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THE UNIVERSITY OF DA NANG UNIVERSITY OF SCIENCE AND TECHNOLOGY TAN NGUYEN VAN RESEARCH AND PROPOSE CONTROL SUGGESTIONS TO IMPROVE THE OPERATION EFFICIENCY OF MICROGRID SYSTEM Specialization : Electrical Engineering Code : 52 02 02 SUMMARY OF DOCTORAL THESIS Da Nang, 2021 This work was completed at UNIVERSITY OF SCIENCE AND TECHNOLOGY – THE UNIVERSITY OF DANANG Science instructor 1: Prof Dr Le Kim Hung Science instructor 2: Assoc Prof Dr Nguyen Huu Hieu Reviewer 1: Reviewer 2: The thesis was defensed at the Engineering Thesis Judging Committee at the University of Technology on ………… 2021 The thesis can be found at: - Learning Resource and Communication Center, University of Technology - National Library of VietNam INTRODUCTION Research motivations: One of the problems facing countries around the world is how to meet the growing demand for energy This increases the demand for energy resources, especially fossil fuels that were initially considered endless However, they have been used to the point of depletion and this has led to negative impacts such as climate change, causing global warming To address global warming, countries are focusing on researching solutions to reduce greenhouse gas emissions, which is to cut fossil fuel use and shift the focus to using more sustainable, environmentally friendly energy sources in power generation However, the use of distributed energy sources (DER) poses a number of challenges arising from their uncertainties (output capacity depends on weather factors ) When the grid has high penetration of renewable energy sources (RES), it will cause an imbalance in capacity,along with related issues of power quality and reliability of the system Currently, Microgrid is the grid structure that is of interest for research as its ability to integrate multiple DER primarily RES has significantly reduced concerns about climate change However, compared to the traditional grid, when Microgrid switched to standalone operation mode, it encounters several challenges: due to the integration of multiple RES, the system has low inertia, the RES depends on weather factors (fluctuations, randomness, and disruption) which makes it difficult to control and balance the capacity in the system, causing frequency fluctuations in the system leading to instability, adversely affecting the quality of electricity Therefore, to improve the operational efficiency of stand-alone Microgrid and make the most of the potential of DER, it is necessary to have appropriate strategies, solutions, and control methods for stand-alone Microgrid On that basis and the context of solar energy sources are currently being developed strongly, the author chooses the research entitled "Research and propose control suggestions to improve the operation efficiency of microgrid system" to propose control suggestions to improve the efficiency of solar energy sources (PV) and other DER sources in Microgrid Research objectives The study proposes control suggestions to optimize microgrid operation Subjects and scope of the thesis Thesis subjects: The study subjects of the thesis are control methods applied to Microgrid Scope of the thesis: The scope of the thesis is to build a model, propose control solutions at the primary control level of stand-alone Microgrid when there are small fluctuations (change in load capacity and of PV system capacity) to improve operational efficiency Microgrid research thesis structure includes diesel generators, solar systems, hybrid storage systems, and load Research methods The research method is a combination of theoretical and experimental mathematical model simulation, research from overview to detail, inheriting the research results that have been published in the world, especially the publications of the thesis authors Scientific and practical significance Scientifically, the thesis has the following contributions: - Proposed MPPT algorithm improvements to improve the efficiency of PV system use - The Hinf sustainability controller proposal applies to HESS's inverse controllers at the primary control level to improve microgrid performance stand-alonely - Propose a descending algorithm based on the HANKEL operator and a balancing method for the controller of the Hinf - sustainable control to reduce the computation and processing time in real-time, to easily applied in practice The results of the thesis will bring the following practical