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Due to ongoing research work, a prototype test rig for testing high speed motors/generators has been developed. Its design is quite unique as the two high speed machines share a single shaft with no support bearings between them. A very high maximum operating speed, up to 80,000 rpm, was required. Because of the need to minimise vibration during operation at very high rotational speeds, rolling bearings were used. To eliminate the influence of higher harmonics of supply voltage and current on the formation of torque oscillations on the shaft and excessive losses in the form of heat, a voltage source inverter with high switching silicon carbide (SiC) power transistors characterizing high precision of the output voltage generation with a fundamental harmonic frequency of several kilohertz has been used. During the first start-ups, it turned out that the system was not stable, and a failure occurred. The paper presents the consequences that may arise when a machine operating at a speed of about 70,000 rpm fails. The article contains pictures of a generator failure that occurred at a high rotational speed.

Summary Mammalian DNA base excision repair (BER) is accelerated by poly(ADP-ribose) polymerases (PARPs) and the scaffold protein XRCC1. PARPs are sensors that detect single-strand break intermediates, but the critical role of XRCC1 during BER is unknown. Here, we show that protein complexes containing DNA polymerase β and DNA ligase III that are assembled by XRCC1 prevent excessive engagement and activity of PARP1 during BER. As a result, PARP1 becomes “trapped” on BER intermediates in XRCC1-deficient cells in a manner similar to that induced by PARP inhibitors, including in patient fibroblasts from XRCC1-mutated disease. This excessive PARP1 engagement and trapping renders BER intermediates inaccessible to enzymes such as DNA polymerase β and impedes their repair. Consequently, PARP1 deletion rescues BER and resistance to base damage in XRCC1−/− cells. These data reveal excessive PARP1 engagement during BER as a threat to genome integrity and identify XRCC1 as an “anti-trapper” that prevents toxic PARP1 activity., Graphical abstract, Highlights • XRCC1 prevents endogenous PARP1 trapping during DNA base excision repair • PARP1 trapping impedes base excision repair and increases sensitivity to base damage • In the absence of PARP1, XRCC1 is dispensable for DNA base excision repair, Demin et al. show that the essential role of the scaffold protein XRCC1 during DNA base excision repair is to prevent toxic “trapping” of PARP1 on SSB intermediates, which otherwise block this essential repair process and lead to increased cellular sensitivity to DNA base damage.

In the article, the authors reviewed the arresting gears used in military aviation. The second part of this part describes the operation concept that is used in the Polish Air Force, in relation to the two types of gears, namely the post-Soviet ones that are still in service, and the second one: of U.S. production obtained due to the purchase of F-16 aircraft. The authors emphasize that in the case of an appropriate operation system, it is possible to extend the service life of devices and maintain safety of the air operations.

Genetic defects in the repair of DNA single-strand breaks (SSBs) can result in neurological disease triggered by toxic activity of the single-strand-break sensor protein PARP1. However, the mechanism(s) by which this toxic PARP1 activity triggers cellular dysfunction are unclear. Here we show that human cells lacking XRCC1 fail to rapidly recover transcription following DNA base damage, a phenotype also observed in patient-derived fibroblasts with XRCC1 mutations and Xrcc1−/− mouse neurons. This defect is caused by excessive/aberrant PARP1 activity during DNA base excision repair, resulting from the loss of PARP1 regulation by XRCC1. We show that aberrant PARP1 activity suppresses transcriptional recovery during base excision repair by promoting excessive recruitment and activity of the ubiquitin protease USP3, which as a result reduces the level of monoubiquitinated histones important for normal transcriptional regulation. Importantly, inhibition and/or deletion of PARP1 or USP3 restores transcriptional recovery in XRCC1−/− cells, highlighting PARP1 and USP3 as possible therapeutic targets in neurological disease., Adamowicz et al. report that toxic PARP1 activity, induced by ataxia-associated mutations in XRCC1, impairs the recovery of global transcription during DNA base excision repair by promoting aberrant recruitment and activity of the histone ubiquitin protease USP3.

