A power distribution method for a DC microgrid including an energy storage system

Abstract

The present invention relates to a power distribution control method for a DC microgrid including an energy storage system. The control process is as follows: by sampling each converter, the output voltage and output current of each converter are obtained, and the output power of each converter is obtained by calculation; the power output of each converter is exchanged with the adjacent converter through the network communication part to obtain the required power exchange amount; the power exchange amount δ pi With the local converter voltage output v dci After making the difference, compare the obtained value with the voltage given value V ref Connect to the secondary controller based on the active disturbance rejection control technology, and output the secondary control signal u through the controller i ; The generated secondary control signal u i To adjust the droop control, change the voltage set value to achieve accurate power distribution and voltage regulation through the voltage and current loop. The present invention eliminates the need to design voltage control and power control separately, simplifying the control structure.

Description

Technical field:

[0001] The present invention relates to the technical field of direct current microgrids, and in particular to a power distribution method for a direct current microgrid including an energy storage system. Background technology:

[0002] With the depletion of fossil energy and the growing severity of environmental pollution, distributed generation (DG) has gained widespread attention. Microgrids are an important means of utilizing distributed energy resources. Compared to AC microgrids, DC microgrids do not require frequency modulation or reactive power control, reducing system control complexity and improving conversion efficiency. Distributed generation units (DGs) are connected to the DC bus through corresponding converters. Different DGs have varying power ratings, so proper power distribution and stable DC bus voltage are key to ensuring stable microgrid operation.

[0003] In DC microgrid power distribution control, droop control is the most widely used, achieving power distribution by introducing virtual impedance. It has the advantages of a simple principle, no need for additional hardware, simple implementation, and no communication requirements. However, droop control has its own limitations, namely that its application can produce bus voltage deviations. To address the shortcomings of droop control, secondary control methods have been applied to DC microgrid power distribution control. Among existing secondary control methods, centralized secondary control methods require global information to achieve control objectives, are susceptible to single-point failures, and have poor reliability. Distributed secondary control methods achieve control objectives through limited communication, but suffer from complex controller design, a high communication burden, and are significantly affected by communication delays and interference. Summary of the invention:

[0004] This invention addresses the shortcomings of traditional distributed secondary control methods, such as complex control structures and high communication requirements. By introducing active disturbance rejection control technology into the secondary control part, a control structure using a voltage and power cascade is designed. This control method only requires exchanging power variables to achieve simultaneous voltage regulation and power distribution control, eliminating the need to design separate voltage and power controllers. This improves the complex structure and high communication requirements of traditional parallel control, simplifies the control structure, and reduces the communication burden. In addition, the introduction of active disturbance rejection control technology improves the system's ability to cope with uncertainty and resist interference. The specific technical solution is as follows:

[0005] A power distribution method for a DC microgrid including an energy storage system, wherein the control system includes: a network communication part, a secondary voltage control part, a secondary power control part, and a primary control part;

[0006] The primary control part includes a DC / DC converter, a voltage and current inner loop, and a droop control;

[0007] The secondary control part is designed by introducing the active disturbance rejection control technology, cascading the secondary voltage control part and the secondary power control part together, eliminating the need to design separate controllers;

[0008] The network communication part adopts a sparse communication network, and the control method only needs to exchange power variables with adjacent controllers;

[0009] The control process is as follows:

[0010] Step 1: By sampling each converter, the output voltage v of each converter is obtained. dci and the output current i dci ; The output power P of each converter is obtained by calculation dci =v dci ×i dci , where v dci is the output voltage of the converter corresponding to the i-th distributed unit, i dci is the output current of the converter corresponding to the i-th distributed unit;

[0011] Step 2: The power output of each converter is exchanged with the adjacent converter through the network communication part to obtain the required power exchange amount Among them, δ pi is the power exchange amount, a ij is the weight coefficient, x pi and x pj are the power vectors of the converters corresponding to the i-th and j-th distributed units respectively;

[0012] Step 3: Convert the power exchange amount δ pi With the local converter voltage output v dci After making the difference, compare the obtained value with the voltage given value V ref Connect to the secondary controller based on the active disturbance rejection control technology, and output the secondary control signal u through the controller i ;

[0013] Step 4: Generate the secondary control signal u i To adjust the droop control, change the voltage set value to achieve accurate power distribution and voltage regulation through the voltage and current loop.