contributions: - Based on control solutions proposed by the thesis, it is possible to apply Microgrid to buildings, industrial zones, isolated islands to maximize the efficiency of RESs - Based on the proposed downgrade algorithm for the controller in the thesis, it is possible to reduce the calculation and processing time of the control systems in Microgrid for easy implementation and practical application Contributions of the thesis The contributions of the thesis are as follows: - Propose an improved MPPT algorithm, applied to PV systems with the configuration requirements of simple MPPT controllers, helping to improve the integration ability of PV systems and operation efficiency of PV systems Microgrid operates stand-alonely - Propose and build a Hinf sustainable controller for the HESS inverter The Hinf Sustainability Controller enhances the operational efficiency of the stand-alone Microgrid - Propose a downgrading algorithm for the Hinf sustainable controller with the control quality equivalent to the full-level Hinf sustainable controller The general layout of the thesis The thesis organizes into four chapters besides the introduction, conclusion, recommendations, list of references, and table of contents The contribution of the thesis presents in Chapter and Chapter Chapter 1: Overview of Microgrid, strategies, and control methods in Microgrid Chapter 2: Modeling and Controlling in Microgrid Chapter 3: Proposing control solutions to improve the operating efficiency of the solar system in Microgrid Chapter 4: Proposing Hinf robust control solutions for HESS to improve the operation efficiency of stand-alone Microgrid CHAPTER OVERVIEW OF MICROGRID, STRATEGIES, AND CONTROL METHODS IN MICROGRID 1.1 Overview of Microgrid The microgrid is defined by Hansen as follows: “Microgrids comprise LV distribution systems with distributed energy resources (DER), flexible loads together with storage devices (flywheels, energy capacitors and batteries …) and these elements are controllable As can be controlled, Microgrid can be operated in either grid-connected mode or stand-alone mode, and it can be switched flexibly between these modes when required.” 1.2 Strategies and control methods in Microgrid To solve the challenges and promote the roles of Microgrid, three management, controlling, and operating Microgrid strategies have been proposed in the thesis as follows: - Centralized control strategy - Distributed control strategy - Hierarchical control strategy 1.3 Control strategies at the primary control level As analyzed above, the switching of Microgrid to stand-alone mode encounters some challenges Therefore, to effectively exploit the RESs and improve the performance of the Microgrid, it is necessary to have appropriate control strategies to control the DERs at the primary level In some studies, control strategies for the primary control levels of Microgrid have been proposed 1.4 Controlling methods In this section, synthesize, analyze and evaluate control methods applied to the primary control level of Microgrid Control methods include traditional PID control, advanced control, adaptive techniques, robust control, and control techniques based on intelligent algorithms such as ANN, FL, PSO algorithm,… 1.5 Structure diagram of research Microgrid The development of distributed solar energy sources integrated into the power grid is increasing in Vietnam and other countries Loads such as buildings, hospitals, airports, factories, and island areas have backup sources using Diesel generators Therefore, the proposal of control solutions to maximize the capacity of distributed solar energy sources, improve the ability to integrate into the grid, and effectively operate Microgrid is of interest From the above analysis, the thesis proposes a research Microgrid structure as shown in Figure 1.15 MBA MBA Phụ tải Máy phát Diesel MGCC MBA MPPT MBA Lưu trữ Pin DC DC DC DC DC AC DC AC Siêu tụ điện DC DC HESS Hệ thống PV Figure 0.15 Microgrid structure 1.6 Comments and conclusions of the chapter Through results on Microgrid in selected references, chapter introduces concepts, operating modes, roles, and problems to operate Microgrid effectively From the problems posed by the Microgrid, this chapter also introduces strategies and control structures for appropriate powersharing between the DERs and ESSs in the Microgrid in gridconnected and stand-alone operation With controlling strategies, the research results refer