Novel Control Method for Dynamic Voltage Regulator

Control strategy affects directly the working performances of dynamic voltage regulator （DVR）. One-cycle control is an effective nonlinear signal modulation control method. In this paper, a new one-cycle control scheme for DVR was proposed in single phase supply system. On the basis of principle analysis, the corresponding one-cycle control model for DVR was built up, which is characterized by simple control circuits, good control performance, and high control precision. As an example, a control model for single-phase DVR was simulated by using Matlab/Simulink and SimPowerSystem. The results show that the load voltage could be compensated quickly at the points of supply voltage stepping down and up, and the relative error was less than 4% in the whole voltage sag process. Both theory analysis and simulation results show that the new one-cycle control scheme for DVR is effective.

ODFF: Optimized Dual Fuzzy Flow Controller Based Voltage Sag Compensation for SMES-Based DVR in Power Quality Applications

The booming electronics itself carries an impact on power quality. Superconducting Magnetic Energy Storage (SMES) is proposed to enhance power quality in three-phase systems under various loads. This paper aimed to compensate the voltage sags under various faults in the grid systems. The SMES is selected as an energy storage unit to improve the capability of voltage sag compensation. Optimized Dual Fuzzy Flow (ODFF) logic controller is designed to prevent the voltage sag time during excessive phase voltage variation. Hence the proposed controller strategy reduces the total harmonic distortion during various fault conditions. To regulate the contribution of active power, the least possible value is improved using ODFF. The depth of voltage sags compensation is achieved by the over modulation and an iterative loop is designed in the control block. While protecting sensitive loads from voltage disturbances, and sags initiated by the power system, the proposed configuration is advantageous for an industrial implementation. It is found that the proposed method can result in more than 50% additional sag support time when compared with the previous methods such as PI and PSO. Utilizing MATLAB Simulink, compensation of sag and minimization of THD is established, and the simulation tests are performed to evaluate the performance of the proposed control method.

Distributed Cooperative Secondary Voltage Control in an Unbalanced Microgrid

The negative-sequence reactive power-conductance(Q^(−)-G) droop control strategy is a conventional method to compensate for the output unbalanced voltages in an islanded MG.Nevertheless, the conflict between unbalanced voltage compensation and negative-sequence reactive power sharing, caused bythe impedance mismatching of distribution lines and distributedgenerators, has not been solved only by Q^(−)-G droop control.In this paper, a distributed cooperative secondary unbalancedvoltage control strategy is proposed to decrease the outputvoltage unbalance factor (VUF) of each droop-controlled DG,as well as to further enhance the negative-sequence reactivepower sharing effectiveness among DGs by properly shiftingup and down the Q^(−)-G droop characteristics of each DG.An algorithm for adaptive VUF weight coefficient is proposedto better suppress VUF under severe imbalance conditions.Furthermore, a negative-sequence small-signal model of an MGunder an unbalanced condition, considering the communicationdelay time of the proposed SUVC, is established to analyze thesystem’s stability and transient performance under the influenceof some critical parameters. Finally, the effectiveness of theproposed strategy is validated by the simulation results froma real-time emulator of StarSim HIL.

Curvature Compensated CMOS Bandgap Reference with Novel Process Variation Calibration Technique

A lowtemperature coefficient（ TC） bandgap reference（ BGR） with novel process variation calibration technique is proposed in this paper. This proposed calibration technique compensating both TC and output value of BGR achieves fine adjustment step towards the reference voltage,while keeping optimal TC by utilizing large resistance to help layout match. The high-order curvature compensation realized by poly and p-diffusion resistors is introduced into the design to guarantee the temperature characteristic. Implemented in 180 nm technology,the proposed BGR has been simulated to have a power supply rejection ratio（ PSRR） of 91 dB@100 Hz. The calibration technique covers output voltage scope of 0. 49 V-0. 56 Vwith TC of 9. 45 × 10^（-6）/℃-9. 56 × 10^（-6）/℃ over the temperature range of-40 ℃-120 ℃. The designed BGR provides a reference voltage of 500 mV,with measured TC of 10. 1 × 10^（-6）/℃.

Fault Ride Through Strategy of DFIG Using Rotor Voltage Direct Compensation Control Under Voltage Phase Angle Jump

Wind power has developed rapidly in recent years,and large-scale wind power facilities connected to power grids will bring many new challenges.Some new operation charac-teristics of power grids with doubly-fed induction generator(DFIG)may exhibit,for example voltage phase angle jumps(VPAJ).VPAJ can negatively impact the fault ride through(FRT)performance of DFIG.This paper firstly investigates the physical mechanism and the operation characteristics of DFIG with VPAJ.It is noted that the current control strategies designed for voltage amplitude changes are not suitable for VPAJ.Secondly,the paper develops an FRT optimization control strategy under VPAJ which optimizes the DFIG operation characteristics.Finally,simulations of a 250 MW wind farm are presented which validate the proposed FRT strategy.

