CN111628491B - Direct current micro-grid improved droop control method based on line impedance detection - Google Patents

Direct current micro-grid improved droop control method based on line impedance detection Download PDF

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CN111628491B
CN111628491B CN202010510946.8A CN202010510946A CN111628491B CN 111628491 B CN111628491 B CN 111628491B CN 202010510946 A CN202010510946 A CN 202010510946A CN 111628491 B CN111628491 B CN 111628491B
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张小莲
汪麒
郝思鹏
刘海涛
陈凡
韦伟
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Nanjing Institute of Technology
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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Abstract

本发明公开了一种基于线路阻抗检测的直流微网改进下垂控制方法，该改进下垂控制方法在传统的下垂控制器中引入了下垂系数调节模块和电压调节模块，下垂系数调节模块利用线路阻抗检测模块获得的各线路阻抗的准确数值，比较各线路阻抗与设定的基准线路的线路阻抗的差异，进而对原各变换器下垂控制的下垂系数补偿，可克服线路阻抗的影响，实现各分布式电源均等出力；电压调节模块对输出电压做补偿，以抵消传统下垂控制带来的母线电压降落，从而维持系统电压稳定。本发明的改进下垂控制方法无需借助额外硬件设备，仅需检测系统已有的电气量，即可计算出线路阻抗的精确值，解决了传统下垂控制功率精准分配与母线电压维持额定难以协调这一固有矛盾。

Figure 202010510946

The invention discloses an improved droop control method for a DC microgrid based on line impedance detection. The improved droop control method introduces a droop coefficient adjustment module and a voltage adjustment module into a traditional droop controller. The droop coefficient adjustment module uses line impedance detection The accurate value of each line impedance obtained by the module compares the difference between each line impedance and the line impedance of the set reference line, and then compensates the droop coefficient of the droop control of each converter, which can overcome the influence of line impedance and realize each distributed The output of the power supply is equal; the voltage regulation module compensates the output voltage to offset the bus voltage drop caused by the traditional droop control, so as to maintain the stability of the system voltage. The improved droop control method of the present invention does not require additional hardware equipment, and only needs to detect the existing electrical quantity of the system to calculate the accurate value of the line impedance, which solves the difficulty of coordinating the precise distribution of traditional droop control power and maintaining the rated bus voltage inherent contradiction.

Figure 202010510946

Description

一种基于线路阻抗检测的直流微网改进下垂控制方法An improved droop control method for DC microgrid based on line impedance detection

技术领域Technical Field

本发明涉及直流微电网技术领域，具体地说是一种基于线路阻抗检测的直流微网改进下垂控制方法。The invention relates to the technical field of direct current microgrids, and in particular to an improved droop control method of a direct current microgrid based on line impedance detection.

背景技术Background Art

近年来以风力发电、光伏电池和微型燃气轮机等为代表的分布式发电(Distributed Generation，DG)技术的发展己成为人们关注的热点。在此基础上建立微电网能够充分发挥DG的作用，同时也是提高供电可靠性、改善电能质量，保证电网安全运行的一种十分有效的途径。与交流微网相比，直流微电网无需考虑母线电压相位、频率稳定问题，控制更简单，具有更高的可靠性；且目前越来越多的新能源发电方式、储能装置和负载等都使用直流电，减少了能量变换环节，同时提高系统效率。In recent years, the development of distributed generation (DG) technology represented by wind power generation, photovoltaic cells and micro gas turbines has become a hot topic of concern. Building a microgrid on this basis can give full play to the role of DG, and it is also a very effective way to improve power supply reliability, improve power quality, and ensure the safe operation of the power grid. Compared with AC microgrids, DC microgrids do not need to consider bus voltage phase and frequency stability issues, and are simpler to control and have higher reliability. At present, more and more new energy generation methods, energy storage devices and loads use DC power, which reduces the energy conversion link and improves system efficiency.