POLQ is a key effector of DSB repair by microhomology-mediated end-joining (MMEJ) and is overexpressed in many cancers. POLQ inhibitors confer synthetic lethality in HR and Shieldin-deficient cancer cells, which has been proposed to reflect a critical dependence on the DSB repair pathway by MMEJ. Whether POLQ also operates independent of MMEJ remains unexplored. Here, we show that POLQ-deficient cells accumulate post-replicative ssDNA gaps upon BRCA1/2 loss or PARP inhibitor treatment. Biochemically, cooperation between POLQ helicase and polymerase activities promotes RPA displacement and ssDNA-gap fill-in, respectively. POLQ is also capable of microhomology-mediated gap skipping (MMGS), which generates deletions during gap repair that resemble the genomic scars prevalent in POLQ overexpressing cancers. Our findings implicate POLQ in mutagenic post-replicative gap sealing, which could drive genome evolution in cancer and whose loss places a critical dependency on HR for gap protection and repair and cellular viability.

A novel non-isolated resonant quasi-impedance (quasi-Z)-source network DC–DC converter is proposed. The resonant impedance source network is derived from the quasi-Z-source network by including the autotransformer-based resonant cell instead of the second inductor of the quasi-Z-network. The leakage inductance of the autotransformer and two resonant capacitors connected in series with the autotransformer windings constitute a high-frequency resonant tank. At the same time, the resonant capacitors block the DC-bias current of the autotransformer. The resonant operation with a sinusoidal current of the main switch and diodes enables electromagnetic interference mitigation and improves the efficiency of the converter. Experimental results of a 100 W, 30 V/200 V prototype are presented to verify the analysis results of the proposed converter.

DNA-dependent protein kinase catalytic subunit (DNA-PKcs) controls one of the most frequently used DNA repair pathways in a cell, the non-homologous end joining (NHEJ) pathway. However, the exact role of DNA-PKcs in NHEJ remains poorly defined. Here we show that NOTCH1 attenuates DNA-PKcs-mediated autophosphorylation, as well as the phosphorylation of its specific substrate XRCC4. Surprisingly, NOTCH1-expressing cells do not display any significant impairment in the DNA damage repair, nor cellular survival, and remain sensitive to small molecule DNA-PKcs inhibitor. Additionally, in vitro DNA-PKcs kinase assay shows that NOTCH1 does not inhibit DNA-PKcs kinase activity, implying that NOTCH1 acts on DNA-PKcs through a different mechanism. Together, our set of results suggests that NOTCH1 is a physiological modulator of DNA-PKcs, and that it can be a useful tool to clarify the mechanisms by which DNA-PKcs governs NHEJ DNA repair.

ATM kinase is a master regulator of the DNA damage response (DDR). A recently published report from the d’Adda di Fagagna laboratory1 sheds a light onto our understanding of ATM activation. In this short-commentary we will expand on this and other work to perceive better some of the aspects of ATM regulation.

Mammalian DNA base excision repair (BER) is an essential pathway comprised of damaged base excision by a DNA glycosylase, incision by AP endonuclease-1 (APE1), end processing and gap filling by DNA polymerase β (POLβ), and DNA ligation by DNA ligase I (LIG1) or DNA ligase III (LIG3). In mammals, BER additionally employs PARP1 and/or PARP2 and the scaffold protein XRCC1 to accelerate and coordinate the overall process. Whereas PARP1 and PARP2 are sensor proteins that detect unrepaired DNA single-strand breaks, the essential role of XRCC1 during BER is unknown. Here, we have identified this role. We show that the DNA repair protein complexes that are assembled by XRCC1 compete with and prevent excessive PARP1 engagement during BER, which otherwise leads to PARP1 ‘trapping’ on BER intermediates in a manner reminiscent of that induced by clinical PARP inhibitors. We demonstrate that this elevated engagement and trapping of PARP1 collectively renders BER intermediates inaccessible to POLβ and impedes their repair. Consequently, PARP1 deletion rescues both the accessibility and repair of BER intermediates in XRCC1-/- cells, and also their cellular resistance to DNA base damage. These data demonstrate that PARP1 trapping is an endogenous threat to genome integrity, and identify XRCC1 as an “anti-trapper” that prevents the toxic binding of PARP1 to BER intermediates to ensure their efficient repair.

