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Resonance damping of LCL filters via input admittance frequency shaping

Abstract

This paper presents a novel active damping technique of current-controlled grid-connected power converters through LCL filters. Based on H8 synthesis algorithms, a grid current controller is obtained so that the grid-connected power converted-based application admittance resembles a given frequency reference. By defining a low resistive admittance as the reference, considered application resonance is effectively damped, reducing grid current oscillations under grid voltage variations and avoiding their associated stability problems. Presented grid current controller senses only the PCC grid voltage and current, and is experimentally tested in both time and frequency domains. Additionally, the effectiveness of presented damping method is proved under different grid impedance scenarios.

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Resonance damping of LCL filters via input admittance frequency shaping

Author: Perez Morales, Jorge,Cóbreces Álvarez, Santiago,Pizarro, Daniel,Rodriguez Sanchez, Francisco Javier,Griñó Cubero, Robert
Publisher: IEEE Press
Year: 2016
DOI: 10.1109/ISIE.2016.7744943
Source: https://upcommons.upc.edu/bitstream/2117/99571/6/ISIE%202016_subm.pdf
© 2016 IEEE. Pe sonal use o his ma e ial is pe mi ed. Pe mission om
IEEE mus be ob ained o all o he uses, in any cu en o u u e media,
including ep in ing/ epublishing his ma e ial o ad e ising o
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edis ibu ion o se e s o lis s, o euse o any copy igh ed componen
o his wo k in o he wo ks
Resonance damping o LCL fil e s ia inpu
admi ance equency shaping
Jo ge Pé ez, San iago Cób eces,
Daniel Piza o, F ancisco Ja ie Rod íguez Sánchez
Depa amen o de Elec ónica
Uni e sidad de Alcalá
Email: jo [email p o ec ed]
Robe G iñó
Ins . o Indus ial and Con ol Enginee ing.(IOC)
Uni e si a Poli ècnica de Ca alunya (UPC)
Email: [email p o ec ed]
Abs ac —This pape p esen s a no el ac i e damping ech-
nique o cu en -con olled g id-connec ed powe con e e s
h ough LCL fil e s. Based on H∞syn hesis algo i hms, a
g id cu en con olle is ob ained so ha he g id-connec ed
powe con e ed-based applica ion admi ance esembles a gi en
equency e e ence. By defining a low esis i e admi ance as he
e e ence, conside ed applica ion esonance is e ec i ely damped,
educing g id cu en oscilla ions unde g id ol age a ia ions
and a oiding hei associa ed s abili y p oblems. P esen ed g id
cu en con olle senses only he PCC g id ol age and cu en ,
and is expe imen ally es ed in bo h ime and equency domains.
Addi ionally, he e ec i eness o p esen ed damping me hod is
p o ed unde di e en g id impedance scena ios.
I. INTRODUCTION
Pulsewid h modula ed (PWM) powe elec onic con e e s
a e usually connec ed o he g id h ough inpu fil e s in o de
o ensu e low THD sinusoidally shaped g id cu en s [1].
Rega ding g id cu en con ol applica ions, one o he mos
common opologies is he LCL fil e [2], which has be e
fil e ing capabili y han simple opologies as, o example,
he L fil e , bu also inc eases con ol complexi y [3]. Tha
is due o he p esence o wo complex conjuga e poles in he
con olled plan , which esonan ly inc eases i s open-loop gain
(i.e., i s admi ance alue).
This esonance will gene a e cu en oscilla ions (a he
esonan equency) unde changes in he sys em ope a ing
poin (e.g., PCC ol age pe u ba ions). These oscilla ions can
be mo e o less du able o e ime and high in magni ude
depending on how damped he esonance is. Mo eo e , hey
can become uns able in p esence o non-dissipa i e closed-
loop sys ems [4] and weak g ids [5].
