liserre_lecture_6
lecture英语范文
lecture英语范文英文回答：Lecture.A lecture is a formal presentation delivered by an expert or specialist, typically in an academic or professional setting. The primary purpose of a lecture is to impart knowledge, convey information, or share insights on a specific topic. Unlike other forms of oral communication, lectures are usually one-sided, with the speaker assuming the role of an authoritative figure who imparts knowledge to the audience.Characteristics of a Lecture:Structured and well-organized: Lectures follow a logical flow of ideas, with an introduction, body, and conclusion. The speaker provides a clear outline or agenda to guide the audience through the presentation.Focused on a specific topic: Lectures are typically narrowly focused on a particular subject matter, allowing the speaker to delve deeply into the topic and present detailed information.Formal and authoritative: The speaker in a lecture is usually an expert or specialist in the field, showcasing their knowledge and expertise. The presentation is often formal in tone and delivery.One-sided communication: Lectures are primarily a one-sided form of communication, with the speaker delivering information to the audience. There is limited opportunity for audience participation or interaction.Note-taking and active listening: Attendees typically take notes during a lecture to record key points and enhance understanding. Active listening is also crucial for retaining information presented during the lecture.Benefits of Lectures:Imparting knowledge: Lectures effectively convey complex information to an audience, providing detailed explanations and examples.Sharing insights and perspectives: Experts can share their unique insights, perspectives, and the latest research findings through lectures.Building a foundation: Lectures lay the groundwork for further study or exploration of a subject, providing a comprehensive overview and key concepts.Improving comprehension: The structured nature of lectures helps learners organize and understand complex ideas.Inspiration and motivation: Lectures can inspire and motivate attendees, sparking interest and enthusiasm for the subject matter.Drawbacks of Lectures:Passive learning: Lectures can be passive experiences for attendees, limiting active engagement and critical thinking.Limited interaction: The one-sided nature of lectures restricts opportunities for audience participation and clarification.Short attention span: Maintaining attention during a long lecture can be challenging, especially if the content is not engaging or relevant.Cognitive overload: Lectures can overwhelm attendees with excessive information, hindering comprehension and retention.Cultural differences: Cultural factors can influence lecture delivery and audience engagement, affecting the effectiveness of the communication.Conclusion:Lectures are an effective form of knowledge dissemination in academic and professional settings. They enable experts to share their knowledge, provide in-depth information, and inspire audiences. However, it is important to acknowledge the limitations of lectures and incorporate interactive elements to enhance learner engagement and comprehension.中文回答：演讲。
Invited Lecture
8.4 ER-schemes
9 Conclusions and further research
We have introduced the use of translation schemes into database design theory. We have shown how they capture disparate notions such as information preservation and dependency preservation in a uniform way. We have shown how they relate to normal form theory and have stated what we think to be the Fundamental Problem of Database Design. Several resulting research problems have been explicitly stated in the paper. We have shown that the Embedded Implicational Dependencies are all needed, when we deal with stepwise re nements of database schemes speci ed by Functional and Inclusion Dependencies. As the material presented grew slowly while teaching database theory, its foundational and didactic merits should not be underestimated. Over the years our students of the advanced database theory course con rmed our view that traditional database design lacks coherence and that this approach makes many issues accessible to deeper understanding. Our approach via dependency preserving translation{re nements can be extended to a full edged design theory for Entity{Relationship design or, equivalently, for database schemes in ER-normal form, cf. MR92]. It is also the appropriate framework to compare transformations of ER-schemes and to address the Fundamental Problem of ER{Database Design. Translation schemes can also be used to deal with views and view updates, as views are special cases of translation schemes. The theory of complementary views from BS81] can be rephrased elegantly in this framework. It is connected with the notion of translation schemes invariant under a relation and implicit denability, Kol90]. Order invariant translation schemes play an important role in descriptive complexity theory, Daw93] and Mak94]. The theory of independent complementary views of KU84] exhibits some severe limitations on the applicability of BS81]. In spite of these limitations it seems worthwhile to explore the connection between independent views and transformation invariant for certain relations further. The latter two applications are currently being developed by the authors and their students and will be included in the full paper.
lecture 6
7. Please serve me ___D____ soup. A. more some B. the less C. more the D. some more
8. ____B____ alloy may be used to replace copper.
