Guozhen Hu

Bio: Guozhen Hu is an academic researcher from Huazhong University of Science and Technology. The author has contributed to research in topics: Microgrid & Load management. The author has an hindex of 3, co-authored 5 publications receiving 1049 citations.

Smart energy management system for optimal microgrid economic operation

Abstract: This study presents a smart energy management system (SEMS) to optimise the operation of the microgrid. The SEMS consists of power forecasting module, energy storage system (ESS) management module and optimisation module. The characteristic of the photovoltaics (PV) output in different weather conditions has been studied and then a 1-day-ahead power forecasting module is presented. As energy storage needs to be optimised across multiple-time steps, considering the influence of energy price structures, their economics are particularly complex. Therefore the ESS module is applied to determine the optimal operation strategies. Accordingly, multiple-time set points of the storage device, and economic performance of ESS are also evaluated. Smart management of ESS, economic load dispatch and operation optimisation of distributed generation (DG) are simplified into a single-object optimisation problem in the SEMS. Finally, a matrix real-coded genetic algorithm (MRC-GA) optimisation module is described to achieve a practical method for load management, including three different operation policies and produces diagrams of the distributed generators and ESS.

Optimal Allocation and Economic Analysis of Energy Storage System in Microgrids

Abstract: This paper presents a methodology for the optimal allocation and economic analysis of energy storage system (ESS) in microgrids (MGs) on the basis of net present value (NPV). As the performance of an MG strongly depends on the allocation and arrangement of its ESS, optimal allocation methods and economic operation strategies of the ESS devices are required for the MG. To optimize the operation strategies and capacities of ESS in MGs, the financial benefit and dynamic models of ESS are discussed. And then, a matrix real-coded genetic algorithm is applied to find maximal NPV, in which each GA chromosome consists of a 2-D real number matrix representing the generation schedule of ESS and distributed generation sources. This paper is to suggest, among those available ESS, the optimal sizes and types of them and their optimal arrangement, such that the total NPV achieved during the system operational lifetime period is maximized. Finally, some computational simulation results are presented to verify the effectiveness of the proposed method.

Techno-economical analysis of Vanadium redox and Lead-acid batteries in stand-alone photovoltaic systems

Abstract: Sizing and techno-economical analysis of a stand-alone photovoltaic generation system with different energy storage is presented in this paper The method adopted is based on the Loss of power supply probability and levelized cost of energy concepts A new energy storage technology of Vanadium redox battery was applied in photovoltaic power system, which was compared to traditional Lead-acid battery from their physical characteristics and economical efficiency And the mathematical models of photovoltaic, Vanadium redox battery, Lead-acid battery are developed Simulation results show that the techno-economical of Vanadium redox battery was prior and fit for long-term energy storage

Sizing Analysis of PV System with VRB Storage

Abstract: Tiriama nauja vanadžio oksidacijos-redukcijos baterijos energijos kaupimo technologija, taikoma saulės elementų energijos sistemoje. Nagrinėjamas saulės elementų modulio ir vanadžio oksidacijos-redukcijos baterijos talpos tarpusavio sąrysis, lyginant su sistema, kurioje naudojami tradiciniai rūgstiniai svino akumuliatoriai. Pritaikytas metodas pagrįstas energijos saltinio nuostolių tikimybės koncepcija. Siekiant įvertinti siūlomos sistemos nasumą, panaudoti duomenys apie vidutinį Saulės spinduliavimą ir aplinkos temperatūrą centriniame Kinijos regione. Atlikta detali ekonominė analizė naudojant energijos vieneto kainos koncepciją. Matematinis modeliavimas parodė, kad vanadžio oksidacijos-redukcijos baterija gali būti geresnis energijos saltinis ir yra ekonomiskesnė, palyginti su rūgstine svino baterija. Il. 8, bibl. 15, lent. 3 (anglų kalba; santraukos anglų ir lietuvių k.). DOI: http://dx.doi.org/10.5755/j01.eee.118.2.1171

Economic analysis of a regional coordinated microgrids system considering optimal PEVs allocation

Abstract: In this paper, the economic analysis of a regional coordinated Microgrids system (RCMS) considering the allocation model of plug-in electric vehicles (PEVs) is proposed. Such a system is made up of a Residential Microgrid (RMG) and an Industrial Microgrid (IMG), and the two microgrids are already configured with optimized wind turbines and photovoltaic arrays. In this model, the PEVs are served as a mobile energy storage system, purchasing energy from RMG at off-peak times when electricity prices are low, and selling to the IMG when electricity prices are high. To minimize the total cost of RCMS, the optimal number of PEVs is figured out by means of improved particle swarm optimization (IPSO) algorithm. To research the factors affecting optimal PEVs number and cost of the system, the relationship of PEVs charging and discharging price is deeply analyzed. The proposed smart optimal allocation model is tested with case one and case two. The simulation results show that the total cost of the system is effectively reduced adopting the proposed model.

