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This paper presents the stability analysis for a distribution static compensator (DSTATCOM) that operates in current control mode based on bifurcation theory. Bifurcations delimit the operating zones of nonlinear circuits and, hence, the capability to compute these bifurcations is of important interest for practical design. A control design for the DSTATCOM is proposed. Along with this control, a suitable mathematical representation of the DSTATCOM is proposed to carry out the bifurcation analysis efficiently. The stability regions in the Thevenin equivalent plane are computed for different power factors at the point of common coupling. In addition, the stability regions in the control gain space, as well as the contour lines for different Floquet multipliers are computed. It is demonstrated through bifurcation analysis that the loss of stability in the DSTATCOM is due to the emergence of a Neimark bifurcation. The observations are verified through simulation studies. Index Terms--Distribution static compensator (DSTATCOM), floquet multiplier, Neimark bifurcation, point of common coupling (PCC), stability regions.

A new control strategy for static compensators (STATCOMs) operating under unbalanced voltages and currents is presented in this paper. The proposed strategy adopts a state observer (software sensor) to estimate ac voltages at the STATCOM connection point. This way, physical voltage sensors are not needed and the hardware gets simplified, among other advantages. Using the superposition principle, a controller is designed to independently control both positive and negative sequence currents, eliminating the risk of overcurrents during unbalanced conditions and improving the power quality at the STATCOM connection bus. Two operating modes are proposed for the computation of the reference currents, depending on whether the objective is to compensate unbalanced load currents or regulate bus voltages. The proposed observer allows positive and negative sequences to be estimated in a fraction of the fundamental cycle, avoiding the delay often introduced by filter-based methods. Overall, the STATCOM performance is improved under unbalanced conditions, according to simulation results presented in the paper. Index Terms--Load compensation, observers, power quality (PQ), sequence currents, software sensors, static compensator (STATCOM), unbalanced systems.

Thyristor-based onload tap-changing ac voltage stabilizers are cheap and robust. They have replaced most mechanical tap-changers in low voltage applications from 300 VA to 300 kVA. Nevertheless, this replacement hardily applies to tap-changers associated to transformers feeding medium-voltage lines (typically 69 kV primary, 34.5 kV line, 10 MVA) which need periodical maintenance of contacts and oil. The Electric Power Research Institute (EPRI) has studied the feasibility of this replacement. It detected economical problems derived from the need for series association of thyristors to manage the high voltages involved, and from the current overload developed under line fault. The paper reviews the configurations used in that field and proposes new solutions, using a compensating transformer in the main circuit and multi-winding coils in the commutating circuit, with reduced overload effect and no series association of thyristors, drastically decreasing their number and rating. The stabilizer can be installed at any point of the line and the electronic circuit can be fixed to ground. Subsequent works study and synthesize several commutating circuits in detail. Index Terms--AC voltage stabilizer, onload tap-changer (OLTC), power conditioning, power quality, voltage control.

Techniques for distributed generations (DGs) have attracted increasing attention due to considerations of environmental sustainability. Wind farms are one of the DGs, and they have intermittent characteristics. This paper presents a method using wind generator voltages, static compensators, and transformer taps as controllers to regulate the voltage profile for operation planning in a distribution system. Wind power generations and bus loads are modeled with random variables. Through gray-based genetic algorithms (GAs), the MW loss in the system is minimized and the operational constraints are fulfilled. Moreover, this paper uses the cumulant method to calculate the bus voltage fluctuation by using the algebraic addition and multiplication to avoid convolution. The probability density function of the voltage fluctuation can be further expressed by the Gram--Charlier series expansion. Applicability of the proposed method is verified through simulation by using a 17-bus system and an autonomous 24-bus (Penghu) system. Index Terms--Cumulant, genetic algorithm (GA), gray code, reactive power control, wind farm.

This paper proposes the performance study of the rotary power-flow controller (RPFC) operating in a two-line transmission corridor. Part I presented the RPFC model and its implementation in SPS/Matlab. This paper presents the simulation results of the RPFC operating in the corridor during the postcontingency period, when one of the two lines is out of service. From the RPFC model and the RPFC control system, derived in part I, this paper first determines the model of the electrical corridor equipped with the RPFC, and then implements the entire model, including the RPFC control system, in the SPS/Matlab. The obtained results provide the behavior of the RPFC as well as that of the corridor during the postcontingency period. This paper analyzes, among other parameters, the influence of the RPST number of poles on the RPFC performances. Finally, the utilization of the RPFC, associated with the shunt capacitive compensation, allows restoring the postcontingency power-flow conditions to be equal to those of the precontingency period. Index Terms--Phase.shifting transformer, rotary phase-shifting transformer, rotary power-flow controller (RPFC), unified power-flow controller (UPFC), variable frequency transformer, voltage regulating-transformer.

