A low-pass-filtered droop frequency-voltage control method based on linear active disturbance rejection

Abstract

The present application relates to the technical field of off-grid frequency and voltage control of micro-grid energy storage converter, and particularly relates to a low-pass filter droop frequency and voltage control method based on linear active disturbance rejection. The technical scheme comprises the following steps: constructing a droop control architecture containing a low-pass filter link, introducing a low-pass filter into the traditional active-frequency droop control loop and reactive-voltage droop control loop respectively; constructing a linear active disturbance rejection controller for secondary frequency and voltage control, taking frequency deviation and voltage deviation as inputs. The present application effectively suppresses the initial frequency change rate, realizes the difference-free adjustment of frequency and voltage, overcomes the difference adjustment limitation of traditional droop control, constructs a hierarchical control architecture for high-frequency disturbance fast suppression and low-frequency disturbance accurate compensation, and balances the dynamic response speed and steady-state control accuracy; the control method has low dependence on system model accuracy, and significantly improves the disturbance rejection ability and operation stability under complex working conditions.

Description

Technical Field

[0001] This invention relates to the field of off-grid frequency and voltage regulation control technology for microgrid energy storage converters, and particularly to a low-pass filter droop frequency and voltage regulation control method based on linear active disturbance rejection. Background Technology

[0002] Microgrids, as a power supply mode that enables efficient integration and localized consumption of distributed power sources, demonstrate significant advantages in improving power supply reliability and promoting the utilization of renewable energy. In islanded operation, microgrids operate independently of the main power grid, relying on internal distributed power sources and energy storage devices to maintain system voltage and frequency stability. However, with the integration of high proportions of renewable energy sources such as wind and solar power through power electronic inverters, microgrid systems exhibit significant low inertia and weak damping characteristics, making frequency stability a particularly prominent issue. Compared to traditional synchronous generator systems with large-inertia rotating equipment, inverter-based microgrids lack inherent inertial response capabilities. During sudden load changes or fluctuations in renewable energy output, the system frequency is prone to rapid drops or rises, potentially triggering protection mechanisms and causing power outages.

[0003] Droop control, as the core strategy for primary frequency and voltage regulation in microgrid energy storage converters, simulates the power-frequency-static characteristics of synchronous generators. This allows the inverter to automatically adjust its output frequency based on active power deviation and its output voltage amplitude based on reactive power deviation, enabling multi-unit parallel operation without interconnection communication. This control method is simple in structure and highly reliable, and has been widely used in practical engineering. However, traditional droop control is essentially proportional control. Its fixed droop coefficient determines the relationship between power distribution accuracy and steady-state voltage and frequency deviations: increasing the droop coefficient improves power distribution accuracy but leads to increased steady-state frequency and voltage deviations, reducing power quality; decreasing the droop coefficient reduces steady-state deviation but weakens the system's dynamic response capability, easily triggering prolonged transient oscillations during load changes. Furthermore, traditional droop control only achieves primary frequency and voltage regulation, which is differential regulation and cannot eliminate steady-state deviations, making it difficult to meet the stringent power quality requirements of isolated microgrids.

[0004] To address the aforementioned limitations of traditional droop control, scholars both domestically and internationally have conducted extensive research on improvements. One approach involves introducing virtual inertial control technology. By connecting a differential element or bandpass filter in parallel within the power control loop, the inertial response characteristics of a synchronous generator are simulated to suppress the initial rate of frequency change. While this method improves system dynamic performance, the selection of parameters lacks theoretical guidance and struggles to simultaneously address the suppression requirements of disturbances across different frequency bands. Another approach employs a secondary frequency and voltage regulation strategy, using algorithms such as integral controllers or sliding mode control to compensate for frequency and voltage deviations, achieving error-free regulation. However, integral control has a slow dynamic response and is prone to parameter coupling problems when working in conjunction with droop control; while sliding mode control offers better robustness, its inherent chattering phenomenon may excite unmodeled dynamics in the system, affecting control quality. More critically, none of the above methods address the unified estimation and compensation of internal uncertainties and external disturbances within the control system, failing to construct a systematic disturbance rejection control framework, making it difficult to achieve high-quality frequency and voltage regulation under complex operating conditions. Therefore, this application proposes a low-pass filter droop frequency modulation and voltage regulation control method based on linear active disturbance rejection. Summary of the Invention

[0005] The purpose of this invention is to address the existing challenge in the art of how to effectively enhance system inertia and damping, improve the ability to suppress internal parameter perturbations and external power disturbances, and achieve error-free frequency and voltage regulation of droop control while retaining its structural simplicity. This invention proposes a low-pass filter droop frequency and voltage regulation control method based on linear active disturbance rejection.

