Active Power Decoupling (APD) circuits enable the use of long lifetime capacitors (film or ceramic capacitors) in single phase power converters. Owing to the inclusion of the APD circuits, the literature reports (1.5 to 1.8)% drop in efficiency of single phase converter at rated power. This reduction in conversion efficiency is one of the significant challenges in the practical use of APD circuits. This paper proposes an approach to reduce the power loss in the bidirectional buck converter based APD circuit. This approach is presented with the help of analytical calculations and graphical representation of operation of APD circuit. The proposed approach requires rapid variation in the average voltage of the buffer capacitor with a change in inverter power. To achieve this, an enhanced control technique is suggested with a duty ratio injection controller. The steady state and transient response of the proposed control technique is validated with simulation and experimentation. Further, the reduction in power losses realized by the proposed approach is verified with the help of a developed laboratory prototype. The proposed approach obtains up to 1% improvement in efficiency of single phase converter at rated power, when compared with existing APD approaches.
This article presents a protection scheme based on the magnitude-phase plane of impedance difference (ID) using wide-area positive sequence components of current and voltage signals for the microgrid. The computation of the ID of the line is performed by extracting signals from the phasor measurement units complied with IEEE C37.118 standards. The composite magnitude-phase plane obtained from the magnitude of the ID and the angle of ID is considered as the key index for the detection of faults. The feasibility to include the proposed microgrid protection technique is examined by the extensive fault cases simulation with substantial variation in fault conditions, including types of fault and fault at different line length and for the grid-connected and islanding modes of microgrid operation. The fault study is carried out on a medium-voltage 15 bus test microgrid and a standard IEEE 34 bus microgrid testbed. The impact of several critical no-fault conditions is also investigated to analyze the possibility of false operation. The proposed ID-based scheme is extensively tested on MATLAB/Simulink platform and validated on the real-time digital simulator. The test results indicate that the magnitude-phase plane of the ID-based scheme can provide a dependable microgrid protection measure.
Abstract:This paper presents a microgrid composed of photovoltaic (PV) array‐battery energy storage (BES) and a diesel generator (DG) set. A bidirectional DC–DC converter (BDDC) is used to integrate the BES to the DC link of the voltage source converter. The BDDC controls the voltage at the DC link to the output voltage of the maximum power point tracking (MPPT) controller, thereby PV array always operates at its maximum power point (MPP). Another function of the BDDC is to block the second‐order harmonic from the BES, when the microgrid is feeding with unequal loads in the three phases. The magnitude of DG set terminal voltages is regulated by an electronic automatic voltage regulator (AVR) that controls the excitation to the synchronous generator. A fast, accurate and oscillations‐less modified variable step size least mean square based adaptive control is used here for improving the power quality. The main features of this microgrid topology are the operation of the PV array at its MPP in all operating scenarios, regulation of DG set voltages, harmonics elimination, balancing of DG set currents and reactive power compensation for the unity power factor operation.
Abstract:In this study, a proportionate power sharing among the parallel inverters operating in an islanded microgrid is achieved using droop and virtual inductance control. The same droop coefficients are used to achieve the frequency regulation as well. The frequency changes which are inevitable in droop control are measured and used to emulate the behaviour of damping and inertia to the DC link voltage using hybrid energy storage system consisting of battery and supercapacitor units. The proposed DC link voltage regulator restores the DC link voltage quickly by providing power corresponding to the rate of change of frequency and frequency deviation. This reduces the impact of voltage variations on the DC-load and keeps modulation index within the linear range for voltage source inverter. The design aspects of DC link voltage regulator, damping and inertia constants, selection of battery and supercapacitor units based on rating of the DC link voltage are discussed. The proposed decentralised droop control and DC link voltage restoration methods are validated through detailed simulation and experimental studies.
