A few research results have been suggested that employ the dc-link voltage control strategies by the generator-side converter instead of the GSC. Wind generator has been extensively used both in independent systems for power supplying remote loads and in grid-connected application. The WG power production can be mechanically proscribed by altering the blade pitch angle. This topology is based on the WG optimal power versus the rotating-speed feature, which is frequently stored in a microcontroller memory. The WG turning speed is calculated; the optimal output power is intended and compared to the actual wind generator output power. The ensuing error is used to manage a power boundary. In a similar edition create in the WG output power is calculated and the target rotor speed for optimal power generation is resulting from the WG optimal power versus rotor-speed characteristic.
independent comparator in hysteresiscontroller. The logic condition for six inverter switches is chosen by the output of the comparator. When the phase “a” current is smaller than (i*- Δi), where Δi is the hysteresis band, the output of the comparator is “1”, the “a” phase will be connected with the positive track of DC link. In contrast, if the phase “a” current is bigger than (i*- Δi), the output of the comparator will become “0”, and the “a” phase will connected to the negative track of DC bus. The similar procedures are applied on other legs. With the hysteresiscontroller, the phase current control within the hysteresis band. The phase currents are approximately sinusoidal in steady state. The smaller the hysteresis band, the more closely do the phase currents represent sine wave but implied a high switching frequency which is a practical limitation of the power device and increased inverter losses. In this experimental, ±0.1 hysteresis band are chosen.
Now days many industrial applications which require electrical drive demand precise speed and torque control, to increase production quality. More ever proper control of these drives using modern control schemes also improves systems efficiency. For application requiring precise control previously DC drives preferred because of their inherent ability to give independent speed and torque control. But these drives have higher maintenance costs because of brush and commutator construction.
Pulse-Width Modulation (SPWM) where the inverter switching function is independent of the instantaneous line current and the inverter harmonics can be obtained from the switching function harmonics. As in most PWM applications the interval between two consecutive switching actions varies constantly within a power frequency cycle. It means that the switching frequency is not constant but varies in time with operation point and conditions. In principle increasing inverter operation frequency helps to get a better compensating waveform. However there are device limitations and increasing the switching frequency cause increasing switching losses, audible noise and EMF related problems. The range of frequencies used is based on a compromise between these two different factors. In this paper, the control of switching frequency is realized by introducing a hysteresis band current control algorithm. The main aim of this study is to reduce the THD of supply current and switching frequency of APF. The hysteresis band currentcontroller changes the hysteresis bandwidth as a function of reference compensator current variation to optimize switching frequency and THD of supply current. In this paper, the synchronous d-q-0 reference frame theory is first briefly reviewed. Next, the proposed hysteresis band current control based compensation strategy for the three-phase active power filter is described. Then, simulation results are presented followed by the conclusion.
Abstract- The Distributed generated system originated due to the demand of electrical energy and keen scarcity of conventional energy sources. The main problem is the harmonization of the DG to the utility grid. Usually, for synchronizing the utility grid with DG source current regulated PWM voltage-source inverters (VSI) are used in order to meet the following objectives: 1) To improve grid stability 2) To control active and reactive power through voltage and frequency control 3) Improvement of power quality, etc. By using Fuzzy with hysteresiscontroller enhancement of power quality is made by diminishing current error at higher band width. This system is modeled and simulated in the MATLAB/Simulink model and the results obtained are compared with conventional hysteresiscontroller.
The synchronous reference frame theory is one of the methods in time-domain based reference current generation techniques. Important characteristic of this theory is the simplicity of the calculations, which involves only algebraic calculation. The d-q transformation output signals depend on the load currents (fundamental and harmonic frequency components) and the performance of the phase locked loop. The PLL circuit is providing sinθ and cosθ for synchronization. It performs the operation in steady-state or transient state as well as for generic voltage and current waveforms. The reference frame transformation is formulated from a three-phase abc stationary system to the direct axis (d) and quadratic axis (q) rotating coordinate system .Park’s Transformation and Clarke’s Transformation are used to decouple the active and reactive components (4). Park’s Transformation is used to simplify the computational complexity by converting the three phase components into equivalent two phase components (5).
purpose needs an enormous knowledge transfer capability for its execution and acknowledgment. this needs a massive selection within the duty cycle and at some purpose prompts changeless brake down of the static gadgets. Use of ANN procedure are produce over the foremost recent number of years for usage of energy electronic converters with less transmission capability. PWM in lightweight of ANN cannot unravel the current system. analysis have likewise been ill-used within the field of state house vector tweak for checking the connection of ANN based mostly strategy. one in every of the difficulty looked by the bulk of the specialist is that the preparation of each individual node for a non-direct management strategy. This paper uses the idea of two point based trajectories to confine the non-linearity sub net for every individual hub has been embraced for preparing of way on choice of factors to be received while exchanging the cloud information.
