Source Voltage Fluctuations Research Articles

Solar Assisted Relift Luo Converter with UPQC for Voltage Unbalance Mitigation Using DDSRF Theory

The upsurge seen in integration of sensitive non-linear loads and Photovoltaic (PV) system based power generation has strengthened the demand for enhanced Power Quality (PQ) in distributed power system. Thereby, a Unified Power Quality Conditioner (UPQC), which is a custom power device is proposed in this work for improving the PQ of the overall network. The load side PQ issues is mitigated using the shunt compensator, while the source side PQ issues is mitigated using the series compensator of the UPQC. The active power to the load is provided from the PV system through a shunt compensator. The voltage level of the output obtained from the PV is improved with the aid of Re-lift Luo converter, which is a DC-DC converter of high efficiency and voltage gain. Moreover, in order to provide a stabilized voltage supply to the UPQC, an Adaptive Proportional Integral (PI) controller is selected and its gains are adjusted with the application of Fuzzy Logic Controller (FLC). The Decoupled Double Synchronous Reference Frame (DDSRF) theory is applied to derive the reference voltage and reference current for balancing source voltage variations and load current harmonics, respectively. The series and shunt compensators are controlled using Cascaded Type-2 FLC (CT2FLC). The effectiveness of the proposed PV-UPQC configuration in eliminating load current harmonics and source voltage fluctuations is evaluated on the basis of MATLAB simulations.

The Effect Of Source Voltage Fluctuation on Ilumination Decrease In Bandles, Led Lights, and Energy Saving Lights

The fluctuating source voltage causes the distributed voltage not to have a nominal value of 220V and affects the characteristics of the lighting. In this study, observations were made on the change in source voltage of the three types of lighting during peak load times. The purpose of this research is to show that any change in the source voltage (PLN) can affect the lifetime of the light bulb. From the results of research on one of the LED lights, when 0 hours is turned on, the source voltage is at 227.0 volts with 108.4 Lux lamp illumination. When 12 hours are turned on, the source voltage is 225.9 Volts with 103.3 Lux lamp illumination. There was a decrease in source voltage of 1.1 Volt and a decrease in illumination of 5.1 Lux. And when 24 hours the lamp is turned on, the source voltage is at 230 Volt with 97.8 Lux lamp illumination. There was an increase in source voltage of 4.1 Volt and a decrease in illumination of 5.5 Lux. As a result of frequent increases in source voltage, the lamp lifetime will decrease more rapidly.

Analysis of a Sliding Mode DC–DC Boost Converter Through LPRS of a Nonlinear Plant

An exact analysis of sliding mode boost converter dynamics based on the locus of a perturbed relay system (LPRS) method is presented in this article. An LPRS representation of the dc–dc boost converter based on a full nonlinear model is developed. This is a first known attempt to apply the LPRS concept to an industrial process having a nonlinear model. The frequency and amplitude of the self-excited oscillations (chattering/ripple) are analyzed through the LPRS method. The LPRS is also used to analyze the effect of the propagation of an external disturbance (fluctuations in the source voltage). It is found that the effect of source voltage fluctuations on the system dynamics can be attributed to a combination of the effects of amplitude modulation and input signal propagation. Further, LPRS is used in the design problem of the dc–dc boost converter prototype to determine the required controller hysteresis value which ensures the desired operating switching frequency. Simulation and experimental results are presented to validate and illustrate the theoretical analysis.

Total Harmonic Distortion and Output Current Optimization Method of Inductive Power Transfer System for Power Loss Reduction