Abstract: This study presents the control of distribution static compensator (DSTATCOM) using band-dependent variable step size (BD-VSS) individual weighting factor with sign error based adaptive filter for power quality improvement in a weak distribution grid. Here, the proposed algorithm is used for estimation of fundamental active weight components from the distorted load currents in order to generate the reference grid currents to mitigate the grid currents power quality issues. This new control algorithm is proposed for fast and accurate estimation of active weight components with low steady-state error, without dynamic oscillation at fast convergence speed. Moreover, the frequency locked loop-double self-tuning second-order generalised integrator based voltage filter is used to extract the positive sequence voltages of the distorted grid voltages for estimating the harmonics, and noise-free voltage unit templates. Therefore, the DSTATCOM with the proposed control algorithm is capable of mitigating the harmonic currents, providing reactive power compensation and operating at unity power factor in a weak distribution grid. Test results demonstrate the viability and robustness of the proposed control algorithm under balanced and unbalanced non-linear load conditions.
Abstract:The incorporation of ancillary services on dis-tributed generators (DGs) at utility level has imposed severalchallenges on the existing distribution networks. To address oneof such problem, this paper discusses the impact of ancillaryservices, mainly the voltage ride through (VRT) capability andactive power curtailment control (APCC) of DGs on their anti-islanding protection scheme (AIPS). In this study, different typesof load models (viz. ZIP, induction motor (IM) and compositeloads) have been considered and non-detection zone (NDZ)characteristics are obtained for a modified IEEE 1547/ UL 1741test system for analyzing the problem. Further demonstrationof this issue has been carried out by conducting time domainsimulations in PSCAD/EMTDC platform on modified IEEE 1547and CIGRE low voltage benchmark test system having compositeloads at each of the load buses. Finally, an appropriate mitigationframework has been proposed by incorporating a hybrid island-ing detection technique to enable simultaneous implementation ofVRT, APCC and AIPS in DGs. The online implementation of theproposed framework is realized in MATLAB/Simulink platformand real-time simulations are performed in OPAL-RT (OP5600)test bed on the modified IEEE 1547/ UL 1741 test system forvalidating its efficacy.
Abstract:The relative share of renewable energy, specifically the solar photovoltaic (PV), is increasing exponentially in the world electric energy sector. This is a cumulative result of reduction in the cost of solar panels, improvement in the panel efficiency, and advancement in the associated power electronics. Among different types of PV plants, installation of small-scale rooftop PV is growing rapidly due to direct end-user benefits and lucrative governmental incentives. There are various standards developed in regards to grid integration of PVs and other distributed generations (DGs). Different power converter topologies are developed to interface the PV panel with the utility grid. To keep up with the stringent regulations imposed by the standards, various control strategies and grid synchronization methods have been developed. This review article amalgamates and summarizes all of the aforementioned aspects of a grid-integrated PV system including various standards, power stage architectures, grid synchronization methods, operation under extreme events, and control methodologies, pertaining to small-scale PV plants. This article will help freshman researchers to gain some familiarity with the topic and introduce them to some of the key issues encountered in this field.
Abstract:A solar photovoltaic (PV)-battery energy storage-based microgrid with a multifunctional voltage source converter(VSC) is presented in this article. The maximum power extractionfrom a PV array, reactive power compensation, harmonics mit-igation, balancing of grid currents and seamless transition fromgrid connected (GC) mode to standalone (SA) mode and vice versa,are performed in this system. Whenever the grid fails, this systemoperates in SA mode automatically, thereby without causing anyinterruption in supplying the load. Similarly, it automatically shiftsto the GC mode, when the grid is restored. The VSC functions incurrent control for GC mode, and it operates in voltage controlfor SA mode of operation. This system is capable of extracting themaximum power from the solar PV array irrespective it is operatingin the GC mode or SA mode. The charging and discharging of thebattery are controlled by using a bidirectional dc–dc converter. Itregulates the dc-link voltage to the maximum power point voltageof the PV array. If the absence of the battery is detected, thenthe control is automatically shifted to VSC for performing theextraction of the maximum power of the PV array.
Abstract:The presence of phasor measurements in ac systems provides a range of protection techniques based on sequence components and phase comparison to discriminate the fault. However, the absence of phasor measurements in dc system reduces the available alternatives for fault detection. In addition, the presence of low fault tolerant converters, large range of fault impedance and varying grid conditions demands sensitive and selective protection schemes. In this regard, several recent works have suggested a communication-based primary protection due to its high sensitivity to faults. However, with a failure in the communication network, the primary protection will also fail to detect a fault. This paper proposes a backup scheme to isolate the faulty section, even in the case of a communication failure. In the literature, overcurrent- and undervoltage-based backup protection schemes are suggested along with unit primary protection. In the presence of low fault tolerant converters and variable fault resistances, the traditional backup schemes may not work well. This paper proposes a new fault detection method for backup schemes, which utilizes only the locally measured current signal, and uses both derivative and integral characteristics of current to ascertain the occurrence of a fault. The proposed method is capable of detecting the fault accurately and within the required time. The performance of the proposed scheme has been assessed on a � 600 V TN-S grounded dc microgrid under various conditions using hardware-in-loop simulations on real-time digital simulator.
