Electric Spring Research Articles

Mechanism analysis and control method of electric spring off-limit failure based on two-port impedance model

Mechanism analysis and control method of electric spring off-limit failure based on two-port impedance model

Control and Power Management Strategy for Shunt DC Electric Spring Integrated DC Microgrid

Incorporation of intermittent renewable sources and nonlinear loads to DC microgrid (DCMG) has increased its vulnerability to voltage instability and flicker. An innovative Demand Side Management (DSM) program that can help in mitigating these voltage disruptions is the deployment of DC Electric Spring (DCES) technology. In this regard, this paper focuses on small signal modeling and controller design of shunt DCES (ShDCES) in DCMG. The test system comprises of an MPPT controlled Solar Photo-Voltaic (SPV) system, battery-operated DCES and various loads. The MATLAB / Simulink performance analysis of the system indicates that, with the incorporation of power management strategy, the ShDCES configuration has enhanced the power quality of SPV-fed DCMG with fast dynamic response in comparison with its “series” counterpart. The effective utilization of battery operated DCES on the load side, instead of the source side, makes it less battery dependent, resulting in enhancement of battery life and lesser environmental hazards. The simulation results are also validated using real-time simulator OP4510 RTS.

A Shunt DC Electric Spring-Based Control Strategy for Real-Time Critical and Noncritical Load Management in DC Microgrid

Deployment of DC Electric Spring (DCES) technology is an innovative demand side management (DSM) program that helps to mitigate voltage interruptions. Conventional control strategy uses proportional-integral controllers to regulate DC spring parameters. As PI controllers have a trade-off between settling time and peak overshoot, they may not be able to achieve the desired dynamic performance under varying DC microgrid (DCMG) conditions. In this regard, this paper proposes an inverted zero compensator for the control of shunt DCES (ShDCES) in DCMG. This controller regulates the ShDCES current and terminal voltage under all operating conditions with reduced settling time and peak overshoot. A power management algorithm is also proposed to optimize the operation of ShDCES under the presence of varying PV generation and critical and noncritical loads. A detailed mathematical analysis of ShDCES and inverted zero compensator design are furthermore incorporated to validate the strategy. The simulation of the proposed method is performed in MATLAB/Simulink environment. The comparison analysis with the conventional controller proves the effectiveness of the new controller. The results are also validated using real-time simulator OP4510RTS.

An Improved Electric Spring Topology Based on LCL Filter

Electric spring (ES), which has been widely discussed in recent years, is a new demand response method. By adjusting the power of noncritical load (NCL), ES can adaptively improve power quality of the grid containing a high proportion of renewable energy sources. Most of the existing ESs is connected in series with NCLs, but this structure limits the compensation power range of ES. In this article, a new ES topology based on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> filter is proposed, where NCL is paralleled with the capacitor branch as the shunt damper. Compared with other types of ES, the proposed <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> -ES has the advantages which can extend the adjustable power range, improve the voltage regulation performance, and suppress the inherent resonance spikes effectively. Finally, the feasibility of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> -ES has been verified by simulation and experimental results.

Design of Back-to-Back Converter Interface for Electric Spring in a Distribution System

In a distribution system, the erratic output power of distributed generation causes fluctuations in the available power to critical loads on the demand side. A novel electric spring (ES) with back-to-back converter configuration is proposed. Besides PCC voltage regulation and power control, the proposed converter integrates the ES to the grid without compromising the DC link voltage and the quality of the grid current. It comprises an instantaneous DC link voltage control, active power control, PCC voltage control, and a hysteresis band current control. The systematic design of the parameters in the configuration is detailed. Simulations were performed in MATLAB/Simulink, and a series of comparative analyses at various control stages were demonstrated. The quality of the grid current was analyzed with PI, PR, and hysteresis band current controllers. It was established that the hysteresis band current controller gave the best performance. Similarly, the DC link voltage was efficiently regulated with the instantaneous DC link voltage controller than the conventional controller.

Linear Matrix Inequality Approach for Robust State Feedback Control of Electric Spring: A Device for the Real Time Demand Side Management

Ever-Increasing environmental concern has raised the penetration of renewable energy sources in the power grid, which brings instability to the grid due to its intermittent nature. Electric Spring (ES) was proposed as the decentralized mechanism to bring voltage regulation and stability to the grid, when being installed at the customer’s end. This work focuses on the control aspect of the ES, being used for providing voltage regulation to the critical load by manipulating the voltage across the non-critical load, amidst fluctuating voltage inflicted by renewables, through injecting voltage with appropriate magnitude and phase. State-Feedback control of ES has been designed using the Linear Quadratic Regulator, being optimized using the numerical convex optimization called Linear Matrix Inequalities, to furnish robustness to the control with optimal control effort. The Cyclic Design approach has been used to transform MIMO system into SISO system, to provide simplicity to the controller design without sacrificing its robustness and efficacy. Integrator has been introduced there in, to bring the steady-state error to zero. The superiority of the proposed control has been established through comparison of results derived through this controller with that of a PI controller, which is widely used for executing the control of ES.

