AC / DC power distribution network coupling node state linearization reconstruction control method and device

Abstract

The invention relates to an AC / DC power distribution network coupling node state linearization reconstruction control method and device. The method comprises the following steps: step 1, constructing a dynamic equation under a rotating coordinate system; step 2, linear decoupling of nonlinear AC / DC coupling nodes is realized, and a new energy state is selected based on a port Hamiltonian theory; 3, the unknown uncertainty of the system in the rotating coordinate system is represented in a lumped mode; 4, duty ratio related items in the polynomial obtained through derivation are selected as control input, and other items obtained through derivation are lumped into another unknown uncertainty disturbance lumped item; step 5, constructing a linearized standard state space model; step 6, determining a control reference state; and 7, designing a corresponding control law, and further completing feedback linearization-based AC / DC power distribution network coupling node state reconstruction control. The transient regulation time is shortened by more than 90%, the total harmonic distortion rate of the voltage is reduced by more than half, and the dynamic performance and the electric energy quality of the system are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of AC / DC distribution network state reconfiguration technology, and relates to a method and device for AC / DC distribution network coupled node state reconfiguration control, and more particularly to a method and device for AC / DC distribution network coupled node state linearization reconfiguration control. Background Technology

[0002] Currently, my country's traditional power system is evolving into a new type of power system that is clean, low-carbon, safe, controllable, flexible, and efficient. The development of medium- and low-voltage AC / DC distribution networks can promote the consumption of clean energy, achieve flexible electricity use, improve energy efficiency, and reduce energy consumption and emissions.

[0003] With the continuous development of new power systems, distributed resources with high uncertainty, represented by distributed photovoltaics, electric vehicles, and small-scale energy storage, are being connected to the distribution network on a large scale, and the distribution network is evolving from a single AC form to a hybrid AC / DC structure.

[0004] However, existing state reconstruction methods struggle to accurately capture the dynamic characteristics of AC / DC coupled nodes when faced with the random fluctuations and uncertainties of distributed energy sources in AC / DC distribution networks. They also exhibit poor adaptability to time-varying loads and complex topologies, failing to effectively address rapid changes in system operating conditions and impacting the accuracy and real-time performance of state reconstruction. Furthermore, when dealing with multivariable coupling problems, their decoupling effect is unsatisfactory, and their control precision is low, making independent control of AC / DC coupled nodes difficult. They also lack sufficient anti-interference capabilities, being highly sensitive to noise, measurement errors, and other interference factors in the distribution network, which can easily lead to significant deviations in state reconstruction results and reduce system stability. Moreover, some methods involve complex mathematical models and algorithms, making it difficult to meet the real-time requirements of practical engineering applications.

[0005] Therefore, in order to solve the above-mentioned technical problems, the present invention proposes a method and apparatus for linearizing and reconstructing the state of coupled nodes in AC / DC distribution networks.

[0006] A search revealed no publicly available literature of the same or similar prior art as this invention. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and device for linearizing and reconstructing the state of coupled nodes in AC / DC distribution networks. By analyzing the operating dynamics of the AC / DC coupled node converter and combining coordinate transformation, dynamic equations in a rotating coordinate system are constructed. By combining feedback linearization decoupling theory, the dynamics of the AC side system of the coupled node are reconstructed. The unknown uncertainties of the system in the rotating coordinate system are lumped together, and a linearized standard state space form of the AC / DC coupled node is constructed to achieve high-gain characterization of state deviation.

