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Proceedings ArticleDOI

Development of Dynamic Equivalents for MicroGrids using System Identification Theory

01 Jul 2007-pp 1033-1038

Abstract: Large deployment of microgrids will have a considerable impact on the future operation of the electrical networks and will greatly influence the power system dynamics mainly at the Medium Voltage (MV) level whenever the upstream system has been lost. In dynamic studies the whole power system cannot be represented in a detailed manner because the huge system dimension would require a very large computational effort. Therefore dynamic equivalents for microgrids need to be derived. The proposed approach is based on system identification theory for developing dynamic equivalents for microgrids, which are able to retain the relevant dynamics with respect to the existing MV network.
Topics: Electric power system (52%)

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      
        
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
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# #  # 

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+'    + *
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(+
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 , $,%   !# "-   
* '  (   +'+
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(  + ' "&
"' '+"+*$2#% 
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:"++2"(22
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@2=!"++2"(2"+
+':2;:'
+  * 2 2 2' $>4
/? '%
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+'+ '&  +   "+ + '>
,$,%"++&*"+
+ "- +  >, 2/ 
56789$8%'(+(&+*'
'+((''"+
B''+,
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0A C1+&'++D"* 
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("+' 
+&'('+,(&+*'
&   ' + & '
B' * + ' ( "+  
'&(B'
+' '+*(*
,"++#"-(
' ' '  + 
(B'*,B'
* ( B'* +B'  
+ "  0914 $% +( E $%
 + E $%  "-
'E $*%   * D"* 
 " ( +(   
(  (   ,   
+!#"-+'+*
+ (+*('
+&('(
"+*"('
**"+,
*( * "-  + '&
* , B'* * + & 
 '+ B'* *  *( ' +
*(B'*
,'(+(
:@2=! 

A
' ( +B'  (  +( +
&)&(B'*,
  "+ (  ( 
"++&&'+&
 &*   + ( &  
+'&'' +'
+++(
+ ' *  -"  +( +
&' + ( *( ' "+   
''" & -  4<- &)
( &)  0F1 + ) &- &)  
'"-"(''(
&' ( B'*  , 081   + "
(&'"+0F1
+++*&+(-"&'+
,()+''&''
-"+( ""+ +'-"
 +'&+(&)
+   ( -"  +(  
 +  ''   +(
0G1
+B'*+'&"'
,('"+*'&
+ # * '  - # "-   
"      " *'
+'+ ' +' +'(
++'+&,(B'*


,

D
,!#&'("++
'  (   + "+ !#
 :
:  , +'  '    
*
+ ,  (    &( 
,$,%+#H!#
'&  "++  * -( '  +
+++('B'+
  *
&+ '  $%  ! 
$!% +   ++  * 
&+  + ' $%   *4 
(+**"'*
&!+'++
'&(
 ,
2
!
!
>

,

: + ) + ,  )&( +
#*'&++'"+
,'&+(
   "( +  , +'  ,   -
 + &( ' * - '  + '
" (  &(   - 
B'
:",+'( 
,"&-"++#"-
"+ + (+' +  + #
**B'(
 ( B'*(   "+
* " (  ,   * 
  &+ +(   
+ - -'+"
( +'   &' ( B'*  ,
&  +(   +  (  
*  "  +    + ' 
'' ,       
&((+"
 
*    ' '   '& 
"   2# ( +* &  071
D"* +"-():'$:%
+++'&$%'"+
+"  $H*:
 HH *%*"
' " *'
"+ "   $HH * 
("+H*&%
 !"
*&"
4 2I *   # ' *
$#%  061 + 2I * /  +  +
" *&   ' + * " /
  > *' "++  & 
+('(+
,0A13 +(+(&+*'
 ,  *   ( &( + 
' +"+
+#'+&+*'(+'+
**B'(  + ,'
D"*&
 "++#"-+
' B'( 

+ # * " '' 
 &( + B'(  +   
:A

C
:A:B'(
 # '   * '
 ' ' *  * "
:B'(  '' * '  &+
+'+    + +  
"#('&$)
+%&(*&
051
# $#
3 +*+,"
(*+B'(
"&&*'+
 + #  +   ' " ' "
* &( / &&  ' *
"(+,B'(*
+'+    * '  * +*
 (   ( ' +( 
+ + ( B'( +' &  +
*'
%
+#*"'
:+'"(
&"4('2
 + &    ( 
&(+,&+ *'*
"''+(('+'&
&+B'(*01 :
CD"* ++(+(
("
:C!(B'(&
3 +  ,    + ' "
( +(+'++#*
" &&&  '( D"*
"'&+#*-" 
( B'( +  # * "
*++
( B'(  & 
+(B'(+*'+'++
  " * "    + (
(''+,"&'+"+
+ (+' + & * " 
'(
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::
!
J
J
  "+ (  ( 
"++&&'+&
 + &*   + ( <   '&
 '' +   '  + 
++(&0G1
+ '((
)   + & ( 
&(''&''
 /'      +
 ' ( B' &(  
<+("++' 
&'  +  ''  #&' 
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*(    () * + "+ +  +
'& (
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:9+&''+++
(''"&)'+'
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:9<'+'(+(

