Ripple reduction and power quality improvement in photovoltaic and wind integration using hybrid intelligent nonlinear control with a shunt active power filter

This paper deals with the steady state analysis of unified power quality conditioner (UPQC). The UPQC, a combination of shunt and series active power filter (APF), is one of the best solutions towards the mitigation of voltage sags and swells problems on distribution network. The mathematical analysis is based on active and reactive power flow through the shunt and series APF, wherein series APF can absorb or deliver the active power whereas the reactive power requirement is totally handled by shunt APF alone during all conditions. The derived relationship between source current and % of sag/swell variation shows shunt APF plays an important role in maintaining the overall power balance in the entire network. The digital simulation is carried out to verify the analysis done. The simulation results support the mathematical analysis. The effect of load VAR variation and the impact of % sag/swell on the kVA ratings of both shunt and series APF are also analyzed. This analysis can be very useful for selection of device ratings for both shunt and series APFs

An ideal AC power transmission is pure sinusoidal, both its voltage and its current. With the increasing production of modern industry, more and more power electronic equipments are used and cause serious current distortion because of open and close of power electronic devices. Harmonic, a measurement of distorted degree of voltage or current, reflects the deviation from sinusoidal wave. Another cause of harmonic is nonlinear loads such as Arc furnaces and transformers. The widely using of nonlinear load brings much harmonic current to transmission lines. The harmonic current passes through transmission lines and causes harmonic voltage exert on the loads in other place(Terciyanli et al. 2011). As a result, the loss of power transmission is increased and the safety of power grid is seriously weakened. With the fast development of modern production, the harmonic in power grid become more and more serious and people pay more attention to how to eliminate harmonic(wen et al. 2010). Active Power Filter (APF) is a promising tool to cut down the influence of harmonics, shunt APF for harmonic current, series APF for harmonic voltage. Unified Power Quality Conditioner (UPQC), consisted of shunt APF and series APF, is effective to reduce both harmonic voltage and harmonic current. Now, UPQC is mainly used in low-voltage lowcapacity applications. But with the development of power system, more and more highpower nonlinear loads are connected to higher voltage grid and the demand of high voltage and high capacity keeps being enlarged. The paper discussed a high power UPQC for high power nonlinear loads. In this UPQC, shunt APF uses a hybrid APF which includes a Passive Power Filter (PPF) and an APF. Shunt APF is connected to a series LC resonance circuit in grid fundamental frequency so as to make shunt APF in lower voltage and lower power. The series LC resonance circuit is connected to grid with a capacitor. DC linker of PPF is connected to DC link of APF. This type of UPQC is fit for high voltage high power application because the voltage and capacity of its active device is much lower than those of the whole UPQC. The paper discussed the principle and control method of this UPQC.

Unified Power Quality Conditioner (UPQC) with a modified Power Angle Control (PAC) scheme is presented for effective interconnection of renewable energy system into the grid. The UPQC consists of both shunt and series Active Power Filters (APFs). The shunt and series APF is one of the most effective custom power devices, which provides compensation for current and voltage-based disturbances, respectively. The shunt APF supplies active power to the load from the Distributed Generation (DG) in addition to reactive power demand supplied by it. Because of this functionality, the Volt–Ampere (VA) burden increases along with the rating of the shunt inverter. The PAC scheme aims to effective utilization of series and shunt APFs through sharing of reactive power to reduce VA burden on shunt APF. The PAC scheme is based on Synchronous Reference Frame (SRF) theory, which has simple computations, is robust and uses existing measurements of Solar Photovoltaic (SPV)-integrated UPQC. The performance of the proposed SPV-integrated UPQC is verified with the manifestation of nonlinear loads and reactive burdens with the SPV power generating system. The dynamic performance of the PV-UPQC is verified under the grid disturbances such as voltage sag, swell, varying load and change in solar irradiation. The effectiveness of the proposed control scheme is evaluated through the digital simulation and hardware experimental prototype model.

