Showing papers by "Juan C. Vasquez published in 2019"
TL;DR: A communication-less strategy for the decentralized control of a photovoltaic (PV)/battery-based highly distributed dc microgrid, where each nanogrid can work independently along with provisions of sharing resources with the community.
Abstract: DC microgrids built through a bottom-up approach are becoming popular for swarm electrification due to their scalability and resource-sharing capabilities. However, they typically require sophisticated control techniques involving communication among the distributed resources for stable and coordinated operation. In this work, we present a communication-less strategy for the decentralized control of a photovoltaic (PV)/battery-based highly distributed dc microgrid. The architecture consists of clusters of nanogrids (households), where each nanogrid can work independently along with provisions of sharing resources with the community. An adaptive I–V droop method is used, which relies on local measurements of state of charge and dc bus voltage for the coordinated power sharing among the contributing nanogrids. PV generation capability of individual nanogrids is synchronized with the grid stability conditions through a local controller, which may shift its modes of operation between maximum power point tracking mode and current control mode. The distributed architecture with the proposed decentralized control scheme enables 1) scalability and modularity in the structure, 2) higher distribution efficiency, and 3) communication-less, yet coordinated resource sharing. The efficacy of the proposed control scheme is validated for various possible power-sharing scenarios using simulations on MATLAB/Simulink and hardware-in-the-loop facilities at the Microgrid Laboratory, Aalborg University.
127 citations
TL;DR: The historical development of a standard single- phase FLL, its modeling and tuning aspects, its relationship with adaptive notch filters, its advanced versions for the synchronization purposes under adverse grid conditions, its modification for different industrial applications, its connection with single-phase PLLs, and its discretization aspects are the main parts of this review.
Abstract: Synchronization techniques can be classified into open-loop and closed-loop methods. In power and energy applications, which are the focus here, the latter type is more popular. Phase-locked loops (PLLs) and frequency-locked loops (FLLs) are two broad categories of closed-loop synchronization techniques. The aim of this paper is providing a review of recent advances in designing single-phase FLLs, which can be very useful for both researchers and engineers. The historical development of a standard single-phase FLL, its modeling and tuning aspects, its relationship with adaptive notch filters, its advanced versions for the synchronization purposes under adverse grid conditions, its modification for different industrial applications, its connection with single-phase PLLs, and its discretization aspects are the main parts of this review.
110 citations
TL;DR: A rule-based adaptive protection scheme using machine-learning methodology for microgrids in extensive distribution automation (DA) based on the state recognition in the algorithm, adaptive reconfigurations can be implemented with enhanced decision-making to modify the protective settings and the network topology to ensure the reliability of the intelligent operation.
Abstract: This paper presents a rule-based adaptive protection scheme using machine-learning methodology for microgrids in extensive distribution automation (DA). The uncertain elements in a microgrid are first analysed quantitatively by Pearson correlation coefficients from data mining. Then, a so-called hybrid artificial neural network and support vector machine (ANN-SVM) model is proposed for state recognition in microgrids, which utilises the growing massive data streams in smart grids. Based on the state recognition in the algorithm, adaptive reconfigurations can be implemented with enhanced decision-making to modify the protective settings and the network topology to ensure the reliability of the intelligent operation. The effectiveness of the proposed methods is demonstrated on a microgrid model in Aalborg, Denmark and an IEEE 9 bus model, respectively.
96 citations
TL;DR: This paper proves that filtered capacitor voltage feedforward is a more robust and reliable solution than implementations based on cascade notch filters.
