Stability Of Distributed Systems Research Articles

Multi-terminal Medium Voltage DC Distribution Network Large-signal Stability Analysis

The Brayton-Moser’s mixed potential theory is a popular approach for large-signal stability analysis of DC-based systems with constant power load (CPL). The criterion from the conventional mixed potential theory contains multiple time-varying parameters which are complicated for convenient stability analysis hence the need for simplification. On the other hand, stability analysis of droop-controlled multiple source converter-based DC systems are scarce. Thus, the large-signal stability criterion of a scaled-down droop-controlled multi-terminal MVDC distribution network with CPL using Brayton-Moser’s mixed potential theory was simplified and derived to show that CPL power rating, PI control parameters, droop and damping coefficients have profound effects on the system’s large-signal stability. By way of MATLAB/Simulink simulations, the large-signal stability of the MVDC distribution system was observed to reduce with increase in CPL power rating and source converter droop coefficients as well as increase with increase in proportionate coefficient values and use of optimized unlike non-optimized damping coefficients. Therefore, the droop-controlled MVDC distribution network with optimized PI control parameters, droop and damping coefficients have enhanced dynamic response and large-signal stability margin proving the accuracy and validity of the simplified large-signal stability criterion.

Impact of Energy Storage Devices on the Distribution System Stability with Distributed Generation. (Dept. E.)

Renewable energy sources have environmental and economic advantages, but it causes many fluctuations and severe problems on the power system. One solution to decrease these problems are designing renewable sources as distributed generations (DGs) on the power distribution system. But it is necessary to add energy storage systems (ESS) to the power system to improve the impact of DGs on the power system stability. In this paper, the photovoltaic system (PV) with energy storage devices such as battery or superconducting magnetic energy storage systems (SMES) is added to the power system and analyzed the stability of the system by using the software program, “MATLAB/Simulink®”. The transient stability of the power system is studied based on many factors as maximum rotor speed deviation, the drop-in grid voltage, and the drop in DC voltage of the PV. A different abnormal system states are simulated to show the effect of system configuration on its stability. For validation, a comparative study is implemented. From the results, it is found that the stability of the power system is improved through the adding of the PV system and increased by adding energy storage systems.

Development of Distributed Low Voltage Distribution Remote Monitoring System

Intelligent power distribution monitoring technology is an important technology to improve the intelligence and automation level of the power distribution system. However, because the current power distribution monitoring methods in low-voltage power distribution rooms are not very developed, regular manual inspections and manual data recording are needed, leading to efficiency very low, so the research and development of intelligent distribution monitoring system in low-voltage distribution room is very necessary.This system is mainly composed of intelligent electrical parameter collection terminal, 4G data transmission module, Alibaba Cloud Internet of Things platform, and remote power host computer, and each device can perform effective data communication. The system is assigned to each low-voltage power distribution room for unified management and viewing. The low-voltage power distribution real-time monitoring system can realize the real-time monitoring of transformer parameters and wireless transmission, and control the 4G communication module to receive or send data to the Alibaba Cloud Internet of Things platform. The remote cloud can monitor and query electrical parameters in real time, and can also send control instructions to the intelligent collection terminal. The terminal host receives various data (such as the three-phase voltage and current of the transformer, active and reactive power, power factor, frequency, harmonics, environmental temperature and humidity, etc.) from the data collector in real time and analyzes it. Once the data exceeds The set threshold will cause an alarm to prevent potential safety hazards in the low-voltage power distribution room. The experimental results prove that the system can monitor the working status of various electrical equipment in the power distribution room in real time, accurately and efficiently, thereby ensuring the safety and stability of the entire power distribution system, and has certain research value.

Critical SCADA applications to parallel operation of transformers in railway electrical traction

The article describes the parallel operation of medium voltage (MV) transformers utilized in electric traction substations (ETS), their connection to the national power system (NPS), and the conditions required for the parallel operation of the ETS transformers. Solutions for the optimization of the parallel operation the MV transformers that power the electric railway traction system (ERTS) are discussed. In the case of multiple failure (fault transformers that serve a section) or load increase over the rated power provided by an electric traction substation (ETS), connection to the respective section of the adjacent ETS transformers is required. The parallel coupling of ETS is possible if High Power Transformers ERTS meet all the conditions for parallel operation. This mode of operation ensures the stability of the electricity distribution system for the consumer. SCADA systems can be used for monitoring critical situations and general optimization of electrical power supply of the railway electric traction system.

