Showing papers on "Stand-alone power system published in 2017"

Classification and assessment of energy storage systems

Abstract: The increasing electricity generation from renewable resources has side effects on power grid systems, because of daily and seasonally intermittent nature of these sources. Additionally, there are fluctuations in the electricity demand during the day, so energy storage system (ESS) can play a vital role to compensate these troubles and seems to be a crucial part of smart grids in the future. This study comparatively presents a widespread and comprehensive description of energy storage systems with detailed classification, features, advantages, environmental impacts, and implementation possibilities with application variations.

Review of commercial thermal energy storage in concentrated solar power plants: Steam vs. molten salts

Abstract: Thermal energy storage systems are key components of concentrating solar power plants in order to offer energy dispatchability to adapt the electricity power production to the curve demand. This paper presents a review of the current commercial thermal energy storage systems used in solar thermal power plants: steam accumulators and molten salts. It describes the mentioned storage concepts and the results of their economic evaluation. The economic value of the TES system is assessed by the Levelized Cost of Electricity (LCOE) calculation, an economic performance metric commonly used in power generation in order to compare cost of electricity among different power generation sources. Lots of studies have been done in the past to compare the LCOE of a complete solar thermal power plant using thermal energy storage systems. However, no specific studies related to the thermal energy storage levelized cost of electricity itself were done. The objective of this study is focused in the comparison of the TES LCOE where calculations are done for a 100 MW Rankine cycle with different plant configuration and for different storage sizes ranging from 1 to 9 h of equivalent full capacity operation.

Cooperation of Wind Power and Battery Storage to Provide Frequency Regulation in Power Markets

Abstract: In the future power system with high penetration of renewables, renewable energy is expected to undertake part of the responsibility for frequency regulation, just as the conventional generators. Wind power and battery storage are complementary in accuracy and durability when providing frequency regulation. Therefore, it would be profitable to combine wind power and battery storage as a physically connected entity or a virtual power plant to provide both energy and frequency regulation in the markets. This paper proposes a real-time cooperation scheme to exploit their complementary characteristics and an optimal bidding strategy for them in joint energy and regulation markets, considering battery cycle life. The proposed cooperation scheme is adopted in a real-time battery operating simulation and then incorporated into the optimal bidding model. The scheme could improve the wind regulation performance score and allow for more regulation bids without affecting the battery life, thus significantly increasing the overall revenue. The validity of the proposed scheme and strategy are proved by the case study.

Performance evaluation of stand alone, grid connected and hybrid renewable energy systems for rural application: A comparative review

Abstract: The energy demand across the globe has increased in many folds due to technological advancement, rapid growth in industries and increase in household energy demand. This led the engineers and planners to think and find the means to harvest the alternative energy sources other than the fossil fuel. Solar, wind, biomass, mini hydro are some of the resources used worldwide to generate energy as per the availability of resources. This paper presents a comparative performances of various stand alone solar photovoltaic(PV), grid connected PV and hybrid renewable energy system (HRES) studied across the globe. The standalone PV system is used to supply electricity to a small habitats/hamlets or to a single household. Hybrid energy system consists of two or more energy sources for generation of power for rural electrification in off grid locations and in grid connected PV systems, excess electricity produced is injected to the grid thereby generating additional income. The research works carried out by various researchers around the globe on renewable energy sources particularly for rural electrification is discussed in this paper. Besides this the utilisation of renewable electricity for Plug-in-Electric Vehicles (PEV) studied across the globe were also discussed.

A review of technical issues on the development of solar photovoltaic systems

Abstract: Today, photovoltaic (PV) plants are receiving a significant attention due to their intrinsic ability to directly transform solar energy in electrical energy. However, electricity generated from PV plants can rarely provide immediate response to load demand, as these sources do not deliver a regular supply immediately compatible with consumers’ needs. Recently, an important attention has been devoted to the use of energy storage in grid-connected PV plants, with the objective of adding flexibility in load management and overcoming some important power quality problems of real distribution grids. This makes PV plants more useful and attractive. Several battery management techniques have been underlying as a way to create more price-responsive demand and as a way to integrate PV plants more effectively into power grid. However, the development of energy policies constraint the wider deployment of PV systems. In this paper, various sizing, modelling, maximum power point tracking (MPPT) methods have been reviewed for the efficient operation of grid-connected PV systems. Dispatch strategies for stored energy that maximize the financial value of battery-PV systems along with several optimization techniques are discussed. Power quality and control technology issues of grid-connected PV systems are also covered. The economic and environmental benefits of grid-connected PV systems are underlined and operational and maintenance issues of PV-battery power systems have been included. The present paper aims at reviewing some technical challenges on the current state of PV systems based on energy policies, various cell technologies, MPPT and converter/inverter technology, energy management and scheduling techniques, reliability, power quality and control systems issues.