A Recapitulation of Electric Spring for Demand Side Management & Power Quality Mitigation

The Mechanical Springs act has developed into electric spring (ES). The efficient law developed by Hooke’s, has been upraised with the new scientific application which pays vital role in this modern society. The main function of this highly new grid technology provides distributed energy storage, voltage regulation, amplify the power quality and stability in a highly and reliable way. So the improvised control scheme has been assist to open new and different avenues to utilize the electric spring to greater extent. Electric Spring is new and innovative concept by which modern society is able to renew natural energy in easy way. Power match between the generation facet as well as the demand facet will be effectively relieved. This theory transforms many non- critical loads with smart loads in the latest century that have automatically following power generation. It is a novel control approach which is needed in the new future smart grid. The previous concept of output voltage control turns into new one that is input voltage control which is based on reactive power to emphasize this work. Because of the rise in the growth of smart grids, micro grids and RESs, it seems to be observed that ES has been growing in popularity for the past few years. It is a form of power system stability solution and it will be ultimate demand side management which is ready to provide stability solutions.

Modeling of electric springs and their multi-objective voltage control based on continuous genetic algorithm for unbalanced distribution networks

This work proposes a multi-objective voltage control for multiple Electric Springs (ESs) in active unbalanced distribution systems, where the goal is to provide a suitable simulation scheme to control the ESs in real-time applications. This multi-objective voltage control relies on a robust ES model, a modified backward/forward solution method (BFSM), and a continuous genetic algorithm (CGA). The proposed ES model is suitable for unbalanced conditions and can be implemented at any network location in single-, two-, and three-phase connections. Also, it considers the self and mutual effects of the distribution line (DL) and the power flow of the elements connected at the point of common coupling (PCC) to determine the ES output voltage. The ES model is adapted to the BFSM to quickly and reliably solve the power flow in the distribution network. Besides, the CGA simultaneously solves the mode of operation and the amount of reactive power exchange of the ESs to minimize power losses, voltage unbalance, and voltage deviation. The proposed voltage control is evaluated on an active distribution network based on a modified IEEE 13-bus for considering both load variations and power intermittences.

Design and Control of a Series-Parallel Elastic Actuator for a Weight-Bearing Exoskeleton Robot.

Weight-bearing exoskeletons are robots that need to carry loads and interact with humans frequently. Therefore, the actuators of these exoskeletons are supposed to be capable of outputting sufficient force with high compliance and little weight. A series–parallel elastic actuator (SPEA) is designed, in this work, to meet the demanding requirements of an exoskeleton robot called PALExo. A gas spring is installed in parallel with an electric cylinder to adjust the force output range of the actuator according to the needs of the exoskeleton. A series elastic module (SEM) is installed in series with the electric cylinder and gas spring to improve the compliance of the actuator, the stiffness of which is variable to adapt to the different stiffness requirements of the exoskeleton’s legs in the standing phase and swinging phase. A force controller combining dynamic compensation and a cascade control with an inner velocity loop and a disturbance observer is designed for the SPEA. The performance of the force controller is verified by experiments and the results demonstrate that the controller has good adaptability to the stiffness of the SEM.

Use of the high voltage source in order to verify the insulation systems of electric motors with the type of protection increased safety used in potentially explosive atmosphere

Evaluation of explosion-proof protected electrical equipment in scope of certification is extremely important considering the risk of explosion that has to be minimized in order to ensure life safety and health of workers and to prevent damaging of property and the environment, as well as free movement of goods when they meet the essential safety requirements at European level. The standards SR EN 60079-0 (Explosive atmospheres. Part 0: Equipment. General requirements) and one or more of the standards containing the specific requirements for the type(s) of protection applied to equipment (ex. SR EN 60079-7 for the type of protection increased safety “e”), are used to perform the assessment. Due to the fact that electric motors with type of protection Increased Safety, whose supply voltage exceeds 1000 V, presents a high risk of sparks occurring in windings, it is necessary to perform tests to verify that the insulation of the windings is adequate and does not lead to electric discharge (through electric springs or sparks) at winding levels.A very important test by which these aspects are verified is the overvoltage-ignition test, applicable to electric motors with increased safety protection type.

