CN108616141B - 微电网中lcl并网逆变器功率非线性的控制方法 - Google Patents

微电网中lcl并网逆变器功率非线性的控制方法 Download PDF

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CN108616141B
CN108616141B CN201810206558.3A CN201810206558A CN108616141B CN 108616141 B CN108616141 B CN 108616141B CN 201810206558 A CN201810206558 A CN 201810206558A CN 108616141 B CN108616141 B CN 108616141B
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inverter
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黄鑫
汪可友
李国杰
韩蓓
冯琳
江秀臣
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Shanghai Jiaotong University
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00Details of apparatus for conversion
    • H02M1/12Arrangements for reducing harmonics from ac input or output
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for ac mains or ac distribution networks
    • H02J3/01Arrangements for reducing harmonics or ripples
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24Arrangements for preventing or reducing oscillations of power in networks
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00Details of apparatus for conversion
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    • H02M1/126Arrangements for reducing harmonics from ac input or output using passive filters
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00Details of apparatus for conversion
    • H02M1/20Contact mechanisms of dynamic converters
    • H02M1/26Contact mechanisms of dynamic converters incorporating cam-operated contacts
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • H02M7/53871Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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    • H02M7/00Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • H02M7/53871Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
    • H02M7/53873Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current with digital control
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    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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    • H02M1/00Details of apparatus for conversion
    • H02M1/0003Details of control, feedback or regulation circuits
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00Details of apparatus for conversion
    • H02M1/0003Details of control, feedback or regulation circuits
    • H02M1/0012Control circuits using digital or numerical techniques
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Abstract

一种适用于微电网中LCL型并网逆变器与外接电网之间功率传输的非线性控制方法,本发明通过生成各种工况下满足特定有功、无功功率指令的参考电流,通过引入基于李雅普诺夫函数的非线性控制方法对逆变器控制,实现对所生成参考信号的快速、准确跟踪。该方法可有效实现有功功率、无功功率的解耦控制,系统动态响应迅速且鲁棒性较强,同时,该方法控制结构简单,易于实现,省去了同步控制环节和额外的电压、电流调节器,实现了各种工况下微电网中LCL型并网逆变器与电网之间快速、准确的功率交换和平稳的功率传输,为提高微电网内部的能量管理效率提供了保障。

Description

微电网中LCL并网逆变器功率非线性的控制方法
技术领域
本发明涉及电力电子变流器,更具体地,涉及一种微电网内LCL并网逆变器功率非线性的控制方法。
背景技术
微电网作为智能电网的关键技术之一,可有效解决分布式电源因位置分散、形式多样、特点各异而对主网和用户造成的冲击,实现对分布式电源的有效整合和高效利用,近年来受到了广泛关注。微电网的运行方式灵活,既能与大电网相连而并网运行,也可以脱离大电网独立运行。
由于微电网内含有大量可再生能源,多数可再生能源要通过逆变器并入微电网中,因此,采用先进的技术对逆变器进行控制尤为重要。当微电网处于并网运行状态下,每台逆变器需要根据微电网的中央控制器下发的功率指令准确地发出/吸收有功、无功功率,从而满足微电网与大电网之间特定的功率交换,同时提高微电网内部的能量管理效率。
然而,中、低压等级的微电网往往处于配电网末端,与配电网相连的公共连接处的电压质量并不理想,往往存在丰富的背景谐波,严重影响了并网逆变器传输功率的质量,同时,电网电压幅值骤升/骤降、频率的波动及线路阻抗的改变均会造成逆变器传输功率产生脉动,与预设功率指令产生偏差,造成能量的传输效率下降,严重时会影响系统的稳定性和逆变器并网。
目前对并网逆变器传输功率的控制主要是通过控制逆变器的输出电流实现的。传统的控制方法主要是双环控制,外环控制器产生参考信号,内环多为电流环,关系到逆变器的稳态精度、谐波含量、动态响应及抗干扰能力等。根据坐标系选取的不同对应不同的控制策略,如在同步旋转坐标系下需将交流量转换成直流量,通过采用比例积分控制器(PI)消除稳态误差,但是在电网电压非理想状态下,经同步旋转坐标系转换得到的将不再是直流量,传统的PI控制将无法满足零稳态误差跟踪。并且同步旋转坐标系下的控制需要用到锁相环节,锁相环性能的优劣将直接影响系统的动态响应速度和逆变器的控制效果。若在两相静止坐标系下进行控制,可省去变换所需的同步环节,减少了控制系统的复杂程度,比例积分调节器(PR)可在基波频率处呈现高增益特性,可对特定频率的正弦量近似实现误差跟踪。但是当正弦量中含有其他谐波分量时,需增加特定频率处的谐振控制器予以消除,增加了控制器的复杂性。而在三相自然坐标系下的控制中,三相系统被分为三个单相系统进行控制,因此对每一相的控制相对独立,虽可用于三相不平衡系统,但控制器的结构相对复杂。
与此同时,随着对非线性控制理论的深入研究,一些非线性控制表现的特性如:快速的动态响应、全局稳定性和较强的鲁棒性等,一定程度上弥补了线性控制的不足,近年来越来越受到学者们的关注,也在逆变器的控制中得到了一定应用,但仍有许多问题尚待解决。
