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Background: Bone marrow transplantation (BMT) is the treatment of choice for many patients with malignant and nonmalignant diseases. Long-term complications such as osteoporosis should be considered, because it is directly associated with the morbidity and mortality. The purpose of this study is to assess the bone mineral density after allogenic or autologous bone marrow transplantation in patients with leukemia or lymphoma.Methods: We prospectively investigated 63 patients undergoing BMT for acute and chronic leukemia and lymphoma. At the end of the study, a total of 28 patients were assessed. Bone mineral density (BMD) was measured prior BMT, and 6 and 12 months after BMT. Osteocalcin, bone alkaline phosphatase and C-terminal telopeptides of type 1 collagen (ICTP) were assessed. Serum concentration of calcium, phosphorous, vitamin D, PTH and sex hormones (FSH, LH, testosterone and estradiol) were also measured.Results: There was a significant decrease in the bone mineral density of the femoral neck six months after BMT (p

Introduction: Bone marrow transplantation is a good therapeutic modality for beta thalassemia. Liver complications are one of the major causes of morbidity and mortality following BMT. Determination of the factors of liver injury leads to earlier diagnosis after BMT and improves prognosis. Method: We studied 113 major Beta thalassemic patients who have been transplanted from 1990- 2000 in bone marrow transplantation center of Shariati Hospital. 62 were male and 51 were female. 27 pa¬tients were class one, 56 were class two and 30 were class three. The median age of each class were 6.5, 6.3 and 8.7. Conditioning regimen consisted of busulfan (3.5-4mg/Kg) and cyclophophamide (40-50mg/Kg).For GVHD prophylaxis we gave cyclosporine ± metothoroxate. Grade of liver fibrosis de¬fined by biopsy in all patients before BMT. All patients and their donors tested for HBSAg, HBSAb, HCVAb, CMVAb with RIA method. We assessed causes of liver dysfunction before and after trans¬plantation and effect of high ferritin level on liver function."nResults: Hepatic dysfunction in first year after transplantation was seen in 86 (76%) patients. Causes of liver dysfunction were consisted of 53.1% GVHD, 15.93% cyclosporine hepatotoxicity, 7.07% condi¬tioning regimen hepatotoxicity and VOD. In all three classes hepatic GVHD, cyclosporine toxicity, death and normal liver function post BMT had significant relation with hepatic dysfunction before BMT (P=0.001). In patients with ferritin level more than 1000, there were significant hepatotoxicity with conditioning regimen (P=0.001). 17 (15.04%) of patients have been died. Discussion: According to our study hepatic GVHD (%53.1) is the most common cause of hepatic dys¬function in all three classes.

Background: Cisplatin-based chemotherapy is the standard treatment for advanced non-small cell lung cancer (NSCLC). Many novel drugs, including gemcitabine, vinorelbine, paclitaxel and docetaxel have been used in combination with cisplatin in this setting. Of these drugs, gemcitabine is reported to have a high response rate and acceptable toxicity. The aim of this study was to evaluate the efficacy and safety of gemcitabine & cisplatin combination."nMethods: Twenty-three patients with NSCLC, who met inclusion criteria, were enrolled from January 2001 till September 2003. All of them were confirmed by histology and were in advanced stages, i.e. stage IIIB or stage IV. Cisplatin with a dose of 70mg/m2 was given every 21 days, in combination with gemcitabine at a dose of 1250mg/m2 administered on days 1and 8 of a 21-day cycle. Results: of the 23 patients, 1 showed complete remission, 5 achieved partial remission, 7 had stable disease and 2 patients showed progressive disease, while 8 patients were not evaluable for response. The overall response in 15 evaluable patients was 40% (95% CI), median survival was 13.5 months (95% CI, 3.5-27.4 months), and median progression free survival (PFS)was 11 months (95% CI, 1.04-20.9 months)."nHematological toxicities included WHO grade 3, 4 anemia, neutropenia and thrombocytopenia 10%, 7% and 2% respectively. Non-Hematological toxicities included nausea/vomiting WHO grade 1,2 & peripheral neuropathy WHO grade 1,2. Skin rashes were mild.Six patients developed grade 2 toxicity. Renal impairment was mild. One case developed Acute Respiratory distress syndrome (ARDS) after first dose of chemotherapy, another case developed transient acute psychosis under therapy. Conclusions: The regimen of combined gemcitabine with cisplatin is safe and effective and well toler¬ated in patients. Some rare but important toxicity such as ARDS may occur occasionally. In this com¬bination, a lower dose of cisplatin seems to have an efficacy similar to that of in previous reports.