[0006] The technical solution of this invention: A low-pass filter droop frequency modulation and voltage regulation control method based on linear active disturbance rejection, comprising the following steps:

[0007] A droop control architecture with a low-pass filter is constructed. Low-pass filters are introduced into the traditional active-frequency droop control loop and reactive-voltage droop control loop respectively. The low-pass filter is used to perform frequency domain decomposition on the frequency deviation signal. The high-frequency disturbance component is allocated to the virtual inertial link to simulate the inertial characteristics of the synchronous generator and suppress the initial rate of frequency change. The low-frequency component is allocated to the droop control link for steady-state power regulation.

[0008] A linear active disturbance rejection controller for secondary frequency and voltage regulation is constructed. With frequency deviation and voltage deviation as inputs, the system lumped disturbance caused by load abrupt changes and distributed power output fluctuations is estimated and dynamically compensated in real time through a linear extended state observer. Combined with the deviation signal after low-pass filtering, additional power regulation commands are generated in the linear state error feedback law.

[0009] Optionally, in the droop control architecture containing a low-pass filter, the control expression for the active-frequency loop is:

[0010] The control expression for the reactive-voltage loop is:

[0011] in, Output control commands representing angular frequency, Represents the rated angular frequency. This represents a voltage output control command. Represents the rated operating voltage. Represents the differential operator, This is the active power droop coefficient. This is the reactive power droop factor. This is the cutoff angular frequency of the low-pass filter connected in series with the active power loop. This is the cutoff angular frequency of the low-pass filter connected in series with the reactive power loop. Given a reference value for active power, Given a reactive power reference value, The actual output active power calculated by the power calculation module. The actual output reactive power calculated by the power calculation module. The system's rated angular frequency, This is the system's rated voltage.

[0012] Optionally, the linear active disturbance rejection controller includes a linear extended state observer and a linear state error feedback control law, whose state equation and error feedback law are as follows:

[0013]

[0014] The control law is:

[0015]

[0016] in, For the output estimate of the controlled object, The derivative value of the output of the controlled object, The estimated value of the lumped disturbance of the controlled object. , , Represent , and The first-order differential, , and For the gain parameters of the linearly extended state observer, The gain coefficient of the controlled object. , This represents the gain coefficient of the linear state error feedback unit in a linear active disturbance rejection controller. This represents the actual output of the controlled object. As the reference input signal, The control value after compensation, This represents the error between the actual output of the controlled object and the estimated output.

[0017] Optionally, the linear active disturbance rejection control model of the active-frequency loop is constructed in the following manner:

[0018] By performing an inverse Laplace transform on the closed-loop transfer function of the low-pass filter droop control active loop, we can transform it into the standard form of a second-order system, thus obtaining the lumped disturbance of the active-frequency loop. and active-frequency loop control gain coefficient :

[0019]

[0020] in,

[0021]

[0022]

[0023] in, Represents the actual output of the controlled object. , These represent the first and second derivatives of the output, respectively. Indicates external disturbance. This represents the active-frequency loop control gain coefficient. For active-frequency loop control variables, The virtual inertia and damping coefficient are obtained after the equivalent transformation of low-pass filter droop control. The time constant of the active power low-pass filter. This is the actual angular frequency of the system. This represents the simulated moment of inertia of the system.