在直流微网中，直流电压源多用并联方式连接到公共直流母线上，为了实现各换器的均衡出力，现有的控制方法主要包括主从控制和下垂控制等。相较于主从控制依赖高速通信技术，下垂控制即使是在无通信的情况下也能达到各单元电流分配的目的，因此更适合于分布式的直流微电网系统。传统的下垂控制引入的下垂系数过大会造成母线电压降落过大，系数过小，又因系统线路本身存在线路阻抗而导致并联变换器之间产生较大电流差，形成环流。因此，功率精准分配与母线电压维持额定是传统下垂控制的固有矛盾。In a DC microgrid, the DC voltage source is mostly connected to the common DC bus in parallel. In order to achieve balanced output of each converter, the existing control methods mainly include master-slave control and droop control. Compared with the master-slave control that relies on high-speed communication technology, droop control can achieve the purpose of current distribution of each unit even without communication, so it is more suitable for distributed DC microgrid systems. If the droop coefficient introduced by traditional droop control is too large, the bus voltage will drop too much. If the coefficient is too small, the system line itself has line impedance, which causes a large current difference between parallel converters, forming a circulating current. Therefore, accurate power distribution and rated bus voltage maintenance are inherent contradictions in traditional droop control.

发明内容Summary of the invention

本发明的目的是针对传统下垂控制存在的功率精准分配与母线电压维持额定间的固有矛盾问题，提供一种基于线路阻抗检测的直流微网改进下垂控制方法；The purpose of the present invention is to provide an improved droop control method for a DC microgrid based on line impedance detection in order to solve the inherent contradiction between accurate power distribution and rated bus voltage maintenance in traditional droop control.

本发明的目的是通过以下技术方案解决的：The purpose of the present invention is to be solved by the following technical solutions:

一种基于线路阻抗检测的直流微网改进下垂控制方法，该改进下垂控制方法基于多源直流微电网系统，其特征在于：该多源直流微电网系统上设有线路阻抗检测模块、下垂系数调节模块和电压调节模块；其中线路阻抗检测模块用于获取多源直流微电网系统上任一条线路的线路阻抗值，通过将线路阻抗检测模块获得的全部阻抗值输送至下垂系数调节模块获得任一条线路的补偿下垂系数；将某条线路的补偿下垂系数和电压调节模块获得的对应的电压偏差值叠加到该条线路对应的多源直流微电网系统上的分布式电源的输出电压参考值上，获得该条线路对应的分布式电源的补偿电压参考值输出至电压电流控制模块以输出相应的控制指令至该分布式电源对应的DC-DC变换器上。An improved droop control method for a DC microgrid based on line impedance detection, the improved droop control method is based on a multi-source DC microgrid system, and is characterized in that: the multi-source DC microgrid system is provided with a line impedance detection module, a droop coefficient adjustment module and a voltage adjustment module; wherein the line impedance detection module is used to obtain the line impedance value of any line on the multi-source DC microgrid system, and the compensation droop coefficient of any line is obtained by transmitting all impedance values obtained by the line impedance detection module to the droop coefficient adjustment module; the compensation droop coefficient of a certain line and the corresponding voltage deviation value obtained by the voltage adjustment module are superimposed on the output voltage reference value of the distributed power supply on the multi-source DC microgrid system corresponding to the line, and the compensation voltage reference value of the distributed power supply corresponding to the line is obtained and output to the voltage and current control module to output the corresponding control instruction to the DC-DC converter corresponding to the distributed power supply.

所述的多源直流微电网系统包括n个分布式电源以及对应的滤波器、DC-DC变换器、线路阻抗、等效的公共负载，各分布式电源相互并联并经过对应的DC-DC变换器和滤波器连接到公共直流母线上。The multi-source DC microgrid system includes n distributed power sources and corresponding filters, DC-DC converters, line impedances, and equivalent common loads. The distributed power sources are connected in parallel to each other and are connected to a common DC bus through corresponding DC-DC converters and filters.

所述线路阻抗检测模块获得线路阻抗值的过程如下：The process of obtaining the line impedance value by the line impedance detection module is as follows:

A1、分别测量多源直流微电网系统上的第i个分布式电源对应的DC-DC变换器的输出电压Voi和输出电流Ioi；A1. Measure the output voltage V oi and output current I oi of the DC-DC converter corresponding to the i-th distributed power source in the multi-source DC microgrid system respectively;

A2、测量多源直流微电网系统上的公共负载RL两端的电压Vbus；A2. Measure the voltage V bus across the common load RL in the multi-source DC microgrid system;

A3、计算得到第i个分布式电源所对应线路的线路阻抗值Ri：A3. Calculate the line impedance value R i of the line corresponding to the i-th distributed power source:

Figure BDA0002528363610000021
Figure BDA0002528363610000021

式(1)中，Ri和Rlinei皆表示第i个分布式电源所对应线路的线路阻抗值。In formula (1), Ri and Rlinei both represent the line impedance value of the line corresponding to the i-th distributed generation.