Damping echniques o esonan sys ems ha e ecei ed
significan a en ion by he specialized li e a u e. They can be
so ed in wo big g oups; ac i e damping [2], [3], [5]–[10],
whe e he sys em con olle is modified o damp he esonance,
and passi e damping [1], [11]–[14], whe e passi e elemen s,
commonly esis ances, a e added o he fil e o displace he
esonan poles. Passi e damping is a simple solu ion bu
comes a he cos o ex a powe loss and educ ion o he
high- equency a enua ion capabili y [13]. Ac i e damping
echniques o e come passi e damping d awbacks, bu i s e -
ec i eness, howe e , is limi ed by he swi ching equency,
VSC
PCC
LCL il e
+
-
+
-
+
-
Powe
con olle
Cu en con olle
Fig. 1. One-line equi alen diag am o he conside ed sys em. In blue he
measu ed a iables, in g een he cu en con olle and in ed he inpu
admi ance o be shaped.
and addi ional passi e componen s may s ill be needed o
damp high- equency esonance [11].
This pape p oposes a new ac i e damping echnique o
g id-connec ed powe elec onic con e e s h ough LCL fil e s
by di ec ly shaping, in he equency domain, he closed-
loop inpu admi ance o he conside ed applica ion. A model-
e e ence app oach is adop ed, whe e designe defines he
desi ed admi ance a he esonan equency and an H∞syn-
hesis algo i hm ob ain he (sub)op imal con olle ha makes
he closed-loop inpu admi ance ma ch he gi en e e ence
[17]. The sys em esonance will be e ec i ely damped, hen,
by defining a pu ely esis i e admi ance as he e e ence.
The es o he pape is o ganized as ollows. Sec ion II
models he plan o he conside ed applica ion and in oduce
he esonan beha iou o he LCL fil e . Sec ion III de elop
he p oposed sys em con ol, s a ing wi h he con olle ob-
jec i es and ending up wi h i s design. Sec ion IV discuss
he esul s o he p oposed con olle , expe imen ally es ed in
bo h ime and equency domains. Addi ionally, i shows how
obus he con olle is, ega ding bo h s and-alone s abili y
and damping capabili y unde di e en g id condi ions. The
pape ends wi h a b ie discussion o i s conclusions.
II. DYNAMIC MODELLING
This pape conside s a g id cu en con ol o a shun
con e e connec ed o he g id h ough an LCL fil e (see
Fig. 1). The sys em is modelled in s a iona y (i.e., αβ)
e e ence ame, which allows e ec i e con olle ope a ion
e en unde unbalanced condi ions. Addi ionally, as αβ axes
a e uncoupled, he o iginal MIMO con ol p oblem is educed
o he con ol o wo iden ical SISO p oblems. Fo he sake
o no a ion simplici y, only one o he con olled channels is
conside ed in his pape o bo h plan modelling and con olle
design.
G id cu en idynamic o conside ed sys em is ep esen ed
in he Laplace domain as ollows:
I(s)=G(s)·U(s)+Gd(s)·Vs(s),(1)
whe e I(s),U(s)and Vs(s)a e he g id injec ed cu en ,
he VSC a e age ou pu ol age and PCC ol age, espec-
i ely. T ans e unc ions G(s)and Gd(s)a e he open-loop
command- o-ou pu and inpu open loop admi ance, espec-
i ely, which will ollow he nex dynamic exp essions i an
ideal PCC ol age (i.e., Lg=0) is conside ed:
G(s)=−Zc(s)
ZL1(s)·Zc(s)+ZL2(s)·(ZL1(s)+Zc(s)),(2)
Gd(s)= ZL1(s)+Zc(s)
ZL1(s)·Zc(s)+ZL2(s)·(ZL1(s)+Zc(s)),(3)
whe e Zc(s)=1/(sC),ZL1(s)=sL1+R1and ZL2(s)=
sL2+R2a e he capaci o , con e e -side coil and g id-side
coil impedances, espec i ely.