Cyber-Attack Detection and Countermeasure for Distributed Electric Springs for Smart Grid Applications

With increasing installations of grid-connected power electronic converters in the distribution network, there is a new trend of using distributed control in a cyber layer to coordinate the operations of these power converters for improving power system stability. However, cyber-attacks remain a threat to such distributed control. This paper addresses the cyber-attack detection and a countermeasure of distributed electric springs (ESs) that have emerged as a fast demand-response technology. A fully distributed model-based architecture for cyber-attack detection in the communication network is developed. Based on a dynamic model of ES with consensus control, a local state estimator is proposed and practically implemented to monitor the system. The estimator is fully distributed because only local and neighboring information is necessary. A countermeasure for the distributed ESs to ride through the cyber-attack and maintain regulatory services in a microgrid is demonstrated successfully. Experimental results are provided to verify the effectiveness of the proposed cyber-attack detection method and its ride-through capability.

Review of Various Application of Electric Spring

Review of Various Application of Electric Spring

Sizing Procedure of Reactive Electric Spring

Reactive electric spring (RES) is a technique aimed at stabilizing the user voltage in presence of grid voltage variations by means of a user-encapsulated circuit. In spite of the numerous papers on the matter, no expressions are still available to size the RES elements. This paper fills this lack, by drawing up a sizing procedure of them. The procedure starts with a targeted investigation of the RES operation and exploits the outcomes to provide expressions for the values of the passive elements as well as for the voltage-current ratings of the voltage source inverter (VSI). The sizing expressions are formulated in normalized form to emphasize their dependence on the parameters of the user non-critical load. Focus of the sizing procedure is on the two RES key-elements, namely the AC-side capacitor and VSI but the AC filter inductor and the DC-side capacitor are also sized. Two options for sizing the AC-side capacitor are also discussed. At last, the study case of a user supplied by a low-voltage distribution line is considered and the sizing expressions are utilized to calculate the RES data. Experimental results, obtained by an on-purpose arranged hardware-in-the-loop (HIL) rig, validate the sizing procedure.

Research on Voltage Stabilizing Control Strategy of Critical Load in Unplanned Island Based on Electric Spring

Aiming to solve the problem of voltage fluctuation of critical load caused by lack of control when an unplanned island occurs in a microgrid, a voltage stabilizing control strategy of critical load based on electric spring is proposed in this paper. When unplanned islanding occurs in a microgrid system, the system bus voltage fluctuates dramatically due to instantaneous power imbalance, compromising the power supply safety of important loads on the bus. In this paper, the electric spring control mode is integrated into the voltage stabilizing control strategy of critical loads in an unplanned island for the first time to realize the protection of critical loads. First of all, a model of an optical storage AC/DC hybrid microgrid is built, the overall system architecture is determined, and the microgrid is divided into four working states. Second, the working principle of electric spring is introduced, and a decoupling control strategy based on double closed loop is proposed. Finally, the experimental simulation of the proposed control strategy is experimentally simulated in Matlab/Simulink environment. The simulation findings show that when the bus voltage and current of microgrid change due to an unplanned island, the proposed control strategy based on electric spring may achieve the stability of voltage and current on critical loads.

Electric Spring and Smart Load: Technology, System-Level Impact, and Opportunities

The increasing use of renewable energy sources to combat climate change comes with the challenge of power imbalance and instability issues in emerging power grids. To mitigate power fluctuation arising from the intermittent nature of renewables, electric spring (ES) has been proposed as a fast demand-side management technology. Since its original conceptualization in 2011, many versions and variants of ESs have emerged and industrial evaluations have begun. This article provides an update of the existing ES topologies, their associated control methodologies, and studies from the device level to the power system level. Future trends of ESs in large-scale infrastructures are also addressed.

Comparison of Voltage Regulation of a Smart Load for 3 Bus System and 15 Bus System under High Penetration of Wind Energy System

Abstract: Modern study about utilizing energy from renewable energy sources was stimulus due to emerging oil crisis in older days due to uncontrolled use of conventional energy sources. Renewable Power Generation from wind and solar energy has become a significant proportion for the overall power generation in the grid. High penetration of Renewable Power Generation (RPG’s) effectreliable operation of bulk power system due to fluctuation of frequency and voltage of the network. The main objectives of high penetration of Renewable Power Generations in distribution system are Regulation of voltage, Mitigating voltage fluctuations due to flickers and Frequency control. The design and control of voltage regulation system using smart loads (SL’s) under large penetration of renewable energy system in distribution level is to be studied with the help of FACT devices like Static Compensator (STATCOM) and It is one of the fast active devices with accurate voltage regulation capability and most importantly for the sensitive/critical loads. Electric spring (ES) is proposed as compelling technique for guideline of framework voltage under fluctuating RPG's with next to no guide of correspondence framework [1]. It is a converter-based framework with self-commutated switches in span design, which is associated with non-basic burdens in series to go about as savvy load. These Smart Loads are controlled to direct voltage across basic burdens and hence partaking popular side administration. Expanded entrance of RPG’s, basically factor speed wind energy transformation framework is having impact on voltage and power quality [1][2]. In this paper, A contextual analysis of impact of variable speed wind energy framework on voltage is completed and which is demonstrated with fluctuating breeze speed. Execution examination of keen burdens are to be contrasted and existing receptive power compensator burdens and Improvement in voltage profile on test feeder is directed on a 3 Bus system and 15 Bus system. Keywords: Renewable energy system (RES), Electric spring (ES), STATCOM, Voltage Flicker, Smart load