所述下垂系数调节模块获得补偿下垂系数的过程如下：The process of obtaining the compensation droop coefficient by the droop coefficient adjustment module is as follows:

B1、以第j个分布式电源所对应线路的线路阻抗值Rj为参考阻抗值，计算得到第i个分布式电源所对应线路的线路阻抗值Ri和参考阻抗值Rj之间的阻抗误差dRi：dRi＝Ri-Rj；B1. Taking the line impedance value R j of the line corresponding to the j-th distributed power source as the reference impedance value, calculate the impedance error dR i between the line impedance value R i of the line corresponding to the ith distributed power source and the reference impedance value R j : dR i =R i -R j ;

B2、将阻抗误差dRi叠加到第i个分布式电源连接的DC-DC变换器对应的下垂控制器中的下垂系数Rdi上，得到第i个分布式电源连接的DC-DC变换器的补偿下垂系数R′di：R′di＝Rdi-dRi，式中的下垂系数Rdi为已知值。B2. Superimpose the impedance error dR i on the droop coefficient R di in the droop controller corresponding to the DC-DC converter connected to the i-th distributed power source to obtain the compensation droop coefficient R′ di of the DC-DC converter connected to the i-th distributed power source: R′ di =R di -dR i , where the droop coefficient R di is a known value.

所述步骤B2中的补偿下垂系数R′di根据阻抗误差dRi与0之间的关系包含以下三种情况：The compensation droop coefficient R′ di in step B2 includes the following three cases according to the relationship between the impedance error dR i and 0:

B21、当dRi＞0时，则第i个分布式电源连接的DC-DC变换器对应的补偿下垂系数R′di＝Rdi-|dRi|＝Rdi-(Ri-Rj)；B21. When dR i > 0, the compensation droop coefficient corresponding to the DC-DC converter connected to the i-th distributed power source is R′ di = R di - |dR i | = R di - (R i - R j );

B22、当dRi＜0时，则第i个分布式电源连接的DC-DC变换器对应的补偿下垂系数R′di＝Rdi+|dRi|＝Rdi-(Ri-Rj)；B23、当dRi＝0时，则第i个分布式电源连接的DC-DC变换器对应的补偿下垂系数R′di＝Rdi。B22. When dR i ＜0, the compensation droop coefficient corresponding to the DC-DC converter connected to the i-th distributed power source is R′ di ＝R di +|dR i |＝R di -(R i -R j ); B23. When dR i ＝0, the compensation droop coefficient corresponding to the DC-DC converter connected to the i-th distributed power source is R′ di ＝R di .

所述电压调节模块获得的对应的电压偏差值过程如下：The process of obtaining the corresponding voltage deviation value by the voltage regulation module is as follows:

C1、分别测量多源直流微电网系统上的第i个分布式电源对应的DC-DC变换器的输出电压Voi，并计算获得输出电压平均值

Figure BDA0002528363610000031
C1. Measure the output voltage V oi of the DC-DC converter corresponding to the i-th distributed power source on the multi-source DC microgrid system, and calculate the average output voltage
Figure BDA0002528363610000031

C2、根据输出电压平均值

Figure BDA0002528363610000032
和第i个分布式电源对应的DC-DC变换器的输出电压Voi，获得第i个分布式电源对应的DC-DC变换器的输出电压Voi的电压偏差值dVi：C2, according to the average output voltage
Figure BDA0002528363610000032
and the output voltage V oi of the DC-DC converter corresponding to the i-th distributed power source, and obtain the voltage deviation value dV i of the output voltage V oi of the DC-DC converter corresponding to the i-th distributed power source:

Figure BDA0002528363610000033
Figure BDA0002528363610000033

C3、利用电压电流控制模块将各电压偏差值dVi叠加到第i个分布式电源的输出电压参考值Vdci *上，获得第i个分布式电源的补偿电压参考值

Figure BDA0002528363610000034
C3. Use the voltage and current control module to superimpose each voltage deviation value dV i on the output voltage reference value V dci * of the i-th distributed power source to obtain the compensation voltage reference value of the i-th distributed power source
Figure BDA0002528363610000034

Figure BDA0002528363610000035
Figure BDA0002528363610000035

式(3)中的第i个分布式电源的输出电压参考值Vdci *为已知值。The output voltage reference value V dci * of the i-th distributed power source in formula (3) is a known value.