[0024] Optionally, the linear active disturbance rejection control model of the reactive power-voltage loop is constructed in the following manner:

[0025] By performing an inverse Laplace transform on the closed-loop transfer function of the low-pass filter droop control reactive power loop, it is transformed into the standard form of a second-order system, yielding the lumped disturbance of the reactive power-voltage loop. and control gain :

[0026]

[0027] in,

[0028]

[0029]

[0030] in, For reactive power-voltage loop control variables, This represents the reactive power-voltage loop control gain coefficient. The virtual inertia is the result of the equivalent transformation for low-pass filtering and droop control. This represents the damping coefficient after the equivalent transformation of low-pass filter droop control. The time constant of the reactive power low-pass filter. This is the actual output voltage of the system.

[0031] Optionally, the gain parameter of the linearly extended state observer , , Based on the observer bandwidth The tuning process satisfies the following relationship:

[0032] , , ;

[0033] The gain coefficient of the linear state error feedback in the linear active disturbance rejection controller and Based on controller bandwidth Damping ratio The tuning process satisfies the following relationship:

[0034] , .

[0035] Optionally, the cutoff frequency of the low-pass filter and the observer bandwidth of the linear active disturbance rejection controller are tuned in tandem according to the disturbance frequency characteristics.

[0036] Optionally, the active-frequency loop and reactive-voltage loop adopt a decoupled design architecture, with low-pass filter droop control parameters and linear active disturbance rejection controller parameters configured independently, and the actual output active power calculated by the power calculation module. The actual output reactive power calculated by the power calculation module It is used for independent adjustment and coordinated optimization of frequency and voltage.

[0037] Compared with the prior art, this application includes at least one of the following beneficial technical effects:

[0038] By introducing a low-pass filter in the droop control, the frequency deviation signal is decomposed in the frequency domain, and high-frequency disturbances are responded to by a virtual inertial element. This effectively simulates the inertial characteristics of a synchronous generator, suppresses the initial rate of frequency change, and makes up for the lack of inertial support in traditional droop control.

[0039] By combining linear active disturbance rejection control with low-pass filter droop control, the system's lumped disturbances are estimated and compensated in real time through an extended state observer, eliminating steady-state deviations in frequency and voltage, and overcoming the inherent limitations of traditional droop control as a proportional control in terms of differential regulation.

[0040] By coordinating the design of the low-pass filter cutoff frequency and the observer bandwidth of the active disturbance rejection controller, a hierarchical response is achieved that enables rapid suppression of high-frequency transient disturbances and accurate compensation of low-frequency steady-state disturbances, thus balancing dynamic response speed and steady-state control accuracy.

[0041] Linear active disturbance rejection control has low dependence on the accuracy of the system model, can effectively suppress internal parameter perturbations and external power disturbances, and significantly enhances the system's disturbance rejection capability and operational stability under complex operating conditions.

[0042] The controller parameters adopt a bandwidth tuning method, and the active-frequency loop and reactive-voltage loop are decoupled, which reduces the difficulty of parameter coordination and facilitates its application in actual energy storage converters.

[0043] This invention enhances system inertia and damping by introducing a low-pass filter into droop control, effectively suppressing the initial rate of frequency change. By combining linear active disturbance rejection control (ADRC) with low-pass filtered droop control, it achieves error-free frequency and voltage regulation, overcoming the limitations of traditional droop control with its inherent error regulation. Through the coordinated design of the low-pass filter and ADRC parameters, a hierarchical control architecture is constructed that rapidly suppresses high-frequency disturbances and accurately compensates for low-frequency disturbances, balancing dynamic response speed and steady-state control accuracy. The control method has low dependence on system model accuracy, significantly improving disturbance rejection capability and operational stability under complex operating conditions. Attached Figure Description

[0044] Figure 1 This is a block diagram of the low-pass filter droop control.

[0045] Figure 2 Diagram of LADRC control model;

[0046] Figure 3 LADRC control block diagram;

[0047] Figure 4 Here is the block diagram for the droop control of the Pf low-pass filter;

[0048] Figure 5 This is a block diagram of a low-pass filter droop frequency modulation control based on linear active disturbance rejection;

[0049] Figure 6 Here is the block diagram for the QU low-pass filter droop control.