发明内容
为应对上述传统方法的不足,提供一种LCL并网逆变器功率非线性的控制方法,以提升并网逆变器应对并网点处恶劣电能质量环境的能力,使每台逆变器在存在干扰条件下都能按照下达的功率指令平稳、准确地发出有功、无功功率,进而提高逆变器运行的可靠性和微电网运行效率。本发明提供一种设计合理并且具有良好动、稳态特性的LCL型并网逆变器功率非线性的控制方法。
为达到上述目的,本发明的技术解决方案如下:
一种微电网中LCL并网逆变器的控制方法,包括以下步骤:
步骤1、采集LCL型并网逆变器滤波电容电压vc和网侧电感电流io,经过坐标变换,建立其在两相静止坐标系下的数学模型;
步骤2、采集交流母线电压vg和本地负载电流iload,经过坐标变换,根据瞬时无功功率理论,生成两相静止坐标系下的网侧电感电流参考信号,并通过观测器对参考信号进行求导,得到参考信号的一阶导数和二阶导数值,作为非线性控制器的输入信号值;
步骤3、设定控制变量io的原始跟踪误差和滤波跟踪误差,建立并网逆变器的非线性控制模型;
步骤4、根据LCL型并网逆变器数学模型和并网逆变器非线性控制模型得到调制波信号,通过坐标变换,得到三相静止坐标系下的调制波信号,通过引入基于李雅普诺夫函数的非线性控制方法对并网逆变器进行控制。
所述并网逆变器在两相静止坐标系下的数学模型为:
所述基于瞬时无功功率理论生成两相静止坐标系下电流参考信号的方法如下
所述原始跟踪误差和滤波跟踪误差分别设定为
eαβ=ioαβ-ioαβ_ref
所述并网逆变器非线性控制模型为
其中,ioαβ表示两相静止坐标系下网侧电感电流分量;xαβ表示状态变量,d为干扰量,包括系统扰动和模型不确定性带来的误差;iloadαβ表示两相静止坐标系下的负载电流分量;vgαβ表示两相静止坐标系下电网电压分量;Pset、Qset分别为给定的有功功率、无功功率指令;ioαβ_ref表示参考电流信号分量;eαβ、Eαβ分别为设定的原始误差和滤波跟踪误差;uαβ表示两相静止坐标系下的非线性控制律,其中,k、λ、ks、ρ分别为自定义大于零常数。
所述状态变量xαβ可表示为
所述干扰量为:
其中,是对网侧滤波电感与线路电感之和Lo的估计值;Δvgαβ为电网电压引起的扰动;ΔRo、ΔLo为线路参数不确定带来的实际应用值和理论值之间的偏差;Δvcαβ为因电网电压扰动对电容电压造成的影响。
所述的生成的调制波信号为:
其中,vsαβ表示两相静止坐标系下的调制波信号分量;viαβ表示两相静止坐标系下的逆变器输入电压信号分量;Kd为比例系数且大于零;Li、C、Lo分别为逆变器侧滤波电感Li、滤波电容C以及网侧滤波电感加线路参数Lo的估计值;vcαβ表示两相静止坐标系下电容电压分量。
对所述非线性控制模型内自定义参数的合理取值,通过李雅普诺夫函数直接法证明系统的稳定性并实现跟踪误差趋向于0。
选择李雅普诺夫函数:V=1/2E2+1/2ρr2,其导数的取值与自定义参数k、λ、ks、ρ有关,通过设计自定义参数使V的导数由于V作为E、r的函数且有V>0,其导数确保V单调递减,直至E、r趋向于0,因此,证明了系统的全局稳定性,实现了跟踪误差趋向于0。
所述的干扰量d包含了对线路阻抗参数不确定性ΔRo、ΔLo的建模,保证了所设计控制器在系统参数不确定或线路阻抗发生变化时功率控制精度;包含了对电网扰动Δvg和电网扰动对电容电压影响Δvc的建模,保证了所设计控制器在非理想电网电压条件下的控制性能。
本发明的优点和积极效果在于:
1、本发明考虑了LCL并网逆变器在并网点电压质量不佳(存在较多谐波)、电压幅值波动、频率跳变等多种因素的干扰,利用李雅普诺夫函数的直接法证明了其稳定性,保证了逆变器发出/吸收有功、无功功率能够准确跟踪预设值,抑制由于电网电压不平衡带来的功率波动,提高了逆变器抗干扰的能力。
本发明在两相静止坐标系下实现,省去了锁相环节,使系统拥有更良好的动态性能。当有功、无功功率指令发生突变时,能够迅速响应,实现功率的快速跟踪,同时也保证了系统的暂态稳定性。
3、当负载为非线性负载时,能够保证入网电流的质量,实现有功、无功功率的准确传输。式(4)-(5)为参考电压计算公式,当负载为非线性负载时,负载电流波形非正弦,为保证入网电流为标准正弦波,得到的逆变器输出电流参考值一定为非正弦,即ioαβ_ref=iloadαβ-igαβ,所设计控制器能够对任意波形进行准确跟踪,因此能够保证入网电流的电流质量。