to analysis, comparison, and evaluation of the controlling methods applied in Microgrid Proposing the Microgrid model is used for the study of the thesis The research results of chapter are published in the 7th research article in the list of the thesis' publications CHAPTER MODELLING AND CONTROLLING IN MICROGRID 2.1 Problem statement In the proposed Microgrid model as shown in Figure 1.15, when Microgrid switches to stand-alone operation, the Diesel generator is the main generator The distributed source using renewable energy is the PV system For stable operation, the thesis proposes to use a hybrid energy storage system (HESS) as the main source of frequency regulation capable of responding to rapid changes of the PV system and load The purpose of this chapter is to build a mathematical model, a Microgrid control structure to simulate, analyze and evaluate the influence of PV system with a high penetration rate, the role of HESS on the operating efficiency of the sources and stand-alone Microgrid 2.2 Modeling and controlling PV systems 2.3 Modelling and controlling Diesel generator 2.4 Modelling and controlling the storage system The Energy Storage System (ESS) integrated into the Microgrid, plays a role in regulating frequency and voltage stability, improving the power quality and reliability of the grid 2.4.1 Overview of the storage system In a Microgrid with a high penetration rate of RES, the requirement of ESS is both to ensure fast power response to changes in renewable sources and loads for frequency stability (stand-alone operation) and to be able to storage to perform the functions as analyzed above (grid-connected operation) Each storage device is not capable of meeting all the requirements, such as energy density, power density, discharge rate, cost, and time As a result, it is necessary to combine two or more types of storage with complementary characteristics to form a hybrid storage system (HESS), to ensure maximum efficiency, and optimize the performance of ESS in Microgrid 2.4.2 Model of converters connecting HESS with Microgrid The energy storage system connects to the Microgrid through power electronic converters shown in Figure 2.17 DC/AC inverter controls the exchange of active and reactive power between HESS and Microgrid A bidirectional DC/DC converter controls the bidirectional current (charge, discharge) of the storage system, and keeps the DC voltage of the DC/AC input stable IHESS ISC DC VSC ISC_DC DC + CDC - DC Siêu tụ điện chiều DSC IDC AC IIA Rf Lf IPCC_A IIB Rf Lf IPCC_B IIC Rf Lf IPCC_C Cf Cf Cf IPin_DC VIA VIB VIC IPin PCC Microgrid DC VPin DC Pin DP Figure 2.17 Structure diagram of HESS connected Microgrid 2.4.2.1 DC/DC bidirectional converter model 2.4.2.2 Model of the inverter (VSI) 2.4.3 HESS controlling methods in Microgrid 2.4.3.1 The second controlling method structure 2.4.3.2 Control Bidirectional DC/DC converter 2.4.3.3 Control Inverter (VSI) 2.5 Microgrid model and frequency control From the alternative circuit models, mathematical equations, and controlling methods built and analyzed above, we have the control model of Microgrid shown in Figure 2.29 DC/DC + - Rf DC AC CDC PCC Lf Lưới điện Cf MPPT Điều khiển HESS VDC_ref DSC Tải VDC DP SC CDC + - Rf DC AC Cf mq md Pin Vòng điều khiển bên HESS Diesel Lf fMG Độ dốc Độ dốc Figure 2.29 Diagram of Microgrid's controlling structure From equations (2.42) and (2.43), we have small signals controlling structure of stand-alone Microgrid as shown in Figure 2.30 Điều khiển sơ cấp Điều khiển độ dốc Tải Ptai Diesel Tdiesel s PDiesel Hệ thống PV PPV_DC TPV s Microgrid P PHESS PPV 2H.s D HESS THESS s fMG Điều khiển sơ cấp Điều khiển độ dốc Figure 2.30 Structure of Microgrid's signal control 2.6 Simulation and results analysis To evaluate the effects of control solutions in Microgrid on operational efficiency, the following simulation will be: Analysis of the influence of MPPT control algorithms on the penetration of PV systems and operational efficiency and frequency stability in Microgrid Analyze the influence of storage system control method on operating efficiency and frequency stability in Microgrid The control system in Figure 4.2 can be described as follows: z w P11 ( s ) P12 ( s ) (4.8) v P( s) v P ( s ) P ( s ) 21 22 u K ( s ).v (4.9) The closed-loop transfer function from w to z is calculated by the following linear transformation: Fl ( P, K ) P11 P12 K ( I P22 K ) 1 P21 (4.10) The aim of Hinf control is to