This paper (Part I) presents a model suitable for the performance analysis of a rotary power-flow controller (RPFC), which operates in a two-lines power system corridor. The RPFC consists of two transformers (one series and one shunt), and two rotary phase-shifting transformers operating in standstill. The shunt and series transformers and the two rotary phase-shifting transformers are represented by the conventional equivalent circuit of a two-winding transformer. The rotor windings of these rotary phase-shifting transformers are connected in parallel while their stator windings are in series. The resulting equipment is the RPFC whose macroscopic model is proposed. The model involves a series branch consisting of an adjustable voltage source (with its internal impedance) and a shunt branch consisting of a current source. The obtained RPFC model with the regulators, implemented in SPS/Matlab, is used for further simulations in Part H. Index Terms--Phase-shifting transformer, rotary phase-shifting transformer, rotary power-flow controller (RPFC), unified power-flow controller (UPFC), variable frequency transformer, voltage regulating-transformer.

This paper presents a novel radio-frequency identification (RFID)-based smart freezer using a new inventory-management scheme for extremely low temperature environments. The proposed solution utilizes backpressure inventory control, systematic selection of antenna configuration, and antenna power control. The proposed distributed-inventory-control (DIC) scheme dictates the amount of items transferred through the supply chain. When a high item visibility is ensured, the control scheme maintains the desired level of inventory at each supply-chain echelon. The performance of the DIC scheme is guaranteed using a Lyapunov-based analysis. The proposed RFID antenna-configuration design methodology coupled with locally asymptotically stable distributed power control ensures a 99% read rate of items while minimizing the required number of RFID antennas in the confined cold chain environments with non-RF-friendly materials. The proposed RFID-based smart-freezer performance is verified through simulations of supply chain and experiments on an industrial freezer testbed operating at -100[degrees]F. Index Terms--Inventory control, low-temperature chemical management, passive radio-frequency identification (RFID), power control.

In this paper, we analyze the queuing performance in the finite-state Markov channel (FSMC) when the single-step power control (SSPC) scheme is adopted. To start with, an SSPC model and its extended power control error (PCE) model are proposed and described in detail. Such models can emulate the behaviors of the interaction between the SSPC and an FSMC and the variation of the PCE with high accuracy. Furthermore, the packet error rate that has been recently analyzed by Lee and Chang is adopted to evaluate the service rate, the time average queuing length, and the probability mass function (PMF) of the queuing length variation. Based on these results, a queuing variation model is proposed to emulate the queuing variation in the FSMC. The flooring phenomenon of the queuing length is observed under a particular requirement of an overflow probability when the SNR value is greater than a certain value. This indicates that the trade-off among the SNR, the buffer size of the queue, and the overflow probability exists. Hence, two different approaches to select the optimal target SNR of the SSPC and the maximum buffer size of the queue under the requested queuing buffer overflow probability are proposed. The improvement of the SSPC, its impact on the system, and the validity of the proposed models are shown in this paper as well. Index Terms--Finite-state Markov channel (FSMC), queuing performance, queuing variation model, single-step power control (SSPC), SSPC model.

An algorithm based on a nonlinear interior-point method and discretization penalties is proposed in this paper for the solution of the mixed-integer nonlinear programming (MINLP) problem associated with reactive power and voltage control in distribution systems to minimize daily energy losses, with time-related constraints being considered. Some of these constraints represent limits on the number of switching operations of transformer load tap changers (LTCs) and capacitors, which are modeled as discrete control variables. The discrete variables are treated here as continuous variables during the solution process, thus transforming the MINLP problem into an NLP problem that can be more efficiently solved exploiting its highly sparse matrix structure; a strategy is developed to round these variables off to their nearest discrete values, so that daily switching operation limits are properly met. The proposed method is compared with respect to other well-known MINLP solution methods, namely, a genetic algorithm and the popular GAMS MINLP solvers BARON and DICOPT. The effectiveness of the proposed method is demonstrated in the well-known PG&E 69-bus distribution network and a real distribution system in the city of Guangzhou, China, where the proposed technique has been in operation since 2003. Index Terms--Distribution systems, genetic algorithms, interior-point methods, mixed-integer nonlinear programming, nonlinear programming, optimal switching operations, optimization solvers, reactive power control, voltage control.