[0050] Figure 7 This is a block diagram of a QU low-pass filter droop voltage regulation control based on linear active disturbance rejection;

[0051] Figure 8 A comparison chart of the output frequencies of the proposed droop control and the traditional droop control;

[0052] Figure 9 A comparison chart of the active power output of the proposed droop control and the traditional droop control.

[0053] Figure 10 A comparison chart of the output voltages of the proposed droop control and the traditional droop control;

[0054] Figure 11 This is a comparison chart of reactive power mutation compensation tracking. Detailed Implementation

[0055] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0056] In this embodiment, the present invention proposes a low-pass filter droop frequency modulation and voltage regulation control method based on linear active disturbance rejection. The method is described in detail below.

[0057] Step 1: Construct droop control based on low-pass filtering

[0058] 1.1 Active / Reactive Power Droop Control (LPF). Existing traditional droop control is an open-loop proportional control, which only simulates the primary frequency and voltage regulation characteristics of a synchronous generator and lacks inertia characteristics. In practical applications, a low-pass filter (LPF) is added to the front end of the droop control to filter out higher-order terms in the instantaneous power, improving system robustness. The transfer function of the low-pass filter is:

[0059]

[0060] In the formula: Represents the differential operator, This is the cutoff angular frequency of the low-pass filter.

[0061] Based on the transfer function of the low-pass filter, the droop control expression after adding the low-pass filter is as follows:

[0062]

[0063] In the formula: Output control commands representing angular frequency, Represents the rated angular frequency. This represents a voltage output control command. Represents the rated operating voltage. Represents the differential operator, This is the active power droop coefficient. This is the reactive power droop factor. This is the cutoff angular frequency of the low-pass filter connected in series with the active power loop. This is the cutoff angular frequency of the low-pass filter connected in series with the reactive power loop. Given a reference value for active power, Given a reactive power reference value, The actual output active power calculated by the power calculation module. The actual output reactive power calculated by the power calculation module. The system's rated angular frequency, This is the system's rated voltage. The low-pass filter droop control block diagram is shown below. Figure 1 As shown.

[0064] in, and The calculation formula is:

[0065]

[0066] In the formula , , , These are the voltage and current values ​​transformed from the three-phase abc coordinate system to the dq axis coordinate system.

[0067] Step 2: Construct LADRC frequency and voltage regulation control considering system disturbances

[0068] Step 2.1 Establishment of the second-order linear active disturbance rejection control model. A linear active disturbance rejection controller (LADRC) is established using a linear extended state observer and linear state error feedback. Its control structure is as follows: Figure 2 , As the reference input signal, This represents the actual output of the controlled object. For the output estimate of the controlled object, The derivative value of the output of the controlled object, An estimate of the lumped disturbance of the controlled object. Additionally, It is the gain coefficient of the controlled object. is the compensated control value, and e is the error between the actual output and the estimated output of the controlled object; , and For linearly extended state observer gain parameters.

[0069] Under normal circumstances, Represented as a concentrated disturbance, the time-domain expression of the controlled object can be expressed as:

[0070]

[0071] Where y represents the actual output of the controlled object. , These represent the first and second derivatives of the output, respectively. Indicates external disturbance. Indicates time, This represents the control input gain coefficient. Indicates control input;

[0072] The LESO model can be represented as:

[0073]

[0074] in, For the output estimate of the controlled object, The derivative value of the output of the controlled object, The estimated value of the lumped disturbance of the controlled object. , , Represent , and The first derivative;

[0075] According to equation (5), the state equation of LESO can be expressed as follows:

[0076]

[0077] Taking the Laplace transform of equation (6) yields:

[0078] in, This represents the state vector estimated by the linearly extended state observer. , , The Laplace transform of ] Represents the differential operator, Indicates the control value after compensation Laplace transform, The Laplace transform of the actual output y of the controlled object. This indicates the gain of the controlled object.

[0079] Based on state estimation, the principle of LESF construction can be derived as follows:

[0080]

[0081] In the formula, This represents the compensated control value. and These are all gain coefficients of the Linear State Error Feedback (LSEF) in a Linear Active Disturbance Rejection Controller (LADRC), and are all undetermined parameters.

