Article(id=1152342294650253567, tenantId=1146029695717560320, journalId=1146119893612605453, issueId=1152342291831681269, articleNumber=null, orderNo=null, doi=null, pmid=null, cstr=null, oa=null, hot=null, price=null, onlineType=0, articleFormat=0, articleType=null, articleTypeStr=null, receivedDate=1721318400000, receivedDateStr=2024-07-19, revisedDate=null, revisedDateStr=null, acceptedDate=null, acceptedDateStr=null, onlineDate=1752669412528, onlineDateStr=2025-07-16, pubDate=1747670400000, pubDateStr=2025-05-20, doiRegisterDate=null, doiRegisterDateStr=null, onlineIssueDate=1752669412528, onlineIssueDateStr=2025-07-16, onlineJustAcceptDate=null, onlineJustAcceptDateStr=null, onlineFirstDate=null, onlineFirstDateStr=null, sourceXml=null, magXml=null, createTime=1752669412528, creator=13701087609, updateTime=1752669412528, updator=13701087609, issue=Issue{id=1152342291831681269, tenantId=1146029695717560320, journalId=1146119893612605453, year='2025', volume='43', issue='5', pageStart='569', pageEnd='710', issueExtLink='null', onlineDate='null', pubDate='null', beforeIssueId=null, nextIssueId=null, price=null, status=1, issueComplete=1, articleOrder=1, issueType=1, specialIssue=null, createTime=1752669411857, creator=13701087609, updateTime=1753694458107, updator=13701087609, preIssue=null, nextIssue=null, ext={EN=IssueExt(id=1156641647501894486, tenantId=1146029695717560320, journalId=1146119893612605453, issueId=1152342291831681269, language=EN, specialIssueTitle=, coverIllustrator=, specialIssueEditor=, specialIssueAbout=), CN=IssueExt(id=1156641647501894487, tenantId=1146029695717560320, journalId=1146119893612605453, issueId=1152342291831681269, language=CN, specialIssueTitle=, coverIllustrator=, specialIssueEditor=, specialIssueAbout=)}, issueFiles=null}, startPage=681, endPage=686, ext={EN=ArticleExt(id=1152342294969020672, articleId=1152342294650253567, tenantId=1146029695717560320, journalId=1146119893612605453, language=EN, title=Research on parallel current sharing strategy based on AC signal injection, columnId=null, journalTitle=Renewable Energy Resources, columnName=null, runingTitle=null, highlight=null, articleAbstract=

Droop control is a common current sharing method for parallel converters in DC microgrid. However, due to the inconsistency of line parameters and the sampling error of sensors, the current distribution accuracy of traditional droop control is low. In order to solve this problem, this paper proposes a parallel current sharing strategy based on AC signal injection. Firstly, by superimposing an AC voltage small signal on the output voltage of the converter, the droop characteristic between the frequency of the AC voltage and the output current of the converter is constructed, and the reactive power generated by the signal and the feedback mechanism are used to realize the accurate current sharing of the converter. Secondly, the compensation virtual resistance is introduced to improve the stability of the system when the load changes greatly. Then, the design mode switching link stops the injection of AC signals in the steady state, so that the power quality can be improved. Finally, the effectiveness of the proposed control strategy is verified by simulation results.