A. Such a
B. Some such
7〕 Determiners with plural and noncount nouns only a lot of, lots of, enough, more, most, such, other
1. Why is there ___A____ traffic on the streets in February than in may? A. less B. fewer C. few D. little
5. He was on leave ___D____ days. A. the few last B. few another C. few other D. the last few
6. ___B____ friends usually speak highly of him. A. His some B. His many C. Many his D. Some his
6.2 Collocation between Nouns and Determiners
1) Determiners with all three classes of nouns the, some, any, no, other, whose, my, your, John‘s,
my, friend’s
8. I’d like ____C____ paper. A. a few B. several C. a bit of D. these
经典常谈第六章作文300字左右
经典常谈第六章作文300字左右英文回答：In the sixth chapter of _The Long Tail_, Chris Anderson discusses the concept of "The Long Tail of Innovation." He argues that innovation is no longer limited to a few large companies, but is instead becoming increasingly distributed and democratized. This is due in part to the rise of the internet, which has made it easier for individuals and small businesses to access the tools and resources they need to innovate.Anderson identifies three key factors that are driving the democratization of innovation:1. The decline of the "gatekeepers" who used to control access to the market.2. The rise of new technologies that make it easier to create and distribute innovative products and services.3. The growing demand for niche products and services.As a result of these factors, Anderson believes that we are entering a new era of innovation, one in which anyone with a good idea can have a shot at success. This is a positive development, as it has the potential to lead to a more diverse and innovative economy.中文回答：在《长尾理论》的第六章中，克里斯·安德森讨论了“长尾创新”的概念。
Lecture_6
Galilean velocity transformation equation
Inertial frames of reference S' is moving at a velocity u with respect to another inertial frames of reference S.
2-3-2 Galilean principle of relativity
Galileo’s observation and understanding of the motion suffered two limitations: • within the realm of mechanics • the mechanical motions at very low speed: v « 299,792,458 meters per second Both of these two factors have greatly influenced Galileo’ s view of space and time and hence his concept of the principle of relativity.
The rigorous expression of the velocity transformation
dr dR dr ′ dR dr ′ dt ′ dt ′ v= = + = + ⋅ = u + v′ dt dt dt dt dt ′ dt dt
Galileo’s velocity transformation demands dt/dt’= 1, or
∆t = ∆t′
The central idea of Galileo’s concept of time: The time is absolute, the time interval is not rested upon the choice of the frame of reference.
trial_lecture
Trial Lecture
Demissie B. Aredo
March 3, 2005
Introduction to Formal Methods
State-of-the-Art FMs are not in the mainstream SW engineering Limitations of FMs in industrial settings Introducing FMs into SW Engineering Practice Success Criteria for Formal Methods
Taken from: [2] Richard Sharpe, Formal methods start to add up once again, Computing, January 8, 2004.