[0082] Combining equations (7) and (8), we can obtain:

[0083]

[0084] in, Indicates control value Laplace transform, Represents the Laplace transform of the reference input signal. This represents the Laplace transform of the actual output y of the controlled object. This represents the transfer function of the feedback channel. This indicates the gain of the controlled object.

[0085]

[0086]

[0087] Combining equations (4), (9), (10), and (11), we can obtain the control block diagram of the linear active disturbance rejection controller as follows: Figure 3 As shown. Figure 3 In this context, K represents the control gain coefficient. and This refers to the control element in a linear active disturbance rejection controller.

[0088] observe Figure 3 From the control model in the paper, it can be found that by simply replacing the controlled object with a low-pass filter droop control algorithm and using the system frequency / voltage of the low-pass droop control as the input feedback, a feedback control structure including the comprehensive disturbance can be derived. Based on the estimation of the output and the total disturbance, LSEF can achieve feedback compensation for the controlled variable, thereby enabling the output to quickly track the input reference value without deviation. According to equations (5) and (8), its differential equation is derived as follows:

[0089]

[0090] and combined Figure 3 Therefore, the closed-loop transfer function of the control system can be derived as follows:

[0091]

[0092] The parameters are set as follows:

[0093]

[0094] In the formula, For controller bandwidth; is the damping ratio.

[0095] The characteristic equation of the Linear Extended State Observer (LESO) can be obtained as follows:

[0096]

[0097] Selecting the ideal characteristic equation Then there is

[0098]

[0099] In the formula, This represents the observer bandwidth.

[0100] Step 2.2 Frequency and Voltage Regulation Control Based on LADRC. In actual energy storage system operation, the control system inevitably contains certain harmonics. The calculated instantaneous output power contains harmonic components with a minimum frequency twice the power frequency. These harmonic components ultimately cause output distortion, affecting power quality. Therefore, adding a first-order filter (Low Pass Filter, LPF) after the power signal to handle the high-frequency harmonic effects yields the actual active power output.

[0101]

[0102] In the formula, This represents the collected active power on the grid side. The actual output active power calculated by the power calculation module; Let be the time constant of the active power low-pass filter. When: in formula (2) , , This represents the virtual active power damping control parameters. This represents the virtual inertia control parameters, which can be... Figure 1 The block diagram of the low-pass filter droop control in Pf is transformed into the following: Figure 4 The structure shown.

[0103] Figure 4 middle Indicates virtual active power damping control parameters, and These represent virtual inertia control parameters, all of which are undetermined control parameters, based on... Figure 4The control block diagram of the low-pass filter drooping active power loop can be used to obtain the closed-loop transfer function expression of the system output frequency with respect to the given active power, output active power and rated frequency, as shown in equation (18).

[0104]

[0105] In the formula, Output control commands representing angular frequency, The actual angular frequency of the system With input signal The transfer function between them Angular frequency With input signal The transfer function between them.

[0106]

[0107] Performing an inverse Laplace transform on equation (18) and rearranging it, we obtain equation (20):

[0108]

[0109] Based on the lumped disturbance of the active-frequency loop in LADRC in step 2.1 The expression can be simplified to:

[0110]

[0111] In the formula, the lumped disturbance of the active-frequency loop The expression is:

[0112]

[0113] Active-frequency loop control gain coefficient The expression is:

[0114]

[0115] Active-frequency loop control variables for:

[0116]

[0117] in, These are the virtual active power damping control parameters after the equivalent transformation of low-pass filter droop control. The time constant of the active power low-pass filter. This is the actual angular frequency of the system. This represents the virtual inertia control parameter.

[0118] Therefore, the linear active disturbance rejection control block diagram for the Pf low-pass filter droop can be obtained as follows: Figure 5 As shown, Figure 5 K1 is the active-frequency loop gain coefficient. This is the forward path control element for the active power LADRC. As shown in the derivation process in step 2.1, the feedback control loop in the active power LADRC is:

[0119]

[0120]

[0121] Based on the above control block diagram, the closed-loop transfer function of the active power control loop (LPF) second-order linear active disturbance rejection control is:

[0122]

[0123] in, express and The transfer function between them express and The transfer function between them express and The transfer function between them.

