Abstract: This paper investigates the operation of space-vector-based hysteresis current control in the synchronous reference frame (SRF) for grid-connected voltage source converters. The space-vector-based approach allows for the systematic application of zero-voltage vectors and prevents high switching frequencies caused by phase interaction. The average switching frequency can be minimized by always selecting the zero-voltage vector that is closest to the previous switching state. Implementation in the SRF ensures a simple structure based on two three-level hysteresis comparators and a switching table that fits well into the traditional structure of vector-oriented current control. For operation in a grid-connected converter with an LCL filter, the current references to the hysteresis controllers are given by a dc-link voltage controller and an active damping mechanism for suppressing filter oscillations. Results from simulations and laboratory experiments are presented to illustrate the features of the investigated approach compared to traditional phase-current hysteresis controllers.

Abstract: A modular power electronic converter, with a cascaded H-bridge multilevel inverter, has been proposed as the grid interface for a large direct-drive wind turbine generator. The present study is to investigate the potential and requirement of fault-tolerant operation in such a system. As each module is connected to isolated generator coils, tolerance to a module or coil fault is possible if the affected module can be bypassed, whereas the control of the healthy modules can be adjusted accordingly. A boost rectifier scheme on the machine side of the power conversion stage has been developed for this purpose, featuring control of the coil current without measuring the electromotive force. A coordinated dc-link voltage controller has been developed, which can rapidly raise the dc-link voltage of the remaining modules to compensate for the loss of a module while ignoring the ripple in the dc link due to low-frequency inverter switching. The ability of the resultant system to tolerate module faults has been demonstrated on a small-scale laboratory prototype.

Abstract: This paper proposes a multiloop controller with voltage differential feedback, and with output voltage decoupling and output current decoupling by only using the output voltage feedback. The output voltage differential feedback loop actively damps the output LC filter resonance and thus increases the system stability margin. The decoupling of output voltage and current makes the inner loop equivalent to a first-order system and thus improves the system dynamic response to load disturbance. The pole placement technique has been used here to design the inner loop and outer loop gain, with considering the effect of system control delay. The proposed control scheme possesses very fast dynamic response at load step change and can also achieve good steady-state performance at both linear and nonlinear loads. In addition, it only uses the output voltage as the feedback variable, which reduces the system complexity. The theoretical conclusion has been verified by simulation and experiment results. This method is proved to be an effective solution for voltage control in stand-alone mode of three-phase microgrid inverters.

Abstract: objective of this paper is to investigate the effect of membership functions in the fuzzy control (FC) of an ac voltage controller for speed control of induction motor drive. A Sugeno type FC for closed loop control of induction motor drive fed by ac voltage controller is designed and considered for evaluation. The controller is used to change the firing angle of the ac volage controller and thereby, the voltage fed to stator of induction motor to regulate the speed. Sugeno type FC is selected for evaluation, as it is easy to implement in simulation. The membership functions selected for evaluation are triangular, trapezoidal, Gaussian and bell shaped functions. The different membership function evaluation is done considering seven linguistic sets for error and change in error. The simulation model of different membership functions in the fuzzy control (FC) of an ac voltage controller for speed control of induction motor drive is implemented in Matlab/simulink The results of the simulated performances are compared. The triangular membership function shows better performance compared to other membership functions.

Abstract: Voltage source converter based on a chain-link cell topology, said converter comprising one or more phases (L1, L2, L3), each of said phases comprising one or more series- connected chain- link cell modules connected to each other, an output voltage of said voltage source converter is controlled by control signals applied to said cell modules. In case of failure of a chain- link cell module that module is controlled, by said control signals, such that zero output voltage is provided at its output voltage AC terminal.

Abstract: In this paper an intelligent fuzzy logic controller is proposed to control the frequency and voltage of a power generating system. The load frequency control (LFC) and automatic voltage regulator (AVR) are installed in each generator to control the real and reactive power flows. Due to rising and falling power demand, the real and reactive power balance is harmed and hence frequency and voltage get deviated from nominal value. This necessitates the need for an intelligent fuzzy controller to generate and deliver power in an interconnected system as economically and reliably as possible while maintaining the voltage and frequency within permissible limits. The conventional PID controllers employed for this task will have zero steady-state error but lead to large deviations in frequency and voltage under varying load conditions. The proposed method overcomes the drawbacks of a conventional fixed gain controller and improvement is achieved in terms of settling time, oscillations and overshoot. The single and...

