The active power filter has been proved to be an effective method to mitigate harmonic currents generated by nonlinear loads as well as to compensate reactive power. The methods of harmonic current detection play a crucial part in the performance of active power filter (APF). This paper presents a new control strategy in which two shunt active power filter configurations are developed in order to define new simple control algorithm which requires minimum number of currentmeasurements. The effectiveness of the proposed control strategies are demonstrated through results. The proposed systems are implemented with MATLAB/SIMULINK. The simulation results are presented for two control strategies and comparison is made among them.
Different analytical methods for the leakage inductance of transformer calculation have been compared. It has been shown that the energy method is the most accurate one. Although the image method is accurate and convenient, it depends on the current of the image conductors. These results are compared by practical measurements for three types of transformers: small single-phase transformer, three-phase distribution transformers and a high voltage test transformer.
A platform for emulating 64 Phasor Measurement Units (PMUs), with data from a real-time simulation, has been developed. An RTDS simulator has been used to provide IEC 61850-9-2 Sampled Value data, representing three-phase voltage and currentmeasurements from up to 64 power system locations, and the platform efficiently processes the data using cost-effective ARM-based devices, which output synchrophasor data according to the IEEE C37.118.2 protocol. The platform provides flexibility to configure the PMU class and reporting rate at run-time. The paper analyses the measured report latency of the PMUs under a variety of configurations. This development provides a cost-effective system for demonstrating wide-area visualisation, control, and protection schemes.
A radial-basis-function NN for fault detection in induction motors was developed by Wu and Chow . The inputs to the system are represented by four-feature vectors extracted from the power spectrum of the vibration signals of the machine. This system was able to detect both mechanical and electrical faults, and also the subsequent development of the mechanical faults. Here, the four-feature vectors were total power average frequency , and normalised variance and skewness of vibration measurements. Good rates of detection were claimed by the authors for frequencies in the range 40 – 60 Hz. The seeded electrical fault was a stator inter-turn short circuit created by the addition of a resistor across one phase which changed the electromagnetic force on the stator. Unfortunately the simulated fault differed considerably from the actual vibration signals produced by real stator winding inter- turn short circuits.
Power is measured in ac systems using wattmeters. A modern digital sampling wattmeter, such as any of the Tektronix power analyzers, multiplies instantaneous samples of voltage and current together to calculate instantaneous watts and then takes an average of the instantaneous watts over one cycle to display the true power. A wattmeter will provide accurate measurements of true power, apparent power, volt-amperes reactive, power factor, harmonics and many others over a broad range of wave shapes, frequencies and power factor. In order for the power analyzer to give good results, you must be able to correctly identify the wiring configuration and connect the analyzer's wattmeters correctly.
Paolo Attilio Pegoraro (M06) received the M.S. (summa cum laude) degree in telecommunications engineering and the Ph.D. degree in electronic and telecommunications engineering from the University of Padova, Padua, Italy, in 2001 and 2005, respec- tively. From 2015 to 20018, he was an Assistant Pro- fessor with the Department of Electrical and Elec- tronic Engineering, University of Cagliari, Cagliari, Italy, where he is currently Associate Professor. He has authored or co-authored over 80 scientific papers. His current research interests include the de- velopment of new measurement techniques for modern power networks, with attention to synchronized measurements and state estimation for distribution grids. Dr. Pegoraro is a member of the IEEE Instrumentation and Measurement Society and of its TC 39 (Measurements in Power Systems).
as ,a function of log N gt versus log in Fig. 6.1. An appreciable entrance effect is apparent. In Fig. 6.2 the single phase air data were crossplotted as N versus the number of equivalent diameters of inter connection lengthy (L/B). The air turbulent mixing data and water tur bulent mixing data overlap to form a continuous curve. This was expected since the Schmidt numbers for air and water are approximately equal. An exponential decrease in N was found for increasing L/D in Fig. 6.2. This effect is believed to be due to two factors. The first is the high initial mass transfer rate as the concentration profile is being developed. This is analogous to entrance effects in heat transfer, for example when the heat transfer coefficient is very high in the case of a cold fluid entering a channel with a high uniform temperature. The second factor is the increased turbulence when the two fluid streams meet at the up stream edge of the interconnection length.