Abstract:Switched-mode power converters are used to interface equipments andconsumer electronic devices over a wide range of power levels. The switch technology ofany power converter is a signature of its power rating. The article discusses differentpower electronic switch technologies used in modern power supply implementation andevaluates their impact in the system design. From the design prospective, power loss ismore important than efficiency. It can be established that as power level of converter goesup, it is indispensable to have higher efficiency due to thermal design considerations.A trend between the switching frequency and its efficiency with respect to the powerrating of the converter has been inculcated in the article.
Abstract:In this paper, the effect of jamming in free space optical (FSO) link, is evaluated by deriving closed-form expressions of the bit error rate (BER) and outage probability (OP) for single-input single-output (SISO) and multiple-input single-output (MISO) FSO systems. The effects of partial-band jamming and broadband jamming over the error performance of the considered FSO systems are also analyzed. The jammer behaves as a random noise source, following the negative exponential distribution-due to the atmospheric turbulence. Therefore, in the presence of jammer, the error performance of FSO systems is governed by the additive negative exponential noise. It is shown by a rigorous analysis that a MISO FSO system can significantly mitigate the effect of jamming. Specifically, we consider a 2×1 FSO system for analysis, and demonstrate the improvement in BER and OP performance an FSO system can gain by using an additional spatial dimension, in the presence of a random jammer. The mitigation of jamming, due to implementation of arbitrary transmit apertures, is also verified through simulation results; which lies in complete agreement with the analytical results. Also, the error performance under the jamming effect is studied numerically over the Gamma-Gamma fading channel incorporated with pointing error effect.
Abstract:Synchronous reference frame (SRF) control strategy for solar photovoltaic (SPV) sources is widely used to delivermaximum power to the grid. However, poor inertia support just after a disturbance and improper phase angle tracking inpresence of the harmonics and system unbalance are noticed when the conventional phase-locked loop (PLL) based SRFcontrol structure is used. In this study, an inertia enhancement method for inverter interfaced SPV sources is proposed, whichadjusts only the PLL parameters with a notch filter (NF) in the SRF controller. NF in PLL is used due to its disturbance rejectionpotential and accurate phase angle tracking, even during system unbalance. The dynamic equation of pseudo induced voltage(PIV) vector with respect to the point of common coupling is derived. The kinematic equation of the PIV angle vector correlatesinertia contribution and inverter terminal voltage. The impact of the change in PLL parameters on inertia enhancement isanalyzed by validating the proposed technique on a test system in the real-time digital simulator. The frequency response by theproposed method has been compared with two state-of-art methods to prove the superiority of the proposed approach inenhancing the inertia of the SPV source in a microgrid.
Abstract:Point wind velocity measurement given by nacelle-top mounted sensor may not be same as effective wind velocity, which strikes the wind turbine rotor blades. This article proposes a new method for the computation of effective wind velocity by inverting the turbine's aerodynamic model after estimating the turbine torque and its rotor speed. Nonlinear control theory-based sliding mode observers are used to estimate the wind turbine generator induced speed emfs, rotor speed, and aerodynamic torque imparted to generator shaft. While satisfying the Lyapunov inequality condition, design aspects of sliding mode observers are discussed in detail. The performance of the proposed wind velocity estimation method is evaluated by using permanent magnet synchronous generator-based wind turbine emulator in laboratory. Simulation and experimental studies confirm that the estimated wind velocity under different wind profile conditions is accurate and can be used in various control algorithms in wind energy conversion systems.