Achieving Picosecond-Level Phase Stability in Timing Distribution Systems With Xilinx Ultrascale Transceivers

This article discusses the challenges posed on the field-programmable gate array (FPGA) transceivers in terms of phase-determinism requirements for timing distribution at the Large Hadron Collider (LHC) experiments. Having a fixed phase after startups is a major requirement, and the typical phase variations observed in the order of tens of picoseconds after startups while using the state-of-the-art design techniques are no longer sufficient. Each limitation observed in the transmitter and receiver paths of the high-speed transceivers embedded in the Xilinx Ultrascale FPGA family is further investigated and solutions are proposed. Tests in hardware using Xilinx FPGA evaluation boards are presented. In addition to a higher phase determinism, the techniques presented make it possible to fine-tune the skew of a link with a picosecond resolution, greatly simplifying clock-domain crossing inside the FPGAs and providing better short-term stability for the FPGA-recovered clock in a high-speed link.

Reduction of Line Losses and Enhancement of Voltage Stability in a Radial Distribution System with Renewable Distributed Generation

Reduction of Line Losses and Enhancement of Voltage Stability in a Radial Distribution System with Renewable Distributed Generation - written by Martha Mbenge Kyule , Moses Peter Musau , Nicodemus Odero Abungu published on 2019/11/21 download full article with reference data and citations

Step-by-step Small-Signal Modeling and Control of a Light Hybrid Electric Vehicle Propulsion System

This paper develops step-by-step a complete electric model of a light hybrid electric vehicle propulsion system. This model includes the vehicle mass, the radius and mass of the wheels, the aerodynamic profile of the vehicle, the electric motor and the motor drive, among other elements. Each element of the model is represented by a set of equations, which lead to getting an equivalent electric circuit. Based on this model, the outer and inner loop compensators of the motor drive control circuit are designed to provide stability and a fast dynamic response to the system. To achieve this, the steady-state equations and the small-signal model of the equivalent electric circuit are also obtained. Furthermore, as these elements are the main load of the power distribution system of the fully electric and light hybrid electric vehicle, the input impedance model of the set composed of the input filter, the motor drive, the motor, and the vehicle is presented. This input impedance is especially useful to get the system stability of the entire power distribution system.

A robust SMES control for enhancing stability of distribution systems fed from intermittent wind power generation

The voltage and frequency stability issues of power systems are the main challenges that arise from high penetration levels of wind energy systems. This paper presents an effective solution for voltage and frequency stability problems by using a superconducting magnetic energy storage (SMES) system controlled with a fuzzy logic controller (FLC). The proposed control system can suppress the voltage and frequency fluctuations due to the high variations of wind speed. In addition, the proposed control system is suitable for both balanced and unbalanced distribution systems with high penetration levels of wind turbines (WTs). A squirrel cage induction generator (SCIG) is selected in the case study, which represents the worst scenario of WT generation from the voltage and frequency stability aspects. This is due to the high reactive power consumed by the SCIG from the utility grid during steady state and voltage fluctuations that may lead to harmful consequences for power system components. The proposed control method is validated using the IEEE 33-bus radial distribution network (RDN), wherein the SMES and WT systems are connected to the weakest points of the RDN. The obtained results demonstrate the superior performance of the proposed FLC-SMES system for alleviating the voltage and frequency fluctuations of the distribution power system during high variations of wind power.

Distributed adaptive vibration control for solar power satellite during on-orbit assembly

The distributed adaptive vibration control for solar power satellite (SPS) during on-orbit assembly is investigated in this paper. Focusing on the platform configuration SPS, the different control units (CUs) and relationship matrices, that describe the topology of whole SPS structure, are firstly defined, and the dynamic model of the CU is proposed through the relationship between the CU and the whole SPS structure. Using the linear quadratic optimal control technique, the adaptive controller of the CU is designed to suppress vibrations, and a compensatory component is included in the controller to deal with the interactions with the whole structure. The closed-loop distributed control system is then developed in the presence of the impact at the specific assembling location, which needs to adaptively update along with the varying dynamic model of the SPS structure during on-orbit assembly. The asymptotic stability of the closed-loop distributed system is investigated, and two representative numerical cases are finally provided. The results demonstrate that the proposed distributed adaptive controllers can significantly suppress the vibration caused by the impact among SPS modules during on-orbit assembly.