Objective: To evaluate the potential advantages of imipenem/cilastatin in control of fever in neutro-penic HSCT recipients.Patients and Method: In this single-center study, 111 consecutive febrile episodes in 104 neutropenic HSCT recipients with a mean age of 26 years were randomized to treatment either with Imipenem/cilastatin 1 g, IV, q8h or cefepime (our standard regimen) 2 g, IV, q8h. If fever persisted, se¬quential antibiotics were added in 72-hour intervals: vancomycin, amikacin and amphotericin-B. The study population was at serious risk of a poor outcome, since 73.5% of febrile episodes occurred after allogeneic and 26.5% of febrile events occurred after autologous hematopoietic stem cell transplanta¬tion."nResults: The median total duration of neutropenia was 10 days, and the median leukocyte count at study inclusion was 0.16 × 109/l. The two patient groups were comparable in terms of Age, gender, un¬derlying disease, conditioning regimen, clinical and bacterial documentation, severity and duration of neutropenia and mucositis, GI decontamination and G-CSF administration. Bacteremia was found in 20.6%, other microscopically documented infections in 9.8%, clinically documented infections in 20.6% and fever of unknown origin in 49% of the febrile episodes. Most (102) febrile episodes were evaluable for response. No significant difference was found between imipenem/cilastatin and cefepime in terms of success rate (73.1% versus 62%), empirical addition of vancomycin (38% versus 26.2%) or median duration of antibiotic therapy (7 days in both).The difference between imipenem/cilastatin and cefepime was statistically significant for median duration of fever (1.5 versus 2 days) and median time of resolution of neutropenia (12 versus 14 days). The overall response rates to initial monotherapy was significantly higher for HSCT recipients with thalassemia, MM, lymphoma, AA, than recipients with ALL, AML, CML, CLL (P

Background: Graft-versus-host disease is one of the major complications after allogenic bone marrow transplantation, but it is not easy to anticipate the onset. Cytokines released by type 1 T-helper cells are thought to play a pivotal role in acute graft-versus-host disease (aGVHD). The ability to predict the likely occurrence of graft-versus-host-disease (GVHD) after BMT would be extremely valuable. By serially measuring serum levels of soluble IL-2 receptor (sIL-2R), IL-18 and following allogeneic bone marrow transplantation (BMT), we tried to define their relationship to aGVHD as complication of the transplantation and determine useful markers for aGVHD predictors. Materials and Methods: Serum sIL-2R, IL-18, and levels were measured by sandwich ELISA in 219 sera samples from 39 patients (with hematological disorders before and after allogeneic BMT) and 28 controls. All patients received BMT from HLA-identical siblings. Results: 25 patients developed aGVHD and serum levels of sIL-2 R and IL-18 , in sera drawn before transplantation , in patients with acute graft-versus-host disease (aGVHD +) , were increased in comparison of patients without acute graft-versus-host disease (aGVHD ¯) and control group and there wasn’t any significant differences in serum levels of sIL-2 R and IL-18 in aGVHD ¯ patients and controls. Serum level of IL-18, in aGVHD+ patients, was increased during day 3 - 24 after BMT, and there was a significant difference in patients with GVHD 0 – GVHD III. In majority of patients with acute GVHD (60 %) , the peak levels of IL-18 and IL-2R was achieved on day 10 after BMT and the rise in sIL-2R and IL-18 preceded of clinical signs of GVHD (mean day 15 after BMT). Level of IL-18 in patients with aGVHD had strongly correlated with the severity of aGVHD on Day 10 after BMT. IL-18 level mean (before BMT), in patients who received Busulfan and Fludarabin to treat aGVHD, was lower than in patients who received Busulfan - Endoxan, or Cyclophosphamide. Conclusion: Our data concluded that IL-18 plays an important role in the development of aGVHD and IL-18 level might be an indicator for aGVHD, reflecting the severity of the disease. These findings suggest that IL-18 may play important roles in the pathogenesis of aGVHD and that measurement of serum IL-18 levels can be useful predictor of aGVHD.