Bo h G(s)and Gd(s)ha e a pai o complex conjuga e
poles which will p oduce an inc ease o hei espec i e gains
a he esonance equency ω es =(L1+L2)/(L1·L2·C)
ad/s. O main impo ance in he s abili y o he conside ed
applica ion is he esonance in Gd(s)( e e o Fig. 7 o see
i s equency domain ep esen a ion), as i may cause high
cu en oscilla ions and e en sys em ins abili y unde PCC
ol age changes. Tha p oblem is inc eased i he sys em is
connec ed o a weak g id (i.e., wi h high g id impedance) [5].
The esonance mus be p ope ly damped in o de o assu e he
co ec and obus ope a ion o he sys em.
III. SYSTEM CONTROL
A. Con ol objec i es
The main objec i e o his pape is he design o a g id
cu en con olle ha , in addi ion o ack a gi en e e ence
i∗, can e ec i ely damp he sys em esonance. In o de o do
so, his pape p oposes he equency shaping o wo closed
loop ans e unc ion, acking ans e unc ion T(s)and
closed-loop admi ance Y(s), which ela e he g id cu en
e e ence i∗and he PCC ol age s o he ob ained g id
cu en , espec i ely.
Fig. 1 shows, in g een, he in eg a ion o he p oposed
con olle Kin he sys em. I has h ee inpu s: he measu ed
PCC ol age s, he sensed g id cu en iand i s co esponding
e e ence i∗. E en hough he con olle is ob ained as a
MIMO sys em in he syn hesis p ocess, is in e es ing o di ide
i s ans e ma ix in ows: K(s)=[KsK e Ki]T. Con-
olle ac ua ion udynamic can be exp essed in he Laplace
domain as ollows:
U(s)=Ks(s)·Vs(s)+K e (s)·I∗(s)+Ki(s)·I(s).(4)
Subs i u ing exp essions (4), (2) and (3) in (1) gi es he closed
loop g id cu en dynamic in he Laplace domain:
I=(1−GKi)−1GK e
  
T(s)
I∗+(1−GKi)−1(Gd+GKs)
 
Y(s)
Vs,
(5)
whe e (s and-alone) sys em s abili y depends only on he
sys em open-loop ans e unc ion L=−GKi.
The con olle design ollows a model- e e ence app oach;
ha is, a con olle K(s)is ob ained in o de o make he
closed-loop ans e unc ions Y(s)and T(s) esemble wo
gi en model e e ences, Y e (s)and T e (s). By defining
a plain low admi ance e e ence a he sys em esonance
equency, oscilla ions can be e ec i ely damped and, as a
esul , de i ed s abili y p oblems a e a oided.
As i is shown in Fig. 1, g id cu en e e ence i∗is
gene a ed by an ou e loop powe con olle , whose objec i e
may be, o example, main ain he DC-bus ol age DC equal
o a gi en e e ence ∗
DC e en unde changes o he load RL
(i.e., he sys em ac s as an ac i e ec ifie ) [15]. I s design is
ou o he scope o his wo k, which is cen ed in he inne
cu en con olle design.
B. Con olle design
Con olle K(s)is ob ained h ough an H∞syn hesis
algo i hm, whose inpu is he gene alized plan P[16]. I is
jus a i ual MIMO plan wi h he s uc u e showed below:
z
z
z
=Pw
w
w
u
u
u,(6)
whe e w
w
wis called he exogenous inpu s ec o o he sys em,
z
z
zis he so-called ou pu e o signals, u
u
uis he ac ua ion
ec o ha will be compu ed o he con olle and
is he
measu emen s ou pu ec o .
H∞syn hesis p ocess will compu e a (sub)op imal con-
olle K, which minimizes he infini y no m1o he closed-
loop sys em N ha esul s om he eedback in e connec ion
o Pand K, and ela es exogenous inpu ec o w
w
wand e o
ec o z
z
z=Nw
w
w:
min
KN(K)∞=min
K
z
z
z2
w
w
w2
≤γ(7)
Fig. 2 shows he conside ed i ual plan P(in ed) used o
ob aining he con olle K(in blue) and he esul ing closed-
loop sys em N.Pis o med by he open-loop plan s Gand
Gd(in o ange) and a se o added elemen s only necessa y o
he syn hesis p ocess (in pu ple) which a e explained below.
