Input-Series-Output-Parallel DC Transformer Impedance Modeling and Phase Reshaping for Rapid Stabilization of MVDC Distribution Systems

This paper focuses on the instability problem of the medium-voltage DC (MVDC) distribution system and proposes an impedance phase reshaping (IPR) method. To obtain the load impedance model of the MVDC distribution system, the input impedance of the input-series-output-parallel (ISOP) DC transformer (DCT) is derived by the generalized average modeling (GAM). Based on the obtained model, the traditional ISOP DCT controller optimization (IDCO) approach is discussed and the IPR method is developed. An impedance phase controller is introduced based on the original control method. According to the optimized impedance stability criterion, the parameters of the impedance phase controller are determined. Compared with the IDCO approach, the proposed method weakens the negative resistance characteristic of the load impedance at the resonant frequency. Therefore, the MV bus voltage oscillation is rapidly mitigated. Besides, the dynamic performance of the system using the IPR method can be classified as good. The simulation results show that the mathematical model is correct, and the proposed method is effective for the rapid stabilization of MVDC distribution systems.

Download Full-text

Bidirectional Power Sharing for DC Microgrid Enabled by Dual Active Bridge DC-DC Converter

Energies ◽

10.3390/en14020404 ◽

2021 ◽

Vol 14 (2) ◽

pp. 404

Author(s):

Sara J. Ríos ◽

Daniel J. Pagano ◽

Kevin E. Lucas

Keyword(s):

Power Management ◽

Distribution Systems ◽

Control Method ◽

Dynamic Performance ◽

Management Control ◽

Photovoltaic System ◽

Dc Microgrid ◽

Dual Active Bridge ◽

Control Scheme ◽

Bidirectional Power Flow

Currently, high-performance power conversion requirements are of increasing interest in microgrid applications. In fact, isolated bidirectional dc-dc converters are widely used in modern dc distribution systems. The dual active bridge (DAB) dc-dc converter is identified as one of the most promising converter topology for the mentioned applications, due to its benefits of high power density, electrical isolation, bidirectional power flow, zero-voltage switching, and symmetrical structure. This study presents a power management control scheme in order to ensure the power balance of a dc microgrid in stand-alone operation, where the renewable energy source (RES) and the battery energy storage (BES) unit are interfaced by DAB converters. The power management algorithm, as introduced in this work, selects the proper operation of the RES system and BES system, based on load/generation power and state-of-charge of the battery conditions. Moreover, a nonlinear robust control strategy is proposed when the DAB converters are in voltage-mode-control in order to enhance the dynamic performance and robustness of the common dc-bus voltage, in addition to overcoming the instability problems that are caused by constant power loads and the dynamic interactions of power electronic converters. The simulation platform is developed in MATLAB/Simulink, where a photovoltaic system and battery system are selected as the typical RES and BES, respectively. Assessments on the performance of the proposed control scheme are conducted. Comparisons with the other control method are also provided.

Download Full-text

Power Flow Analysis of Weakly Meshed Distribution Network Including DG

Engineering, Technology & Applied Science Research ◽

10.48084/etasr.2277 ◽

2018 ◽

Vol 8 (5) ◽

pp. 3398-3404 ◽

Cited By ~ 2

Author(s):

A. Al-Sakkaf ◽

M. AlMuhaini

Keyword(s):

Power Distribution ◽

Distribution System ◽

Power Flow ◽

Distribution Systems ◽

Flow Analysis ◽

Load Flow ◽

Power Distribution Systems ◽

Power Flow Analysis ◽

Bus Voltage ◽

Flow Study

Power flow is one of the essential studies in power system operation and planning. All steady-state parameters for power distribution systems, such as bus voltage magnitudes, angles, power flows, and power losses, can be calculated by conducting power flow analysis. Distribution system features differ from those of transmission system, rendering conventional load flow algorithms inapplicable. In this paper, three distribution power flow techniques are presented and tested to evaluate their performance when applied to a networked distribution system including distributed generation (DG). These are the distribution load flow (DLF) matrix, the enhanced Newton Raphson (ENR), and the robust decoupled (RD) method. IEEE 33-bus system is adopted for implementing the above methods. Radial and weakly meshed configurations are applied to the tested system with DG inclusion to investigate their influence on the power flow study findings.

