Dimitar Bozalakov

Ghent University | UGhent · Department of Electromechanical Systems and Metal Engineering

In this research, the performance of vanadium redox flow batteries (VRFBs) in grid-connected energy storage systems centering on frequency and power sharing using voltage source inverters was evaluated. VRFBs are increasingly promising due to their scalability and long lifespan. We explore the impact of voltage source inverters on the frequency of...

Proton exchange membrane (PEM) electrolyser stands as a promising candidate for sustainable hydrogen production from renewable energy sources (RESs). Given the fluctuating nature of RESs, accurate modelling of the PEM electrolyser is crucial. Nonetheless, complex models of the PEM electrolyser demand substantial time and resource investments when i...

This paper presents a scheme for the production of green molecules at sea. Since RESs exhibit a fluctuating output power, their intermittency could be effectively accommodated by using electrolysers. This study focuses on the production of green molecules at sea, taking advantage of the benefits offered by the seawater. To this end, the feed water...

The study deals with the techno-enviro-economic aspects of hydrogen production using polymer electrolyte membrane electrolysers powered by a hybrid grid-connected tidal-wind energy system. System modelling is presented initially. The energy management strategies for hydrogen production are then analysed as rule-based approach and as optimised appro...

Following the urgency of climate change issues, investments in renewable energy sources and electrification of the transportation sector have enormously increased to facilitate the transition to a more sustainable future. However, as renewable resources like wind parks are replacing conventional power plants, new balancing solutions are required to...

Renewable Energy Sources (RES) have drawn significant attention in the past years to make the transition towards low carbon emissions. On the one hand, the intermittent nature of RES, resulting in variable power generation, hinders their high-level penetration in the power system. On the other hand, RES can aid not only to supply much more eco-frie...

Among renewable energy sources, wind energy is one of the most promising ones. However, small and medium wind turbines need to cope with the natural intermittent nature of wind speed at lower altitudes. This imposes challenges on optimally tracking the Maximum Power Point (MPP) of the turbine. Up to now, various MPPT techniques have been proposed....

Among renewable energy sources, wind energy is one of the most promising ones. However, small and medium wind turbines need to cope with the natural intermittent nature of wind speed at lower altitudes. This imposes challenges on optimally tracking the Maximum Power Point (MPP) of the turbine. Up to now, various MPPT techniques have been proposed....

Distributed generation (DG) allows the production of renewable energy where it is consumed, avoiding transport losses. It is envisioned that future DG units will become more intelligent, not just injecting power into the grid but also actively improving the power quality by means of active power filtering techniques. In this manner, voltage and cur...

Accurate knowledge of the induction machine rotor temperature is important for both condition monitoring and motor performance. Lumped-parameter thermal networks allow to flexibly model the temperature distribution with low computational effort. However, their accuracy highly depends on the accuracy of their thermal parameters. Moreover, these para...

This paper presents an optimisation model to assess the techno-economic feasibility of a hydrogen refuelling station, which purchases power from the electricity market, supplies the mobility sector with hydrogen, and participates in the ancillary service market. The problem is formed as a mixed-integer nonlinear programming model to investigate the...

As the share of renewable energy sources increases, the grid frequency becomes more unstable. Therefore, grid balancing services will become more important in the future. Dedicated devices can be installed close to the point where offshore wind farms are connected to the transmission grid on land. There, they can be used to attenuate power variatio...

The share of renewable energy is increasing because of environmental concerns and favorable economic conditions. The majority of the distributed energy resources, connected to the low-voltage grid, are inverter-connected units. These inverters are controlled by using specially developed control strategies to determine the power injection between th...

The energy from solar can easily harnessed to be used for various applications and grid injection. For cooking, different techniques can be utilized. Some people use the sun to cook. Other people use batteries and inverters even at noon. Hence, the cooking system becomes expensive. In fact, Photovoltaic panels did not decrease considerably in price...

This article proposes a recent Adaptive Predictive (AP) control technique applied to a DC-DC buck converter. This converter topology has a wide range of applications in the current electronic and electrical systems that demand an efficient use of low bus voltage and specific requirements in load current consumption. Nevertheless, this converter, an...

Resonant wireless power transfer (RWPT) allows for efficient transfer of electrical energy over an air gap, by optimally tuning a receiver resonator. Next to transferring electrical energy to supply or charge a device, previous work demonstrated that the induced current in receiver resonators can be directly applied to exert mechanical torque on a...

