Abstract: This paper proposes a low-voltage ride-through scheme for the permanent magnet synchronous generator (PMSG) wind power system at the grid voltage sag. The dc-link voltage is controlled by the generator-side converter instead of the grid-side converter (GSC). Considering the nonlinear relationship between the generator speed ωm and the dc-link voltage Vdc , a dc-link voltage controller is designed using a feedback linearization theory. The GSC controls the grid active power for a maximum power point tracking. The validity of this control algorithm has been verified by simulation and experimental results for a reduced-scale PMSG wind turbine simulator.

Abstract: This paper presents a novel adaptive dc-link voltage-controlled LC coupling hybrid active power filter (LC-HAPF) for reducing switching loss and switching noise under reactive power compensation. First, the mathematical relationship between LC-HAPF dc-link voltage and reactive power compensation range is deduced and presented. Based on the compensation range analysis, the required minimum dc-link voltage with respect to different loading reactive power is deduced. Then, an adaptive dc-link voltage controller for the three-phase four-wire LC-HAPF is proposed, in which the dc-link voltage as well as the reactive power compensation range can be adaptively changed according to different inductive loading situations. Therefore, the compensation range, switching loss, and switching noise of the LC-HAPF can be determined and reduced correspondingly. In this paper, the reference dc-link voltage is classified into certain levels for selection in order to alleviate the problem of dc voltage fluctuation caused by its reference frequent variation, and hence reducing the fluctuation impact on the compensation performances. Finally, representative simulation and experimental results of a three-phase four-wire center-split LC -HAPF are presented to verify the validity and effectiveness of the proposed adaptive dc-link voltage-controlled LC-HAPF in dynamic reactive power compensation.

Abstract: This paper introduces a robust adaptive control strategy of shunt active power filters (SAPF) for power-factor correction, harmonic compensation, and balancing of nonlinear loads. The proposed control scheme is implemented without load harmonic detection. The compensation constraints are obtained by regulating indirectly the currents of the power mains. The reference currents of are generated by the dc-link voltage controller based on the active power balance of system. They are aligned to the phase angle of the power mains voltage vector, by using a phase-locked loop system. The current control strategy is implemented by an adaptive pole-placement control strategy integrated to a variable structure control scheme. This control scheme uses the internal model principle of reference currents for achieving the zero steady-state tracking error. Experimental results are shown for determining the effectiveness of an -proposed control system.

Abstract: This paper proposes a hierarchical active power management strategy for a medium voltage (MV) islanded microgrid including a multihybrid power conversion system (MHPCS). To guarantee excellent power management, a modular power conversion system is realized by parallel connection of small MHPCS units. The hybrid system includes fuel cells (FC) as main and supercapacitors (SC) as complementary power sources. The SC energy storage compensates the slow transient response of the FC stack and supports the FC to meet the grid power demand. The proposed control strategy of the MHPCS comprises three control loops; dc-link voltage controller, power management controller, and load current sharing controller. Each distributed generation (DG) unit uses an adaptive proportional resonance (PR) controller for regulating the load voltage, and a droop control strategy for average power sharing among the DG units. The performance of the proposed control strategy is verified by using digital time-domain simulation studies in the PSCAD/EMTDC software environment.

Abstract: In a switching power supply apparatus, a first switching element is controlled by a driving voltage output from a switching control IC. A second switching control circuit controls the on-time of a second switching element so that the time ratio of the on-time of the second switching element to the on-time of the first switching element becomes almost constant with respect to a change in a load current. In a normal load state, since a square wave output from a frequency setting unit within the switching control IC is output with no change, a converter operates in a current-continuous mode. In a light load state, a driving signal generation unit within the switching control IC is subjected to blanking with the period of a signal output from a maximum frequency setting unit and an oscillation frequency is reduced. Accordingly, the converter operates in a current-discontinuous mode.

Abstract: Provided is a transmitter in a wireless power transmission system, the transmitter including a Transmission (Tx) power converter for converting a Direct Current (DC) voltage into a first Alternating Current (AC) voltage, and converting the converted first AC voltage into a second AC voltage by amplifying the converted first AC voltage, a Tx matching circuit for matching an impedance thereof with that of a receiver for receiving the second AC voltage to transmit the second AC voltage, a Tx resonator for resonating the second AC voltage into resonant waves to transmit the second AC voltage to the receiver, and a Tx controller for determining an amplification rate of the first AC voltage and controlling the Tx power converter to convert the first AC voltage into the second AC voltage according to the determined amplification rate.

