Voltage stability analysis of power distribution networks using multi-agent approach

In this paper, a distributed multi-agent scheme is presented for reactive power management with renewable energy sources (RESs). The multi-agent system (MAS) framework is developed for distribution systems to improve the stability which is mostly dominated by voltage and the agents in this framework coordinate among themselves using online information and energy flow. In this paper, the agents basically perform two tasks- reactive power estimation and necessary control actions. The topology of distribution network is used to estimate the required reactive power for maintaining voltage stability where distributed static synchronous compensators (DSTATCOMs) are used to supply this reactive power. The DSTATCOM is controlled by using a linear quadratic regulator (LQR) controller within the agent framework. The proposed scheme is further compared with the conventional approach to validate the simulation results.

Voltage violations are the main problem faced in distribution networks (DN) with a higher penetration of inverter-based generations (IBG). Active and reactive power control from smart inverters (SI) can mitigate such violations. Optimal power flow (OPF)-based control provides more accurate operating set points for the coordinated operation of SIs. Therefore, this paper presents a three-phase OPF-based control on SI-enriched unbalanced distribution networks. To consider this, first three-phase model using the current injection model (CIM) is developed. Later, the optimal active and reactive power set points for SIs are obtained by solving a quasi-dynamic optimization problem. The uniqueness of the proposed method is that it regulates the voltage at the affected nodes by obtaining the optimal set points for the smart inverter. The OPF is implemented with a mathematical CIM in Pyomo and solved using the Knitro solver. The proposed method is compared with the sensitivity-based Volt-Var Control (VVC), Volt-Watt Control (VWC), and combined VVC and VWC methods. The effectiveness of the proposed method is verified in a European low-voltage and CIGRE medium-voltage distribution network with 100% penetration. The analysis shows that the OPF-based control optimizes with less network loss and can maintain voltage violations with less reactive power support.

In order to meet the high permeability and the access of large scale distributed generation, at present and in the future, active distribution network becomes the trend of smart grid research. This paper introduces the influence of distribution network voltage distribution and stability of distributed energy access based on active distribution network; The reactive power and voltage optimization control method of active power distribution network is summarized from the aspects of optimal voltage regulation measure, voltage regulation measure of power network equipment, reactive power optimal dispatch of power system, and so on. Analysis of the current status of the research, and summarized the existing active distribution network with a distributed power pickup distribution network reactive power and voltage control of the existence of some problems and the insufficiency still some problems that must be solved in the study of reactive power and voltage optimization control of active distribution network are pointed out.

The mathematical relationship between reactive power consumed by DC system and AC voltage on inverter bus is derived under different control modes, respectively.Based on these relationships, a new definition of multi-infeed short circuit ratio (MISCR) is formulated from the power-flow model of PQ decoupled method.The specific influence of different control modes on voltage stability is analyzed.Considering the relationship between MISCR and voltage stability of AC/DC hybrid system, the characteristics of values of new MISCR are derived.Case study of an actual regional power grid validates these characteristics.

As the demand for more efficient and adaptable power distribution systems intensifies, especially in rural areas, innovative solutions like the Capacitor-Coupled Substation with a Controllable Network Transformer (CCS-CNT) are becoming increasingly critical. Traditional power distribution networks, often limited by unidirectional flow capabilities and inflexibility, struggle to meet the complex demands of modern energy systems. The CCS-CNT system offers a transformative approach by enabling bidirectional power flow between high-voltage transmission lines and local distribution networks, a feature that is essential for integrating renewable energy sources and ensuring reliable electrification in underserved regions. This paper presents a detailed mathematical representation of power flow within the CCS-CNT system, emphasizing the control of both active and reactive power through the adjustment of voltage levels and phase angles. A control algorithm is developed to dynamically manage power flow, ensuring optimal performance by minimizing losses and maintaining voltage stability across the network. The proposed CCS-CNT system demonstrates significant potential in enhancing the efficiency and reliability of power distribution, making it particularly suited for rural electrification and other applications where traditional methods fall short. The findings underscore the system's capability to adapt to varying operational conditions, offering a robust solution for modern power distribution challenges.

