Voltage Control System Research Articles

СИНТЕЗ ДВОКОНТУРНИХ СИСТЕМ КЕРУВАННЯ НАПРУГОЮ РЕВЕРСИВНИХ ПІДВИЩУВАЛЬНИХ DC-DC ПЕРЕТВОРЮВАЧІВ

The paper deals with the design and analysis of cascaded DC-link voltage control systems for bidirectional buck-boost DC-DC converters. Its model is significantly nonlinear and non-minimum-phase, which makes it impossible to achieve high dynamic quality indicators using standard methods of linear control theory. A new method for design and analysis of DC-DC converters control systems based on partial feedback linearization and the subsequent application of linear PI voltage and current controllers is proposed. It provides that the resulting model is composed of the feedback inter-connected linear asymptotically stable subsystems with bilinear properties. The resulting system is linearized in the vicinity of the trajectories corresponding to the power balance equation. Such form allows to apply the theory of cas-caded systems with two time-scale separation of the control loops dynamics. It not only ensures system stability but also allows to specify the process quality indicators using methods available to control engineers. References 14, figures 9.

Fuzzy Multi-Agent Based Voltage and Reactive Power Control

. Variations in load and generation profiles cause overvoltages leading to equipment insulation failure and undervoltages, which impact voltage stability margin. Voltage and reactive power control aims to keep the voltage profiles within desired limits and reduce power losses. In this paper multi-agent system based on Java technology and adaptive fuzzy logics algorithms are implemented to control voltage and reactive power. Agents communicate with each other using Foundation for Intelligent Physical Agents (FIPA) to be able to achieve their objectives. A fuzzy agent controls the voltage at the busbars. Multi-agent systems make it possible to do three hierarchal voltage control in distribution systems.

ATP prediction of voltage sag effect on sensitive loads.

The objective of this paper is to analyze the behavior of adjustable speed drives (ASD) connected to the power system under symmetrical voltage sag conditions. An ATP model has been developed to simulate the response of a VSI inverter driving a three-phase induction motor. Speed and voltage control systems are included. The response of mechanical and electrical variables is obtained.

High-Flexibility DC-Link Voltage Control for Grid-Tied Solar PV Systems: Maximizing Performance and Power Quality

High-Flexibility DC-Link Voltage Control for Grid-Tied Solar PV Systems: Maximizing Performance and Power Quality

Sustainable Power Flow: Voltage Distribution Strategies for Renewable Energy Integration

The rapid expansion of green energy resources (RER) into existing electrical networks necessitates an evolved approach to voltage distribution. This study explores the challenges and solutions associated with integrating green energy into high and low voltage distribution systems (HVDS and LVDS). The research evaluates various protection schemes for dynamic fault currents, voltage control systems for mitigating power quality issues, and optimal planning strategies for distributed generation. Innovative methodologies for integrating solar and wind energy, such as centralized-decentralized control approaches and demand response mechanisms, are proposed. The study demonstrates, through MATLAB simulations, that HVDS configurations significantly improve system efficiency and reduce technical losses compared to LVDS, particularly when interfacing with green energy sources.

Distributed model predictive control based on the alternating directions method of multipliers applied to voltage and frequency control in power systems

AbstractWe present a straightforward way to solve a model predictive control problem for a power network system given as a nonlinear differential‐algebraic equation (DAE) in a distributed way using the consensus alternating directions method of multipliers (consensus ADMM) algorithm. While no convergence‐ or stability results are available for fully nonlinear DAE models, this gives unprecedented experimental evidence that power network systems of the presented structure allow to be controlled in this way, unlocking the numerous combined advantages of distributed and predictive control schemes in the context of energy distribution networks, as well as broadening the field of use for the consensus ADMM algorithm to nonlinear DAE models.

A Novel Energy Management Control Scheme for a Standalone PV System in a DC Nanogrid

Distributed energy resources (DERs), such as photovoltaic (PV) sources, together with storage systems, such as battery energy storage systems (BESS), are increasingly present and necessary in our electricity distribution networks. Furthermore, the need for efficient use of energy from DERs, especially in developing countries and remote communities, must be addressed with the development of nanogrids (NGs), particularly DC NGs, and standalone PV systems with adequate control strategies. This paper investigates the control and dynamic operation of a standalone PV system. It consists mainly of three DC–DC power converters for the PV source interface, battery management, and load voltage control. A two-level modulation scheme is applied to each of these converters to switch them ON and OFF. A maximum power point tracking (MPPT) closed-loop voltage control system is implemented to make sure that the PV operates at optimum power regardless of the irradiance level or temperature, while battery voltage and load-side voltage control are also implemented to indirectly provide the required load power. The control of each of the converters is achieved by deriving their small-signal models using a state-space approach from which various control objectives are implemented. The DC-link is clamped by a BESS which acts as a backup source to provide power to the DC load in the absence of sufficient power from the PV panel. The dynamic operation of the whole system is enhanced by proposing a robust feedforward scheme that improves the response of the system in the presence of disturbances. The models are analyzed and implemented using PLECS, and numerical simulations are performed to validate the developed models and control schemes.