Abstract: Apparatuses and methods are disclosed for regulating or limiting the voltage output from solar modules connected in series such that the voltage on a string bus connecting those solar modules does not exceed regulatory or safety limitations. This can be accomplished via a controller, local management units (for downconverting solar module voltage output), or a combination of the two.

Abstract: This article reports the results from the implementation and testing of a Wide-Area Power Oscillation Damper (WAPOD) controlling a 180 Mvar TCR Static Var Compensator (SVC) installed in the Hasle substation of Norwegian 420 kV transmission grid. The WAPOD uses voltage phase angle signals from two distant locations in the Norwegian grid as inputs to the damping controller. The damping controller modulates the voltage reference set point used by the SVC's voltage controller, thereby creating a damping effect. The WAPOD is an extension to the existing Power Oscillation Damping (POD) controller that uses local measurements. A switch-over logic allows for the use of no damping control, local damping control or wide-area control. Field tests were performed during November 2011, and involved the disconnection and re-connection of a 420 kV transmission line. The performance of the WAPOD is compared to that of state-of-the-art local Phasor POD, and when no damping control is enabled. The testing results show that the WAPOD performed satisfactorily and according to the design expectations. These results show that the potential flexibility of the WAPOD to choose, among the different PMU signals, those that have the good observability of inter-area modes can be an advantage to the use of local feedback signals for damping control, as it is current practice today. Further testing of this WAPOD with other PMU signals from locations with stronger observability will be helpful to illustrate the advantage of this flexibility.

Abstract: One of the advantages of power factor corrector with boundary current mode control is the reduction of reversal recovery loss of diode. This paper proposes a family of predictive methods adapted to digital pulse-width modulations for digital-controlled PFC operated under boundary current mode. The DPWM methods include leading-edge modulation, trailing-edge modulation and triangular modulation. For the proposed control method, the switching period retaining zero current switching is predicted and the turn-on period is determined by the voltage controller. Therefore, neither zero-current detection nor high-frequency A/D converter for current sampling is required for the proposed control method.proposed control method. Experimental results derived from a DSP-based controller are presented for confirmation. The power factor corrector is with 250 W power rating, 100 V/AC/50 Hz input, and 385 V/DC output. Experimental results demonstrate the effectiveness of the proposed predictive digital-controlled PFC under boundary current mode control.

Abstract: A two-terminal current controller having a current limiting unit and an adjusting unit regulates a first current flowing through a load according to a load voltage. When the load voltage does not exceed a first voltage, the two-terminal current controller operates in a first mode for conducting a second current associated a rectified AC voltage, thereby limiting the first current to zero and adjusting the second current accordingly. When the load voltage is between the first voltage and a second voltage, the two-terminal current controller operates in a second mode for conducting the second current, thereby limiting the first current to zero and limiting the second current to a constant value larger than zero. When the load voltage exceeds the second voltage, the two-terminal current controller operates in a third mode for turning off the current limiting unit. The adjusting unit can adjust the predetermined value and the second voltage.

Abstract: This paper investigates dc voltage control strategies for output power smoothing of a fully rated converter-based wind turbine with energy storage device connected to the common dc link via a bidirectional dc/dc converter. Since the dc link voltage ripple reflects power oscillation, coordinated dc voltage control schemes are used for the ac network side converter and energy storage system to ensure that generated high-frequency power fluctuation is absorbed by the energy storage system, whereas the low-frequency components are transmitted to the connected ac network. Two methods have been proposed: one is based on proportional-integral (PI) voltage controller and low-pass filter with large time constant, and the other is based on PI with low natural frequency and droop controller with large droop gain. The detailed controller designs are described and system stability is assessed and shown to be stable. Both the MATLAB/Simulink simulations and experimental results are presented to demonstrate the effectiveness of the proposed methods for power smoothing.

Abstract: This study deals with an implementation of a constant speed permanent magnet synchronous generator (PMSG)-based three-phase stand-alone wind energy conversion system (SWECS). The voltage and frequency controller is realised using only a single voltage source converter (VSC) and a battery energy storage system (BESS). The BESS is used to provide load levelling under varying wind speeds and to control frequency of SWECS. The voltage of PMSG is regulated under varying wind speeds and loads by supplying the reactive power from VSC. The performance of SWECS is demonstrated as a load leveller, a load balancer, a harmonic compensator and a voltage and frequency controller.