Phasor measurement units (PMUs) are considered as a promising tool for future monitoring, protection and control of power systems. In this paper, a unified approach is proposed in order to determine the optimal number and locations of PMUs to make the system measurement model observable and thereby can be used for power system state estimation. The PMU placement problem is formulated as a binary integer linear programming (BILP), in which the binary decision variables (0, 1) determine whether to install a PMU at each bus, while preserving the system observability and lowest system metering economy. The proposed approach integrates the impacts of both existing conventional power injection/flow measurements (if any) and the possibility of single or multiple PMU loss into the decision strategy of the optimal PMU allocation. Unlike other available techniques, the network topology remains unaltered for the inclusion of conventional measurements, and therefore the network connectivity matrix is built only once based on the original network topology. The mathematical formulation of the problem maintains the original bus ordering of the system under study, and therefore the solution directly points at the optimal PMU locations. Simulations using Matlab are conducted on a simple testing seven-bus system, as well as on different IEEE systems (14-bus, 30-bus, 57-bus, and 118-bus) to prove the validity of the proposed method. The results obtained in this paper are compared with those published before in literature. Index Terms--Integer programming, optimal location, PMUs, state estimation.

Complexities of computer program codes for Newton--Raphson load flow (NRLF) analysis are usually enhanced during power flow modeling of an interline power flow controller (IPFC). This is due to the fact that the contributions of the series converters of the IPFC are needed to be accounted for while computing bus power injections and Jacobian matrix elements. Also, the IPFC real power injection term along with its associated Jacobian matrix call for new codes to be written. In this paper an advanced IPFC model is proposed to address this issue, wherein an existing power system installed with IPFC(s) is transformed into an augmented equivalent network without any IPFC. To obtain the solution of the original network containing IPFC(s), the augmented network can easily be solved by reusing the existing NRLF codes, as this network is now devoid of any IPFC. Consequently, the complexities of the computer program codes are reduced substantially. Various practical device limit constraints of the IPFC can also be taken into account by the proposed model. Index Terms--Flexible ac transmission systems (FACTS), interline power flow controller (IPFC), Newton power flow.

A wide-range active and reactive power flow controller is designed to operate the inverter in pure leading, pure lagging, and the mix with active and reactive power conditions. The key to achieving lagging power flow control is to ensure sufficiently high enough dc bus voltage to avoid duty cycle saturation. The key to achieving precision power flow control for a wide range of power level is to adopt the quasi-proportional resonant controller for the current loop and the admittance compensator to cancel the grid-voltage-induced negative power flow. In this paper, the current loop transfer function has been systematically derived for the controller design purpose. Phasor analysis was adopted to explain the need of dc bus voltage requirement. A 5-kVA grid-tie fuel cell inverter was used as the platform to show current loop controller design and admittance compensation. The proposed controller has been simulated, and the same parameters have been used for a DSP-based controller. Both simulation and hardware experimental results agree well with the theoretical analysis. Index Terms--Admittance compensation, fuel cell power conditioning system, LCL filter, proportional-resonant compensator, reactive power control, single-phase grid-tie inverter.

This paper proposes a novel fuzzy power control (FPC) scheme to effectively improve the performance of the downlink code-division multiple-access (CDMA)-based local multipoint distribution service (LMDS) system. Conventional power control scheme is taken to reduce rain fading effects and intercell interference, and then increase the capacity of this LMDS system. To more effectively improve the system performance, three major factors (i.e., rain rate, path loss exponent depending on channel fading conditions, and number of subscribers in the interfering cell sectors) are taken as the input variables of fuzzy logic control in our proposed FPC scheme to obtain the channel quality condition and distance threshold for power control region adjustments. Simulation results show that our proposed FPC scheme performs better than the conventional scheme in terms of outage probability. Index Terms--Code division multiple access (CDMA), fuzzy, local multipoint distribution service (LMDS), power control.

Mobile terminals (MTs) in real personal communication service (PCS) environments are turned OFF due to limited battery lifetime, avoidance of unwanted incoming calls, and undesirable subscriber behaviors. Since the probability that an MT is in the OFF-state may be significant, MT power ON/OFF-state transition behavior and the effect of state management on mobile communication networks require analysis. Two MT power ON/OFF-state management schemes are introduced based on the level of location registers (LRs) for managing MT state information. Effects are investigated from the aspects of a radio interface, a network, and a database based on the modeling of the state transition behavior of an MT for varying values of MT and mobile communication network parameters. These values include the MT ON/OFF duration and the incoming call arrival rate. Although additional database processing overhead exists, the management of MT power ON/OFF-states provides a significant reduction in overhead from the aspects of the radio interface and the network. There is a tradeoff between the two management schemes as the MT ON/OFF ratio varies. Index Terms--Database, location register (LR), mobile communication networks, mobility management, modeling and analysis, network, personal communication service (PCS), power ON/OFF-state management, radio interface.