[0124]

[0125]

[0126]

[0127]

[0128] in, , , , , , for Polynomial coefficients.

[0129]

[0130]

[0131]

[0132]

[0133]

[0134]

[0135] In the formula and Both are the gain of LSEF in the active power LADRC; , and The gain parameter is the linear extended state observer in the active power LADRC.

[0136] Similarly, voltage regulation control based on LADRC can be established. According to equation (3), the instantaneous reactive power of the system can be calculated. Due to the influence of system power exchange and harmonics, the reactive power also needs to be filtered out by a low-pass filter to remove higher-order terms.

[0137]

[0138] In the formula, This represents the collected grid-side reactive power. This represents the actual output reactive power calculated by the power calculation module; Let be the time constant of the reactive power low-pass filter. When: in formula (2) , , This represents the virtual reactive power damping control parameters. This represents the control parameters after the equivalent transformation of the low-pass filter droop control. The block diagram of the Qu low-pass filter droop control can be transformed into, for example, the control parameters after the equivalent transformation. Figure 6 The structure shown. According to... Figure 6 The control block diagram of the LPF drooping reactive power loop can be used to obtain the closed-loop transfer function expression of the system output voltage with respect to the given reactive power, output reactive power and rated voltage, as shown in equation (29).

[0139]

[0140] In the formula AC output voltage With input The transfer function between them AC output voltage With input The transfer function between them.

[0141]

[0142] Performing an inverse Laplace transform on the above equation and rearranging, we obtain:

[0143]

[0144] Based on the expression for the lumped disturbance of the reactive-voltage loop in LADRC, the above equation can be simplified to:

[0145]

[0146] In the formula, the lumped disturbance of the reactive power-voltage loop The expression is:

[0147]

[0148] Reactive-voltage loop control gain coefficient The expression is:

[0149]

[0150] Reactive power-voltage loop control variables The expression is:

[0151]

[0152] Therefore, the linear active disturbance rejection control block diagram for the Qu low-pass filter droop can be obtained as follows: Figure 7 As shown. Figure 7 K2 is the reactive-voltage loop LADRC gain coefficient. This is the forward path control element for reactive power LADRC. This is the feedback control element in the reactive power LADRC. From the derivation process in step 2.1, we can see that:

[0153]

[0154]

[0155] Based on the above control block diagram, the closed-loop transfer function of the reactive power control loop (LPF) second-order linear active disturbance rejection control is obtained as follows:

[0156]

[0157] in, Indicates the output voltage of the energy storage system. express and The transfer function, express and The transfer function, express and The transfer function.

[0158]

[0159]

[0160]

[0161]

[0162] in, , , , , , for Polynomial coefficients.

[0163]

[0164]

[0165]

[0166]

[0167]

[0168]

[0169] In the formula and Both are gains of LSEF in reactive power LADRC; , and This refers to the gain parameter of the linearly extended state observer in the reactive power LADRC.

[0170] A system incorporating energy storage and off-grid operation was built in the Matlab / Simulink platform. System parameters are shown in Table 1. The power characteristics of the energy storage converter under different operating conditions in response to load power variations were simulated and analyzed.

[0171] Table 1 Simulation parameters of superconducting-electrochemical hybrid energy storage converter

[0172] parameter numerical values Energy storage battery voltage 800V DC bus voltage 600V DC bus capacitor 6.75mF VSC switching frequency 2kHz VSC filter inductor 0.25mH VSC filter capacitor 0.3mF Rated AC voltage RMS value 220V Initial power of load 20kW, 10kVar

[0173] The microgrid system initially operates in islanded mode with a load of 30kW / 10kVar. After 2 seconds, the active power of the load suddenly increases to 30kW, which remains for 1 second before being disconnected, returning to the initial load state. Figure 8 The frequency waveforms of the energy storage converter output are compared when the proposed droop control and the conventional droop control are used.

