Abhisek Ukil

University of Auckland · Department of Electrical & Computer Engineering

The rapid discharge of the dc-link capacitors during the short-circuit fault would cause the transient current with fast propagation speed in the VSC based dc system. It is necessary to limit the dc fault current and lower the requirement of fault detection speed. However, the traditional fault current limitation method with directly installed indu...

The challenge of denial of service attacks (DoS) on distributed communication channels of multi battery energy storage systems (MBESSs) in a microgrid is discussed in this article. It is important to note that DoS attacks may prevent information from being shared between agents by stopping from transferring data, putting the devices in danger and j...

Due to the difficult topography and bad weather conditions across large distances, dc line breakdown is a serious danger to the safety of high-voltage direct-current systems (HVDC). Thus, there is a need of an accurate and reliable fault location method to safely isolate the dc grid in the occurrence of a dc fault. Travelling wave (TW) fault locati...

Heating, ventilating and air-conditioning systems have a significant share in the energy consumed by buildings. Modeling of room temperature dynamics is the first-step in designing an efficient air-conditioning system. In this regard, this paper proposes a semi-nonlinear thermal model: ordinary differential equation, with parameters as nonlinear fu...

In voltage source converter (VSC) based low voltage DC systems (LVDC), the fault current of the DC-link capacitor is considerably high and destructive to system infrastructure. It is necessary to develop effective fault detection methods with sufficient sensitivity and accuracy. To achieve these targets, a complex domain analysis based fault detect...

This paper presents a detailed investigation of an emergency power supply that enables solar photovoltaic (PV) power integration with a battery energy storage system (BESS) and a wireless interface. Through the utilisation of solar PV-based generation and BESS with wireless/contactless power transmission , the proposed method offers an easy-to-setu...

Theme: Aiming to the sustainable economic development and coping with the climate change and energy crisis, the energy storage systems (ESSs) have been worldwide developed and adopted with the applications of renewable energy, electric vehicles (EV), green buildings, etc. ESSs involves various technologies, which yield different devices, including...

This article introduces a way to optimize the power output of a photovoltaic (PV) system by implementing a maximum power point tracking (MPPT) technique. The algorithm is based on adaptive particle swarm optimization (APSO) under partial shading conditions (PSC). APSO aims to solve the issue that conventional MPPT algorithms cannot track the optima...

This study utilizes neural networks to achieve maximum power point tracking in photovoltaic systems. After Bayesian optimization of the hyperparameters, the model can accurately determine the maximum power point voltage based on solar irradiance and temperature, enabling optimal power output from the photovoltaic system under uniform irradiance, st...

This article introduces a way to optimize the power output of a photovoltaic system by implementing a maximum power point tracking (MPPT) technique. The algorithm is based on adaptive particle swarm optimization (APSO) under partial shading conditions (PSC). APSO aims to solve the issue that conventional MPPT algorithms cannot track the optimal glo...

Solar energy with battery storage has enormous potential for residential power supply applications. However, the installation is often complicated with lots of wiring. The wireless power transfer (WPT) interface can greatly reduce the complicated wiring part, facilitating easier installation, with additional benefits like electrical isolation, lowe...

Due to the lack of zero-crossing in dc current and the rapid discharging of the dc-link capacitor, a typical fast-growing transient current will be generated after the dc fault inception in VSC interfaced dc power system, which may affect the dc grid operation and damage power electronics equipment. Therefore, a novel fault detection method with fa...

This paper presents a robust control framework with meta-heuristic intelligence to optimize the energy performance of air handling units (AHUs) and to maximize the thermal comfort of occupants by judiciously selecting the temperature set points of two controllers (i.e., the H∞ controller and the boiler controller). The selection of these set points...

The increasing penetration of electric vehicles (EVs) in current and future transport fleets imposes significant loading on the existing power grids. Moreover, dc is experiencing renewed interest with rapid growth in electronic loads, the move towards renewable energy sources (RES) and distributed generation, and advances in power electronics techn...

This paper proposes a new consensus based load frequency controller (LFC) using distributed multi-battery energy storage system (MBESS). The proposed control strategy effectively utilizes the ability of the battery storage devices to provide/absorb active power during the period of power deficit/excess. The controller uses the consensus based appro...