T e (s)and Y e (s)a e he desi ed ( e e ence model) ack-
ing and admi ance ans e unc ions. Thei ou pu s, i and iy,
1The infini y no m o a MIMO sys em H(s)in he equency domain is
defined as H(s)∞
supω¯σ(H(jω)), whe e ¯σ(H(jω)) is he maximum
singula alue o H(jω). Fo SISO sys ems ha is simplified o H(s)∞

supω|H(jω)|
s
*
i
i
i
y
e
y
i
e
w
u
z
N
*
i
s
i
u
d
G
G
e
T
e
Y
u
W
W
y
W
P
K
i
s
*
i
u
s
Fig. 2. S uc u e used o he H∞syn hesis. In ed he gene alized plan
P(s). W apped inside o i , in o ange he open loop plan G(s)and open
loop admi ance Gd(s), and in pu ple he e e ences and weigh s added o
he syn hesis. Finally, he ob ained con olle is ep esen ed in g een.
ma k he e e ence cu en s due o acking and admi ance
con ol e ec s, espec i ely. G id cu en iis sub ac ed om
bo h e e ence cu en s, gi ing wo di e en e o s: e o
acking and ey o admi ance con ol. Bo h con olle objec-
i es (i.e., admi ance and acking shaping) can be achie ed
by means o minimizing hese wo e o s. Bu , as bo h e o s
depend on he g id cu en , hey can no minimized a he
same equencies (i.e., ican no be equal o bo h i and iy
a he same equency). Addi ionally, con ol bandwid h mus
be limi ed by means o con ol e o uminimiza ion. To
handle his ade-o , h ee equency-weigh s (W (s),Wy(s)
and Wu(s) espec i ely) mul iplies each signals. Ou pu and
inpu signal ec o s o gene alized plan Pdefined in Fig. 2
a e hen:
z
z
z=⎡
⎣
W ·e
Wy·ey
Wu·u
⎤
⎦
=⎡
⎣
s
i∗
i
⎤
⎦w
w
w= s
i∗u
u
u=u(8)
As syn hesized con olle Kshould minimize z
z
z, inc easing
one weigh a a gi en equency (while se ing he o he wo
ela i ely low) should esul in he minimiza ion o i s inpu a
ha equency. Following his design c i e ion, and gi en he
con olle objec i es s a ed in he p e ious subsec ion, sui able
equency-weigh s a e ep esen ed in Fig. 3. As i is shown,
acking o cu en e e ence i∗is only desi ed a he g id
undamen al equency, 60 Hz in his applica ion, meanwhile
admi ance shaping is desi ed, mainly, a supe -synch onous
equencies, which is he loca ion o he LCL-fil e esonance
(a sub-synch onous admi ance shaping is also conside ed o
damp possible low equency g id oscilla ion). Finally, con ol
bandwid h is limi ed a high equencies. Laplace exp essions
o he selec ed weigh s a e showed below:
W (s)=K
s2+2ζnω1s+ω2
1
s2+2ζdω1s+ω2
1
,(9)
whe e K is he ini ial acking gain, ω1is he undamen al
equency in ad/s and ζdand ζnwill define bo h maximum
102101100101102103104
100
50
0
50
100
Magni ude (dB)
Admi ance
shaping a ea Admi ance
shaping a ea
Re e ence
acking a ea
Con ol
s opband
F equency (Hz)
Fig. 3. Magni ude o he selec ed weigh s in he equency domain. The
equency spec um is di ided in a eas acco ding o he con olle objec i e
in ha ange.