[0008] The present invention solves its practical problem by adopting the following technical solution: A method for linearizing and reconstructing the state of coupled nodes in an AC / DC distribution network includes the following steps: Step 1: By analyzing the operating dynamics of the AC / DC coupled node converter and combining coordinate transformation, construct the dynamic equations in the rotating coordinate system; Step 2: Based on the dynamic equations obtained in Step 1, the nonlinear AC / DC coupling nodes are linearized and decoupled through nonlinear dynamic averaging and feedback linearization, and a new energy state is selected based on the port Hamiltonian theory. Step 3: Differentiate the new energy state selected in Step 2, select the input-related terms in the polynomial obtained by differentiation as another new power state, and lump the remaining terms obtained by differentiation into the lumped term of unknown uncertainty disturbance. The lumped term represents the unknown uncertainty of the system under the rotating coordinate system. Step 4: Further differentiate the other new power state selected in Step 3, select the duty cycle related terms in the polynomial obtained by differentiation as the control input, and aggregate the remaining terms obtained by differentiation into another unknown uncertainty disturbance aggregate term; Step 5: Combining the new energy state selected in Step 2, the new power state selected in Step 3, the lumped term of unknown uncertainty disturbance selected in Step 3, the control input selected in Step 4, and the lumped term of another unknown uncertainty disturbance selected in Step 4, construct a linearized standard state-space model. Step 6: Based on the standard state-space model constructed in Step 5, directly apply various disturbance observation and feedforward architecture disturbance rejection control methods to determine the control reference state; Step 7: Based on the mathematical model constructed in Steps 5-6, the applied disturbance rejection control method, and the determined reference state, design the corresponding control law, and then complete the state reconfiguration control of the AC / DC distribution network coupled nodes based on feedback linearization.

[0009] Moreover, the specific method of step 1 is as follows: Considering a typical medium-to-low voltage AC / DC coupling node, based on the moving average theory and Park coordinate transformation, the inductor current, capacitor voltage, control signal, and output current of phases a, b, and c of the three-phase AC coupling node are transformed into the dq rotating coordinate system to form a dynamic model, whose dynamic equations can be expressed as follows: Based on the moving average and coordinate transformation theory, the dynamic equation of the AC / DC coupling node can be written as: (1) in, , Let be the inductor currents along the d and q axes, respectively. , The capacitor voltages are on the d-axis and q-axis, respectively. , The output currents for the d and q axes are respectively. , These are the duty cycles for the d and q axes, respectively. , These are the inductance and capacitance values ​​on the AC side, respectively. , f It is the frequency, which is usually considered to be an approximately constant value in medium and low voltage distribution networks.

[0010] Furthermore, the specific steps of step 2 include: (1) Considering the voltage-current nonlinear coupling in formula (1) of step 1, and the difficulty in directly obtaining the voltage-current in formula (1) of step 1 in actual operation. The new energy state is selected based on the port Hamiltonian theory, as shown in formula (2); (2) The derivative of the selected new energy state is calculated based on the relevant variables and their changing relationships in the dynamic model. The derivative expression of the new state is obtained, i.e., formula (3), which lays the foundation for subsequent processing and is more suitable for subsequent linearization and decoupling operations. (2) Differentiation yields: (3) in, , , Let be the new energy states along the d and q axes and their first derivatives with respect to time, respectively.

[0011] Furthermore, the specific steps of step 3 include: To characterize the lumped term of unknown uncertainty disturbances in power dynamics in step 2, these uncertainty factors are lumped together so that they can be considered and addressed in a unified manner in subsequent steps, thereby reducing their impact on the system. Consider the known terms in formula (3) , Select a new state; make: (4) in, , It is the lumped sum of unknown and uncertain disturbances in power dynamics. , These represent another new power state along the d and q axes, respectively; Furthermore, the specific method for step 4 is as follows: Taking the derivatives of the new state selected in step 2 and the other new state introduced in step 3, we obtain the derivative expression of the new state (5): By combining existing dynamic models and relevant variable information, a detailed expression for the system changes under the new state is derived, providing a key basis for the subsequent construction of the standard state-space form.

[0012] (5) in, , Another new power state for the d and q axes, respectively. , The first derivative with respect to time.