++&'"+'&
 + ' +" " +   + (
(&+*' "+ ++ "  +
   + + ' + 
&+*+&-
' ( + + +'+ 
+ ++''*
2''(&
  +  +  + &
 * , "++ *  +  
+(''+(
''''(-B''
+*&(B'$% 
( )
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 0F1 +   +B' 
'+ &"  & +B' +
   +B' * '
'+'+*++ "++
   +    +  
& &( +&'+  '+   
&(**+ 
'++*
'*&'

9
+&+
'  + +  &(  **
*'( + $% '  + 
&++B'0F1
2"$2%++&
'  (    "+ 
 2*+(
*&*0A1*'(2
"  $2% & + &  
2  +'+ + ' +  *
*(0C1'
&'
:(   *' "++ +  
'++';+*+
+-++*&'
''+(+*
(&-+'*
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+  +  , ( B'*
* ) (  +( ( 
+(  +  + '  (
&  + *& +( -"  (
*'(+,(B'*B'
&   ( '   
'+*(,"++#
"-" (,
"    + + -" &'
+ , ( " ' + "+ + 
' &+"
 
:('+"+,"-*
4 +"-"+ '&-
 "+ +  + ( B'*  &
&*  + ) ("+  
 + (    B'  +  
&  &( B'*+'
+)(+,
+"-+,"-
+ +( " + & + , ( "
'+ &" "  ( 
 + *   + ,4 % +  
* "+  #  * (  (
 "+ &% + &  "+  2I *
 ( " (    
+'++
!#  +'+ * "+ 2I   + 
&+'+&
+ '   '& ( B'*  ,
++*#
  
, (  ++  , " ( '
 :F

&



'
"


:F,(B'*
+ , ( B'* "  "+ + 
"- +'+ + (&'(4 + &'( &' 
+"&)&(&+&'(&'*
(B'(*&(*(+/
'+(:F

+ -( '   (  '  +
 ''   +  + +( "+
 ) + , " ( ' + '(
'+(++
* + * "     ' +' +
((&(''
   *  "++   '
.
/
0
/
* +'+ + &- 
:8
1
A
A
+
2
+
2
:8''+,(B'*
+ ''  "+ *' +* &
'+'+
+* 
[
]
221
AA
=
θ
$9%
+ *&
3

 : 8  + * " 
&(+,+#+
+ ' " +( 091 " '  
"+''
44!
+**&($9% 2
 ) + "+ + ' B'  
B'$A%+'+
*'   '& ( ' 
+   &" 2  + (
'   B' 2  + 
*+('+
 '  2 * +  
'*':G
-  ' + '  + + 
*    + *  "++  " &
'  *     &  +


F
Σ
:G2+
#
J
!
2
!:
 '  " * '
./
0/
*'>+(
*' +   '( + , (
B'* + '  " ' +
,    "   
  +  + , (
B'*+'+++:G
(  *   (  : 
,+!#"-+'+
+ *   "      
&     " +'
+#*'(+'+
8+  +"+'*'
$(%*>'&
5$
  0F1 "  ! 
      
B'*  *( +  "-
'&+#!# &(+
)&'
5$

#
!
!

+  +   &'  (
B'*+,+(
:7 "++,+,(
"'(+'$F55-#%
+#"-+"+#!#
 #H!# &'  ; +
, + , " C5-3   C5-3
:  +   * $("+% + '(
("+,'+:7
+    &  +  (
 :" + ,   +
'" (   " 
+ # "- "   ' 
B''&'7
$!%   +  + '   ' * 95
$+  '     LA 
LA5% "++'+(
   ' + *&   * F
"+*5
>8
+,
&&
'%
(
:7(>4$%(E$&%'
(
<!
,
2,