Demissie B. Aredo March 3, 2005, Oslo 6
Main Concepts of FMs
Demissie B. Aredo March 3, 2005, Oslo 4
Historical Timeline
1947-48: Von Neumann and Goldstine propose six-step programming process, starting with conceptualization of the problem mathematically 1959: Backus-Naur Form (BNF) for languages 1960: Hoare's Algol 60 compiler 1962: PetriNets 1969: Hoare's 'axiomatic basis’ 1973: IBM's VDM (Vienna Development Method), Cliff Jones 1978: Hoare's CSP (communicating Sequential Processes)
Liferay Portal 6学习笔记
Portlet
Portlet被定義成为一個新的組件，具有新的明確的界面與行为。为了盡可能與現有的Servlet結合達到重复使用的目的，Portlet的規範利用了Servlet的規範，許多觀念都很相似的，結合Portlet、Servlet及Jsp在同一個網站系統中，我們稱为Portlet應用。在同一個Portlet應用中，他們將分享同一個類加載器(ClassLoader)，上下文(Context)及Session。
權限控制:系統采用LDAP對用戶資源進行統一的管理，同時提供二次開發接口，可以與其他應用系統的用戶管理模塊對接，並能隨相關業務系統實時更新訪問權限。通過完善的授權機制及存取控制，用戶訪問權限控制到字段級別，確保用戶只能訪問具有權限的應用系統及相關信息。
內容管理:實現應用系統之間實時交換信息。采用多種緩存機制，保證內容交換的性能和准確性。采用基於XML的Rich Site Summary (RSS)標准，迅速在各應用系統之間傳播最新變化。
什麼是
Portlet是Portal中最重要的組件，負責在Portal中呈現信息內容，有相應的生命周期。通過自定義Portlet，用戶很容易定義個性化的Portal頁面。Portlet由Portlet容器負責管理、處理請求並返回動態頁面，可以作为Portal的可即插即用的界面組件。
Portlet
一個Portlet是以Java技術为技術的Web組件，由Portlet容器所管理，專門處理客戶的信息請求以及產生各種動態的信息內容。Portlet为可插式的客戶界面組件，提供呈現層成为一個信息系統。
学术英语(理工)_Unit 6 PPT课件
Academic English for Science and Engineering
Unit 6 Making an Oral Presentation
Unit Contents
1 Preparing your oral presentation 2 Organizing the content 3 Using proper language 4 Delivering your presentation 5 Using visual aids 6 Dealing with Q and A 7 Raising questions in class and in the lecture 8 Participating in discussions
Unit 6 Making an Oral Presentation
2 Organizing the content
1 Function: Describe the outline of the talk 2 Function: Introduce the topic 3 Function: Indicate the shift from one idea to another 4 Function: Give closing remarks 5 Function: Summarize the talk
Part 3 Conclusion.
a) Let the audience know that you are approaching the end of the presentation, by restating your purpose, and saying that you have achieved it. b) Leave your audience with a clear summary of the main points you have covered in the talk. c) Thank the audience. d) Give the audience a chance to ask questions.
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Stability of power converters connected to the gridthrough LCL-filtersMarco Liserreliserre@poliba.itOutline✓Grid converters connected through an LCL-filter✓LCL-filter resonance used to estimate the gid inductance ✓Passive damping methods✓current sensors on the converter side✓current sensors on the grid side✓design of the passive damping✓Active damping methods✓multiloop methods✓notch filter methods✓design of the active damping✓Influence of the conditions at PCCOutline✓Grid converters connected through an LCL-filter✓LCL-filter resonance used to estimate the gid inductance ✓Passive damping methods✓current sensors on the converter side✓current sensors on the grid side✓design of the passive damping✓Active damping methods✓multiloop methods✓notch filter methods✓design of the active damping✓Influence of the conditions at PCC101102103104105-70-60-50-40-30-20-100frequency (Hz)magnitude (Db)L 1L 1+L 2LCL()()swresLCsw sw g z h i h i 222ωω-≈ripple attenuationGrid converters connected through an LCL-filtervi REF M. Liserre, F . Blaabjerg e S. Hansen, “Design and Control of an LCL -filter basedThree-phase Active Rectifier” IEEE Transactions on Industrial Applications, Sept./Oct. 2005, vol. 41, no.5, pagg. 1281-1291.Grid converters connected through an LCL-filter102103-5050M a g n i t u d e [D b ]102103-300-200-1000100Frequency [Hz]P h a s e [G r a d ]✓The LCL-filter challenges the system stability✓There is a resonant peak associated to two resonant poles ✓Their position changes as the grid inductance changesv ga v