Three-phase diode rectifiers are widely used as the front-ends of industrial ac drives. These types of loads introduce harmonic currents into the networks, which have odd orders: 6n ± 1(n = 1, 2, 3 . . .) of the fundamental frequency. Since these harmonic currents cause serious problems and deteriorate the power quality of the distribution networks, the shunt APF was developed to compensate those harmonic currents and consequently to improve the power quality. As illustrated in Fig. 1, a shunt APF is basically a threephase voltage source inverter (VSI) connected in parallel with a nonlinear load at the point of common coupling through an inductor LF . The energy storage of the APF is a large capacitor located at the dc-link side of the inverter. The nonlinear load can be presented as a RL or RLC load connected to the power supply through a three-phase diode rectifier as shown in Fig.1.As stated earlier, the APF must generate the harmonic currents to compensate harmonics produced by the nonlinear load and to make the supply currents sinusoidal. To fulfill these demands, the traditional control scheme requires a harmonic detector and current controller where both loops must be designed properly to achieve good control performance. However, it may cause excessive complexity in the design process.
The increasing use of nonlinear loads such as adjustable speed drives, electric arc welders and switching power supplies cause’s large amounts of harmonic currents injects in to distribution system. LC passive filters are traditionally utilized to compensate the harmonic currents since they are simple and low cost solution. However, they are often large and heavy. In contrast, shunt active power filter purpose is to generate harmonic currents having the same magnitude and opposite phase with the harmonics produced by the nonlinear load and to ensure the supply currents contains only fundamental component. Adopting the advantage of indirect current control schemes i.e., absence of harmonic detector, this paper proposes an advanced control strategy to enhance the APF performance. In the proposed control scheme the supply currents are directly measured and regulated to be sinusoidal by an effective harmonic compensator, which is developed based on a PI and VPI controllers and implemented in the fundamental reference frame. In place of PI and VPI controller a new controller implemented with ANN technique applied as current controller for threephase Shunt Active Power Filter then THD will be further reduced and dynamic response of the system also reduced.
As the oil, gas and water must be mixed evenly ac- cording to the certain percentage during the experiments, some equipments are very important in the system such as the oil and water mixing tank, the air compressor sup- plying certain amount of gas, and the static mixer mixing the three-phase fluid. The amount of the oil and water can be measured before they are mixed in the mixing tank, and the gas will be measured by the standard gas meter before mixing with the oil-water two phase flows in the static mixer. In order to reduce the pulse interfer- ence of the fluid, oil-water mixed fluid and gas must be regulated by the steady regulator devices. Transparent pipes are installed in the pipeline system so as to observe the flow pattern of the fluid in real time. There are more than fourteen flow control valves installed in the pipeline system, so we can change the ways and directions of the mixed fluid whenever it is needed. The three-phase flow must be precipitated, separated and recycled after the experiments.
Mehl and Barbi proposed a method to improve the power factor of a threephase diode based bridge rectifier with the three IGBT based Bi-directional switchesThese switches operated at low frequency and each bi- directional switch is turn on when corresponding phase voltage crosses Zero volt and conduct for 1/12 th of line voltage cycle. The circuit features are low cost, simplicity, and high power applications. The converter requires a connection to the neutral wire of the ac system and due to that connection a pulsed current is present on the neutral. It was also noticed is the circuit the energy stored by the inductor is responsible for increment high voltage stress across the switches during commutation of switches  
A capacitor connected on the DC side of the VSC acts as a DC voltage source. A small active power is drawn from the line to keep the capacitor charged and to provide transformer and VSC losses, so that the injected voltage Vs is practically 90 degrees out of phase with current I. In the control system block diagram Vd_conv and Vq_conv designate the components of converter voltage Vq_conv which are respectively in phase and in quadrature with current.