find the controller K(s) that minimizes the infinity standard of the transfer function matrix Fl ( P, K ) , as shown below: (4.11) Fl ( P, K )(s) max ( Fl ( P, K )( j)) However, in most practical applications, it is not necessary to find a globally optimal controller for the Hinf problem but only need to solve simpler suboptimal problems (in terms of arithmetic) be the minimum value of Fl ( P, K )( s ) (global optimal value) Assuming γ > γmin, the suboptimal problem is to find a stable controller K(s) as follow: Fl ( P, K )( s ) (4.12) The above problem is also known as the optimal asymptote problem By decreasing γ, we can give an optimal solution to the Hinf control problem 4.2.3 Weight function in Hinf control problem To solve the above suboptimal problem, there are many controller design methods, one of which is to design a stable control of loop gain through weight functions Therefore, one of the important steps of the Hinf robust controller design is to determine the weight functions These weight functions will help to design the system control quality characteristics according to the desired satisfaction of 16 the quality objective and the objective of stable stability against the changes of input disturbances The desired quality characteristics of the Hinf controller are expressed through weighting functions (frequency filters) on the sensitivity transfer function characteristics 4.2.4 Steps to design and synthesize Hinf controller 4.2.5 Sustainability analysis of the system using M- structure 4.3 Proposing a downgrading algorithm for the controller Hinf 4.3.1 Overview of the principle of downgrading the controller 4.3.2 Proposing a downgrading algorithm for the controller On the basis of the analysis of Hankel standard and the above equilibrium downgrading method, in order to be suitable for the research object, the thesis proposes a downgrading algorithm for a matrix of transfer function [m x n] between n inputs and m output 4.4 Proposing using Hinf robust control method for HESS inverter in Microgried In order to ensure that the stand-alone Microgrid always ensures stable operation with the frequency within the allowable limit when there is a change in the generation and the load source, it is necessary to propose a suitable control method for HESS In this part, the thesis proposes to use the robust control method for HESS inverters in Microgrid and proposes a downgrading algorithm for the Hinf robust controller 4.4.1 Microgrid’s frequency stabilization control structure To improve the operating efficiency of Microgrid, the thesis proposes to apply the Hinf robust control method to the inverter of Microgrid's HESS at the primary control level, with the structure as shown in Figure 4.10 17 VDC_ref Điều khiển HESS VDC DSC SC DC DC DP Pin Pdiesel DP CDC + - Microgrid DC PHESS AC md mq PPV fMG 2H.s D Ptai Pdiesel DC DC fMG Bộ điều khiển bền vững Hinf K(s) Hình 4.10 Model of Microgrid’s frequency stable control structure using robust control for HESS 4.4.2 Building a mathematical model of Microgrid 4.4.3 Hinf robust controller design for inverter Follow the steps below to build a Hinf robust controller for HESS inverters: 4.4.3.1 Building state space model From the system of equations (4.16), we can build a small signal linear state space model as follows: x Ax B1u B2 w y C x D1u D2 w (4.17) 4.4.3.2 Building P-K structure From the state P - P w e space model (4.17) z e and proceed to design e P a Hinf robust controller f =0 m with P-K structure as m v u f shown in Figure 4.11 P The signals in the P-K K(s) structure are defined as K follows: Figure 4.11 P-K control structure applied to Microgrid tải PV Wp1 (s) Wu1 (s) Wu2 (s) diesel * MG d q Mơ hình khơng gian trạng thái tín hiệu nhỏ G(s) 18 -+ MG 4.4.3.3 Determining the weight functions 4.4.3.4 Synthesis of K controller After selecting the appropriate weight functions, the controller K is synthesized (calculation program in Appendix 3) and the corresponding γ (also known as GAM) value is given, GAM = 5,5766.10-6 The transfer function of controller K consists of one input (Input: f MG ) anh two outputs (Output1: md Output2: mq ) 4.4.3.5 Evaluation of the controller based on quality standards The structure of the degenerate value structure (gain of the systematic variable) shows the relationship between the sensitivity function S, KS with the quality weight function W p ( s ) and Wu (s) The sensitivity functions show the relationships of the