: wherein is derivative of is a normal number, , is Euclidean norm.

6. The fixed-time perturbation observer-based DC microgrid control method of any one of claims 1 to 5, wherein, The observation error is calculated based on the following formula: wherein, is an observation error, and is a preset weight coefficient.

7. The fixed-time perturbation observer-based DC microgrid control method of claim 1, wherein, Local And are updated based on the following equation: wherein, and is an intermediate variable, is derivative of , denotes a set of neighbor nodes of the i-th DC converter, denotes a weight between the i-th DC converter and the j-th DC converter, is a preset upper bound of convergence time, t is an updating time, is a current error of the i-th DC converter at the updating time.

8. A fixed-time perturbation observer-based DC microgrid control system, characterized in that, Comprising: A disturbance observation unit configured to perform: S1, in the communication network of the DC microgrid, for any DC converter i, collecting its neighbor node j's and and delivering the locally saved and to the neighbor node j; and are the time intermediate variable and the average current error observation value of the i-th DC converter, respectively, and are the time intermediate variable and the average current error observation value of the j-th DC converter, respectively; S2, using a preset time-distributed observer, updating the local , , and and ;​ S3, repeating steps S1 and S2 until and both iteratively converge to values that no longer change; S4, update using the fixed-time disturbance observer based on the following equation to be based on the updated update : wherein, is the derivative of and are the observed values of and predicted by the disturbance observer, and are the current error and voltage disturbance at the ith DC converter, respectively; and are the observed values of and predicted by the disturbance observer, and are the voltage error and load disturbance at the ith DC converter, respectively; , is a sign function; is the inductance of the line where the ith DC converter is connected, N is the total number of DC converters, and represent the admittance load and the capacitance value connected to the DC bus, respectively, , is the droop coefficient corresponding to the ith DC converter, is the resistance of the line where the ith DC converter is connected, is the equilibrium point of the current of the ith DC converter; observer gain , , , > 0, and , ; is an observation error-based switching function, expressed as follows: For a preset threshold value, the observation error is calculated based on the difference between and and the difference between and ; A secondary control unit configured to perform: S5, repeat step S4 until both converge to values that no longer change; S6, determining a desired value of the DC bus voltage according to the micro-grid operating state and a steady-state unit current , acquiring a bus voltage signal and an output current signal , obtaining a bus voltage error and a unit current error of the i-th DC converter , and calculating a comprehensive error of the i-th DC converter based on the bus voltage error and the unit current error ;​ S7, based on the convergence value and the integrated error a secondary control signal is calculated using a fixed-time secondary controller ; S8, repeat steps S6 and S7 until the integrated error converges to the target interval, based on the secondary control signal obtained at the time of convergence control the i-th DC converter.

9. An electronic device, comprising: Comprising: A computer readable storage medium and a processor; The computer readable storage medium is configured to store executable instructions; The processor is configured to read the executable instructions stored in the computer readable storage medium, and execute the method according to any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The computer readable storage medium stores computer instructions, and the computer instructions are configured to make the processor execute the method according to any one of claims 1-7.

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