Voltage Reference Signal Research Articles

Multi Open-/Short-Circuit Fault-Tolerance Using Modified SVM Technique for Three-Level HANPC Converters

Open- and short-circuit faults are the most severe issues that affect the stability and reliability of power conversion systems. The space vector modulation (SVM) technique is widely used to control power converters. However, conventional SVM is incapable of controlling the system effectively when such faults occur. Considering these, this article proposes a modified SVM that is capable of tolerating the extreme cases of faults (including multi open-/short-circuit faults) simultaneously. An innovative fault tolerance method is proposed to tolerate multifaults in hybrid active neutral point converters (HANPCs). Furthermore, new voltage reference signals are created in addition to calculating voltage offset and inserting modified switching sequences. A descriptive performance analysis of the modified SVM technique is applied under healthy and faulty conditions. Correspondingly, the effects of the total harmonic distortion of the system performance are also highlighted and explained. The results reveal that the proposed control strategy can effectively maintain healthy and safe operation under faulty conditions without the need for additional parts or alteration of the topology configuration. In addition, the proposed method can be applied to HANPCs without special requirements to withstand high voltage levels. The effectiveness of the proposed method is verified by simulation and experimental results.

An efficient compensation of modified DSTATCOM for improving microgrid operation

This paper proposes a design for a modified distribution static compensator (DSTATCOM) with a proposed current controller for microgrid (MG) applications. The modified DSTATCOM is incorporated in a three-phase four-wire network system to deal accurately at grid connected mode with balanced, unbalanced and excursion load for both nonlinear and inductive loads. Moreover, it handles the stability issues of the MG at fault caused islanding incidents. The design criteria of the modified DSTATCOM parameters is presented and discussed. The hysteresis current controller is introduced to drive the voltage source converter (VSC) and its reference voltage signal is generated based on the instantaneous symmetrical components theory (ISCT). Matlab/Simulink software is used to verify the performance of the modified DSTATCOM with the proposed controller under different load types and loading conditions for grid connected mode and islanded mode of MG operation. Based on the simulation results, the power factor is improved and the non-linear harmonics currents are compensated therefore the harmonic distortion of the supply currents and voltage are reduced, moreover the stability operation at fault cause islanding is maintained. The results show the superiority of the proposed modification of DSTATCOM in dealing with unbalanced, distorted and bad power factor system in comparing with conventional DSTATCOM.

Lyapunov based harmonic compensation and charging with three phase shunt active power filter in electrical vehicle applications

With the increasing proliferation of high-tech loads and electrical vehicle (EV) charging stations, shunt active power filters (SAPFs) are contemplated to play a growingly substantial role in power distribution and delivery. In this regard, this paper proposes a Lyapunov based harmonic compensation and charging with the operation of three-phase SAPF as interface EV applications and the electric grid. The proposed control algorithm provides effective harmonics mitigation capability under various non-linear loads (NLLs) groups and grid disturbances. A noteworthy contribution of this paper is that a Lyapunov based proportional integral with anti-windup (PI with AW) control is proposed to regulate oscillations of the DC-link voltage without increasing DC-link capacitor size. The proposed control algorithm offers comprehensive solutions with several improvements, novelties and features as: (i) keeping the total harmonic distortion (THD) of source currents below recommended IEEE-519 limits, (ii) extraction of reference current and voltage signals based on Lyapunov estimator (LE) with effective and good harmonic rejection capability, (iii) achieving good dynamic performance with utilizing a Lyapunov based PI with AW control for the DC-link capacitor voltage and (iv) eliminating the necessity of any high-pass or low-pass filters with utilizing LE based orthogonal signal generation (OSG). Besides, comparative analyses with previous studies are handled to examine improvements provided by the proposed control algorithm. The feasibility and effectiveness of the proposed control algorithm are confirmed by PSCAD/EMTDC environment and DSP based PIL quasi-real time results.

