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This study deals with a new approach to tackle the challenges encountered in the filters-based reactive power calculation techniques utilized in the control system of static VAr compensators. In this approach, step and time-varying responses are improved by a combination of differential and filter-based methods. Then, optimum values of the main parameters of the low-pass and band-stop filters are determined considering three criteria: accuracy, speed, and capability for following the time-varying loads. To assess the performance of the proposed method, a new objective function is introduced, calculated for two sets of signals, captured from a real field in Mobarakeh Steel Company in Isfahan/Iran. Then, the proposed and the other reactive power calculation methods are assessed in practice and simulation. Also, the algorithm is implemented using a TMDSCNCD28335 as the processor to assess the real-time feasibility of the method. To do so, the reactive power variation of an electrical arc furnace is emulated in a prototype test bench and the algorithm is run in real-time by the processor during the system operation. [ABSTRACT FROM AUTHOR]

In remote areas, the distribution networks are usually underdeveloped; thus, three-phase medium-voltage grids may provide a low-cost power supply solution for residential buildings. A new centralized approach topology of three-port power hub converter, which consists of a V/V transformer, a back-to-back inverter, and a static volt-ampere reactive (VAR) compensator with adaptive impedance, is proposed for remote area power supply. The proposed three-port converter interfaces two bidirectional power ports connecting three-phase ac grid and dc grid, respectively, and one unidirectional power port connects ac loads. The functions of the proposed converter are the bidirectional power flow control between three-phase ac grid and dc grid and power quality compensation to the three-phase ac grid. Finally, to verify the validity of the proposed three-port converter and its control performance, different simulation and experimental cases are implemented under different operation conditions. [ABSTRACT FROM AUTHOR]

Induction generators (IG) are widely used in renewable energy systems, such as wind power, and micro/mini hydro-turbines. In applications, such as urban wind-energy systems, electric vehicles and more electric aircrafts, induction machines can be used to supply electrical power to auxiliary loads, deriving power from main engines. In this article, an IG system with open-end stator windings is proposed for simultaneous supply of regulated power to frequency insensitive ac-loads and dc-link loads for the first time. One end of the stator winding is connected to auxiliary loads while the other end is connected to a capacitor-fed voltage source inverter (VSI). In the proposed system, VSI is controlled to supply reactive power required by the IG while simultaneously regulating the dc-link voltage and ac load voltage at required level. The proposed method is based on scalar-control of the induction machine, thus making it a simple and robust system to supply active power demanded by ac and dc loads. The proposed control scheme has been simulated in MATLAB-Simulink and experimentally verified for steady state and transients with various ac loads including linear, nonlinear, and unbalanced loads. [ABSTRACT FROM AUTHOR]

The respective advantages of ac and dc microgrids lead to the blooming development of the hybrid ac/dc microgrid, which consists of ac and dc microgrid tied by an interlinking converter. A new structure of hybrid coupled interlinking converter (HCIC), which composed of a converter in series with a static VAR compensator (SVC), is proposed for hybrid ac and low voltage dc (LVdc) microgrids. Moreover, a new droop control method is correspondingly developed for the proposed HCIC. Its fundamental active and reactive power flow in the hybrid ac/dc microgrid is controlled by P-δ and Q-P-V droop control for converter part of the HCIC, and P-Q-α droop control is proposed for SVC part of the HCIC. Furthermore, a fast harmonic control is given based on a decoupled control strategy to improve the filtering characteristics of SVC part of the HCIC, suppress the harmonic power, and/or inject active power. Finally, simulation and experimental results are provided to verify that the proposed HCIC for hybrid ac/LVdc microgrids has the ability of good power flow control and power quality compensation, which not only meets the power flow requirements with low rating system, but also greatly promotes the development of more robust hybrid ac/dc microgrids. [ABSTRACT FROM AUTHOR]

In this paper, the structure, coordinate control method, and parameter design of a hybrid system are proposed for active power injection and nonactive power (reactive, harmonic, and unbalance power) compensation. The proposed hybrid system consists of a static var compensator (SVC) in parallel with a capacitive-coupling grid-connected inverter (CGCI) (SVC//CGCI). In SVC//CGCI, the SVC part is used to dynamic compensate the reactive power and unbalance power, while the low rating CGCI part is used to inject active power, provide harmonic power and a fixed amount of capacitive reactive power. Compared with conventional inductive-coupling grid-connected inverter (IGCI), the CGCI can provide active, reactive and harmonic power with low rating of active inverter part. The cost of the SVC part is much lower than that of active inverter part, thus the reduction of inverter rating can lead to a decrease in the total cost of the SVC//CGCI. Therefore, the SVC//CGCI can be a cost effective solution for active power injection and nonactive power compensation. Finally, simulation and experimental results are provided to show the advantages and validity of the proposed SVC//CGCI in compared with the conventional IGCI and SVC//IGCI. [ABSTRACT FROM AUTHOR]