所述的电压电流控制模块为PI调节器。The voltage and current control module is a PI regulator.

本发明相比现有技术有如下优点：Compared with the prior art, the present invention has the following advantages:

本发明的改进下垂控制方法在传统的下垂控制器中引入了下垂系数调节模块和电压调节模块，下垂系数调节模块利用线路阻抗检测模块获得的各线路阻抗的准确数值，比较各线路阻抗与设定的基准线路的线路阻抗的差异，进而对原各变换器下垂控制的下垂系数补偿，可克服线路阻抗的影响，使各变换器的输出阻抗趋于一致，实现各分布式电源均等出力；电压调节模块将各变换器的输出电压与输出电压的平均值的差值作为调整量，对各变换器的输出电压进行调整，以抵消传统下垂控制带来的母线电压降落，整体抬高公共直流母线电压值，从而维持系统电压稳定；该改进下垂控制方法无需借助额外硬件设备，只需利用系统中已有的设备对系统的一些电气量进行检测，即可计算出线路阻抗的精确值，解决了传统下垂控制功率精准分配与母线电压维持额定难以协调这一固有矛盾，且具有良好的动态响应性能。The improved droop control method of the present invention introduces a droop coefficient adjustment module and a voltage adjustment module into the traditional droop controller. The droop coefficient adjustment module uses the accurate values of each line impedance obtained by the line impedance detection module to compare the difference between each line impedance and the line impedance of the set reference line, and then compensates the droop coefficient of the original droop control of each converter, which can overcome the influence of the line impedance, make the output impedance of each converter tend to be consistent, and achieve equal output of each distributed power source; the voltage adjustment module uses the difference between the output voltage of each converter and the average value of the output voltage as the adjustment amount, and adjusts the output voltage of each converter to offset the bus voltage drop caused by the traditional droop control, and overall raises the common DC bus voltage value, thereby maintaining system voltage stability; the improved droop control method does not require the use of additional hardware equipment, and only needs to use the existing equipment in the system to detect some electrical quantities of the system to calculate the accurate value of the line impedance, which solves the inherent contradiction that the traditional droop control power precise distribution and the bus voltage maintenance rating are difficult to coordinate, and has good dynamic response performance.

附图说明BRIEF DESCRIPTION OF THE DRAWINGS

附图1为本发明的基于线路阻抗检测的直流微网改进下垂控制方法的原理图；FIG1 is a schematic diagram of an improved droop control method for a DC microgrid based on line impedance detection according to the present invention;

附图2为本发明的多源直流微电网系统的结构图；FIG2 is a structural diagram of a multi-source DC microgrid system of the present invention;

附图3为本发明的多源直流微电网系统的等效电路图；FIG3 is an equivalent circuit diagram of a multi-source DC microgrid system of the present invention;

附图4为本发明的线路阻抗检测模块检测的分布式电源DG1的线路阻抗仿真图；FIG4 is a line impedance simulation diagram of the distributed power source DG1 detected by the line impedance detection module of the present invention;

附图5为本发明的线路阻抗检测模块检测的分布式电源DG2的线路阻抗仿真图；FIG5 is a line impedance simulation diagram of the distributed power source DG2 detected by the line impedance detection module of the present invention;

附图6为传统下垂控制与本发明的基于线路阻抗检测的直流微网改进下垂控制方法的DC-DC变换器的输出功率对比图；FIG6 is a comparison diagram of the output power of the DC-DC converter of the conventional droop control and the improved droop control method of the DC microgrid based on line impedance detection of the present invention;

附图7为传统下垂控制与本发明的基于线路阻抗检测的直流微网改进下垂控制方法的公共直流母线电压对比图；FIG7 is a comparison diagram of the common DC bus voltage between the conventional droop control and the improved droop control method of the DC microgrid based on line impedance detection of the present invention;

附图8为热插拔情况下的本发明的线路阻抗检测模块检测的分布式电源DG1的线路阻抗仿真图；FIG8 is a line impedance simulation diagram of the distributed power source DG1 detected by the line impedance detection module of the present invention in the case of hot plug;

附图9为热插拔情况下的本发明的线路阻抗检测模块检测的分布式电源DG2的线路阻抗仿真图；FIG9 is a line impedance simulation diagram of the distributed power source DG2 detected by the line impedance detection module of the present invention in the case of hot plug;

附图10为热插拔情况下的本发明的线路阻抗检测模块检测的分布式电源DG3的线路阻抗仿真图；FIG10 is a line impedance simulation diagram of a distributed power source DG3 detected by the line impedance detection module of the present invention in a hot-swap situation;

附图11为热插拔情况下的本发明的基于线路阻抗检测的直流微网改进下垂控制方法的输出功率仿真图。FIG11 is an output power simulation diagram of the improved droop control method of the DC microgrid based on line impedance detection of the present invention under hot plugging conditions.