DC Grid Voltage Regulation Using New HESS Control Strategy

Abstract: The power generation from renewable power sources is variable in nature, and may contain unacceptable fluctuations in case of the wind power generation. High fluctuations in power generation may negatively impact the voltage stability of the microgrid. This problem can be alleviated by using hybrid energy storage system consisting of batteries and supercapacitors (SCs) at dc grid. A new control scheme is proposed to control the power sharing between batteries and SCs to match the generation-demand mismatch and hence to regulate the grid voltage. In the proposed control strategy, the SC supplies error component of the battery current in addition to the fast transient power demand. This added feature not only improves the dc grid voltage regulation capability but also reduces the stress levels on the battery and hence increases the life span of the battery. The main advantage of the scheme is that, the uncompensated power due to slow dynamics of the battery is diverted to the SC and keeps the state of charge within the limits for longer duration, as compared to the conventional strategy. The proposed scheme is validated through detailed experimental studies.

Active power filter (APF) for mitigation of power quality issues in grid integration of wind and photovoltaic energy conversion system

Abstract: The deep integration of renewable energy resources, including solar photovoltaic (PV) and wind turbine (WT) energy, mainly depend on the inexpensive technological improvement of global emissions and the precise techniques for power quality. Grid-connected inverters act as key components in distributed generation systems for cutting-edge technology. The inverter connects the renewable energy sources and power distribution network systems for the conversion of power. In grid-connected systems, several current and voltage harmonics affect the system performances. Likewise, highly unstable devices coupled with the growing demand for nonlinear loads and renewable energy resources influence the power networks and systems performance in terms of power quality. The effective solutions to these problems are passive filters (PFs), static var generators, and active power filters (APFs). However, the use of PFs in a high-power system increases its cost, size, and weight. This study aims to assess the most advanced APFs by reducing the number of power switches and focus on the reduction of cost, size, and weight of grid-connected inverters. Several studies compared and evaluated reduced-switch-count APF inverter topologies, such as AC–AC, back-to-back, and common leg, under the single-phase and three-phase systems. Recently, cost-effective solutions to reduce the number of components, transformerless inverters, multilevel and multifunctional inverters based on the APF in PV, and wind energy conversion systems have been greatly explored. The current techniques and their limitations for developing advanced inverter-based devices for renewable energy systems are discussed with justifications. Therefore, this review would potentially help industrial researchers improve power quality in PV and WT energies and power distribution network systems.

A Supervisory Power Management System for a Hybrid Microgrid With HESS

Abstract: This paper proposes a supervisory power management system (PMS) for a grid interactive microgrid with a hybrid energy storage system. The key feature of the proposed PMS is reduced number of sensors required to implement the PMS. The PMS considers renewable power variation, grid availability, electricity pricing, and changes in local loads. It can detect the operating mode of system without measuring load currents and powers. A single-phase voltage source converter (VSC) transfers real power between dc grid and utility grid besides offering ancillary services such as harmonic mitigation, reactive power support, and unity power factor at the point of common coupling (PCC). In the proposed system, a better dc-link voltage regulation is achieved and the usage of supercapacitors reduces the current stress on the battery. The PMS also addresses extreme operating conditions such as load shedding, off-maximum power point tracking operation of photovoltaic, elimination of critical oscillation of hybrid energy storage systems power, islanded operation, and resynchronization with grid. The performance of the proposed PMS is verified by digital simulation and experimental studies.

A Sensorless Power Reserve Control Strategy for Two-Stage Grid-Connected PV Systems

Abstract: Due to the still increasing penetration of grid-connected photovoltaic (PV) systems, advanced active power control functionalities have been introduced in grid regulations. A power reserve control, where namely the active power from the PV panels is reserved during operation, is required for grid support. In this paper, a cost-effective solution to realize the power reserve for two-stage grid-connected PV systems is proposed. The proposed solution routinely employs a maximum power point tracking control to estimate the available PV power and a constant power generation (CPG) control to achieve the power reserve. In this method, the solar irradiance and temperature measurements that have been used in conventional power reserve control schemes to estimate the available PV power are not required, and thereby, being a sensorless approach with reduced cost. Experimental tests have been performed on a 3-kW two-stage single-phase grid-connected PV system, where the power reserve control is achieved upon demands.