Model-based processing for the estimation of space-charge distribution from non-contact pulsed electro-acoustic measurements

Estimating the space-charge distribution using the pulsed electro-acoustic method requires a calibration procedure, in which a reference voltage signal is measured and used to divide the output voltage signal of the piezoelectric sensor. Such a procedure is time consuming and generally involves manually setting filter parameters whose values should be chosen to reduce ringing artifacts in the charge profile and, at the same time, preserve the bandwidth of the profile. This paper proposes a model-based estimation method called the matrix pencil that does not require a calibration procedure to retrieve the charge distribution, albeit with normalized amplitudes, and thus it paves the way for reducing data acquisition and processing times. Results on simulated and experimental data confirm the effectiveness of the proposed method in estimating the space-charge distribution in irradiated polymers.

Parameterized and centralized secondary voltage control for autonomous microgrids

The paper presents a novel secondary voltage control scheme for autonomous microgrids. The proposed scheme is accomplished by a secondary voltage controller combined with a parameter decision modular. The secondary controller generates new voltage reference signals for Q-U droop control upon the operation statuses, and the parameter decision modular generates the regulation parameters for secondary voltage controller. Reactive power allocation coefficient is used to regulate output ratio of reactive power of DG units while reactive power weight is used to realize the rough-tuning for bus voltage and voltage weight for fine-tuning. Numerical simulation results show that the reactive power is shared accurately among DG units at the desired ratio and the voltage of any bus is restored with sufficient spare capacity by the proposed secondary scheme.

Performance Validation of PV System Incorporated ZSI-Dynamic Voltage Restorer for Long-Lasting Power Quality Improvement

Abstract A power distribution system’s main challenge is to provide consistent, reliable electricity to fulfill high demand. The incorporation of renewable energy sources into the utility grid system can be accomplished. However, renewable sources are intermittent in nature, and the loads work dynamically and cause imbalances to the system voltage within an immediate time frame. Intermittent renewable sources affect the voltage of the power grid system. Photovoltaic (PV) power generation with Z-source inverter (ZSI)–based dynamic voltage restorer (DVR) is used to avoid negative effects on the voltage. For step-up low direct current (dc) voltage to require alternating current voltage for the compensation of the voltage disturbance, ZSI with an energy storage impedance network is used. dc-dc converters connect the PV cell and the battery storage to the impedance source network. This article also incorporates an improved second-order generalized integrator (I-SOGI) control system for the generation of reference voltage signals. The I-SOGI control reference voltage generation approach greatly improves system performance and decreases the harmonic voltage. The voltage-related problems in the system connected to the utility grid are mitigated with DVR. In different load and source conditions, the PV generation with DVR performance is verified by the experimental prototype.

Development and Verification of Indirect Lightning-Induced Transient Protection Circuit for Avionics System

In this paper, an indirect lightning-induced transient protection circuit for avionics system is proposed, and its effectiveness is verified. The proposed circuit consists of a metal oxide varistor (MOV), a transient voltage suppression (TVS) diode, and a resistor. Compared with the conventional circuits (MOV or TVS diode), the improved noise suppression of the proposed circuit against indirect lightning strikes are experimentally verified in accordance with radio technical commission for aeronautics (RTCA) DO-160G Sec. 22. The highest attenuation levels of indirect lightning strike WF5A reference voltage and current signals are approximately 91.0% and approximately 98.4% for the input lightning signals, respectively.

An accurate digital converter for lossy capacitive sensors

This paper presents an incremental delta-sigma based capacitance-to-digital converter for lossy capacitive sensors. The proposed converter consists of a capacitance-to-voltage converter followed by a single-bit incremental delta-sigma converter. Unlike conventional incremental-delta sigma converter where a fixed reference voltage signal is utilized, the proposed converter utilizes a reference signal which depends on the amplitude and frequency of the input excitation signal. The generated reference signal for the incremental-delta sigma converter reduces the error in the capacitance measurement due to variation in the excitation signal frequency and amplitude. In addition, the proposed converter utilizes a frequency-independent quadrature phase shifter circuit for the generation of reference π/2 phase-shifted signal for the phase-sensitive detection operation. Moreover, a modified clock counting approach is utilized to measure the sensor capacitance accurately. A prototype of the proposed circuit is fabricated using commercial off-the-shelf components and tested. The experimental results demonstrate that the circuit is able to measure the sensor capacitor in the range from 20 pF to 163 pF. The worst-case error in sensor capacitance measurement was less than 0.2%. Furthermore, the proposed converter experimentally provides a signal-to-noise ratio of 56.66 dB.