具体实施方式DETAILED DESCRIPTION

下面结合附图与实施例对本发明作进一步的说明。The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

如图1、图2、图3所示，一种基于线路阻抗检测的直流微网改进下垂控制方法，该改进下垂控制方法基于多源直流微电网系统，多源直流微电网系统包括n个分布式电源以及对应的滤波器、DC-DC变换器、线路阻抗、等效的公共负载RL，各分布式电源相互并联并经过对应的DC-DC变换器和滤波器连接到公共直流母线上。该多源直流微电网系统上设有线路阻抗检测模块、下垂系数调节模块和电压调节模块；其中线路阻抗检测模块用于获取多源直流微电网系统上任一条线路的线路阻抗值，通过将线路阻抗检测模块获得的全部阻抗值输送至下垂系数调节模块获得任一条线路的补偿下垂系数；将某条线路的补偿下垂系数和电压调节模块获得的对应的电压偏差值叠加到该条线路对应的多源直流微电网系统上的分布式电源的输出电压参考值上，获得该条线路对应的分布式电源的补偿电压参考值输出至电压电流控制模块以输出相应的控制指令至该分布式电源对应的DC-DC变换器上。As shown in Figures 1, 2 and 3, an improved droop control method for a DC microgrid based on line impedance detection is provided. The improved droop control method is based on a multi-source DC microgrid system. The multi-source DC microgrid system includes n distributed power sources and corresponding filters, DC-DC converters, line impedances, and equivalent common loads RL . Each distributed power source is connected in parallel to a common DC bus through a corresponding DC-DC converter and filter. The multi-source DC microgrid system is provided with a line impedance detection module, a droop coefficient adjustment module and a voltage adjustment module; wherein the line impedance detection module is used to obtain the line impedance value of any line on the multi-source DC microgrid system, and the compensation droop coefficient of any line is obtained by transmitting all impedance values obtained by the line impedance detection module to the droop coefficient adjustment module; the compensation droop coefficient of a certain line and the corresponding voltage deviation value obtained by the voltage adjustment module are superimposed on the output voltage reference value of the distributed power source on the multi-source DC microgrid system corresponding to the line, and the compensation voltage reference value of the distributed power source corresponding to the line is obtained and output to the voltage and current control module to output the corresponding control instruction to the DC-DC converter corresponding to the distributed power source.

如图1所示，本发明的基于线路阻抗检测的直流微网改进下垂控制方法的基本工作原理如下：As shown in FIG1 , the basic working principle of the improved droop control method of a DC microgrid based on line impedance detection of the present invention is as follows:

采用了一个线路阻抗检测模块，分别测量多源直流微电网系统上的第i个分布式电源对应的DC-DC变换器的输出电压Voi和输出电流Ioi，以及测量多源直流微电网系统上的公共负载RL两端的电压Vbus，计算得到第i个分布式电源所对应线路的线路阻抗值

Figure BDA0002528363610000041
A line impedance detection module is used to measure the output voltage V oi and output current I oi of the DC-DC converter corresponding to the i-th distributed power source on the multi-source DC microgrid system, and the voltage V bus across the common load RL on the multi-source DC microgrid system, and calculate the line impedance value of the line corresponding to the i-th distributed power source.
Figure BDA0002528363610000041

采用了一个下垂系数调节模块，以第j个分布式电源所对应线路的线路阻抗值Rj为参考阻抗值，计算得到第i个分布式电源所对应线路的线路阻抗值Ri和参考阻抗值Rj之间的阻抗误差dRi＝Ri-Rj，将阻抗误差dRi叠加到第i个分布式电源连接的DC-DC变换器对应的下垂控制器中的下垂系数Rdi上，得到第i个分布式电源连接的DC-DC变换器的补偿下垂系数R′di＝Rdi-dRi，式中的下垂系数Rdi为已知值。A droop coefficient adjustment module is adopted. The line impedance value R j of the line corresponding to the j-th distributed power source is taken as the reference impedance value. The impedance error dR i =R i -R j between the line impedance value R i of the line corresponding to the ith distributed power source and the reference impedance value R j is calculated. The impedance error dR i is superimposed on the droop coefficient R di in the droop controller corresponding to the DC-DC converter connected to the ith distributed power source, and the compensation droop coefficient R′ di =R di -dR i of the DC-DC converter connected to the ith distributed power source is obtained, where the droop coefficient R di is a known value.