Solid-State Transformers for Distribution Systems–Part I: Technology and Construction

Solid-state transformers (SSTs) are an emerging technology that has been developed to improve the stability, reliability, and economic operation of distribution systems. These new transformers are composed of a medium ac voltage (MV) stage, a dc stage, and a low ac voltage (LV) stage. Passive and active dc links are used to construct the dc stage in SSTs in order to offer new functionalities, including hybrid (ac and dc) distribution, reactive power compensation, voltage/frequency regulation, power quality improvement, and distributed generation utilization. On one hand, a distribution SST has its ac stage connected to an MV level, which mandates specific power electronic converter (PEC) topologies, switching element capabilities, and filtering circuits. On the other hand, the dc-link stage has to provide isolation between the MV and LV levels, which requires the employment of isolated dc PECs. Part I of this work provides a review of SST designs and constructions (for deployment in distribution systems), in terms of the required technology, supported functionalities, and construction features.

Investigation and Enhancement of Stability in Grid-Connected Active DC Distribution Systems With High Penetration Level of Dynamic Loads

Nowadays, grid-connected active dc distribution systems are gaining widespread acceptance due to the remarkable development of the dc technology, high penetration levels of dc loads, and the market availability of dc-based distributed generators. One of the main features of dc systems is the elimination of multiple conversion stages required for variable frequency ac loads, such as variable-speed drive applications; therefore, dc distribution systems are considered as an efficient and cost-effective choice for supplying such dynamic loads. Induction motors (IMs) equipped with open-loop constant voltage/frequency $(V/f)$ variable speed drives are considered as the workforce for many industrial loads due to their simplicity and satisfactory dynamic performance. However, $V/f$ IM drives exhibit poor stability dynamics, particularly, at low-speed operation, which might negatively interact with the dc distribution system, leading to further stability degradation. Therefore, this paper investigates the interaction dynamics and the performance of a grid-connected dc distribution system with a high penetration level of dynamic loads. A detailed small-signal model of the entire system is developed to characterize the overall system stability margins with the help of the eigenvalues and impedance-based analysis. Moreover, the uncertainties affecting the marginal stability such as motor operating speed, dc feeder length, and bus capacitance, are thoroughly addressed. It has been found that the dynamic loads in grid-connected dc distribution systems would exhibit instability issues due to various dynamic interactions; therefore, two different stabilizing compensation methods are proposed to mitigate the associating instability issues and enhance the system damping capability. Detailed time-domain non-linear simulations and experimental results are presented to validate the analytical results.

Probabilistic assessment of static voltage stability in distribution systems considering wind generation using catastrophe theory

With increasing penetration of distributed generations, the importance of the voltage stability assessment of distribution networks has been increased. Considering this situation, a probabilistic model is proposed to evaluate the voltage stability of distribution network integrating wind turbine (WT) units. With this intention, a probabilistic voltage stability index (PVSI) of a radial distribution system with wind power generation is presented. This index investigates the probabilistic risk of voltage collapse for all the buses of system considering uncertainty of WTs. Therefore, the most sensitive bus to the voltage collapse can be identified. The problem model is based on the catastrophe theory that can find the bifurcation point of system. Three-point estimation method is employed to calculate the statistical moments of voltage and PVSI of nodes. Moreover, to estimate the cumulative distribution function of output random variables, the Cornish−Fisher series are used. The performance of the probabilistic index is tested on the IEEE 69-bus radial distribution system where different load models are considered. The results demonstrate that the PVSI can accurately predict the voltage instability condition of the system.

An OLTC-inverter coordinated voltage regulation method for distribution network with high penetration of PV generations

The voltage fluctuation caused by the photovoltaic distributed generations (PVDGs) threatens distribution system stability. In a multiple feeder distribution network, the voltage fluctuation trends in different feeders will be varied because of the different types and capacities of distribution generators. In this paper, an on-load tap changer (OLTC) & inverter coordinated regulation method is proposed. The fuzzy controller is implemented to coordinate the OLTC and power allocation optimization (PAO) Module. The PAO Module coordinates all inverters on a feeder to maintain terminal voltage of this feeder in rated range while maximizing the active power output of the inverters. By means of the state estimation, the fuzzy logic gathers voltage information from different feeder terminals, to decide whether to maintain voltage stability via adjusting OLTC or PAOs. Thus, the efficiency of PV generations can be improved greatly. A typical distribution network with high penetration of PV distributed generations is built to validate the results.