Phase shift control and controller area network assisted proportional resonant control for grid integration of single phase voltage source inverters

Grid integration of inverters using renewable sources of energy is essential for providing a secure and clean source of power supply. Many techniques developed so far control the grid current to realize the regulation of power flow to the power grid. However, implementation of communication assisted synchronization methods for single-phase full-bridge inverters is not found to be discussed in the literature. The focus of this research is to conceptualize, simulate, and implement two control techniques, namely Phase Shift Control (PSC) and Controller Area Network Assisted Proportional Resonant Control (CANAPRC) for single-phase inverters. In the PSC method, the inverter injects the desired real power into the grid by controlling the phase angle between converter and grid voltages. A low complexity synchronization procedure was adopted using single-phase PLL to generate a reference voltage signal using the PSC method. In contrast, the CANAPRC method outputs a current reference created by the resonant controller using a communication network. The inverter can pump the required real and reactive power to the grid with reduced harmonics, enhanced power-sharing and transient stability using the two strategies. Simulations in MATLAB R2016a analyze the two models out effectively. Prototype models validate the proposed control strategies.

WITHDRAWN: Performance analysis of SRF-based UPQC on polluted electric utility grid

The effectiveness of the UPQC is determined by its control algorithm for generating the reference signal. In this paper, the reference signal generation is based on SRF (Synchronous Reference Frame) algorithm in a UPQC (Unified Power Quality Conditioner). The detailed SRF algorithm with a generation of the reference voltage and current signal are analyzed and implemented using MALAB/Simulink. Secondary distribution power system was created in MALAB/Simulink to analyses the performance of the UPQC before and after connection. The performance UPQC is examined with steady and dynamic conditions and the remarks of SRF algorithm have been concluded.

A Fast-Dynamic Control Scheme for a Power-Electronics-Based PV Emulator

The dynamic performance of a photovoltaic (PV) emulator is critical for testing applications with fast maximum power point tracking (MPPT) algorithms. In this article, a power-electronics-based PV emulator (PVE) is proposed to achieve fast-dynamic response, as well as, to emulate accurately in all regions of the current-voltage (I-V) characteristic curve. The control scheme of the proposed PVE consists of an instantaneous output impedance matching (IOIM) controller based on load resistance feedback to generate the voltage reference signal and an inner boundary control (BC) scheme to regulate the converter at a given reference within a short period of time. The IOIM controller overcomes the drawback of conventional PVEs that suffer from oscillating reference signal in a certain region of the I-V characteristic curve. Moreover, use of load resistance feedback in the reference generation algorithm allows the decoupling of the reference signal generator from the inner control loop. The BC scheme adapts a corrected second-order switching surface to achieve a faster response time and robust operation with switching converter loads. Detailed small signal model of the PVE is derived to design the IOIM control loop and to ensure a stable and fast convergent emulation in the entire I-V characteristic curve. Experimental results of a 130 W (VMPP = 35.2 V, IMPP = 3.69 A) prototype are presented with both resistive loads and an MPPT converter to verify its performance under fast varying irradiance and load conditions.

A Simple Zero-Sequence Voltage Injection Method for Carrier-Based Pulsewidth Modulation of the Three-Level NPC Inverter

This article proposes a simple zero-sequence voltagei injection method for the carrier-based pulsewidth modulation (CBPWM) of the three-level neutral-point-clamped (NPC) inverter. The injected zero-sequence voltage signal is simply determined by comparing the three reference voltage signals and the dc-link capacitor voltages, respectively. Theoretical analyses show that the CBPWM with the proposed method can balance the dc-link capacitor voltages and eliminate/reduce the ripples of the dc-link capacitor voltages of the NPC inverter. Compared with other CBPWM schemes, the CBPWM with the proposed method has lower computation cost, does not need the information of the three-phase currents, and can reduce the switching loss of the NPC inverter. The CBPWM with the proposed zero-sequence voltage injection method and its superiority is validated experimentally in comparison with existing CBPWM schemes. The proposed method works in both inverter and rectifier modes, which is validated by simulation results.