Multi-faceted sustainability improvement in low voltage power distribution network employing DG and capacitor bank

This paper focuses on the modeling and analysis of different power distribution network (PDN) structures in 3D TSV ICs, including 3D full wave model and equivalent circuit model. In addition, a simplified equivalent circuit model of stacked PDN is proposed to analysis aspects influencing stacked PDN impedance, such as number of ground TSVs, number of TSV pairs and number of stacked layers. Analyses about how these aspects influencing total capacitance, inductance of stacked PDN and causing resonance in PDN self-impedance (Z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> ) are made in detail. What's more, power noise in different stacked PDN structures is calculated and analyzed in time domain to evaluate their power integrity features. Analysis in this paper can offer instructions for the design and analysis of on-chip PDN.

In power grid modernisation, optimal network use is essential to preserving acceptable voltage profiles, boosting voltage stability, reducing power losses, and strengthening system security and dependability. This can be accomplished by strategically placing reactive power compensation devices within transmission and distribution networks, such as capacitor banks, synchronous condensers, flexible alternating current transmission system (FACTS) devices and custom power devices. The optimal location and size of these devices are essential for effective investment, but previous research has mostly concentrated on a variety of methods for this goal, using different indices to evaluate power loss, voltage stability, voltage profile and line loadability. Despite these initiatives, there is still a lack of a thorough analysis of how current indices and methodologies are applied to all varieties of reactive power compensation devices. This paper offers a detailed literature review on the ideal placement and sizing of these devices, encompassing analytical, conventional and hybrid-based techniques. It discusses key objectives such as power loss reduction, voltage deviation (VD) mitigation, voltage stability enhancement and improvements in system reliability and security. Additionally, the paper examines the relevance of reactive power for stakeholders, including transmission system operators (TSOs), distribution system operators (DSOs) and power generating companies, and explores the mathematical modelling of optimal reactive power dispatch (ORPD), considering the impact of renewable energy sources (RESs) and the role of FACTS devices.

Attempts to reduce greenhouse gas emissions are promising with the recent dramatic increase of installed renewable energy sources (RES) capacity. Integration of large intermittent renewable resources affects smart grid systems in several significant ways, such as transient and voltage stability, existing protection scheme, and power leveling and energy balancing. To protect the grid from threats related to these issues, utilities impose rigorous technical requirements, more importantly, focusing on fault ride through requirements and active/reactive power responses following disturbances. This dissertation is aimed at developing and verifying the advanced and algorithmic methods for specification of protection schemes, reactive power capability and power control requirements for interconnection of the RESs to the smart grid systems. The first findings of this dissertation verified that the integration of large RESs become more promising from the energy-saving, and downsizing perspective by introducing a resistive superconducting fault current limiter (SFCL) as a self-healing equipment. The proposed SFCL decreased the activation of the conventional control scheme for the wind power plant (WPP), such as dc braking chopper and fast pitch angle control systems, thereby increased the reliability of the system. A static synchronous compensator (STATCOM) has been proposed to assist with the uninterrupted operation of the doubly-fed induction generators (DFIGs)-based WTs during grid disturbances. The key motivation of this study was to design a new computational intelligence technique based on a multi-objective optimization problem (MOP), for the online coordinated reactive power control between the DFIG and the STATCOM in order to improve the low voltage ride-through (LVRT) capability of the WT during the fault, and to smooth low-frequency oscillations of the active power during the recovery. Furthermore, the application of a three-phase single-stage module-integrated converter (MIC) incorporated into a grid-tied photovoltaic (PV) system was investigated in this dissertation. A new current control scheme based on multivariable PI controller, with a faster dynamic and superior axis decoupling capability compared with the conventional PI control method, was developed and experimentally evaluated for three-phase PV MIC system. Finally, a study was conducted based on the framework of stochastic game theory to enable a power system to dynamically survive concurrent severe multi-failure events, before such failures turn into a full blown cascading failure. This effort provides reliable strategies in the form of insightful guidelines on how to deploy limited budgets for protecting critical components of the smart grid systems.

With the development of science and technology, there has been growing the grid size, the growing demand for electricity and the extent of increasing the electricity market.In this paper, a mathematical morphology and genetic algorithm based dynamic reactive power optimization method for distribution network is proposed.By means of constructing mathematical morphology filter, the binary image composed by allelic genes of chromosome is filtered and the problem that deals with the action times of voltage regulating devices for compensation is turned into filtering problem of discrete binary image.With further automate scheduling, distribution automation and unmanned substation reactive power optimization of distribution line running made an urgent request.Reactive power optimization can improve the voltage passing rate, increasing the reliability of the system, the power quality, and the system runs the security and economy of the perfect combination, very broad application prospects.