In this paper, the structure, modeling, parameter design, and control method are proposed for a new hybrid structure of a static var compensator in parallel with a hybrid active power filter (SVC//HAPF). The SVC part of the SVC//HAPF is used to dynamically compensate the reactive power. And, the HAPF part is used to provide harmonic power and small amount of reactive power compensation. Due to the large fundamental voltage drop on coupling the LC part, the active inverter part of the SVC//HAPF has low voltage rating. Meanwhile, the parallel-connected SVC acts as a current divider to reduce the active inverter current. Therefore, the proposed SVC//HAPF shows the great promise in compensating harmonic current and wide-range reactive power with a low (both) voltage and current rating active inverter part. To show the advantages of the proposed SVC//HAPF, simulation comparisons among the active power filter (APF), HAPF, SVC in series with HAPF (SVC−HAPF), and the proposed SVC//HAPF are provided. Finally, experimental results based on the laboratory-scaled hardware prototype are given to show the validity of the SVC//HAPF. [ABSTRACT FROM PUBLISHER]

A modified scheme for reactive power compensation using static VAr compensators (SVCs) has been proposed in this paper for unbalanced four-wire system. The conventional SVC-based scheme requires both delta ( $\Delta $ $)$ - and star (Y)-connected SVCs for the same purpose. The proposed scheme uses a single-equivalent delta-connected thyristor controlled reactor (TCR) along with a combination of Y- and $\Delta $- connected thyristor switched capacitors for this purpose. The single-equivalent $\Delta $ -TCR in the present scheme is the result of a virtual Y-TCR and the conventional $\Delta $-TCR. This can reduces effective number of switching devices, cost, complexity, and space requirement compared to the conventional SVC-based schemes. Moreover, the proposed scheme can have various advantageous features compared to newly used DSTATCOM. The proposed scheme can also prevent injection of triplen harmonics in to the line, which is injected by Y-TCR in the conventional scheme. An optimized switching function is adopted in the proposed scheme for reduction of additional injected harmonics by TCR. The optimized switching angles are computed offline using gravitational search algorithm and stored in the processor memory for online application. The viability of the proposed scheme is simulated using MATLAB/Simulink and verified by suitable experimental results on a practical system. [ABSTRACT FROM AUTHOR]

A new thyristor-controlled reactor scheme is presented in this paper, in which the total bank is split into one Δ- and one Y-connected reactor bank with the addition of a low-rating zig-zag autotransformer, instead of the conventional scheme using a Δ-connected reactor bank with a harmonic current filter. This arrangement prevents the triplen harmonics generated by the Y bank from entering into the supply system and at the same time, the combination results in cancellation of some major characteristic harmonics from the source current. Thus, without using any additional filters or phase-shifting two-winding transformer, this scheme facilitates reactive power control over a wide range and also meets the requisite harmonics standards. The scheme is simple and provides a cost-effective solution to the VAr compensation problem. Simulation and experimental results are provided to validate the proposed concept. [ABSTRACT FROM PUBLISHER]

Based on cascaded ac–ac converter with controllable phase and amplitude (ACCPA), a novel π model ACCPA was proposed for power flow control, whose output voltage phase and amplitude can be regulated, respectively, and simultaneously with respect to the input voltage. Single-phase π model ACCPA comprises a buck-type ac unit, a third harmonic trap and a boost-type ac converter. Compared with single-phase cascaded ACCPA, it has a more simplified structure by dispensing with the LC output filter of the buck-type ac converter, and can adopt the same two-stage duty-cycle modulation. The buck-type ac unit regulates the phase of output voltage and the boost-type ac converter does the amplitude. By utilizing impedance compensation with capacitance in single-phase π model ACCPA, it is effective to counteract or reduce the lag effect which is put on fundamental voltage by line impedance of third harmonic trap and inductance. Three-phase π model ACCPA comprises three buck-type ac units and a three-phase boost-type ac converter, it not only dispenses with three LC output filters, but also does three third harmonic traps, so it has simple structure. Experimental results verified the feasibility of π model ACCPA and the correctness of its theory. [ABSTRACT FROM PUBLISHER]

This paper proposes a probabilistic method to model the uncertainty of reactive power compensation by static VAr compensators (SVCs) in electric arc furnaces (EAFs). The time-varying characteristics of EAF accentuate the voltage fluctuations and produce flicker in power lines as well as neighboring loads. In order to solve this issue, quick and accurate response of SVC within a half-cycle ahead is required. This paper proposes a nonparametric approach based on lower upper bound estimation method to construct prediction intervals (PIs) for the reactive power in EAFs. Due to the nonlinear nature of reactive power signals in EAFs, a set of PIs are produced and combined to find an optimal aggregated PI. The proposed prediction method provides a faster-than-real-time monitoring of SVC, which aims at high speed and efficient reactive power compensation. In order to find the most satisfying PIs with high coverage probability and low average width, an optimization algorithm is developed to improve the training process of neural networks. The appropriate performance of the proposed method is examined on the practical data gathered from the Mobarakeh Steel Company, Iran. [ABSTRACT FROM PUBLISHER]

