Harmonic Analysis : Harmonic Suppression Techniques

Modelling of the series transformer, VSC and LC filter is presented in this section. A time-varying threephase

It is observed that the power factor is maintained closer to unity when the input voltage is reduced from 230V to 110Vrms. Figure 11 (a) and (b) shows the power factor correction of controller for various load condition such as 20% (60W) and 75% (230W). The power factor for the system is found to be 0.84 for light load condition and 0.99 for full load condition. The THD of input current at full load with predominant third and fifth harmonic components are shown in Figure 12(a) and (b).Third harmonics is found to be 4.8% and fifth harmonic component is 4.9% which are well within IEC 61000-3-2 standard during wide range of load variations. The variation in power factor with load is shown graphically in Figure 13(a). It can be inferred from the graph that improved resettable control operates at high power factor for all load condition whereas the conventional PI control has poor power factor under light load conditions. Figure 13(b) shows the comparison between the efficiency of the converter for varying load conditions with the conventional control method and the resettable integrator control. The converter’s efficiency is maintained at 92% for light load conditions and 96% for fully loaded condition with integrator control technique. Thus the improved resettable integrator controller provides a very simple and reliable solution for power factor correction and

In a healthy individual hormones are secreted through the hypothalamus and pituitary gland and are regulated through negative feedback. Normally the hormone cortisol would cause secretion of CRH and ACTH. When CRH secretion is low ACTH secretion is also low which leads to lower cortisol secretion. Since we know that the patients tumor is secreting excess cortisol we can determine that the hormone levels will be different. Negative feedback would usually keep the hormone levels within a stable range but we know that the tumor is not responding to negative feedback which means more ACTH and CRH is going to be secreted. This increase is hormone levels will cause more cortisol to be secreted.

The impact of the proposed sequences has been simulated for 0.4 modulation index with a 0.5 lagging power factor load (power factor angle 60°). The simulation setup consists of the following software: 1) MATLAB/Simulink – used to implement the modulation strategies and switching sequences, and 2) PSIM – used to simulate the T-NPC inverter running with an R-L load and to provide conduction and switching losses of each switch. The inverter switching pulses were generated within Simulink and were fed to PSIM through sim-coupler module which provides a link between PSIM and simulink for the purpose of co-simulation [29].

The DVR is one of the most common and effective solutions for protecting critical load against voltage sags [10] [11]. The DVR is a power electronic device used to inject three-phase voltages in series and in synchronism with the distribution feeder voltages in order to compensate for voltage sags. Moreover, it can be efficiently used to augment the fault ride through capability in wind applications. Detection time is an important factor in the voltage restitution process. Fast detection

Since the beginning, people have requested that Majestic Transformers create or fabricate a broad range of rectifier power supplies to distribute as a part of their application. Some of these units are as simple as fitting a bridge rectifier onto the output winding of a single phase or three phase transformer, while others are complicated. They involve using variable transformers, meters, line insulation monitors, and smoothing circuits ranging up to 7000A and injecting a current into railway conduction rail systems for testing, up to 5kV for running and testing high voltage

The innovative inverter technology produces safe, smooth power, protecting your sensitive electronics (computers, smartphones, etc.) from damage.

Measuring the power quality it requires the network system voltage within their limits, as the non linear loads increasing .Effects of Harmonic on power quality and the efficiency. In power system , harmonics are the multiples frequencies . when we apply pure sinusoidal wave form of

However, renewable energy sources have been used in so many countries to reduce CO2 emissions and provide sustainable electrical power. The power electronic interface between a renewable energy source and the grid can be used to control reactive power output and hence the network voltage as well as curtailing real power output, and so enable the generator to respond to the requirements of the grid.

In a research article [9], the frequency response characteristics of the system can be altered when the harmonic distortion levels are not within the acceptable limits through changing sizes or locations of the capacitor, by changing source characteristics, or by design a harmonic filter. Filters are the most common solution as it can provide reactive power support at the fundamental frequency and a low impedance path for one or more harmonic current components to flow. The filter elements must be specifically designed to withstand the harmonic components along with the fundamental frequency voltages and currents. Common method for filter design is by utilizing one single-tuned shunt filter first, designed for the lowest generated harmonic (typically 5th) and it is advisable to use capacitors with a higher voltage rating than the system. Determine the voltage distortion level at the bus. The commonly applied limit of 5% (total harmonic distortion – THD) was presented in IEEE Standard 519-1981. If required, determine if the harmonic current levels meet IEEE Standard 519-1992. If not, there may be a need for multiple filters (i.e., 5th and 7th). Vary the filter elements according to the specified tolerances and check its effectiveness. Lastly, by checking the frequency response characteristic to verify that the newly created parallel resonance is not close to a generated harmonic frequency (i.e., the 7th harmonic filter may create a new 5th harmonic resonance).

Alexander B. Nassif and Jing Yong [7] have proposed a method to identify the consumers generating inter harmonic frequencies. The inter-harmonics can be measured by means of Impedance based approach applied at the metering point. The main idea is that, the inter-harmonic impedance of the system is much smaller than that of an inter-harmonic generating load. This method can identify the source of each inter-harmonic component without having to rely solely on the active power measurement and requires only an approximate value for the inter-harmonic impedance measured at the metering point.

The development of power electronic converters is marked by demands for a simultaneous reduction in Size , losses and power related costs. Historically diode bridge rectifiers with a laSrge capacitor at the dc bus have been used to convert the ac voltage to a dc voltage. But diode bridge rectifiers draw a very high peak current from the ac utility, which is rich in harmonics and thus gives a very poor power factor. Modern AC-DC power supplies utilize power factor correction in order to minimize the harmonics in the input current drawn fiom the utility. The Boost topology is the most popular topology used for power factor correction today. In this paper, power factor correction using boost converters in single phase diode bridge rectifiers is presented.

Feed forward control is a reliable for rejecting fast and dynamic voltage disturbances in the phase grid. Mainly in this scheme implemented in phase voltages of the Wyes connected configuration. Under this unbalanced and distorted grid conditions, the online conversion of line - to - line values into the phase value is unworkable. In order to an exploit full advantages of feed forward controller is a most appropriate modulator is needed. In this article the feed forward of grid line-to-line voltages is used in phase voltages. The introduced feed forward method is implemented in Implicit Zero Sequence Discontinuous Pulse Width Modulation (IZDPWM) technique that is compatible for grid connected inverters. Regarding in the IZDPWM grid topologies distorted the harmonics of the grid voltages. Hence, a sinusoidal current is injected to the grid. Moreover, the measuring grid line-to-line voltages two sensors are required; hence an overall system costs is reduced and control system reliability is increased. The time-domain simulations in MATLAB/Simulink and experimental results from a Hardware based laboratory prototypes are in good agreements,

Index Terms— Double fed induction generator, diode clamped multilevel matrix converters, grid, matrix Converter, space vector pulse width modulation technique, wind turbine.

For emolument of current harmonics (if any), the instantaneous resoluteness of different active and reactive powers is utilized - the active and reactive powers are computed utilizing p-q theory. No restrictions are imposed on the voltage or current wave forms, and it can be applied to three-phase systems with or without a neutral wire for three-phase generic voltage and current wave forms. Thus, it is valid not only in steady state, but withal in transient states.