Summary The DNA damage response (DDR) signal transduction pathway is responsible for sensing DNA damage and further relaying this signal into the cell. ATM is an apical DDR kinase that orchestrates the activation and the recruitment of downstream DDR factors to induce cell-cycle arrest and repair. We have previously shown that NOTCH1 inhibits ATM activation upon DNA damage, but the underlying mechanism remains unclear. Here, we show that NOTCH1 does not impair ATM recruitment to DNA double-strand breaks (DSBs). Rather, NOTCH1 prevents binding of FOXO3a and KAT5/Tip60 to ATM through a mechanism in which NOTCH1 competes with FOXO3a for ATM binding. Lack of FOXO3a binding to ATM leads to the loss of KAT5/Tip60 association with ATM. Moreover, expression of NOTCH1 or depletion of ATM impairs the formation of the FOXO3a-KAT5/Tip60 protein complex. Finally, we show that pharmacological induction of FOXO3a nuclear localization sensitizes NOTCH1-driven cancers to DNA-damage-induced cell death., Graphical Abstract, Highlights • NOTCH1 does not inhibit recruitment of ATM to DSBs • NOTCH1 competes with FOXO3a for binding to the FATC domain of ATM • FOXO3a is necessary for KAT5/Tip60 binding to ATM • Induction of FOXO3a nuclear localization sensitizes TALL-1 cancer cells to DNA damage, Adamowicz et al. show that NOTCH1 inhibits ATM not by impairing ATM recruitment to the DSBs but by blocking formation of a three-protein complex composed of ATM, FOXO3a, and KAT5/Tip60. NOTCH1 competes with FOXO3a for binding to the FATC domain of ATM, resulting in NOTCH1-mediated ATM kinase inhibition.

DNA double-strand breaks (DSBs) are toxic DNA lesions which, if not properly repaired, may lead to genomic instability, cell death and senescence. Damage-induced long non-coding RNAs (dilncRNAs) are transcribed from broken DNA ends and contribute to DNA damage response (DDR) signaling. Here we show that dilncRNAs play a role in DSB repair by homologous recombination (HR) by contributing to the recruitment of the HR proteins BRCA1, BRCA2, and RAD51, without affecting DNA-end resection. In S/G2-phase cells, dilncRNAs pair to the resected DNA ends and form DNA:RNA hybrids, which are recognized by BRCA1 and promote its recruitment to DSBs. We also show that RNase H2 is in a complex with the HR proteins BRCA1, PALB2, BRCA2, and RAD51, and that it localizes to DSBs in the S/G2 cell-cycle phase. BRCA2 controls DNA:RNA hybrid levels at DSBs by mediating RNase H2 recruitment and, therefore, hybrids degradation. These results demonstrate that regulated DNA:RNA hybrid levels at DSBs contribute to HR-mediated repair.

DNA double-strand breaks (DSBs) are toxic DNA lesions, which, if not properly repaired, may lead to genomic instability, cell death and senescence. Damage-induced long non-coding RNAs (dilncRNAs) are transcribed from broken DNA ends and contribute to DNA damage response (DDR) signaling. Here we show that dilncRNAs play a role in DSB repair by homologous recombination (HR) by contributing to the recruitment of the HR proteins BRCA1, BRCA2, and RAD51, without affecting DNA-end resection. In S/G2-phase cells, dilncRNAs pair to the resected DNA ends and form DNA:RNA hybrids, which are recognized by BRCA1. We also show that BRCA2 directly interacts with RNase H2, mediates its localization to DSBs in the S/G2 cell-cycle phase, and controls DNA:RNA hybrid levels at DSBs. These results demonstrate that regulated DNA:RNA hybrid levels at DSBs contribute to HR-mediated repair., Long non-coding RNAs transcribed at DNA damaged sites can play part in DNA damage response. Here the authors reveal that damaged induced lncRNAs can form DNA:RNA hybrids at resected DNA-ends. These hybrids are involved in recruiting HR-mediated repair machinery which, in turn, controls their level at DSBs.