Dynamic Voltage Restorer to Mitigate Voltage Sag/Swell using Black Widow Optimization Technique with FOPID Controller

The efficiency with which electrical equipment use electricity is essential for several reasons. First, superior power quality (PQ) improves efficiency and facilitates peak performance in electronic equipment. This article's goal is to make the advantages of installing a Dynamic Voltage Restorer (DVR) to enhance PQ for energy users clearer. To improve DVR dependability and user friendliness, the suggested technique uses a hysteresis voltage control system that works with variable switching frequency. Simulation findings show that voltage compensation is successful under disturbances when a black widow optimization (BWO) based Factional order proportional derivative (FOPID) controller is used. This paper proposed is to improve PQ using a BWO- FOPID controller and compare the outcomes to those achieved from a previously developed PI controller in a distribution power system using MATLAB.

Collaborative Disturbance Rejection Voltage Control Technology for Distribution Stations under Distributed Resource Coordination

In order to improve the stability of the voltage in the distribution system, a distributed resource coordination-based coordinated anti-interference voltage control technology for distribution stations is proposed. The study analyzes the anti-interference capabilities of different types of renewable energy, energy storage, electric vehicles, and control distributed photovoltaic grid-connected inverters based on the analysis results. The objective function and constraints of voltage control are set. Voltage control is performed by adjusting the photovoltaic inverter and reactive power compensation device. The experimental results show that the proposed method can achieve stable control of system voltage under both photovoltaic output fluctuations and load fluctuations, indicating that its control effect is good.

Super-twisting sliding mode control for neutral point voltage of three-phase four-wire inverter based on SiC/Si hybrid switch

The three-phase four-wire voltage source inverter (3P4W VSI) is widely used in applications like uninterrupted power supply (UPS) and bidirectional onboard charger. The increasing power density demand requires higher switching frequency and lower switching loss. To fulfill the conflicting objectives, two-fold methodology is proposed in this paper: 1) SiC/Si hybrid switches (HyS) together with recently reported gate trigger are reported for the first time in the 3P4W VSI; 2) the natural point voltage is controlled to track a sinusoidal voltage with the frequency equal to 3 times of fundamental frequency in order to achieve higher DC-bus voltage utilization rate, and further reduce the switching loss. The traditional PI controller is very hard to achieve desired performance due to both the nonlinearity and the variant reference of the natural point voltage control system. Thereby, the super-twisting sliding mode control (ST-SMC) is proposed in this paper to achieve desired tracking performance and fast dynamic response. The effectiveness and superiority of the system are verified by both simulation and experiment comparison with the existing methods using a 5 kW prototype.

Power Quality Improvement Using TID based DVR Controller

The effectiveness of power utilized by electronic devices is crucial for various reasons. Firstly, high-quality power results in better efficiency, allowing devices to operate at optimal energy levels. This article aims to clarify the significance of Power Quality by highlighting the benefits of using a Dynamic Voltage Restorer (DVR) to improve power quality for electricity consumers. The proposed method employs a hysteresis voltage control system that operates with variable switching frequency to enhance DVR reliability and ease of operation. Using a Tilt Integral Derivative (TID) controller, a type of fractional order controller similar to the PID controller, voltage compensation under disturbances is achieved with satisfactory results demonstrated via simulation. The primary objective of this project is to mitigate power quality issues such as voltage swell and sag in a distribution power system by enhancing power quality with a TID controller and comparing the results with those obtained from a previously implemented PID controller, using MATLAB software. Keywords: Dynamic Voltage Restorer (DVR), Tilt Integral Derivative controller (TID), Total Harmonic Distortion, MATLAB software.