)(
sW
)(
y
sW
)(
usW
)(
e
sT
)(
e
sY
)('sG
)(
dsG
)(zG
)(sG
()sK
()zK
syn hesis
()sP
1
)(()zz'
GzG
Disc e ize h ough
ZOH me hod
Add compu a ional
delay
Make con inuous
h ough Tus in
app oxima ion
Con inuous plan
wi h delay and
ZOH dynamics
sis
Disc e ize h ough
Tus in me hod
Con inuous open
loop model
C
o
n
i
n
u
o
u
s
o
p
e
n
l
o
o
p
m
o
d
e
l
Design
speci ica ions
Fig. 4. Flux diag am o he inne con olle Ksyn hesis and disc e iza ion
p ocess
gain peak and wid h o he weigh esonance;
Wy(s)=Ky
s2+2ζdω1s+ω2
1
s2+2ζnω1s+ω2
1
·1
(1/ωy)s+1 (10)
whe e an ini ial weigh Ky>K
is defined, ζdand ζnchange
posi ions o define a complemen a y no ch o he acking
weigh esonance and an addi ional pole is defined a high
equency ωy o delimi he admi ance shaping egion;
Wu(s)=Ku
(1/ωu1)s+1
(1/ωu2)s+1,(11)
whe e a ze o in he equency ωu1will inc ease he ini ial low
ac ua ion weigh Ku, and a pole a e y high equency ωu2
is added jus o ulfil H∞syn hesizing me hod equi emen s.
As o he e e ence model, a acking e e ence T e =1is
se , which will esul in pe ec cu en acking a undamen al
equency (i.e., I(jω1)≈I∗(jω1)), meanwhile a low esis i e
admi ance o Y e =0.1Ω
−1is conside ed, which will esul
in a p ope ly damped LCL esonance.
Syn hesized con olle K(s)is ob ained in Laplace con inu-
ous domain. In o de o be implemen ed in a digi al pla o m,
AC p og ammable
Powe supply
DSP-FPGA
Con ol pla o m
VSC
LCL l e
Fig. 5. Pic u e o expe imen al se -up.
TABLE I. EXPERIMENTAL SETUP PARAMETERS
Sn17.5kVA L13.4mH
Vg120 VR128.8mΩ
ω12π60 ads−1L21.7mH
V∗
DC 700 VR218.6mΩ
Tsw 400 μsC18 μF
Ts200 μsCDC 4.7mF
i mus be p e iously disc e ized. The disc e iza ion p ocess
is summed up in Fig. 4. I is impo an o poin ou ha
he ob ained con olle , and hen he close-loop admi ance,
akes in o accoun he phase lag in oduced by bo h PWM
modula ion and compu a ional delay. Fo mo e in o ma ion
abou he disc e iza ion p ocess o he admi ance and acking
shaping o powe con e e s e e o [17].
IV. RESULTS
P oposed algo i hm has been es ed in bo h simula ions
and an expe imen al se -up. The la e consis o an AC
p og ammable powe supply Pacific Sma Sou ce 345-AMX,
emula ing he g id, and a 17.5kVA wo-le el VSC connec ed
o i h ough an LCL fil e . Passi e loads RLa e connec ed
o he DC-side o es he pla o m unde di e en ope -
a ing poin s. Con ol algo i hm is implemen ed on a Texas
Ins umen s DSP TMS320DSK6713. Table I sums up se -up
pa ame e s, whe e Tsis he sampling pe iod o he con ol
algo i hm and Tsw is he con e e ’s IGBTs swi ching pe iod.
A pic u e o he expe imen al se -up is shown in Fig. 5.
A. F equency domain esul s
Fig. 6 shows heo e ical acking ans e unc ion T(ob-
ained ollowing (5)), which is equal o i s e e ence T e a
he undamen al equency, as was specified in he design p o-
cess. Fig. 7 shows he admi ance shaping esul s. Theo e ical
admi ance Yis equal o he gi en e e ence Y e a bo h
sub and supe -synch onous equencies as i was specified.
F equency (Hz)
M
agn
i
u
d
e
(dB)
100101102103
−10
−5
0
5
T e T
Fig. 6. Ob ained acking ans e unc ion Tand i s e e ence T e .