The DNA-damage response (DDR) ensures genome stability and proper inheritance of genetic information, both of which are essential to survival. It is presently unclear to what extent other signaling pathways modulate DDR function. Here we show that Notch receptor binds and inactivates ATM kinase and that this mechanism is evolutionarily conserved in Caenorhabditis elegans, Xenopus laevis and humans. In C. elegans, the Notch pathway impairs DDR signaling in gonad germ cells. In mammalian cells, activation of human Notch1 1 leads to reduced ATM signaling in a manner independent of Notch1 1 transcriptional activity. Notch1 binds directly to the regulatory FATC domain of ATM and inhibits ATM kinase activity. Notch1 1 and ATM activation are inversely correlated in human breast cancers, and inactivation of ATM by Notch1 1 contributes to the survival of Notch1-driven leukemia cells upon DNA damage.

The paper presents closed-loop electric vehicle (EV) drive with 5-phase induction motor operating with switched-autotransformer (LCCAt) inverter. Electrical drives with five-phase induction motors are considered for application in electric vehicles. Space vector modulation (SVM) is the most common option for controlling a five-phase inverter. However, if the battery level cannot ensure the controllability over a wide speed range of EV drive, the supply voltage has to be elevated. Bidirectional impedance source inverters (e.g. Z-source inverter, qZ-source inverter) have been presented suitable for EVs. The concept of Z-source/qZ-source inverters has been recently extended to transformer-based inverters (e.g. Trans-Z-source inverter, T -source inverter) which use coupled inductors with an appropriate turns ratio. Unfortunately, coupled inductors store significant portion of the energy during boost operation which tends their cores to saturate at higher currents. The use of four element LCCAt-source (inductor-capacitor-capacitor- autotransformer) network allows proposed switched- autotransformer inverter for obtaining high voltage gain while ensuring high modulation index and reduced volume of inductive elements. Simulation and preliminary experimental results using the laboratory model of switched-autotransformer inverter with designed 4.3 kW, 30V five-phase induction motor are shown to verify the effectiveness of the proposed system.

Z-source inverters (ZSIs) are suited for applications which require a large range of voltage gain, such as in fuel cells. The present paper extends the concept of ZSIs. New type high step-up LCCT-Z-source inverter dedicated for fuel cells is proposed in the paper. Compared to recently proposed modifications of basic Z-source inverter the new topology has the advantages of available continuous input current, improved boost ratio and simple topology. Thanks to application of transformer with turns ratio higher than one the proposed LCCT-Z-source can operate with lower shoot-through ratio and higher modulation index compared to ZSI. The existence of two built-in DC-current-blocking capacitors connected in series with transformer windings prevents the transformer core from saturation. Simulation and experimental results are provided to verify the reliability of the proposed topology.

Curcumin, a natural polyphenol derived from the rhizome of Curcuma longa , is a potent anticancer agent, which restricts tumor cell growth both in vitro and in vivo. Thus far curcumin was shown to induce death of cancer cells. This study reports the induction of cellular senescence of human colon cancer cells HCT116 upon curcumin treatment. The SA-β-galactosidase activation was observed both in p53+/+ and p53−/− cells, however the latter ones were less sensitive to the prosenescent activity of curcumin. Upregulation of p53 and p21 proteins was observed in p53+/+ HCT116, while p53-independent induction of p21 was noticed in p53−/− HCT116. Moreover, the senescence of HCT116 cells was accompanied by autophagy, that was confirmed by electron microscopy observations of autophagosomes in the curcumin-treated cells as well as LC3-II expression, punctue staining of LC3 and increased content of acidic vacuoles. Inhibition of autophagy, due to the diminished expression of ATG5 by RNAi decreased the number of senescent cells induced by curcumin, but did not lead to increased cell death. Altogether, we demonstrated a new antitumor activity of curcumin leading to cancer cell senescence and revealed the presence of a functional link between senescence and autophagy in curcumin-treated cells.