gb v gc A/Di a i b i cA/Di g a i g b i g cA/Dv ca v cb v ccA/D Grid converters connected through an LCL-filterVSIdcv +-g v 1L vi2L Cv Cf C gL eg i +-+-+-✓Influence on the low frequency behavior ✓Influence on the high frequency behavior()()22221()1()()LC res s z i s G s v s L s s ω+==+()2212()11()()res i s G s v s L L Cs s ω==+current sensors on the converter sidecurrent sensors on the grid sideGrid converters connected through an LCL-filtergi VSIModulatorgv 1L vi2L Cv f C e*v +-+-Currentcontrol+-gL +-Ci VSIModulatorg v 1L vi2L Cv f C gL e*v g i +-+-Currentcontrol+-L2 L1VSC C fv c iCURRENTCONTROLL2C f Z bZ Tgrid Z TconvL1Z b(a)L2 L1VSC C fi g v cCURRENTCONTROLL2C fZ bZ Tgrid Z TconvL1Z b(b)L2 L1VSCC fi ge CURRENTCONTROL(c) L2 L1VSCC fie CURRENTCONTROL(d)()11Tgrid g CTconvz j x xz jx=+-=+()11Tgrid gTconv Cz jxz j x x=+=+-()11TgridTconv g czz j x x x==+--(c)(d)()()11Tgrid CTconvz j xz j x=+-=+-1 % error if x c is less than 10 %Grid converters connected through an LCL-filterREF M. Liserre, A. Dell’Aquila, F. Blaabjerg “Step-by-step design procedure for a grid-connected three-phase PWM Voltage Source Converter” International Journal ofGrid converters connected through an LCL-filter()a Cv gi VSIModulatorgv 1L vi2L Cv f C e*v +-+-Current control+-gL +-Ci Ci igi v1j L iω ()2g gj L L i ω+e()b C vg i VSIModulatorg v 1L vi2L Cv f C e*v +-+-Current control+-gL +-Ci Ci gi iv 1j L iω ()2g gj L L i ω+eGrid converters connected through an LCL-filter()cCvCigiiv1j L iω2gg gj L ij L iωωeVSI Modulatorgv1Lvi2LCvfCgLe*vgi+-+-Currentcontrol+-gv()dgiVSIModulatorgv1Lvi2LCvfC e*v+-+-Currentcontrol+-gL+-Ci CvCi-igiv1j L iω2gg gj L ij L iωωegvGrid converters connected through an LCL-filterDesign procedure1.Ripple analysis and converter-side inductor choice2.Harmonic attenuation of the LCL-filter and choice of the resonance frequency value3.LCL-filter optimization and choice of grid-side inductor, capacitor and damping method and value1.Installed reactive power of the filter2.Robustness of the filter attenuation, to the grid impedance variation3.The influence of the damping on the LCL-filter attenuation11dc MAXV I n L f∆=()()22221LCres i z i ωωωω≈-Grid converters connected through an LCL-filterInfluence of inductor saturationThe frequency behaviour of the non-linear inductance can be studied splitting the model in a linear part and a non-linear part in accordance with the Volterra theory .The V olterra-series expansion of the flux is ()()51i i t t ϕϕ=≈∑+-veL 1ii 1+-()111,...,n n n i i i L ϕ-=()2121i i L ϕ=()31231,i i i L ϕ=non-linear inductanceOutline✓Grid converters connected through an LCL-filter✓LCL-filter resonance used to estimate the gid inductance ✓Passive damping methods✓current sensors on the converter side✓current sensors on the grid side✓design of the passive damping✓Active damping methods✓multiloop methods✓notch filter methods✓design of the active damping✓Influence of the conditions at PCC21221112resres f g g C L L L L ωω⎛⎫∆=- ⎪⎪++⎝⎭Considering the closed loop current control where only a proportional controller is considered for the sake of simplicity()()()()2222222() 1.5g fg fP LC c sPres P L C res k s z G s LT sLs k sk z ωω+=++++-•Different grid impedances lead to different resonance frequencies that can be detected103-25-20-15-10-50510152025From: Input P oint To: Output P ointM a g n i t u d e (d B )resonance frequency 3230 Hzin case Lg=3.2 mHresonance frequency 3530 Hzin case Lg=1.2 mHUse of the LCL-filter resonance to estimate the grid inductance-1-0.50.51-1-0.8-0.6-0.4-0.200.20.40.60.810.05/T0.50/T 0.45/T 0.40/T 0.05/T 0.10/T 0.15/T 0.20/T0.25/T0.30/T 0.35/T0.50/T 0.35/T 0.30/T 0.25/T0.10/T 0.15/T 0.20/T0.80.90.45/T0.40/T0.30.10.20.70.40.50.6resonance