Constant Voltage Regulation Research Articles

Distributed Secondary Control of DC Microgrid with Power Management Based on Time-of-Use Pricing and Internal Price Rate

This paper presents a novel approach to manage distributed DC microgrids (DCMG) by integrating a time-of-use (ToU) electricity pricing scheme and an internal price rate calculation mechanism. The proposed power-management system is designed to effectively handle uncertainties such as utility grid (UG) availability, fluctuating electricity prices, battery state of charge (SOC) levels, and frequent plug-ins and plug-outs of electric vehicles (EVs). Uncertainties in DCMG systems often lead to inefficiencies, power imbalances, and inexact voltage regulation issues within DCMGs. In addition, to maintain the power balance and constant voltage regulation under various operational states, the proposed scheme also incorporates secondary control into the DCMG power-management system. Unlike the existing approaches that often fail to adapt dynamically to changing conditions, the proposed method is the first approach to consider the concept of internal price rate in designing the DCMG power management. To address this challenge, this approach proposes a more resilient power-management strategy to enhance the efficiency and adaptability of DCMG systems. Extensive simulations and experimental validations demonstrate the practicality and adaptability of the proposed control strategy under diverse test conditions, including operation transitions between grid-connected mode (GCM) and islanded mode (IM), low battery SOC condition, operation transition from the current control mode (CCM) to distributed secondary control mode (DSCM), and EV plug-in scenarios. The test results confirm that the proposed method enhances the reliability, efficiency, and economic viability of DCMG systems, making it a promising solution for future smart grid and renewable energy integrations.

Observer-Based Finite-Time Disturbance Rejection Control for Dynamic Wireless Charging Systems With Constant Output Voltage Regulation

Observer-Based Finite-Time Disturbance Rejection Control for Dynamic Wireless Charging Systems With Constant Output Voltage Regulation

A Bidirectional Direct AC-AC Resonant SCC

A direct ac-ac resonant switched-capacitor converter (SCC) for both noninverting and inverting output voltages is proposed here, which is suitable for bidirectional power transmission including different applications such as dynamic voltage restorer (DVR), constant voltage regulator (CVR), and constant current regulator (CCR). Zero voltage switching (ZVS) and zero current switching (ZCS) operation conditions are easily realized for its power switches, which effectively reduce the switching losses, as well as the electromagnetic interference (EMI) noise. Consequently, high-frequency operation is possible, which improves the converter power density, in practice. Continuous voltage-gain, transformerless connection of the converter output port to the gird, no commutation problems without using extra components, and improving the electrical specifications are some other advantages of the given resonant SCC. The converter operation principles, its key waveforms and different operational states, its mathematical analysis and normalized state-plane trajectories, simulation results, as well as its design procedure, are also given here, in detail. To verify the given theoretical analyses and simulation results, a 500 W prototype converter for a 2 kW DVR with 220 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> nominal output voltage has been implemented successfully, which realizes 96.55% efficiency at its rating power value.

Rehabilitation and Techno design of Distribution transformer and 11kV feeder of a radial distribution system

In any transmission and distribution system- the performance of that system mainly depends on voltage regulation and efficiency. Hence for the better operation of the system, it is required to maintain constant voltage regulation with good power factor and low power loss throughout the feeder. This can be achieved by using various methods. Out of those, placement of a capacitor bank at the densely loaded areas is the best-proven method compared to any other method. This research work considered the feeder-5 of the Al-Uwainath primary substation which was suffering from low voltage–poor regulation- problems. Here in this research modeled and analyzed 3 different techniques for rehabilitation to this low voltage, poor regulation, and power factor problem and recommended the most efficient method out of the three methods. As a part of this project simulated the same conditions of the site after collecting the data of the feeder from the site by using ETAP software and checked the performance by calculating its voltage regulation, power losses, and power factor in all three 3 different methods and recommended the most efficient method of feeder-5 rehabilitation by comparing the results of three methods with the exciting system.