This paper tackles a power minimization problem of interleave-division multiple-access (IDMA) systems over a fading multiple-access channel. The problem is minimizing the total power received by the receiver while keeping the bit error rates (BERs) of all users below a predefined value. The original formulation of the problem has highly nonlinear and implicitly defined functions, which render most existing optimization methods incapable. A new formulation is proposed in this paper, whose solution can effectively be obtained by a branch-and-bound (B&B) technique. An algorithm is devised based on B&B, and its effectiveness is also demonstrated by numerical experiments of systems with a moderate numbers of users. Index Terms--Branch-and-bound (B&B), code-division multiple access (CDMA), interleave-division multiple access (IDMA), iterative multiuser detection (MUD), optimization, power allocation.

Hybrid electric vehicles (HEVs) have demonstrated the capability to improve fuel economy and emissions. The plug-in HEV (PHEV), utilizing more battery power, has become a more attractive upgrade of the HEV. The charge-depletion mode is more appropriate for the power management of PHEVs, i.e., the state of charge (SOC) is expected to drop to a low threshold when the vehicle reaches the trip destination. Trip information has so far been considered as future information for vehicle operation and is thus not available a priori. This situation can be changed by the recent advancement in intelligent transportation systems (ITSs) based on the use of on-board global positioning systems (GPSs), geographical information systems (GISs), and advanced traffic flow modeling techniques. In this paper, a new approach to optimal power management of PHEVs in the charge-depletion mode is proposed with driving cycle modeling based on the historic traffic information. A dynamic programming (DP) algorithm is applied to reinforce the charge-depletion control such that the SOC drops to a specific terminal value at the end of the driving cycle. The vehicle model was based on a hybrid electric sport utility vehicle (SUV). Only fuel consumption is considered for the current stage of the study. A simulation study was conducted for several standard driving cycles and two trip models using the proposed method, and the results showed significant improvement in fuel economy compared with a rule-based control and a depletion sustenance control for most cases. Furthermore, the results showed much better consistency in fuel economy compared with rule-based and depletion sustenance control. Index Terms--Dynamic programming (DP), intelligent transportation systems (ITSs), plug-in hybrid electric vehicles (PHEVs), power management.

Self-commutating multilevel current reinjection is a potential alternative to conventional HVDC thyristor technology. An important drawback of the multilevel configurations is the interdependence of the reactive power injections at both ends of the link. This paper describes a new concept applicable to large power converters consisting of two series-connected twelve-pulse groups. It is based on the use of a controllable shift between the firings of the two twelve-pulse groups in opposite directions, a new concept that provides independent reactive power control at the sending and receiving ends. The theory is verified by EMTDC simulation. Index Terms--HVDC transmission, multilevel conversion, reactive power control.

A neurofuzzy controller (NFC) with adaptive input link weights (ILWs) and working as an adaptive power system stabilizer is presented. The control structure of the proposed adaptive neurofuzzy power system stabilizers (ANFPSSs) consists of a neuroidentifier to track the dynamic behavior of the plant and an NFC to damp the low-frequency power system oscillations. Usually, the input membership functions (IMFs) and consequent parameters (CPs) are adapted in order to enhance the performance of the NFC. However, the adjustment of IMFs can be realized indirectly by the tuning of ILWs introduced here, which is simpler due to the small number of parameters involved. Therefore, in this paper, ILWs and CPs are updated online by the gradient descent method. Simulation studies over a range of operating conditions and disturbances in a single machine-infinite bus system and a multimachine power system demonstrate the improvement in the dynamic performance of the system with the proposed ANFPSS. Index Terms--Adaptive control, fuzzy logic controller (FLC), neural networks, power system stabilizer (PSS).

