Voltage Control Technique Research Articles

Performance Analysis of Buck-Boost and SEPIC Converter for Commutation Torque Ripple Minimization in BLDC Motors

This paper discusses comparative analysis of Buck-Boost and SEPIC (Single Ended Primary Inductance) converters used in DC link voltage control technique to reduce torque ripple in Brushless Direct Current Motors (BLDCM). The aim of this study is to prove the efficiency of the aforementioned two converters, which have been adopted in many studies to reduce torque ripples caused by commutation, on the same motor parameters. Although BLDCM has many advantages, ripples in the generated torque have limited the use of these motors in applications requiring precise speed and torque. In this study, BLDCM was analyzed exhaustive mathematically and electrically and the problem that caused commutation torque ripples was explained in detail. The DC link voltage control has been proposed to suppressing torque ripples in the BLDCM. In addition, the link voltages required for reducing the torque ripples were obtained separately via both the Buck-Boost and the SEPIC converters. These converter topologies are examined under certain speed and torque conditions and the results were compared. When the results are evaluated together, it was observed that both converters performed the very closely performance each other. However, the Buck-Boost converter produced the desired voltage levels with less oscillation than the SEPIC converter.

Toward the Optimization of a PMSG Wind Energy Conversion System On-Grid by a Robust Mixed Controller

The grid interconnected Wind Energy Conversion System (WECS) remains a major challenge. To deal with the effect of the intermittent nature of wind speed. This paper presents the design of a combined nonlinear controller based on a sliding mode controller (MSMC) for a wind system. This control technique includes a smooth switching sliding mode observer (SS-SMO) and a non-singular terminal sliding mode controller (NT-SMC). The SS-SMO is used to observe the torque/speed disturbances, while the NT-SMC is used as a regulator. A voltage control technique is adopted to maintain the voltage at the common DC-link. To control the electrical power injected into the grid a Backstepping controller is proposed. The WECS is built around a wind turbine coupled to a Permanent Magnet Synchronous Generator (PMSG). The proposed technique is robust against model uncertainties and external disturbances. In addition, the complexity of the system is reduced by replacing the mechanical speed and position sensors with the estimated parameter. The simulations results show the performances in terms of monitoring of set point, stability, and robustness with respect to the variation of wind speed.

Optimised coordinated control of hybrid AC/DC microgrids along PV-wind-battery: a hybrid based model

This work presents a novel coordinated control approach for an MG with hybrid AC/DC loads and energy resources. As a result, power interactions between the DC and AC subgrids are appropriately enabled by distributing power fluctuations in a coordinated manner. Initially, a coordinated control scheme of distributed converters was presented. Then, a model predictive power and voltage control (MPPVC) technique is used for DC/AC interlinking converter that offers high-quality voltages and guarantees the optimal power transfer amongst ac and dc sub-grids. This paper aims to enhance the control structure of the energy storage system (ESS), where the optimised PI controller is insisted. Particularly, the gain of PI controller is optimally tuned by a new hybrid algorithm named as index-based fly-rider combined model (IF-RM) that incorporates both the concepts of rider optimisation algorithm (ROA) and firefly algorithm (FF). Finally, the betterment of the proposed work was validated over other existing models.

Sensorless DC-link voltage regulation strategy for single-phase grid-connected solar photovoltaic systems

A sensorless DC-link voltage control technique is proposed for a two stage, single-phase grid-connected solar photovoltaic (PV) system. The developed control strategy is predicated on the fact that if PV power is directly fed into the grid, the DC link voltage would stabilise. However, losses must be properly compensated to maintain a flat DC-link voltage profile. To account for the system losses, teaching-learning-based optimisation (TLBO) is used offline. After the offline implementation, a regression model based on maximum power is built to estimate system losses. The regression model is applied to the system to predictively compensate for system losses. As a result, the DC link control loop is avoided, and sensorless control is achieved. A unit-template-based control is used to synchronise the PV system with the grid. Simulation experiments using MATLAB/Simulink are used to verify the superiority of the proposed scheme over the conventional sensor-based technique.