control system signals as follows: S f MG v w (Ptai PPV ) KS1 md u1 w (Ptai PPV ) mq u2 w (Ptai PPV ) The results from Figure 4.13 and Figure 4.14 show that the histograms of the sensitivity function S, KS1 and KS2 are all below the quality characteristic contours and , which means the K Wu ( s ) W p ( s) KS2 controller Fl ( P, K )( s) always Wp S Wu KS satisfies the condition so the quality of the designed controller is always guaranteed 19 Hình 4.13 Hàm S sai lệch tần số fMG 4.4.3.6 Hình 4.14 Hàm KS sai lệch tín hiệu md mq Evaluating the controller taking into account uncertainties 4.4.4 Synthesis and comparison of downgrading and full-order controllers Using the proposed downgrading algorithm, we proceed to downgrade the controller K with order synthesized above After implementing the proposed downgrading method, the highest order of the transfer function of the controller K is reduced to order 4.4.4.1 Evaluation of the downgrading controller The Hinf robust controller uses the proposed algorithm to downgrade based on the Hankel operator, and the equilibrium downgrade considers the error of amplitude and phase angle of the controller's Bode plot, so firstly we evaluate the Bode plot of the fullorder controllers and lower-order controllers Figure 4.18 and figure 4.19 compare the amplitude and phase angle of the Bode plot of the K1 and K2 controllers when downgrading, full-order From the results, comparing the Bode plot shows that the control quality of the downgrading robust and fullorder controllers is not much different 20 Figure 4.18 Bode plot of controller K1 Figure 4.19 Bode plot of controller K2 Next, from the quality plot of the sensitivity functions S and K S corresponding to the downgrading and full-order controllers are the same and are shown as shown in Figure 4.20 The results show that, after downgrading the K controller, the control quality characteristics of the sensitivity function S and KS are still guaranteed Figure 4.20 Comparing the sensitivity function S when the controller is full-order and downgrading Figure 4.21 Comparing the sensitivity function KS when the controller is full-order and downgrading 4.4.4.2 Evaluating the controller taking into account uncertainties 4.5 Simulation and evaluation of proposed control solutions to the operational efficiency of Microgrid Using the PV system and load scenarios described in Chapter to conduct simulations to evaluate the influence of full order, downgrading Hinf and droop methods applied to HESS to the 21 operational efficiency of Microgrid, then conclude the proposed control solutions in chapter 4.5.1 Full-order Hinf robust controller 4.5.1.1 Scenario of variable PV system and constant load 4.5.1.2 Scenario of constant PV system and variable load 4.5.2 Comparison and evaluation of control solutions In this section, we will compare and evaluate the control methods applied to HESS in the thesis, thereby concluding the proposed solutions to the operational efficiency of Microgrid 4.5.2.1 Scenario of variable PV system and constant load Figure 4.31 shows the results of the frequency response of the Microgrid in the cases when the HESS inverter uses droop control, full-order and downgrading Hinf robust control for the scenario of variable PV system power as shown in Figure 4.25 Similarly, Figure 4.32 shows the results of comparing the voltage VDC of the DC bus of the inverter corresponding to the control methods Figure 4.31 Frequency response of Microgrid Figure 4.32 Voltage VDC of DC bus Figures 4.33 and 4.34 show the results of comparing the power response of Diesel and SC generators with the control methods applied to the HESS inverter 22 Figure 4.34 Power response of SC Figure 4.33 Power response of Diesel Similarly Figure 4.35 shows the results of the battery's power response corresponding to the control methods applied to the HESS inverter Figure 4.35 Power response of battery 4.5.2.2 Scenario of constant PV system and variable load Figure 4.36 shows the frequency response of the Microgrid when the load increases or decreases by 15% For the Hinf control method, the Microgrid frequency changes very little, because the SC storage source can respond quickly and accurately to the change of the load Figure 4.37 Voltage VDC of DC bus Figure 4.36 Frequency response of Microgrid 23 Figure 4.37 shows the result of VDC voltage of the DC busbar corresponding to the control methods applied to the inverter of HESS when the load increases or