This paper proposes a unified mathematical model of a voltage-sourced converter (VSC) based on positive and negative synchronously rotating frames under both unbalanced grid supply and imbalanced input impedances. Based on the developed model, a new definition of instantaneous reactive power is introduced, and an accurate mathematical model of the instantaneous active and reactive powers at different locations of the VSC is derived. To avoid the use of band-trap filter for decomposing the positive- and negative-sequence dq components of current and voltage, a new control scheme with multifrequency proportional-resonant controller in the stationary [alpha][beta] frame is employed to improve the steady state and dynamic response under generalized unbalanced operation conditions. Simulation and experimental studies with various factors were conducted and compared under different types of unbalanced conditions. The simulated and experimental results demonstrate that the proposed control scheme in the stationary [alpha][beta] frame provides sufficiently steady-state tracking capability for ac input current, and a better transient response in compensation for wide-range generalized unbalanced operation conditions. Index Terms--Instantaneous power, multifrequency proportional-resonant (MFPR) regulator, unbalanced conditions, voltage-sourced converter (VSC).

This paper presents the output power control of a wind energy conversion system (WECS) based on a permanent magnet synchronous generator (PMSG). It is assumed that the considered wind module integrates a stand-alone hybrid generation system, jointly with a battery bank, a variable ac load, and other generation subsystems. The operation strategy of the hybrid system determines two possible operation modes for the WECS, depending on the power requirements of the load and the wind availability. The paper deals with the design of a combined high-order sliding mode (HOSM) controller for the power control of the WECS on both operational modes. The main features of the obtained controller are its chattering-free behavior, its finite-time reaching phase, its simplicity, and its robustness with respect to external disturbances and unmodeled dynamics. The performance of the closed-loop system is assessed through representative computer simulations. Index Terms--High-order sliding mode (HOSM), nonlinear systems, wind energy.

Wind power penetration is expected to be largely increased in the near future. Nevertheless, due to the high variability of wind, the increase of the installed capacity in wind energy could sometimes lead to a stopping of nonadjustable power plants if the planning of those units was still decided without considering a realistic estimation of the available wind potential. In that way, and as it is illusory to imagine that all the installed wind capacity will always be produced, this article proposes a new method, based on a discrete convolution process, to compute a two-state probabilistic model for wind generation and to define, so, an equivalent capacity for global wind production in order to introduce it in the predictive peak load covering process. This global model is, in fact, based on the convolution between each single wind park multistates histograms and permits to compute accurate equivalent capacity for the wind production of an entire country. Finally, note that, here, the proposed method is applied to the Belgian production park. Index Terms--Power control, power system modeling, Weibull distributions, wind energy.

An industrial plant, such a power system, always contains parametric uncertainties. In the design of a controller the uncertainties have to be considered. Otherwise, if the real plant differs from the assumed plant model, a controller, designed based on classical controller design approaches, may not ensure the stability of the overall system. In this paper design of robust control for the UPFC controllers including power-flow and DC voltage regulator, using a [H.sub.[infinity]] loop-shaping design via a normalized coprime factorization approach, where loop-shape refers to magnitude of the loop transfer function L = GK as function of frequency is presented. As an example, we have designed a case for the system to compare the proposed method with a conventional method (classical P-I controller). AS the results of the linear and nonlinear simulations, the validity of the proposed method has been confirmed. Keywords: Unified Power Flow Controller (UPFC); Flexible AC Transmission Systems (FACTS); power system oscillation; [H.sub.[infinity]] loop-shaping, INTRODUCTION The Flexible AC Transmission Systems (FACTS) based on power electronics offer an opportunity to enhance controllability, stability, and power transfer capability of AC transmission systems . The Unified Power [...]

This paper considers the suitability of a range of multi-input-multi-output (MIMO) orthogonal frequency-division multiplexing architectures for use in urban hotspots. A ray-tracing propagation model is used to produce realistic MIMO channel data. This information is used to determine the expected throughput and area coverage for various physical (PHY) layer schemes. Site-specific throughput predictions are generated in a city-center environment. Link adaptation (LA) is shown to play a key role in the choice of space-time algorithm, the use of adaptive modulation and coding, and the number of antennas employed at both ends of the radio link. No single PHY layer scheme is suitable to cover the entire coverage area. Results demonstrate the need for MIMO LA under a wide range of channel conditions. For the area under test, 2% of covered locations selected a spatial multiplexing (SM) scheme, 50% selected a space-time block coding (STBC) scheme, and 48 % selected a hybrid SM/STBC scheme. With suitable power control and LA, for the scenario under consideration, high peak capacities and good geographic coverage were achieved. Index Terms--Link adaptation (LA), orthogonal frequency-division multiplexing (OFDM), power control, propagation, space-time block codes (STBCs), spatial multiplexing (SM).