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直流微电网中并联变换器常用下垂控制进行均流,但因线路参数不一致以及传感器采样误差,致使传统下垂控制电流分配精度较低。文章提出了一种基于交流信号注入的并联均流策略。首先,通过在变换器的输出电压上叠加一个交流电压小信号,构建交流电压的频率与变换器输出电流间的下垂特性,利用该信号产生的无功功率以及反馈机制实现变换器的精确均流;其次,引入补偿虚拟电阻,提高系统在负荷变化较大时的稳定性;然后,设计模式切换环节使得稳态时停止注入交流信号,让电能质量得以改善;最后,仿真结果表明该控制策略实现了大负载接入情况下的系统稳定,能够在无通信条件下自适应完成电流均分和改善电能质量的目标。

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薛阳(1976-),男,博士,副教授,研究方向为微电网协调控制、微网能量管理。E-mail:

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薛阳(1976-),男,博士,副教授,研究方向为微电网协调控制、微网能量管理。E-mail:

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薛阳(1976-),男,博士,副教授,研究方向为微电网协调控制、微网能量管理。E-mail:

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IEEE Journal of Emerging and Selected Topics in Power Electronics, 2021, 9(2): 1290-1301., articleTitle=Enhanced frequency droop method for decentralized power sharing control in DC microgrids, refAbstract=null), Reference(id=1159145983990149992, tenantId=1146029695717560320, journalId=1146119893612605453, articleId=1152342294650253567, doi=null, pmid=null, pmcid=null, year=2022, volume=52, issue=14, pageStart=15, pageEnd=19, url=null, language=null, rfNumber=[10], rfOrder=9, authorNames=段慧芹, 黄志勇, 杜书平, journalName=电气传动, refType=null, unstructuredReference=段慧芹, 黄志勇, 杜书平, 等. 基于交流小信号注入的双向 DC-DC 变换器均流控制[J]. 电气传动, 2022, 52(14): 15-19., articleTitle=基于交流小信号注入的双向 DC-DC 变换器均流控制, refAbstract=null)], funds=[Fund(id=1159145983130317641, tenantId=1146029695717560320, journalId=1146119893612605453, articleId=1152342294650253567, awardId=52075316, language=CN, fundingSource=国家自然科学基金(52075316), fundOrder=null, country=null), Fund(id=1159145983180649291, tenantId=1146029695717560320, 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figureFileSmall=Xql2Q6/kw6N37P+cJXkNcA==, figureFileBig=5UQdsFFzM8biY4kxmjy4Sg==, tableContent=null), ArticleFig(id=1159145982924796738, tenantId=1146029695717560320, journalId=1146119893612605453, articleId=1152342294650253567, language=EN, label=Table 1, caption=System simulation parameters, figureFileSmall=null, figureFileBig=null, tableContent=
参数 DG1 DG2 DG3
变换器电感 $L/\mathrm{{mH}}$ 1 1 1
变换器电容 $C/\mu \mathrm{F}$ 1000 1000 1000
输入电压/V 450 450 450
母线给定电压 ${U}^{ * }/\mathrm{V}$ 700 700 700
线路阻抗 ${R}_{\text{line }}/\Omega$ 1.2 1 0.8
频率下垂系数 ${d}_{\mathrm{{fk}}}$ 0.15 0.3 0.3
叠加交流电压 $A$ 3.5 3.5 3.5
注入频率 ${f}^{\prime }/\mathrm{{Hz}}$ 50 50 50