F equency (Hz)
−200
−150
−100
−50
0
Magni ude (dB)
Y e GdYYiden
Phase (deg)
100101102103
−180
−90
0
90
180
Fig. 7. Admi ance equency esul s. Open-loop admi ance Gdis shown in
black. Admi ance e e ence model Y e is shown on blue colo . The closed
loop syn hesised admi ance ( heo e ical) Yis shown on pu ple. Red c osses
show he expe imen ally measu ed admi ance Yiden .
Yiden is an expe imen al admi ance measu emen ob ained by
adding a h ee phase con olled sinusoidal signal o he ol age
gene a ed by he AC powe supply and analysing, in s eady-
s a e, he cu en esponse o he con e e a ha equency.
O main impo ance is he esonance equency o Gd, whe e
mo e poin s o Yiden a e aken, which p o es he good ac i e
damping capabili ies o he p oposed me hod.
B. Sys em obus ness
Fig. 8 shows he ob ained sys em sensi i i y unc ion S=
(1 −GKi)−1. I s infini y no m S∞is a good in e se
indica o o he design s and-alone obus ness [16], ha is,
how much plan pa ame e s may change un il he designed
sys em becomes uns able. A commonly design c i e ion o
obus con olle is o syn hesize loops wi h S∞<6dB,
which will assu e a gain ma gin bigge han 6dB and a phase
ma gin bigge han 30o. This c i e ion is ulfilled, as i can be
seen in Fig. 8, which p o es he design obus ness.
The e ec s o g id impedance on he p esen ed ac i e
damping echnique a e es ed below. Conside ing a non-ideal
induc ance Lga he PCC, he g id cu en is modified as
ollows:
I(s)=G(s)·U(s)+G
d(s)·Vg(s),(12)

F equency (Hz)
M
agn
i
u
d
e
(dB)
100101102103
−80
−60
−40
−20
0
20
S
Fig. 8. Ob ained sensi i i y unc ion S. Blue dash-do ed line ma ks he
accep ed 6dB sensi i i y gain limi o obus sys ems.
Lg(p.u)
F equency(Hz)
|Y|(-1)
Lg(p.u)
F equenc
y
(Hz)
Fig. 9. E ec o modi ying he g id induc ance Lgon he ob ained close
loop admi ance modulus |Y(s)|.
whe e Vg(s)=Vs(s)+(s·Lg)·I(s)and
G(s)=−Zc(s)
ZL1(s)·Zc(s)+Zg(s)·(ZL1(s)+Zc(s)),(13)
G
d(s)= ZL1(s)+Zc(s)
ZL1(s)·Zc(s)+Zg(s)·(ZL1(s)+Zc(s)) (14)
He e Zg(s)=s(Lg+L2)+R2is he new g id-side impedance.
Subs i u ing exp essions (4), (13) and (14) in (12) gi es he
new closed loop inpu admi ance Y(s)seen om he PCC:
Y(s)= I(s)
Vs(s)=G(s)·Ks(s)+G
d(s)
1−(G(s)·Ki(s)+s·Lg·Gd(s))
(15)
Fig. 9 shows closed loop inpu admi ance modulus |Y(s)|in
he equency domain unde changes o he g id induc ance
Lg∈[0.05,1] p.u 2. P esen ed damping echnique is e ec i e
e en unde high g id induc ances (i.e., weak g ids), as i
is shown in he minimum modulus inc ease o e he gi en
admi ance e e ence o 0.1Ω
−1.
C. Time domain esul s
Fig. 10 shows expe imen al ime domain e olu ion o he
sys em a e he in oduc ion o a DC-load o 4.2 kW. Fig.
2Lgis exp essed in pe uni alues o he con e e nominal impedance
Zn=(
√3Vg)2/Sn.
G id ol age
G id cu en
DC-bus ol .