Inductive power transfer (IPT) system is widely used in material handling. A typical structure of the system takes an H-bridge inverter with an inductor-capacitor-inductor (LCL) resonant filter to realize a constant track current supplying changeless energy to the second side. However, the output voltage total harmonic distortion (THD) of the inverter increases, which causes the increase of output current circulation, when using voltage width control method to eliminate source voltage fluctuating. Therefore, a two-stage converter is proposed to optimize the output current circulation. The two-stage IPT system is composed of a boost converter cascaded with an H-bridge resonant inverter. The boost converter is employed to provide a higher and stable DC bus voltage. The H-bridge resonant inverter operates in a fixed width with a constant switching frequency. With the proposed topology, the THD of the high frequency voltage maintains the minimum value to realize minimum output current circulation in the LCL filter. The soft switching is realized to reduce the losses. Furthermore, expressions of coil and track model are presented by combining the theoretical analysis and finite element analysis (FEA). The experimental results show that over 76.6% efficiency is demonstrated in conditions of an 800 W load at the 14% source voltage fluctuation and the maximum efficiency was 78.6 %. The range of efficiency variation was 2% compared to a full-bridge system with voltage pluse-width control of which was 4.6%.

Analysis of a sliding mode boost converter under fluctuating input source voltage, using LPRS method

DC/DC converters require a controller that ensures high performance under the variations of load and source voltage, ensuring stability and a fast transient response at all operating points. This paper provides a detailed analysis of the dynamics of sliding mode boost converter using the locus of a perturbed relay system (LPRS) method. LPRS allows for an exact determination of the amplitude and the frequency of the output voltage oscillations as well as the equivalent gain. Furthermore, it describes the external signal propagation through the system. Analysis of the effect of the source voltage fluctuations on the output voltage waveform is presented in the paper as analysis of exogenous disturbance propagation. The mathematical analysis is verified through simulations and hardware experiments.

Adaptive tuning algorithm for single‐phase Z‐source inverters

This study proposes an adaptive tuning algorithm for dynamic adjustment of the saturation limits for the shoot-through duty ratio (STDR) and modulation index of a Z-source inverter. This adaptive tuning is crucial in Z-source inverter applications where wide fluctuations in dc source voltage are expected. Even though a standalone application is chosen here to demonstrate the validity of an adaptive tuning algorithm, the proposed algorithm is equally valid for other applications using Z-source inverter based topologies also. The effects of non-idealities on dc-link voltage and ac output voltages are investigated, and STDR expressions for which the dc-link voltage is maximal are derived. Subsequently, these expressions are utilised to define the saturation limit of the STDR in the proposed adaptive tuning algorithm. The transient phenomenon of state-switching behaviour in a Z-source inverter under closed-loop operation is analysed for different perturbed conditions. A laboratory prototype of a 250 VA single-phase Z-source inverter is built to demonstrate the proposed adaptive tuning algorithm. The proposed algorithm and associated control laws are implemented using a dsPIC30f6010 microcontroller. The effectiveness of the closed-loop controlled single-phase Z-source inverter system is tested with linear and non-linear loads. The measured results are in close agreement with analytical investigations.

LPRS analysis of sliding mode buck converter

DC-DC buck (step-down) converters are widely used in various power systems. An exact analysis of buck converter dynamics based on the locus of a perturbed relay system (LPRS) is proposed. Beside conventional analysis tasks – determination of the frequency and amplitude of the self-excited oscillations (chattering), which characterize ripple of the converter output signal - analysis of the propagation of source voltage fluctuations is presented. The latter is conveniently done through the same LPRS method. The results are supported by simulations with the use of the conventional model of the converter.

Rectifier Capacitor Filter Stress Analysis When Subject to Regular Voltage Fluctuations

Lamp flicker levels that arise as a result of voltage fluctuations can exceed limits set by appropriate standards. New lamp types such as compact fluorescent lights are less sensitive to voltage fluctuations as their flicker characteristics are considerably different compared to those of the traditional incandescent lamp. These differences could support the moderation of the present voltage fluctuation and flicker standards and hence the associated limits. The potential detrimental effects on electrical equipment which may be caused by relaxation of these limits should be investigated before any changes to the present standards take place. The impact of voltage fluctuations on a full-bridge rectifier with a capacitor filter is considered as a case study in this paper. Such a circuit is found at the front end of many different types of equipment that are connected to the public ac supply network. The capacitor ripple current characteristic is of particular interest. The research reported in this paper indicates that the filter capacitor will accumulate and dissipate increased amount of charge when the rectifier is subjected to ac source voltage fluctuations. The consequence is that the RMS value of the capacitor current will increase, where the magnitude of this increase is related to the modulation frequency and magnitude of the fluctuating voltage. Therefore, an ac supply with a voltage fluctuation component will cause a full-bridge rectifier with capacitor filter to sustain increased stress. This stress may accelerate the capacitor ageing process, eventually resulting in premature equipment failure. The research indicates that there is a need for indices other that the short-term and long-term flicker indices required for equipment compatibility levels.