Given preliminary evidence of timed, sequential chemotherapy of high dose cytosine arabinoside the current study was initiated to assess the side effects and efficacy of this regimen in patients with newly acute myelocytic leukemia (AML). Nineteen adults who referred to Hematology-Oncology and Bone Marrow Transplantation (BMT) research center of Tehran University of Medical Sciences were enrolled in a trial from Aug 1999 to Nov 2000. All patients had a Karnofski classification above 60%. At this time induction therapy consisted of daunorubicin or idarubicin given at a dose of 60 mg/m² and 12 mg/m² IV respectively on days 1-3, and cytarabine (Ara-C) 100 mg/m² intravenously by continuous infusion on days 1-7, followed by Ara-C 1000 mg/m² given on day 8-10 every 12 hours by IV infusion. Consolidation therapy started after 35th day. Of 19 fully evaluable patients, 10 patients achieved a complete remission, whereas 36.6% patients succumbed to death due to regeneration failure. The clinical data show that the overall survival rate from diagnosis 55.5% (95% CI, 30.8-78.5) at 6 months for the entire cohort of the patients. Disease free survival is also 50% (95% CI, 26-74). Mean duration of death due to treatment was 20 days (range 17-29) after beginning the regimen. Presenting WBC counts, French-American-British (FAB) classification, sex and age were not useful prognostic variables. Fever, diarrhea, nausea and vomiting and GI hemorrhage were seen in 19, 6, 4, 7 patients respectively. It seems the 3+7+3 regimen is a promising approach for the AML patients regarding to high complete remission rate, but more supportive care should be considered. Furthermore any, benefit in long-term outcome can’t be determined regardless to the choice of post remission therapy (e.g., GCSF, appropriate antibiotics and etc).

From 1996 to 2002, fifty three patients with major beta-thalassemia received allogeneic peripheral blood stem cell trans¬plantation (PBSCT). Median age was 6 years .Twenty two were class I, 17 class II and 14 class III. All of the donors were HLA-identical. Conditioning regimen for class I and II patients consisted of Cyclophosphamide (CY) 50 mg/kg/day for 4 days + Busulfan (Bu) 3.5 mg/kg for 4 days, while class III patients received 4 mg/kg/day Busulfan for 4 days and 40mg/kg/day Cyclophosphomide for 4 days. G-CSF (Neopogen) 5µ/kg IV was given to donors. Graft Versus Host Disease (GVHD) prophylaxis regimen consisted of Cyclosporin-A (CsA) 3 mg/kg/day plus Methotrexate (MTX) 10 mg/m2 on day+1 and 6 mg/m2 on days +3 and +6. The median time for neutrophil and platelet engraftment was day +16 and day +23 post transplantation, respectively. Chronic GVHD (cGVHD) was observed in 30 patients (56%). Ten patients (18.8%) died. Forty patients are well and transfusion independent. Median time of follow-up was 23 months. Recurrences have been seen at 3 pts, one patient 21 months, the other one 6 months and the last one 8 months after transplantation, who received Donor Lymphocyte infusion (DLI). Event free survival was 72% and overall survival was 80%. In conclusion, we suggest that PBSCT can be considered a safe and effective treatment for children with Beta-thalassemia major and cGVHD is tolerable and manageable in these patients.

This paper presents supervisory control of a dynamic flow controller (DFC) based on the discrete-event systems (DES) theory. A DFC can be considered as a flexible ac transmission system controller and includes a mechanically-switched phase-shifting transformer, a multimodule thyristor-switched capacitor, a multimodule thyristor-switched reactor, and a mechanically switched capacitor. Owing to the inherent discrete switching nature of a DFC, its components are modeled as finite automata; then, a DES supervisory control is designed to implement the control logic of the DFC system in different modes of operation (i.e., 'automatic' and 'auto/manual'). It is shown that the specifications are controllable and the synthesized supervisors are nonblocking in both modes and the modular supervisors nonconflict in auto/manual mode. Index Terms--Discrete-event systems (DES), dynamic flow controller (DFC), power flow, supervisory control.