采用了一个电压调节模块，分别测量多源直流微电网系统上的第i个分布式电源对应的DC-DC变换器的输出电压Voi，并计算获得输出电压平均值

Figure BDA0002528363610000051
在计算获得第i个分布式电源对应的DC-DC变换器的输出电压Voi的电压偏差值
Figure BDA0002528363610000052
利用PI调节器将各电压偏差值dVi叠加到第i个分布式电源的输出电压参考值Vdci *上，获得第i个分布式电源的补偿电压参考值
Figure BDA0002528363610000056
A voltage regulation module is used to measure the output voltage V oi of the DC-DC converter corresponding to the i-th distributed power source on the multi-source DC microgrid system, and calculate the average output voltage
Figure BDA0002528363610000051
The voltage deviation value of the output voltage V oi of the DC-DC converter corresponding to the i-th distributed power source is calculated.
Figure BDA0002528363610000052
The PI regulator is used to superimpose each voltage deviation value dV i on the output voltage reference value V dci * of the i-th distributed power source to obtain the compensation voltage reference value of the i-th distributed power source.
Figure BDA0002528363610000056

下面结合具体实例，在MATLAB/Simulink下对本发明所提的改进下垂控制方法进行仿真验证。In combination with specific examples, the improved droop control method proposed in the present invention is simulated and verified under MATLAB/Simulink.

本发明以两台分布式电源(DG)并联直流系统对改进下垂控制方法的有效性进行验证。The present invention verifies the effectiveness of the improved droop control method by using a DC system with two distributed generation (DG) units connected in parallel.

根据以上分析，将下垂系数调节模块和电压调节模块引入各变换器传统下垂控制器中，改进后的下垂控制器的表达式如下：According to the above analysis, the droop coefficient adjustment module and the voltage adjustment module are introduced into the traditional droop controller of each converter. The expression of the improved droop controller is as follows:

第一号DC-DC变换器为：

Figure BDA0002528363610000057
其中R′d1＝Rd1-(R1-R2)，
Figure BDA0002528363610000053
The first DC-DC converter is:
Figure BDA0002528363610000057
Where R′ d1 =R d1 -(R 1 -R 2 ),
Figure BDA0002528363610000053

第二号DC-DC变换器为：

Figure BDA0002528363610000058
其中R′d2＝Rd2-(R2-R1)，
Figure BDA0002528363610000054
The second DC-DC converter is:
Figure BDA0002528363610000058
Where R'd2 = Rd2 - ( R2 - R1 ),
Figure BDA0002528363610000054

系统的仿真参数如下：The simulation parameters of the system are as follows:

表1系统仿真的参数Table 1 System simulation parameters

Figure BDA0002528363610000055
Figure BDA0002528363610000055

Figure BDA0002528363610000061
Figure BDA0002528363610000061

实施例一传统下垂控制方法与本发明的改进下垂控制方法的对比Example 1 Comparison between the conventional droop control method and the improved droop control method of the present invention

如图4、图5所示，采用本发明的基于线路阻抗检测的直流微网改进下垂控制方法，获得两分布式电源的线路阻抗检测值与设定值的误差在0.00000001，整体测量效果十分精确。可见本发明的改进下垂控制方法可精确的检测各分布式电源的线路阻抗。As shown in Figures 4 and 5, by using the improved droop control method of the DC microgrid based on line impedance detection of the present invention, the error between the line impedance detection value and the set value of the two distributed power sources is 0.00000001, and the overall measurement effect is very accurate. It can be seen that the improved droop control method of the present invention can accurately detect the line impedance of each distributed power source.