Six-switch converter fed sensorless three-phase IM drive for home appliances

Abstract In this paper, a single-phase to three-phase converter is proposed to provide variable output voltage and frequency. The proposed topology employs only six IGBT switches, which form the front-end rectifier and the output inverter for the one step conversion from single-phase supply to output three-phase supply. The front-end rectifier permits bidirectional power flow and provides excellent regulation against fluctuations in source voltage. Moreover, it incorporates active input current shaping feature. An easy method to implement control strategy is proposed. This control strategy ensures nearly unity input power factor with sinusoidal input current over the operating range. Based on sensorless vector control technique, the proposed converter is used for the speed control of the three-phase induction motor. A low cost motor drive can be achieved using the proposed converter and control technique. Simulation and experimental results are carried out to analyse and explore the characteristics of the low cost drive system.

Single-to-three phase induction motor sensorless drive system

This paper presented a single to three-phase induction motor drive system to provide variable output voltage and frequency. The proposed drive system employs only six IGBT switches, which form the front-end rectifier and the output inverter for the one step conversion from single-phase supply to output three-phase supply. The front-end rectifier permits bidirectional power flow and provides excellent regulation against fluctuations in source voltage. Moreover, it incorporates active input current shaping feature. The control strategy of the proposed drive system of three-phase induction motor is based on speed sensorless vector control technique. A low cost of motor drive and much more advantages can be achieved using the proposed drive system. Simulation and experimental results are carried out to analysis and explore the characteristics of the proposed drive system.

Impact of voltage fluctuation on dose delivery of BJ-6B accelerator

Objective To study the impact of main source voltage fluctuation on dose rate and dose delivery accuracy of BJ-6B accelerator. Methods The accelerator was calibrated by a voltage regulator at an output voltage of 332 V. The main source voltage fluctuation was simulated by changing the output of voltage regulator within the range of 321 - 338 V. The change of dose rate was recorded. Using a water phantom, each absorption dose was measured five times and averaged along the central beam axis at the depth of 1.5 cm, 5 cm and 10 cm, respectively, with the conditions of monitor unit: 100 MU ,field: 10 cm× 10 cm and SSD = 100 cm. The impact of voltage fluctuation on dose rate and dose delivery of BJ-6B accelerator was analyzed. Results Voltage fluctuation had an significant effect on dose rate. In a certain range, dose rate and absorption dose at different depths increased as the output voltage increased. Conclusions It is essential to equip the BJ-6B accelerator with a high accurate voltage stabilizer, and the voltage stabilizer must be adjusted to its highest accuracy. Key words: Voltage; Dose rate; Dose accuracy

Determination of Flicker Transfer Coefficients Near Large Synchronous Generators

Large disturbing loads such as electric arc furnaces (EAF) create fluctuations in source voltage at the point of common coupling (PCC). These voltage fluctuations then propagate throughout the power system with varying degrees of attenuation. The amount of attenuation is, in general, a function of system impedance and load composition, and can be characterized by what is known as a flicker transfer coefficient. The frequency response of synchronous generators near 60 Hz has a significant effect on flicker propagation, particularly in networked HV or EHV systems. To date, information available in the literature has not adequately described this phenomenon from a theoretical perspective or shown how to take this affect into consideration when computing flicker transfer coefficients. The following paper addresses these issues by: 1) providing a formal description of a synchronous generator model that can be used to determine flicker transfer coefficients when traditional modeling methods may not be appropriate and 2) providing a novel way of calculating flicker transfer coefficients using the described machine model. Synchronized flicker measurements, made at an EAF installation and nearby generating facility in the Southern Company service area, were used to validate the results of the proposed method.