Abstract: The use of LCL filters is a well-accepted solution to attenuate the harmonics created by the pulsewidth modulation. However, inherently LCL filters have a resonance region where the unwanted harmonics are amplified, which can compromise stability. Several techniques have been developed in order to tackle this issue. At first the use of passive damping, by intentionally increasing the resistance of the LCL filter components, is a simple, robust, and straightforward solution; however, it decreases the overall efficiency of the system, and hence in general is unwanted. Alternatively, active damping strategies, where the resonance damping is provided by the current controller, are of major interest. This paper analyzes the robustness of the closed-loop dynamics when different active damping techniques are implemented. The analyzed active damping techniques, which have been selected because of their readiness and simplicity, are: 1) filtered capacitor voltage feedforward and 2) second-order filters in cascade with the main current controller. The impedance/admittance stability formulation is used to model the system, which has been proven to be very convenient for the assessment of robustness. Experimental tests are provided in order to show the accuracy of the analysis and verify the findings. This paper proves that filtered capacitor voltage feedforward is a more robust and reliable solution than implementations based on cascade notch filters.
83 citations
TL;DR: In this article, the possibility of achieving long-range wireless communication between inverters to empower various control schemes is discussed, which can improve the accuracy, speed and robustness of them.
Abstract: In a microgrid, with several distributed generators (DGs), energy storage units and loads, one of the most important considerations is the control of power converters. These converters implement interfaces between the DGs and the microgrid bus. In order to achieve higher functionality, efficiency and reliability, in addition to improving the control algorithms it is beneficial to equip the inverters with “smart” features. One interpretation of “smartness” refers to minimizing the requirement of communication and therefore switching from centralized to decentralized control. At the same time, being equipped with efficient and state of the art communication protocols also indicates “smartness” since the requirement of communication cannot be completely omitted. A “smart inverter” should offer some features such as plug and play, self-awareness, adaptability, autonomy and cooperativeness. These features are introduced and comprehensively explained in this article. One contribution discussed here is the possibility of achieving long-range wireless communication between inverters to empower various control schemes. Although current efforts aim to modify and improve power converters in a way that they can operate communication free, if a suitable and functional communication protocol is available, it will improve the accuracy, speed and robustness of them.
81 citations
TL;DR: Providing a review of recent advances, introducing the concept of inloop filters for designing more advanced FLLs, demonstrating the FLL modeling and tuning in the presence of an inloop filter, analyzing the advantages and disadvantages of using an in loop filter in the Fll structure, and establishing a connection between FLL's and PLLs are the main parts of this research.
Abstract: Contrary to the phase-locked loop (PLL), which has almost reached a mature stage of development in power and energy applications (particularly in three-phase systems), the frequency-locked loop (FLL) is not a mature technique yet. This is probably because of the implementation of FLLs in the stationary reference frame, which makes their modeling, tuning, and performance enhancement more complicated than PLLs. The aim of this paper is conducting a research on three-phase FLLs. Providing a review of recent advances, introducing the concept of inloop filters for designing more advanced FLLs, demonstrating the FLL modeling and tuning in the presence of an inloop filter, analyzing the advantages and disadvantages of using an inloop filter in the FLL structure, and establishing a connection between FLLs and PLLs are the main parts of this research.
77 citations
TL;DR: The design of nonlinear droop in dc power distribution systems is studied with special emphasis on load sharing, voltage regulation, system efficiency, and stability, and a generic polynomial expression is presented to unify different droop equations.
Abstract: Linear droop faces the design tradeoff between voltage regulation and load sharing due to cable resistances and sensing errors. Using a larger droop resistance improves load sharing, but requires a wider droop voltage range. In the nonlinear droop, droop resistance is a function of the converter's output current, and its value increases when the output current increases. As a result, the impacts from sensors and cables are reduced. In this paper, the design of nonlinear droop in dc power distribution systems is studied with special emphasis on load sharing, voltage regulation, system efficiency, and stability. After discussing the piecewise linear and nonlinear droop control, a generic polynomial expression is presented to unify different droop equations. The impact of droop on dc system efficiency is analyzed by evaluating cable and power converter losses. The converter's output impedance using nonlinear droop is modeled to analyze the system stability with constant power loads. The selection and design guidelines of nonlinear droop are summarized, considering both the static performance and interaction with load systems. The analysis is verified in 400-V multi-source dc systems. The nonlinear droop is fully distributed as it only needs local information.