The issues related to power quality are becoming stronger; as the sensitive equipment plays a leading role in the power industry, it will pollute the system and increase the cost due to inbuilt compensation and deficiency of implemented regulations. Now, the cost and efficiency of the system are considered nearly at the identical level. Different active power filters were developed earlier to resolve the power quality issues. Among the series and shunt active power filter (SAPF), SAPF counterbalances the reactive power and brings down the load current harmonics. This paper presents both PI control and hysteresis current control based; three-phase SAPF in a three-wire three-phase system is implemented to even out the reactive power, harmonics and improving the total harmonic distortion for the nonlinear loads to improve power quality. This compensation process is a different approach only to sense the line currents and not the sensing of harmonics or load components of reactive power used in conventional methods. A MATLAB/Simulink environment is used to carry out the simulations. The obtained simulation results are the demonstration of improvement in power quality.

Power quality improvement faces different and significant problems due to voltage instability and the wide use of electronic power devices. To overcome these different power quality problems, an active power filter is used. The active power filter, in general, has 4 main categories- shunt, series, unified power quality conditioner, and hybrid active power filter. The shunt active power filter is usually used to mitigate source current harmonics and compensate reactive power for power factor correction. The series active power filter is usually used to mitigate voltage problems (sags, swells, transients, dips, distortions, harmonics, etc.). The unified power quality conditioner is a combination of the shunt active power filter and the series active power filter; it is used to mitigate all voltage and current problems, compensate voltage, current system harmonics, and reactive power compensation, and mitigate voltage dips, voltage sags, voltage swells, and voltage phase shift. In this paper, the 3-phase 3-wire unified power quality conditioner is utilized to mitigate all power system problems (voltages and currents) and discuss the effect of the shunt and series active power filter separately on source voltage and source current waveforms. This case study shows that the source voltage distortion can be mitigated by using the series active power filter alone, but the source current distortion cannot be mitigated without using both the series and shunt active power filter. The source current harmonic problem mainly exists due to 1) distorted voltage sources, and 2) non-linear loads. Therefore, the unified power quality conditioner must be used to mitigate source current distortions in the case of the distorted voltage source, to comply with the standard limits IEEE 519, IEC 555, and IEC 61000. HIGHLIGHTS The UPQC is used to mitigate all voltage and current problems and improve all power system quality The SEAPF eliminates all voltage problems The SHAPF has no effect on source voltage The SHAPF eliminates source current harmonic distortion GRAPHICAL ABSTRACT

This paper presents amodified p-q theory based unified power quality conditioner (UPQC) connected into a three-phase four-wire (3P4W) distribution system to handle the significant power quality problems viz. voltage and current harmonics, voltage sags and swells, voltage unbalancing, load unbalancing and low power factor due to excessive reactive power demand. A UPQC, which is the consecutive connection of shunt and series active power filters (APFs) combinedly connected to a dc link, is capable of rectifying all the above power quality problems concurrently. The concept of fundamental frequency positive sequence (FFPS) extraction derived from generalized cascaded delayed signal cancellation (GCDSC) technique and p-q theory are integrated in the UPQC control which results into its robust performance under highly undesirable conditions. To lighten the burden of reactive power on shunt APF, reactive power apportion between shunt and series APF is successfully accomplished with the power angle control (PAC)algorithm without hindering the major function of UPQC. The triggering signals for both converters are generated with the help of hysteresis band controller. An elaborated analysis of UPQC performance under dynamic loading condition with linear and non-linear single-phase and three-phaseloads is carried out in the simulation work done on the MATLAB/SIMULINK platform.