Due to the capacitive discharging effect after the fault inception, the dc line current increases dramatically in the dc power system which is interfaced with the ac system through the voltage source converters (VSCs). Therefore, the fast response of the fault detection methods is important to interrupt the fault line with short delay. In recent ye...

A Multi-Objective Optimization (MOO) framework is proposed in this study, for optimization of the overall performance of forced extraction systems used in the kitchen environment. The target of the proposed framework is to achieve a balance (trade-off) among three conflicting objectives: minimization of discomfort, minimization of energy consumed b...

Hnybrid energy storage system (HESS) in microgrids is used to achieve the power balance between the load and generation sides. This paper proposed an event-triggered deadbeat control for HESS to regulate the the bus voltage of microgrids efficiently. The charging and discharging behaviours of HESS are controlled by the deadbeat-based controller, an...

This article presents a new method for estimating the fault location in a voltage-source-converter-interfaced dc system. The proposed dc fault location estimation method evaluates the distance from the fault point to the dc line terminal by estimating the line inductance; hence, it is designated as $L$ location. Since the fault impedance usually...

The present study proposes an alternative approach following command-filtered integral backstepping principle to control the rotor side converter (RSC) of a doubly-fed induction generator (DFIG) based wind energy conversion system (WECS). This controller provides better benefit compared to the classical backstepping controller; since the errors int...

In islanding microgrids, supercapacitors (SCs) are used to compensate the transient power fluctuation caused by sudden variations of load demand and generation power to keep the output voltage stable and reduce the stress in batteries. However, SC current in dynamic response leads to transient power loss on power electronic converters, and it would...

The present study proposes a new consensus control based multi energy storage system for DC microgrid. The proposed design achieves the consensus in finite time by sharing, both the local information of State of Charge (SoC) and battery power with the neighbours. The consensus based control equalises the SoC of multiple energy storage, irrespective...

This paper proposes a hybrid control method based on model predictive control (MPC) and iterative learning control (ILC) for the hybrid energy storage system (HESS) in the application of islanded microgrid with photovoltaic (PV) generation. The hybrid method helps to deal with the sudden change in generation and load power demands. MPC aims to regu...

With the rapid discharge of the dc-link capacitors during the fault occurrence, the dc line current grows rapidly in the dc grid, which interfaces the ac sources through the voltage source converter. Therefore, it is essential to develop a dc fault detection method, which can detect the dc fault with fast response speed and high reliability. In thi...

The rapid discharge of the dc-link capacitors during the short-circuit fault would cause the transient current with fast propagation speed in the VSC based dc system. It is necessary to limit the dc fault current and lower the requirement of fault detection speed. However, the traditional fault current limitation method with directly installed indu...

An adaptive neuro-fuzzy inference system (ANFIS) controller is developed and presented in this study to control hybrid energy storage system (HESS) which combines the battery and super-capacitor (SC). The battery compensates the energy requirement for a longer duration while the SC limits the stress on battery caused by the power fluctuations durin...

Maximum power point tracking (MPPT) is used to utilize intermittent solar power fully in the photovoltaic (PV) systems. Tracking the MPP fast and accurately with changes in the solar irradiance and the temperature is the goal of MPPT techniques. In this paper, a hybrid MPPT method based on iterative learning control (ILC) and perturb \& observe (P&...

In microgrids, hybrid energy storage system (HESS), which consists of batteries and supercapacitors (SC), is used to maintain the power balance between the intermittent renewable energy source (RES) and the changing load demands. A sudden large change in the RES generation or the load demand might result in long rise/fall-time and large over/unders...

Due to the rapid discharging of the dc-link capacitors, the short-circuit fault normally results in a fast-growing transient current in the voltage source converter (VSC) based dc power system. Therefore, a fast and sensitive fault detection method is required. In this paper, the feasibility of Hilbert-Huang transform (HHT) for fault detection in V...

The present study proposes a novel methodology based on a meta-heuristic algorithm to accurately estimate the thermal parameters of a building. These parameters are often most difficult to be quantified in practice as these are strictly determined by the characteristics of the materials used in building construction, which vary significantly from o...