75 citations
TL;DR: Frequency-locked loops based on the linear Kalman filter, complex bandpass filter, and circular limit-cycle oscillator are considered, which have not been well analyzed in the literature, and limited knowledge about their real advantages/disadvantages compared to the SOGI-FLL exists.
Abstract: Frequency-locked loops (FLLs) create a rather large category of closed-loop synchronization techniques, which have received considerable attention in different engineering applications, particularly for synchronization, signal processing, and control purposes. Focusing on single-phase grid applications, designing FLLs is often based on a second-order generalized integrator (SOGI), and the SOGI-FLL is regarded as a standard structure. Using the linear Kalman filter (LKF), complex bandpass filter (CBF), and circular limit-cycle oscillator (CLO) are some alternative approaches. FLLs based on these filters/elements, which are briefly referred to as the LKF-FLL, $1\phi$ -CBF-FLL, and CLO-FLL, have not been well analyzed in the literature, and limited knowledge about their real advantages/disadvantages compared to the SOGI-FLL exists. Covering this gap is the objective of this paper.
39 citations
11 Jul 2019
TL;DR: A real hybrid-electric-ferry is taken as a case-study to integrate battery units to a dc bus for supplying the propulsion motors and a coordinated power flow control between DGs and BUs is presented.
Abstract: DC and dc/ac hybrid distribution and energy storage for shipboard power systems (SPSs) are becoming a major trend due to efficiency improvement, space saving, and maneuverability enhancement. This paper has taken a real hybrid-electric-ferry as a case-study to integrate battery units (BUs) to a dc bus for supplying the propulsion motors. Furthermore, two diesel generators (DGs) are connected to the ac bus to supply the hotel loads, and a bidirectional dc/ac converter with an LCL filter is responsible for the power flow between ac and dc buses. This power topology is flexible for this ferry operation in pure electrics, extended range, and shore power modes. The DC bus voltage is stabilized and its voltage ripple is limited by BUs’ interleaved three-phase bidirectional dc/dc converter with its controller considering the operation states of propulsion motors. A coordinated power flow control between DGs and BUs is presented that the system frequency is fixed for the optimal operational efficiency of the diesel engines and a ${Q}$ – ${V}$ droop control plus a virtual impedance loop is used to make different ac bus voltages. Synchronization with shore power and the dc/ac converter is facilitated by ${P}$ – ${f}$ droop control. Simulation results are presented to validate the proposed control approach in different missions.
37 citations
TL;DR: Using the proposed control method, the amplitude of the output current can be limited to a constant value, which can be set by the customer to avoid the destruction of the power converter, and to obtain a faster recovery performance as well.
Abstract: In this paper, an overload and short-circuit protection method is proposed for voltage source inverter-based uninterruptible power supply (UPS) system. In order to achieve high reliability and availability of the UPS, short circuit and overload protection scheme are necessary. When overload or short circuit happens, using the proposed control method, the amplitude of the output current can be limited to a constant value, which can be set by the customer to avoid the destruction of the power converter, and to obtain a faster recovery performance as well. The detailed principle of the proposed protection method is discussed in this paper. It mainly contains three parts in the control diagram for current limit, first is the anti-windup in the voltage and current controllers, then the feedforward of the capacitor voltage to the current control loop, the last is the fast reset of the resonant part of the current controller when overcurrent happens. The procedure of developing the control method is also presented in the paper. Experimental results on a commercial UPS system are presented to verify the effectiveness of the control method.
36 citations
TL;DR: By using the proposed method, the energy can be effectively harvested from the crane into the flywheel energy storage system during its operation, which significantly enhances the harbor power system efficiency as well as supply quality.