This paper deals with the steady state analysis of unified power quality conditioner (UPQC). The UPQC, a combination of shunt and series active power filter (APF), is one of the best solutions towards the mitigation of voltage sags and swells problems on distribution network. The analysis is based on active and reactive power flow through the shunt and series APF, wherein series APF can absorb or deliver the active power whereas the reactive power requirement is totally handle by shunt APF alone during all conditions. This analysis is very useful for selection of kVA ratings for both shunt and series APF. The MATLAB/SIMULINK results are provided in order to verify the analysis

The fitting of an active power filter (APF) to mitigate the effects of a diode or thyristor bridge-rectifier is predicated on the assumption that the rating of the filter is reasonable (i.e. small) compared with the rating of the existing bridge rectifier or of a replacement active rectifier. The ratings of both shunt and series APFs are analysed in a variety of operating conditions. Ratings are assessed through peak voltage and mean current as appropriate for junction semiconductor devices. Rms ratings are also given because of their familiarity. The series APF, appropriate for the compensation of harmonic voltage sources, is of a generally higher rating than the shunt APF, appropriate for harmonic current sources. The use of a shunt APF where a series APF is appropriate results in poor device utilisation. The semiconductor ratings of an APF can be reduced by using hybrid schemes. Removing large-amplitude, low-order current harmonics with harmonic traps is effective for the shunt APF. Reducing peak voltages by attenuating high-frequency components is effective with the series APF. Arranging rectifiers into multipulse arrangements is seen to be effective for both shunt and series APFs. The ratings are approximately halved for the 12-pulse case.

This article proposes a modified Power Angle Control (PAC) strategy for a Unified Power Quality Conditioner (UPQC) with Distributed Generation (DG) for the viable interconnection of a Solar Photovoltaic (SPV) system into the network. The UPQC is composed of both shunt and series Active Power Filters (APFs). Shunt and series APFs are the standout among the best custom power devices, which gives compensation to current- and voltage-based unsettling influences distinctly. In the SPV-interconnected UPQC, the shunt APF supplies power from DG to the associated load, apart from providing a reactive power request, which prompts an expansion in the Volt-Ampere (VA) burden after its rating. The PAC scheme intends the successful use of series and shunt APFs through the sharing of reactive power to decrease the VA burden on shunt APF. The PAC strategy depends on an enhanced Synchronous Reference Frame that is equipped with a Second-Order Generalized Integrator–based Phase Locked Loop, which has simple calculations, is vibrant, and utilizes existing estimations of the SPV-incorporated UPQC. The execution of the proposed SPV-incorporated UPQC is examined with the presence of nonlinear and reactive burdens. The dynamic performance of the SPV-UPQC is checked under the grid disturbances, for example, voltage sag, swell, varying load, and change in sunlight-based light. The viability of the proposed control strategy is assessed through the digital simulation and equipment exploratory model results.

One of the methods to improve the power quality in electric power networks is the use of active power filters. In the article, a method of analysis of transition and quasi-steady state processes in a shunt active three-phase power filter (SAPF) was presented. The analysis of electromagnetic processes was carried out on the basis of a mathematical description of the active filter. Structural models for the simulation of dynamic processes in the shunt active three-phase power filter were developed. The results of studies of dynamic states obtained for the SAPF with independent control and current control were shown. A study of the active filter was performed with the use of Matlab-Simulink program.

Non-linear loads, such as switched mode power supply, adjustable-speed drives, arc furnaces, etc., result in deterioration of power quality in terms of current harmonics and reactive power demand. Shunt active power filters are widely used to compensate the current harmonics, thereby improving power quality. Digital signal processors and microcontroller units used in digital control of shunt active power filters are constrained by a complex algorithm structure, adaptability, accuracy, the absence of feedback loop delays, and larger execution time. Shunt active power filters require a faster computation update rate to maintain the closed-loop bandwidth, accurate sensing of voltage and current, proper estimation of parameters, and a high frequency pulse-width modulation. In this article, a low-cost single all-on-chip field-programmable gate array implements the digital control of a three-phase shunt active power filter. This proposed implementation scheme has much less execution time and boosts the overall performance of the system. All required tasks of a typical shunt active power filter are implemented with a low-cost single all-on chip field-programmable gate array module that provides freedom to reconfigure for any other applications. Additional features, such as anti-windup, over-sampling, and time multiplexing, are also added to improve the overall performance. The proposed system is designed to meet IEEE 519 and IEC EN 61000-3 recommendations in terms of harmonic elimination and unity power factor requirements. The entire algorithm is coded, processed, and simulated using Xilinx 12.1 ISE Suite to estimate the advantages of the proposed system. This code is also defused on the low-cost single all-on-chip Xilinx Spartan 3A DSP-XC3SD1800 laboratory prototype, and experimental results obtained match with simulated counterparts. The proposed control scheme for the shunt active power filter results in reduces current harmonics under dynamic and steady-state operating conditions.