<
:
!,
!$M#% ,'$-3 E-#%
#"- F55N/55 4AF5EA4A55
, F5N/5 LALFN/A
:LFN/AE#L/F
  +    +
+( & &* +  + ,
(B'*&+,&+*'"
+,  '" "*'
: +''+*&'
+&'"++&"++
, + (+,
(B'**" 
&+*'''",
&&&A
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!$M#% ,'$-3 E-#%
#"- F55N/55 4A55EA4A55
, F5N/5 L5N/AE#L/F
AL:LFN/A
 + "   + "
B'*"'4%#"-
LFE A%   " '   LA5E C%
 + '*'(
L95    &" +  & 
'(:6>
:  +"   &" + * "
/&(+, "(B'*+
:"+,
   B'( *   & +"
: 5 +' + # / * "  
++,*''
 + +  "+ (  B'( 
 + "+ + (+' + 
B'('+
(&&*:6 *(

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Journal ArticleDOI
Anmar Arif1, Zhaoyu Wang1, Jianhui Wang2, Barry Mather3  +2 moreInstitutions (5)
TL;DR: A thorough survey on the academic research progress and industry practices is provided, and existing issues and new trends in load modeling are highlighted.
Abstract: Load modeling has significant impact on power system studies. This paper presents a review on load modeling and identification techniques. Load models can be classified into two broad categories: 1) static and 2) dynamic models, while there are two types of approaches to identify model parameters: 1) measurement-based and 2) component-based. Load modeling has received more attention in recent years because of the renewable integration, demand-side management, and smart metering devices. However, the commonly used load models are outdated, and cannot represent emerging loads. There is a need to systematically review existing load modeling techniques and suggest future research directions to meet the increasing interests from industry and academia. In this paper, we provide a thorough survey on the academic research progress and industry practices, and highlight existing issues and new trends in load modeling.

175 citations


Cites methods from "Development of Dynamic Equivalents ..."

  • ...The authors presented an alternative approach in [73] using a grey box modeling approach....

    [...]

  • ...gated models for the entire network using black-box [70]–[72] and grey-box [37], [38], [73] approaches....

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01 Feb 2014
TL;DR: This paper summarizes major results of the work of the CIGRE working group on load modeling of new types of load including renewables using measurement data and historical data after two years' activities.

123 citations


Proceedings ArticleDOI
01 Dec 2012
Abstract: The energy flow between source and the load of micro grid must be balanced to have a constant dc grid voltage. Due to intermittency in the natural sources and the variations in load, energy balance operation demands storage. The commonly preferred choice of energy storage in micro grid is valve regulated lead acid batteries. When batteries are used as energy storage, due to its low power density, the charge and discharge rate is low. It causes severe stress on the battery under quick load fluctuations and results in increase in the number of charge/discharge cycles. Hence, the lifetime of the battery reduces. The super capacitors have high power density and it can react speedily to quick load fluctuations. However, super capacitors alone cannot be used as energy storage as it cannot supply load for a longer time. Hence, this paper proposes a combined energy storage using batteries and super capacitors with high energy and power density. The photovoltaic (PV) based micro grid with combined energy storage is designed and the control strategy is validated for different atmospheric and load conditions.

85 citations


Cites background from "Development of Dynamic Equivalents ..."

  • ...It has numerous advantages which includes the utilization of natural sources, low carbon emission, decentralized power system network etc [1]....

    [...]


Journal ArticleDOI
Abstract: This paper presents the development of the dynamic equivalent model of an active distributed network (ADN) based on the grey-box approach. The equivalent model of an ADN comprises a converter-connected generator and a composite load model in parallel. The grey-box approach was chosen for model development as it incorporates prior knowledge about the ADN structure into the model, makes the model more physically relevant and intuitive than black-box or white-box models, and potentially improves the accuracy of the model. The dynamic equivalent model is presented in the seventh-order nonlinear state space format. It was initially loosely developed from the algebraic and differential equations describing assumed typical components of an ADN. Various static load models, dynamic load compositions, fault locations and a diverse range of distributed generation types and scenarios are considered in order to establish the generic range of model parameters for an ADN. The model is intended for the use in large power system stability studies.

75 citations


Cites methods from "Development of Dynamic Equivalents ..."

  • ...A dynamic equivalent of the MicroGrid (MG) was developed using the grey-box approach and evolutionary particle swarm optimization (EPSO) for parameter estimation purposes in [10]....

    [...]