Abstract: Utility-interfaced power electronic systems use a grid synchronizing framework, known as phase locked-loop and need transformation of sinusoidal signals to rotating dq reference frame, for control purpose. The voltage or current signal parameters including instantaneous fundamental frequency, phase angle, amplitude need to be captured in presence of harmonics, noise and DC offset. This work proposes an adaptive estimation scheme for the same, using recursive least squares with time-varying covariance gains. Proposed adaptation of gain presents faster transient response and noise-tolerant steady-state response, achieving optimal trade-off between the two. Covariance resetting mechanism is presented for better dynamic profile during step-changes in the signal. The scheme for single phase signal transformation is extended for transforming three phase unbalanced sinusoids to decoupled double synchronous reference frame. Stability analysis, design guidelines and discrete-time realization of proposed methods is provided for reproducibility. Theoretical deductions of proposed method are supported with several comparative test cases simulated in MATLAB/Simulink as well as the experimental results.
Abstract: This article proposes an optimal charging and dis-charging schedule for a hybrid photovoltaic-battery system con-nected in the premises of a residential customer. The schedulingstrategy is formulated to minimize the electricity bill of the cus-tomer. The proposed scheme uses the data obtained from short-term load, weather, and solar forecasting. A time-of-use tariffscheme is considered to be implemented by the utility. The proposedmethod is tested on real residential load and solar generationscenario. The test results verify that the implementation of theoptimal battery scheduling algorithm can significantly increase thenet saving in the electricity bill of the customer.
Abstract:System inertia plays a vital role in controlling theangular stability of the system during a disturbance. Due toincreased penetration of power electronic interfaced sources, suchas Solar Photovoltaic (SPV) source, the overall system inertiareduces and varies depending on their operating conditions. Inthis paper, an approach for online inertia estimation in thepower system network with SPV sources is proposed, using thesynchronized measurements from Phasor Measurement Units(PMUs). An equivalent swing equation is used to emulate thenetwork dynamics. A relationship between the inertia constantand the roots of this equation is determined. In order tonumerically obtain the roots, the Estimation of Signal Parametervia Rotational Invariance Techniques (ESPRIT) method is firstused to find the modes present in the frequency signal. A newformulation is proposed to extract an equivalent mode from allthe obtained modes. Also, to avoid phase step error, Rate OfChange Of Frequency (ROCOF) is estimated from the equivalentmode of the frequency signal. Results obtained for the39busNew England system for various test cases, using Real-TimeDigital Simulator (RTDS), prove the efficacy and superiorityof the proposed approach over the existing approaches in theliterature.
Abstract: This paper develops a robust control strategy forvoltage regulation of customer-end AC loads, where the lowvoltage multi-terminal DC network has been used for powerdistribution purpose. The control law for load-end DC-ACconverter is synthesized by Lyapunov’s direct method usingbackstepping design process. The resultant control action issimply obtained by linear combination of states and referenceset-points, and do not add extra dynamics into the systemavoiding complexity. The proposed method does not require loadcurrent measurement. Simulation studies in MATLAB/Simulinkshow better dynamic performance compared to conventional PIcontrollers. The experimental results from a laboratory-scaleprototype demonstrate robustness of proposed controller againstvariations in type and amount of load profile as well as DCvoltage.
Abstract: In this article, the presented work proposes a power management scheme in a dc microgrid by utilizing integrated device level control designs. Dynamics of nondispatchable energy sources, energy storage systems, and critical loads while synthesizing the control scheme are extensively studied. The presented work focuses on the integrated operation of local converter controls and power control unit during load fluctuations, environmental changes, accidental islanding, state of charge (SOC) breach, etc., without any time-critical information sharing. Low bandwidth communication (LBC) assisted control actions are enabled only in response to specific events such as battery management system (BMS) operation in autonomy, onset of peak hours, and load shedding. This article examines small signal analysis of individual interfacing converters to conduct eigenvalue studies of the closed-loop control systems. Successful control transitions are achieved in real-time digital simulator to validate the proposed management strategy under various system conditions. Hardware-in-the-loop setup validates the implement-ability of the control strategy in dc microgrids.