An adaptive control strategy for grid-forming of SCIG-based wind energy conversion systems

One of the crucial issues in the expansion of isolated wind energy conversion systems (WECSs) is the design of a grid forming control structure that is robust to changes of the system’s operating point in the steady-state as well as transient conditions. This paper has addressed the voltage/frequency control of a local microgrid as well as flux and slip control of a squirrel cage induction generator that feeds the microgrid via a back-to-back converter in an isolated WECS. An adaptive nonlinear voltage control structure has been proposed for load side converter (LSC) consists of a constant frequency voltage regulator and a current controller based on the Lyapunov function method (LFM), which are connected in cascade. In an outer loop, the reference current of LSC is generated by the voltage regulator designated for maintaining the voltage/frequency of the microgrid. In an inner loop, the reference signals are robustly tracked by the current controller. In a novel reference frame that its angle difference with the stationary reference frame is determined by a dual loop DC link voltage controller, an LFM-based nonlinear flux controller is proposed for the machine side converter (MSC). Using the proposed flux control structure, in addition to maintaining the flux magnitude at a nominal value, by controlling the generator slip through adjusting the speed of the proposed reference frame, the power balance is established and the DC voltage is maintained at a pre-set value. The performance of the proposed controllers has been investigated through simulation in the MATLAB® software. The obtained results confirm the robustness and stability of the proposed control structure with respect to various disturbances and uncertainties.

A Multimode Control Scheme for Output Regulation and Voltage Balancing in a Stacked-Switch Resonant Converter With Extended High Efficiency for Wide Gain Range Applications

In this article, a new hybrid comprehensive multimode control system is proposed for a stacked-switch bidirectional CLLC resonant converter for wide voltage gain applications. By configuring the presented leg with different switching patterns, the presented leg in the converter can operate in different modes: full-wave (FW), half-wave (HW), or voltage-doubler (VD) through the converter’s built-in circuit redundancy. The proposed hybrid control scheme consists of different control modes: variable frequency modulation, pulse-width modulation (PWM), and asymmetric PWM (APWM) control. Correspondingly, four voltage gain curves are derived from the proposed converter. With the proposed approach, the converter is able to achieve constant voltage regulation while constraining the range of switching frequency, allowing very high efficiencies to be realized for a wide range of input voltages. Soft-switching is achieved for all the semiconductor devices for the entire operating range. The steady-state and dynamic performances of the proposed hybrid comprehensive control system are verified through a proof-of-concept 400-V <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim ~1$ </tex-math></inline-formula> -kV/ 700-V, 1-kW laboratory prototype. Results confirmed that the efficiency is maintained between 95.03% and 96.97% throughout the specified input voltage range.

Dynamic Analysis and Active Stabilization of a Utility-Scale Grid-Connected Current-Source Inverter-Based PV System Considering Source Dynamics

This paper investigates the effects of the dynamic properties of a photovoltaic generator (PVG) on the stability of a grid-connected current-source inverter (CSI)-based photovoltaic system and presents a simple yet effective active compensator to ensure system stability. A detailed equivalent model of the PVG that considers the dynamic resistance, diffusion capacitance, series inductance, and dc cable resistance and inductance is used, and the effects of these parameters are assessed. It has been found that when the PVG operates in the constant-current region (CCR), the phase margin becomes negative in the control-to-input dynamics, which alters the stability of the dc-link current control. The change in the system dynamics when the operating point of the PVG shifts from the constant-voltage region (CVR) to CCR is verified through a detailed small-signal state-space model of the complete system. Furthermore, an active compensator is proposed to ensure stable dc-link current control operation at all operating points of the PVG. The influence of different control parameters on the integrated system dynamics is examined to determine the range of the control parameters required for stable operation. The performance of the proposed system under utility-grid fault, grid voltage parameter variation, weak grid, and changes in insolation level is also evaluated. Detailed nonlinear time-domain simulation results, using a typical utility-scale CSI-based PV system, validate the analytical results and the effectiveness of the proposed active stabilization under different operating conditions.

Deepening into the charge storage mechanisms and electrochemical performance of TiO2 hollandite for sodium-ion batteries

The electrochemical performance of TiO2 hollandite, TiO2(H), obtained by complete K+ ion extraction of the bronze K0.2TiO2 is investigated. TiO2 develops a fairly stable capacity of 106 mAh g–1 after 300 cycles at C/8 (42 mA g–1) and maintains 100 mAh g–1 after 600 cycles. At high current rate (2C, 671 mA g–1) 55 mAh g–1 is still maintained. Cycling produces nanosizing of the TiO2 electrode (to 200–300 nm) by electrochemical milling but cyclic voltammetry at different sweep rates indicates that diffusive controlled faradic contribution to the total capacity of TiO2(H) due to Na insertion is significant even at high current. However, participation of pseudocapacitive charge storage is unveiled. The voltage profile resembles in fact that of pseudocapacitive materials with no clear evidence of a constant voltage region. Operando XRD confirmed the lowering of symmetry from tetragonal I4/m to monoclinic I2/m upon sodiation with a relatively narrow two-phase region different from other long plateaus of typical battery materials. Cyclic voltammetry clearly indicates that the two peaks (centered at 1.25 and 0.5 V on reduction) correspond to diffusion-limited faradic processes. Thus, it can be said that hollandite TiO2 is a battery-like material, but for which kinetics is not limited by a biphasic transformation. Instead, kinetics is limited mainly by slow diffusion in single phases with variable composition (continuous variation of voltage vs. capacity) that are formed upon Na+ intercalation into the tunnels. The limited diffusion at high sweep rate favors the dominance of pseudocapacitance (charge transfer at the surface). A comparison with the bronze K0.2TiO2 reveals the importance of potassium in the electrochemical properties and the nature of the different physicochemical processes of both compounds.Sodium ion diffusion coefficient in TiO2(H), 2.6 · 10–13 cm2 s–1, is several orders of magnitude higher than that of TiO2 rutile and anatase, however it does not provide a fast intercalation into the tunnels to consider it a pseudocapacitive intercalation material.