Q-V 耦合系数/V $\cdot {\mathrm{{var}}}^{-1}$ 8 8 8
电流调节器 1.2+20/s 1.2+20/s 1.2+20/s
电压调节器 $2 + 2/\mathrm{s}$ 2+2/s 2+2/s
), ArticleFig(id=1159145982991905605, tenantId=1146029695717560320, journalId=1146119893612605453, articleId=1152342294650253567, language=CN, label=表 1, caption=系统仿真参数, figureFileSmall=null, figureFileBig=null, tableContent=
参数 DG1 DG2 DG3
变换器电感 $L/\mathrm{{mH}}$ 1 1 1
变换器电容 $C/\mu \mathrm{F}$ 1000 1000 1000
输入电压/V 450 450 450
母线给定电压 ${U}^{ * }/\mathrm{V}$ 700 700 700
线路阻抗 ${R}_{\text{line }}/\Omega$ 1.2 1 0.8
频率下垂系数 ${d}_{\mathrm{{fk}}}$ 0.15 0.3 0.3
叠加交流电压 $A$ 3.5 3.5 3.5
注入频率 ${f}^{\prime }/\mathrm{{Hz}}$ 50 50 50
Q-V 耦合系数/V $\cdot {\mathrm{{var}}}^{-1}$ 8 8 8
电流调节器 1.2+20/s 1.2+20/s 1.2+20/s
电压调节器 $2 + 2/\mathrm{s}$ 2+2/s 2+2/s
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基于交流信号注入的并联均流策略研究
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薛阳 , 杨江天 , 李金星 , 李清 , 丁凯
可再生能源 | 2025,43(5): 681-686
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可再生能源 | 2025, 43(5): 681-686
基于交流信号注入的并联均流策略研究
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薛阳 , 杨江天, 李金星, 李清, 丁凯
作者信息
  • 1 上海电力大学 自动化工程学院 上海 200090
  • 薛阳(1976-),男,博士,副教授,研究方向为微电网协调控制、微网能量管理。E-mail:

Research on parallel current sharing strategy based on AC signal injection
Yang Xue , Jiangtian Yang, Jinxing Li, Qing Li, Kai Ding
Affiliations
  • 1 School of Automation Engineering Shanghai University of Electric Power Shanghai 200090 China
出版时间: 2025-05-20
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直流微电网中并联变换器常用下垂控制进行均流,但因线路参数不一致以及传感器采样误差,致使传统下垂控制电流分配精度较低。文章提出了一种基于交流信号注入的并联均流策略。首先,通过在变换器的输出电压上叠加一个交流电压小信号,构建交流电压的频率与变换器输出电流间的下垂特性,利用该信号产生的无功功率以及反馈机制实现变换器的精确均流;其次,引入补偿虚拟电阻,提高系统在负荷变化较大时的稳定性;然后,设计模式切换环节使得稳态时停止注入交流信号,让电能质量得以改善;最后,仿真结果表明该控制策略实现了大负载接入情况下的系统稳定,能够在无通信条件下自适应完成电流均分和改善电能质量的目标。

直流微电网  /  下垂控制  /  并联均流  /  交流信号注入  /  虚拟电阻

Droop control is a common current sharing method for parallel converters in DC microgrid. However, due to the inconsistency of line parameters and the sampling error of sensors, the current distribution accuracy of traditional droop control is low. In order to solve this problem, this paper proposes a parallel current sharing strategy based on AC signal injection. Firstly, by superimposing an AC voltage small signal on the output voltage of the converter, the droop characteristic between the frequency of the AC voltage and the output current of the converter is constructed, and