frequency 3530 Hz in case Lg=1.2 mHresonance frequency 3230 Hz in case Lg=3.2 mH0.050.10.150.2-20-1001020time [s]c o n v e r t e r c u r r e n t [A ]10203040506070800246harmonic order a m p l i t u d e o f t h e h a r m o n i c s [A ]49th harmonic correspondingto 2450 Hz resonance frequencyUse of the LCL-filter resonance to estimate the grid inductance✓Different methods can be used to excite the system resonance, such as:✓increase the proportional gain of the current control;✓add other zeros and poles in the controller in order to push the LCL-filter poles out of the stability region;both methods change the resonance frequency of the closed loop system ✓saturate the ac voltage command for the PWM modulator it does not change the resonance frequency0.050.10.150.2-1-0.500.51time [s]m o d u l a t i n g s i g n a lEvaluation of the proposed algorithm2040608010000.020.040.06-1-0.500.5-1-0.500.510.91.6e30.80.70.60.50.40.33.6e34e30.10.24001.6e32e32.4e32.8e33.2e31.2e34001.2e33.6e34e38008002e32.4e32.8e33.2e3I m a g A x i sReal AxisRoot Locus E ditor (C)Experimental spectrum of the grid current SimulatedRoot locusTest in case the grid inductance is equal to 0 mHEvaluation of the proposed algorithmExperimental spectrum of the grid current SimulatedRoot locusTest in case the grid inductance is equal to 1.5 mH2040608010000.010.020.030.04-1-0.500.51-1-0.8-0.6-0.4-0.200.20.40.60.810.91.6e30.80.70.60.50.40.33.6e34e30.10.24001.6e32e32.4e32.8e33.2e31.2e34001.2e33.6e34e38008002e32.4e32.8e33.2e3I m a g A x i sReal AxisRoot Locus E ditor (C)Evaluation of the proposed algorithm2040608010000.020.040.06-1-0.500.5-1-0.50.510.91.6e30.80.70.60.50.40.33.6e34e30.10.24001.6e32e32.4e32.8e33.2e31.2e34001.2e33.6e34e38008002e32.4e32.8e33.2e3I m a g A x i sReal AxisRoot Locus E ditor (C)2040608010000.010.020.030.04-1-0.500.51-1-0.8-0.6-0.4-0.200.20.40.60.810.91.6e30.80.70.60.50.40.33.6e34e30.10.24001.6e32e32.4e32.8e33.2e31.2e34001.2e33.6e34e38008002e32.4e32.8e33.2e3I m a g A x i sReal AxisRoot Locus E ditor (C)0 mH1.5 mHREF M. Liserre, R. Teodorescu, F . Blaabjerg, “Grid impedance estimation via excitationof LCL-filter resonance” to be published on IEEE Transactions on IndustryOutline✓Grid converters connected through an LCL-filter✓LCL-filter resonance used to estimate the gid inductance ✓Passive damping methods✓current sensors on the converter side✓current sensors on the grid side✓design of the passive damping✓Active damping methods✓multiloop methods✓notch filter methods✓design of the active damping✓Influence of the conditions at PCCIncreasing the switching/samplingfrequency, the losses decrease but at the same time the damping becomes lessPassive damping: current sensors on the converter side()[]∑-=hg d d h i h i R P 2)(3lossesL 1L 2C fR dvv cei i gi c⎪⎪⎭⎫ ⎝⎛++⎪⎪⎭⎫ ⎝⎛++-=221222211)()(res d T LC d s L L R L s z s L R s s L s v s i ωmain terms of the sum are for the index h near tothe multiples of the switching frequency order.As the damping resistor increases , both stability is enforced and the losses grow but at the same time the LCL-filter effectiveness is reduced .-1-0.50.51-1-0.50.51Rd=0Rd=16Rd=wr*LgFrequency [Hz]102103-300-200-1000100D(z)G(z)D(z)Gd(z)Phase [deg]-5050D(z)G(z)D(z)Gd(z)Magnitude [dB]102103root locusbode plotPassive damping: current sensors on the converter side-1.5-1-0.500.51 1.5-1.5-1-0.50.511.50100200300400500-1001050100150200250300350400450500-15-10-5051015converter side currentPassive damping: current sensors on the converter side304050-100damping resistor value [Ω]d c u r re n t [A ]202530354045501591011100200300010200 2.3%THD 4%0.8%THFHD 1.9%29 Wlosses 67 WExcessive damping45678-2020grid currentPassive damping: current sensors on the converter sideroot locus-1-0.50.51-1-0.500.51pole introduced by the delayreduction of the bandwidth from 350 Hz to 200 Hz Good method to reduce losses in high power applications at the price of a slow down of the dynamicPassive damping: current sensors on the converter side REF M. Liserre, A. Dell’Aquila, F . Blaabjerg "Stability improvements of an LCL -filterbased three-phase active rectifier”, PESC 2002, Cairns, Australia, June 2002.