[0014] After adopting the above control structure, the beneficial results of the present invention are:

[0015] As a control method for power distribution in a DC microgrid, the present invention introduces an active disturbance rejection control (ADRC) technology to change the secondary control structure, combines the voltage control and power control parts, simplifies the traditional parallel control structure into a cascade control structure, and realizes decoupling between voltage and power through the dynamic interference decoupling characteristics of the ADRC, eliminating the need to design voltage control and power control separately and simplifying the control structure. At the same time, the control method only needs to exchange power control variables with adjacent controllers, reducing the number of data exchanges required for control and eliminating the need to increase the frequency of communication, thereby alleviating the communication burden. At the same time, the ADRC technology is adopted to cope with the uncertainty during the actual operation of the system through the "total disturbance" concept of the ADRC, which can effectively improve the system's ability to cope with communication delays and anti-interference. Description of the drawings:

[0016] Figure 1 This is the block diagram of the secondary control structure of the present invention. The secondary controller exchanges data through a sparse communication network and only needs to exchange power variables with adjacent controllers. The power exchange amount is subtracted from the voltage output value of each converter and then the voltage set value is used to obtain the secondary control signal to adjust the droop control. In the figure, {1,2,3,…,n} represents each distributed generation unit in the microgrid system, δ pi is the power exchange amount, a ij is the weight coefficient, x pi and x pj are the power vectors of the converters corresponding to the i-th and j-th distributed units, respectively, v dci is the measured local converter voltage output, V ref Give the system a voltage value. u i The generated secondary control signal.

[0017] Figure 2 The control block diagram for each distributed generation unit is shown. By exchanging data with adjacent controllers, the required power control variables are obtained. The secondary control part generates secondary control signals to adjust the droop control. The power distribution and voltage regulation are achieved by adjusting the voltage set value. i ,L i and C i are the resistance, inductance and capacitance components corresponding to the i-th distributed unit respectively; V ref is the given voltage value of the system, v dci is the measured local converter voltage output value, is the voltage given value after adjustment by the proposed control; i dci is the measured local converter current output value, is the given value of the current loop, i L is the measured inductor current value; ri is the droop coefficient; {k p ,β1,β2,b0} are all ADRC parameters; δ pi is the power exchange amount, a ij is the weight coefficient, x pi and x pj are the power vectors of the converters corresponding to the i-th and j-th distributed units respectively; ∫ is the integration operator; ∑ is the summation operator. Specific implementation method:

[0018] Example:

[0019] Explanation of terms:

[0020] DC microgrid: A microgrid composed of direct current, which is an important component of the smart power distribution system.

[0021] Distributed power generation: also known as distributed power generation, distributed type power generation, and decentralized power generation, is a technology and system that uses a variety of small, grid-connected devices to generate electricity and store energy.

[0022] Energy storage systems include energy and material input and output, energy conversion, and storage equipment. They are used to store and release electrical energy generated by distributed generation units in microgrid systems.

[0023] Converter: A device that can convert one form of current into another, including DC-DC, DC-AC, AC-AC, and DC-AC. The form used in this invention is DC-DC conversion.

[0024] Direct current (DC): Also known as "constant current," it is a constant flow of electricity of constant magnitude and direction. It is the unidirectional flow or movement of electric charge, usually electrons. The current density varies over time, but the direction of movement generally remains the same at all times.

[0025] Droop control: A control method used for power distribution in DC microgrids that achieves power distribution by introducing virtual impedance. However, it has its own limitations: applying droop control can cause bus voltage deviations, which create an inherent conflict between bus voltage deviation and power distribution accuracy.