the reactive power generated by the signal and the feedback mechanism are used to realize the accurate current sharing of the converter. Secondly, the compensation virtual resistance is introduced to improve the stability of the system when the load changes greatly. Then, the design mode switching link stops the injection of AC signals in the steady state, so that the power quality can be improved. Finally, the effectiveness of the proposed control strategy is verified by simulation results.

DC microgrids  /  droop control  /  current sharing  /  AC signal injection  /  virtual resistance
薛阳, 杨江天, 李金星, 李清, 丁凯. 基于交流信号注入的并联均流策略研究. 可再生能源, 2025 , 43 (5) : 681 -686 .
Yang Xue, Jiangtian Yang, Jinxing Li, Qing Li, Kai Ding. Research on parallel current sharing strategy based on AC signal injection[J]. Renewable Energy Resources, 2025 , 43 (5) : 681 -686 .
近年来, 为实现 “双碳” 目标, 太阳能、风能等可再生能源受到广泛关注[1]。同时,微电网技术也已成为发展可再生能源的重要研究方向[2]。微电网被分为直流微电网和交流微电网两类[3]。直流微电网在运行控制、资源利用以及投资建设方面有着诸多优势, 为保证直流微电网有效运行, 直流微电网中各变换器须实现协调控制及母线电压稳定[4,5]
由于并联变换器参数以及线路阻抗的不一致性, 变换器直接并联时难以实现负荷电流的均分, 从而降低系统的可靠性和稳定性。若系统处于大负荷工况, 部分输出电流大的变换器所承受的电流和电压应力也较大, 会率先到达其最大电流阈值, 造成模式切换混乱, 导致系统无法正常运行。 为了能在无通信条件下解决负荷电流分配和母线电压跌落问题,文献[6]提出了适用于直流微电网的叠加频率下垂法, 该方法在变换器的输出直流电压上叠加交流信号, 利用其频率协调控制各变换器,但在负载变化较大时, 系统存在稳定性不足的问题。为解决因注入信号频率低而造成系统动态性较差的问题,文献[7]提出了一种基于高频注入法的均流策略。文献[8]构建出频率-有功下垂关系,利用注入信号产生的有功功率调节下垂增益, 解决了系统由于线路阻抗差异而带来的功率无法合理分配的问题。文献[9,10]利用注入交流电压产生的无功功率来调节变换器输出电压, 实现了无通信条件下的负荷电流精确分配。但因注入了交流信号, 输出电压电流存在纹波, 给电能质量带来影响。
为解决交流信号注入法在负载变化较大时稳定性不足以及因输出电压带有交流纹波而影响电能质量的问题, 本文提出了一种改进的基于交流信号注入的并联均流策略。该策略分析了直流微电网系统典型结构与传统下垂控制的局限性, 进而提出基于交流信号注入的并联均流策略。在对信号注入法的并联均流过程进行理论分析基础之上, 设计补偿虚拟电阻和模式切换环节。在负载变化较大的情况下,改进后的控制策略实现对电流精确分配, 同时提高了电能质量。仿真结果验证了所提控制策略的有效性。
图 1 为直流微电网系统典型结构。该系统由分布式电源、储能系统和负载等组成。
分布式电源中的风电和光伏分别由$\mathrm{{AC}}/\mathrm{{DC}}$变换器和 DC/DC 变换器连接至直流母线,二者只能作为电源, 因此能量为单向流通。储能系统中的蓄电池以及超级电容模块经由双向 DC/DC 变换器连接至直流母线, 既可作为供能的电源又可作为储能的负载。交流负载和直流负载分别由$\mathrm{{AC}}/\mathrm{{DC}}$变换器和$\mathrm{{DC}}/\mathrm{{DC}}$变换器与直流母线相连。
电压-电流下垂控制是直流微电网中普遍应用的变换器均流策略,其表达式为
${U}_{\mathrm{{ok}}} = {U}^{ * } - {R}_{\mathrm{{dk}}}{I}_{\mathrm{{ok}}}$
式中:${U}_{\mathrm{{ok}}},{I}_{\mathrm{{ok}}}$分别为变换器输出电压、输出电流;${U}^{ * }$为直流母线给定电压;${R}_{\mathrm{{dk}}}$为变换器虚拟阻抗, 也称下垂系数。
图 2 为由两个变换器和一个负载并联在直流母线上所组成的微电网简化等效电路。