Abstract: In at least one embodiment, the controller senses a leading edge, phase cut AC input voltage value to a switching power converter during a cycle of the AC input voltage. The controller senses the voltage value at a time prior to a zero crossing of the AC input voltage and utilizes the voltage value to determine the approximate zero crossing. In at least one embodiment, by determining an approximate zero crossing of the AC input voltage, the controller is unaffected by any disturbances of the dimmer that could otherwise make detecting the zero crossing problematic. The particular way of determining an approximate zero crossing is a matter of design choice. In at least one embodiment, the controller approximates the AC input voltage using a function that estimates a waveform of the AC input voltage and determines the approximate zero crossing of the AC input voltage from the approximation of the AC input voltage.

Abstract: The first single-loop current sensorless control (SLCSC) for single-phase boost-type switching-mode-rectifier (SMR) had been proposed in the prior paper. SLCSC with sinusoidal input voltage possesses good performance, but its performance with distorted input voltage should be improved. In this paper, a modified SLCSC is proposed and implemented in a field-programmable gate array (FPGA)-based system to obtain better performance than SLCSC. Instead of the phase-shift signal in SLCSC, the inductor voltage amplitude signal becomes the output of proportional-plus-integral (PI)-type voltage controller in the modified SLCSC. The provided simulation and experiment results demonstrate the modified SLCSC.

Abstract: A fast DC-link voltage controller is desirable to reduce the DC-link capacitor for PV inverters. This paper proposes a method for single-phase grid-connected PV inverters to remove the ripple component from the DC-link voltage signal and a scheme to regulate the DC-link voltage based on energy-balance analysis. The proposed scheme provides excellent dynamic performance as well as a function to prevent DC-link overvoltage by limiting the input power, which is verified by both simulation and experiments.

Abstract: Larger percentages of wind power penetration translate to more demanding requirements from grid codes. Recently, voltage support at the point of connection has been introduced by several grid codes from around the world, thus, making it important to analyze this control when applied to wind power plants. This paper addresses the analysis of two different voltage control strategies for a wind power plant, i.e. decentralized and centralized voltage control schemes. The analysis has been performed using the equivalent and simplified transfer functions of the system. Using this representation, it is possible to investigate the influence of the plant control gain, short circuit ratio, and time delays on the system stability, as well as the fulfillment of the design requirements. The implemented plant voltage control is based on a slope voltage controller, which calculates the references to be sent to the wind turbines, according to the slope gain and the difference between the reference and measured voltage at the point of connection. The results show that for a system where the time delay between the central control and the actuators is not negligible, the performance of a decentralized voltage control is better than the centralized one in terms of time reaction, disturbance rejection, and short-circuit ratio (SCR) dependency. However, for a system with reduced time delay (10 ms) the centralized scheme can have a performance similar to the decentralized one, in the SCR range of interest.

Abstract: The protection of the sensitive but unbalanced and/or non-linear loads from sag/swell, distortion and unbalance in supply voltage is achieved economically using a dynamic voltage restorer (DVR). A simple generalized algorithm for the generation of instantaneous reference compensating voltages for controlling DVR, based on basic SRF theory has been developed. This novel algorithm makes use of fundamental positive sequence phase voltages extracted by sensing only two unbalanced and/or distorted line voltages. The algorithm is general enough to handle linear as well as nonlinear loads. The compensating voltages when injected in series with a distribution feeder by a 3-single phase H-bridge voltage source converter (VSC) with constant switching frequency hysteresis band voltage controller, tightly regulate the voltage at load terminals against any power quality problem on the source side. A capacitor supported DVR does not need any active power during steady state operation because the injected voltage is in quadrature with the feeder current. The proposed control strategy is validated through extensive simulation studies in MATLAB.

