Mehdi Savaghebi

• PhD
• Professor (Associate) at Technical University of Denmark

In this paper a current control strategy is proposed for grid-following inverters that are connected to the grid through LCL filters. A lead compensation is utilized in series with the proportional gain of the current controller so that high bandwidth is achieved. Furthermore, capacitor current feedback active damping is used to mitigate the effect...

As inverter‐based resources like wind turbines increase, grid inertia and stability decrease. Optimal placement and control of energy storage systems can stablise low‐inertia grids. This paper investigates how optimal battery energy storage systems (BESS) enhance stability in low‐inertia grids after sudden generation loss. The sitting, sizing and c...

This paper proposes a control strategy for grid-forming converters based on a cascade control scheme with current and voltage controllers and an outer loop to control the injected active and reactive power. The analysis demonstrates the increased disturbance rejection capability of the current controller, and the improved loop gain in the low-frequ...

This paper proposes a control strategy for grid-forming converter based on a cascaded control scheme with current and voltage controllers. The theoretical analysis demonstrates the possibility of obtaining almost zero steady-state error for the current loop utilizing only a proportional controller with a magnitude and lead compensation functions to...

Integration of microgrids may introduce significant power quality challenges to the power distribution networks that may necessitate additional enforcement such as installing new Power Quality Improvement Devices (PQID), which is costly and not always possible option. This paper proposes a control approach that enables the existing power electronic...

Faults in a DC aircraft power system typically lead to serious equipment damage, which severely threatens the safety of the whole aircraft system. A fast and accurate real-time fault detection scheme is necessary for aircraft power systems to provide high reliability in the system. In this paper, a new fault detection device (FDD) is proposed based...

It is well-known that the accurate measurement of input voltage and current, as the feedforward and feedback terms, plays a crucial role in the nonlinear controller design for power factor compensation of an AC-DC boost converter. This paper addresses the problem of the simultaneous estimation of the input voltage and current from the output voltag...

In this study, distributed event‐and self‐triggered (ST) control methods are proposed for accurate load sharing and voltage control in islanded AC microgrids with resistive line impedances. The proposed control framework is comprised of a two‐level control structure. At the primary level, the V‐I droop control method is adopted. In this method, the...

Due to the proliferation of critical nonlinear loads in the islanded AC microgrids, the power quality improvement at the sensitive load bus (SLB) is a challenging task. To deal with this issue, a distributed event-triggered control strategy for the voltage harmonic compensation is proposed in this paper. By applying the proposed strategy, the distr...

In this paper, transient current and voltage responses, caused by low and high impedance faults in a power system with distributed generation (DG) systems, are investigated. The proposed approach utilizes a novel transient index (TI) based on the voltage during fault at the point of common coupling. The proposed technique uses voltage signals at DG...

Many distribution systems have several branches with only one protection system at the upstream system. This characteristic degrades the performance of traditional fault location schemes. In this paper, a localized fault location method based on the transient behavior of fault currents by using local data is proposed. The proposed scheme uses only...

Accurate locating of the faulty section is desired in DC microgrid due to the presence of power electronic converters and low-impedance cables. Some of the existing schemes consider power sources at only one end of the line; thus, assume that the fault current is injected from only one end of the line. This assumption is not true in the case of mes...

DC faults can create serious damages if not detected and isolated in a short time. This paper proposes a fault detection technique for DC faults to enhance the protection of DC microgrid clusters. To detect such faults accurately and quickly, a DC fault detection scheme using empirical mode decomposition (EMD) and Hilbert transform (HT) is proposed...

Hybrid standalone DC Microgrid, which consist of photovoltaic (PV) generation, energy storage systems, and power electronic converters, provide high efficiency and clean power supply to loads. These hybrid DC Microgrids can be implemented in many applications, where there are difficulties in connecting to the main grid. In this paper, a directional...

High penetration of rooftop PV systems in distribution feeders can give rise to overvoltage during peak generation hours. A well-known solution for this problem is Volt-VAR control method, in which PV inverters mitigate the overvoltage by reactive power absorption. The conventional Volt-VAR scheme calculates the reactive power reference based on a...

Due to the mismatched line resistance in the modular on-line Uninterruptible Power Supply (UPS) systems, accurate active power and harmonic power sharing is an arduous work. To tackle this issue, this paper proposes a distributed dynamic event-triggered control for the power sharing to accurately compensate the effect of mismatch among the line res...