Delta Power Control Strategy for Multistring Grid-Connected PV Inverters

Abstract: With a still increasing penetration level of grid-connected photovoltaic (PV) systems, more advanced active power control functionalities have been introduced in certain grid regulations. A delta power constraint, where a portion of the active power from the PV panels is reserved during operation, is required for grid support (e.g., during frequency deviation). In this paper, a cost-effective solution to realize delta power control (DPC) for grid-connected PV systems is presented, where the multistring PV inverter configuration is adopted. This control strategy is a combination of maximum power point tracking (MPPT) and constant power generation (CPG) modes. In this control scheme, one PV string operating in the MPPT mode estimates the available power, whereas the other PV strings regulate the total PV power by the CPG control strategy in such a way that the delta power constraint for the entire PV system is achieved. Simulations and experiments have been performed on a 3-kW single-phase grid-connected PV system. The results have confirmed the effectiveness of the proposed DPC strategy, where the power reserve according to the delta power constraint is achieved under several operating conditions.

Decentralized Method for Load Sharing and Power Management in a PV/Battery Hybrid Source Islanded Microgrid

Abstract: This paper proposes a new decentralized power management and load sharing method for a photovoltaic based islanded microgrid consisting of various photovoltaic (PV) units, battery units and hybrid PV/battery units. Unlike the previous methods in the literature, there is no need to communication among the units and the proposed method is not limited to the systems with separate PV and battery units or systems with only one hybrid unit. The proposed method takes into account the available PV power and battery conditions of the units to share the load among them. To cover all possible conditions of the microgrid, the operation of each unit is divided into five states and modified active power-frequency droop functions are used according to operating states. The frequency level is used as trigger for switching between the states. Efficacy of the proposed method under different load, PV generation, and battery conditions is validated experimentally in a microgrid lab prototype consisting of three units.

Stochastic Scheduling of Battery-Based Energy Storage Transportation System With the Penetration of Wind Power

Abstract: Battery-Based Energy Storage Transportation (BEST) is a potential solution for optimizing the power system operations with a high penetration of wind energy. In this paper, we propose a scenario-based stochastic model for the BEST-integrated power system scheduling. In this model, load and wind energy forecasting inaccuracies and random disturbances are modeled in scenario trees using the Monte Carlo simulation method. Random disturbances represent forced outages of both power system and railway system components, including generation units, transmission lines, railway stations, and railway lines. Benders decomposition is adopted to solve the stochastic model. Two BEST-integrated power systems are used to illustrate the proposed model and the performance of the proposed solution algorithm. The first one is a 6-bus power system integrated with a 3-station and 3-line railway network. The second one is the modified IEEE 118-bus power system integrated with a railway network composed of 8 railway stations and 10 rail lines. Simulation results show that the BEST system implementation is a viable option for managing the large-scale integration of wind power which can reduce the curtailment of wind power and accordingly lower the operation cost of power systems.

Grid Adaptive Power Management Strategy for an Integrated Microgrid With Hybrid Energy Storage

Abstract: The penetration of growing microgrid systems within the ac distribution network is leading to several challenges to have a safe and reliable operation of the power system. For the utility system, it is mandatory to maintain the voltage and frequency within the prescribed limits at the local bus under diverse conditions of the renewable energy sources (RESs), loads, and grid. With these conditions, the need for energy storage system (ESS) becomes extremely important for effective operation of critical and frequency sensitive loads. The vital role of ESS based on dc-bus regulation and monitoring of grid frequency in the microgrid is a challenging task and needs to be investigated in detail. Therefore, in this paper, the storage and microgrid are scheduled to work in a grid supportive manner. Also, these ESSs need to be operated within its safe state of charge limits. Hence, based on all the above constraints, an appropriate grid adaptive power management strategy (GA-PMS) is formulated to generate current references for RES, ESS, and microgrid-connected converters. Furthermore, this algorithm includes seamless microgrid operation under abnormal conditions, priority-based load shedding, and ensuring power quality standards at the local bus. The performance of proposed GA-PMS is tested and validated through the simulation and experimental studies.

A Novel Grid-Connected PV System Based on MMC to Get the Maximum Power Under Partial Shading Conditions

Abstract: In the case of partial shading, the output power of the unshaded PV modules will be decreased by the influence of the shaded PV modules in one branch. In order to solve this problem, this paper proposes a novel topology for a PV power generation system by connecting a PV module to the capacitor in each submodule of a modular multilevel converter parallel. As partial shading occurs, the maximum power can be extracted by regulating the capacitor voltage to the maximum power point voltage. With this proposed topology, the maximum power tracking controller, the redundancy module controller, the voltage stability controller, and the grid-connected controller are studied. Simulation and experiment results show that comparing to the traditional topology, the proposed topology can greatly improve the output power of the PV system under the conditions of partial shading and features with low-voltage stress and high efficiency.