Advanced control systems combined with high speed gate driver circuits enable extremely high rate of change of power devices voltages, up to hundreds of kV/us. Short rise times of power devices could cause significant EMC problems, which are unacceptable in majority of power electronics applications. It is known that voltage variations during diode switch-off depend on how long it takes for the charge stored near the p-n junction to be recovered during voltage reversing. In fast switching applications good forward recovery characteristics are needed. The silicon carbide (SiC) diodes characterize almost zero reverse recovery charge. However the lossless operation in connection with extremely high dv/dt could cause the SiC diodes less effective in damping the voltage ringing. The compromise between high efficiency and low EMI emission is therefore the actual aim of the research. The paper compares the static and dynamic characteristics of ultra fast silicon (Si) and SiC Schottky diodes and presents the study of the mechanism of parasitic high frequency oscillations during turn-off transient.

This paper presents the steady-state analysis of the voltage-fed quasi-Z-source inverter (qZSI) with cascaded (two-stage) quasi-Z-source network (qZS-network). Cascaded qZS-network is derived by the adding of one diode, one inductor and two capacitors to the traditional qZSI. Main focus of this paper is on mathematical models of the cascaded qZS-converter. Static models were elaborated and analyzed for the continuous (CCM) and discontinuous conduction mode (DCM) of the converter. In order to verify the theoretical assumptions a prototype has been built. The experimental results are presented and analyzed.

Many renewable generation units (e.g. PVs, fuel cells, small wind turbines) require integrated DC-AC converters providing efficient high step-up power conversion. The recently proposed Z-source-type integrated buck-boost inverters characterize one stage energy processing and wide range of output voltage regulation. This paper presents the possibility of further extending Z-source-type inverters application area through the topology reconfiguration. The unique property of the proposed Z-source-type inverter with applied high frequency transformer and built-in DC current blocking capacitors is that no energy is stored in the transformer windings. That prevents core saturation and enables high voltage gain. Simulation and experimental results are shown to verify the proposed topology.

Recent achievements related to the use of silicon carbide (SiC) devices in wind generation systems (WGSs) are presented in the paper. With applications in WGS, the choice of high-temperature, high-frequency SiC devices reduces the volume and size of power electronic converters, particularly their passive filters which dominate the weigh of the converter. The SiC-based power converters are expected to have three times lower losses than silicon-based AC-DC-AC converters currently applied to the wind turbines. Efficiency improvement can be particularly significant at low wind speeds where the WGS operates most of the time. The paper presents results obtained for the 30A 1200V generator side SiC JFET-based DC-AC converter with a switching frequency 100 kHz. The prototype was worked out and investigated at the Gdansk University of Technology. A special attention is paid to the performance of two stage DC-coupled gate driver circuit. Static and dynamic characteristics of 1200V SiC devices (JFETs and Schottky diodes) used in the WGS DC-AC converter are investigated. An approach to suppression of undesirable oscillations/EMI problems caused by the high dv/dt of SiC devices is presented.

The application of current source inverters (CSI) in induction motor (IM) drives offers a number of advantages, including: voltage boosting capability, natural shoot-through short-circuit protection and generation of sinusoidal voltages. The exact generation of sinusoidal voltages is possible thanks to thanks to the effect of the output ac filter capacitors and may improve the accuracy of sensorless IM control. The elimination of high dv/dt in CSI fed IM drives provides also a noticeable electromagnetic interference (EMI) reduction. The paper presents recent achievements of current source inverters (CSI) which are the use of new genertion silicon carbide (SiC) devices (normally-off SiC JFETs and SiC Schottky diodes) and the application of modern nonlinear control which may considerably improve the performance of CSI fed IM drives.