AC-microgrids versus DC-microgrids with distributed energy resources: A review

Abstract: This paper presents the latest comprehensive literature review of AC and DC microgrid (MG) systems in connection with distributed generation (DG) units using renewable energy sources (RESs), energy storage systems (ESS) and loads. A survey on the alternative DG units' configurations in the low voltage AC (LVAC) and DC (LVDC) distribution networks with several applications of microgrid systems in the viewpoint of the current and the future consumer equipments energy market is extensively discussed. Based on the economical, technical and environmental benefits of the renewable energy related DG units, a thorough comparison between the two types of microgrid systems is provided. The paper also investigates the feasibility, control and energy management strategies of the two microgrid systems relying on the most current research works. Finally, the generalized relay tripping currents are derived and the protection strategies in microgrid systems are addressed in detail. From this literature survey, it can be revealed that the AC and DC microgrid systems with multiconverter devices are intrinsically potential for the future energy systems to achieve reliability, efficiency and quality power supply.

DC Microgrids—Part II: A Review of Power Architectures, Applications, and Standardization Issues

Abstract: DC microgrids (MGs) have been gaining a continually increasing interest over the past couple of years both in academia and industry. The advantages of dc distribution when compared to its ac counterpart are well known. The most important ones include higher reliability and efficiency, simpler control and natural interface with renewable energy sources, and electronic loads and energy storage systems. With rapid emergence of these components in modern power systems, the importance of dc in today's society is gradually being brought to a whole new level. A broad class of traditional dc distribution applications, such as traction, telecom, vehicular, and distributed power systems can be classified under dc MG framework and ongoing development, and expansion of the field is largely influenced by concepts used over there. This paper aims first to shed light on the practical design aspects of dc MG technology concerning typical power hardware topologies and their suitability for different emerging smart grid applications. Then, an overview of the state of the art in dc MG protection and grounding is provided. Owing to the fact that there is no zero-current crossing, an arc that appears upon breaking dc current cannot be extinguished naturally, making the protection of dc MGs a challenging problem. In relation with this, a comprehensive overview of protection schemes, which discusses both design of practical protective devices and their integration into overall protection systems, is provided. Closely coupled with protection, conflicting grounding objectives, e.g., minimization of stray current and common-mode voltage, are explained and several practical solutions are presented. Also, standardization efforts for dc systems are addressed. Finally, concluding remarks and important future research directions are pointed out.

State of the Art in Research on Microgrids: A Review

Abstract: The significant benefits associated with microgrids have led to vast efforts to expand their penetration in electric power systems. Although their deployment is rapidly growing, there are still many challenges to efficiently design, control, and operate microgrids when connected to the grid, and also when in islanded mode, where extensive research activities are underway to tackle these issues. It is necessary to have an across-the-board view of the microgrid integration in power systems. This paper presents a review of issues concerning microgrids and provides an account of research in areas related to microgrids, including distributed generation, microgrid value propositions, applications of power electronics, economic issues, microgrid operation and control, microgrid clusters, and protection and communications issues.

Distributed Control to Ensure Proportional Load Sharing and Improve Voltage Regulation in Low-Voltage DC Microgrids

Abstract: DC microgrids are gaining popularity due to high efficiency, high reliability, and easy interconnection of renewable sources as compared to the ac system. Control objectives of dc microgrid are: 1) to ensure equal load sharing (in per unit) among sources; and 2) to maintain low-voltage regulation of the system. Conventional droop controllers are not effective in achieving both the aforementioned objectives simultaneously. Reasons for this are identified to be the error in nominal voltages and load distribution. Though centralized controller achieves these objectives, it requires high-speed communication and offers less reliability due to single point of failure. To address these limitations, this paper proposes a new decentralized controller for dc microgrid. Key advantages are high reliability, low-voltage regulation, and equal load sharing, utilizing low-bandwidth communication. To evaluate the dynamic performance, mathematical model of the scheme is derived. Stability of the system is evaluated by eigenvalue analysis. The effectiveness of the scheme is verified through a detailed simulation study. To confirm the viability of the scheme, experimental studies are carried out on a laboratory prototype developed for this purpose. Controller area network protocol is utilized to achieve communication between the sources.

Distributed Cooperative Control of DC Microgrids

Abstract: A cooperative control paradigm is used to establish a distributed secondary/primary control framework for dc microgrids. The conventional secondary control, that adjusts the voltage set point for the local droop mechanism, is replaced by a voltage regulator and a current regulator. A noise-resilient voltage observer is introduced that uses neighbors’ data to estimate the average voltage across the microgrid. The voltage regulator processes this estimation and generates a voltage correction term to adjust the local voltage set point. This adjustment maintains the microgrid voltage level as desired by the tertiary control. The current regulator compares the local per-unit current of each converter with the neighbors’ and, accordingly, provides a second voltage correction term to synchronize per-unit currents and, thus, provide proportional load sharing. The proposed controller precisely handles the transmission line impedances. The controller on each converter communicates with only its neighbor converters on a communication graph. The graph is a sparse network of communication links spanned across the microgrid to facilitate data exchange. The global dynamic model of the microgrid is derived, and design guidelines are provided to tune the system's dynamic response. A low-voltage dc microgrid prototype is set up, where the controller performance, noise resiliency, link-failure resiliency, and the plug-and-play capability features are successfully verified.