[0026] Power distribution: Performs the required control on the power output of each distributed generation unit in the DC microgrid.

[0027] Active disturbance rejection control (LADRC): An engineering control technology whose core idea is to call the internal and external disturbances of the system as total disturbances and estimate and compensate them.

[0028] Communication network: A data transmission method used to exchange information between distributed power sources in a DC microgrid system.

[0029] Communication delay: refers to the time delay that occurs during the communication process.

[0030] A control method for power distribution in a DC microgrid, the control system comprising: a network communication part, a secondary voltage control part, a secondary power control part, and a primary control part;

[0031] The primary control part includes a DC / DC converter, a voltage and current inner loop, and a droop control;

[0032] The design is carried out using the active disturbance rejection control technology, and the secondary voltage control part and the secondary power control part are cascaded together;

[0033] The network communication part adopts a sparse communication network and only needs to exchange power variables with adjacent controllers;

[0034] The control process is as follows:

[0035] Step 1: By sampling each converter, the output voltage v of each converter is obtained. dci and the output current i dci ; The output power P of each converter is obtained by calculation dci =v dci ×i dci , where v dci is the output voltage of the converter corresponding to the i-th distributed unit, i dci is the output current of the converter corresponding to the i-th distributed unit;

[0036] Step 2: The power output of each converter is exchanged with the adjacent converter through the network communication part to obtain the required power exchange amount Among them, δ pi is the power exchange amount, a ij is the weight coefficient, x pi and x pj are the power vectors of the converters corresponding to the i-th and j-th distributed units respectively;

[0037] Step 3: Convert the power exchange amount δ pi With the local converter voltage output v dci After making the difference, compare the obtained value with the voltage given value V ref Connect to the active disturbance rejection controller and output the secondary control signal u i ;

[0038] Step 4: Use the generated secondary control signal to adjust the droop control and change the voltage setpoint to achieve accurate power distribution and voltage regulation through the voltage and current loops.

[0039] This patent introduces active disturbance rejection control technology, realizing a cascade control structure of power and voltage. There is no need to design voltage and power controllers separately, which reduces the complexity of the control structure. The secondary controller only needs to exchange a power exchange quantity with the adjacent controller, without exchanging voltage variables, and does not require a high communication frequency, which reduces the communication burden. The total disturbance idea of active disturbance rejection control can effectively improve the control system's ability to cope with communication delays and anti-interference.

Claims

1. A power distribution control method for a DC microgrid including an energy storage system, characterized in that The control system includes: network communication part, secondary voltage control part, secondary power control part and primary control part; The primary control part includes a DC / DC converter, a voltage and current inner loop, and a droop control; Introducing the active disturbance rejection control technology into the secondary control part for design, cascading the secondary voltage control part and the secondary power control part together; The network communication part adopts a sparse communication network and only needs to exchange power variables with adjacent controllers; The control process is as follows: Step 1: By sampling each converter, the output voltage v of each converter is obtained. dci and the output current i dci ; The output power P of each converter is obtained by calculation dci =v dci ×i dci , where v dci is the output voltage of the converter corresponding to the i-th distributed unit, i dci is the output current of the converter corresponding to the i-th distributed unit; Step 2: The power output of each converter is exchanged with the adjacent converter through the network communication part to obtain the required power exchange amount Among them, δ pi is the power exchange amount, a ij is the weight coefficient, x pi and x pj are the power vectors of the converters corresponding to the i-th and j-th distributed units respectively; Step 3: Convert the power exchange amount δ pi With the local converter voltage output v dci After making the difference, compare the obtained value with the voltage given value V ref Connect to the active disturbance rejection controller and output the secondary control signal u i ; Step 4: Use the generated secondary control signal to adjust the droop control and change the voltage setpoint to achieve accurate power distribution and voltage regulation through the voltage and current loops.

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