Journal ArticleDOI
Jovica V. Milanovic1, Samila Mat Zali1Institutions (1)
TL;DR: The dynamic equivalent model of ADNC is presented in a seventh-order nonlinear quasi state space format, developed from the algebraic and differential equations describing assumed typical components of the ADNC.
Abstract: Paper presents an equivalent model of an active distribution network cell (ADNC) with distributed generation for transmission system stability studies. The equivalent model of ADNC comprises a converter-connected generator and a composite load model in parallel. The gray-box approach was chosen as it enables inclusion of prior knowledge about the ADNC structure into the model development, hence making the model more physically relevant and intuitive than a black-box or white-box model. The dynamic equivalent model is presented in a seventh-order nonlinear quasi state space format, developed from the algebraic and differential equations describing assumed typical components of the ADNC. The developed equivalent model of ADNC was validated through small and large disturbance studies using the modified IEEE nine-bus transmission system model.

71 citations


Cites methods from "Development of Dynamic Equivalents ..."

  • ...In [11], a gray-box approach was combined with an Evolutionary Particle Swarm Optimization (EPSO) algorithm for parameter estimation of a microgrid (MG)....

    [...]


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Abstract: The conventional reactive power in single-phase or three- phase circuits has been defined on the basis of the average value concept for sinusoidal voltage and current waveforms in steady states. The instantaneous reactive power in three-phase circuits is defined on the basis of the instantaneous value concept for arbitrary voltage and current waveforms, including transient states. A new instantaneous reactive power compensator comprising switching devices is proposed which requires practically no energy storage components.

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Jonas Sjöberg1, Qinghua Zhang2, Lennart Ljung1, Albert Benveniste2  +4 moreInstitutions (3)
TL;DR: What are the common features in the different approaches, the choices that have to be made and what considerations are relevant for a successful system-identification application of these techniques are described, from a user's perspective.
Abstract: A nonlinear black-box structure for a dynamical system is a model structure that is prepared to describe virtually any nonlinear dynamics. There has been considerable recent interest in this area, with structures based on neural networks, radial basis networks, wavelet networks and hinging hyperplanes, as well as wavelet-transform-based methods and models based on fuzzy sets and fuzzy rules. This paper describes all these approaches in a common framework, from a user's perspective. It focuses on what are the common features in the different approaches, the choices that have to be made and what considerations are relevant for a successful system-identification application of these techniques. It is pointed out that the nonlinear structures can be seen as a concatenation of a mapping form observed data to a regression vector and a nonlinear mapping from the regressor space to the output space. These mappings are discussed separately. The latter mapping is usually formed as a basis function expansion. The basis functions are typically formed from one simple scalar function, which is modified in terms of scale and location. The expansion from the scalar argument to the regressor space is achieved by a radial- or a ridge-type approach. Basic techniques for estimating the parameters in the structures are criterion minimization, as well as two-step procedures, where first the relevant basis functions are determined, using data, and then a linear least-squares step to determine the coordinates of the function approximation. A particular problem is to deal with the large number of potentially necessary parameters. This is handled by making the number of ‘used’ parameters considerably less than the number of ‘offered’ parameters, by regularization, shrinking, pruning or regressor selection.

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Proceedings ArticleDOI
07 Aug 2002
Abstract: It is expected that dispersed generation (DG) will play an increasing role in electric power systems in the near future. Among the benefits that DG can give to the power system operators and to the electricity customers, one of the most attractive is the possibility of improving the continuity of power supply. DG plants can be designed to supply portions of the distribution grid in the event of an upstream supply outage. Techniques for controlling DG plants that use feedback of only locally measurable variables are presented. This solution allows correct system operation and switching between parallel and isolated modes without needing online communication of control signals between the generators. The control technique is described with particular reference to inverter-interfaced systems (micro-turbines, fuel cells). Simulations of sample cases including different size and type of generators are presented.

303 citations


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Abstract: Under normal operating conditions, a MicroGrid is interconnected with the medium voltage network; however, in order to deal with black start and islanded operation following a general blackout, an emergency operation mode must be envisaged. A sequence of actions and conditions to be checked during the restoration stage are identified and tested through numerical simulation. Voltage and frequency control approaches, inverter control modes, and the need of storage devices are addressed in this paper in order to ensure system stability, achieve robustness of operation, and not jeopardize power quality during service restoration in the low voltage area

261 citations


Proceedings ArticleDOI
12 May 2002
TL;DR: A new meta-heuristic (EPSO) built putting together the best features of evolution strategies (ES) and particle swarm optimization (PSO), including an application in opto-electronics and another in power systems is presented.
Abstract: This paper presents a new meta-heuristic (EPSO) built putting together the best features of evolution strategies (ES) and particle swarm optimization (PSO). Examples of the superiority of EPSO over classical PSO are reported. The paper also describes the application of EPSO to real world problems, including an application in opto-electronics and another in power systems.

236 citations


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