The maximum current carrying capacity (ampac-ity) of power cables depends on the heat transfer-ability of its surrounding medium. Submarine power cable ampacity is calculated conventionally following the international standards defined for underground cables. In reality, the thermal behavior of submarine environments differs significantly from its...

The present study proposes an alternate approach following command-filtered backstepping principle to control the terminal voltage and stabilise the speed of a diesel generator through the excitation system. This controller eliminates the errors introduced due to differentiation of input signal and is therefore better compared to the conventional b...

Several frequency-domain based fault detection methods were developed in the high voltage (HVDC) system in recent years. In this paper, a modified empirical mode decomposition (EMD) designated as median mode decomposition (MMD) is introduced, and a new fault detection method is developed based on that. Compared with the traditional EMD, MMD is able...

This paper presents a solar-PV (photo-voltaic) system with wireless power transfer (WPT) and battery storage backup in various state changes throughout the day. A 378W PV module is connected with high-frequency converters at 20 kHz switching frequency and an LCL compensation network for the wireless power transfer across the primary and the pickup...

This paper investigates some issues associated with the power sharing in the Hybrid Energy Storage System (HESS) in the Multi Micro-Grid System (MMGS) to meet the load demands. To address this problem in isolated microgrids, which often arises in emergency situations, the present study proposes an efficient energy management system (EMS) which oper...

In this research paper, the Multi Agent System (MAS) is introduced to Multi Micro-Grid (MMG) mesh system with the consensus control to share the power between arbitrary inverters to meet the load demand. Each microgrid consists with the Hybrid Energy Storage (HESS) which include the battery and Supercapacitor (SC) to supply/absorb the energy accord...

Although the capability of digital microprocessors has been developed rapidly, the heavy computation burden is a challenge for the model predictive control on the applications of power electronics. This paper presents a zero iteration model predictive control (MPC) for a hybrid energy storage system (HESS) with dual batteries. A PI controller is us...

The rapid rising rate of dc line current after the dc fault inception in the high voltage dc (HVDC) system proposes a high requirement on the response speed of dc fault detection methods. In this paper, a new detection method based on empirical mode decomposition (EMD) is proposed. Unlike traditional parameters including time and frequency, EMD tri...

DC fault current breaking devices are important components for enabling robust protection of the dc system. This chapter will present the ongoing developments regarding the dc fault isolation devices. There are two major trends in dc fault isolation, namely based on, dc circuit breaker (DCCB) and converter-based solution. Firstly, the DCCB will be...

This chapter introduces the devices and components, which are the building blocks for dc grid. These include ‘Thyristor’, which is the building block for the line commutated converters (LCC) and Insulated Gate Bipolar Transistors (IGBTs), which is the building block for voltage source converters (VSC). Other emerging converter topologies are introd...

This chapter provides the introduction to dc grid. A historical perspective of the dc grid is provided, followed by major installations of the high voltage High Voltage Direct Current (HVDC) (HVDC) transmission systems. Comparison of ac and dc systems are given in terms of operation, cost. Various applications of dc technologies, for example High V...

This chapter introduces protection system design for HVDC system and compact dc distribution applications. In the former case, three fault clearance strategies are investigated and compared based on how fast the system recover from fault. As for latter, we are interested to determine the criteria for selecting the protection methods.

This chapter describes the operation of directional protection and communication assisted unit-protection strategies for dc power systems. The directional analysis of the fault currents has been covered in detail and various combinations of directional protection with comparative studies have been presented. Various communication assisted protectio...

This chapters covers the modeling and control of the ac/dc generation systems which would be implemented in the dc grids. The current and voltage source based ac/dc conversion systems with fixed frequency ac input from the stiff ac grid have been considered for HVDC applications. In addition to the HVDC systems, generation systems for marine and ae...

This chapter introduces the frequency-domain based transient analysis of the dc fault currents. Short-Time Fourier Transform (STFT) based fault analysis has been proposed as a frequency domain method for transient state detection in dc networks. This chapter describes in detail the operation of STFT based transient detection with the support of ana...

This book offers a comprehensive reference guide to the important topics of fault analysis and protection system design for DC grids, at various voltage levels and for a range of applications. It bridges a much-needed research gap to enable wide-scale implementation of energy-efficient DC grids. Following an introduction, DC grid architecture is pr...