[0174] Depend on Figure 8It is known that when the system load increases suddenly, the traditional droop control strategy cannot achieve frequency error adjustment, so the system output frequency also drops sharply to 49.5Hz, and there is also continuous fluctuation. Such frequency abrupt change and fluctuation will cause great damage to the sensitive load in the system. However, the proposed low-pass filter droop control based on LADRC only has a very small frequency fluctuation, less than 0.1Hz, and recovers to 50Hz within 50ms.

[0175] Tracking of sudden changes in system active power, such as Figure 9 As shown in the figure, the proposed droop control can achieve a smaller active power compensation steady-state error compared to traditional droop control.

[0176] To verify the voltage regulation performance of the proposed control under reactive power disturbance, a comparative simulation experiment was conducted: the initial reactive power load was set to 10 kVar, which was then stepped to 20 kVar after 2 seconds and maintained for 1 second before recovering. Figure 10 A comparison of the voltage amplitude waveforms output by the energy storage converter under the proposed droop control and the traditional droop control is presented. As shown in the figure, when the system reactive power changes abruptly, the output voltage of the traditional droop control system drops instantaneously to 309.2V and exhibits continuous fluctuations; while the output voltage fluctuation of the proposed droop control system is less than 0.1V and recovers within 50ms. Figure 11 A comparison of reactive power mutation compensation tracking is presented, by Figure 11 It can be seen that the proposed droop control can achieve better compensation effect and has smaller steady-state error.

[0177] This invention addresses the inherent shortcomings of isolated microgrids, such as inertia loss, poor frequency stability, and insufficient dynamic response and steady-state deviation in traditional droop control due to the high proportion of renewable energy integration. It proposes a low-pass filter-based droop frequency and voltage regulation control method based on linear active disturbance rejection. First, by introducing a low-pass filter into the traditional droop control loop, the frequency deviation signal is decomposed in the frequency domain. This allows high-frequency disturbance components to be responded to by a virtual inertial element, simulating the inertia characteristics of a synchronous generator, thereby suppressing the initial rate of frequency change and enhancing the inertia and damping of the system during dynamic processes. Second, to address the steady-state deviation that still exists after primary frequency and voltage regulation, a secondary regulator based on linear active disturbance rejection control is constructed. A linear extended state observer is used to estimate and compensate for the lumped disturbances caused by load abrupt changes and renewable energy fluctuations in real time. Combined with linear state error feedback, additional power commands are generated to achieve error-free frequency and voltage regulation. The method of this invention constructs a hierarchical collaborative control architecture that rapidly suppresses high-frequency disturbances and accurately compensates for low-frequency steady-state disturbances by coordinating the cutoff frequency of the low-pass filter and the observer bandwidth of the active disturbance rejection controller. This not only retains the advantages of the traditional droop control structure in its simplicity, but also effectively solves the bottlenecks of its lack of inertia and steady-state deviation. It significantly improves the dynamic response speed, steady-state control accuracy and robustness of the system under complex disturbances, and ultimately provides technical support with both strong anti-disturbance capability and high power quality for the safe and stable operation of high-proportion new energy microgrids in islanded state.

[0178] The above specific embodiments are merely several optional embodiments of the present invention. Based on the technical solutions of the present invention and the relevant teachings of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