Abstract: Systems and methods are provided for an electrical system. The electrical system, for example, includes a first load, an interface configured to receive a voltage from a voltage source, and a controller configured to receive the voltage through the interface and to provide a voltage and current to the first load. The controller may be further configured to, receive information on a second load electrically connected to the voltage source, determine an amount of reactive current to return to the voltage source such that a current drawn by the electrical system and the second load from the voltage source is substantially real, and provide the determined reactive current to the voltage source.

Abstract: Provided are methods, circuits, and systems for obtaining power from a power generator such as a photovoltaic cell or a fuel cell. The methods, circuits, and systems comprise converting substantially DC output power from the power generator into a high frequency AC voltage while rejecting or minimizing oscillations in the output power from the power generator; converting the high frequency AC voltage into a high frequency substantially sinusoidal voltage or current; and converting the high frequency substantially sinusoidal AC voltage or current into (i) a DC voltage or current, and (ii) a low frequency substantially sinusoidal AC voltage or current; wherein the high frequency substantially sinusoidal AC voltage or current is isolated from the DC voltage or current or the low frequency substantially sinusoidal AC voltage or current.

Abstract: The present invention discloses a voltage regulator, and a control circuit and a control method therefor. The method for controlling a voltage regulator comprises: receiving a dynamic voltage identification signal which instructs the voltage regulator to change its output voltage to a target voltage, and generating a compensation signal to shorten an interval for the output voltage of the voltage regulator to reach the target voltage.

Abstract: Aiming at the application requirement of high-input-high-output voltage, a novel solution on the base of input-series-output-series (ISOS) connected converter was proposed in the paper. The ISOS converter consists of two zero-voltage-zero-current-switched full bridge (ZVZCS-FB) converters, which are using the common-duty-ratio and share the same controller. The characteristics of the voltage sharing is analyzed in detail and verified by the experiments. The small-signal analysis of the topology and the design of the controller are also discussed in detail in the paper. The research results indicate the relationship between the effective duty ratio and the efficiency of each module, when the input voltage of the two modules is stable; and there is no need to take any measurements to realize the voltage sharing of the two modules, when the efficiency of the two modules are equal. The proposed solution has good value for high input voltage, high output voltage and high power applications.

Abstract: The present disclosure includes circuits, systems and methods for regulating voltage. One voltage regulator system embodiment includes a voltage regulator having an output and a number of stages coupled in parallel to the output of the voltage regulator. Each stage includes a source follower circuit, and a sample and hold circuit coupled in series between the output of the voltage regulator and an input of the source follower circuit.

Abstract: A three-phase three-level shunt active filter controlled by fuzzy logic current controller which can compensate current harmonics generated by nonlinear loads is presented. Three-level inverters and fuzzy controllers have been successfully employed in several power electronic applications these past years. To improve the conventional pwm controller performance, a new control scheme based on fuzzy current controller is adopted for three-level (NPC) shunt active filter. The scheme is designed to improve compensation capability of APF by adjusting the current error using a fuzzy rule. The inverter current reference signals required to compensate harmonic currents use the synchronous reference detection method. This technique is easy to implement and achieves good results. To maintain the dc voltage across capacitor constant and reduce inverter losses, a proportional integral voltage controller is used. The simulation of global system control and power circuits is performed using Matlab-Simulink and SimPowerSystem toolbox. The results obtained in transient and steady states under various operating conditions show the effectiveness of the proposed shunt active filter based on fuzzy current controller compared to the conventional scheme.

Abstract: Disclosed herein is a solid-state imaging element including: a plurality of unit pixels each having a photoelectric conversion part, a transfer part that transfers a charge generated by the photoelectric conversion part to a predetermined region, and a draining part that drains a charge in the predetermined region; a light shielding film being formed under an interconnect layer in the unit pixels and shield, from light, substantially the whole surface of the plurality of unit pixels except a light receiving part of the photoelectric conversion part; and a voltage controller controlling a voltage applied to the light shielding film. The voltage controller sets the voltage applied to the light shielding film to a first voltage in charge draining by the draining part and sets the voltage applied to the light shielding film to a second voltage higher than the first voltage in charge transfer by the transfer part.