Abstract: Seaports are specifically designed for trading purposes. They are equipped with facilities for handling industrial and commercial goods as well as raw materials stored in containers. These facilities are often based on diesel cranes, which are noisy and produce air pollution. A possible solution to address this problem is replacing the diesel-power cranes with the electric ones. This idea, however, demands a high power connection to the grid in the seaport. This paper presents a cost-effective and environmentally friendly solution based on an electrical flywheel system to reduce electricity consumption from the electrical power network while improving system efficiency by using already existing technologies. Besides, this study presents a new method for controlling electrical drives using flywheel energy storage systems in harbor crane applications by exploiting the energy harvested from the cranes. The system model, including the electrical grid, cranes, power electronic drives, and flywheels as energy storages, is presented and an effective control methodology is developed. Simulation results of a practical crane system are presented and discussed. Practical lab-scale setup is also built and tested. The results have shown that by using the proposed method, the energy can be effectively harvested from the crane into the flywheel energy storage system during its operation, which significantly enhances the harbor power system efficiency as well as supply quality.
TL;DR: Simulations using PLECS and experiments on a real commercial modular UPS are developed to verify the effectiveness of the proposed control methodology, showing a superior power sharing performance is obtained when using the proposed method.
Abstract: In this paper, an average active power sharing control strategy based on the distributed concept for the parallel operation of voltage source inverters is proposed to be applied to the modular uninterruptible power supply (UPS) systems The presented method is named distributed adaptive virtual impedance control (DAVIC), which is coordinated with the droop control method Low bandwidth CAN-based communication is used for the requirement of data sharing of the proposed method in the real modular UPS system Unlike the conventional virtual impedance control techniques, the virtual impedance of a converter module is adjusted automatically by using global information when DAVIC is applied, further to tune the output impedance of the power modules The adaptive virtual impedance is calculated by using the difference between the active power of a local module and the average active power of all the modules in a modular UPS The DAVIC overcomes the drawback of the conventional virtual impedance control since an accurate value of the real output impedances of different converter modules is not required Simulations using PLECS and experiments on a real commercial modular UPS are developed to verify the effectiveness of the proposed control methodology These results shown a superior power sharing performance is obtained when using the proposed method
TL;DR: A better dynamic power sharing performance along with an inherent anti-windup capability of the integral controller is achieved by using the proposed novel DAISC approach.
Abstract: This paper presents a distributed average integral secondary control (DAISC) method for modular uninterruptible power supply (UPS) systems-based microgrids. For each UPS unit, the local primary control level encompasses droop control and virtual impedance loops, which is commonly used in parallel inverter systems. In order to provide a fast voltage recovery performance, along with excellent power sharing capability among the parallel UPS modules, a distributed secondary control method based on controller area network (CAN) communication is proposed. In a sharp contrast to the existing distributed secondary control strategies, in which the output voltage and frequency of the modules are not shared through the CAN bus, in the proposed apporach, the inverter modules of the modular UPS share the integral output value of the secondary controller. By using the proposed novel DAISC approach, a better dynamic power sharing performance along with an inherent anti-windup capability of the integral controller is achieved. Simulation results using PLECS and experiments from a modular UPS platform have been developed to verify the feasibility and effectiveness of the proposed distributed secondary control. The results show that good performance of voltage recovery and power sharing of the proposed control method is obtained.
TL;DR: In this paper, a fast yet effective open-loop synchronization (OLS) technique based on Cascaded Delayed Signal Cancellation (CDSC) is presented.
Abstract: The shunt active power filters (SAPFs) are broadly utilized to improve the power quality (PQ) issues of electric power systems. A crucial issue in implementing these filters is the accurate estimation of the grid voltage phase/frequency. Indeed, the dynamic behavior and the performance of the SAPF strongly rely on this point. To deal with this challenge, a fast yet effective open-loop synchronization (OLS) technique based on Cascaded Delayed Signal Cancellation (CDSC) is presented in this paper. The proposed technique can reject the odd-order harmonics, the DC offset of the grid voltage, and its dynamic response during transients take an only half cycle of the fundamental frequency. To adapt the proposed OLS technique to the frequency changes, an efficient frequency estimator is also presented. The effectiveness of the proposed OLS technique is demonstrated using simulation and experimental results.