Without storage provision, a wind energy conversion system (WECS) does not have fault ride-through capability for most temporary faults on the utility feeder. This paper proposes a hybrid valve switching and control strategy for a voltage-sourced converter (VSC) used for interfacing a WECS to the utility grid. The hybrid control of the VSC ensures continuous operation of the system in the presence of temporary single line to ground faults on the utility feeder without the need for a storage provision. The fast acting hybrid control also limits reactive fault current contribution by the converter, and therefore, avoids problems associated with overcurrent protection of the feeder. The hybrid valve switching and control of the VSC consists of: 1) sinusoidal pulse width modulation (SPWM) based valve switching and current-controlled voltage-source operation of the VSC during normal system operating conditions and 2) hysteresis space vector modulation (HSVM) based switching together with controlled current-source operation of the VSC during temporary fault conditions. The hybrid control of the VSC isolates the WECS from the grid side disturbances to ensure uninterrupted operation of the unit. Simulation studies of the grid-interactive WECS in PSCAD/EMTDC confirm the validity of the proposed hybrid control scheme. Index Terms--Hybrid control, induction generator, self-excitation, sinusoidal pulse width modulation (SPWM), space vector modulation, thyristor rectifier, voltage-sourced converter (VSC), wind energy.

This paper presents a new voltage control strategy for an electronically-interfaced distribution generation (DG) unit that utilizes a voltage-sourced converter (VSC) as the interface medium. The control strategy is based on the concept of voltage-controlled VSC (VC-VSC) rather than the conventional current-controlled VSC (CC-VSC). The proposed VC-VSC 1) enables operation of a DG unit in both grid-connected and islanded (autonomous) modes, 2) provides current-limit capability for the VSC during faults, 3) inherently provides an islanding detection method without non-detection zone, 4) provides smooth transition capability between grid-connected and autonomous modes, and 5) can accommodate ride-through capability requirements under a grid-connected mode. This paper also investigates performance of the proposed VC-VSC strategy based on an eigenanalysis in MATLAB, and time-domain simulations in the PSCAD/EMTDC environment. Index Terms--Autonomous operation, distributed generation (DG), islanding detection, ride-through capability, small-signal analysis, voltage-controlled voltage-sourced converter (VC-VSC).

This paper presents a novel dynamic model of a matrix converter (MC) that utilizes a space vector modulation (SVM) switching method. The MC is intended as the interface medium between a distributed resource (DR) unit, e.g., a microturbine-generator, and the utility grid. The MC model is developed in the direct- and quadrature-axis reference frame to be consistent with the utility grid model for dynamic studies. The model can be used for investigation of large signal transients as well as small signal dynamics. The accuracy of the model is validated by comparing the study results obtained from the developed model with those from the exact switched-model of the MC in the PSCAD/EMTDC environment. Index Terms--dq reference frame, dynamic model, matrix converter, space vector modulation.

A thyristor-based static transfer switch (STS) provides a continuous supply for a voltage sensitive load through fast transfer between two sources when the main source does not meet load voltage requirements. This paper investigates the impact of phase difference between the corresponding voltages of the two sources on the load transfer performance achieved by an STS. The studies are performed on the IEEE benchmark STS-1 system using the power system computer-aided design/electromagnetic transient dc simulation software. The studies indicate that the impact of phase difference on the STS load transfer time is insignificant when the sensitive load is a passive (e.g., RL) load. However, if the load can operate in a regenerative mode (e.g., a motor load), the effect of phase difference on the transfer time is noticeable. The studies show that a phase difference of 25[degrees] can increase the load transfer time by about 2 ms. Index Terms--Power quality, sensitive loads, static transfer switch.

This paper investigates the use of an AC-AC matrix converter, as an alternative to AC-DC-AC converter system, to interface a high-speed micro-turbine generator (MTG) to a utility grid as a distributed generation unit. A new switching strategy and a control mechanism for the converter are presented. Based on time-domain simulations in the PSCAD/EMTDC environment, the dynamic behavior of a micro-turbine generation system, including the dynamic models of the micro-turbine (thermodynamics), generator, matrix converter, converter control and micro-turbine control, is studied. The studies conclude that a matrix converter is technically a viable option to interface a MTG to a utility grid. Index Terms--Dynamics, matrix converter, micro-turbine generator (MTG), steady-state.