We consider the problem of finding low-complexity, bandwidth-efficient, and processing-power-efficient transmission schemes for a downlink scenario under the framework of diversity combining. Capitalizing on recent results for joint adaptive modulation and diversity combining (AMDC) schemes, we design and analyze two AMDC schemes that utilize power control to reduce the radiated power and, thus, the potential interference to other systems/users. Based on knowledge of channel fading, the proposed schemes adaptively select the signal constellation, diversity combiner structure, and transmit power level. We show that the novel schemes also provide significant average transmit power gains compared to existing joint adaptive quadratic-amplitude modulation (QAM) and diversity schemes. In particular, over a large signal-to-noise ratio (SNR) range, the transmitted power is reduced by 30%-50%, yielding a substantial decrease in interference to coexisting systems/users, while maintaining high average spectral efficiency, low combining complexity, and compliance with bit-error-rate constraints. Index Terms--Adaptive modulation, diversity techniques, performance analysis, power control.

Recently dual frequency induction heating is often performed for hardening an uneven work-piece such as a gear which has tips and bottoms, and two resonant inverters are necessary for such heating. In this paper, new quasi-resonant inverter circuits including a resonant capacitor with a short-circuit switch, which can operate at various frequencies are discussed. First, an equivalently variable resonant capacitor having a short-circuit switch in parallel is described for varying output frequency of the quasi-resonant inverter. Then, two types of adjustable frequency quasi-resonant inverter circuits including the variable resonant capacitor are reported in every desired range of the adjustable output frequency. Additionally a new indirect power control method is proposed since the power to the work-piece cannot be directly detected in operation and the equivalent output resistance of the heating circuit is unknown. Index Terms--Adjustable frequency, dual frequency induction heating, power control, quasi-resonant inverter, short-circuit switch.

In this paper, a new strategy for the control of terminal voltage and frequency of a stand-alone self-excited induction generator-(SEIG) based wind generator, working with variable speed and load is proposed. With a generalized impedance controller (GIC) (voltage source pulsewidth-modulated inverter with a dc-link battery), a new strategy to maintain the active and reactive power balance at the SEIG terminals has been introduced to control its terminal voltage and frequency. In the proposed control strategy, only a voltage feedback loop has been used to control both the SEIG terminal voltage and the frequency. A mathematical model of the SEIG-GIC system under wind generator environment has been developed and simulated in the MATLAB/Simulink. The simulation results are validated with the experimental ones conducted on a laboratory prototype of the SEIG-GIC system. The novelty of the present technique is that the GIC is capable of maintaining a constant SEIG terminal voltage and frequency, following both speed and load perturbations, with only a single (voltage) feedback loop. Index Terms--Active and reactive power controller, frequency controller, generalized impedance controller (GIC), self-excited induction generator (SEIG), voltage controller.

Medium access control (MAC) protocols simulta. neously integrating transmission power (TP) control with directional antennas have the potential to enhance both energy savings and capacity throughput in wireless multihop Mobile Ad hoc NETworks (MANETs). In this paper, we present a model to calculate future interference in networks with directional antennas, and based on this model, we derive some relations that should exist between the required TP of RTS, CTS, DATA, and ACK frames for successful data packet delivery in MANETs based on the directional version of the IEEE 802.11 distributed coordination function. From these relations, we propose a distributed power control scheme. Furthermore, we show, via simulations, that the true potentials from the proposed control scheme cannot be shown due to the imperfection of the derived model. Based on these observations, we introduce another class of power control algorithm that instead deploys a prediction filter (Kalman or extended Kalman) to estimate future interference. Simulation experiments for different topologies are used to verify the significant throughput and energy gains that can be obtained by the proposed power control schemes. Index Terms--Directional antenna, interference, Kalman filter, Mobile Ad hoc NETwork (MANET), power control.

Power electronic converters connected in series with the grid can provide protection of sensitive processes against voltage dips. In this paper, an advanced cascade controller for series-connected voltage-source converter (VSC), constituted by an outer voltage loop and an inner current loop, is presented. Positive and negative sequence components of voltage and current are controlled separately to achieve perfect compensation of unbalanced dips. Limitation of the VSC output voltage and compensation of the computational time delay are included in the current controller for both sequence components. Experimental results for the series-connected VSC with the proposed cascade controller under balanced and unbalanced voltage dips are presented. Index Terms--Cascade controller, dynamic sag compensators, power quality, vector current controller (VCC), voltage-source converter.