Abstract:In this paper, the groundwork on jamming effect and its alleviation mechanismsin free space optical (FSO) communication are studied over Gamma-Gamma (GG) fadingchannels along with the pointing error (PE) effects. A closed-form expression of the biterror rate (BER) is evaluated analytically for a single-input single-output (SISO) FSO systemin the presence of jammer. The worst case jamming condition for maximization of erroris calculated numerically. The jammer channel is considered to be GG distributed. Beingthe most dominating noise, the jamming signal is acted as the only noise source in theconsidered FSO set-up. Therefore, this study is performed over additive GG noise channel.The error performances are investigated for different atmospheric turbulence (AT) regimes(weak to strong) and for different PE parameters of jamming noise. Moreover, to combatthe jamming effect, a multiple-input single-output (MISO) FSO system is considered. Aclosed-form expression of the BER of the multiple transmit channels over the GG noiseis analytically calculated. The analytical results for both SISO and MISO FSO systems areverified with the help of the simulation results obtained by MATLAB software. It is establishedthat MISO FSO performs better than SISO FSO system in terms of BER performance underthe influence of jamming noise. Furthermore, many important observations are made uponthe BER performances for different AT and PE parameters for SISO and MISO FSO systems.
Abstract:This article elucidates a real-time energy management strategy for a smart residential apartment building having nonidentical occupants at the dwelling units (DUs). The aim of the present article is to design a distributed energy management algorithm, which can optimize the real-time demand of the entire building against abruptly updated rooftop solar generation and real-time price (RTP) of energy. The proposed energy management strategy differentiates among the DUs by considering a new parameter named load criticality level, which is defined as the value imposed by the DU residents to their power consumption. The optimization portfolio is developed as a novel bilevel, stochastic, multiobjective optimization problem where the maximization of utility of the consumed power is considered simultaneously with the cost minimization. To this end, a virtual energy trading platform is designed in this article between central building management system and the DUs, where they interact with each other by following the directives of single-leader multifollower Stackelberg game. The solution strategy is proposed as a Lyapunov optimization, which needs only the current values of the uncertain parameters, such as load variation, renewable generation, and energy price, and do not require any knowledge about their probabilistic variation, to eliminate the complexities regarding time average stochastic equations. Strenuous simulation on real-time data of four DUs, it is proved that the proposed framework can track the abrupt change in RTP and solar generation efficiently. Comparing with two benchmark methods viz. centralized process and greedy algorithm, the superiority of the designed energy management portfolio is established.
Abstract: In this work, the authors consider the communication network of a power substation, where multiple intelligent electronic devices (IEDs) transmit their delay sensitive control and monitoring messages to a common receiver over a wireless network; in the presence of a broadband jammer, which is capable of jamming multiple channels simultaneously. The objective of the IEDs is to successfully transmit their messages within a specified time, whereas the jammer wants to obstruct IED's transmission. A novel utility function is designed for the players, that addresses the time-critical nature of communication. Due to the conflicting interest of the IEDs and the jammer, they model the interaction between them as a repeated Bayesian zero-sum game, which also addresses the repeated interaction among the IEDs and the jammer, and the unavailability of exact information about the jammer. The equilibrium strategies for both the scenarios of perfect and imperfect monitoring are derived and verified through simulation results. Further, the performance of the proposed game model in various scenarios is thoroughly compared in the result section. Finally, the efficacy of the proposed defence strategies is tested in a practical communication network of a power substation under jamming, which is simulated in Optimised Network Engineering Tool (OPNET).
Abstract:This paper deals with the design and stability analysis
of a DC microgrid with battery-supercapacitor energy storage
system under variable supercapacitor operating voltage. The
conventional design method reported in the literature considers
the rated supercapacitor voltage in the modeling and design of
controllers. However, the supercapacitor unit can discharge as
low as 10% of its rated voltage due to self discharge. It is observed
that the conventional method of controller design can potentially
make the system unstable or introduce ringing in the DC link
voltage at low supercapacitor voltage. In this work, the sensitivity
of DC microgrid stability with respect to supercapacitor voltage
variation is analyzed, an optimal supercapacitor voltage to be
considered in the design is calculated and a design method is
proposed to ensure the stability of DC microgrid in all operating
modes. The stability of the DC microgrid with controllers
designed using the proposed method is evaluated with digital
simulation and experimental studies.
Abstract:This paper proposes a centralized control strategy
for power management of hybrid microgrid connected to the
grid using a parallel combination of grid side converters (GSCs).