TL;DR: The aim of this paper is to develop advanced DSC-based PLLs for single-phase applications based on adaptive DSC operators and their performances are evaluated using experimental results.
Abstract: In three-phase systems, using the delayed signal cancelation (DSC) operators is one of the most popular approaches for designing advanced phase-locked loops (PLLs), particularly for applications where a high disturbance rejection ability is demanded. In single-phase systems, however, they have not received a considerable attention. The aim of this paper is to develop advanced DSC-based PLLs for single-phase applications. To this end, three PLLs are designed and presented. The first is based on adaptive DSC operators, and the other two are based on nonadaptive operators. The design aspects of these PLLs are discussed in detail, and their performances are evaluated using experimental results.
TL;DR: In this letter, the procedure of deriving the LTP model for single-phase GSTs is first demonstrated and the accuracy of theLTP model in predicting the GST dynamic behavior and stability is evaluated and compared with that of the LTI one.
Abstract: The grid synchronization unit, which is often based on a phase-locked loop (PLL) or a frequency-locked loop (FLL), highly affects the power converter performance and stability, particularly under weak grid conditions. It implies that a careful stability assessment of grid synchronization techniques (GSTs) is of vital importance. This task is most often based on obtaining a linear time-invariant (LTI) model for the GST and applying standard stability tests to it. Another option is modeling and dynamics/stability assessment of GSTs in the linear time-periodic (LTP) framework, which has received a little attention. In this letter, the procedure of deriving the LTP model for single-phase GSTs is first demonstrated. The accuracy of the LTP model in predicting the GST dynamic behavior and stability is then evaluated and compared with that of the LTI one. Two well-known single-phase GSTs, i.e., the second-order generalized integrator-based FLL (SOGI-FLL) and enhanced PLL (EPLL), are considered as the case studies.
TL;DR: A hierarchical controller applied to a microgrid, including wind turbines and battery units, is proposed to provide a coordinated frequency support to a weak grid by adjusting the tie-line active power flow according to the frequency-grid requirements.
Abstract: Dispersed wind power connected to the weak grid may cause the frequency instability. In this paper, a hierarchical controller applied to a microgrid (MG), including wind turbines (WT) and battery units (BU), is proposed to provide a coordinated frequency support to a weak grid by adjusting the tie-line active power flow according to the frequency-grid requirements. The coordination between MG local and central controllers provides the following features. 1) In case of required grid-frequency, the MG tie-line power flow will be controlled to be constant in each dispatching time interval. 2) In case of under-frequency, the coordination between WT virtual inertia and BU controllers will be used to participate in primary frequency regulation (PFR). Then, BU supplies power according to the secondary frequency regulation (SFR) commanded by the main-grid dispatch center. 3) In case of over-frequency, BU absorbs power to reduce the tie-line active power for PFR purposes. After that, the SFR uses pitch control coordinated with the battery charge control. A stability analysis model is established to deal with several transitions among different operation modes and the interaction between the weak grid impedance and the MG output impedance. Simulation results are presented to validate the proposed approach.
TL;DR: Looking at today's energy development, the traditional singlepower generation and transmission phase is gone forever, which requires clean, intelligent, efficient, and reliable power.
Abstract: Looking at today's energy development, the traditional singlepower generation and transmission phase is gone forever. We are now in the Internet of Smart Energy era, which requires clean, intelligent, efficient, and reliable power. With the largescale adoption of renewable sources and Internet of Things technology, the development of the energy Internet has become irreversible. Global newenergy companies are urgently exploring and actively responding to this trend.