Many renewable generation units (e.g. PVs, fuel cells, small wind turbines) require integrated DC-AC converters providing efficient high step-up power conversion. On the basis of recent developments in impedance source (Z-source) inverters the present paper proposes an integration of quasi-Z-source inverter (qZSI) with a built-in high frequency transformer. Two new type LCCT-Z-Source inverters are presented by author. Proposed inverters characterize continuous input current, improved relationship between boost coefficient and modulation index and improved EMI performance. Application of four element (Inductor — Capacitor — Capacitor — Transformer) LCCT impedance network provides higher voltage gain than obtained in quasi-Z-source inverter. The advantage of proposed topology over other recently developed trans Z-source inverters (TZSI) is that two built-in capacitors block DC currents in transformer windings and prevents core saturation. Simulation and experimental results are shown to verify the proposed topologies.

Cooperation of small generation units within distributed generation system or micro-grid require solving many communication, control and data transmission problems. A wind energy conversion system (WECS) with squirrel cage induction generator (SCIG) and a full-scale power converter is considered in present paper. Application of wireless communication in WECS is discussed in the paper. Some experimental results are presented.

This paper presents an optimization possibility of the voltage-fed continuous input current quasi-impedance source inverter (qZSI) by the introduction of the two-stage quasi-Z-source network (qZS-network). The two-stage qZS-network could be derived by the adding of one diode, one inductor and two capacitors to the traditional qZSI. The proposed two-stage qZSI inherits all the advantages of the traditional solution (voltage boost and buck functions in a single stage, continuous input current and improved reliability). Moreover, the proposed solution features over 30% shoot-through duty cycle reduction for the same voltage boost factor as compared to the conventional qZSI. Theoretical analysis of the two-stage qZSI in shoot-through and non-shoot-through operating modes is presented. The proposed and traditional qZS-networks are compared. A prototype has been built to verify the theoretical assumptions. The experimental results are presented and analyzed. Finally, a further optimization method of the proposed two-stage qZS-network is discussed.

This paper proposes the performance improvement method for the voltage-fed continuous input current quasi-impedance source inverter (qZSI) by the introduction of the two-stage quasi-Z-source network (qZS-network). The two-stage qZS is derived by the adding of one diode, one inductor and two capacitors to the traditional qZSI. The proposed two-stage qZSI inherits all the advantages of traditional solution (voltage boost and buck functions in a single stage, continuous input current and improved reliability). Moreover, the proposed solution features over the 30% shoot-through duty cycle reduction for the same voltage boost factor and component stresses as compared to conventional qZSI. Theoretical analysis of the two-stage qZSI in shoot-through and non-shoot-through operating modes is presented. The design guidelines for the two-stage qZS-network based step-up DC/DC converter are provided. A prototype has been built to verify the theoretical assumptions. The simulation and experimental results are presented and discussed.

Wind energy conversion systems (WECS) seem to be self-evident elements of the future smart grids. Among many generator types the squirrel cage induction generator (SCIG) characterizes robustness and low cost. A full-scale power converter can perform smooth grid connection over wide speed range of multiple-stage geared SCIG. Increasing number of sensors can improve the WECS control and diagnostics but increasing number of thin wires i.e. between a nacelle and the converter housing can reduce reliability. A wireless communication using ADF7020 transceiver for data acquisition and transmission is proposed in the paper.

Variable speed cascaded doubly fed induction generators (CDFIG) have been recently proposed to apply in renewable energy generation systems i.e. small hydropower plants, windmills, shaft generators of vessels and embedded applications. CDFIG requires lower maintenance than DFIG due the absence of slip rings and brushes. It can operate with secondary side converter with fractional ratings of the total power. The use of power factor corrector (PFC) rectifiers to handle the CDFIG slip power is investigated in the paper. The three-phase Minnesota rectifier and a three-phase/switch/level PWM rectifier called Vienna rectifier are considered. Simulations using PSIM simulation software are presented.