[0013] Furthermore, the specific steps of step 5 include: (1) The standard state-space form for constructing key AC / DC coupling nodes and converters is as follows: (6) in, , These are the control inputs for the d and q axes, respectively. , These are another unknown perturbation along the d and q axes, respectively; (2) Further organize and construct the standard state-space form of the key AC / DC coupling nodes and converters, as shown in formula (7), to transform the complex nonlinear AC / DC coupling node system into a relatively simple and easy-to-handle linearized standard state-space model: (7) Furthermore, the specific steps of step 6 include: A nonlinear disturbance observer, expressed as in formula (8), is used to generate corresponding control signals based on the observed system state and disturbance conditions, thereby achieving effective control of the AC / DC coupling node and improving system performance. (8) in, , , , They are respectively , , , The estimation results, , , , , , , , Let be the intermediate variables of each observer along the d and q axes, and their first derivatives with respect to time. , , , These are the gain coefficients of the observers on the d and q axes, respectively; When the system is stable, the derivatives of each state are 0. Formula (9) is constructed as the control reference state to ensure that the system can operate and adjust according to the predetermined reference state. (9) in, , , , , , These are the reference values ​​for each state along the d and q axes, respectively; Furthermore, the control law in step 7 can be written as: (10) in, , , These are the reference values ​​for each state along the d and q axes, respectively; This control law comprehensively considers information such as system state, reference state, and disturbance observations to generate specific control signals, which are used to drive equipment such as converters in AC-DC coupling nodes, thereby achieving effective regulation and control of the system state to reduce voltage distortion rate and shorten transient settling time.

[0014] A low-voltage AC / DC distribution network coupled node state reconfiguration control device based on feedback linearization, comprising: The sampling module, whose output is connected to the processor, is used to acquire the required current signal in real time. , , and voltage signal , , The actual analog quantity is converted into a digital signal that the processor can directly receive and execute; The processor is used to execute the steps of a low-voltage AC / DC distribution network coupled node state reconfiguration control method based on feedback linearization. The output of the drive module is connected to the AC / DC coupling node model and is used to receive control signals from phases a, b, and c. , , The driving signal is modulated and generated to directly drive steps S1 to S6.

[0015] The storage module is used to store the state reconstruction control method program.

[0016] Advantages and beneficial effects of the present invention: 1. This invention proposes a linearized reconfiguration control method and device for the state of coupled nodes in AC / DC distribution networks. By selecting an energy function as the state variable of the system, it performs coordinate transformation on the original dynamic equations, avoiding direct analysis of the original voltage and current equations containing strong nonlinearity and multivariable cross-coupling terms. This changes the mathematical description of the system and transforms the nonlinear coupled system into a linearly decoupled system model.

[0017] 2. This invention represents various uncertainties, such as distributed power source fluctuations and time-varying loads, as an unknown disturbance in the state equation. By designing a nonlinear disturbance observer to perform online estimation and feedforward compensation of this lumped disturbance, it achieves active suppression of internal and external interferences, solving the technical problem that traditional methods suffer from insufficient anti-interference capability under complex operating conditions, leading to performance degradation or even instability.

[0018] 3. Compared with traditional control methods, the present invention reduces the transient adjustment time by more than 90% and the total harmonic distortion rate of voltage by more than half, significantly improving the dynamic performance and power quality of the system. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the AC / DC coupling node model of the present invention; Figure 2 This is a block diagram of the low-voltage AC / DC distribution network coupled node state reconfiguration control device based on feedback linearization according to the present invention; Figure 3 This is a schematic diagram of the coupling node of a low-voltage AC / DC system in a certain location in Tianjin, according to the present invention. Figure 4 This is a comparison chart of the voltage stability test results of the present invention; Figure 5 This is a schematic diagram of the three-phase voltage performance of the PI control strategy; Figure 6 This is a schematic diagram of the transient performance of three-phase voltage during power surges using a PI control strategy. Figure 7 This is a schematic diagram of the three-phase voltage performance of the control strategy proposed in this invention; Figure 8 This is a schematic diagram of the transient performance of the three-phase voltage during power surges in the control strategy proposed in this invention. Detailed Implementation

[0020] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings: A method for linearizing and reconstructing the state of coupled nodes in an AC / DC distribution network includes the following steps: Step 1: By analyzing the operating dynamics of the AC / DC coupled node converter and combining coordinate transformation, construct the dynamic equations in the rotating coordinate system; The specific method for step 1 is as follows: Considering a typical medium-to-low voltage AC / DC coupling node, based on the moving average theory and Park coordinate transformation, the inductor current, capacitor voltage, control signal, and output current of phases a, b, and c of the three-phase AC coupling node are transformed into the dq rotating coordinate system to form a dynamic model, whose dynamic equations can be expressed as follows: Based on the moving average and coordinate transformation theory, the dynamic equation of the AC / DC coupling node can be written as: (1) in, , Let be the inductor currents along the d and q axes, respectively. , The capacitor voltages are on the d-axis and q-axis, respectively. , The output currents for the d and q axes are respectively. , These are the inductance and capacitance values ​​on the AC side, respectively. , These are the duty cycles for the d and q axes, respectively. , f It is the frequency, which is usually considered to be an approximately constant value in medium and low voltage distribution networks.