An improved version of instantaneous symmetrical component
theory (ISCT) is developed and is used for the control of parallel
operated GSCs, which results in reduced sensor requirement,
control complexity, and communication bandwidth. In addition,
a simple power management algorithm is developed to test the
efficacy of the proposed parallel grid side converter control
strategy for all the microgrid modes considering state of charge
(SOC) limits of hybrid energy storage system (HESS), load
changes, and renewable power variations. In the proposed system,
a better dc link voltage regulation is achieved and usage of
supercapacitor reduces the current stresses on the battery. With
the proposed control strategy, the essential features of grid
side converters like power quality, power injection, bidirectional
power flow and proportional power sharing are achieved. The
effectiveness of the developed control strategy for the proposed
system is tested using MATLAB based simulink environment and
validated experimentally using a laboratory prototype.
Abstract:The AC-DC distribution systems have recently gained huge popularity due to advancements in power converters, high penetration of renewable energy resources and wide usages of DC loads. However, load flow in such systems is a challenging task due to non linear characteristics of power converters. This paper presents a novel load flow algorithm for AC-DC distribution systems, utilizing the concept of graph theory and matrix algebra. Four developed matrices, loads beyond branch matrix [LB], path impedance matrix [PI], path drop matrix [PD], slack bus to other buses drop matrix [SBOBD] and simple matrix operations are utilized to obtain load flow solutions. These matrices reveal the network topology and relevant information about the behaviour of AC-DC distribution network during load flow studies. In contrast with traditional load flow methods for HVDC systems, the proposed technique does not require any lower upper (LU) decomposition, matrix inversion and forward-backward substitution of Jacobian matrix. Because of the aforementioned reasons, the developed technique is computationally efficient. The proposed method has been tested using several case studies of AC-DC distribution network which includes different operating modes of various power converters. Results show feasibility and authenticity of the proposed method.
Abstract: Home energy management systems (HEMS) encourage
participation of residential consumers into the demand response
programs. This paper proposes a robust-CVaR (Conditional Value at
Risk) optimization approach for day ahead HEMS to reduce the effect
of risk of real time exposure to energy price and solar power
generation uncertainties. Initially the CVaR method is integrated
with the Two-point Estimation (2PE) analysis to approximate the
solar power, modelled as Beta probability distribution function, in
low computation effort compared to conventional Monte Carlo
Simulation (MCS) based CVaR approach. Then the optimization
constraints are revised to their robust counterparts by accounting a
certain amount of uncertainty in the energy prices from their nominal
values. Unlike previous literatures, the optimization problem is
developed to minimize the risk value of the energy cost. Again to
maximize the life of the plug in electric vehicle (PEV) a pseudo cost
function for the PEV battery degradation is proposed. The entire
optimization portfolio is developed as a mixed integer linear
programming (MILP) for its easy execution. Simulation is
demonstrated on a smart home, designed as an AC-DC microgrid
(MG), having practical appliance data sets, to prove the efficacy of the
Abstract: In this paper, we study the physical layer secrecy performance of a hybrid satellite
and free-space optical (FSO) cooperative system. The satellite links are assumed to follow
the shadowed-Rician fading distribution, and the channel of the terrestrial link between
the relay and destination is assumed to experience the gamma–gamma fading. For the
FSO communications, the effects of different types of detection techniques (i.e., heterodyne
detection and intensity modulation with direct detection) as well as the pointing error are
considered. We derive exact analytical expressions for the average secrecy capacity and
secrecy outage probability (SOP) for both cases of amplify-and-forward (AF) and decodeand-
forward (DF) relaying. The asymptotic analysis for the SOP is also conducted to provide
more insights on the impact of FSO and satellite channels on secrecy performance. It is
found that with the AF with fixed gain scheme, the secrecy diversity order of the investigated
system is only dependent on the channel characteristics of the FSO link and the FSO
detection type, whereas the secrecy diversity is zero when the relay node employs DF or
AF with variable-gain schemes.