A comprehensive analysis of wavelet-based method detecting and locating fault in HVDC system is detailed in this chapter. We study how wavelet transform can serve as a protection tool to decide right tripping signal. Detailed coefficient is one of the parameters we use to determine the fault occurrence. Using the analytical fault signal, we illustr...

In this chapter, we will look into the different approach of detecting the dc fault—time-domain methods. There are three different methods to be discussed: overcurrent, rate of change and capacitive discharge. The operation of each method is explained in detail. We obtain the fault signal from the simulation model and apply these methods to evaluat...

This chapter introduces the various non-unit protection strategies for dc grid applications. The requirements of the protection coordination strategies are derived and the procedure of implementing the non-unit protection methods is determined by comparison with the existing protocols available for the ac power systems. The parameters and fault det...

Understanding of dc fault characteristics is very important for designing robust protection system. This chapters presents the analytical expressions for the different types of dc faults, namely pole-to-pole (PP) and pole-to-ground (PG). Firstly, fault current calculation for current source converter (CSC)-based dc system is presented. This is foll...

Thus far, this book approaches performance validation mainly based on simulation-based fault signal. It is practically infeasible to create the short-circuit in real VSC-HVDC system while it is in operation. To validate the fault detection methods using real fault signal, this chapter lays out the steps to create the VSC-based dc test system in lab...

DC power networks are gaining popularity owing to better efficiency, easier integration of renewable energy sources as compared to the AC grids. Owing to such advantages, DC grids are used in the high-voltage power transmission systems (HVDC), as well as being considered for microgrids, more-electric aircraft, shipboard power systems, etc. in the m...

The short circuit fault in the VSC based dc power system typically generates rapidly rising transient current which may have serious repercussions on dc grid operation and health of the integrated power electronic devices. Thus, the dc grid requires a high speed and robust fault detection for reliable system operation. With this regard, this paper...

Energy Storage System plays a vital role in assisting Microgrids to control fluctuating load demand with intermittent power supply. As well as enabling power quality to monitored and controlled, this paper introduces a power storage device, Vanadium oxide flow battery which would facilitate the expansion and allow flexibility with the Microgrid net...

Utilisation of wind energy is related closely with power intermittency issues. For instance, in East Nusa Tenggara, there is a demand-generation mismatch as the load demand is high in the evening and low at noon whereas the wind speed tends to reach its peak at noon. A hybrid storage system is proposed to handle the mismatch by either supplying the...

This paper investigates the effect of integration of solar PV generation with wireless power transfer (WPT) on DC loads with varying PV input parameters. The power converter of the system is designed to operate at around 85 kHz, and two operating conditions of solar irradiance are considered. The first case is an ideal solar PV array with standard...

Large scale grid integration of electric vehicles (EVs) is greatly dependent on electricity price, renewable energy and energy storage system (ESS). In this paper, EVs are charged and discharged according to the requirement of the user with an effective method of charge flow analysis from energy management system. It comprises of controlled operati...

Fault detection in HVDC system is of great importance for reliable operation. In this paper, Electromagnetic Time Reversal (EMTR) technique-based fault detection and localization are proposed. As fault generated transient signal travels along the transmission line, EMTR can help to detect the fault. A HVDC system is simulated in the PSCAD software....

The present study applies reinforcement learning strategy for controller design to improve the low voltage ride through (LVRT) capability of a hybrid power system through convertible static compensator (CSC). The study considers different configurations of CSC such as static synchronous series compensator (SSSC), one static synchronous compensator...

This paper presents a new consensus-based control method for hybrid energy storage system (HESS) with a cascaded multiport converter in the DC microgrid. The cascaded multiport converter has two stages, where the first stage is for the supercapacitor and the second stage is for the batteries. The two-stage structure can reduce the component rating...

Cyber-Physical Systems (CPSs) are implemented in many industrial and embedded control applications. Where these systems are safety-critical, correct and safe behaviour is of paramount importance. Malicious attacks on such CPSs can have far-reaching repercussions. For instance, if elements of a power grid behave erratically, physical damage and loss...

A new three-level bidirectional DC-DC converter configuration for the battery and supercapacitor (SC) energy storage systems in DC microgrids is presented in this paper. The PI-based control method is implemented to operate the proposed converter with hybrid energy storage system. Furthermore, joint control is utilized to obtain rapid DC-link volta...