[0021] Step 2: Based on the dynamic equations obtained in Step 1, the nonlinear AC / DC coupling nodes are linearized and decoupled through nonlinear dynamic averaging and feedback linearization, and a new energy state is selected based on the port Hamiltonian theory. The specific steps of step 2 include: (1) Considering the voltage-current nonlinear coupling in formula (1) of step 1, and the difficulty in directly obtaining the voltage-current in formula (1) of step 1 in actual operation. Select a new state, as shown in formula (2); (2) Perform a derivative operation on the selected new state. Based on the relevant variables and their changing relationships in the dynamic model, derive the derivative expression of the new state, i.e., formula (3), to lay the foundation for subsequent processing and better adapt to subsequent linearization and decoupling operations: (2) Differentiation yields: (3) in, , , Let be the new energy states along the d and q axes and their first derivatives with respect to time, respectively.

[0022] Step 3: Differentiate the new energy state selected in Step 2, select the input-related terms in the polynomial obtained by differentiation as another new power state, and lump the remaining terms obtained by differentiation into the lumped term of unknown uncertainty disturbance. The lumped term represents the unknown uncertainty of the system under the rotating coordinate system. The specific steps of step 3 include: To characterize the lumped term of unknown uncertainty disturbances in power dynamics in step 2, these uncertainty factors are lumped together so that they can be considered and addressed in a unified manner in subsequent steps, thereby reducing their impact on the system. Consider the known terms in formula (3) , Select a new state; make: (4) in, , It is the lumped sum of unknown and uncertain disturbances in power dynamics. , These represent another new power state for the d and q axes, respectively; Step 4: Further differentiate the other new power state selected in Step 3, select the duty cycle related terms in the polynomial obtained by differentiation as the control input, and aggregate the remaining terms obtained by differentiation into another unknown uncertainty disturbance aggregate term; The specific method for step 4 is as follows: Further differentiating the new state selected in step 2 and the other new power state introduced in step 3, we obtain the derivative expression of the new state (5): By combining existing dynamic models and relevant variable information, a detailed expression for the system changes under the new state is derived, providing a key basis for the subsequent construction of the standard state-space form.

[0023] (5) in, , These are two new power states for the d and q axes, respectively. , The first derivative with respect to time.

[0024] Step 5: Combining the new energy state selected in Step 2, the new power state selected in Step 3, the lumped term of unknown uncertainty disturbance selected in Step 3, the control input selected in Step 4, and the lumped term of another unknown uncertainty disturbance selected in Step 4, construct a linearized standard state-space model. The specific steps of step 5 include: (1) The standard state-space form for constructing key AC / DC coupling nodes and converters is as follows: (6) (2) Further organize and construct the standard state-space form of the key AC / DC coupling nodes and converters, as shown in formula (7), to transform the complex nonlinear AC / DC coupling node system into a relatively simple and easy-to-handle linearized standard state-space model: (7) in, , These are the intermediate control laws for the d and q axes, respectively. , These are another unknown perturbation along the d and q axes, respectively; Step 6: Based on the standard state-space model constructed in Step 5, directly apply various disturbance observation and feedforward architecture disturbance rejection control methods to determine the control reference state; The specific steps of step 6 include: A nonlinear disturbance observer, expressed as in formula (8), is used to generate corresponding control signals based on the observed system state and disturbance conditions, thereby achieving effective control of the AC / DC coupling node and improving system performance. (8) in, , , , They are respectively , , , The estimation results, , , , , , , , Let be the intermediate variables of each observer along the d and q axes, and their first derivatives with respect to time. , , , These are the gain coefficients of the observers on the d and q axes, respectively; When the system is stable, the derivatives of each state are 0. Formula (9) is constructed as the control reference state to ensure that the system can operate and adjust according to the predetermined reference state. (9) in, , , , , , These are the reference values ​​for each state along the d and q axes, respectively; Step 7: Based on the mathematical model constructed in Steps 5-6, the applied disturbance rejection control method, and the determined reference state, design the corresponding control law, and then complete the state reconfiguration control of the AC / DC distribution network coupled nodes based on feedback linearization.