4、本发明考虑LCL并网逆变器系统参数不确定性,当线路阻抗发生改变时,系统具有较强的鲁棒性,不影响功率传输的精度。
附图说明
图1是本发明含LCL并网逆变器的微电网系统示意图。
图2是本发明控制方法的原理图。
图3是本发明并网点电压受到干扰下的电压波形和系统有功、无功功率波形。
图3(a)是并网点电压含谐波时的电压波形和系统有功、无功功率波形;
图3(b)是并网点电压幅值升/降时的电压波形和系统有功、无功功率波形;
图3(c)是并网点频率跳变时电压波形和系统有功、无功功率波形;
图4是功率指令发生突变时,系统的有功、无功功率波形。
图5是非线性负载下,系统的有功、无功功率及电流波形。
具体实施方式
以下结合附图对本发明实施例作进一步详细叙述。
一种微电网中LCL并网逆变器的非线性功率的控制方法,是在如图1所示的微电网系统中的LCL型并网逆变器上实现的。该系统主要包括外接电网1、并网点开关2、三相交流母线3、三相负载4、分布式发电单元5、其他分布式发电单元6这六个部分。
所述的分布式发电单元5包括直流电压源7、电压源三相全桥逆变器8、LCL型滤波电路9、线路阻抗10。所述直流电源7用理想直流电压源,电压表示为Vdc;所述电压源三相全桥逆变器8包括六个开关管S1~S6;所述LCL型滤波电路9包括逆变器侧滤波电感Li11、滤波电容C12、网侧滤波电感Lg 13;线路阻抗10包括线路电阻Ro 14和线路电感Ll 15,为方便建模,将网侧滤波电感Lg和线路等效电感Ll合并为Lo 16,电压源三相全桥逆变器8的空载电压为vi;滤波电容12上的电压为vc;并网点处电压为vg,逆变侧电感电流为ii;网侧电感电流为io;负载电流为iload;流入电网电流为ig
本发明的控制方法包括以下步骤:
步骤1、采集LCL并网逆变器滤波电容电压vc和网侧电感电流io,经过坐标变换,建立其在两相静止坐标系下的数学模型。
首先根据图1、图2所示,系统在两相静止坐标系下的数学模型可表示为:
考虑模型参数的不确定性和系统可能经受的扰动,式(17)可写成:
ΔLo、ΔRo表示系统参数估计的偏差;Δvgαβ表示电网电压扰动,Δvcαβ表示系统参数和电网电压带来的电容电压波动。
将扰动量表示为
定义状态变量:控制律表示为:其中分别为对Lo、C的估计值。因此,得到并网逆变器简化后的数学模型为
其中,d为干扰项,表示为可假设d未知但有界。
步骤2、采集交流母线电压vg和本地负载电流iload,经过坐标变换,根据瞬时无功功率理论,生成两相静止坐标系下的网侧电感电流参考信号,并通过观测器对参考信号进行求导,得到参考信号的一阶导数和二阶导数值,作为非线性控制器的输入信号值。
采集得到的vg、iload信号,经过坐标变换得到vgαβ、iloadαβ,通过基于瞬时无功功率的计算公式(21)得到网侧滤波电感的电流参考值ioαβ_ref
之后,通过观测器得到参考信号的一阶导数和二阶导数的精确估计值:
其中,分别为和ioαβ_ref的估计值,ko为观测器的增益,根据获得实时更新。
定义观测器的输出误差为:
通过设置足够大的观测器的增益ko,可使观测器输出误差调节到系统允许范围内。用同样的方法在一阶导数的基础上得到电流参考信号的二阶导数值。
步骤3、设定控制变量io的原始跟踪误差和滤波跟踪误差,建立并网逆变器的非线性控制模型;
定义原始误差信号和滤波跟踪误差信号分别为:
eαβ=ioαβ-ioαβ_ref
通过步骤2所述观测器,得到网侧滤波电感电流的一阶导数通过公式(24)得到滤波跟踪误差Eαβ作为非线性控制器的输入信号,非线性控制律为
其中,k、λ、ks、ρ分别为自定义大于零常数。
步骤4、根据LCL型并网逆变器数学模型和并网逆变器非线性控制模型得到调制波信号,通过坐标变换,得到三相静止坐标系下的调制波信号,通过引入基于李雅普诺夫函数的非线性控制方法对并网逆变器进行控制。
根据式(17)得到两相静止坐标系下的调制波信号为:
其中,为逆变器侧滤波电感的估计值;Kd为大于零的比例系数。
将所述的调制波信号输入正弦波矢量调制模块,得到S1~S6六路脉冲信号,输入并控制所述的电压源型三相全桥逆变电路。
综上所述,可以得到LCL型并网逆变器的功率非线性控制系,如图2所示。
现利用Matlab/Simulink搭建了1台LCL并网逆变器系统仿真模型,并模拟逆变器受并网点处扰动电压(含有谐波、幅值改变、频率跳变)影响、功率预设值发生改变以及非线性负载接入的3种实际工况,对所提控制算法进行检验。
工况一:并网点处电网电压受到扰动,主要存在三种情况:
1、含有背景谐波;