Abstract —Voltage source inverters are essential devices to integrate renewable energy sources to the main grid and control the injection of real and reactive power. Due to their inherent nonlinear dynamics, the stability and particularly the current limitation of power controlled inverters represent challenging tasks under grid variations or unrealistic power demands. In this paper, using the synchronously rotating dq transformation, a nonlinear current limiting controller is proposed for three- phase inverters connected to the grid through an LCL filter. The proposed controller introduces a cascaded control structure with inner current and voltage control loops and an outer power controller that includes a droop function to support the grid and rigorously guarantee a limit for the grid currents. Using nonlinear closed-loop system analysis and based on input-to-state stability theory, the limits for the d- and q-axis grid currents are proven independently from each other without adding any saturation units into the system that can lead to instability. Extensive simulation results of the proposed nonlinear current- limiting controller are provided to demonstrate its effectiveness and current-limiting property.
voltage harmonics in threephase system was introduced in this paper. Wide use of non-linear load, results in current harmonics causes frequent problems such as overheating of building wiring, overheating of transformer units and failure in electronics equipment. The desired aim is to reduce current and voltage harmonics to improve the power quality. A new filter having a combination of PI and Fuzzy controllers which eliminates maximum amount of harmonics.
Turbulent interchange rates between two adjacent triangular subchannels were measured for single phase air, single phase water and two-phase air-water flows. The subchannels were physically separated, except in the mixing section, by a O.OO6 inch stainless steel strip. Initially a 9 inch and then an I8 inch by 0.04 inch wide slot were cut into the stainless steel strip. Methane was employed as the air tracer and potassium nitrate (KIIO^) as the water tracer. A gas chromatograph and an atomic absorption unit were used for gas and liquid analyses respectively.
A modern microgrid should be able to operate either connected or disconnected from the main grid; it should have two major modes: grid-connected mode and island mode. In grid- connected mode, the system is a lot easier to control and protect since it’s relatively small in terms of scale. Critical demand-supply balance becomes a challenge of operating the Microgrid in island mode since the voltage and frequency of the system must be maintained at 208 V and 60 Hz. Hence, it requires an elegant approach to run the solar system tests with it isolated from the infinite bus. Figure 17 shows the wiring diagram to test the system with a synchronous generator. It consists of a DC motor starter, a DC motor, a synchronous generator, power rheostat, a Yokogawa power meter, 2 circuit breaker modules, a 3-phase Wye-connected
Abstract- A novel threephase asymmetric Multilevel Inverter with series H-bridges is proposed. The proposed topology is based on a cascaded connection of H- bridges to generate more levels at the output side of voltage by using different voltages of DC source voltages on both sides of the inverter. This topology is used to generate all positive, negative and zero levels by using a lower number of IGBT’s, DC sources and controlling circuit parameters that leads to lower THD, reduction in installation space, cost of inverter is low, reduced radio frequency interface(RFI) and increasing the life of inverter also. It reduces not only switching network such as power electronic components, and also reduces the blocked voltages at each IGBT. An Asymmetric cascaded MLI uses different magnitudes of voltages that leads to the more number of levels at the output as compared to that of the Symmetric cascaded multi level inverter[MLI]. The performance of A novel threephase asymmetric MLI with series H-bridges have been verified by using threephase MLI of MATLAB/SIMULINK.
Space Vector PWM technique is an algorithm to control PWM pulses for three-phase alternating voltage generation with the purpose of reducing total harmonic distortion with high efficiency. If a three-phase power converter which is expected to produce voltage on AC side is in accordance with reference voltage, the reference signal is expressed by space vector with transformation abc- αβ. From the transformation result, duty cycle for every state combination of switch S a , S b , S c is determined.
Harmonic analysis of Front End Current (FEC) of threephase single switch boost converter to reduce the total harmonic distortion (THD), active switching & passive filters are incorporated in this work. A constant frequency switching is used for active filtering & pulse width modulation (PWM) technique is used to regulate the output voltage. Power factor improvement is accomplished by using PWM technique and passive LC high frequency harmonics filters. An Electro Magnetic Interference (EMI) filter is used to suppress the high frequency component generated by the active switching. Moreover, a series LC filter resonating with the supply frequency is also used to suppress the low frequency value could be made less than 3%, which is a great improvement over the earlier rectifiers that have only EMI filter. In the earlier types of rectifiers, the THD value was as high as 17%. The efficiency of the module is also studied. As the output voltage has the nonlinear relation with duty cycle, the efficiency is also nonlinear with output voltage variation. But up to certain range of duty cycle it could be made linear in nature with output voltage. The efficiency versus duty cycle and THD versus duty cycle curve for the proposed rectifier circuit is given for a clear understanding of the model.