P.G. Student, Department of EEE, Info Institute of Engineering, Coimbatore, Tamil Nadu, India 1,3 Assistant Professor, Department of EEE, Info Institute of Engineering, Coimbatore, Tamil Nadu, India 2 ABSTRACT: This paper presents complete analysis, to compare and elevate the performance of two control strategies. By using Fuzzy controller, the tracking reference currents of shunt active filters under balanced, un- balanced and non-sinusoidal conditions. There are two control methods one is instantaneous real active and reactive power method (p-q), another one is active and reactive current method (id-iq) which are widely used in active filters. For both (p-q) and (Id-Iq) methods used for different voltage conditions with fuzzy controller. The Simulation results confirm the performance of active and reactive current control strategy (id-iq) more than active and reactive power control strategy (p-q) with fuzzy controller. Variable frequency drives (VFDs), electronic ballasts, battery chargers, static var compensators are installed, and the problems related to harmonics are expected to get inferior. Due to excellent harmonic compensation, the result Active power filter (APF) gains much more attention. In different control strategies, the performance of the active filter seems to be in contradictions.
should be minimum at start-up and should increase gradually as the motor speeds up. Increasing the level of the voltage source should be done automatically. This alternative is realized through the use of a controlled full wave rectifier (AC-DC converter). The position of firing angle of the rectifier should be decided by a closed loop controller. The input to the controller should be the motor speed. The job of the controller is to have a high value of firing angle at start-up and decreasing it gradually as the motor speeds up. The firing angle should reach and stick to zero value as the motor reaches steady state conditions.
This paper has evaluated six different PWM techniques namely Single PWM, Multiple PWM, Sinusoidal PWM, Selected harmonic Elimination PWM, Hysteresis Band current control PWM and Space Vector PWM . The paper has provided a thorough review of the each technique with a special focus on the operation of single and three phase inverter which will be implemented digitally in Phase-II. In this paper, Simulink models for all six techniques have been developed and tested in the MATLAB/Simulink environment. The report discusses the advantages and drawbacks of each technique.
evaluation of shunt active power filter(SAPF) for power quality improvement. Power quality complications can be take up using SAPF. A Simulation model of the three-phase shunt active filter had been implemented based on IRP theory The system where we can observe the considerable Improvement in the source current in the norms of total Harmonic distortion (THD) of source current. We can also Observe the correction in the). Properties are restored in the terms of source voltage and Source current are in phase by this implementation. The performance of the SAPF by using the IRP theory for nonlinear load is demonstrated with the MATLAB simulation results.
In the vector control scheme, torque control can be carried out by suitable regulation of the stator current vector; this implies that accurate speed control depends on how well the current vector is regulated. In high-per- formance vector drives, a current-control loop, with a considerably high bandwidth, is necessary to ensure ac- curate current tracking, to shorten the transient period as much as possible and to force the voltage source inverter (VSI) to equivalently act as a current source amplifier within the current loop bandwidth. In this work, a hys- teresis-band current controlled VSI is used. This control- ler will generate the reference currents with the inverter within a range which is fixed by the width of the band gap. In this controller the desired current of a given phase
Microgrid is the small grid which consists of the large number of micro sources. These micro sources are the source of energy mainly the renewable energy sources. The main purpose of this project is to connect the microgrid with the main utility grid. In this paper the micro grid will work in synchronism with the utility grid. The power supplied to the loads is via main utility grid as well as by microgrid as per the demand of the loads. If the load increases than the extra power is supplied by the main grid. When the intentional islanding takes place or due to any other power quality issues than the microsources have to generate extra power to fulfill the demand of the local loads all these conditions are analyzed and shown with the help of MATLAB on simulink. Keywords: Microgrid, Photovoltaic, SPWM, HysteresisCurrent
The notch filter is a very simple method allowing the APF's current reference extraction without need to active/reactive power or any complicated calculations. In this paper Hysteresis and fuzzy logic controller are implemented. Hysteresis control PWM is basically an instantaneous feedback current control method of PWM where the actual current continually tracks the command current within a hysteresis band. The design of a control able to pursue current peaks isn't straightforward. But, this difficulty has been overwhelmed by the introduction of fuzzy logic in power electronic field.