Download Full-text

Integration of Photovoltaic Power Units to Power Distribution System through Modular Multilevel Converter

Energies ◽

10.3390/en11102753 ◽

2018 ◽

Vol 11 (10) ◽

pp. 2753 ◽

Cited By ~ 3

Author(s):

Seyed Hakimi ◽

Amin Hajizadeh

Keyword(s):

Power Distribution ◽

Distribution System ◽

Distribution Systems ◽

Sliding Mode ◽

Dynamic Performance ◽

Lyapunov Theory ◽

Modular Multilevel Converter ◽

Multilevel Converter ◽

Power Distribution System ◽

Grid Voltage

With the growing of using photovoltaic (PV) units in power distribution systems, the role of high-performance power electronic converters is increasing. In this paper, modelling and control of Modular Multilevel Converter (MMC) are addressed for grid integration of PV units. Designing a proper controller for MMC is crucial during faulty conditions to make the converter stable and provide proper dynamic performance. To achieve this goal, a dynamic model of MMC is presented which it includes symmetrical components of voltage and current. Then, adaptive robust current controllers are developed based on sliding mode and fuzzy controllers for MMC and then the robustness and stability of the controllers are proved by the Lyapunov theory. To implement the proposed controllers under unbalanced grid voltage fault, positive and negative sequences current controllers are implemented to compensate the effect of grid voltage fault and load power variation. Finally, numerical results are shown to evaluate the performance of MMC. In the end, the experimental results are given to prove the controller performance. The outcome indicates that the proposed current controllers are more effective under voltage disturbance conditions and could satisfy the stability of MMC.

Download Full-text

Optimal Control Strategy for Distributed Energy Resources in a DC Microgrid for Energy Cost Reduction and Voltage Regulation

Energies ◽

10.3390/en14040992 ◽

2021 ◽

Vol 14 (4) ◽

pp. 992

Author(s):

Phi-Hai Trinh ◽

Il-Yop Chung

Keyword(s):

Control Strategy ◽

Distribution System ◽

Distribution Systems ◽

Control Method ◽

Voltage Regulation ◽

Energy Resources ◽

Distributed Energy Resources ◽

Sensitivity Factor ◽

Voltage Sensitivity ◽

Distributed Energy

Distributed energy resources (DERs), including renewable energy resources (RESs) and electric vehicles (EVs), have a significant impact on distribution systems because they can cause bi-directional power flow in the distribution lines. Thus, the voltage regulation and thermal limits of the distribution system to mitigate from the excessive power generation or consumption should be considered. The focus of this study is on a control strategy for DERs in low-voltage DC microgrids to minimize the operating costs and maintain the distribution voltage within the normal range based on intelligent scheduling of the charging and discharging of EVs, and to take advantage of RESs such as photovoltaic (PV) plants. By considering the time-of-use electricity rates, we also propose a 24-h sliding window to mitigate uncertainties in loads and PV plants in which the output is time-varied and the EV arrival cannot be predicted. After obtaining a request from the EV owner, the proposed optimal DER control method satisfies the state-of-charge level for their next journey. We applied the voltage sensitivity factor obtained from a load-flow analysis to effectively maintain voltage profiles for the overall DC distribution system. The performance of the proposed optimal DER control method was evaluated with case studies and by comparison with conventional methods.

Download Full-text

Real-Time Dispatch of Coupled Transmission and Distribution Systems within a Distributed and Cooperative Framework

Energies ◽

10.3390/en13205281 ◽

2020 ◽

Vol 13 (20) ◽

pp. 5281

Author(s):

Lingshu Zhong ◽

Lin Guan

Keyword(s):

Power Control ◽

Real Time ◽

Distribution System ◽

Cooperative Control ◽

Distribution Systems ◽

Control Method ◽

Active Power ◽

Renewable Energy Consumption ◽

Active Power Control ◽

Transmission And Distribution

This paper presents a real-time dispatch strategy for coupled transmission and distribution systems within a distributed and cooperative control framework to maintain reliable and secure operation with minimum generation costs and maximum renewable energy consumption. The presented strategy transforms each distribution system into a dispatchable active source via an average-consensus-based active power control of renewable distributed energy resources (DERs) at the distribution level and then dispatches the active power reference of conventional generators as well as the distribution systems in a measurement-based way at a transmission level. The voltage fluctuation caused by the DER active power control is smoothened with a distributed voltage control method, which can also reduce the active power loss in the distribution systems. Compared to existing real-time dispatch strategies, the proposed strategy can eliminate security issues in the transmission system in a short time by regulating large amounts of DERs at a distribution level in a simple and easy controlled structure, in which the differences in the communication conditions and privacy requirements between the distribution and transmission systems are adequately considered.