decreases instantaneously by 15% Figure 4.39 Power response of Figure 4.38 Power response of SC Diesel Similar to the case of variable PV system power scenario, in this scenario, for full-order and downgrading Hinf robust control methods, the HESS is quickly and accurately controlled in response to load changes in the primary frequency control level, so that the Diesel power also not involved in this process, the result of Diesel generator power response is shown in Figure 4.38 The results Figure 4.39 shows with the case of sudden 15% load change similar to the variable PV system power scenario, the power responded by SC in the case of using full order and downgrading Hinf robust control algorithms is greater than in the case using the droop based control method Similarly Figure 4.40 shows the results of the battery power response in HESS corresponding to the control methods Hình 4.40 Power response of battery 4.5.3 Conclusion From the simulation results from Figure 4.25 to Figure 4.40, the following conclusions are drawn: 24 The full-order Hinf robust controller for HESS inverters is designed with control quality that meets the required standards for voltage VDC and frequency stability The Hinf robust controller downgraded according to the proposed downgrading algorithm has the same control quality as the full-order controller The comparison results have shown that the full-order and downgrading Hinf robust control method compared to the droop based control method has advantages such as: voltage VDC of DC bus, Diesel generator power and Microgrid's frequency change is very small compared to using conventional droop method, this enhances Microgrid's operational flexibility, making it easy to switch between Microgrid operating modes from stand-alone to grid-connected and vice versa Thus, from the simulation results, analysis, comparison and evaluation above, it has been shown that the control solutions proposed in Chapter have improved the operational efficiency of Microgrid with the following objectives: Reduce the frequency deviation of Microgrid Reduce the installed capacity of energy storage system Limiting the use of fossil fuels Emission reduction Optimizing the use of renewable energy Enhancing operational stability and reliability of Microgrid 4.6 Comments and conclusions chapter In this chapter, the thesis introduces the theory of robust control based on Hinf Proposing a downgrading algorithm for the stable controller Hinf based on Hankel standard and the equilibrium downgrading method From there, the thesis propose to apply and design a Hinf robust controller for HESS inverters in an stand-alone Microgrid taking into account the effects of uncertainties From the proposed downgrading algorithm, synthesize a downgrading Hinf robust controller for the HESS inverter of in standalone Microgrid Next, conduct simulation to evaluate the quality of control, robust quality of multivariable full-order, downgrading robust 25 controllers with droop method Finally, from the simulation results, the comparative analysis and evaluation conclude the influence of the proposed control solutions in Chapter on the performance of Microgrid Research results of chapter of the thesis are published in works and in the list of publications of the topic 26 CONCLUSIONS AND RECOMMENDATIONS Conclusion Based on the research objectives, the thesis entitled " Research and propose control suggestions to improve the operation efficiency of microgrid system " has completed the contents and made contributions in the field of Microgrid control and operation as follows: - Currently, solar energy systems are being developed very rapidly, providing for many different loads and have a very wide capacity range from a few W to MW Current solar systems mainly use MPPT P&O algorithms to track MPP points Therefore, the improved MPPT algorithm based on the basic output parameters of the PV system which is voltage, current and pulse width D of the power electronic controller of the thesis is simple, with good tracking performance, high MPP point, almost no power fluctuation around MPP point when irradiance changes quickly, slowly and remain constant, equivalent to intelligent MPPT algorithms based on FL, ANN, PSO to help improve system performance PV In addition, the proposed MPPT algorithm helps to increase the integration of PV systems and the operational efficiency of stand-alone Microgrids - Microgrid is a part of smart grid, it is