Deep reinforcement learning based voltage control revisited

AbstractDeep Reinforcement Learning (DRL) has shown promise for voltage control in power systems due to its speed and model‐free nature. However, learning optimal control policies through trial and error on a real grid is infeasible due to the mission‐critical nature of power systems. Instead, DRL agents are typically trained on a simulator, which may not accurately represent the real grid. This discrepancy can lead to suboptimal control policies and raises concerns for power system operators. In this paper, we revisit the problem of RL‐based voltage control and investigate how model inaccuracies affect the performance of the DRL agent. Extensive numerical experiments are conducted to quantify the impact of model inaccuracies on learning outcomes. Specifically, techniques that enable the DRL agent are focused on learning robust policies that can still perform well in the presence of model errors. Furthermore, the impact of the agent's decisions on the overall system loss are analyzed to provide additional insight into the control problem. This work aims to address the concerns of power system operators and make DRL‐based voltage control more practical and reliable.

Stochastic performance evaluation method of wind power DC bus voltage control system

The stochastic fluctuation of DC bus voltage of wind power grid-connected system is related to the safe and stable of power system, and the stochastic performance evaluation is an important means for early warning system. In order to evaluate stochastic performance of control system, this paper proposes a stochastic performance evaluation method based on minimum variance theory. A dual closed loop control model of wind power grid-connected converter DC bus voltage is established, the stochastic performance evaluation indicator is derived by time-series analysis and Diophantine decomposition, and the method to solve the indicator through operation data is given. The effectiveness of the proposed method is verified by FAST-MATLAB co-simulation platform. And the results show that the stochastic performance of the system can be improved by optimizing the parameters of the controller and the DC bus voltage.

Consensus-based Distributed Bus Voltage Control of in DC Microgrid Clusters

This paper proposes a consensus-based voltage control strategy for the bus of a DC microgrid cluster. Firstly, the closed-loop dynamics of a DC microgrid cluster bus voltage control system based on the consensus distributed control architecture is described, taking into full account the information exchange delay among the microgrid subsystems. Secondly, by constructing the Lyapunov-Krasovskii functional, the voltage control system asymptotic stability criteria under parameter uncertainties are rigorously derived, and the corresponding controller design criteria are obtained. Simulation results show that compared with the centralized control schemes, the proposed consensus distributed control method can reduce the average settling time by 24.39% and the average integral of absolute error of aggregate deviations by 23.92%.

Distributed Online Voltage Control With Fast PV Power Fluctuations and Imperfect Communication

Coordinated Volt-Var control methods have demonstrated their techno-economic feasibility in voltage regulation of photovoltaic (PV) rich distribution systems. However, fast fluctuating PV power and imperfect communication networks may significantly challenge the effectiveness of these methods. In this paper, a revised dynamic consensus algorithm is proposed to coordinate distributed inverters for Volt-Var control in real time. With this proposed method, Var saturation and overvoltage issues which tend to occur at downstream buses of PV rich distribution systems are significantly mitigated. To quantitatively analyse the algorithm performance in imperfect communication environments, the information delivery between agents is modelled by stochastic state transition processes among finite numbers of virtual nodes so as to quantitatively depict the random time delay and packet dropout in a discrete way. On this basis, the state transition process of the whole system is further depicted by a series of row-stochastic matrices, and the ergodic theory is used to analytically derive the algorithm tracking error in an imperfect communication environment. Our proposed method can also be extended to more complex applications, where both Var compensation and PV curtailment (or EV dispatch) are available for system voltage control. Simulation results verify the superiority of our method over traditional ones.

Performance of PMU in an electric distribution grid during transients

Abstract PMUs and micro PMUs are an emerging technology that is gaining increasing importance in the monitoring and control of electric distribution grids. Their ability to provide accurate, real-time information on power quality, along with their ability to quickly detect and isolate any problems on the grid, make them a key tool for increasing grid safety and reliability. In terms of research and development, there is a growing interest in developing more advanced and reliable Micro PMUs that can provide more detailed and accurate information about the grid. In addition, there is a growing focus on integrating Micro PMUs with other grid control and monitoring systems, such as frequency and voltage control systems, to achieve greater efficiency in grid management. In this research, a commercial PMU is tested during transient conditions typical of distribution grids such as load insertion and de-insertion and distributed generation. The system involves simulating a grid in a Simulink environment and transforming digital signals into analog signals to be supplied to the PMU. Some indices such as TVE, ROCOF are then used for performance analysis.