Output-Feedback Cooperative Formation Maneuvering of Autonomous Surface Vehicles With Connectivity Preservation and Collision Avoidance.

In this paper, a cooperative time-varying formation maneuvering problem with connectivity preservation and collision avoidance is investigated for a fleet of autonomous surface vehicles (ASVs) with position-heading measurements. Each vehicle is subject to unknown kinetics induced by internal model uncertainty and external disturbances. At first, a nonlinear state observer is used to recover the unmeasured linear velocity and yaw rate as well as unknown uncertainty and disturbances. Then, observer-based cooperative time-varying formation maneuvering control laws are designed based on artificial potential functions, nonlinear tracking differentiators, and a backstepping technique. The stability of closed-loop distributed formation control system is analyzed based on input-to-state stability and cascade stability. The salient features of the proposed method are as follows. First, cooperative time-varying formation maneuvering with the capability of connectivity preservation and collision avoidance can be achieved in the absence of velocity measurements. Second, the complexity of the cooperative time-varying formation maneuvering control laws is reduced without resorting to dynamic surface control. Third, the uncertainty and disturbance are actively rejected in the presence of position-heading measurements. Simulation results are given to substantiate the proposed output feedback control method for cooperative time-varying formation maneuvering of ASVs with connectivity preservation and collision avoidance.

Adaptive Droop Based Virtual Slack Control of Multiple DGs in Practical DC Distribution System to Improve Voltage Profile

This paper proposes an adaptive droop based virtual slack (ADVS) control for multiple distributed generations (DGs) to improve voltage stability of a practical DC distribution system. Although there have been many researches for optimal sizes of multiple DGs, their solutions are valid only in the particular operating point. Additionally, a previous study proposed a voltage control based optimal operation method, its performance depends on measurement accuracy in practice. The proposed ADVS control operates the system based on the current sensitivities between the DGs and loads, so that it can regulate the system voltages without a large computational effort. This is effective even if measurements are noisy and biased. All DGs contribute to voltage regulation by current control even though they do not directly control voltages. As an additional effect, they effectively share the load. To verify the proposed method, the DC system is modeled based on the real distribution system of the Do-gok area in Seoul, Korea. Then, the Levenberg-Marquardt algorithm determines its operation point. The proposed method is verified based on the electromagnetic transient (EMT) simulation with random loads.

Dynamic voltage stability of unbalanced distribution system with high penetration of single‐phase PV units

Dynamic voltage instability (DVI) issues are the primary concern in low-voltage distribution network (DN) due to growing integration of low-inertia compressor motor loads such as air-conditioner and refrigerator. The concern of DVI is likely to increase owing to high penetration of rooftop type single-phase photovoltaic (PV) units in DN. On the other hand, DNs are inherently unbalanced as a result of load and line characteristics along with unbalanced PV penetration. This paper examines the impact of imbalance on the dynamic voltage stability (DVS) in DN and provides solutions to mitigate any adverse effects. Dynamic models of the single-phase PV units are developed and utilised in the paper. The degree of unbalanced is defined first, and then its impact on the DVS is investigated. From the investigation, it is observed that degree of instability is increased with the increment of imbalance. The paper has also proposed a mitigation strategy i.e. reactive power injection by PV inverter. Case studies are conducted on modified IEEE 4 bus system which represents a low-voltage DN. Results reveal that reactive power injection by PV inverter can improve the DVS by mitigating the impact of unbalance.

A novel method: using an adenosine triphosphate (ATP) luminescence-based assay to rapidly assess the biological stability of drinking water.