This work presents the development of analytical models for thyristor-controlled reactors (TCRs). A nonlinear model for the TCR was developed based on the use of Generalized Switching Functions and from this model, a detailed linear model was derived. The linear model allows for the analysis and precise understanding of the behavior of the TCR under small disturbances both in the time and frequency domains, for frequency ranges up to some tens of hertz. This model clearly shows that the TCR dynamics are operating point dependent. System parameter variations are also correctly considered in the model. With the proposed model, it is possible to design static var compensators (SVC) controllers in an integrated form, avoiding risks of instabilities and guaranteeing a good overall dynamic performance for the system. Validation of the models was done by comparing simulated results obtained with the proposed model with those obtained with a traditional electromagnetic transients program (EMTP). Index Terms--Generalized switching functions, reactive power control, static var compensators, SVC analytical models.

This paper presents a model-based controller for a three-phase four-wire shunt active filter, which uses a three-leg split-capacitor topology to implement the voltage source inverter. The controller is aimed to compensate reactive power and harmonic distortion in the general case of distorted and unbalanced source voltages and load currents, including distorted loads connected between a phase and the neutral line. In addition, the controller is able to compensate for the homopolar component of the load current, that is, the current flowing to the source via the neutral line can be considerably reduced without modifying the actual topology. The complete model in (fixed frame) [alpha][beta] [gamma]-coordinates is presented. Special attention is given to the homopolar component (referred here as the [gamma]-component) of the line current, source voltage and control input, which are instrumental for the control design purpose. Experimental results in a 2 kVA prototype are provided to illustrate the benefits of the proposed solution. Index Terms--Active filters, adaptive signal detection, reactive power control.

This paper introduces a procedure for using optimization-enabled electromagnetic transient simulation (OE-EMTS) for the design of HVDC system controls. The OE-EMTS method conducts a sequence of simulation runs of the network, guided by a nonlinear optimization algorithm. The controller parameters in each subsequent run are refined with the aim of achieving a desired performance measure, mathematically represented by an objective function (OF). The paper demonstrates a design procedure, in which the selection of the OF follows an evolutionary path. The system is first designed with an initial OF, which often results in some unforeseen negative system behavior. In the next stage, a new OF is selected, which has the potential for mitigating this negative behavior. This cycle is terminated when a high-quality design is achieved. The procedure is exemplified with the controller design for a 200-MW back-to-back dc scheme to operate within a range of inverter short circuit ratios. The optimality measure considers dynamic changes in controller set-points as well as recovery from faults. Index Terms--Control design, electromagnetic transient simulation (EMTS), HVDC, optimization, robustness.

An optimal neuro-fuzzy external controller is designed in this paper for a static compensator (STATCOM) in the 12-bus benchmark power system. The controller provides an auxiliary reference signal for the STATCOM in such a way that it improves the damping of the rotor speed deviations of its neighboring generators. A Mamdani fuzzy rule base constitutes the core of the controller. A heuristic dynamic programming-based approach is used to further train the controller and enable it to provide nonlinear optimal control at different operating conditions of the power system. Simulation results are provided that indicate the proposed neuro-fuzzy external controller is more effective than a linear external controller for damping out the speed deviations of the generators. In addition, the two controllers are compared in terms of the control effort generated by each one during various disturbances and the proposed neuro-fuzzy controller proves to be more effective with smaller control effort. Index Terms--Adaptive critic designs (ACDs), neuro-fuzzy systems, optimal control, static compensator (STATCOM), supervisory level control.

This brief proposes a novel controller which greatly enhances the performance of a power-factor correction converter. This controller is optimally tuned to place the eigenvalues of the system well inside the unit circle and hence it guarantees stable operation over a wide range of input voltages. The design of the controller is based on the stability analysis of the system using the state transition matrix over a clock cycle. It is shown that the transition matrix across the switching manifold greatly influences the system's performance, allowing the system to be stabilized by periodically altering the manifold. The results are validated by analytical and numerical studies. Index Terms--Bifurcation, control of power electronics, powerfactor correction (PFC).

This paper presents an in depth analysis to show that the conventional power balance model for the dc-side control of the Neutral Point Diode Clamped (NPC) converter is not adequately accurate for all operating conditions. The inaccuracy is due to the fact that the instantaneous power of the ac-side inductors is assumed to be negligible in the power balance equation. This paper shows that this assumption obscures (i) the impact of operating point which is a direct consequence of the inherent nonlinear nature of the problem and (ii) the nonminimum-phase property of the plant in the rectifying mode of operation. Thus, the conventional dc-side control model may lead to unsatisfactory performance or even instability. To overcome the shortcoming, this paper also develops accurate nonlinear and linearized models for the dc-side controller design, including the impact of the ac-side interface reactors. The analytical results and the conclusions are validated by digital time-domain simulation of a study system in the PSCAD/EMTDC environment. The mathematical developments and conclusions of the paper are equally applicable to the conventional two-level VSC. Index Terms--Generalized state-space averaging, multilevel converter, neutral point diode clamped (NPC) converter, nonminimum-phase plant, power balance.