Robust numerical solution for assessing corrosion of reinforced concrete structures under external power supply

Impressing current is a popular technique to adjust corrosion behaviors of structures, both in academic investigation and engineering practice. Focusing on the specific problem, this paper presents a robust solution strategy for analyzing corrosion of reinforced concrete structures, under both voltage-controlled and current-controlled power supply. Following fundamental electrochemistry, a nonlinear numerical model incorporating field and global variables is developed, where the ways of considering power supplies with different controlling modes are presented. To tackle the essential global variable to problems under current-controlled power supply, a pseudo discretization method is newly developed to facilitate the highly nonlinear finite element analysis. Given moisture-induced nonuniform concrete resistivity, the moisture field in concrete is also modelled and solved together with the corrosion propagation through a staggered solution scheme. The proposed approach is carefully validated against a variety of reported experiments. Moreover, by directly controlling steel passivation state, the influence of steel depassivation extent on the cathodic protection performance for aging reinforced concrete structures under different saturation degree is numerically investigated for the first time. It is discovered that the protection effectiveness is closely related to the steel depassivation state. It is also revealed that the influence of concrete saturation degree on protection performance in a current-controlled system is generally more complex than that of a voltage-controlled system.

Physics-Shielded Multi-Agent Deep Reinforcement Learning for Safe Active Voltage Control With Photovoltaic/Battery Energy Storage Systems

While many multi-agent deep reinforcement learning (MADRL) algorithms have been implemented for active voltage control (AVC) in power distribution systems, the safety of electrical components involved in the operation of these algorithms are mostly ignored. In this work, a safe MADRL control scheme is proposed to regulate the reactive and active power control of photovoltaics (PVs) to alleviate power congestion and improve voltage quality by coordinating battery energy storage systems (BESSs) and static var compensators (SVCs). Uniquely, the learning algorithm designed in this paper can limit the action of the agent when approaching a dangerous state to ensure the safety of BESSs during the training process, which is realized by developing a multi-agent twin delayed deep deterministic (MATD3) policy gradient algorithm with a physics-based shielding mechanism. Specifically, actions that lead to dangerous states, the state-of-charge (SoC) of BESSs is fully loaded or drained, are replaced by the shielding mechanism with safe actions while maintaining system stability. Furthermore, each PVs node in the power distribution network is treated as an agent under the fact of reactive and active power sensitivities to voltage in the MATD3 algorithm, which is beneficial for improving scalability. Training, testing and comparative results on IEEE 33-bus and 141-bus with real-world data are provided to demonstrate the effectiveness and superiority of the proposed algorithm.

Voltage and active power local PI control of distributed energy resources based on the effective transfer function method

This paper presents the design of local PI regulators to control voltage and active power of the Distributed Energy Resources (DERs) in grid-connected Active Distribution Networks (ADNs). The design is developed based on the proposed Multiple-Input Multiple-Output (MIMO) model of ADN. Firstly, the Relative Gain Array (RGA) matrix is used to address the problem of input–output pairing and to show that the voltage control loops are coupled whereas the active power control loops are decoupled. Subsequently the method of the Effective Open-Loop Transfer Function (EOTF) is used to decompose the multi-loop voltage control system into a set of equivalent Single-Input Single-Output (SISO) loops. Then, each PI regulator is independently designed to fulfill some control objectives dictated by the designer. The proposed design procedure is simple and straightforward. The fixed-parameters PI regulators facilitate the integration of DERs into traditional distribution networks which are usually operated without or with limited communication infrastructure. The simulation results presented for various scenarios of two different ADN confirm that performance objectives and regulation at the desired set-points are achieved in a robust sense.

Strategies for improving ride-through capability of three-terminal HVDC system under AC side fault

This paper considers a three-terminal hybrid DC transmission system in which the rectifier station adopts line-commutated converter (LCC) while the inverter station adopts parallel two-terminal modular multilevel converter (MMC). The focus of this paper is on the improvement of ride-through capability of LCC AC system in the presence of a fault. A strategy for improving the fault ride-through capability based on local information is proposed. First, the mathematical models of different types of converters in a hybrid DC system are established, and the influence of AC faults at the sending end on the DC transmission system is discussed. Second, in the presence of a slight fault on the AC side of LCC, the current margin control is proposed for the load center side MMC2, where the MMC2 maintains the DC port current as the minimum allowable value. Third, if a serious fault on the AC side of LCC causes a significant AC voltage drop, it is proposed that the non-load center terminal MMC1 adopts voltage margin control. In addition, the MMC1 takes over the DC system voltage control so as to maintain MMC2 to absorb minimum power from the DC system, and prevent the load center connected by the MMC2 from removing too many important loads or causing a frequency collapse. Last, a large number of simulation results verify the effectiveness of the proposed methods.