Matej Krpan

• Doctor of Philosophy
• HVDC System Performance Engineer at Hitachi Energy

Wind power generation has reached a significant share in power systems worldwide and will continue to increase. As the converter-connected generation reduces the grid inertia, more and more interest has been given to exploiting the kinetic energy and controllability of variable-speed wind turbine generators (VSWTGs) for frequency support. Consequen...

Power converter technology partially or fully electrically decouples the wind energy source from the grid which results in the decrease of system inertia. However, when those units participate in virtual inertial response their electromechanical dynamics become coupled to the grid electromechanical modes. To date, there were no comprehensive studie...

The paper presents accurate and simple dynamic model of a supercapacitor bank system for power system dynam- ics studies. The proposed model is derived from a detailed RC circuit representation. Furthermore, a complete control system of the supercapacitor bank is also presented. The proposed model is easy to integrate in any power system simulation...

This paper presents a nonlinear dynamic simulation model of an ultracapacitor (UC) bank and the associated control system. The control system at hand consists of two levels: the lower level controls the inverter of the UC bank, while the upper control level is responsible for providing charging/discharging active power set points to be followed by...

Ovo je pregled teme istraživanja za kvalifikacijski doktorski ispit. U radu je dan osvrt na problem regulacije frekvencije i radne snage u sustavima s visokim udjelom OIE spojenih preko sučelja energetske elektronike s naglaskom na vjetroelektrane. Zatim, prikazan je pregled modeliranja vjetroelektrana za potrebe dinamičkih simulacija EES-a. Na kra...

This paper presents the results, insights and challenges of a small-scale laboratory implementation of a virtual storage plant (VSP) and the distributed control of its portfolio for frequency restoration services. The proposed framework has been experimentally validated using a controller-hardware-in-the-loop setup consisting of 5 battery storage s...

The increasing share of power converters in power systems is changing the power system dynamics. Increased penetration of converter-interfaced renewable energy sources reduces the inertia of the power system and introduces new interactions among the converters and the rest of the power system. This thesis is aimed at evaluating the impact of increa...

The massive penetration of distributed energy resources (DER) encourages the provision of frequency regulation services at the distribution network level following large frequency disturbances occurring at the transmission system side. The availability of reduced-order or aggregated models will facilitate the coordination between transmission and d...

The paper presents a detailed analysis and comparison of proton exchange membrane fuel cell (PEMFC) models with different levels of complexity. Since the full PEMFC model is highly nonlinear and depends on numerous technical parameters that are not usually readily available, this paper investigates the adequate complexity level of the PEMFC model f...

Contrary to microgrids (MGs) for which grid code or legislative support are lacking in the majority of cases, energy communities (ECs) are one of the cornerstones of the energy transition backed up by the EU’s regulatory framework. The main difference is that, unlike MGs, ECs grow and develop organically through citizen involvement and investments...

Power system operators are increasingly procuring frequency regulation reserves from distributed energy resources via aggregators. Provision of the frequency regulation services by the aggregators can be studied from different aspects and by using different models, ranging from very-short-run to long-term scheduling models. By developing a methodol...

U radu su opisane aktivnosti vezane uz istraživanje i razvoj naprednih metoda za regulaciju elektroenergetskog sustava u Laboratoriju za napredne elektroenergetske mreže. Fokus rada je na rezultatima Horizon 2020 projekta „CROSSBOW“ u sklopu kojeg se vršila eksperimentalna validacija distribuiranog upravljanja spremnicima energije za regulaciju fre...

This paper proposes a sound separation methodology based on deep learning neural network (DLNN) to extract useful diagnostic material in non-invasive audio-based On-Load Tap Changer (OLTC) diagnostics. The proposed methodology has been experimentally verified on both artificial mixtures (created by reproducing the targeted data by the speakers plac...

U radu je opisana koncepcija bivšeg Laboratorija za električna postrojenja na Fakultetu elektrotehnike i računarstva Sveučilišta u Zagrebu (FER) te njegova transformacija u Laboratorij za napredne elektroenergetske mreže (engl. Smart Grid Laboratory – SGLab). Model elektroenergetskog sustava (EES) u laboratoriju odgovara trenutnom i budućem energet...

The share of renewable energy sources interfaced to the bulk power system through power electronic devices is continuously increasing. As a result, the power systems of the future face challenges of stability and reduced inertia and, to maintain the stability of the low-inertia systems, various concepts of grid-forming converter control schemes hav...

The share of renewable energy sources interfaced to the bulk power system through power electronic devices is continuously increasing. As a result, The power systems of the future face challenges of stability and reduced inertia and, to maintain the stability of the low-inertia systems, various concepts of grid-forming converter control schemes hav...

In this paper, we explore the issues of sizing, modelling and controlling a supercapacitor ESS (SESS) for power system applications. We give an overview of different supercapacitor models used in literature. We present a simple method for sizing a SESS taking into account a realistic supercapacitor model, calculate the energy yield and voltage prof...

This paper presents a nonlinear dynamic simulation model of an ultracapacitor (UC) bank and the associated control system. The control system at hand consists of two levels: the lower level controls the inverter of the UC bank, while the upper control level is responsible for providing charging/discharging active power set points to be followed by...