-1-0.500.51-1-0.50.51k maxk max k optimumk optimum-1-0.500.51-1-0.50.51k max k optimumk maxk optimum undampedpassively dampedStable without damping !Passive damping: current sensors on the grid sidePassive damping + one sample delayundampedpassively damped-1-0.50.51-1-0.50.51k optimumk optimum-1-0.50.51-1-0.50.51k optimum k optimumk maxk maxDesign algorithm: constraints✓for the stability: ρMAX-maximum radius of poles of the current closed loop -ρMAX should be at least < 1 in order to have a stable current loop;✓for the bandwidth: bw–the lowest between the frequencies at which the gain of the closed loop isreduced to 3 dB and at which the phase delay becomeslarger than 45°;✓for the LCL-filter switching ripple attenuation: ra;✓for the damping losses: P d.Design algorithm: parameters✓the current controller proportional gain k p;✓the sampling frequency f sampling;✓the damping resistor value R d.ρMAX is a function of all the three parameters but especially of the last two in a non-linear way,bw depends strongly and almost linearly on the second parameter,Pd depends on the last two of them in a non-linear wayra depends especially on the second of them.thus a step-by-step algorithm can be writtenUse of a non-linear least-mean-square method✓a non-linear least-mean-square method can be adopted in order to find the optimal solution without linearising the relations: ρMAX (k p , f sampling , R d ), bw (k p , f sampling , R d ), ra (k p , f sampling , R d ), Pd (k p , f sampling , R d )✓It has been chosen to use the Levenberg-Marquardt method in conjunction with the linear search.✓The Levenberg-Marquardt method uses a search direction which is a solution of a linear set of equations. The line search is based on the solution of a sub-problem to yield the search direction in which thesolution is estimated to lie. The minimum along the line formed from this search direction is approximated by a polynomial method involvinginterpolation. Polynomial methods approximate a number of points with a polynomial whose minimum can be calculated easily✓The method gives good results if the optimal solution is near the initial conditions.Dynamic testStart of rectifying mode at full load (a); no load (b)(a)(b)settling time of 30 msDynamic testStep load change from no load to 4 kW load (a); and from no load to nominal load (11 kW) (b)(a)(b)REF R. Teodorescu, F . Blaabjerg, M. Liserre, A. Dell’Aquila, “A stable three -phase LCL-filter based active rectifier without damping” IAS 2003, USA, October 2003.Outline✓Grid converters connected through an LCL-filter✓LCL-filter resonance used to estimate the gid inductance ✓Passive damping methods✓current sensors on the converter side✓current sensors on the grid side✓design of the passive damping✓Active damping methods✓multiloop methods✓notch filter methods✓design of the active damping✓Influence of the conditions at PCCActive damping✓Obtain stability without additional losses✓Modify the control algorithm✓Various techniques based also on the use of more sensors ✓Two main possibilities:✓Multiloop✓Notch filterActive damping✓multiloop (use of more sensors)✓notch filter in cascadeActive dampingactive damping plug-inActive damping: lead networkαd M A X T f 1=ααφ+-=11arcsinM A X()()ddddk s L T f k s L T f 1011=→≥=→<α11)(++=s