capable of operating in grid-connected, stand-alone mode and flexibly switching between two modes when required Therefore, the proposal and construction of a Hinf robust controller for HESS inverters in the Microgrid of the thesis help to control the exact distribution of power between the sources participating in the dispatching when there is a change in the renewable energy source and the load keeping the frequency of the stand-alone Microgrid always within the allowable limit This makes it easy for Microgrid to flexibly switch between the two operating modes In addition, the Hinf controller helps to improve the operational efficiency of Microgrid when operating in stand-alone mode 27 - The application of controllers in practical systems still accounts for a small proportion because these controllers often have very high order leading to complex hardware, large computation and processing time Proposing a downgrading algorithm for the controller based on Hankel standard and the equilibrium downgrading method of the thesis obtained a controller with control quality equivalent to that of a full-level Hinf controller Therefore, the proposed downgrading algorithm helps to downgrade the controller to make the hardware simpler, reducing the volume, calculation and processing time of the system when applied in practice Recommendation Based on the research results of this thesis, multiple further research directions are proposed as follows: - Research to improve the proposed MPPT algorithm capable of capturing the maximum power point of the PV system that is obscured, shaded - Research and apply a downgrading Hinf based robust controller to control the voltage stability of stand-alone Microgrid - Research on using electric vehicles connected to the grid (V2G) to improve the operating efficiency of Microgrid 28 LISTS OF PUBLICATIONS OF THE THESIS [1] N Van Tan, N B Nam, N H Hieu, L K Hung, M Q Duong, and L H Lam, “A Proposal for an MPPT Algorithm Based on the Fluctuations of the PV Output Power, Output Voltage, and Control Duty Cycle for Improving the Performance of PV Systems in Microgrid,” Energies, vol 13, no 17, p 4326, Aug 2020, (SCI-E) [2] B N Nguyen, V T Nguyen*, M Q Duong, K H Le, H H Nguyen, and A T Doan, “Propose a MPPT Algorithm Based on Thevenin Equivalent Circuit for Improving Photovoltaic System Operation,” Front Energy Res., vol 8, p 14, Feb 2020, (SCI-E) [3] Van Tan Nguyen, Huu Hieu Nguyen, Kim Hung Le and The Khanh Truong, “Expansion of Renewable Energy Capacities in Microgrids using Robust Control Approaches”, GMSARN International Journal, Issue 1, March 2022 (Scopus) [4] Huu Hieu Nguyen, Van Tan Nguyen, Binh Nam Nguyen, Dinh Minh Duc Truong, Huu Dan Dao, Quoc Cuong Le,” The roles of energy storage systems in stabilizing frequency of the islanded microgrid ”, The University of Danang - Journal of Science and Technology, Vol 18, 2020 [5] Van Tan Nguyen, Thi Minh Chau Le, Huu Hieu Nguyen, Le Hong Lam, Anh Vu Nguyen, Ngoc Viet Nguyen, “Evaluating the efficiency of maximum power point tracking algorithms when the solar panels are shaded ”, The University of Danang - Journal of Science and Technology, Vol 18 (No5.2), 2020 [6] Van Tan Nguyen, Duong Hung Hoang, Huu Hieu Nguyen, Kim Hung Le, The Khanh Truong, Quoc Cuong Le, “Analysis of Uncertainties for the Operation and Stability of an Islanded Microgrid”, IEEE, 2019 ICSSE, (Scopus) [7] Van Tan Nguyen, Le Hong Lam, Duong Minh Quan, Nguyen Huu Hieu, Le Kim Hung,”A Thorough Overview of Hierarchical Structure of Microgrid Systems”, IEEE, 2018 4th GTSD, (Scopus) [8] Huu Hieu Nguyen, Van Tan Nguyen, Thi Bich Thanh Truong, Van Thien Son Nguyen, Van Xuan Nguyen, “Application of hybrid renewable energy system in the solar power integration capacity for airport load.” The University of Danang - Journal of Science and Technology, 2021 ... Tdiesel s PDiesel Hệ thống PV PPV_DC TPV s Microgrid P PHESS PPV 2H.s D HESS THESS s fMG Điều khiển sơ cấp Điều khiển độ dốc Figure 2.30 Structure of Microgrid' s signal control... of Microgrid' s controlling structure From equations (2.42) and (2.43), we have small signals controlling structure of stand-alone Microgrid as shown in Figure 2.30 Điều khiển sơ cấp Điều khiển. .. control model of Microgrid shown in Figure 2.29 DC/DC + - Rf DC AC CDC PCC Lf Lưới điện Cf MPPT Điều khiển HESS VDC_ref DSC Tải VDC DP SC CDC + - Rf DC AC Cf mq md Pin Vòng điều khiển bên HESS
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