Ant colony optimization algorithm and fuzzy logic for switched reluctance generator control

<abstract> <p>This article discusses two methods to control the output voltage of switched reluctance generators (SRGs) used in wind generator systems. To reduce the ripple of the SRG output voltage, a closed-loop voltage control technique has been designed. In the first method, a proportional-integral (PI) controller is used. The parameters of the PI controller are tuned based on the voltage variation. The SRG is generally characterized by strong nonlinearities. However, finding appropriate values for the PI controller is not an easy task. To overcome this problem and simplify the process of tuning the PI controller parameters, a solution based on the ant colony optimization algorithm (ACO) was developed. To settle the PI parameters, several cost functions are used in the implementation of the ACO algorithm. To control the SRG output voltage, a second method was developed based on the fuzzy logic controller. Unlike several previous works, the proposed methods, ACO and fuzzy logic control, are easy to implement and can solve numerous optimization problems. To check the best approach, a comparison between the two methods was performed. Finally, to show the effectiveness of this study, we present examples of simulations that entail the use of a three-phase SRG with a 12/8 structure and SIMULINK tools.</p> </abstract>

Application of the Voltage Control Technique and MPPT of Stand-alone PV System with Storage

Application of the Voltage Control Technique and MPPT of Stand-alone PV System with Storage

Application of Energy-Saving for an inverter feeds three-phase induction motor

Three-phase induction motors are the most prevalent AC motors used in many applications. Operation of these motors at load power less than that of the motor full-load power leads to significant power losses and reduces the motor’s efficiency. To mitigate these losses and increase the efficiency of the three-phase induction motors at light loading conditions, energy-saving techniques should be utilized. This paper investigates a voltage control technique applied to light-loaded induction motors to save the energy using an inverter. The light load selected in this paper is a fan load of power load less than the motor full load power. Theoretical analysis, computed characteristics, and experimental verifications are presented to show the effectiveness of the proposed energy-saving technique.

Intelligent voltage regulator for distributed generation-based network

Power grids are being transformed into a smart distribution network that incorporates multiple distributed energy resources (DERs), ensuring stable operation and improved power quality at the same time. Many research papers have been published in recent years that discuss the voltage violation issues that emerge from the high penetration of distributed generation (DG). In this paper, we propose a new optimal voltage control technique based on feedforward neural networks (FFNN) to maintain a stable voltage profile. MATLAB®/Simulink® has been used to carry out the simulation. The simulation results show the efficiency of this method in voltage control. The proposed approach ensured a stable voltage profile for the considered schemes.

Parallel Hybrid Converter-Based STATCOM and Capacitor Voltage Control Technique

The parallel-hybrid converter (PHC) is a promising high-power topology. Smaller capacitor size, lower capacitor and switch counts, and low-energy storage requirement are some of its important features. However, it requires a large dc-filter inductor to filter the dc-side harmonics. Moreover, since its dc and ac sides are strongly coupled, only a single stable operating point in terms of a fixed modulation-index (MI) value is possible. Even with an additional dedicated control effort, the obtained MI variation remains still limited. This article proposes the PHC-static compensator (STATCOM) configuration that eliminates the dc-filter inductor requirement and can also operate at any MI value without necessitating additional control efforts. A detailed power analysis of the PHC-STATCOM for balanced and unbalanced grid conditions (UGCs) is performed in this article. A new control technique for PHC-STATCOM is proposed, which effectively balances the capacitor voltages of its chain-links even during UGCs. The energy storage requirement of PHC-STATCOM is evaluated to obtain the capability curve and determine its capacitor size. The PHC-STATCOM is compared with the popular STATCOM configurations in terms of the capacitor and switch counts. The proposed principles of PHC-STATCOM for several three-phase balanced and UGCs are verified using simulation and experimental studies.

Power Quality Analysis of the Output Voltage of AC Voltage and Frequency Controllers Realized with Various Voltage Control Techniques

Single-phase and three-phase AC-AC converters are employed in variable speed drive, induction heating systems, and grid voltage compensation. They are direct frequency and voltage controllers having no intermediate power conversion stage. The frequency controllers govern the output frequency (low or high) in discrete steps as per the requirements. The voltage controllers only regulate the RMS value of the output voltage. The output voltage regulation is achieved on the basis of the various voltage control techniques such as phase-angle, on-off cycle, and pulse-width modulation (PWM) control. The power quality of the output voltage is directly linked with its control techniques. Voltage controllers implemented with a simple control technique have large harmonics in their output voltage. Different control techniques have various harmonics profiles in the spectrum of the output voltage. Traditionally, the evaluation of power quality concerns is based on the simulation platform. The validity of the simulated values depends on the selection of the period of a waveform. Any deficiency in the selection of the period leads to incorrect results. A mathematical analytical approach can tackle this issue. This becomes important to analytically analyze the harmonious contents generated by various switching control algorithms for the output voltage so that these results can be successfully used for power quality analysis and filtering of harmonics components through various harmonics suppression techniques. Therefore, this research is focused on the analytical computation of the harmonics coefficients in the output voltage realized through the various voltage and frequency control techniques. The mathematically computed results are validated with the simulation and experimental results.