T s T k s L d d dαlead network-40-20020050100kdzFrequency [Hz]102103Phase [deg]Magnitude [dB]102103principle of operationActive damping: lead network✓The increase of the lead ratio increases the phase lead but it produces higher amplifications at higher frequencies α1✓adopting a low-pass filter ,it is possible to select a high phase margin (80°)around the resonance frequency (2.5kHz)T d = 5.6*10-4α= 1.2*10-2k d has to be chosen both on damping anddynamic considerationsdiscretization →oodzp z z z k z L ++=)(Active damping: lead networkInstead of a low-pass filter it is enough to select carefully the lead network position)()(11)(1z E z L z z D d --=()()2211resf s LC s E ω+=i*_+D(z)G(z)1-zi++1-zE(z)D d (z)L(z)v c=1for f < 1.8 kHz because of the lead network1for f > 4 kHz because of introduce phase lead for f ∈[1.8 ÷4] kHzActive damping: lead network-1-0.50.51-1-0.50.51kdz=0kdz=1kdz=1 kdz=0.6 kdz=0.6 kdz=0k dz = 0.6•best damping•good dynamicActive damping: lead network102103-5050M a g n i t u d e [D b ]102103-300-200-1000100Frequency [Hz]P h a s e [G r a d ]D(z)Dd(z)G(z)D(z)G(z)Dd(z)Reduction of the unstable peak under 0 dBActive damping: lead network0.20.40.60.81-300-200-1000100200300400lead network gain k dzd c u r re n t [A ]THD = 1.6% THFHD = 0.6%0.30.320.340.360.380.4-20-1001020g r i d c u r r e n t [A ]lead network gain k dzoptimum steady-state performanceDynamic performances0.150.160.170.18-10-50510152025time (s)d c u r re n t [A ]0.150.160.170.18-10-50510152025time (s)d c u r re n t [A ]0.150.160.170.18-10-50510152025d c u r r e n t [A ]time (s)0.150.160.170.18-10-50510152025d c u r re n t [A ]time (s)Passive damping 16 ΩPassive damping 8 Ω+one delayActive damping Active damping(capacitor voltage used also for dq-frame orientation)REF M. Liserre, A. Dell’Aquila, F . Blaabjerg "Stability improvements of an LCL -filterActive damping: use of a notch filterCurrent controlleri d*i d i q i =0q *PIL PIL-++e dv d,av v q,avu d u qe q+++----dq abcA C T I V E D A M P I N Gnomore sensorsdifficultto tuneundampedactive damped 2222()o AD o z z G z z p ⎡⎤-=⎢⎥-⎣⎦Active damping: use of a notch filterRoot locus of the undamped system-202-202-202-202converter side currentsensorsgrid side currentsensorsRoot locus of the undamped system with one delayconverter side currentsensorsgrid side currentsensors-202-22-202-202Root locus of the passive damped systemconverter side currentsensorsgrid side currentsensors-202-202-202-202Genetic algortihms✓The Genetic Algorithm (GA) simulates Darwin’s theory on natural selection and Mendel’s work in genetics on inheritance: the stronger individuals are likely to survive in a competing environment.✓In short the GA finds the optimum solution combining a set of randomly chosen solutions. In the following the term “individual” indicates the possible solution, the terms “gene” indicates one of the parameters of the solution and the “fitness value” indicates the degree of goodness of the individual.Genetic algortihmsThe GA process is performed through the following iterative steps:1.selection the individuals are selected on the basis oftheir fitness value to reproduce in the mating pool;2.crossover each new individual is generated by twothat are reproducing.This process is performedusing part of the genes characterising eachindividual;3.mutation is the way to randomly produce newcharacters in the new individual of the population,by changing one of its genes.Use of genetic algorithm for active damping optimisation ()()()()()()()()()()()4324321043243210d i a i z a i z a i z a i z a i D z b i z b i z b i z b i z b i ++++=++++()()()(1)1sp p IiT k i z k i T D z z -++=-Stability : active damping filterDynamic : PI current controller。