图 2 中:${U}_{\mathrm{o}1},{U}_{\mathrm{o}2}$为变换器的输出电压;${I}_{\mathrm{o}1},{I}_{\mathrm{o}2}$为变换器的输出电流;${U}_{\mathrm{{dc}}1},{U}_{\mathrm{{dc}}2}$为给定变换器电压;${R}_{\mathrm{d}1},{R}_{\mathrm{d}2}$为变换器虚拟阻抗;${R}_{\text{load }}$为微电网的等效负载;${R}_{\text{linel }},{R}_{\text{line2 }}$为线路阻抗;${U}_{\text{pcc }}$为直流母线电压。
根据基尔霍夫电压定律,变换器输出电流为
${I}_{\mathrm{{ok}}} = \frac{{U}_{\mathrm{{ok}}} - {U}_{\mathrm{{pcc}}}}{{R}_{\text{linek }}}, k = 1,2$
由式 (1), (2) 可得:
$\frac{{I}_{\mathrm{o}1}}{{I}_{\mathrm{o}2}} = \frac{{R}_{\mathrm{d}2} + {R}_{\text{line }2}}{{R}_{\mathrm{d}1} + {R}_{\text{line }1}}$
根据式 (3) 可知,当变换器虚拟阻抗远大于微电网等效负载时, 可实现各变换器输出电流按下垂系数成比例分配。如果选取的下垂系数数值较大,则可提高电流分配的精度,但造成的电压跌落也更大;如果选取的下垂系数数值较小,则电流分配的精度又不足。
在直流下垂控制系统中, 缺乏具有全局一致性的可控变量, 所以很难实现精准控制。对照交流电网系统中频率-有功的下垂控制思想, 将一个交流小信号叠加在变换器的输出电压上, 并将该信号的频率作为全局变量, 构建交流电压频率与变换器输出电流间的下垂特性, 以达到变换器均流的目的。基于此, 本文提出一种基于交流信号注入的并联均流控制策略, 其总体控制框图如图 3 所示。
图 3 中变换器的控制器由交流小信号注入、 下垂控制、模式切换和电压电流内环控制 4 个部分组成。其主要原理:叠加交流信号至变换器的输出电压上, 通过其产生的无功环流来调整各变换器的输出电压, 进而实现变换器电流均分。当达到稳态条件时,模式切换信号$\lambda$为 1,锁存器锁存该虚拟阻抗并停止信号注入, 变换器工作在下垂控制模式。当负载变化时, 信号重新注入并切换为频率控制模式。通过模式的自主切换, 实现分配精度的同时有效改善了交流纹波问题。在此基础上, 在下垂控制部分引入一定值补偿虚拟电阻, 通过增加等效下垂系数的方式提高了系统在接入大负载时的稳定性。
图 3 中每个变换器的输出电压均注入一个交流电压小信号,其表达式为
$ {\widetilde{U}}_{\mathrm{k}} = A\sin \left( {{2\pi }{f}_{\mathrm{k}}t}\right) $
式中:$A$为注入交流电压的幅值;${f}_{\mathrm{k}}$为注入交流电压的频率;$t$为时间。
幅值$A$过小则会难以检测,过大则会导致输出电压的纹波也较大。一般所允许的最大电压纹波为额定电压的$5\%$,对应幅值$A$应当小于额定电压的${2.5}\%$,本文取$A = {3.5}\mathrm{\;V}$。交流电压的频率和变换器输出电流应当满足下垂关系。
$ {f}_{\mathrm{k}} = {f}^{ * } - {d}_{\mathrm{{fk}}}{I}_{\mathrm{{ok}}} $
式中:${f}^{ * }$为交流电压的额定频率,取${50}\mathrm{\;{Hz}};{d}_{\mathrm{{fk}}}$为频率下垂系数。
由频率相角关系可得交流电压的相位角表达式为
$ {U}_{\mathrm{{ok}}} = {U}^{ * } - {R}_{\mathrm{{dk}}}{I}_{\mathrm{{ok}}} $
以 2 台变换器并联为例, 进行分析。系统稳态时,变换器的频率应相等,由式(5)可得,两变换器的输出电流值和对应的频率下垂系数值成反比, 即:
$ \frac{{I}_{\mathrm{o}1}}{{I}_{\mathrm{o}2}} = \frac{{I}_{\mathrm{n}1}}{{I}_{\mathrm{n}2}} = \frac{{d}_{\mathrm{f}2}}{{d}_{\mathrm{f}1}} = \alpha $
式中:${I}_{\mathrm{{nk}}}$为变换器$k$的额定电流;$\alpha$为变换器的额定容量比。
由式 (6)可得 2 台变换器的相位之差为
$ \varphi = {\varphi }_{1} - {\varphi }_{2} = {2\pi }\int \left( {{d}_{\mathrm{f}2}{I}_{\mathrm{o}2} - {d}_{\mathrm{f}1}{I}_{\mathrm{o}1}}\right) \mathrm{d}t $
由式 (8) 可知, 变换器输出电流与频率下垂系数成比例时, 相位之差为零。如果系统无法将变换器的输出电流根据比例进行分配, 那么相位差则会随着时间累计,此时将会形成无功功率环流。因线路阻抗相较于负载阻抗其数值很小, 该无功环流只存在于变换器间。
图 4 为低压直流微电网中 2 台变换器并联时的交流等效电路。
图 4 中:${R}_{\text{load }}$为负载;${R}_{\text{line }}$为线路电阻;${\widetilde{U}}_{\text{pcc }}$为母线电压交流分量。
变换器间的无功功率环流为
$ {Q}_{1} = - {Q}_{2} = - \frac{{A}^{2}}{2\left( {{R}_{\text{linel }} + {R}_{\text{line2 }}}\right) }\sin \varphi $