A recently proposed high power switch-mode rectifier topology offers advantages over the conventional line-commutated thyristor rectifiers in terms of size and cost. This paper presents modeling and analysis of the high power switch-mode rectifier configuration, operated under a newly developed digital control strategy. The developed strategy provides a fast transient response to disturbances and achieves equal current sharing between the buck converter modules which are paralleled within the switch-mode rectifier. A continuous-time state-space model of the switch-mode rectifier and analyses of both the steady-state and the transient operation modes of the digitally controlled rectifier are presented. The continuous-time model is used as a basis for time-domain simulations of the rectifier's behavior in the MATLAB/Simulink environment. The validity of the presented model is demonstrated based on comparison between the simulation results and the corresponding experimental results. The experimental results are obtained from a 2-kW scaled-down laboratory setup of the rectifier. The stability of the digitally controlled rectifier system is also examined based on an overall small-signal sampled-data model of the rectifier system including the controls. Index Terms--Switch-mode rectifier topology, time-domain simulations.

A novel method of extraction and measurement of individual harmonics of a signal with time-varying frequency is presented. The proposed method is based on a nonlinear, adaptive mechanism. Compared with the well-established techniques such as DFT, the proposed method offers (i) higher degree of accuracy, (ii) structural/performance robustness, and (iii) frequency-adaptivity. The structural simplicity of the algorithm renders it suitable for both software and hardware implementations. The limitation of the proposed method as compared with DFT-based methods is its slower transient response. Based on simulation studies, performance of the method is presented and its accuracy and response time are compared with a DFT-based method. Index Terms--Harmonics detection and extraction, harmonics measurement, inter-harmonics, power quality, time-varying frequency.

This paper presents a new synchronization method which employs an enhanced phase-locked loop (EPLL) system. The operational concept of the EPLL is novel and based on a nonlinear dynamical system. As compared with the existing synchronization methods, the introduced EPLL-based synchronization method provides higher degree of immunity and insensitivity to noise, harmonics and other types of pollutions that exist in the signal used as the basis of synchronization. The salient feature of the EPLL-based synchronization method over conventional synchronization methods is its frequency adaptivity which permits satisfactory operation when the centre frequency of the base signal varies. The proposed EPLL-based method of synchronization is also capable of coping with the unbalanced system scenarios. Structural simplicity of the EPLL-based method greatly simplifies its implementation in digital software and/or hardware environments as an integral part of a digital control platform for power electronic converters. The primary application of the proposed synchronization method is for the distributed generation units, e.g., wind generation systems, which utilize power electronic converters as an integral part of their systems. Index Terms--Distributed generators, phase angle estimation, synchronization, PLL, power systems.

A signal processing system for extraction of harmonic and reactive current components is introduced and its performance is evaluated. The extraction system is adopted as part of the control system of a single-phase active power filter (APF) to provide the required signals for harmonic filtering and reactive power compensation. Performance of the overall system is evaluated based on digital time-domain simulation studies. The APF control system including the signal processing algorithms are implemented in Matlab/Simulink Fixed-Point Blockset to accommodate bit-length limitation which is a crucial factor in digital implementation. The power system including the APF, load and the supply system are simulated with the PSCAD/EMTDC software to which the Matlab-based control model is interfaced. The simulation results indicate that the signal processing unit can provide the required signals for APF to perform filtering/compensation within the transient period of 2 to 3 cycles. Index Terms--APF, FACTS, harmonics, power factor adjustment, reactive current, STATCOM.

This paper introduces a new phase-locked loop (PLL) system. The proposed system provides the dominant frequency component of the input signal and estimates its frequency. The mechanism of the proposed PLL is based on estimating in-phase and quadrature-phase amplitudes of the desired signal and, hence, has application advantages for communication systems which employ quadrature modulation techniques. The studies demonstrate that the proposed PLL also provides a superior performance for power system applications. Derivation of the mathematical model and theoretical stability analysis of the proposed PLL are carried out using dynamical systems theory. Advantages of the proposed PLL over the conventional PLLs are its capability of providing the fundamental component of the input signal which is not only locked in phase but also in amplitude to the actual signal while providing an estimate of its frequency. Computer simulation is used to evaluate its performance. Evaluations confirm structural robustness of the proposed PLL with respect to noise and distortions. Index Terms--Frequency estimation, peak detectors, phase detection, phase-locked loops (PLLs), power system state estimation, quadrature amplitude modulation, synchronization.