2、电压幅值发生改变;
3、频率产生波动。
设定功率值为向电网输入有功功率20kW,发出无功功率10kVar。分别验证以上三种网侧扰动对逆变器输入电网功率产生的影响。仿真结果如图3所示。vga、vgb、vgc分别代表并网点处abc三相电压,Pg、Qg分别代表逆变器与电网交换的有功功率和无功功率。系统仿真时长为0.2s,为方便对比,0~0.1s并网点电压为理想电压波形,0.1s~0.2s并网点电压受到干扰,为非理想电压波形。
首先将设定在0.1s后,并网点电压含有15V的三次谐波分量和15V的5次谐波分量,同时三次谐波分量相位滞后基波分量相位25度,五次谐波分量相位超前基波分量相位35度。从图3(a)中可以看出,0.1s后,逆变器输入电网的有功功率和无功功率能准确跟踪预设功率指令,并且当并网点电压存在畸变时仍保持功率传输的平稳,未产生二倍频脉动,电压情况恶化瞬间也未产生较大波动。
然后设定在0.1s后,并网点电压幅值产生波动,同样可以观测处,输入电网的有功、无功功率始终维持在预设值附近,并且时刻保持平稳。
最后,设定在0.1s后,并网点电压频率发生跳变,由50Hz下降至49.5Hz,可以看出传输功率未受频率变化的影响。
工况二:预设功率指令随时间变化,在0~0.1s中,设定系统输入电网的有功功率、无功功率均为零;0.1s~0.2s中,系统向电网输送有功功率10kW,从电网吸收无功功率20kVar;0.2s~0.3s,系统向电网输送有功功率20kW,从电网吸收无功功率10kVar;0.3s~0.4s,系统从电网吸收有功功率10kW,向电网发出无功功率10kVar。
从仿真结果可以看出,系统做到了对有功功率、无功功率的解耦控制,能够快速、准确地跟踪功率指令。
工况三:系统在0~0.1s向线性负载供电,0.1s~0.2s向非线性负载供电。且功率指令为向电网发出20kW的有功功率和10kVar的无功功率。
从仿真结果可以看出,在负载突变时刻,功率存在较小的冲击,并快速收敛至指令值,并在负载为非线性的情况下保证了向电网传输功率的平稳和准确。
由此可见,LCL型并网逆变器在并网点电压存在扰动、带非线性负载等情况下,采用所提控制方法可使其具有良好的功率传输能力,系统的动态响应迅速。

Claims (1)

1.一种微电网中LCL型并网逆变器的控制方法,其特征在于包括以下步骤:
1)采集LCL并网逆变器滤波电容电压vc和网侧电感电流io,经过坐标变换,建立所述的并网逆变器在两相静止坐标系下的数学模型为:
其中,ioαβ为两相静止坐标系下网侧电感电流分量;uαβ表示两相静止坐标系下的非线性控制律;
xαβ为状态变量:
d为干扰量,包括系统扰动和模型不确定性带来的误差;所述的干扰量为d:
式中,为对网侧滤波电感及线路电感之和Lo的估计值;Δvgαβ为电网电压引起的扰动;Ro为线路电阻值,ΔRo、ΔLo为线路参数不确定带来的实际应用值和理论值之间的偏差;Δvcαβ为因电网电压扰动对电容电压造成的影响,vgαβ表示两相静止坐标系下电网电压分量;
2)采集交流母线电压vg和本地负载电流iload,经过坐标变换,根据瞬时无功功率理论,生成两相静止坐标系下的网侧电感电流参考信号ioαβ_ref为:
式中,iloadαβ表示两相静止坐标系下的负载电流分量;入网电流igαβ可通过式(5)计算:
式中,Pset、Qset分别为给定的有功功率、无功功率指令;
3)设定网侧电感电流io的原始跟踪误差eαβ和滤波跟踪误差Eαβ分别为:
式中,ioαβ_ref表示参考电流信号分量,k为自定义大于零的常数,为原始跟踪误差eαβ的一阶导数;进一步定义跟踪误差为:
通过观测器对参考电流信号ioαβ_ref(t)进行求导,得到参考电流信号的一阶导数和二阶导数值作为非线性控制器的输入信号值,建立并网逆变器的非线性控制模型如下:
式中,k、λ、ks、ρ分别为自定义大于零的常数;
4)根据LCL并网逆变器数学模型和并网逆变器非线性控制模型得到调制波信号,通过坐标变换,生成三相静止坐标系下的调制波信号为:
其中,viαβ表示两相静止坐标系下的逆变器输入电压信号分量;Kd为比例系数且大于零;分别表示对逆变器侧滤波电感Li、滤波电容C和网侧滤波电感加线路电感Lo的估计值;vcαβ表示两相静止坐标系下电容电压分量;
5)利用所述的三相静止坐标系下的调制波信号通过引入基于李雅普诺夫函数的非线性控制方法对并网逆变器进行控制。
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