In this paper, a new modeling and parameter design method for the thyristor-controlled LC-coupled hybrid active power filter (TCLC-HAPF) is proposed, which includes the analysis of the inner flowed three-phase unbalanced power during unbalanced condition. Different from the conventional method which ignores the inner flowed three-phase unbalanced power, the proposed design method can achieve better performance during unbalanced compensation. To verify the validity and advantages of the proposed modeling and parameter design method of TCLC-HAPF, the mathematical analysis, representative simulation and experimental results for compensating different unbalanced loading situation are presented in comparison with the conventional design method. [ABSTRACT FROM PUBLISHER]

This paper presents a topology for a three-phase generation system for an isolated unbalanced load fed by a doubly fed induction generator with a neutral wire to include single-phase loads. The challenges of unbalanced loads connected to the system are presented along with a proposal for mitigating current imbalance by employing a four-leg rectifier. The proposed compensation method is based on the sequence decomposition analysis, and thus, it is based on previous works that use current control in double synchronous reference frames. Nevertheless, a conceptual analysis is presented that vindicates the use of resonant controllers in the stationary $abc$ frame. [ABSTRACT FROM PUBLISHER]

In a flyback converter using the conventional valley-switching method, the switching frequency under the light load condition is higher than that under the heavy load condition, which increases the switching loss. A valley skip (VS) technique can reduce the switching frequency under the light load condition. Although it helps to reduce the switching loss, it makes the uncomfortable humming sound caused by a sudden change in switching frequency during valley change. To minimize the audible noise, a new digitally controlled soft valley change (SVC) technique is proposed in this paper. It changes the turn-on instant among valleys gradationally during several switching cycles under any transient situation. The SVC also helps to spread switching frequency so that electromagnetic interference can be reduced. The proposed technique is suitable for the applications that operate under the dynamic load condition such as an audio amplifier. The proposed technique is implemented in an integrated circuit and verified by a prototype experimental test board of 60 W/12 V. [ABSTRACT FROM PUBLISHER]

This paper presents the stability-improvement results of a synchronous generator (SG)-based one-machine infinite-bus system with a permanent-magnet SG (PMSG)-based offshore wind farm (OWF) and a doubly fed induction generator (DFIG)-based OWF using a static VAR compensator (SVC). The operating characteristics of the studied two OWFs are simulated by an equivalent aggregated PMSG driven by an equivalent wind turbine (WT) and an equivalent aggregated DFIG driven by an equivalent WT through an equivalent gearbox, respectively. A damping controller of the SVC is designed by using adaptive-network-based fuzzy inference system (ANFIS) to contribute adequate damping characteristics to the dominant modes of the studied SG under various operating conditions. A frequency-domain approach based on a linearized system model using root-loci technique and a time-domain scheme based on a nonlinear system model subject to various disturbances are both utilized to examine the effectiveness of the proposed control scheme. It can be concluded from the simulation results that the proposed SVC joined with the ANFIS damping controller is capable of improving the stability of the studied SG system subject to different disturbances. [ABSTRACT FROM PUBLISHER]

A novel spatial-layer rate-control algorithm is proposed for scalable video coding (SVC). First, by analyzing the relationship among the best initial quantization parameter (Qp), channel bandwidth, and the initial frames' complexity measure, an adaptive Qp-initialization model is introduced to determine the starting Qp value for not only the base layer but also the spatial enhancement layers of SVC. Then, a two-stage Qp -determination scheme is designed to improve the rate-control performance for the spatial-layer SVC with an efficient frame-complexity prediction method and an adaptive model-parameter update technique employed. Experimental results demonstrate the effectiveness of the proposed Qp -initialization scheme and the two-stage Qp-determination algorithm. By comparison with two other benchmark rate-control algorithms, the proposed rate-control algorithm is able to control constrained bit rates accurately with better rate-distortion performance. [ABSTRACT FROM PUBLISHER]

In this paper, the control strategy for the static synchronous compensator (STATCOM) used in utility distribution systems is investigated, and a novel fuzzy-PI-based direct- output-voltage (DOV) control strategy is presented. Based on power balancing principle and feedforward decoupling control, this novel DOV control strategy cannot only reduce the active and reactive current control loops of a conventional double-loop control strategy but also achieve the decoupling control to regulate dc-link voltage and maintain the voltages at the point of common coupling (PCC). In order to effectively improve the immunity capability of this novel DOV control strategy to the uncertainties in system parameters, two fuzzy PI controllers are separately employed to maintain the voltages at the PCC and to simultaneously regulate dc-link voltage. The validity and effectiveness of this novel control strategy for the STATCOM used in utility distribution systems have been verified by simulation results, and a scaled physical prototype rated at ±300 kVAr is also developed to test the STATCOM system. [ABSTRACT FROM AUTHOR]