Flexibility pricing of integrated unit of electric spring and EVs parking in microgrids

Electric spring (ES) as a breakthrough in power electronics has led to a revolution in demand-side management. This paper presents flexible power management (FPM) of a networked microgrid (MG) in the presence of renewable energy sources (RESs) and flexibility sources (FSs). The FSs include the novel topology of the integrated unit of ES with electric vehicles (EVs) parking (IUEE) and incentive-based demand response program (DRP). The proposed FPM model is formulated as an optimization problem that minimizes the difference between the expected energy cost and the expected profit of FSs' flexibility subject to the AC optimal power flow (AC-OPF), RESs, FSs, and MG flexibility constraints. In the proposed model, flexibility pricing is performed for both upward and downward flexibility services in which the expected flexibility profit is proportional to the product of the FSs' flexibility and flexibility incentive price (FIP). Further, this paper uses a stochastic programming to model uncertain parameters associated with load demand, energy prices, maximum RES generation capacity, and EVs’ parameters. Finally, the potential of the proposed FPM model in improving the economic, operational and flexibility conditions of the MG is investigated through implementation of the proposed model on the 32-bus radial MG.

Optimization of electric spring operational strategy to minimize electricity bill

This paper aims at using electric spring to reduce the monthly electricity bill by developing its optimal operational strategy to capitalize on the variable energy cost over a day. An hourly-sampled optimization algorithm is presented to devise an optimum daily strategy for electric spring as a tool to smartly manage energy among the loads, utility, and storage devices, provided that load and solar power forecasts are available. Uncertainty in forecasts is dealt with by embedding certain stochastic processes with the proposed optimization algorithm to identify an envelope of probable operational strategies. The development and deployment of the proposed optimization algorithm are presented on a realistic load profile of a typical net-zero energy house in South Australia. The obtained results are analyzed under different connection configurations. Consequently, a significant reduction in the monthly electricity bill is realized.

Introduction of degradation modeling in qualification of the novel subsea technology

All-electric systems are the novel subsea technology that is an upgrade of widely deployed electro-hydraulic control systems. They promised more reliable equipment and a safer environment. An all-electric production system performs several functions related to hydrocarbon production control. It also performs safety functions by isolating the reservoir from the environment. Safety functions are performed by activation of safety valves. These safety valves include electric springs in their design instead of mechanical springs. Failure modes and effects analysis of these valves show that interruptions in the power supply appear as random demands to the safety valves, and experiencing such demands may deteriorate their performance. However, the current reliability assessment of safety valves does not consider any degradation phenomena. This paper’s main objective is to investigate the degradation modes caused by demands and their influence on the all-electric actuation system’s performance under different maintenance strategies. A degradation modeling framework based on the multiphase Markov process is proposed. The impact of demand is modeled by changing the initial condition or by increasing the transition rates between two degraded states. The amplitude of the increment depends on the condition at the time of the demand. Analytical formulae are developed for the time-dependent reliability assessment.

Hybrid stochastic/robust flexible and reliable scheduling of secure networked microgrids with electric springs and electric vehicles

Electric spring (ES) as a novel concept in power electronics has been developed for the purpose of dealing with demand-side management. In this paper, to conquer the challenges imposed by intermittent nature of renewable energy sources (RESs) and other uncertainties for constructing a secure modern microgrid (MG), the hybrid distributed operation of ESs and electric vehicles (EVs) parking lot is suggested. The proposed approach is implemented in the context of a hybrid stochastic/robust optimization (HSRO) problem, where the stochastic programming based on unscented transformation (UT) method models the uncertainties associated with load, energy price, RESs, and availability of MG equipment. Also, the bounded uncertainty-based robust optimization (BURO) is employed to model the uncertain parameters of EVs parking lot to achieve the robust potentials of EVs in improving MG indices. In the subsequent stage, the proposed non-linear problem model is converted to linear approximated counterpart to obtain an optimal solution with low calculation time and error. Finally, the proposed power management strategy is analyzed on 32-bus test MG to investigate the hybrid cooperation of ESs and EVs parking lot capabilities in different cases. The numerical results corroborate the efficiency and feasibility of the proposed solution in modifying MG indices.