With increased integration of wind energy systems, an accurate wind speed forecasting technique is a must for the reliable and secure operation of the power network. Statistical methods such as Auto-Regressive Integrated Moving Average (ARIMA) and hybrid methods such as Wavelet Transform (WT) based ARIMA (WT-ARIMA) model have been the popular techniques in recent times for short-term and very short-term forecasting of wind speed. However, the contribution of the forecasting error due to different decomposed time series on the resultant wind speed forecasting error has yet not been analyzed. This paper, thus explores this shortcoming of the ARIMA and WT-ARIMA models in forecasting of wind speed and proposes a new Repeated WT based ARIMA (RWT-ARIMA) model, which has improved accuracy for very short-term wind speed forecasting. A comparison of the proposed RWT-ARIMA model with the benchmark persistence model for very short-term wind speed forecasting, ARIMA model and WT-ARIMA model has been done for various time-scales of forecasting such as 1min, 3min, 5min, 7min and 10min. This comparison proves the superiority of the proposed RWT-ARIMA model over other models in very short-term wind speed forecasting.
With the rapid proliferation of the advanced metering infrastructure, the smart grid is evolving towards increased
customer participation. It is now possible for a utility to influence the customer demand profile via
demand side management techniques such as real-time pricing and incentives. Energy storage devices play a
critical role in this context, and must be optimally utilized. For instance, the peak power demands can be shaved
by charging (discharging) the batteries during periods of low (high) demand. This paper considers the problem
of optimal battery usage under real-time and non-stationary prices. The problem is formulated as a finite-horizon
optimization problem, and solved via an online stochastic algorithm that is provably near-optimal. The proposed
approach gives rise to a class of algorithms that utilize the battery state-of-charge to make usage decisions in
real-time. The proposed algorithms are simple to implement, provably convergent for a wide class of nonstationary
prices, easy to modify for a variety of use cases, and outperform the state-of-the-art techniques, such
as those based on the theory of Markov decision processes or Lyapunov optimization. The robustness and
flexibility of the proposed algorithms is tested extensively via numerical studies in MATLAB and real time digital
Abstract: Quick fault detection and isolation of faulty section are desired in DC microgrid due to the presence of power
electronic converters and low cable impedances. Owing to need of fast disconnection, limited time and data are available for
online fault distance estimation. Some of the existing techniques consider source capacitors connected at only one end of the
cable; therefore, assume that the fault current is contributed by only one end of the cable. This may not be true in the case of
multi-source DC microgrids, where fault current would be supplied from both the ends. Further, existing communication-based
techniques require either data synchronisation or fast communication network. To address these issues, this study proposes an
online fault location method for multi-source DC microgrid without using communication. The mathematical model of faulted
cable section connected to sources at both the ends is derived. This model is used along with the measurements to determine
the fault distance. The model consistency with the measurements is quantified using the confidence level based on the residual
analysis. A ring-type multi-source DC microgrid system is considered and simulated on real-time digital simulator to demonstrate
the effectiveness of the proposed algorithm.
Abstract:This paper deals with the protection of critical
loads from voltage-related power quality issues using a
dynamic voltage restorer (DVR). A generalized control algorithm
based on instantaneous space phasor and dual P -Q
theory has been proposed to generate the instantaneous
reference voltages to compensate the load voltages with
direct power flow control. The proposed algorithm adapts
energy-optimized series voltage compensation, which results
in a reduction of energy storage requirement. The
proposed DVR control scheme can support the load from
voltage-related power quality issues irrespective of the load
current profile. Each leg of the three-phase three-leg split
capacitor inverter is used to inject series compensation voltage
in respective phases of the system. Model-based computer
simulation studies and real-time experimental results
validate the effectiveness of the proposed control algorithm.
Abstract: Real-time visualisation of large power systems, by tracking the system states, is a challenging task as it involves
processing a large measurement set to obtain the system states. This study proposes a hierarchical parallel dynamic estimation
algorithm to estimate the states of a large-scale interconnected power system. The power system is decomposed into smaller
subsystems, which is processed in parallel to obtain a reduced order state estimate. This information is then transmitted to the
central processor, which collates the individual reduced order estimates to obtain the global estimates. Each processor uses
state matrix of smaller dimension, thereby reducing the computational burden. The low-level processors utilise only a fraction of
the global measurements in the proposed approach, and there is no need for any information exchange from the central
processor to the low level processors, which helps in reducing the communication requirements. Moreover, detection of
anomalies can also be carried out at the local processors without the need for any separate bad data detection at the central
processor. IEEE 30- and 118-bus systems are used as test beds to study the proposed approach.