TL;DR: In this paper, a frequency sharing approach is presented to smooth the effect of the highly intermittent nature of PV panels integrated with the shipboard microgrids, where a hybrid system based on an ultra-capacitor and a lithium-ion battery is developed such that high power and short term fluctuations are catered by an ultra capacitor, whereas long duration and high energy density fluctuations are cater by the lithium ion battery, in order to cater for the fluctuations caused by weather or variation in sea states, a battery energy storage system (BESS) is utilized in parallel to the
Abstract: In recent times, concerns over fossil fuel consumption and severe environmental pollution have grabbed attention in marine vessels. The fast development in solar technology and the significant reduction in cost over the past decade have allowed the integration of solar technology in marine vessels. However, the highly intermittent nature of photovoltaic (PV) modules might cause instability in shipboard microgrids. Moreover, the penetration is much more in the case of utilizing PV panels on ships due to the continuous movement. This paper, therefore, presents a frequency sharing approach to smooth the effect of the highly intermittent nature of PV panels integrated with the shipboard microgrids. A hybrid system based on an ultra-capacitor and a lithium-ion battery is developed such that high power and short term fluctuations are catered by an ultra-capacitor, whereas long duration and high energy density fluctuations are catered by the lithium-ion battery. Further, in order to cater for the fluctuations caused by weather or variation in sea states, a battery energy storage system (BESS) is utilized in parallel to the dc-link capacitor using a buck-boost converter. Hence, to verify the dynamic behavior of the proposed approach, the model is designed in MATLAB/SIMULINK. The simulation results illustrate that the proposed model helps to smooth the fluctuations and to stabilize the DC bus voltage.
TL;DR: A delay compensator based on lead-lag compensation along with gain regulation block is designed to enhance the system stability against the communication delay and validate the effectiveness of the proposed methods.
Abstract: The secondary control of microgrids (MGs) normally relies on the communication network to exchange information. Communication delay is an inherent characteristic during the signal transmission process, which may deteriorate the system dynamic performance and even destabilize the system. This paper studies the impact of communication delay on the small-signal stability of MGs with distributed secondary frequency and voltage control, and further investigates the corresponding delay compensation method. First, a time-delayed small-signal dynamic model of MGs considering both distributed secondary frequency and voltage controllers is developed. Based on the model, a comprehensive delay-dependent stability analysis is performed to reveal how the amount of communication delay, the topologies of communication networks, and the values of control parameters affect the system stability. Subsequently, a delay compensator based on lead-lag compensation along with gain regulation block is designed to enhance the system stability against the communication delay. Finally, time-domain simulation and experimental results are presented to validate the effectiveness of the proposed methods.
TL;DR: An internal model control-based dc-link voltage regulation method is proposed and capable of achieving the seamless transition in traditional normal mode, photovoltaic-aidednormal mode, enhanced eco-mode (EEM), and burn-in test mode (BTM).
Abstract: To enhance the robustness and disturbance rejection ability of an on-line uninterruptible power supply (UPS) system, an internal model control-based dc-link voltage regulation method is proposed in this paper. Furthermore, the multimode operations of the on-line UPS system are investigated and their corresponding control strategies are proposed. The proposed control strategies are capable of achieving the seamless transition in traditional normal mode, photovoltaic-aided normal mode, enhanced eco-mode (EEM), and burn-in test mode (BTM). Meanwhile, the uninterruptible load voltage is promised during the mode transition. The small-signal analysis is also conducted to investigate the stability of EEM and BTM. Finally, extensive experimental results are provided to validate the effectiveness of the proposed methods.
TL;DR: The results provided have been compared, corroborating the importance of taking into account the economic aspects of the regulatory constraints when managing the facility and highlighting the urgency to extrapolate this approach to other countries in order to enhance the economic feasibility of these facilities and aid to their deployment.
TL;DR: Simple PQ assessment models and a series of controlled experiments are proposed and carried out in a real ship under sea-going conditions considering nonlinear bow thruster load and high power ballast pump loads under unbalanced and harmonic voltage conditions.