Claims

1. A low-pass filter droop frequency modulation and voltage regulation control method based on linear active disturbance rejection, characterized in that, Includes the following steps: A droop control architecture with a low-pass filter is constructed. Low-pass filters are introduced into the traditional active-frequency droop control loop and reactive-voltage droop control loop respectively. The low-pass filter is used to perform frequency domain decomposition on the frequency deviation signal. The high-frequency disturbance component is allocated to the virtual inertial link to simulate the inertial characteristics of the synchronous generator and suppress the initial rate of frequency change. The low-frequency component is allocated to the droop control link for steady-state power regulation. A secondary frequency and voltage regulation controller based on linear active disturbance rejection control is constructed. With frequency deviation and voltage deviation as inputs, the system lumped disturbance caused by load change and distributed power output fluctuation is estimated and dynamically compensated in real time through a linear extended state observer. Combined with the deviation signal after low-pass filtering, an additional power regulation command is generated in the linear state error feedback law. In the droop control architecture containing a low-pass filter, the control expression for the active-frequency loop is: The control expression for the reactive power-voltage loop is: in, Output control commands representing angular frequency, Represents the rated angular frequency. This represents a voltage output control command. Represents the rated operating voltage. Represents the differential operator, This is the active power droop coefficient. This is the reactive power droop factor. This is the cutoff angular frequency of the low-pass filter connected in series with the active power loop. This is the cutoff angular frequency of the low-pass filter connected in series with the reactive power loop. Given a reference value for active power, Given a reactive power reference value, The actual output active power calculated by the power calculation module. The actual output reactive power calculated by the power calculation module. The system's rated angular frequency, This is the system's rated voltage; The linear active disturbance rejection controller includes a linear extended state observer and a linear state error feedback control law, and its state equation and error feedback law are as follows: The control law is: ,in, For the output estimate of the controlled object, The derivative value of the output of the controlled object, The estimated value of the lumped disturbance of the controlled object. , , Represent , and The first-order differential, , and For the gain parameters of the linearly extended state observer, The gain coefficient of the controlled object. , This represents the gain coefficient of the linear state error feedback unit in a linear active disturbance rejection controller. This represents the actual output of the controlled object. As the reference input signal, The control value after compensation, This represents the error between the actual output of the controlled object and the estimated output.

2. The low-pass filter droop frequency modulation and voltage regulation control method based on linear active disturbance rejection according to claim 1, characterized in that, The linear active disturbance rejection control model of the active-frequency loop is constructed in the following way: By performing an inverse Laplace transform on the closed-loop transfer function of the low-pass filter droop control active loop, we can transform it into the standard form of a second-order system, thus obtaining the lumped disturbance of the active-frequency loop. and active-frequency loop control gain coefficient : in, in, Represents the actual output of the controlled object. , These represent the first and second derivatives of the output, respectively. Indicates external disturbance. This represents the active-frequency loop control gain coefficient. For active-frequency loop control variables, The virtual inertia and damping coefficient are obtained after the equivalent transformation of low-pass filter droop control. The time constant of the active power low-pass filter. This is the actual angular frequency of the system. This represents the simulated moment of inertia of the system.

3. The low-pass filter droop frequency and voltage modulation control method based on linear active disturbance rejection according to claim 2, characterized in that, The linear active disturbance rejection control model of the reactive power-voltage loop is constructed in the following way: By performing an inverse Laplace transform on the closed-loop transfer function of the low-pass filter droop control reactive power loop, it is transformed into the standard form of a second-order system, yielding the lumped disturbance of the reactive power-voltage loop. and control gain : in, in, For reactive power-voltage loop control variables, This represents the reactive power-voltage loop control gain coefficient. The virtual inertia is the result of the equivalent transformation for low-pass filtering and droop control. This represents the damping coefficient after the equivalent transformation of low-pass filter droop control. The time constant of the reactive power low-pass filter. This is the actual output voltage of the system.

4. The low-pass filter droop frequency and voltage modulation control method based on linear active disturbance rejection according to claim 1, characterized in that, The gain parameter of the linearly extended state observer , , Based on observer bandwidth The tuning process satisfies the following relationship: , , ； The gain coefficient of the linear state error feedback in the linear active disturbance rejection controller and Based on controller bandwidth Damping ratio The tuning process satisfies the following relationship: ， 。 5. The low-pass filter droop frequency and voltage modulation control method based on linear active disturbance rejection according to claim 1, characterized in that, The cutoff frequency of the low-pass filter and the observer bandwidth of the linear active disturbance rejection controller are tuned in tandem according to the disturbance frequency characteristics.

6. The low-pass filter droop frequency and voltage modulation control method based on linear active disturbance rejection according to claim 1, characterized in that, The active-frequency loop and reactive-voltage loop adopt a decoupled design architecture, with low-pass filter droop control parameters and linear active disturbance rejection controller parameters configured independently, respectively. The actual output active power is calculated by the power calculation module. The actual output reactive power calculated by the power calculation module It is used for independent adjustment and coordinated optimization of frequency and voltage.

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