This paper presents different topologies of voltage inverters with alternative input LC networks. The basic topology is known in the literature as a Z-source inverter (ZSI). Alternative passive networks were named by the authors as T-sources. T-source inverter has fewer reactive components in comparison to conventional Z-source inverter. The most significant advantage of the T-source inverter (TSI) is its use of a common voltage source of the passive arrangement. Experimental results for the TSI are in agreement with theoretical and simulated prediction.

This paper presents different topologies of buck-boost converters with passive input networks that have alternative topologies; this is known in the literature as a Z-source inverter. Alternative passive networks were named by the authors as T-inverters; these improve output voltage regulation of the PWM inverters. T-inverter has fewer reactive components in comparison to conventional Z-source inverter. The most significant advantage of the T-inverter is its use of a common voltage source of the passive arrangement. This solves many problems involving electromagnetic compatibility which are present in the Z-source inverter. Experimental results for the T-inverter are in agreement with theoretical and simulated predictions.

Mini hydropower and wind power plants have a promising future in Poland. Variable speed cascaded induction generators could be an attractive alternative to conventional double output induction generators habitually applied in mini hydropower stations. Cascaded induction generators require lower maintenance due the absence of slip rings and brushes. Unidirectional power converters can be employed in such power plants to provide simple power electronics, reduce of the maintenance and increase availability. Different topologies of rectifiers with a function of power factor correction could carry the slip power from the secondary side of the cascaded generator during the supersynchronous operation. The main benefit of these clean power rectifiers in comparison with diode rectifiers is the ability of canceling the torque harmonics of cascaded generator. The paper discuss which topology of clean power rectifiers could be applied as machine side rectifier in mini and micro power plants utilizing cascaded induction generator connected to grid.

In the near future brushless induction machines could become the real alternative for the brush-geared doubly fed induction generators in windmills applications. Cascaded doubly fed induction generator (CDFIG) examined in the paper consists of two identical wound rotor induction machines having their rotors mechanically and electrically coupled. In CDFIG both stators of connected machines are accessible. While stator of the first machine is directly connected to the grid, the stator currents and voltages of the second machine can be manipulated for power generation requirements. The paper presents an equivalent circuit of CDFIG at steady state as well the mathematical model of the twin stator cascaded machine. The PSIM simulation software is used for a preliminary investigations of CDFIG.

Alternating voltage inverters (converters) supplied by low-voltage sources DC (ex. fuel cell, photovoltaic cell) are most frequently realized on the basis of the three fundamental topologies: a) PWM voltage inverter with non-transformer converter DC/DC in the "boost-converter" system, b) PWM voltage inverter with transformed converter DC/DC in the "boost-converter" system, c) PWM current converter. However none of these solutions is claimed to be the best and dominant over the others. Search for new and better solutions continues and among them one finds inverters with input symmetrical passive four-terminal networks, which features are very interesting. The paper describes work principles, attributes and potential of the buck-boost inverters system with symmetrical passive four-terminal networks. The paper focuses on the basic Z-source system and suggested new system of a inverter, which was elaborated by authors. Simplified theoretical analysis of both systems has been verified by simulation research. In the last section of the article, the possibility to build multilevel inverters based on diode clamped typology with new four-terminal networks is presented.

In present paper feedback linearization approach for induction motor control in flux - weakening region is proposed. Steady state equations of rotor flux feedback linearization control (FLC) are used for selecting optimal air gap flux level permitting maximum torque operation in field - weakening region. By adjusting the base speed for the constant power operation according to the air gap flux level, the current limit and the voltage limit can be achieved. Preliminary simulation results are presented.

A two-stage speed control algorithm for sensor- less induction motor drives is proposed to obtain high per- formance, as well as high efficiency under nonlinear control. Dependencies for limiting the inverter output voltage and currents based on a multiscalar model of the induction motor are presented. Full decoupling of speed and flux control is the main benefit of the multiscalar model based control system. A passive filter for minimizing additional losses is used.

The control of a servomechanism problem, which is an extension of the results of Kaczorek (1976) and Porter and Bradshaw (1974) is considered. Also, the problem of tracking quality is presented.