A Comprehensive Review on Control Techniques for Power Management of Isolated DC Microgrid System Operation

The present research investigations in power management fraternity are focused towards the realization of smart microgrid (MG) technologies. Due to intrinsic advantages of Direct Current (DC) system in terms of compatibility with power generation sources, modern loads and storage devices, DC MG has becoming popular over Alternate Current (AC) system. A secondary voltage and current control schemes of DC MG system are mainly based on the distributed consensus control of Multi-agent system (MAS) to balance generation and the demand. The basic concern of the cooperative control of MAS is consensus, which is to design a suitable control law such that the output of all agents can achieve synchronization. The distributed consensus algorithm requires much less computational power and information exchange in between the neighbor’s agent. Meanwhile the other controllers such as model predictive control (MPC) requires accurate dynamic models with high computational cost and it suffers from lack of flexibility. The hierarchical consensus control technique is classified into three levels according to their features, namely primary, secondary, and tertiary. MAS is a popular distributed platform to efficiently manage the secondary control level for synchronization and communication among the power converters in autonomous MGs. In this article, various primary control techniques for local voltage control, voltage restoration in the secondary control level and tertiary control for energy management techniques are discussed. With this, the key emphasis to reduce the voltage deviation and disturbances in a heterogeneous DC MG network solutions are discussed. Furthermore, to analyze the system response and the charging and discharging characteristics of the battery unit, the developed second order heterogeneous consensus controller is compared with the traditional homogeneous consensus control and droop control methods. Finally a detailed discussion on simulation case study using heterogeneous consensus control method over the traditional methods are provided using MATLAB/Simulink platform.

Sensorless Voltage Observer for a Current-Fed High Step-Up DC-DC Converter Using Extended Kalman Filter

In high voltage applications, sensorless voltage control techniques can reduce the cost and increase the reliability of DC-DC converters. In this paper, a sensorless voltage observer for a current fed Cockcroft-Walton voltage multiplier is designed. The first step is to derive the converter model. Since any inaccuracy in the derived model can result in a discrepancy between the observed voltage and the actual output voltage, an accurate model is derived, which incorporates the influential elements. Then, two voltage observers based on the extended Kalman filter (EKF) are designed and used to estimate the output voltage, transformer magnetizing current and inductor current for two different configurations of the high step-up DC-DC converter. Experimental and simulation results of the system show the efficiency of the observers. The proposed observers represent good precision as the main parasitic parameters are considered in the converter model.

Improved Digital Average Voltage Control for Switching Converter With Capacitor Current Compensation

Taking a buck converter in continuous conduction mode as an example, the improved digital average voltage (IDAV) control technique with capacitor current compensation is presented, and the operation principle and control law are analyzed in detail. The stability and transient performance impacted by the compensation coefficient are investigated by sampled-data modeling, and the optimal compensation coefficient for the fastest load transient performance is found. The analysis results show that the compensation coefficient can be regarded as a virtual equivalent series resistor (ESR) of the capacitor, which affects the stability and transient performance of the system without increasing output voltage ripple. Experimental results are given to verify the correctness of the theoretical analysis.

Three-level buck converter utilizing a DAC-based flying capacitor voltage control technique

This paper proposes a three-level buck converter utilizing a Digital-to-Analog Converter (DAC)-based flying capacitor voltage control technique, which controls the voltage on a flying capacitor with a differential difference amplifier and common mode feedback circuit for stable operation. Employment of the DAC-based flying capacitor voltage control circuit allows the proposed circuit to compensate for the inductor voltage error as the load current varies. The proposed three-level buck converter was implemented with a CMOS 180 nm standard process. The measurement results demonstrate the wide range of the input and output voltage from 2.7 V to 3.6 V and 0.7 V to 2.4 V, respectively. The proposed three-level buck converter achieved the peak power efficiency of 91% and output ripple voltage of 32.5 mV at the switching frequency of 2 MHz and load current range of 10 mA to 400 mA.

RETRACTED ARTICLE: Power sharing scheme in interconnected DC microgrids – A new approach

While the techno-economic feasibility of Solid State Transformer (SST) is constantly under question, some of the leaders in the power sector have recognised the potential of the technology and have started efforts of commercialisation. One of the important advantages of SST is its ability to integrate the low voltage DC grids technology. The key areas of research in this field is to use the accurate model of SST between two dc grids. In this article, an accurate composite model of SST that incorporates high switching frequency is developed. The model is controlled using a conventional voltage control technique and with a proposed power control technique. Thus developed SST is employed in transferring the power between two ring main dc microgrids (composed with distributed energy resources) using dual active bridge configuration. This article provides detailed insight of power-sharing scheme between two interconnected ring dc microgrids while maintaining its individual bus voltages within prescribed limits with supervisory communication control approach. Experiments have been conducted on the proposed method by using proposed control approach, and its results are explored.