With the increasing number of DC microgrids, DC microgrid clusters are emerging as a cost-effective solution. Therefore, due to the possible long distances between DC microgrids, once a fault occurs and is cleared, it should be located. Especially, locating high impedance faults (HIFs) is challenging. With communication-free fault locating methods,...

A new DC fault current limiter (FCL)-based circuit breaker (CB) for DC microgrid (MG) clusters is proposed in this paper. The analytical expressions of the DC fault current of a bidirec-tional interlink DC/DC converter in the interconnection line of two nearby DC MGs are analyzed in detail. Meanwhile, a DC fault clearing solution (based on using a...

Single phase induction motors (SPIM) are widely used in residential and commercial applications. Enhancement of efficiency of SPIMs can lead to huge energy savings. This paper presents a novel mechanical sensorless control method for SPIM drives. In this method, a machine learning algorithm is used to estimate the slip based on the ratio of main an...

In recent years, shipboard microgrids (MGs) have become more flexible, efficient, and reliable. The next generations of future shipboards are required to be equipped with more focuses on energy storage systems to provide all-electric shipboards. Therefore, the shipboards must be very reliable to ensure the operation of all parts of the system. A re...

This paper introduces an optimal voltage control (OVC) framework for islanded microgrids (MGs) as a unified hierarchical control scheme, started from bus voltage set‐points optimization at tertiary level, then effectively followed by secondary control, which controls the distributed energy resources via their primary level controllers. The distribu...

Several technical, computational, and economic barriers have caused curtailing a share of renewable-based power generation, especially in systems with higher penetration levels. The Mobile Battery Energy Storage (MBES) can cope with this problem considering the spatial and temporal distribution of the curtailed energy. Accordingly, a new operation...

Nowadays, the role of cyber-physical systems (CPSs) is of paramount importance in power system security since they are more vulnerable to different cyber-attacks. Detection of cyber-attacks on a direct current microgrid (DC-MG) has become a pivotal issue due to the increasing use of them in various electrical engineering applications, from renewabl...

The high-resolution data on electricity consumption, recorded by smart meters at customers’ premises, are valuable sources of operational information and consumption patterns. In addition, customers’ characterization plays an undeniable role in the implementation of demand response (DR) programs, as any changes in the consumption patterns could aff...

The number of harmonic-producing sources is rapidly growing in the power grid due to the increased penetration of power electronic-interfaced resources (such as wind turbines, photovoltaic systems, and energy storage units) and proliferation of nonlinear loads. Many researchers have investigated the effects of non-sinusoidal waveforms on the perfor...

This paper proposes an algorithm for detection and identification of the location of short circuit faults in islanded AC microgrids (MGs) with meshed topology. Considering the low level of fault current and dependency of the current angle on the control strategies, the legacy overcurrent protection schemes are not effective in in islanded MGs. To o...

An accurate definition of a system model significantly affects the performance of model-based control strategies, for example, model predictive control (MPC). In this paper, a model-free predictive control strategy is presented to mitigate all ramifications of the model’s uncertainties and parameter mismatch between the plant and controller for the...

Abstract A control approach for three‐phase four‐leg LC‐filtered voltage source inverters (VSIs) is proposed for an uninterruptible power supply (UPS) application. A filter inductor in the fourth (neutral) leg of the VSI is considered to enhance the output voltage quality when feeding different types of loads in such a system. The proposed approach...

An electric spring (ES) with series connection to non-critical loads (NCLs) is mainly known as a smart load (SL) technology that can compensate undervoltages and overvoltages. In this paper, an improved control method is presented for the electric spring to regulate the effective value of the critical load (CL) voltage to the nominal value and to c...

The increasing penetration of dc distributed energy resources (DERs) and dc loads has motivated the utilization of dc microgrids (MGs). In this paper, a new two-level control scheme is proposed for accurate power sharing and appropriate voltage regulation in dc MGs during islanded operation mode. In the primary control level, a P-V̇ droop method is...

Preservation of wind turbines (WTs) grid-connectivity during grid faults and grid-code (GC) compliant reactive power injection at PCC during voltage drops is an imperative task to perform in modern WTs. This is known as the low-voltage ridethrough (LVRT) capability of WTs, emerging as an integral GC requirement. Despite current provision of LVRT in...

The high share of electric vehicles (EVs) in the transportation sector is one of the main pillars of sustainable development. Availability of a suitable charging infrastructure and an affordable electricity cost for battery charging are the main factors affecting the increased adoption of EVs. The installation location of fixed charging stations (F...

In recent years, DC distribution system has been considered as an efficient solution in Shipboard Power Systems (SPS) to improve the system performance in several aspects such as overall efficiency, reliability, security and size. However, rising fuel price, its unpredictability, growing global demand for energy and the necessity to decrease enviro...