Shunt Active Power Filters (SAPF) are designed and employed for improvement in power quality by compensating harmonics and reactive Power. Nowadays, due to increase in use of non-linear as well as unbalanced loads in every stages cause harmonics problems. This causes false operation of sensitive equipments, heating of conductors and affects the customer side loads. The performance of SAPF depends upon the design and characteristic of controller adopted for it. In this paper, comparison between Proportional Integral (PI) and Fuzzy Logic Controller (FLC) based SAPF operations under linear and non-linear load conditions is presented. Voltage Source Converter (VSI) is connected to Point of Common Coupling (PCC) through interface inductor and is triggered by signals from hysteresis current controller. Simulation results with PI and FLC based operations on SAPF are presented and explained.

A reliable and efficient adaptive neural network-based active power filter to estimate and compensate harmonic distortion from supply mains is presented in this paper. Nowadays, there is drastic rise of current and voltage harmonics in power systems, caused by nonlinear loads. Active power filters (APF) are used to mitigate harmonics and thereby, improve power quality. This paper deals with application of artificial neural network in shunt active power filter which provides ease in implementation and fast dynamic response compared to conventional active power filters. In depth analysis of neural network applications in the intelligent control and estimation for power quality compensation is presented in this paper. Here, both reference compensating current generation scheme as well as current controller for the active power filter are developed using artificial neural network technique. Effective compensation provided by the proposed artificial neural network-based shunt active power filter is proved through simulation results. Experimental analysis carried out using dSPACE DS1104 also validates power quality improvement by the proposed APF scheme.

In this paper, the optimized Fuzzy Logic controlled three-phase Shunt Active Power Filters (SAPF) to eliminate harmonics of line current, correct power factor, balanced and unbalanced loads are given. To efficiently operate the system, Ant Colony Algorithm (ACA) optimizes this fuzzy logic controller. The controller is customized by adding a tuning controller to improve filter performance for lighter loads, in- addition, this tuning controller controls the output parameter of Shunt Active Power Filter (SAPF) by tuned to an optimized value. This optimized SAPF system has very short response time delay for different complex power quality issues and various compensation purposes. The system obtains dissimilar compensating current references accurately and easily. Moreover, Simulation shows that installation of this optimized controller in the SAPF system eliminates harmonics and corrects the waveform of the line current and corrected power factor. Simulation results obtained with MATLAB and testing results on a shunt APF are presented to validate the performance of the compensation system.

This paper explained efficient operation of solar cell based shunt active power filter for considerable energy management, harmonic estimation and is elimination along with reactive power compensation. The PV module is designed with INC MPPT technology and the shunt active power filter is connected at the AC side of the inverter integrated with a nonlinear rectifier load. The harmonics in load voltage, load current and source current are present due to connection of nonlinear load and intermittent PV power generation. The presence of harmonics in the power system may cause severe harm such as component overheating, increase in installation and consumer cost, malfunctioning of equipment, unusual tripping of circuit breakers, failure of sensors and noisy communication. To overcome all the above problems Filters are to be designed. Here a shunt active power filter designed to suppress the harmonic effects produced in the PV based system. Here the shunt active power filter design includes the PI controller whose gains are selected arbitrary which affects its performance. In the first study the total harmonic distortion (THD) is calculated with no filter and nonlinear load. Then THD Analysis is performed with shunt active power filter. Further to improve the performance of shunt active power filter, a hybrid optimization technique is applied to select the proper value of PI gains R and L of nonlinear load. The simulation result depicts that the optimized shunt active filter reduces harmonics to a great extent.