Dynamic rate and power control algorithms for distributed wireless networks that also account for the congestion levels in a network with three schemes of algorithms adaptive scheme, quadratic control scheme and robust scheme is proposed. The algorithm for quadratic control and robust solutions are model-dependent and hence they reveal improved performance over the adaptive solution.

This paper presents the design and analysis of a fixed-frequency pulsewidth modulation (PWM)-based quasi-sliding-mode voltage controller for buck converters from a circuit design perspective. A practical design approach that aims at systematizing the procedure for the selection of the control parameters is presented. In addition, a simple analog form of the controller for practical realization is provided. The resulting controller exhibits the same structure as a PWM proportional derivative (PD) linear controller, but with an additional component consisting of the instantaneous input voltage and the instantaneous output voltage. Simulation and experimental results show that the performance of the converter agrees with the theoretical design. Index Terms--Buck converter, fixed-frequency, hysteresis-modulation, pulsewidth modulation (PWM), quasi-sliding-mode (QSM), sliding-mode (SM) control.

This paper presents a new digital dimming controller (DDC) for the backlight resonant inverter to improve the ignition behavior of the cold cathode fluorescent lamp (CCFL) and, hence, to increase the CCFL's lifespan. The DDC using a soft-starting technique (DDC-SST) is designed and developed to reduce the high ignition voltage and to eliminate the ignition current spikes. A full-bridge resonant inverter is adopted in the backlight system. The design considerations along with a complete analysis for said controller are detailed. Encouraging experimental results in close agreement with the theoretical analysis are also exhibited. The overall system power efficiency is approximately 85%. The ignition voltage is reduced by around 30% without any lamp current spike occurring during the dimming control operation. The apparent advantages of the proposed dimmer are listed in the conclusion. Index Terms--Backlight, cold cathode fluorescent lamp (CCFL), digital dimming, liquid crystal display (LCD), resonant inverter.

In this paper, a current control scheme, based on proportional-integral regulators using sinusoidal signal integrators (SSIs), is proposed for shunt type power conditioners. The aim is to simplify the implementation of SSI-based current harmonic compensation for industrial implementations where strict limitations on the harmonic distortion of the mains' currents are required. To compensate current harmonics, the SSIs are implemented to operate both on positive and negative sequence signals. One regulator, for the fundamental current component, is implemented in the stationary reference frame. The other regulators, for the current harmonics, are all implemented in a synchronous reference frame rotating at the fundamental frequency. This allows the simultaneous compensation of two current harmonics with just one regulator, yielding a significant reduction of the computational effort compared with other current control methods employing sinusoidal signal integrators implemented in stationary reference frame. A simple and robust voltage filter is also proposed by the authors to obtain a smooth and accurate position estimation of the voltage vector at the point of common coupling (PCC) under distorted mains' voltages. The whole control algorithm has been implemented on a 16-b, fixed-point digital signal processor (DSP) platform controlling a 20-kVA power conditioner prototype. The experimental results presented in this paper for inductive and capacitive loads show the validity of the proposed solutions. Index Terms--Digital signal processor (DSP), shunt type power conditioner, sinusoidal signal integrators (SSIs).

This paper considers mobile to base station power control for lognormal fading channels in wireless communication systems within a centralized information stochastic optimal control framework. Under a bounded power rate of change constraint, the stochastic control problem and its associated Hamilton-Jacobi-Bellman (HJB) equation are analyzed by the viscosity solution method; then the degenerate HJ equation is perturbed to admit a classical solution and a suboptimal control law is designed based on the perturbed HJB equation. When a quadratic type cast is used without a bound constraint on the control, the value function is a classical solution to the degenerate HJB equation and the feedback control is affine in the system power. In addition, in this case we develop approximate, but highly scalable, solutions to the HJB equation in terms of a local polynomial expansion of the exact solution. When the channel parameters are not known a priori, one can obtain on-line estimates of the parameters and get adaptive versions of the control laws. In numerical experiments with both of the above cost functions, the following phenomenon is observed: whenever the users have different initial conditions, there is an initial convergence of the power levels to a common level and then subsequent approximately equal behavior which converges toward a stochastically varying optimum. Index Terms--Dynamic programming, Hamilton-Jacobi-Bellman (HJB) equations, lognormal fading channels, power control, quality of service.