source is helpful part in electrical power generation. The renewable energy source is interface to point of common coupling (PCC), because of increase electrical power generation. In this case we are interface renewable energy source to grid to full fill the demand. This paper presents Static Compensator (STATCOM) with Interfacing wind energy source (WES) modelled in the MATLAB SIMULINK toolbox for the mitigation of the power quality issues in the distribution system. STATCOM is one of the custom power device used in distribution system for power conditioning. STATCOM is developed for the compensating reactive power demanded by non-linear and unbalanced load. Also power factor of the source is improved and the Total Harmonic Distortion in the source currents is reduced. STATCOM can correct voltage harmonics by injecting the reactive current into the system. Instantaneous reactive power theory is used for obtaining reference source current for controlling STATCOM. The performance of the STATCOM by using the IRP theory for unbalanced and nonlinear load is demonstrated with the MATLAB simulation results.
Comparing the techniques for calculating the reference voltage of the series compensator, presented above, it can be concluded that the UPQC-P algorithm has the simplest implementation (it involves very little computation). In the UPQC-P case the voltage rating of the series compensator is considerably reduced. Also, the UPQC-Q compensation technique does not work in the case when the load is purely resistive. Therefore, the UPQC-P control strategy has been used in the UPQC simulation model. PI controller has been used for dc link voltage control in the UPQC simulation model.
In the past, dc motors were used in areas where variable speed operation was required, since their flux and torque could be easily controlled by the field and the armature current. Separately excited dc motors have been used extensively due to their fast response and good four quadrant operation with high performance at near zero speeds. However, their complex construction means that dc motors are expensive to maintain. Squirrel cage induction motors are ideal for traction applications. They have a simple and rugged structure, high reliability and robustness and low maintenance. High performance control of induction machines requires fast transient response and good energy efficiency. Torque control in ac machines is achieved in ac motors by controlling the motor currents, just like in dc motors. However, in ac machines, both phase angle and magnitude of the current need to be controlled. Unlike in dc machines, the dynamic system in ac machines is nonlinear and the flux and torque producing currents are not orthogonal. Thus, these quantities need to be decoupled before independent control of torque and flux can be employed. Vector control and direct torque control techniques are employed to accomplish this task.
The power electronics converters such as single phase, three phase rectifier based on diode, thyristor devices and adjustable speed drives and arc furnaces induces the harmonics, reactive current in electric power system. It is well-known fact that harmonics and reactive current do not have any contribution to real power flow and need to be compensated to enhance power quality. In general, current harmonics are responsible for low efficiency, poor power factor, torque pulsation and interference with nearby communication line. To eliminate harmonics and compensate reactive power requirement of the nonlinear load shunt active power filter has been widely studied. The shunt active power filter is also known as DSTATCOM. The DSTATCOM is one of the custom power device used for compensation of harmonics and reactive power requirement of the load. Interesting features of DSTATCOM is that it can mitigate the harmonic and reactive currents by injecting equal but out of phase harmonic currents [3-5].
The conventional DTC of PMSM has received considerable investigation for its advantage of quick change of torque, robustness and simplicity . However, only six valid voltage vectors are available in conventional DTC which induce such problems as large torque ripple and variable switching frequency . Hence the space vector modulation -direct torque control (SVM-DTC) was presented in which the along with hysteresis control of torque and stator flux hysteresiscontroller in conventional DTC, reference voltage calculator and space vector modulation unit are used. The SVM-DTC can provide constant switching frequency and more accurate Stator flux and torque control.
This paper presents variable hysteresiscurrent control technique to reduce harmonic present at input and output side of rectifier under unbalance input impedances. Whether ever unbalance input impedances present high quality of input currents and output DC voltage are obtained. Here variable bandwidth of hysteresiscurrentcontroller is used to track line current of all the three phases independently.