[0025] The control rate in step 7 can be written as: (10) in, , , These are the reference values ​​for each state along the d and q axes, respectively; This control law comprehensively considers information such as system state, reference state, and disturbance observations to generate specific control signals, which are used to drive equipment such as converters in AC-DC coupling nodes, thereby achieving effective regulation and control of the system state to reduce voltage distortion rate and shorten transient settling time.

[0026] The state reconstruction method proposed in this invention achieves linear decoupling of nonlinear AC / DC coupling nodes through nonlinear dynamic averaging and feedback linearization, and lumped-out processing of external unmatched unknown uncertainties. The method was tested on the coupling node of an SM35BH3 2# low-voltage AC / DC system in Tianjin. The system topology is as follows: Figure 3 As shown, the system comprises a 23-node AC bus and a photovoltaic-charging pile DC bus, connected via a bidirectional AC / DC converter. The quantitative comparison results of the proportions of each harmonic are as follows: Figure 4 As shown in the figure, the voltage transient diagram results are as follows: Figures 5-8 As shown. Compared with the dual closed-loop PI control strategy, the proposed control method reduces the voltage distortion law (THD) by more than half and the transient settling time by more than 90%.

[0027] A low-voltage AC / DC distribution network coupled node state reconfiguration control device based on feedback linearization, such as Figure 2 As shown, it includes: The sampling module, whose output is connected to the processor, is used to acquire the required current signal in real time. , , and voltage signal , , The actual analog quantity is converted into a digital signal that the processor can directly receive and execute; The processor is used to execute the steps of a low-voltage AC / DC distribution network coupled node state reconfiguration control method based on feedback linearization. In this embodiment, the sampling methods used by the sampling module include, but are not limited to, voltage divider sampling, isolation amplifier sampling, Hall effect sampling, differential sampling, etc. The output of the drive module is connected to the AC / DC coupling node model and is used to receive control signals from phases a, b, and c. , , The signal is modulated and generated to directly drive S1~S6.

[0028] In this embodiment, the driving methods used by the driving components include, but are not limited to, multi-level modulation, sinusoidal pulse width modulation (SPWM), and space vector pulse width modulation (SVPWM). The storage module is used to store the state reconstruction control method program; like Figure 1 As shown, the AC / DC coupling node model includes: a DC bus connected to the DC bus via a three-phase full-bridge converter, three-phase inductors, and three-phase capacitors. DC side voltage , , These are the control signals for phases a, b, and c, respectively. L and C represent the output-side inductance and capacitance values. , , These are the inductor currents for phases a, b, and c, respectively. , , These are the voltages of the inductors in phases a, b, and c, respectively. , , The output currents are for phases a, b, and c, respectively.

[0029] The working principle of this invention is: At the coupling node of the medium and low voltage AC / DC distribution network, the dynamic operation of the converter is first analyzed and combined with coordinate transformation. Using the moving average and Park coordinate transformation theory, the inductor current, capacitor voltage, control signal and output current of the three-phase AC coupling node are transformed from phases a, b, and c to the d-q rotating coordinate system, and the corresponding dynamic equations are constructed.

[0030] Based on this dynamic equation, nonlinear dynamic averaging and feedback linearization methods are used to linearize and decouple the nonlinear AC / DC coupling node, and a new state is selected. The derivative of the selected new state is then calculated based on the relevant variables and their relationships in the dynamic model, deriving the derivative expression for the new state. This lays the foundation for subsequent processing, making it more suitable for linearization and decoupling operations.