Download Full-text

Effective Demand Side Scheme for PHEVs Operation Considering Voltage Stability of Power Distribution Systems

International Journal of Emerging Electric Power Systems ◽

10.1515/ijeeps-2016-0041 ◽

2017 ◽

Vol 18 (2) ◽

Cited By ~ 3

Author(s):

Mamdouh Abdel-Akher ◽

Ahmad Eid ◽

Abdelfatah Ali

Keyword(s):

Control Strategy ◽

Power Distribution ◽

Distribution System ◽

Distribution Systems ◽

Voltage Stability ◽

Fuzzy Logic Controller ◽

Control Method ◽

Stability Index ◽

Input Variables ◽

Network Status

Abstract This paper presents a new technique for a controlled charging/discharging of the PHEV’s battery considering the network status on a real-time basis. A control strategy is developed to secure the operation of power system irrespective of the number of vehicles and their connection place. The proposed control strategy utilizes an improved normalized steady-state voltage stability index that is easy to compute in the distribution management systems. A fuzzy logic controller (FLC) is used for evaluating the battery level of charging/discharging of individual PHEV connected to the distribution network. The controller is a part of the smart charger which uses the battery state of charge and the stability index as input variables. Based on the FLC output, the interface converter of a PHEV decides the desired charging/discharging levels of the battery. The developed controller ensures the secure operation of the distribution system during charging since only empty batteries will have a high priority to charge. A time domain, as well as 24-hour time-series simulations, are used to test the proposed control method. The results show that the developed control method guarantees secure operation, whatever the number and location of PHEVs connected to the studied system.

Download Full-text

Research on Control Method of DC Voltage Based on Power Feedforward

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.380-384.3065 ◽

2013 ◽

Vol 380-384 ◽

pp. 3065-3068

Author(s):

Xin Du ◽

Ling Zhu

Keyword(s):

Control Method ◽

Feedforward Control ◽

Dynamic Performance ◽

Response Speed ◽

Active Power ◽

System Response ◽

Dc Voltage ◽

Dc Bus ◽

Bus Voltage ◽

Grid Side

DC-bus voltage is affected by fluctuations of load and grid impact, threating the safe operation of the system. According to the instantaneous active power balance, a power feedforward control strategy was proposed to reduce the DC voltage fluctuations. In this strategy, the load active power was directly fed-forward to the grid-side given instantaneous active power node through a constructed load state feedforward channel, which avoided the slower process of indirect power adjustment through outer voltage loop. So, the system response speed was greatly accelerated, the DC-bus voltage fluctuation was inhibited effectively, and the dynamic performance of the system had improved. Test results demonstrate the effectiveness of the proposed strategy.

Download Full-text

Enhancing power quality of ANN controller based PhotoVoltaic source injected DVR

International Journal of Engineering & Technology ◽

10.14419/ijet.v7i2.31.13430 ◽

2018 ◽

Vol 7 (2.31) ◽

pp. 155

Author(s):

T Ramesh ◽

S K. Mayurinathan ◽

R Saravanan ◽

G Emayavaramban

Keyword(s):

Distribution System ◽

Distribution Systems ◽

Control Method ◽

Voltage Sag ◽

Voltage Waveform ◽

High Quality ◽

Load Voltage ◽

On Line ◽

Stable Voltage

The DVR is a series connected FACTS controller used to compensate voltage disturbance in distribution systems. The main purpose of the DVR is to examine the load voltage waveform regularly if any disorder happens, the equilibrium or excess voltage is injected to the load voltage. The most important advantage of the DVR is observance the users all the time on-line with high quality stable voltage maintaining the permanence of production. In this dissertation, a Photovoltaic voltage injected with an ANN control method for DVR that protects a sensitive load, to counter voltage sag under uneven loading conditions (linear, non-linear) is presented. DVR along with other parts of the distribution system are simulated using MATLAB/ SIMULINK.

Download Full-text

Study on Dynamic Performance of UPFC Based on PSASP

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.385-386.941 ◽

2013 ◽

Vol 385-386 ◽

pp. 941-944 ◽

Cited By ~ 1

Author(s):

Lin Chuan Li ◽

Ye Fei Chen ◽

Fang Zhang

Keyword(s):

Power Flow ◽

System Analysis ◽

Control Method ◽

Dynamic Performance ◽

Transient Model ◽

Power Flow Control ◽

Power System Analysis ◽

Capacitor Voltage ◽

Bus Voltage ◽

Program Interface

An improved power flow control method of UPFC was proposed with consideration of the dynamic performance of dc capacitor: the line power flow was controlled based on current prediction in the series side, while the bus voltage and the dc capacitor voltage were controlled by the modulation ratio and phase shifting angle, respectively. The transient model of UPFC was established by Power System Analysis Software Package (PSASP) using its User Program Interface (UPI). The simulation results indicate that the model shows a good dynamic performance of UPFC.

Download Full-text