Zoom 1
Zoom 1 Zoom 2
G id ol age G id ol age
G id cu en G id cu en
DC-bus ol . DC-bus ol .
+250V
-250V
+30A
-30A
+780V
+580V
+250V
-250V
+30A
-30A
+780V
+580V
+250V
-250V
+30A
-30A
+780V
+580V
5ms/di 50ms/di
0ms
-5000ms
-3165ms-3215ms-3390ms-3890ms
Zoom 2
Fig. 10. Connec ion o a 4.2kW DC-load wi h a null eac i e e e ence. Top
shows he comple e ansien . Zoom 1 ocuses on he cu en s and DC- ol age
e olu ion a e he connec ion. Zoom 2 shows g id cu en s and ol ages in
s eady-s a e.
G id ol age
G id cu en
DC-bus ol .
Zoom 1
Zoom 1
+250V
-250V
+60A
-60A
+720V
+680V
+250V
-250V
+60A
-60A
+720V
+680V
20ms/di
-790000us
-1290000us
-1084000ms
G id ol age
G id cu en
DC-bus ol .
50ms/di
-1284000us
Fig. 11. Response unde g id balanced ol age dip when DC-bus is loaded
wi h 4.2kW. All phases all o 60% o i s alue keeping hei phase un ouched.
Top iew shows he comple e ansien in g id ol ages, cu en s and DC-bus
ol age. Lowe iew ocuses on he dip ini ial edge.
11 shows he esponse o he sys em unde a balanced dip
o 60% o he nominal g id ol age alue. Bo h expe imen s
show good cu en acking pe o mance. O main impo ance
is he cu en esponse unde he g id dip: as can be seen, no
oscilla ion a equency ω es can be app ecia ed on i , which
p o es again he good ob ained esonance damping.
V. CONCLUSION
This wo k p esen s a no el ac i e damping echnique o
cu en -con olled g id-connec ed powe con e e s h ough
esonance fil e s like he LCL. Resonance damping will esul
in smalle cu en oscilla ions unde PCC ol age a ia ions
and, as a consequence, will imp o e sys em s abili y in con-
nec ion o weak g ids.
P esen ed ac i e damping echnique is based on equency
shaping o he closed-loop inpu admi ance o he conside ed
applica ion, and only needs g id cu en and g id ol age mea-
su emen s (i.e., no addi ional LCL fil e senso s a e needed).
This is achie ed by a model- e e ence app oach, whe e, a e
designe specifies a desi ed admi ance e e ence, an H∞
syn hesis algo i hm will ob ain he (sub)-op imal con olle
ha shapes he sys em admi ance, in he equency domain, o
ollow he gi en e e ence. By defining a esis i e admi ance
e e ence he esonance can be e ec i ely damped, and ela ed
s abili y p oblems a e a oided. Cu en con ol design o
achie e his goal is explained.
Expe imen al es o he ob ained con olle a e done and
hei esul s a e shown. P oposed me hod shows good cu en
acking and esonance damping capabili ies. The la e is
p o ed expe imen ally in bo h equency and ime domains.
Mo eo e , damping echnique is demons a ed ( heo e ically)
e ec i e e en unde ex emely high g id impedance, wi h bo h
good phase and gain ma gins.
Fu u e wo ks will s udy he esonance damping and s abili y
obus ness unde fil e and g id modelling unce ain ies, and
how hey a e a ec ed by he addi ion o di e en con ol
measu emen s (like fil e capaci o ol age o con e e side
cu en ).
ACKNOWLEDGEMENT
This wo k o he Uni e si y o Alcala g oup was sup-
po ed in pa by he spanish esea ch p ojec s CONPOSITE
(ENE2014-57760-C2-2-R Minis e io de Economía y Com-
pe i i idad) and PRICAM (S2013/ICE-2933 Conseje ía de
educación, ju en ud y depo e de la Comunidad de Mad id).
The wo k o Robe G iñó was suppo ed in pa by he
Spanish Resea ch P ojec DPI2013-41224-P.
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