Abstract: In general, partial power of the parallel ac/dc converter is processed only once and transferred directly. In order to keep the output voltage constant, the switching duty ratio in the parallel converter must vary with the line phase. It means that the operating point of the parallel ac/dc converter changes with the variation of input voltage, which would be a challenge for controller design. In this paper, the dynamic modeling of a single-stage single-switch parallel boost-flyback-flyback converter is developed by the linearization of its large-signal equations. To overcome the modeling uncertainty due to the variation of operating point, the feedback controller is designed based on the boundary of the mode to obtain zero steady-state error, fast rise time, and heavily damping within input voltage range. Both the derived dynamic modeling and the designed voltage controller are demonstrated by the provided simulation and experiment results.

Abstract: This paper deals with an adaptive control method to be used in the dc-link voltage controller of diesel-electric power supply units being arranged with both permanent-magnet generator and three-phase boost rectifier. The proposed control method is based on the suitable manipulation of the overall system transfer function to achieve an adaptive “closed-form” expression for the parameters of the dc-link voltage controller. Such an approach allows overcoming the inherent nonlinear behavior of the system, so that the overall system dynamic performance is not affected by the system load conditions. Moreover, a current feedforward technique based on the estimation of the load current will be introduced to improve the control stiffness to load unbalances.

Abstract: In this paper, a complete simulation model of a grid-connected single-phase two-stage photovoltaic (PV) system with associated controllers is presented. The simulation model is developed in PSCAD/EMTDC simulation program. The component models of the grid-connected PV system include a PV array, a dc-dc boost converter, a voltage source converter (VSC) and an LCL filter. Components of the LCL filter, the dc-link capacitor of the VSC and the inductor of the dc-dc boost converter are established theoretically and that are used in modelling the grid-connected PV system. The control architecture of the presented system incorporates a synchronous reference frame phase-locked-loop (s-PLL), a stationary frame current controller, a dc-link voltage controller, a dc-dc boost converter controller and a maximum power point tracking (MPPT) algorithm. Control design methodologies are described in detail. Simulation studies confirm that the modelling and control design approaches taken are robust and lead to a system with acceptable performance.

Abstract: A converter unit configured to couple to a photovoltaic panel (PV) may include a controller to sense an output voltage and output current produced by the photovoltaic panel, and manage the output voltage of a corresponding power converter coupled to a DC bus to regulate the resultant bus voltage to a point that reduces overall system losses, and removes non-idealities when the panels are series connected. The controller may also adapt to output condition constraints, and perform a combination of input voltage and output voltage management and regulation, including maximum power point tracking (MPPT) for the PV. The output voltage and output current characteristic of the power converter may be shaped to present a power gradient - which may be hysteretically controlled - to the DC bus to compel an inverter coupled to the DC bus to perform its own MPPT to hold the DC-bus voltage within a determinate desired operating range.

Abstract: This study presents a topology for a pulse width modulated (PWM) three-phase voltage regulator that uses only two driving switches, providing high reliability and making the switching stage simpler and cheaper compared with other available configurations. The proposed topology is suitable for voltage regulation on the distribution power system. It is able to regulate the steady-state voltage and to reject voltage variations such as flicker or sags caused by large motors start. In addition, the compensator features a topology free of energy storage elements. The PWM control is based on dc signals, asynchronous from the grid, simpler than the control used for traditional voltage source converters – it does not require a phase-locked loop, and does not involve trigonometric calculations. As a result of this, the controller can be achieved with an analogue controller or a low-cost microcontroller. The proof of concept is performed with a 220 V three-phase voltage regulator, which is simulated and prototyped in the laboratory.

Abstract: Exemplary embodiments are directed to a power controller A method may include comparing a summation voltage comprising a sum of an amplified error voltage and a reference voltage with an estimated voltage to generate a comparator output signal The method may also include generating a gate drive signal from the comparator output signal and filtering a signal coupled to a power stage to generate the estimated voltage

Abstract: Switching-mode power conversion system and method thereof. The system includes a primary winding configured to receive an input voltage, and a secondary winding coupled to the primary winding and configured to, with one or more first components, generate, at an output terminal, an output voltage and an output current. Additionally, the system includes an auxiliary winding coupled to the secondary winding and configured to, with one or more second components, generate, at a first terminal, a detected voltage. Moreover, the system includes an error amplifier configured to receive the detected voltage and a first reference voltage and generate an amplified voltage based on at least information associated with a difference between the detected voltage and the first reference voltage. Also, the system includes a compensation component configured to receive the amplified voltage and generate a second reference voltage based on at least information associated with the amplified voltage.