In a decarbonised economy, hydrogen could be a promising energy carrier, mainly for the transportation sector. Using hydrogen-filled vehicles can decrease air pollution and greenhouse gas emission. One of the requirements for the implementation of hydrogen as a fuel for the transportation sector is a focus on the optimal design of hydrogen refuelli...

To meet the demand for increasingly high power density in electric drives, the concept of a so-called integrated modular motor drive has emerged. The machine is composed of multiple identical modules, which receive individual control signals for multiphase control, to reduce unwanted stator current harmonics. Each module is equipped with its own po...

In Belgium, and many other countries, rooftop solar panels are becoming a ubiquitous form of decentralised energy production. The increasing share of these distributed installations however imposes many challenges on the operators of the low-voltage distribution grid. They must keep the voltage levels and voltage balance on their grids in check and...

Accurate temperature estimation inside an electrical motor is key for condition monitoring, fault detection, and enhanced end-of-life duration. Additionally, thermal information can benefit motor control to improve operational performance. Lumped-parameter thermal networks (LPTNs) for electrical machines are both flexible and cost-effective in comp...

ITEG will develop and validate an integrated hydrogen production solution for clean energy generation and storage in remote areas facing grid export limitation. Project objectives: • Open up new market opportunities for the ocean energy sector through energy storage • Optimise the EMS and fast-track the integrated solution towards commercialisati...

The demand for ever increasing efficiency keeps challenging the design and control of electrical machines. Thermal monitoring is in that perspective an important addition to the electromagnetic aspect. Temperature measurements in electrical machines can be challenging, especially in high-frequency inverter-fed motors. High dv/dt ratios in the stato...

Squirrel-cage induction machines with Indirect Field-Oriented Control are widely used in industry and are frequently chosen for their accurate and dynamic torque control. During operation however temperature rises, leading to changes in machine parameters, particularly the rotor resistance, that affect the accuracy of torque control. We investigate...

Thermal modeling of induction machines is becoming increasingly important to improve the operational efficiency and performance. Lumped-Parameter Thermal Networks are both flexible and suitable for online use, but their parameters must be well identified to obtain accurate temperature predictions. The convection coefficient between the motor frame...

The GREENPORTS project aims to develop a comprehensive model of the power system based primarily on both onshore and offshore wind energy and hydrogen produced by proton exchange membrane (PEM) water electrolysis, assuming an ability of the electrolyser to provide balancing services to the power grid. The results will be implemented in a pilot case...

In this paper, a new smart monitor and control system has been designed for injected power application to grid from a three-phase photovoltaic inverter (a smart monitor and control system (SMCS)). The system consists two main units. Firstly, the control system unit: this unit connects directly to the inverter to measure the output voltage of three-...

This paper presents and describes the design and implementation of a new gate driver circuit for a three-phase grid tide photovoltaic inverter system using SIC- MOSFET at the power stage. The proposed design consists of a 5 kW power threephase inverter system with a new isolated gate driver related to IGBT, MOSFET and SIC-MOSFETs. The designed circ...

The increased utilisation of distributed renewable energy sources in low voltage grids leads to power quality problems such as overvoltages and voltage unbalance. This imposes challenges to the distribution system operators to maintain the power quality in their grids. To overcome these issues, energy storage systems could be integrated together wi...

The increasing penetration of renewable energy resources imposes challenges to the distribution system operators to maintain the voltage levels and voltage unbalance within limits. The voltage control by means of reactive power in low voltage grids becomes ineffective due to the mainly resistive feeders. In this article, the performance of some cla...

This paper presents and describes the design and implementation of a new gate driver circuit for a three-phase grid tide photovoltaic inverter system using SIC- MOSFET at the power stage. The proposed design consists of a 5 kW power three-phase inverter system with a new isolated gate driver related to IGBT, MOSFET and SIC-MOSFETs. The designed cir...

The constantly decreasing prices of the battery storage systems make them a very attractive solution for mitigating overvoltages and voltage unbalance in low voltage grids with high penetration of renewable energy resources. A centralised storage device, connected at the end of the feeder can be a very effective solution for dealing with overvoltag...

Nowadays, most three-phase, "off the shelf" inverters use electrolytic capacitors at the DC bus to provide short term energy storage. However, this has a direct impact on inverter lifetime and the total cost of the photovoltaic system. This article proposes a novel control strategy called a 120 ∘ bus clamped PWM (120BCM). The 120BCM modulates the D...