RETRACTED: Artificial ecosystem-based optimization for optimal tuning of robust PID controllers in AVR systems with limited value of excitation voltage

This paper presents an application of a novel optimization method called Artificial Ecosystem-Based Optimization (AEO) to determine the optimal design parameters of the proportional-integral-derivative (PID) controller for an automatic voltage regulator (AVR) system. Unlike the previous studies presented in the literature, the proposed method takes into account the excitation voltage limit and therefore formulates a new objective function for optimal PID parameters design. The practical aspect of the proposed constraint is significant since the generator field winding can be seriously damaged in case of the large excitation voltage. The performance of the proposed controller using the solution methodology proposed in this study and its contribution to the robustness of the control system are investigated. Further, the obtained PID parameters are used to simulate the AVR dynamics for a large step change in the generator’s voltage set-point. Besides, the obtained step responses have been compared with the corresponding responses of the AVR system whose PID parameters are determined by using well-known methods presented in the literature. Also, the proposed AEO-PID controller shows superior performances in the case of uncertainties in the AVR system’s parameters, as well as in the presence of the different disturbances in the system. The results obtained show that the obtained parameters provided a more secure and stable machine operation even with changes of the reference, generator, or excitation voltage signals compared with the performance of the controllers obtained by the previous works presented in the literature. Furthermore, AEO has proven its ability to get optimal solutions in a fast and efficient manner in terms of accuracy and time spent per iteration.

Implementation of solar PV system unified ZSI-based dynamic voltage restorer with U-SOGI control scheme for power quality improvement

The main challenge in today's power system is to supply continuous, reliable power and satisfy the high demand. The incorporation of renewable energy sources into the utility grid system can be accomplished. However, the renewable sources are intermittent in nature and the loads work dynamically and cause imbalances to the system voltage within an immediate time. Intermittent renewable sources affect the voltage of the power grid system. Photovoltaic (PV) power generation with Z-source inverter (ZSI)-based dynamic voltage restorer (DVR) is used to avoid that. For step-up low DC voltage to required AC voltage for the compensation of the voltage disturbance, ZSI with the energy storage impedance network is used. DC-DC converters connect the PV cell and the battery storage to the impedance source network. This article also incorporates an upgraded second-order generalized integrator (U-SOGI) control system for the generation of reference voltage signals. The U-SOGI control reference voltage generation approach greatly improves system performance and decreases the harmonic voltage. The voltage-related problems in the system connected to the utility grid are mitigated with DVR. In different load and source conditions, the PV generation with DVR performance is verified by the digital simulation and experimental prototype.

Specifying the Waveforms for the Calibration of CISPR 16-1-1 Measuring Receivers

Ensuring the measuring receiver's compliance with the specifications given in CISPR 16-1-1 is mandatory. This is achieved through traceable calibration of the instrument regarding its standard requirements. Incidentally, the receiver's response to pulses of the weighting detectors is the most challenging aspect that must be calibrated. The calibration method requires generating broadband pulses of a given impulse area and at certain repetition frequencies. Such pulses must deliver a known quasi-peak level and have a flat spectrum over the frequency band under consideration. Although the standard states the tolerable uncertainties for the pulse characteristics, it does not stipulate their exact waveform. This void is significant because it hinders the reproducibility of the calibration method, forbids to completely describe the CISPR 16-1-1 pulse generator, and truncates the traceability chain. This paper proposes a parametric model for pulsed waveforms that are compliant with the requirements established for the calibration of the receivers’ response to pulses. The model is numerically solved and evaluated for producing a waveform vector that can be transformed into a reference voltage signal using arbitrary function generators. The validity of the proposed waveforms is experimentally verified in terms of its time domain characteristics and its frequency spectrum.