A Step-Up Reconfigurable Multimode LLC Converter Module With Extended High-Efficiency Range for Wide Voltage Gain Application in Medium Voltage DC Grid Systems

In this article, a newmodular multimode reconfigurable step-up resonant converter that is capable of extending very high efficiency from full load to reduced load conditions is proposed for wide voltage gain application in medium voltage dc (MVdc) grid system. The proposed converter module is able to switch from a hybrid control scheme that consists of variable frequency and phase shift control to pulsewidth modulation (PWM) control in the auxiliary switch of the output voltage quadrupler (VQ). In addition, the input bridge can also be reconfigured to a half-bridge mode to suit high input voltage range while utilizing a hybrid control technique that consists of variable frequency and asymmetrical PWM control. With the proposed approach, the converter module is able to achieve constant output voltage regulation without requiring a wide spectrum of switching frequency or phase shift control. Hence, close-to resonance operation with very high efficiency can be maintained for a wide range of input voltage and loading conditions. Soft switching operations are always guaranteed for all the primary side switches, the output diodes and the auxiliary switch in the VQ. The steady-state and dynamic performance of the proposed modular multimode step-up converter are validated through simulation results on a silicon carbide (SiC) based 360 V–1 kV/16 kV, 80-kW system and experimental results on a proof-of-concept 150–400 V/6.6 kV, 10-kW SiC laboratory prototype. Results confirmed that the efficiency is maintained between 97.8% and 99.1% from full load to at least 20% load condition for the specified input voltage range.

Decentralized Power Management of DC Microgrid Based on Adaptive Droop Control With Constant Voltage Regulation

An adaptive droop control with constant voltage regulation is proposed for the power and voltage management of a DC microgrid (DCMG) with multiple power sources, such as a utility grid (UG), a distributed generator (DG), an energy storage system (ESS), and an electric vehicle (EV). In the proposed scheme, the droop characteristics for the UG, ESS, and EV are adaptively changed according to electricity price conditions and state-of-charge (SOC) levels in order to optimize the DCMG operation flexibility as well as electricity cost. The proposed control method not only ensures the power-sharing of DCMG reliably without the use of a communication link, but also regulates the DC bus voltage stably at the nominal value. To achieve this, the proposed scheme consists of primary control and secondary control. The primary control is used to achieve power-sharing in the decentralized DCMG, while the secondary control is used to overcome the disadvantage of conventional droop control, i.e., to remove DC bus voltage deviations. Decentralized power management is also presented to enhance the DCMG system reliability in the presence of uncertainties such as DG generation power, the ESS and EV SOC levels, the grid and EV availabilities, the load demand, and electricity price conditions. The effectiveness of the proposed scheme is demonstrated in a comprehensive simulation and experiment under various conditions. The test results clearly confirm the control flexibility and overall performance of the proposed control scheme for decentralized DCMG system.

A Two-Stage Isolated High Step-Up Quasi-Resonant DC-DC Converter with Pre-Voltage Regulator

A two-stage isolated high step-up quasi-resonant DC-DC converter with pre-voltage regulator is proposed in this article. A quasi-resonant network and a voltage doubler are added on the secondary side of the transformer to achieve voltage lift-up in the latter stage, which can realize the ZVS turn-on of primary switches and there is also no reverse recovery loss in the secondary side diodes. In order to ensure the efficient operation of the system, the latter stage is designed to operate at the rated state to achieve a constant output. While the front-stage synchronous Buck-Boost converter acts as a voltage regulator to realize constant voltage regulation in a wide input voltage range. An experimental prototype with an input voltage range of 20-28 V and output 400 V&#x002F; 0.5 A is built under 1 MHz switching frequency. A peak efficiency of 93.6&#x0025; is achieved. The experimental results verify the correctness of the theoretical analysis.