This paper presents a GPS-based decentralized control strategy for hybrid AC/DC microgrids. The proposed method uses V-I droop characteristics for the distributed energy resources (DERs) in each of AC and DC subgrids. In particular, the output voltage of each DER is adjusted as a piecewise linear function of the per-unit output current. In addition...

Distribution network protection is becoming more sophisticated in the wake of ever-changing landscape of power systems driven by the vast renewable energy integration mostly sited behind the meters, growing uncertainty and volatility subsequent to smart demand response and renewable energy integrations, further fusion of power electronics-interface...

The synchronous rotating inertia is the key parameter of power system stability. Increasing the penetration of nonsynchronous generators, e.g., wind turbine, photovoltaics, and energy storage system, in the power grids leads to some stability challenges due to the lack of rotating mass and kinetic inertia in the system. In this chapter, the effect...

In this paper, a new identification tool for dynamic voltage restorer (DVR) is proposed to achieve flexible active and reactive power dispatch during voltage sags. The presented tool entirely relies on the theoretical analysis of the elliptical transformation, and identification marks are determined for different power injections by using one set o...

In this paper, a new modified structure of a DC/DC T-source converter is proposed. Since the proposed converter provides high voltage gain, it is suitable for photovoltaic integration into uninterruptible power supply (UPS) systems. The proposed structure employs partial power processing technique to increase the output voltage as well as efficienc...

This paper aims to present a new structure of the parallel Z-source inverters (ZSIs) for dual-input single-phase grid-connected photovoltaic (PV) systems. The ZSI is a single-stage buck-boost converter that uses an inductor-capacitor network between the inverter bridge and the PV string and follows the maximum power point by applying the shoot-thro...

In the process of determination of breakpoints for overcurrent relays (OCR), different sets with equal number of OCRs can be selected as minimum breakpoint set (MBPS). Therefore, determination of the most appropriate MBPS is an issue which must be considered. This paper proposes a prioritization between different MBPSs based on the sum of operating...

In this paper, a current sharing method based on the circular chain control (3C) method is proposed for controlling parallel inverters of unequal ratings in uninterruptible power supply (UPS) applications. Due to its circular structure, 3C is one of the most convenient methods which can be used in UPS as well as microgrid systems. However, the conv...

In this study, a coordinated control scheme is proposed for sharing harmonics compensation effort among voltage and current controlled mode (VCM and CCM) inverters in islanded microgrids. In this method, the voltage harmonics compensation of sensitive bus (SB) is achieved by using secondary control as well as virtual impedance and admittance loops...

In this paper, an efficient energy management system (EMS) is proposed for optimal operation of multiple electrically coupled microgrids (MGs). A new bi-level EMS is employed as an enhanced technique to coordinate vehicle-to-grid (V2G) operation of electric vehicles (EVs) with a stochastic framework in a multi-microgrid system. Hierarchical EMS hel...

This article presents a reduced-order generalized proportional-integral observer based resonant super-twisting sliding mode controller (RST-SMC) for the three-phase ac–dc converters. On the contrary to utilizing the proportional-integral controller in regulating the dc-link voltage, which may cause large undershoot/overshoot under the disturbance,...

In the most common hierarchical control structure for microgrids, the secondary control layer relies on communication technologies for receiving feedback data and sending control commands. The imperfections of communication such as the delays can cause oscillations during the voltage and frequency restoration which degrade the power quality. This w...

With the changing nature of electrical systems from conventional electrical systems to smart electrical systems, several aspects should be considered and adapted with the new conditions. One of the most important characteristics of electrical systems, is the power quality concept. There has been much effort on designing devices to improve power qua...

Microgrid, which is one of the main foundations of the future grid, inherits many properties of the smart grid such as, self-healing capability, real-time monitoring, advanced two-way communication systems, low voltage ride through capability of distributed generator (DG) units, and high penetration of DGs. These substantial changes in properties a...

In recent years, distribution networks have been increasingly affected by the random nature of harmonic sources introduced by nonlinear load and renewable energy sources (RES) such as photovoltaic (PV) systems. This paper presents an approach based on Genetic Algorithm (GA) and Monte-Carlo Simulation (MCS) for the optimal planning of single-tuned p...

DC microgrids have attracted significant attention over the last decade in both academia and industry. DC microgrids have demonstrated superiority over AC microgrids with respect to reliability, efficiency, control simplicity, integration of renewable energy sources, and connection of dc loads. Despite these numerous advantages, designing and imple...