Design of a Compact Series-Connected AC Voltage Regulator With an Improved Control Algorithm

This letter presents an improved control algorithm for the compensation of ac source voltage fluctuation. The proposed idea can be used to regulate both the overvoltage and undervoltage situations with only unidirectional energy transmission. Theoretical analysis has been achieved based on the power flow theory. A case study is demonstrated by means of a prototype experiment to prove its performance and effectiveness.

A new single-phase to three-phase converter with active input current shaping for low cost AC motor drives

A single-phase-to-three-phase converter for a low-cost AC motor drive is proposed. The converter employs only six switches and incorporates a front-end half-bridge active rectifier structure that provides the DC link with an active input current shaping feature, which results in sinusoidal input current at close to unity power factor. The front-end rectifier in the converter permits bidirectional power flow and provides for excellent regulation against fluctuations in source voltage, facilitating regenerative braking of the AC motor drive. A control strategy that maintains a near-unity power factor over the full operating range and is easy to implement is described. Suitable design guides for the selection of filter components are presented. Simulation and experimental results that verify the developed theoretical models are also presented. >

交流電気鉄道における三相側無効電力補償による電源電圧変動の抑制

交流電気鉄道における三相側無効電力補償による電源電圧変動の抑制

A high-frequency off-line SMR converter with improved performance characteristics

A novel offline high-frequency switch-mode rectifier (SMR) converter topology is presented. This topology allows the safe use of lossless single-capacitor switch snubbers from zero to rated load power variation. To ensure the safe and lossless operation of the high-frequency stage under all operating conditions, the inverter stage is analyzed in detail and expressions are derived for the snubber capacitor voltage as a function of the high-frequency transformer leakage and magnetizing inductances, operating frequency, and the charging time of the snubber capacitors. The effect of AC source voltage fluctuations on the input power factor is also analyzed for the front-end half-controlled bridge rectifier. The theoretical results have been verified experimentally. >

Analysis of the Effect of Source Voltage Fluctuations on the Power Factor in Three-Phase Controlled Rectifiers

The effect of source voltage fluctuations on the harmonics and the power factor is analyzed for a six-pulse line-commutated converter. Exact expressions are derived for currents in the filter network and the ac supply lines as a function of the size of a series inductor in the LC type low-pass filter connected to a resistive load. The harmonics are calculated according to a method which is unorthodox in power engineering and which is based on the convolution theorem. Switching functions required for the discontinuous conduction mode are derived from time-domain analysis. The method is applicable to a wide class of switching networks.

Adaptive Harmonic Control in PWM Inverters with Fluctuating Input Voltage

New techniques of harmonic reduction and voltage regulation in PWM inverters with fluctuating input voltage are described. A novel selective harmonic reduction technique is also developed for three-phase full-bridge inverters to reduce the number of switchings per output cycle. For keeping the fundamental load voltage at the present value and suppressing the generation of low-order harmonics when the input voltage fluctuates, the conventional sinusoidal reference of the triangulation method is replaced by a quasi-sinewave whose magnitude varies inversely with the input voltage to keep the product of the reference voltage and the input voltage sinusoidal. Harmonic analysis of the W-type modulation and M-type modulation is given to show that the load voltage spectra of the output waveforms generated with the proposed methods are insensitive to the source voltage fluctuation and load variation. Experimental results confirm the theoretical analysis.

Wide-Range and High Efficiency Switching Power Supply for Color TV Receivers

In TV receivers with semiconductors, regulated power supplies are necessary to keep reliable operation of the receivers, against both the source voltage fluctuation and load variation. Generally its regulated DC output voltage is constrained around 100V by a horizontal output transistor rating.

Integrated circuit measurement of skin conductance

An active skin-conductance measuring device, utilizing integrated circuit operational amplifiers, is described. The transducer offers accurate measurement despite fluctuations in source voltage. The circuit also provides protection in case of accidental short circuit.