The rapid and credible evaluations of the microbial stability of a drinking water distribution system (DWDS) are of great significance for ensuring the safety of drinking water and predicting microbial pollution. Conventional biostability assessment methods mainly focus on bacterial regrowth or evaluation of the level of nutrients that support bacterial regrowth. However, such methods are time-consuming and have many limitations. An adenosine triphosphate (ATP) assay can rapidly measure all active microorganisms and is known to be a useful method to assess the microbial activity of drinking water. The measurement of ATP has been used for more than a decade in the field of drinking water research. This article reviews the application of an ATP luminescence-based method to assess the biostability of drinking water and discusses the feasibility of ATP measurement as a parameter for quickly evaluating this criterion. ATP measurement will help researchers and water managers better monitor the biological stability of drinking water from the source to the consumer's tap. This review covers the: (1) principle and application of the ATP measurement in drinking water quality assessment; (2) comparison of the merits and demerits of several methods for evaluating the biostability of drinking water; (3) discussions on using ATP measurement in evaluating biostability; and (4) improvements in the use of ATP measurement in evaluating biostability. At the end of this review, recommendations were given for better application of the ATP measurement as a parameter for monitoring the microbial quality of drinking water.

Optimal Allocation of Renewable Distributed Generation and Capacitor Banks in Distribution Systems using Salp Swarm Algorithm

Recent advances in power generation technologies using renewable energy resources, changes in utility infrastructure and government policies tend to increase the interest in a renewable-based distributed generation units (DGs) in a distribution system. To obtain reduced power loss, voltage deviation and improved bus voltage stability in distribution systems, it is mandatory to control optimal power flow of both active and reactive power. Therefore, optimal allocation of DGs and CBs plays a vital role in distribution systems performance enhancement. Where optimal allocation of DGs reduce active power loss and optimal allocation of capacitor banks (CBs) improve bus voltages. This paper proposes a salp swarm algorithm (SSA) for optimal allocation of DGs and CBs. The main aim of the proposed algorithm is to attain technical, economic and environmental benefits. The proposed algorithm is based on the salps swarming behavior in oceans when navigating and foraging. To assess the performance of the proposed SSA three different cases considered: optimal allocation of only DGs, only CBs and simultaneous DGs and CBs. The proposed algorithm is tested on IEEE 33 and 69 bus radial distribution systems. The simulated results illustrate the efficiency of the proposed algorithm when compared to other existing optimization algorithms. Also, the proposed algorithm has achieved technical benefits of reduced power loss, voltage deviation, and improved bus voltage stability, the economic benefit of reduced total electrical energy cost and environmental benefit of reduced emissions.

Power Loss Minimization and Reliability Enhancement in Active Distribution Networks Considering RES Uncertainty

Renewable energy sources (RES) has been growing continuously and most probably have been included in distribution networks. RES intermittent nature of electricity production due to the dependency on external conditions which are changing seasonally. The uncertainty of their power production causes negative impacts on voltage profile and increasing the power losses. This paper proposes a novel technique based on hybrid optimization methods to determine the optimum power of the uncertain power sources and the optimum network configuration to minimize the power losses and maintain the voltage profile under normal and shading conditions. The proposed hybrid algorithm utilizes a Genetic algorithm (GA) combined with particle swarm optimization (PSO) to overcome the uncertainty and optimize the configuration of the networks. Considering different normal and shading operation conditions of RES, the proposed model has been tested on standard IEEE 33 and 66 bus systems and validated with other conventional methods to verify the correctness of the operation and compare the performance and effectiveness. Results obtained show a significant improvement in voltage profile, reduction of power losses, and hence increasing the overall distribution system stability.

APPLICATION OF FINANCIAL INCLUSIONS IN INDONESIA: A STUDY ON VULNERABLE GROUP

Financial inclusion refers to all efforts aimed at eliminating all forms of price and non-price barriers to people’s access to financial services. Financial inclusion is a national development strategy and an influential agenda. The aims of this research are to examine any informal norms or limitations that affect the realization of financial inclusion. Regulative, normative, procedural, and declarative cognition as relaxed norms are thought to influence the implementation of financial inclusion, especially for vulnerable groups. Financial inclusion aims to encourage economic growth through income distribution, poverty alleviation, and financial system stability. This strategy is targeted at groups experiencing obstacles in accessing financial services, especially groups with the greatest needs and financial services that have not been fulfilled, such as poor people and vulnerable groups, in four different locations in Indonesia. As a result of testing several financial inclusion instruments for 254 respondents in this group, it was found that users of financial institution services, both men and women, had similar roles and needs; though government regulation through normative aspects has a positive effect, the procedural elements hurt financial inclusion. Moreover, government regulation through declarative cognitive aspects (the ability to use the dimensions of memory and cognitive skills) has a positive effect on financial inclusion.