This paper proposes a novel method to locate faults in an AC-meshed microgrid. To this end, a set of features is first extracted and selected from the measured signals and fed to a Support Vector Machine (SVM) to detect the occurrence of fault. Then, the Distributed Generator (DG) with the lowest amount of fundamental voltage, which is the closest...

This article aims to determine the most suitable cross-sectional area for a high voltage alternating current (HVAC) submarine cable in the design phase of new projects. A thermal ladder network method (LNM) was used to analyse the thermal behaviour in the centre of the conductor as the hottest spot of the cable. On the basis of the calculated cable...

In this paper, a regeneration protection solution is proposed to address the DC-link overvoltage issue and the unequal power sharing in the parallel Uninterruptible Power Supply (UPS) systems. First, a DC-link Voltage Protection (DCVP) control strategy is proposed to protect the inverter against the excessive DC-link voltage that may trigger the pr...

High power motor loads are widely used in shipboard microgrids (SMGs) consuming about 70% of generated electrical power. Voltage dips, which are usually caused by the starting current of high power motors, are one of the main causes of onboard sensitive electrical equipment dropout. This phenomenon must be considered in design of SMGs to comply wit...

Multifunctional DGs and active power filters have become a mature technology in recent years, so in this paper, an optimized current control method for a multilevel converter is proposed. The control method will overcome harmonic current tracking inefficiency of previous control methods in online harmonic compensation applications in microgrids. Th...

In this paper, offline adaptive control of a microgrid in an islanded operation mode is presented. The proposed control scheme consists of a power controller, voltage controller, and current controller, which are operating in a cascade structure. The power controller is designed based on the droop characteristics while the voltage and current loops...

This paper presents a reduced-order enhanced state observer (RESO)-based control strategy for the PWM DC-DC buck converter. With the proposed RESO control strategy, the output voltage regulation of the DC-DC buck converter is able to achieve robust characteristics against the external disturbance and internal parameter variation even without output...

In this paper, the impact of grid-connected photovoltaic (PV) systems on voltage total harmonic distortion (THDV) in radial distribution systems is investigated. To well present the behavior of PV systems, both amplitude and phase angle of the harmonic current sources are considered in the simulations. Specifically, when the current harmonic phase...

Proper installation of rooftop photovoltaic generation in distribution networks can improve voltage profile, reduce energy losses, and enhance the reliability. But, on the other hand, some problems regarding harmonic distortion, voltage magnitude, reverse power flow, and energy losses can arise when photovoltaic penetration is increased in low volt...

Power quality (PQ) is becoming more and more critical issue in shipboard microgrid systems (SMG). Especially, the impact of voltage unbalance combined with harmonic distortions on the SMG behavior has not been fully investigated. In this paper, simple power quality assessment models and a series of controlled experiments are proposed and carried ou...

This paper presents the power flow modeling of droop-controlled distributed generation units with secondary frequency and voltage restoration control for hierarchically controlled islanded microgrids. These models are incorporated in the conventional Newton-Raphson power flow method as a new bus, without the necessity of a slack bus, and include th...

Fault Current Limiters (FCLs) are one of the main solutions to upcoming challenges in microgrid protection. Regarding the high penetration of distributed generations (DGs) in future power system, designing cheap and effective FCL is a necessity. The present study addresses this issue by proposing an embedded FCL operating based on modifying the sec...

In this paper, the control of an interface inverter for application of a hybrid photovoltaic and battery energy storage system (BESS) is proposed. The control system of the inverter consists of 2 parts including power quality enhancement and active power control. A control approach for battery state of charge and power management is proposed for im...

To enhance the robustness and disturbance rejection ability of an on-line uninterruptible power supply (UPS) system, an Internal Model Control (IMC)-based DC-link voltage regulation method is proposed in this paper. Furthermore, the multi-mode operations of the on-line UPS system are investigated and their corresponding control strategies are propo...

In this paper, the power quality (PQ) improvement of multi-area microgrids (MAMGs) is addressed. To this aim, mitigation of voltage harmonics and unbalance is considered by using distributed generators (DGs) and active power filters (APFs) in a proper way. As a novel approach, the main goal of the proposed method is to pick out redundant APFs and/o...

This paper presents a smart Transactive energy (TE) framework in which home microgrids (H-MGs) can collaborate with each other in a multiple H-MG system by forming coalitions for gaining competitiveness in the market. Profit allocation due to coalition between H-MGs is an important issue for ensuring the optimal use of installed resources in the wh...