Abstract: This paper presents a robust system-oriented control design approach for distributed generation (DG) converters in microgrids. The conceptual design of the proposed interface is to provide control system robustness against system-level interactions without strict knowledge of complete microgrid system dynamics. To increase the robustness against converter-microgrid interactions, the microgrid system is modeled by a dynamic equivalent circuit, which might include uncertainties induced due to microgrid impedance variation and interactions with the equivalent microgrid bus-voltage. The equivalent microgrid model along with local load interactions and uncertainties are augmented with the DG interface power circuit model to develop a robust H∞ voltage controller. To account for power angle interaction dynamics, an angle feed-forward control approach is adopted, where the angle of the equivalent microgrid bus, as seen by each DG unit, is estimated and used for feed-forward control. Unlike conventional droop controllers, the proposed scheme yields two-degree-of-freedom controller, resulting in stable and smooth power sharing performance over a wide range for the static droop gain and also at different loading conditions. A theoretical analysis and comparative simulation and experimental results are presented to demonstrate the robustness and effectiveness of the proposed control scheme.

Abstract: An apparatus and method for compensating an image of a display device are disclosed. The image compensation apparatus of a display device comprises a scatterometer configured to analyze luminance of a display image according to a test initialization voltage and a test data voltage applied to a plurality of pixels and to measure a deviation of a threshold voltage of a driving transistor of the plurality of pixels; a voltage controller configured to divide the display panel into a predetermined area according to a deviation of a threshold voltage of the driving transistor and to calculate different initialization voltages that initialize driving of pixels included in the area on a predetermined area basis; and an initialization voltage supplier configured to apply a corresponding initialization voltage calculated in the voltage controller to the plurality of pixels included in the predetermined area.

Abstract: The subject matter of this application is embodied in an apparatus that includes a data processor, and at least one hardware monitor to measure circuit delays associated with the data processor and a power supply to provide power to the data processor. The apparatus also includes a voltage regulator to regulate a voltage level provided by the power supply, and a look-up table having target voltage values and target circuit delay values each corresponding to one or more conditions. The apparatus further includes a controller to control the voltage regulator. The controller at various time points controls the voltage regulator based on target voltage values obtained from the look-up table. In between the time points, the controller controls the voltage regulator based on differences between target circuit delay values and measured circuit delay values.

Abstract: A switching regulator includes a power stage and a controller. The power stage is operable to produce an output voltage. The controller is operable to set a duty cycle for the power stage based on feed-forward control so that the power stage produces the output voltage as a function of an input voltage and a reference voltage provided to the switching regulator. The controller is further operable to adjust the feed-forward control to counteract the effect of one or more nonlinearities of the switching regulator on the output voltage.

Abstract: At least one embodiment is directed to a semiconductor voltage controller comprising: a start-mode circuit associated with a start-mode; and an off-mode circuit associated with an off-mode, wherein the voltage controller is operable to receive a feedback signal and an off-mode signal from a single input and provide an output voltage, wherein the voltage controller is operable to be in the off-mode when the feedback signal is less than a skip level and the feedback signal is less than a HV control level, and wherein the voltage controller is operable to be in start mode when the feedback signal is greater than HV control level and Vcc is below a Vcc-start.

Abstract: This paper presents a comparative evaluation of four different multi-loop control schemes for a high-bandwidth AC power source. The power source considered in this work is based on a three-level T-type inverter with a two-stage LC output filter. The control schemes evaluated in this paper have an output voltage controller in the outer loop. For the inner control loop the following options are evaluated: capacitor current feedbacks, proportional-integral and proportional inverter output current control in combination with reference voltage and load current feedforward, and first LC stage capacitor voltage and inverter output current feedback.

Abstract: In this paper, we investigated the necessity and effects of optimal control methods in the stability and performance of a micro-grid that operates in islanded mode. The micro-gird is consisted of a combined heat and power (CHP), a capacitor bank (CB), photovoltaic panel (PV) as power generation sources. In addition, battery and the building electricity and thermal load are placed on the load side. A simple comprehensive model is assumed for each component of the micro-gird and the dynamic behavior of micro-grid voltage and frequency is studied in details. Since the micro-grid operates in islanded mode, the fluctuations in the building load act as disturbances and could cause the instability in the voltage and frequency. So it is necessary to design a controller to regulate the voltage and frequency. Particle swarm optimization (PSO) is used as a method to realize the optimal controller in the micro-grid. Simulation results showed the effects of proposed controller on the reduction of voltage and frequency fluctuations.