Abstract: Microgrids are low-voltage distribution networks comprising various distributed generators (DGs), storage devices, and controllable loads that can operate either interconnected or isolated from the main distribution grid as a controlled entity. This paper concentrates on the modeling and control of a voltage-source-inverter-based microgrid. Considering the dispersion of DGs and loads, the controllers are designed using different control strategies respectively corresponding to the types of the DGs and ways of combining of storage devices. The Power and Voltage Controller coupled with the microsources provides fast response to disturbances and load changes without relying on communications. PQ control can realize the designated control of real and reactive power of DGs according to actual operation situation. V/f control can realize power sharing between different DGs when the load power changes, and provide frequency support when in the islanded mode. With the implementation of the unified controller, the inverter-based microgrid system is able to switch between islanding and grid-connected modes without disrupting connected critical loads. The two control strategies have been verified in simulation using MATLAB/SIMULINK by switching between interconnected and islanded modes.

Abstract: This research has been motivated by industrial demand for single phase PWM rectifier in traction application. This paper presents an advanced control structure design for a single phase PWM rectifier. The PWM rectifier is controlled to consume nearly sinusoidal current with power factor nearing to unity. The control structure consists of a DC-link voltage controller and a current controller implemented by a proportionalresonant controller using a fast phase angle and frequency estimator. The estimation algorithm is derived from the weighted least-squares estimation method. The feasibility of the proposed control structure is confirmed by experimental tests performed on designed laboratory prototype.

Abstract: A device includes a charge controller to regulate a battery output voltage based on an input voltage and an input current received from a charging circuit. A loop controller monitors the input voltage and the input current to generate a feedback signal to adjust the input voltage to the charge controller.

Abstract: This paper proposes the field weakening method of IPMSM(Interior Permanent Magnet Synchronous Machine) for the electric vehicle (EV) application. The method of using lookup-table generally used in automotive application has merits for fast dynamics, however containable data is limited especially on DC-link voltage. On the other hands, the method using a voltage feedback control has advantages in current control at variable speed and DC-link voltage automatically. However, dynamics is determined by the gain of controller. In this paper, field weakening control of fast dynamics and variable DC-link voltage is achieved by suitable combination of lookup-table and voltage feedback controller. Proposed method is verified by the simulation and experiment result.

Abstract: Voltage feed-back flux-weakening (FW) control scheme for vector-controlled Interior Permanent Magnet Synchronous Motor (IPMSM) drive systems is considered in this paper. The voltage controller is based on the difference between the amplitude of the reference voltage space vector and a proper limit value, related to the feeding inverter limitations, and adopts the phase angle of reference current space vector as the control variable. A novel theoretical analysis of the overall dynamics of the voltage control loop is carried out, also taking into account non-linear effects and discrete-time implementation issues. The design of the controller can therefore be optimized for each operating condition by an adaptive approach, allowing to define stability properties and to maximize bandwidth of the voltage control loop. Maximization of the dynamical performance provides the main advantage of the proposal, i.e. allows a lower voltage (control) margin to be considered with respect to standard approaches, leading to a higher torque and system efficiency and/or a reduced value of the dc-bus capacitance. A motor drive system for home appliances is considered as a test bench to prove the effectiveness and importance of the proposal.

Abstract: The microgrid concept has the potential to solve major problems arising from large penetration of distributed generation in distribution systems. A microgrid is not a robust system when compared to a power system. Therefore, proper control strategies should be implemented for a successful operation of a microgrid. This paper proposes the use of a coordinated control of reactive sources for the improvement of the dynamic voltage stability in a microgrid. The associated controller is termed as a Micro Grid Voltage Stabilizer (MGVS). The MGVS is a secondary level voltage controller which takes the weighted average of the voltage deficiencies at the load Buses and generates a control signal. This control signal is divided among the reactive power sources in the microgrid in proportion to their available capacities; thus each source will be required to generate certain amount of reactive power. The MGVS is implemented in a micro grid test system in MATLAB environment. A dynamic simulation of the test system is carried out for the cases of with and without the MGVS for various disturbances. Both grid-connected and islanded modes of operation are considered. Results show that, with the addition of MGVS, the dynamic voltage profile of the microgrid system, especially at the load Buses, improve drastically.