[0031] Meanwhile, considering the unknown uncertainties in power dynamics, these uncertainties are lumped together to introduce new uncertain states, so that these disturbances can be considered and addressed uniformly in subsequent steps, reducing their impact on the system. Furthermore, the derivatives of the selected new states and the new states with introduced uncertainties are differentiated to obtain the derivative expressions for the new states. Combining the existing dynamic model and relevant variable information, detailed expressions for system changes under the new states are derived, thereby constructing a linearized standard state-space model of the key AC / DC coupling nodes and the converter.

[0032] Based on this, various disturbance observation and feedforward architecture-based disturbance rejection control methods are directly applied. A nonlinear disturbance observer is used to generate corresponding control signals based on the observed system state and disturbance conditions, thereby achieving effective control of AC / DC coupling nodes. By determining the control reference state, it is ensured that the system can operate and adjust according to the predetermined reference state. Then, corresponding control laws are designed, comprehensively considering information such as system state, reference state, and disturbance observation values ​​to generate specific control signals to drive equipment such as converters in AC / DC coupling nodes. This achieves effective regulation and control of the system state, reducing voltage distortion rate and shortening transient settling time, thereby improving the voltage stability and dynamic performance of AC / DC distribution network coupling nodes.

[0033] It should be emphasized that the embodiments described in this invention are illustrative rather than limiting. Therefore, this invention includes, but is not limited to, the embodiments described in the specific implementation. Any other implementations derived by those skilled in the art based on the technical solutions of this invention are also within the scope of protection of this invention.

Claims

1. A method for linearizing and reconstructing the state of coupled nodes in an AC / DC distribution network, characterized in that: Includes the following steps: Step 1: By analyzing the operating dynamics of the AC / DC coupled node converter and combining coordinate transformation, construct the dynamic equations in the rotating coordinate system; Step 2: Based on the dynamic equations obtained in Step 1, the nonlinear AC / DC coupling nodes are linearized and decoupled through nonlinear dynamic averaging and feedback linearization, and a new energy state is selected based on the port Hamiltonian theory. Step 3: Differentiate the new energy state selected in Step 2, select the input-related terms in the polynomial obtained by differentiation as another new power state, and lump the remaining terms obtained by differentiation into the lumped term of unknown uncertainty disturbance. The lumped term represents the unknown uncertainty of the system under the rotating coordinate system. Step 4: Further differentiate the other new power state selected in Step 3, select the duty cycle related terms in the polynomial obtained by differentiation as the control input, and aggregate the remaining terms obtained by differentiation into another unknown uncertainty disturbance aggregate term; Step 5: Combining the new energy state selected in Step 2, the new power state selected in Step 3, the lumped term of unknown uncertainty disturbance selected in Step 3, the control input selected in Step 4, and the lumped term of another unknown uncertainty disturbance selected in Step 4, construct a linearized standard state-space model. Step 6: Based on the standard state-space model constructed in Step 5, directly apply various disturbance observation and feedforward architecture disturbance rejection control methods to determine the control reference state; Step 7: Based on the mathematical model constructed in Steps 5-6, the applied disturbance rejection control method, and the determined reference state, design the corresponding control law, and then complete the state reconfiguration control of the AC / DC distribution network coupled nodes based on feedback linearization.

2. The AC / DC distribution network coupled node state linearization reconfiguration control method according to claim 1, characterized in that: The specific method for step 1 is as follows: Considering a typical medium-to-low voltage AC / DC coupling node, based on the moving average theory and Park coordinate transformation, the inductor current, capacitor voltage, control signal, and output current of phases a, b, and c of the three-phase AC coupling node are transformed into the dq rotating coordinate system to form a dynamic model, whose dynamic equations can be expressed as follows: Based on the moving average and coordinate transformation theory, the dynamic equation of the AC / DC coupling node can be written as: (1) in, , Let be the inductor currents along the d and q axes, respectively. , The capacitor voltages are on the d-axis and q-axis, respectively. , The output currents for the d and q axes are respectively. , These are the duty cycles for the d and q axes, respectively. , These are the inductance and capacitance values ​​on the AC side, respectively. , f It is the frequency, which is usually considered to be an approximately constant value in medium and low voltage distribution networks.