参照传统交流系统中的无功-电压下垂控制, 可通过无功功率补偿变换器输出的直流电压。 而变换器$k$的输出电压可由图 3 得到。
$ {U}_{\mathrm{{ok}}} = {U}^{ * } - {d}_{\mathrm{q}}G\left( s\right) {Q}_{k} $
式中:${U}^{ * }$为变换器给定直流电压;${d}_{\mathrm{q}}$为$Q - V$耦合系数;$G\left( s\right)$为一阶低通滤波器对应的滤波函数;${Q}_{k}$为变换器$k$的输出无功。
此时变换器$k$的等效下垂系数为
$ {R}^{\prime }{}_{\mathrm{d}k} = \frac{{d}_{\mathrm{q}}G\left( s\right) {Q}_{k}}{{I}_{\mathrm{o}k}} $
若线路阻抗${R}_{\text{linel }} > {R}_{\text{line }}$,则变换器初始电流${I}_{\mathrm{o}1} < {I}_{\mathrm{o}2}$,由式 (8),(9) 可知,两变换器输出的交流分量会存在相位差,进而产生无功功率环流。2 台等容量变换器并联均流过程如图 5 所示。
采用信号注入法的变换器在负载变化较大时, 存在系统稳定性低的问题, 因此需加以改进。 根据式(9)可知,信号注入法中的无功功率取值与交流电压幅值、线路电阻以及相位角的大小有关, 且存在上限。根据式(11),变换器的等效下垂系数也存在上限,故而信号注入法的均流能力受限。为此, 在原等效下垂系数基础上引入补偿虚拟电阻, 改进后的等效下垂系数为
$ {\widehat{R}}_{\mathrm{{dk}}} = {R}^{\prime }{}_{\mathrm{{dk}}} + {R}_{\mathrm{{dk}}} $
式中:${\widehat{R}}_{\mathrm{{dk}}}$为改进后的等效下垂系数;${R}^{\prime }{}_{\mathrm{{dk}}}$为原等效下垂系数,其大小可变;${R}_{\mathrm{{dk}}}$为补偿虚拟电阻,其大小固定。
${R}_{\mathrm{{dk}}}$的取值应当适宜,若与原下垂系数相比, 过小则难以达到提高系统稳定性的目的, 与传统下垂系数相比, 过大则会带来更多的母线电压跌落, 影响系统动态性能。而传统下垂系数虚拟电阻值为直流母线电压允许偏差最大值与变换器额定电流值之比。基于上述分析, 补偿虚拟电阻应满足:
$ {\widehat{R}}_{\mathrm{{dk}}} \leq {R}_{\mathrm{{dk}}} \leq \frac{\Delta U}{{I}_{\mathrm{{ok}}}} $
式中:${\Delta U}$为直流母线电压所允许的最大偏差。
信号注入法虽能实现较为精确的均流, 但由于交流信号的引入, 输出电压和电流会出现纹波, 影响电能质量。为解决这一问题,本文提出了一种切换控制策略,切换信号定义为
$ \lambda = \left\{ \begin{array}{l} 0,\left| \frac{{Q}_{k} - {Q}_{k}^{\text{ss }}}{{Q}_{k}^{\text{ss }}}\right| \geq {0.02} \\ 1,\text{ 其他 } \end{array}\right. $
式中:${Q}_{k}^{\mathrm{{ss}}}$为变换器$k$的无功功率最新稳态值。
图 3 可知,当负载发生变化时,稳态条件破坏,$\lambda = {SW} = 0$,此时变换器处于信号注入模式。系统经过均流反馈, 在一定时间内逐渐达到稳态,$\lambda = {SW} = 1$,此时停止信号注入,锁存器将锁存${R}^{\prime }{}_{\mathrm{{dk}}}$, 变换器切换至传统下垂控制模式, 下垂系数为锁存的${R}^{\prime }{}_{dk}$。改进后的控制策略无需通信,负载变化较大或较小时均能通过信号注入法快速完成均流, 而在检测到系统稳定后, 通过模式切换模块可停止信号的注入, 并迅速切换至传统下垂控制模式, 有效消除了输出电压、电流的交流纹波, 电能质量得到明显提升。
为了验证所提控制策略的均流性能以及对输出电压质量改善的能力, 利用 Matlab/Simulink 工具搭建了图 2 的简化直流微电网仿真模型, 并设计了两种案例进行对比分析。并联系统的电源为直流电源模型,负荷由${100\Omega }$阻性负荷和随时间变化的恒功率负荷(Constant Power Load, CPL)构成。系统初始负荷为${100\Omega }$阻性负荷;$t = 2\mathrm{\;s}$时,增加$2\mathrm{\;{kW}}$恒功率负荷;$t = 4\mathrm{\;s}$时,再增加$6\mathrm{\;{kW}}$恒功率负荷。系统中 3 台变换器的容量比为$2 : 1 : 1$,相应的系统参数如表 1 所示。
案例一中分别采用了传统下垂控制策略和本文所提信号注入法进行仿真, 通过对比分析验证了所提信号注入法对变换器输出电流的均分性能。传统下垂控制策略中变换器 DG1 和 DG2 的下垂系数分别为 1 和 2。仿真结果如图 6,7 所示。
图 6 给出了传统下垂控制下母线电压及两变换器输出电流的波形图, 可见, 系统起动后, 负荷每隔$2\mathrm{\;s}$发生一次变化。由图 6(a)可知,在系统开始运行及负荷变化后,当系统达到稳定时,由于线路阻抗的存在,母线电压存在较大的跌落,且随着负载电流增大而增大,最大为${16}\mathrm{\;V}$。由图 6(b)可知, 输出电流存在较大误差, 未能实现按比例分配。故须对传统下垂控制方法进行改进。