Electric distribution systems are going through a major upgrade with increasing penetration of distributed energy resources (DERs) and impacting transmission system operational analysis. Traditionally, the transmission system’s voltage stability margin is computed by performing a continuation power flow (CPF) analysis. In transmission-CPF, loads in distribution systems are aggregated at the transmission-distribution (T&D) interface buses, and the distribution system’s electrical characteristics, like feeder length, increasing penetration of DERs, and associated control, are not considered. The traditional CPF thus considers the distribution network as a purely passive network without active network management and distributed energy resources. In this paper, two integrated T&D CPF methods are implemented using a co-simulation framework that uses individual transmission and distribution solvers. The first method is iteratively-coupled T&D CPF (IC-TDCPF), where the iterative coupling concept forces convergence of boundary variables at T&D PCC (Point of common coupling) at every CPF step. The second method, Loosely Coupled T&D CPF (LC-TDCPF), relaxes the boundary convergence constraints at PCC to achieve faster calculation speed. Moreover, a reduced distribution network equivalent is also developed to enable faster computation of VSM by reducing the number of integrated T&D buses. The developed T&D CPF co-simulation framework uses an open-source platform <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MATPOWER</i> for solving transmission system and open-source software <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OPENDSS</i> for solving distribution system. Three large integrated T&D systems with 4196, 10587, and 12295 buses are developed to demonstrate the impact of DERs, voltage-dependent load models, and distribution network topology on integrated voltage stability margin using the proposed T&D CPF and co-simulation.

Reactive power optimization control is an important part of power grid connection. With the construction of New Power System, a large number of distributed new energy will be built and connected to the Grid. In order to deal with the randomness and volatility of new energy and hidden dangers of high proportion of new energy in Grid, reactive power optimization control of grid connected power supply is an important measure to stabilize the power system. Photovoltaic(PV) inverters have independent reactive power control and output capabilities through decoupling. Based on this, this paper proposes a reactive power and voltage equalization(RVE) control algorithm for inverter groups. Aiming at the phenomenon of poor power quality at the source-load point of common coupling(SLPCC) and large voltage drop difference in PV station, a RVE algorithm based on reactive power and voltage vector relationship of inverter generation nodes and array iteration is proposed, and the operation simulation is performed. The results show that the control strategy can carry out effective reactive power control and voltage equalization to inverter groups.

This paper proposes active and reactive power management based on distributed optimization method that is employed to minimize loss, voltage variation of buses, load shedding and variation of power generation. In this approach, energy efficiency is improved and voltage profile is kept in an acceptable range under different operating conditions of renewable energy resources and loads. Three various power control methods such as (1) active power control (APC), (2) reactive power control (RPC) and (3) simultaneous APC with RPC are implemented by proposed active and reactive power management unit (ARMU). Measurement units collect essential information and send them to ARMU in each bus. ARMU determines the active and reactive power set points of dispatchable DGs and loads and reactive set points of non-dispatchable DGs in each bus. Also ARMU updates set point in less than one second and all controllable units contribute to voltage and power control which is proper for online optimization. Simulation results show the superior performance of this control method to regulate dynamic active and reactive power set points in distribution network.

This paper presents the analysis of power distribution network impedance and loop inductance of irregular parallel-plane structures and multi-slots plane-pair structures by using the plane-pair partial element equivalent circuit method(PPP). The influence of slot area occupancy rate (AOR) on impedance and loop inductance is investigated for various structures. The test structure is designed and fabricated to validate the influence of AOR on impedance and loop inductance of the PDN. The simulation and measurement of the structure impedance are performed up to 10GHz, and the good agreement are obtained between the simulation and the experiment.

This paper proposes a decoupled power control algorithm for grid integration of photovoltaic (PV) systems using quasi-Z-source inverter (qZSI). The proposed controller uses model predictive control (MPC) framework to inject the maximum available power harvested from the PV panels to the grid and also to compensate reactive power required by the grid. Thus, a power electronics interface (PEI) is proposed to integrate the PV panels to the grid and also to work as a reactive power compensator simultaneously. A reliable technique is proposed to regulate the impedance network elements' voltage and current according to the maximum operating point of PV panels and grid voltage/current requirements. The proposed controller features simple structure for practical implementation, fast dynamic response under changing sky condition, and negligible tracking error in steady state condition for decoupled active and reactive power control in a typical distributed generation (DG) systems. The performance of the proposed controller is verified experimentally using dSPACE-DS1007 platform, and the grid-side power quality analysis is provided and evaluated according to IEEE-519 standard.