Voltage Unbalance Compensation in Distribution Feeders Using Soft Open Points

Soft open points(SOPs)are power electronic devices that may replace conventional normally-open points in distribution networks.They can be used for active power flow control,reactive power compensation,fault isolation,and service restoration through network reconfiguration with enhanced operation flexibility and grid resiliency.Due to unbalanced loading conditions,the voltage unbalance issue,as a common problem in distribution networks,has negative impacts on distribution network operation.In this paper,a control strategy of voltage unbalance compensation for feeders using SOPs is proposed.With the power flow control,three-phase current is regulated simultaneously to mitigate the unbalanced voltage between neighboring feeders where SOPs are installed.Feeder voltage unbalance and current unbalance among three phases are compensated with the injection of negative-sequence and zero-sequence current from SOPs.Especially in response to power outages,three-phase voltage of isolated loads is regulated to be balanced by the control of SOPs connected to the feeders under faults,even if the loads are unbalanced.A MATLAB/Simulink model of the IEEE 13-bus test feeder with an SOP across feeder ends is implemented,and experimental tests on a hardware-in-the-loop platform are implemented to validate the effectiveness of the proposed control strategy.

A novel sourceline voltage compensation circuit for embedded NOR flash memory

A novel sourceline voltage compensation circuit for program operation in embedded flash memory is presented. With the sourceline voltage compensation circuit, the charge pump can modulate the output voltage according to the number of cells to be programmed with data ＂0＂. So the IR drop on the sourceline decoding path is compensated, and a stable sourceline voltage can be obtained. In order to reduce the power dissipation in program operation, a bit-inversion program circuit is adopted. By using the bit-inversion program circuit, the cells programmed to data ＂0＂ are limited to half of the bits of a write data word, thus power dissipation in program operation is greatly reduced. A 1.8-V 8 × 64-kbits embedded NOR flash memory employing the two circuits has been integrated using a GSMC 0.18-μm 4-poly 4-metal CMOS process.

Overview of control,integration and energy management of microgrids

Microgrids are being developed as a building block for future smart grid system.Key issues for the control and operation of microgrid include integration technologies and energy management schemes.This paper presents an overview of grid integration and energy management strategies of microgrids.It covers a review of power electronics interface topologies for different types of distributed generation(DG)units in a microgrid,a discussion of energy management strategies,as well as the DG interfacing converter control schemes.Considering the intermittent nature of many renewable energy based DG units,the ancillary services of DGs using the available interfacing converter rating are also discussed in the paper.

A wideband RF amplifier for satellite tuners

This paper presents the design and measured performance ofa wideband amplifier for a direct conversion satellite tuner. It is composed of a wideband low noise amplifier （LNA） and a two-stage RF variable gain amplifier （VGA） with linear gain in dB and temperature compensation schemes. To meet the system linearity requirement, an improved distortion compensation technique and a bypass mode are applied on the LNA to deal with the large input signal. Wideband matching is achieved by resistive feedback and an off-chip LC-ladder matching network. A large gain control range （over 80 dB） is achieved by the VGA with process voltage and temperature compensation and dB linearization. In total, the amplifier consumes up to 26 mA current from a 3.3 V power supply. It is fabricated in a 0.35μm SiGe BiCMOS technology and occupies a silicon area of 0.25 mm^2.

A low-phase-noise LC-VCO with an enhanced-Q varactor for use in a high-sensitivity GNSS receiver

An LC-VCO with an enhanced quality factor（Q） varactor for use in a high-sensitivity GNSS receiver is presented.An enhanced A-MOS varactor is composed of two accumulation-mode MOS（A-MOS） varactors and two bias voltages,which show the improved Q and linearization capacitance-voltage（C-V） curve.The VCO gain（K_（vco）） is compensated by a digital switched varactors array（DSVA） over entire sub-bands.Based on the characteristics of an A-MOS,the varactor in a DSVA is a high Q fixed capacitor as it is switched off,and a moderate Q tuning varactor when it is switched on,which keeps the maximal Q for the LC-tank.The proposed circuit is fabricated in a 0.18μm 1P6M CMOS process.The measured phase noise is better than -122 dBc/Hz at a 1 MHz offset while the measured tuning range is 58.2%and the variation of K_（VCO） is close to±21%over the whole of the sub-bands and the effective range of the control voltage.The proposed VCO dissipates less than 5.4 mW over the whole operating range from a 1.8 V supply.