Abstract: Power quality (PQ) is becoming more and more critical issue in shipboard microgrid systems (SMGs) Especially, the impact of voltage unbalance combined with harmonic distortions on the SMG behavior has not been fully investigated In this paper, simple PQ assessment models and a series of controlled experiments are proposed and carried out in a real ship under sea-going conditions The ship experimental results are presented and discussed considering nonlinear bow thruster load and high power ballast pump loads under unbalanced and harmonic voltage conditions In addition, the analysis of bow thruster current harmonic surges during the ballast pump start-up is presented Furthermore, the voltage/current distortions of a working generator, bow thruster and pump loads are analyzed The paper provides a valuable analysis for coping with PQ issues in the SMG
01 Sep 2019
TL;DR: In this article, the authors presented a method which mimics coupled nonlinear Poincare-Bendixson oscillators synchronization to realize current sharing in islanded three-phase Microgrid.
Abstract: This paper presents a method which mimics coupled nonlinear Poincare–Bendixson oscillators synchronization to realize current sharing in islanded three-phase Microgrid. We propose that each inverter be controlled to imitate the dynamics of coupled oscillators. When they are controlled to interact strongly enough, they will all start synchronization. We also introduce the comparison between Van der Pol oscillator corresponding to their physical characteristics. The dual-loop based on the oscillator is designed in αβ frame, and the phase dynamics are derived to observe system initial state performance. The behavior and performance of the proposed method were verified experimentally regarding load connection, inverter removal and current ratios changes.
TL;DR: The feasibility of the proposed regeneration protection solution is verified by experimental results from the parallel UPS system prototype and an active power-sharing control strategy by regulating the virtual resistance is proposed to solve the circulating current caused by UPS regeneration issue.
Abstract: 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 control strategy is proposed to protect the inverter against the excessive dc-link voltage that may trigger the protection mechanism of the UPS system. In addition, an active power-sharing control strategy by regulating the virtual resistance is proposed to solve the circulating current caused by UPS regeneration issue. Finally, the feasibility of the proposed regeneration protection solution is verified by experimental results from the parallel UPS system prototype.
TL;DR: An evaluation method is proposed to estimate the expected severity of voltage dips and also generator current transient surges due to the onboard motor startups under real sea-going conditions using the Riemann-summation-principle evaluation method.
Abstract: High power motor loads are widely used in shipboard microgrids (SMGs) consuming about 70% of the 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 with maritime standards. In this paper, an evaluation method is proposed to estimate the expected severity of voltage dips and also generator current transient surges due to the onboard motor startups under real sea-going conditions. This is based on the Riemann-summation-principle evaluation method. The quasi-balanced and unbalanced ac bus voltage cases are carefully selected to present the actual impact of the voltage dips in real SMG. The evaluations are validated by measurements gathered from the ballast pump motor startup in the SMG. The proposed method can provide ship engineers with necessary information about the actual magnitude/depth of voltage dips. Accordingly, the allowable capacities of high-power motors can be estimated, which is beneficial to determine proper motor starter designs and improve the power quality in real SMGs.
01 Nov 2019
TL;DR: The simulation results demonstrate that the proposed power management system (PMS) of vessels is proposed to monitor and prevent the blackout by using the model predictive controller (MPC) based on optimal control method in order to estimate the future power demand in the hostile environment.
Abstract: This paper presents the power management system (PMS) that relies on optimal power planning and maximum energy efficiency in dynamic positioning (DP) drilling vessel. Nowadays, it is becoming an improving demand for higher precision and decreases ship motion induced by environmental disturbance such as wind, waves, and sea current, which leads to the use of power generation more efficient. According to this, an efficient strategy solution and schedule have increased significantly for power management of diesel generator (DG) units on marine vessels as an independent microgrid to the utility grid. Thus, the power management system (PMS) of vessels is proposed to monitor and prevent the blackout by using the model predictive controller (MPC) based on optimal control method in order to estimate the future power demand in the hostile environment. Due to nonlinear characteristics of diesel generators, such as power ramp rate limits and non-smooth cost functions, a particle swarm optimization (PSO) is applied to solve the economic dispatch (ED) problem for a dynamic system. The simulation results demonstrate that the proposed method can improve ED operation problems more efficiently while meeting DGs constraints.