Three-phase grid synchronization is one of the main techniques of the three-phase grid connected power inverters used in photovoltaic systems. This technique was used to reach the fast and accurate three-phase grid tied inverter synchronization. In this paper a new synchronization method is presented on the basis of integrating the grid voltage two...

The constantly increasing interest towards the electric and plug-in hybrid electric vehicles will increase the voltage unbalance and overvoltages in the distribution grids and therefore, the power quality of the grid voltage might be put in a danger. To overcome this issue more sophisticated control strategies for the battery chargers must be used...

In this paper, a new smart system has been designed that can monitor and control the power injected to grid from a three-phase photovoltaic inverter (a smart monitoring and controlling system (SMCS)). The system is designed as two units. Firstly, the control system unit: this unit connects directly across the inverter in order to measure the status...

This paper presents a new operating type of a three phase photovoltaic PID current control system connected to the low voltage distribution grid. This operating type introduces a 120-degree bus clamp PWM control method (120° BC-PWM). A 120° BC-PWM is a special switching sequences technique employing bus clamp sequences that use only one phase under...

This paper presents a new operating type of a three phase photovoltaic PID current control system connected to the low voltage distribution grid. This operating type introduces a 120-degree bus clamp PWM control method (120° BC-PWM). A 120° BC-PWM is a special switching sequences technique employing bus clamp sequences that use only one phase under...

Nowadays, most three-phase, “of the shelf” inverters use electrolytic capacitors at the DC bus to provide short term energy storage. However, this has a direct impact on inverter lifetime and the total cost of the photovoltaic system. Tis article proposes a novel control strategy called a 120∘ bus clamped PWM (120BCM). Te 120BCM modulates the DC bu...

The increasing share of single-phase distributed generation units in low voltage grids causes voltage unbalance problems and overvoltages. Therefore, the need for power quality improving control strategies of grid-connected inverters emerges. Some control strategies require three-phase four-wire inverter topologies. The simplest way to connect the...

In three-phase Low Voltage (LV) networks, distributed photovoltaic (PV) units can contribute to voltage unbalance mitigation in case they are connected with the use of three-phase inverters integrating unbalance mitigation control schemes. This paper presents a probabilistic framework that simulates the time-varying action of voltage magnitude and...

The increased penetration of renewable distributed energy sources increases the challenges for distribution systems operators to keep the voltage variations within the prescribed limits. One of the voltage problems is caused by single-phase systems leading to voltage unbalance. Another problem is overvoltages caused by local injection of distribute...

This paper applies a long term network observability analysis for investigating the potential contribution of photovoltaic (PV) inverters to the mitigation of voltage unbalance in low voltage (LV) feeders. For this purpose, a probabilistic offline state estimation algorithm is used, which simulates the time-varying action of local voltage (magnitud...

In this paper, a new software tool is presented for the simulation of electrical networks under steady-state conditions. Its distinct advantage is the robust integration of distributed generation droop controls, while offering the ability to simulate extended networks fast and reliably. The proposed simulation tool is based on the combination of tw...

Because of the increasing penetration of distributed generation (DG) units, distribution system operators are faced with significant challenges such as voltage and congestion problems. This has led to continuously evolving grid interconnection requirements for DG. One of these requirements is the voltage support by DG units during voltage dips. In...

Die elektromagnetische Umformung (EMU) ist eine innovative Technologie für die Formgebung sowie für das Fügen und Trennen durch Umformung. Sie basiert auf der Nutzung elektromagnetischer Kräfte und bietet aussichtsreiche Möglichkeiten für: -Das Erreichen höherer Umformgrade im Vergleich zu konventionellen Umformverfahren für zahlreiche Werkstoffe,...

In this article, a high voltage two channel differential probe has been developed and tested in order to satisfy the requirements of power electronic measurements. The bandwidth of at least 10MHz is verified using a 50MHz sine wave generator. Voltage edges at 5V/ns like in real converters generated from a DC chopper are also applied and the probe i...

The paper presents a study of an improved heat sink structure for semiconductor switches with increased heat dissipation capabilities. The study involves a conventional heat sink modified by introducing a small chimney on top of the component that is being cooled. This creates a local air flow due to the chimney effect, where the hot air is sucked...

In this article a three-phase BLDC motor controller for use in an Ultra-Light Electrical Vehicle is presented. The control is performed using a Programmable Logic Device (CPLD), which doesn't require any additional processor. In this way a robust and low-complexity control is obtained. For extending the speed range of the BLDC, a phase advance circ...