如图6、图7所示，在0s时，系统投入一号分布式电源DG1和二号分布式电源DG2，采用传统下垂控制方法，可见两分布式电源的输出功率不等，且偏差较大，公共直流母线电压降落较大。在2s时，引入基于线路阻抗检测的直流微网改进下垂控制方法，约经过0.3s后，可见两分布式电源的输出功率趋于一致，公共直流母线电压降落明显改善，且动态响应良好。可见本发明的改进下垂控制方法能够有效的缓解功率分配精度和电压降落间的矛盾。As shown in Figures 6 and 7, at 0s, the system puts distributed power source DG1 No. 1 and distributed power source DG2 No. 2 into use, and adopts the traditional droop control method. It can be seen that the output power of the two distributed power sources is not equal, and the deviation is large, and the voltage drop of the common DC bus is large. At 2s, the improved droop control method of the DC microgrid based on line impedance detection is introduced. After about 0.3s, it can be seen that the output power of the two distributed power sources tends to be consistent, the voltage drop of the common DC bus is significantly improved, and the dynamic response is good. It can be seen that the improved droop control method of the present invention can effectively alleviate the contradiction between power distribution accuracy and voltage drop.

实施例二热插拔情况下的本发明的改进下垂控制方法的适用效果Embodiment 2 Applicable effect of the improved droop control method of the present invention in the case of hot plugging

如图8、图9、图10所示，采用本发明的基于线路阻抗检测的直流微网改进下垂控制方法，在0s时，系统投入一号分布式电源DG1、二号分布式电源DG2和三号分布式电源DG3，计算得到的各线路阻抗值与设定值基本一致。在3s时，三号分布式电源DG3退出系统，一号分布式电源DG1、二号分布式电源DG2的线路阻抗实测值基本保持不变，三号分布式电源DG3的线路阻抗实测值突变为3*105Ω，线路阻抗可等效为无穷大。可见，本发明的基于线路阻抗检测的直流微网改进下垂控制方法能够有效适用于热插拔情况。As shown in Figures 8, 9 and 10, the improved droop control method of the DC microgrid based on line impedance detection of the present invention is adopted. At 0s, the system puts into use the No. 1 distributed power source DG1, No. 2 distributed power source DG2 and No. 3 distributed power source DG3, and the calculated impedance values of each line are basically consistent with the set value. At 3s, the No. 3 distributed power source DG3 exits the system, the measured line impedance values of the No. 1 distributed power source DG1 and No. 2 distributed power source DG2 remain basically unchanged, and the measured line impedance value of the No. 3 distributed power source DG3 suddenly changes to 3*10 5 Ω, and the line impedance can be equivalent to infinity. It can be seen that the improved droop control method of the DC microgrid based on line impedance detection of the present invention can be effectively applied to hot plug situations.

如图11所示，在0s时，系统投入一号分布式电源DG1、二号分布式电源DG2和三号分布式电源DG3，采用传统下垂控制，可见三台分布式电源输出功率不等，且偏差较大。在1s时，在系统中引入本发明所提供的基于线路阻抗检测的直流微网改进下垂控制方法，约经过0.3s后，可见三台分布式电源均匀出力，共同分担公共负载。在2s时，三号分布式电源DG3退出系统，可见三号分布式电源DG3的出力降为0，余下两分布式电源共同负担公共负载，且出力相同。即本发明的基于线路阻抗检测的直流微网改进下垂控制方法能良好的应用于热插拔情况。As shown in Figure 11, at 0s, the system puts distributed power source DG1 No. 1, distributed power source DG2 No. 2 and distributed power source DG3 No. 3 into use, and adopts traditional droop control. It can be seen that the output power of the three distributed power sources is not equal, and the deviation is large. At 1s, the improved droop control method of the DC microgrid based on line impedance detection provided by the present invention is introduced into the system. After about 0.3s, it can be seen that the three distributed power sources are evenly output and share the common load. At 2s, the distributed power source DG3 No. 3 exits the system. It can be seen that the output of the distributed power source DG3 No. 3 drops to 0, and the remaining two distributed power sources share the common load, and the output is the same. That is, the improved droop control method of the DC microgrid based on line impedance detection of the present invention can be well applied to hot plug situations.

以上实施例仅为说明本发明的技术思想，不能以此限定本发明的保护范围，凡是按照本发明提出的技术思想，在技术方案基础上所做的任何改动，均落入本发明保护范围之内；本发明未涉及的技术均可通过现有技术加以实现。The above embodiments are only for illustrating the technical idea of the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the present invention; any technology not involved in the present invention can be realized by existing technologies.