Abstract: An analog to digital converter (ADC) can include a multi-input comparison unit configured to compare a pixel voltage from an image sensor, a comparison voltage comprising a stepped voltage modified during a coarse mode of operation, and a ramp voltage comprising a ramped voltage modified to one another during a fine mode of operation, to provide a comparison result signal that indicates whether the comparison voltage combined with the ramp voltage is greater than or less than the pixel voltage. A selection control signal generation unit can receive the comparison result signal and a mode control signal, to indicate the coarse or fine mode, to provide a selection control signal allowing modification of the comparison voltage in the coarse mode and to hold the comparison voltage constant in the fine mode. A reference voltage selection unit can receive the selection control signal to control modification of the comparison voltage.

Abstract: A method of operation of a power supply system includes: providing a source voltage with a power source; generating a device voltage with the source voltage; monitoring the source voltage and the device voltage; and supplying the device voltage to a mobile device with the device voltage controlled by a control unit.

Abstract: This paper proposes the new voltage controller in photo-voltaic system for Stand-Alone Applications with battery energy storage. The output of the PV array is unregulated DC supply due to change in weather conditions. The maximum power is tracked with respect to temperature and irradiance levels by using DC-DC converter. The perturbation and observes algorithm is applied for maximum power point tracking (MPPT) purpose. This algorithm is selected due to its ability to withstand against any parameter variation and having high efficiency. The solar cell array powers the steady state energy and the battery compensates the dynamic energy in the system. The aim of the control strategy is to control the SEPIC converter and bi-direction DC-DC converter to operate in suitable modes according to the condition of solar cell and battery, so as to coordinate the two sources of solar cell and battery supplying power and ensure the system operates with high efficiency and behaviors with good dynamic performance. The output of DC-DC converter is converted to AC voltage by using inverter. The AC output voltage and frequency are regulated. A closed loop voltage control for inverter is done by using unipolar sine wave pulse width modulation (SPWM). The regulated AC voltage is fed to AC standalone loads or grid integration. The overall system is designed, developed and validated by using MATLAB-SIMULINK. The simulation results demonstrate the effective working of MPPT algorithm, control strategy and voltage controller with SPWM technique for inverter in AC standalone load applications. DOI: http://dx.doi.org/10.11591/ijpeds.v2i1.127

Abstract: This paper investigates the use of new technologies for current and voltage measurement especially in high voltage equipment It is focused to the principle of low power current transformers with voltage output and to the resistive-capacitive dividers for voltage measurement The principles of these devises are explained and their advantages and new features in comparison to known inductive and capacitive principles are discussed An important step into the world of smart grid is the integration of these sensor principles into the new digital communication A digital interface, realised with a merging unit, is proposed With this digital interface the values of current and voltage can be distributed to the secondary measurement and protection equipment

Abstract: This paper proposes a nonlinear voltage regulator with one tunable parameter for multimachine power systems. Based on output feedback linearization, this regulator can achieve simultaneous voltage regulation and small-signal performance objectives. Conventionally output feedback linearization has been used for voltage regulator design by taking infinite bus voltage as reference. Unfortunately, this controller has poor small-signal performance and cannot be applied to multimachine systems without the estimation of the equivalent external reactance seen from the generator. This paper proposes a voltage regulator design by redefining the rotor angle at each generator with respect to the secondary voltage of the step-up transformer as reference instead of a common synchronously rotating reference frame. Using synchronizing and damping torques analysis, we show that the proposed voltage regulator achieves simultaneous voltage regulation and damping performance over a range of system and operating conditions by controlling the relative angle between the generator internal voltage angle δ and the secondary voltage of the step up transformer. The performance of the proposed voltage regulator is evaluated on a single machine infinite bus system and two widely used multimachine test systems.