3. The AC / DC distribution network coupled node state linearization reconfiguration control method according to claim 1, characterized in that: The specific steps of step 2 include: (1) Considering the voltage-current nonlinear coupling in formula (1) of step 1, and the difficulty in directly obtaining the voltage-current in formula (1) of step 1 in actual operation. The new energy state is selected based on the port Hamiltonian theory, as shown in formula (2); (2) The derivative of the selected new energy state is calculated based on the relevant variables and their changing relationships in the dynamic model. The derivative expression of the new state is obtained, i.e., formula (3), which lays the foundation for subsequent processing and is more suitable for subsequent linearization and decoupling operations. (2) Differentiation yields: (3) in, , , Let be the new energy states along the d and q axes and their first derivatives with respect to time, respectively.

4. The AC / DC distribution network coupled node state linearization reconfiguration control method according to claim 1, characterized in that: The specific steps of step 3 include: To characterize the lumped term of unknown uncertainty disturbances in power dynamics in step 2, these uncertainty factors are lumped together so that they can be considered and addressed in a unified manner in subsequent steps, thereby reducing their impact on the system. Consider the known terms in formula (3) , Select a new state; make: (4) in, , It is the lumped sum of unknown and uncertain disturbances in power dynamics. , These represent another new power state for the d and q axes, respectively.

5. The AC / DC distribution network coupled node state linearization reconfiguration control method according to claim 1, characterized in that: The specific method for step 4 is as follows: Taking the derivatives of the new state selected in step 2 and the other new state introduced in step 3, we obtain the derivative expression of the new state (5): By combining existing dynamic models and related variable information, a detailed expression for the system change under the new state is derived, providing a key basis for the subsequent construction of the standard state-space form; (5) in, , Another new power state for the d and q axes, respectively. , The first derivative with respect to time.

6. The AC / DC distribution network coupled node state linearization reconfiguration control method according to claim 1, characterized in that: The specific steps of step 5 include: (1) The standard state-space form for constructing key AC / DC coupling nodes and converters is as follows: (6) in, , These are the control inputs for the d and q axes, respectively. , These are another unknown perturbation along the d and q axes, respectively; (2) Further organize and construct the standard state-space form of the key AC / DC coupling nodes and converters, as shown in formula (7), to transform the complex nonlinear AC / DC coupling node system into a relatively simple and easy-to-handle linearized standard state-space model: (7)。 7. The AC / DC distribution network coupled node state linearization reconfiguration control method according to claim 1, characterized in that: The specific steps of step 6 include: A nonlinear disturbance observer, expressed as in formula (8), is used to generate corresponding control signals based on the observed system state and disturbance conditions, thereby achieving effective control of the AC / DC coupling node and improving system performance. (8) in, , , , They are respectively , , , The estimation results, , , , , , , , Let be the intermediate variables of each observer along the d and q axes, and their first derivatives with respect to time. , , , These are the gain coefficients of the observers on the d and q axes, respectively; When the system is stable, the derivatives of each state are 0. Formula (9) is constructed as the control reference state to ensure that the system can operate and adjust according to the predetermined reference state. (9) in, , , , , , These are the reference values ​​for each state along the d and q axes, respectively.

8. The AC / DC distribution network coupled node state linearization reconfiguration control method according to claim 1, characterized in that: The control rate in step 7 can be written as: (10) in, , , These are the reference values ​​for each state along the d and q axes, respectively. This control law comprehensively considers information such as system state, reference state, and disturbance observations to generate specific control signals, which are used to drive equipment such as converters in AC-DC coupling nodes, thereby achieving effective regulation and control of the system state to reduce voltage distortion rate and shorten transient settling time.

9. A low-voltage AC / DC distribution network coupled node state reconfiguration control device based on feedback linearization, characterized in that: include: The sampling module, whose output is connected to the processor, is used to acquire the required current signal in real time. , , and voltage signal , , The actual analog quantity is converted into a digital signal that the processor can directly receive and execute; The processor is used to execute the steps of a low-voltage AC / DC distribution network coupled node state reconfiguration control method based on feedback linearization. The output of the drive module is connected to the AC / DC coupling node model and is used to receive control signals from phases a, b, and c. , , Modulate and generate a driving signal to directly drive steps S1 to S6; The storage module is used to store the state reconstruction control method program.

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