Claims (4)

1. A direct current micro-grid improved droop control method based on line impedance detection is based on a multi-source direct current micro-grid system and is characterized in that: the multi-source direct current micro-grid system is provided with a line impedance detection module, a droop coefficient adjustment module and a voltage adjustment module; the circuit impedance detection module is used for obtaining a circuit impedance value of any one circuit on the multi-source direct current micro-grid system, and all impedance values obtained by the circuit impedance detection module are transmitted to the droop coefficient adjustment module to obtain a compensation droop coefficient of any one circuit; superposing a compensation droop coefficient of a certain line and a corresponding voltage deviation value obtained by a voltage regulating module to an output voltage reference value of a distributed power supply on a multi-source direct current micro-grid system corresponding to the line, obtaining a compensation voltage reference value of the distributed power supply corresponding to the line, and outputting the compensation voltage reference value to a voltage and current control module so as to output a corresponding control instruction to a DC-DC converter corresponding to the distributed power supply;
the process of the droop coefficient adjusting module for obtaining the compensation droop coefficient is as follows:
b1, using the line impedance value R of the line corresponding to the jth distributed power supply j Calculating to obtain a line impedance value R of a line corresponding to the ith distributed power supply for the reference impedance value i And a reference resistance value R j Between the impedance error dR i ：dR i ＝R i -R j ；
B2, reducing the impedance error dR i Droop factor R superimposed into droop controller for the ith distributed power connection's DC-DC converter di Obtaining the compensation droop coefficient R of the ith distributed power supply connected DC-DC converter d ′ i ：R d ′ i ＝R di -dR i Sag factor R in the formula di Is a known value;
compensating for the droop coefficient R in step B2 d ′ i According to the impedance error dR i The relationship with 0 includes the following three cases:
b21, when dR i When the current value is more than 0, the compensation droop coefficient R corresponding to the DC-DC converter connected with the ith distributed power supply d ′ i ＝R di -|dR i |＝R di -(R i -R j )；
B22 when dR i If the current value is less than 0, the compensation droop coefficient R corresponding to the DC-DC converter connected with the ith distributed power supply d ′ i ＝R di +|dR i |＝R di -(R i -R j )；
B23, when dR i If =0, the compensation droop coefficient R corresponding to the DC-DC converter connected to the ith distributed power supply d ′ i ＝R di (ii) a The corresponding voltage deviation value process obtained by the voltage regulating module is as follows:
c1, respectively measuring output voltage V of DC-DC converter corresponding to ith distributed power supply on multi-source direct current micro-grid system oi And calculating to obtain the average value of the output voltage
Figure FDA0004077781480000011
C2, according to the average value of the output voltage
Figure FDA0004077781480000012
Output voltage V of DC-DC converter corresponding to ith distributed power supply oi Obtaining the output voltage V of the DC-DC converter corresponding to the ith distributed power supply oi Voltage deviation value dV of i ：
Figure FDA0004077781480000021
C3, utilizing the voltage current control module to control each voltage deviation value dV i Superimposed to the output voltage reference value V of the ith distributed power supply dci * Obtaining a compensation voltage reference value of the ith distributed power supply
Figure FDA0004077781480000022
Figure FDA0004077781480000023
Reference value V of output voltage of ith distributed power supply in expression (3) dci * Is a known value.
2. The line impedance detection-based direct current microgrid improved droop control method of claim 1, characterized in that: the multi-source direct-current micro-grid system comprises n distributed power supplies, corresponding filters, a DC-DC converter, line impedance and an equivalent common load, wherein the distributed power supplies are mutually connected in parallel and are connected to a common direct-current bus through the corresponding DC-DC converter and the corresponding filters.
3. The method for improving the droop control of the direct current microgrid based on the line impedance detection of claim 1 or 2, characterized in that: the process of the line impedance detection module for obtaining the line impedance value is as follows:
a1, respectively measuring output voltage V of DC-DC converter corresponding to ith distributed power supply on multi-source direct current micro-grid system oi And an output current I oi ；
A2, measuring common load R on the multi-source direct current micro-grid system L Voltage V across bus ；
A3, calculating to obtain a line impedance value R of a line corresponding to the ith distributed power supply i ：
Figure FDA0004077781480000024
In the formula (1), R i And R linei All represent the line impedance value of the line corresponding to the ith distributed power supply.
4. The line impedance detection-based direct current microgrid improved droop control method of claim 1, characterized in that: the voltage current control module is a PI regulator.
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