TL;DR: The development and the experimental validation of a novel dynamic model of an islanded three-phase Inverter-based Microgrid (IMG) that reproduces the relevant system dynamics without excessive complexity and enough accuracy is presented.
Abstract: The development and the experimental validation of a novel dynamic model of an islanded three-phase Inverter-based Microgrid (IMG) is presented in this paper. The proposed model reproduces the relevant system dynamics without excessive complexity and enough accuracy. The dynamics of the IMG are captured with a compact and scalable dynamic model, considering inverter based distributed generators with d-current droop primary and proportional resonant inner controllers. The complete development of the model, the practical assumptions, and the accurate proportional power sharing of the primary control technique are shown. The accuracy performance was verified in experiments performed at the Aalborg Intelligent Microgrids Laboratory for an islanded IMG case.
10 Jun 2019
TL;DR: A combined topology is proposed, which consists of a hybrid active power filter connected to the switchboard via a series passive filter and a parallel fixed capacitor-thyristor controlled reactor (FC-TCR) to overcome the aforementioned deficiencies of the SPS.
Abstract: Over recent years, due to the fast expansion of power electronics technology onboard shipboard power systems (SPSs), harmonic contamination has become one of the main concerns. Moreover, the SPSs are characterized by heavy pulsed loads, which can draw a large amount of power in a short duration, which usually causes a voltage drop. If the latter exceeds the norms, a voltage collapse might occur and leads to the blackout of the ship. The contribution of this paper is to propose a combined topology, which consists of a hybrid active power filter (HAPF) connected to the switchboard via a series passive filter (hereafter called HAPF), and a parallel fixed capacitor-thyristor controlled reactor (FC-TCR) to overcome the aforementioned deficiencies of the SPS. Based on the model predictive control (MPC) and synchronous reference frame technique (SRF), the HAPF estimates the harmonics of the system and counter them, while the FC-TCR is designed to act as a low-pass filter and a reactive power compensator to enhance the stability and reduce the distortion of the voltage. The modeling and control of the proposed topology are presented. Furthermore, the voltage stability analyses of the SPS are conducted. Finally, the performance of the proposed topology is carried out under MATLAB/Simulink environment, and the results demonstrate the efficacy of the HAPF and the FC-TCR in suppressing harmonics and improving the voltage stability of the SPS.
01 Dec 2019
TL;DR: Through intensive simulation studies of a practical shipboard power system, which are carried out in MATLAB/Simulink environment, it is demonstrated that the FC-TCR can enhance the power quality and voltage stability of SPSs better than traditional PPFs filters.
Abstract: In the last decades, due to the substantial evolution of shipboard power systems (SPSs) towards all-electric ships, power quality (PQ) issues onboard ships have become a serious challenge. To deal with this problem, using active filters may not be very practical because they have limited rated powers, high implementation cost, and other deficiencies particularly for medium-voltage SPSa. Some cost-effective solutions such as passive power filters (PPFs) and fixed capacitor-thyristor controlled reactors (FC-TCR) might be a reliable solution for medium voltage SPSs due to their capability to operate in medium and high voltage applications, low cost and easy maintenance. The contribution of this paper is to provide more in-depth analysis and mathematical development to evaluate and compare the performance of these solutions. Moreover, developed mathematical formulas are suggested to enhance the FC-TCR capability in terms of harmonic filtering. Through intensive simulation studies of a practical shipboard power system, which are carried out in MATLAB/Simulink environment, it is demonstrated that the FC-TCR can enhance the power quality and voltage stability of SPSs better than traditional PPFs filters.