Implementasi Kontroler PI Pada Buck Converter Sebagai Pengaturan Tegangan Konstan Di Sistem Turbin Angin Permanent Magnet Schronous Generator (PMSG) Dilengkapi Sistem Monitoring Berbasis IoT

The need for electrical energy has become a primary need for humans, until now the energy used to generate electrical energy is fossil fuels whose numbers are dwindling. Renewal of energy is needed through renewable energy, namely using unlimited wind energy. The wind speed is always changing in a fluctuating manner which can affect the output voltage at the power plant. In this study, the wind turbine used is a permanent magnet synchronous generator, the output voltage from the generator is a 3-phase electric voltage which is then rectified into a DC voltage. To be able to stabilize the voltage, a buck converter circuit is used as a voltage reducer, the switching control used in the buck converter uses a half bridge with IC IR2110 with a frequency of 31.5 kHz. The buck converter can reduce the voltage with an input voltage range of 30-100 Volts with a duty cycle of 10- 90%, the PI control system on the buck converter circuit for constant voltage regulation of 27 Volts (settpoint) and using the IoT thingspeak website for remote monitoring.

A Low-Profile High-Efficiency Fast Battery Charger With Unifiable Constant-Current and Constant-Voltage Regulation

Present universal serial bus (USB) battery chargers often suffer from limitations to meet the increasing demand for quick charging due to compromised power efficiency and complicated hardware implementation. In this paper, we propose a charge unifiable (QU) control scheme that enables a battery charger to improve power efficiency in a low-profile hardware manner. This scheme features fully soft-switching (vis-a-vis hard switching) and single control scheme (vis-a-vis multiple) for distinct constant current (CC) and constant voltage (CV) charging modes. To the best of authors’ knowledge, the proposed QU control scheme is the first to simultaneously offer fully soft-switching, innate CC-and-CV regulation, and seamless CC-to-CV transition. To verify the proposed design, we monolithically realize a low-profile high-efficiency fast battery charger based on this scheme. The prototype embodying a tiny 470-nH output inductor supports a maximum input voltage of 16V, output voltage of 2.2-4.2 V, output current of 0.1-2 A, and peak power efficiency of 96.2%. When benchmarked against state-of-the-art counterparts, the proposed charger features at least $2.1\times $ smaller inductor and 7.2% higher power efficiency at both the maximum and the minimum output power charging scenarios. Further, this charger is the only design that features ≥91% power efficiency in the whole load range.

Automatic Tap-Changer with TRIAC Switch for Constant Voltage and Current Measurements

This research article demonstrates how to protect the power transformer from over load time. It is to controlling our desired voltage on various load times but the research gives some solution to avoid over voltage problem by automatic tapping technique. In this research tapping of transformer is selected automatically with the help of Peripheral Interface Controller (PIC) microcontroller. Effective use of potential transformer is to find out the precision in the system. The load voltage is measured by potential transformer which is given to precision rectifier. It will produce the accurate voltage levels. Here the things are using PIC microcontroller which is a flash type reprogrammable device in which system was already programmed. The Model was fabricated with Triode for Alternating Current (TRIAC) switches just as a switching devices and Peripheral Interface Controller microcontroller just as a control unit. In this research automatic control sections by using tap changer. In conventional methods industrialist used mechanical on load tap changer which is highly risk, because it does not produces constant output voltage and can create voltage dips. In this research it will be overcome above problem by using automatic electronic tap changer. It will produce constant voltage regulation and to measure variation of current.

A quick and effective MPPT scheme for solar power generation during dynamic weather and partial shaded conditions

Photovoltaic (PV) panels are equipped with Maximum Power Point Tracking (MPPT) schemes to extract utmost available power even during dynamic weather conditions (DWC) and partial shaded conditions (PSC). Though P-V and I-V characteristics of a PV system are affected by DWC and PSC, they have a constant current region (CCR) and constant voltage region (CVR). To achieve the optimal operating point of a PV system, the existing conventional MPPT schemes have to pass through CCR and CVR regions which consume time. Hence, this paper presents a novel MPPT scheme that eliminates perturbation in constant regions in any condition by projecting tangents over P-V characteristics thereby approaches an estimated point on the top of the curve quickly. Further, the iterative procedure involved in the proposal achieves the exact optimal point according to operating conditions of the system. Experimental and simulation results of the proposed methodology provide enough evidence to prove the superiority of the proposed method over conventional Perturb and Observe (P&OC) scheme.