In PV microgrids, batteries are used to balance the power between the generation and loads side. In this paper, a Dual Hybrid Energy Storage System (DHESS) in microgrids is proposed to reduce the batteries life loss. the duel HESS can work3 on two modes, one is responsible for charging, and another for discharging. The working mode changing is deci...

A significant portion (ca. 40%) of the world's total energy is utilized in buildings. Cooling of large buildings worldwide is done by centrifugal chiller systems, where the compressors, pumps, fans are driven by AC motors. These motors are energy hungry parts of the chiller. All-variable speed chillers, taking into account load variations, reduced...

The residential sector forms a substantial energy consumer, therefore, it is the focus of efforts to reduce energy consumption. To this end, a good understanding of customer load profiling for both the electricity and gas is fundamental to improve the energy utilization efficiency. Unfortunately, the hourly based energy load profiles are not direct...

In recent years, building energy management has been a major research concern; as building end-uses comprise around 30-40% of energy consumption worldwide. Among these end-uses, Heating, Ventilation and Air Conditioning (HVAC) systems have a share of 50%; especially at commercial level. The present study investigates the performance and impact of t...

The increasing integration of Electric Vehicle (EV) poses unique challenges for voltage and frequency regulation in electric distribution grids. EVs are at present the most reliable substitutes for standard fossil fuel-based cars. The mobility and variability due to EV loads exacerbates the problem of voltage regulation in distribution grids that a...

DC marine vessels with medium voltage compact dc power systems are dominated by a significant amount of active loads and a finite number of generation sources. In such scenarios, the network configuration of the dc power system is expected to get dynamically altered to fulfil the required generation and load demands for the desired marine mission....

Growing emphasis on the disturbance-free electrical power distribution demands for economical and efficient smart estimation techniques in the automation architectures of the future medium voltage (MV)/ low voltage (LV) distribution networks. Unlike high-end protective relays which are typically used in the high voltage transmission systems, low-en...

This paper presents a bidirectional single-inductor multiple-port (BSIMP) converter for integrating hybrid energy storage system (HESS) into DC microgrids, where the HESS is the combination of different types of energy storages (ESs). A control method based on model predictive control (MPC) is proposed to regulate the BSIMP converter for the HESS....

DC-coupled microgrids are simple as they do not require any synchronization when integrating different distributed energy generations. However, the control and energy management strategy between the renewable energy sources and the energy storages under different operating modes is a challenging task. In this paper, a new energy management scheme i...

Widespread adoption of electric vehicles (EVs)would significantly increase the overall electrical load demandin power distribution networks. Hence, there is a need for comprehensive planning of charging infrastructure in order to prevent power failures or scenarios where there is a considerable demand-supply mismatch. Accurately predicting the real...

In this study, a new dynamic evolution control (DEC) based power sharing method is proposed for hybrid energy storage system (HESS) with photovoltaic in the isolated DC grid application. The proposed control approach solves the current controller conflict problem in HESS and provides faster DC link voltage restoration. A DEC method is implemented t...

Islanding phenomenon is often undesirable for microgrids because it may interrupt power services, and cause damage to the equipment. At times, islanding is also required to isolate any potential problem. Anti-islanding methods can detect the islanding, causing the distributed generators (DGs) to stop providing power to the loads in microgrids, the...

The maximum current carrying capacity of a power cable (Ampacity) is determined by the thermal characteristics of the cable components and surrounding medium in which they are buried. Power cable ampacity calculations are based on typical standard tables defined with predetermined parameters. In realtime, the environment of installation plays signi...

In this paper, a control strategy is proposed for renewable-interfaced hybrid energy storage system (HESS) under grid connected/islanding conditions. A second harmonic based phased locked loop (PLL) is employed for effective syn-chronization/resynchronization of the microgrid system under contingency conditions. The operation and management of the...

This paper presents a simple and effective deadbeat-based method for hybrid energy storage systems (HESSs), including batteries and supercapacitors, in DC microgrids. Inheriting from the nature of deadbeat control strategies, the proposed method can generate the optimal duty ratio in one control cycle, so that it can respond faster to the disturban...