Conventionally, control system of a static transfer switch (STS) is designed based on the assumption that the STS terminal voltages are in-phase. This paper investigates the impact of phase difference of the STS terminal voltages on the STS transfer time and cross current. The phase difference is assumed to be a result of the difference of the feeder impedances. The paper shows that phase differences of even up to 4.5 [degrees], which are accompanied by up to 5% voltage drop at the STS terminal, can noticeably increase the transfer time and the cross current magnitude. The studies are conducted on the IEEE STS-1 benchmark system using the PSCAD/EMTDC software. Index Terms--Load transfer, power quality, sensitive loads, static transfer switch.

A new approach for measuring the peak value of the fundamental component of a distorted sinusoidal signal for power system applications is presented. The method is applicable to single-phase as well as three-phase systems. While maintaining structural simplicity, the proposed approach is highly robust with respect to noise and distortion due to disturbances and unbalanced conditions of the system. The method is also highly tolerant of uncertainties in the setting of its internal parameters. The salient feature of the proposed approach is its capability of adapting to the variations in the center frequency of the input signal. The method is suitable for environments that frequency excursions are experienced and conventional discrete Fourier transform (DFT)-based methods do not provide satisfactory results. Speed and accuracy of the response can also be controlled. Structural simplicity and robustness of the proposed scheme make it well suited for digital implementation on software and hardware platforms. Performance of the proposed method is presented based on simulation studies in the MATLAB environment and an experimental setup. Index Terms--Amplitude measurement, frequency adaptive, peak measurement.

This paper deals with the calculation of a sparse network equivalent (SNE) for the analysis of electromagnetic transients in large systems. The methodology and the mathematical details are presented in the companion paper [1]. This sequel presents application examples to demonstrate the accuracy and computational efficiency of the SNE. Equivalents for networks composed of 12, 50, and 100 transmission lines are derived and the results are discussed. Index Terms--Discrete time, electromagnetic transients, network equivalent, quadratic programming, time-domain fitting.

This paper deals with the calculation of a sparse network equivalent (SNE) for the analysis of electromagnetic transients in large systems. The main feature of the new approach is the enforcement of sparsity, stability, passivity, and accuracy at specific frequencies of the equivalent. The procedure is based on time-domain fitting with quadratic programming to enforce the constraints. The SNE can be interfaced with transient calculation programs directly in time domain. Results are presented in the companion paper. Index Terms--Discrete time, electromagnetic transients, network equivalent, quadratic programming, time-domain fitting.

The frequency spectrum of an external system used in the simulation of electromagnetic transients shows many peaks due to resonance effects of the leading transmission lines. Therefore, the two-level equivalent we developed contains simplified lines for the leading part of the system and lumped elements represented by rational functions as a correction for the rest of the external system. This leads to a computationally more efficient model, over a wide frequency range, than the existing equivalents with only lumped parameter components. The paper describes how the parameters of the new equivalent are optimized for most accurate fitting of the input admittance while assuring its positive realness and accuracy at dc and power frequency. Generators in the external system are represented in the equivalent as Norton current sources at the connecting terminals. The equivalents can be single or multiport. Index Terms--External equivalents, multiport system, Norton equivalent, positive realness, quadratic programming, rational approximation, sequential quadratic programming.

Fast (subcycle) bus transfer by means of a static transfer switch (STS) requires short time intervals for detection and transfer process. Due to these time intervals, the load transformer is subjected to a transient process which can be accompanied by large transient current components through the transformer. The transient current, in turn, can cause voltage sag at the load terminal. The STS control logic must be able to distinguish such a voltage sag from those due to the supply disturbances and not disconnect the load. This paper provides simplified analytical expressions to predict F of the load transformer which can be used to estimate the corresponding voltage sag. PSCAD/EMTDC-based digital simulation of the actual nonlinear system is also carried out to substantiate the validity of the analytical expressions. Index Terms--Load transformer, power quality, sensitive loads, static transfer switch.

This paper provides an adaptive filter for synchronous detection and extraction of harmonics. The filter can he used as integral part of the control system of a power electronic apparatus (e.g., STATCOM, APF, and UPFC) to generate the desired control signals. Stability and convergence analyses of the adaptive filter are presented based on dynamical systems theory. Performance of the filter is verified as a means for reference signal generation in a shunt active power filter. Index Terms--Active power filter, adaptive filter, averaging theorem, synchronous harmonic detection.