Development of PRF extractor using thermoelectric element and temperature sensor

Recently, Platelet-rich fibrin (PRF) centrifuges have been used in PRF separation for autologous PRF procedure that can lower the financial burden to patients treated with dental implants. When autologous blood is used to separate PRF, temperature maintenance acts as one of the important variables for high-efficiency PRF extraction. Therefore, in this study, we developed a PRF centrifuge that could control temperature by thermoelectric element and temperature sensor. In order to implement precision temperature control, a circuit was constructed using a PT100Ω temperature sensor. We developed our own sensor module for the PT100Ω. A 1mA constant current circuit was constructed for the temperature control module, and a constant voltage regulator was used. The current and voltage were not affected by the external circuit, and the temperature sensor could detect only the temperature imposed upon it. This made it possible to sense the temperature with high sensitivity. Thermoelectric elements were controlled based on the sensed temperature using the PT100Ω. The thermoelectric element and temperature sensor module were used in developing the PRF extractor to precisely control the temperature. The temperature change according to the number of thermoelectric elements was confirmed. As a result, the desired temperature could be reached using a total of six thermoelectric elements.

Dual Mode Controller-Based Solar Photovoltaic Simulator for True PV Characteristics

Integration of solar photovoltaic (PV) panels with existing utilities requires effectively controlled converters. While developing and testing such converters, it is difficult to test them with actually installed PV panels owing to unavailability of practical onsite conditions for all the time. For such cases, PV simulators are preferred, which are required to exhibit PV system behavior under working conditions without the use of real outdoor installation. This reduces the time and cost of experimentation. In this paper, a real-time PV simulator based on a dc-dc buck converter is investigated to obtain true PV characteristics. The practical difficulty with PV simulators is that they often get oscillations in the constant current region or constant voltage region of PV characteristics, particularly when the controller is designed using a low-cost digital controller. This paper introduces a novel hysteresis controller to ensure effective operation in both these regions. This dual control strategy ensures effective control in both regions and provides smooth trajectories as per mathematical model or lookup table to mimic any PV characteristics under various temperatures and insolations with the use of the low-cost digital controller. The hardware prototype is constructed with the digital signal controller to demonstrate the efficacy of the proposed simulator.

Modified Electronic Load Controller for Constant Frequency Operation With Voltage Regulation of Small Hydro-Driven Single-Phase SEIG

This paper is aimed at design and implementation of a modified electronic load controller (MELC) for constant frequency operation with voltage regulation of a two winding single-phase self-excited induction generator (SEIG) applicable for renewable energy applications specifically for off-grid power generation using a small-size hydro energy. The system frequency is maintained constant at a reference level for fixed as well as variable input mechanical power to the prime mover experienced in small hydro systems due to seasonal variations. The point of common coupling (PCC) voltage is also regulated by the controller at varying loads by controlling the power flow to the dump load. The proposed MELC is developed for the constant frequency generation and voltage regulation of single-phase SEIG with frequency as a feedback variable.

Distortion-Free CV/CC AC Power Supply Having the Unity Input Power Factor by the Use of Variable Capacitance Devices

A new CV (Constant-Voltage) CC (Constant-Current) ac power regulator is proposed. Our original Variable Capacitance Device of linear reactance device is utilized in the power stage. This device makes almost no distortion. In this circuit, a sinusoidal output voltage and a high efficiency can be obtained. For the purpose of output voltage/current control and input power-factor correction, two Variable Capacitance Devices were adopted. Two dc-dc converters were used for high-speed driver of these devices. The unity input power factor can be obtained all over the constant-voltage region and the constant-current region. Input current of the proposed power supply becomes almost zero at no load and at short-circuit load.

Characterizing the Dynamics of the Peak-Current-Mode-Controlled Buck-Power-Stage Converter in Photovoltaic Applications

It is well known that the application of peak-current-mode (PCM) control produces highly desirable properties in the conventional or voltage-fed converters but requires to compensate the inductor-current loop for extending the active duty ratio beyond 50%. This paper investigates the dynamical properties and operational constraints of a PCM-controlled buck-power-stage converter in the photovoltaic (PV) applications. It has been already earlier noticed that the application of PCM control can make the converter unstable in the PV applications. The investigations reveal that the inductor-current feedback forces the open-loop converter to adopt the dynamic properties of a voltage-fed converter, and consequently, the stable operation is limited to the constant-voltage region of the PV generator. The developed small-signal models reveal that a right-half-plane pole appears in the converter dynamics, when the operation point enters into the constant-current region leading to instability. The stability can be restored by heavily compensating the inductor-current loop, which seriously removes the desired properties materialized in the conventional buck converter. The provided experimental evidence fully supports the theoretical findings.