This paper proposes a sound separation methodology based on deep learning neural network (DLNN) to extract useful diagnostic material in non-invasive audio-based On-Load Tap Changer (OLTC) diagnostics. The proposed methodology has been experimentally verified on both artificial mixtures (created by reproducing the targeted data by the speakers plac...

This paper presents a high-level overview of the integration of renewable energy sources (RES), primarily wind and solar, into the electric power system (EPS) in Croatia. It presents transmission system integration aspects for the particular case of this country. It explains the current situation and technical characteristics of the current convent...

U ovom referatu se predstavlja nelinearni dinamički model superkondenazatora s odgovarajućim upravljačkim sustavom. Predloženi upravljački sustav sastoji se od dva upravljačka sloja: donji upravljački sloj upravlja pretvaračem dok je gornji upravljački sloj odgovoran za pružanje postavnih vrijednosti djelatne snage za punjenje/pražnjenje koje će po...

Increased wind energy penetration influences the power system dynamic response to transient disturbances. Replacement of conventional production units with converter-connected wind turbines reduces natural power system inertia contained in rotational masses of synchronously connected turbine-generator units, therefore creating low-inertia power sys...

This paper proposes a method to define the value of an emergency service which the microgrid can provide both to the system operator and its own users. This means the microgrid operates as a market-driven grid-tied energy community. However, it also needs to be able to disconnect from the main grid and maintain stable operation in the off-grid regi...

This paper proposes a method to define the value of an emergency service which the microgrid can provide both to the system operator and its own users. This means the microgrid operates as a market-driven grid-tied energy community. However, it also needs to be able to disconnect from the main grid and maintain stable operation in the off-grid regi...

Generic dynamic models of hydraulic turbines are unable to capture power oscillations phenomena originating from a torque disturbance on a single runner blade. In this paper, an improved dynamic model of a double-regulated hydraulic turbine which takes into account torque oscillations identified from draft tube pressure measurements was presented....

The paper introduces, describes and analyses the specific power oscillations in hydroelectric power plant Dubrava that can appear in large bulb turbines operating with low tailwater levels. The procedure for the identification of the cause of oscillations is described and it is experimentally shown that the cause of power oscillations is a disturba...

The paper will present the process of the planned grid connection scheme optimization for wind power plants. At start the overview of the current status and trends will be observed alongside a short description of the Croatian power system specifics. The special highlight will be given to the wind energy integration. Following, the potential proble...

The paper presents accurate and simple dynamic model of a supercapacitor bank system for power system dynamics studies. The proposed model is derived from a detailed RC circuit representation. Furthermore, a complete control system of the supercapacitor bank is also presented. The proposed model is easy to integrate in any power system simulation s...

It has been over two decades since the publication of pioneer works about the power transformer diagnostics based on monitoring of their acoustic fingerprints. Since then, there has been a great progress in this field and the methods used are as complex as ever. Any unnecessary intervention on a power transformer implies its temporary disconnection...

In a power system, increased wind energy penetration changes the dynamic system response to active power disturbances. Due to the lack of natural inertial response from converter connected wind sources, an advanced converter control is required for maintaining a transient frequency stability of modern power systems with high shares of renewable ene...

Enabling the type-II and type-IV wind turbine generators to participate in grid frequency control couples them to the electromechanical modes of the grid. In this paper we have investigated how initial wind speed, rotor-side controller parameters, PLL parameters and pitch angle controller parameters influence the virtual inertial response and prima...

In the recent years, frequency support from converter-connected wind power generation has been a hot topic in the field of power system dynamics and control. At the same time, the share of wind generation in the power systems worldwide has significantly risen. Therefore, it is necessary to discuss a new approach to low-order system frequency respon...

Increase of converter-connected renewable power generation such as variable-speed wind turbines (VSWTs) decreases the system inertia constant, which reduces the frequency stability of the power system. Thus, it will be necessary to include these renewables in the inertial response and primary frequency control (PFC) of future power systems. In this...

Povećani udio vjetroelektrana s generatorima s promjenjivom brzinom vrtnje smanjuje konstantu tromosti elektroenergetskog sustava zbog razdvojenosti mehaničke brzine rotora turbine i mrežne frekvencije iako postoji određena količina kinetičke energije u lopaticama vjetroagregata. Posljednjih godina, sve se više istražuje iskorištenje te kinetičke e...

Danas se sve više elektrana na obnovljive izvore energije (OIE) na mrežu spaja preko frekvencijskih pretvarača koji razdvajaju mehaničku frekvenciju rotora i mrežnu frekvenciju čime se smanjuje konstanta tromosti sustava koja opisuje otpornost sustava na poremećaje radne snage. Posljedica smanjenja konstante tromosti je smanjena stabilnost frekvenc...

An increased share of variable speed wind turbines reduces the inertia of the power system due to the decoupling of mechanical rotor frequency and grid frequency. In the recent years, a lot of research has been done about exploitation of the rotating mass of a wind turbine for participation in the primary frequency regulation of the power system. T...

To enable conduction of quality research of power system dynamics using computer simulation software, appropriate mathematical and simulation models have to be developed. In the last two decades, an exponential increase of installed wind power capacity can be observed, while the gas power plant capacity and energy production has also seen an increa...

Synchronous generator theory has been known since the beginning of its use, but the modelling and analysis of synchronous generators is still very existent in the present-day. Modern digital computers enable development of detailed simulation models, thus individual power system elements, including synchronous generators, are represented by the hig...