An Efficient Vector Control Policy for EV-Hybrid Excited Permanent-Magnet Synchronous Motor

In this paper, a new control strategy for hybrid excited salient permanent-magnet synchronous motor (HEPMSM) is proposed, where both armature winding and DC field windings are located in the stator. The developed control strategy fulfills the required characteristics of the electric vehicles (EVs) and hybrid electric vehicles (HEVs) motors. A detailed mathematical model of the HEPMSM is presented. The field current (FC) is kept constant near its rated value for the high acceleration constant torque (CT) region. The conventional control usable method of reducing FC and reversing it on the motor performance characteristics through the constant power (CP) region is examined and evaluated. A proposed FC pattern is applied to three deferent operating modes of EV. High acceleration and wide stable constant power speed range without overdesign is the main target of this work. Based on the deduced optimum control pattern, the required EV-HEPMSM performance characteristics are developed. The required d–q control armature, field currents as well as d–q stator voltage components are provided for either current or voltage control technique availabilities. Simulation work is carried out on the commonly used method and on the proposed method. The obtained simulated characteristics effectively validate the target of the proposed steady-state presented analysis and pattern.

Effect of optimal Multi-DG siting and sizing in transmission system using hybrid optimization technique for voltage control

<span>The advancement of Distributed Generation (DG) technologies have caused great impact to power system operation. Inappropriate installation of DGs may lead to over-compensation or under-compensation situation. Thus, a reliable optimization is urgent to avoid any unwanted effect. This paper analyses the installation impact of different types-multi-DGs determined using a pre-developed hybrid optimization technique termed as Immunized-Brainstorm-Evolutionary Programming (IBSEP). It is imperative to study the effect of multi-DGs installation such that a relevant utility can make a correct decision, whether its installation is worth or vice versa. Rigorous study has been conducted in terms of identifying the optimal location and sizing, installed on transmission system for voltage control involving different DG types. Comprehensive results are embedded in this paper to demonstrate the effect of multi-DGs installation in transmission system which in turns beneficial to the utility.</span>

Detection and Mitigation of Data Manipulation Attacks in AC Microgrids

This paper presents a resilient control framework for distributed frequency and voltage control of AC microgrids under data manipulation attacks. In order for each distributed energy resource (DER) to detect any misbehavior on its neighboring DERs, an attack detection mechanism is first presented using a Kullback-Liebler (KL) divergence-based criterion. An attack mitigation technique is then proposed that utilizes the calculated KL divergence factors to determine trust values indicating the trustworthiness of the received information. Moreover, DERs continuously generate a self-belief factor and communicate it with their neighbors to inform them of the validity level of their own outgoing information. DERs incorporate their neighbors' self-belief and their own trust values in their control protocols to slow down and mitigate attacks. It is shown that the proposed cyber-secure control effectively distinguishes data manipulation attacks from legitimate events. The performance of proposed secure frequency and voltage control techniques is verified through the simulation of microgrid tests system implemented on IEEE 34-bus test feeder with six DERs.

Comparison of Voltage Control by Inverters for Improving the PV Penetration in Low Voltage Networks

Voltage rise caused by reverse power flows and intermittency in renewable power is the main limiting factor for integration of photovoltaic(PV) generation in low voltage networks. Inverter voltage control techniques have been developed to provide effective voltage control and support higher penetration integration of PV generation. In this paper, the common Volt-VAR control, PF(P) and Q(U) control of photovoltaic inverter methods are detailed compared. A set of simulation study-cases have been designed based on a generic LV grid model, which is considered as representative for the Bornholm network. Observations of the influence of different Volt-VAR control strategies upon different electrical parameters on hosting capacity increase potential have been performed. Results show that inverter controls can greatly contribute the integration of PV in LV networks in the perspective of avoiding overvoltage.

Robust Policy-Based Distributed Voltage Control Provided by PV-Battery Inverters

Various approaches that combine local, centralized and distributed voltage control techniques have been proposed in literature. These techniques suffer from different problems. Local voltage control systems suffer from degraded voltage regulation; centralized voltage control systems have poor reliability and scalability; distributed voltage control systems are complex to implement. To solve these issues, this paper proposes a novel distributed voltage control system enabled by robust linear policies. The proposed voltage control consists of two phases. In the day-ahead phase, the voltage control problem is formulated as a chance-constrained stochastic optimization problem, where the control actions are expressed as linear function of the uncertain households' active power consumption and photovoltaic power. The paper applies robust optimization to construct a tractable approximation to the chance constraints. In the real-time phase, the photovoltaic-battery systems communicate with each other and apply the robust policies to regulate voltages within limits. Simulations over 36500 scenarios are used to demonstrate the robustness of the proposed voltage control system.