图 7(a) 可知,交流信号注入法下的母线电压基本能维持在给定值${700}\mathrm{\;V}$。但由于交流信号的注入,母线电压始终含有交流纹波,降低了电能质量。由图 7(b)可知,系统开始运行后,在 0~1.1$\mathrm{s}$变换器输出电流自适应调节,稳定时${I}_{\mathrm{o}1},{I}_{\mathrm{o}2}$分别为${4.6},{2.3}\mathrm{\;A}$;在$t = 2\mathrm{\;s}$,负荷增加$2\mathrm{\;{kW}}$,变换器输出电流在${0.9}\mathrm{\;s}$的时间内完成动态调节,${I}_{\mathrm{o}1},{I}_{\mathrm{o}2}$分别为${5.8},{2.9}\mathrm{\;A}$;在$t = 4\mathrm{\;s}$,负荷增加$6\mathrm{\;{kW}}$,由于负荷变化较大, 系统稳定性不足, 未能实现变换器的均流。
案例二分析了在所提改进控制策略下的 3 台变换器并联时的均流情况, 仿真结果如图 8 所示。
图 8(a)可知,母线电压由直流分量和叠加的交流分量组成, 负荷变化时, 母线电压的波动较小,始终处在稳定范围,动态调节时的电压纹波为${3.5}{\mathrm{\;V}}_{ \circ }$对比图7$\left( \mathrm{a}\right)$,采用切换控制后,电压纹波被消除并能保持稳定, 稳定时电压与直流母线额定电压偏差最大值为${10}\mathrm{\;V}$。由图 8(b)可知,$t = 2\mathrm{\;s}$负荷发生较小变化时,输出电流在${43}\mathrm{\;{ms}}$内完成自动调节并达到$2 : 1 : 1$的精确分配,相较于图 7(b) 可知, 所提控制策略具有更好的动态性。由于引入了补偿虚拟电阻,当$t = 4\mathrm{\;s}$时,虽然负荷变化较大, 但变换器输出电流仍能迅速根据容量之比进行准确分配,系统稳定性得到明显提高。
传统信号注入法的无功功率存在上限, 负载变化较大时稳定性不足,并且变换器输出的电压带有交流纹波, 影响电能质量。针对这一问题, 本文提出了一种改进的基于交流信号注入的变换器并联均流策略,对其仿真验证并得到以下结论。
①交流信号注入的反馈机制:通过构建交流电压的频率与变换器输出电流之间的下垂特性, 利用交流信号注入法的反馈机制实现变换器的均流,提高了系统的电流分配精度。
②补偿虚拟电阻:当负荷变化较大时,系统仅需较小的交流电压幅值以及无功功率便可保障其稳定性,增强了系统的动态响应能力。
③模式切换环节:在系统稳定后,通过停止信号注入来切换至传统下垂控制模式, 有效消除了输出电压和电流的交流纹波,提升了电能质量。
综上所述, 本文提出的策略不仅提高了变换器并联系统的均流精度和稳定性, 还通过引入虚拟电阻和模式切换机制, 有效解决了传统信号注入法的局限性,显著改善了电能质量。
  • 国家自然科学基金(52075316)
  • 上海市2021年度“科技创新行动计划”(21DZ1207502)
  • 国网浙江省电力有限公司科技项目(5211HZ17000F)
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2025年第43卷第5期
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  • 接收时间:2024-07-19
  • 首发时间:2025-07-16
  • 出版时间:2025-05-20
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  • 收稿日期:2024-07-19
基金
国家自然科学基金(52075316)
上海市2021年度“科技创新行动计划”(21DZ1207502)
国网浙江省电力有限公司科技项目(5211HZ17000F)
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    1 上海电力大学 自动化工程学院 上海 200090
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2种不同金属材料的力学参数

Family
属数
Number of
genus
种数
Number of
species
占总种数比例
Percentage of
total species (%)

Genus
种数
Number of
species
占总种数比例
Percentage of total
species (%)
鹅膏菌科Amanitaceae 2 11 5.26 鹅膏菌属 Amanita 10 4.78
小菇科 Mycenaceae 2 12 5.74 丝盖伞属 Inocybe 5 2.39
多孔菌科 Polyporaceae 8 14 6.70 蜡蘑属 Laccaria 5 2.39
红菇科 Russulaceae 3 23 11.00 小皮伞属 Marasmius 6 2.87
小菇属 Mycena 11 5.26
光柄菇属 Pluteus 5 2.39
红菇属 Russula 17 8.13
栓菌属 Trametes 5 2.39
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