This paper presents a unified power signal processor (PSP) for use in various applications in power systems. The introduced PSP is capable of providing a large number of signals and pieces of information which are frequently required for control, protection, status evaluation, and power quality monitoring of power systems. The PSP receives a set of locally measured three-phase voltage and current signals and provides their fundamental components, amplitudes, phase angles, frequency, harmonics, instantaneous and stationary symmetrical components, active and reactive currents and powers, power factor, and the total harmonic distortion. Simplicity and integrity of its structure as well as its robustness with respect to internal parameters and external disturbances and noise render the proposed scheme very attractive for practical implementations. Index Terms--Amplitude detection, frequency estimation, harmonic analysis, phase detection, PLL, power signal processing, reactive current extraction, symmetrical components, synchronization, THD.

High power switch-mode rectifiers offer advantages over conventionally used line-commutated thyristor rectifiers in terms of size and cost. This paper describes operation of the high power switch-mode rectifier based on an original control strategy which is digitally implemented. The rectifier is operated in a constant output current mode. The control strategy provides a fast transient response to disturbances and achieves equal current sharing between the buck converter modules which are paralleled within the switch-mode rectifier. Equal current sharing is maintained in steady-state as well as in transient operation. The paper demonstrates that the transient response to load disturbances achievable with the proposed control strategy is superior to the response obtained with the conventional control strategy in terms of the output current overshoot and the settling time. The control algorithm is digitally implemented on a DSP/FPGA based digital control platform and its performance is verified on a 2 kW scaled-down experimental setup of the switch-mode rectifier. Index Terms--Current sharing, digital control, power converter, rectifier, switch-mode.

This paper presents various applications of a nonlinear adaptive notch filter which operates based on the concept of an enhanced phase-locked loop (PLL). Applications of the filter for online signal analysis for power systems protection, control and power quality enhancement are presented. The proposed scheme can be applied for signal analysis both under stationary and non-stationary conditions. Based on digital time-domain simulations, applications of the filter for a) sinusoidal waveform peak detection, b) harmonic identification/detection, c) detection/extraction of individual components of a signal, d) instantaneous reactive current extraction, e) disturbance detection, f) noise reduction in zero-crossings detection, and g) amplitude (phase) demodulation for flicker estimation, are presented. Index Terms--Amplitude/phase demodulation, flicker estimation, harmonic extraction, notch filter, phase-locked loop (PLL), reactive current extraction, sinusoidal peak detector, spectrum analysis, zero-crossings detection.

Thyristor-based static transfer switches (STSs) are used in uninterruptible power supply systems and in distribution networks to provide connection to alternate sources of ac power for critical loads when the main sources fail. However, performance of STSs from a transfer-time point of view has not been reported in the technical literature. This performance evaluation is a complex issue due to the dependence of the transfer time on gating scheme and commutation between thyristors. This paper provides a thorough analysis of a fast gating strategy for STS systems. It derives analytical expressions to estimate the transfer time for different operating conditions and identifies the worst case scenario(s) in which maximum transfer time occurs. The analytical results are validated based on time-domain simulation studies using a PSCAD/EMTDC package for a medium-voltage system. The simulation results are verified based on comparison with those obtained from an experimental setup. Index Terms--Bus transfer, power quality, sensitive loads, static transfer switch, UPS systems.

The paper presents an approach for network equivalent calculation for the analysis of electromagnetic transients in power systems. It is based on time-domain fitting and enforces some degree of sparsity while preserving the accuracy of the equivalent. The calculated equivalent is appropriate for direct interface with the rest of the system in time-domain. A constrained least squares solution of the time-domain fitting equations is used to ensure accuracy at 0 and 60 Hz. Results demonstrating the accuracy and computational efficiency of the method are presented. Index Terms--Constrained least squares, discrete time, electromagnetic transients, network equivalent, time-domain fitting.

This paper evaluates performance of a wavelet-based, on-line (real-time) voltage detection scheme for power quality applications. The objectives are: 1) to demonstrate suitability of the proposed method in detecting faults/disturbances in a power system and 2) to compare its performance with that of a conventional scheme. Two (STS) systems are chosen as frameworks for comparison; a low-voltage laboratory STS setup for which measured results are provided, and a medium-voltage STS system for which detection times are derived based on simulation, using the EMTDC/PSCAD. Index Terms--Power quality, sensitive loads, static transfer switch, voltage detection, wavelet transform.