Dynamic Voltage Restorer for Mid Point Compensation using Transformer Less Inverter using Solar PV System

The process of electrical phenomenon primarily based Dynamic voltage restoration for a one section of the transmission line voltage dip is presented an unique technique to observe and make amends for the single part where the voltage dips is formed, simulated using advanced simulation techniques. The pre-sag alternative methods are utilized on top of proposed management. Within the aforementioned management technique the proposed where a reference voltage signal is produced matching normal voltage magnitude as well as the frequency Once the proposed restorer is operated with the system, then reference signal’s phase will be synchronised with the voltage as this system considers the error if it is a voltage dip. Thus the ability circuit within the voltage restorer produces an amendment of a wave shape to compensate the dip. Circuit components and hence the feedback circuit is discussed.

A Novel MPPT Technique for Single Stage Grid-Connected PV Systems: T4S

In this paper, a novel maximum power point tracking (MPPT) technique, which has been named T4S (a technique based on the proper setting of the sign of the slope of the photovoltaic voltage reference signal), is presented and discussed. It is specifically designed with reference to a single-stage grid-connected PV system. Its performance is numerically compared with that of the well-known and widely used perturb and observe (P&O) MPPT technique. The results of the numerical simulations confirm the validity of the proposed MPPT technique which exhibited a slightly better performance, under stationary and also time-varying irradiance conditions. In addition, the T4S technique is characterized by the following features: it does not require explicit power detection or calculation and, moreover, it allows the tracking of the maximum average power injected into the grid rather than the tracking of the maximum instantaneous power extracted by the PV source.

Energy Considerations for Tracking in DC to DC Power Converters

A design of an adaptive controller applied to the boost and buck-boost converters to deal with the problem of tracking a sinusoidal voltage is proposed. The main contribution is to provide conditions on the design procedure in order to obtain a reduction in the DC voltage (offset of the sinusoidal signal) of the reference signal; in this way the AC energy is maximized. A nonlinear stable system is designed in order to produce the necessary inputs to exactly track the inductor reference current, which is a necessary condition to achieve the tracking behavior of the voltage reference signal ft=A+Bsin⁡(wt). A numerical example is provided to corroborate the result.

New Fault-Tolerant Control Strategy of Five-Phase Induction Motor with Four-Phase and Three-Phase Modes of Operation

The developed torque with minimum oscillations is one of the difficulties faced when designing drive systems. High ripple torque contents result in fluctuations and acoustic noise that impact the life of a drive system. A multiphase machine can offer a better alternative to a conventional three-phase machine in faulty situations by reducing the number of interruptions in industrial operation. This paper proposes a unique fault-tolerant control strategy for a five-phase induction motor. The paper considers a variable-voltage, variable-frequency control five-phase induction motor in one- and two-phase open circuit faults. The four-phase and three-phase operation modes for these faults are utilized with a modified voltage reference signal. The suggested remedial strategy is the method for compensating a faulty open phase of the machine through a modified reference signal. A modified voltage reference signal can be efficiently executed by a carrier-based pulse width modulation (PWM) system. A test bench for the execution of the fault-tolerant control strategy of the motor drive system is presented in detail along with the experimental results.

Power Electronic Converter Based PMSG Emulator: A Testbed for Renewable Energy Experiments

This paper presents a converter-based permanent magnet synchronous generator (PMSG) emulator as a testbed for designing, analyzing, and testing of the generator's power electronic interface and its control system. The PMSG model is formulated in a real-time digital simulator. A voltage type ideal transformer model combined with a virtual impedance is presented as an interface algorithm. The design procedure and implementation of the virtual impedance in a simulation platform is discussed. A six-switch voltage source converter is used as a power amplifier to mimic the behavior of the PMSG supplying linear and nonlinear loads. A proportional–integral plus resonant controller is proposed as a voltage loop controller for tracking a distorted output voltage reference signal. The accuracy of the proposed emulator is investigated for the fundamental and low-order voltage harmonics. Technical challenges of the PMSG emulator are considered and proper solutions are suggested. The performance of the proposed emulator is compared with an actual PMSG.