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This paper presents a proposal for a Hybrid Cycloconverter with Three-phase Input and Single-phase Output with Low Output Voltage Harmonic Distortion (THDV). The proposed topology is based on the series association of Thyristor-based Cycloconverter with a non-isolated two DC-DC converters. The DC-DC converters are designed to process the minimum amount of energy necessary to mitigate harmonic distortion of the output voltage and, hence, to increase power density and efficiency. Theoretical analysis is presented and corroborated by experimental results obtained with a small-scale laboratory prototype. Different operating modes are analyzed and confirm the functionality of the proposed converter.

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Introduction. The power extracted from the wind turbine and delivered to the electrical network must be maximum and constant and the whole system should be have a good compromise between efficiency and cost. In order to attenuate this objective, a doubly fed induction machine, a cycloconverter, a maximum power point tracking algorithm and a flywheel energy storage system constitute a very interesting solution among many others that have been proposed. Novelty. The novelty of the proposed work is to use a doubly fed induction machine and a three pulses cycloconverter to reduce the cost and to integrate a flywheel energy storage system between the wind generator and the electrical network to maintain the constancy of the power sent to the network, following the instability of the wind. The proposed work uses a maximum power point tracking algorithm to capture the optimal power available in the wind in order to increase the efficiency of the system. Results. A detailed study of the proposed system is presented with the detailed dynamic modeling equations and simulation results are conducted to show the performance and the efficiency of the suggested work.

Single-phase direct frequency converters are gaining attraction at the research and academic level as they are rapidly getting space over conventional multistage converters. The converters developed with a rectification and inversion process using a DC-link level are examples of multistage converters with some serious concerns such as an increase in the overall weight, losses, and cost. They also suffer from the low-reliability issue due to the issues involved with DC-link capacitors and problems linked with electromagnetic interference (EMI) caused by high-frequency pulse width modulation (PWM) switching. These problems are addressed with line frequency switching cycloconverters. In these converters, the power quality of the output voltage is improved by governing the amplitude of some selected output pulses or half-cycles. For this purpose, a low-frequency multiple tapping transformer may be used to obtain various voltage levels. However, its use is the main source of increased overall weight, losses, cost, and volume. In transformer eliminated topologies, high-frequency PWM control can be employed to control the magnitude of some selected half cycles of the output voltage. However, this approach may arise some problems related to EMI. In both control techniques, the attention is focused on the power quality of the output voltage only. The concern for the input current is ignored and not yet analyzed. This is one of the critical power quality concerns and requires further investigation. The magnitude control of the output half-cycles causes the variation in the amplitude of some half cycles of the input currents. As a result, all half cycles of the input current become non-symmetric. It generates harmonics that are always of low frequency and cannot be easily filtered out. It results in a high value of the harmonic factor (HF) of the input current. The improvement in the power quality of the output voltages severally degrades the power quality of the input currents. In this research, this problem is investigated with mathematically computed harmonic coefficients with a pulse selective approach. Also, a simple single-phase cycloconverter is introduced to improve the power quality index of the input current. The overall analysis is supported by the results obtained from a Simulink-based environment and a practically constructed prototype. [ABSTRACT FROM AUTHOR]

Copyright of Electrical Engineering & Electromechanics is the property of National Technical University, Kharkiv Polytechnic Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper proposes a new modular multilevel AC/AC converter using high-frequency (HF) transformer, which has the advantages of modular design, easy expansion, high power density, no circulation current, good output voltage waveform quality and low cost. This converter has broad application prospects in the fields of high-voltage and high-power wind power generation, fractional frequency power transmission (FFTS) and power electronic transformer. The proposed converter topology can connect two three-phase AC systems with different frequencies and amplitudes directly. By introducing HF transformer, the direct series connection of input and output modules can be realized simultaneously, and the expensive industrial frequency transformer with large volume and weight can be removed. In order to achieve HF electrical isolation, the HF inversion of the output pulse is carried out at the inverter side to realize the HF output of the fundamental wave. After passing the HF transformer, the pulse is restored to the low-frequency output wave by the cycloconverter. Aiming at the problem of freewheeling of HF link, the method of common state conduction is introduced, which can effectively reduce the switching loss. The modulation scheme, control strategy and typical parameter design are developed. Furthermore, the feasibility of the proposed converter is verified by simulation results.

This paper presents a novel single-phase to single-phase multiconverter topology that can be applied in multiple areas. The proposed multiconverter is designed with only two soft power semiconductor switches (e.g. MOSFET or IGBT), four power diodes and a center-tapped transformer which makes it more compact in size, decrease the gate driving complexity, reduce the total equipment costs and enhance the energy conversion efficiency with minimized losses. Furthermore, the utilization of the transformer in the proposed converter mitigates the multiple AC source requirement problems and provides galvanic isolation which increases the reliability of the converter. Moreover, the presented multiconverter is applicable in various areas including electric traction as a speed controller, induction heating, AC and DC variable power supplies, etc. which signify the competence of this converter in energy conversion appliances. However, a comparative analysis of the offered converter with the existing AC-AC converters is also introduced in this paper with respect to the number of components, equipment costs, gate driving complexity, and application areas. In order to evaluate the performance of the proposed multiconverter, the simulation-based results carried out in MATLAB/Simulink are presented and analyzed in this paper with proper descriptions. Finally, a scaled-down prototype is developed in the laboratory to validate the simulation results and the feasibility of the proposed multiconverter.

In variable speed applications, the cycloconverter-based AC to AC power conversion technique has gained more attention among researchers and academics than the traditional rectifier-inverter-based AC to AC power conversion process. The conventional rectifier-inverter-based AC to AC power conversion process has several disadvantages. It uses multi-power stages that increase the converter power conversion losses and increase the cost, volume, and weight of power losses. Besides high conduction and switching losses, the electromagnetic interference problems also accompany the above issues. In this regard, this paper proposes a novel step-down Triac based cycloconverter for variable speed control applications. The proposed topology uses only five Triac devices for one-third and one-fourth frequency conversion of 50 Hz with reduced total harmonics distortion without using any pulse width modulation techniques. The proposed model is designed in the MATLAB/SIMULINK environment. The simulation results show that around 18.85% and 23.67% of total harmonics distortions are reduced in the proposed converter for one-third and one-fourth frequency conversion of 50 Hz, respectively. Two physical experiments are carried out to prove the validity of the simulation results. [ABSTRACT FROM AUTHOR]

Harmonic distortions caused by non-linear loads (NLLs) affect the behavior of electrical systems, creating harmonics in the fundamental signal. As a result, this deteriorates the power quality. Therefore, this work proposes the implementation of a hybrid filter based on an artificial neural network (ANN) control system, focused on subharmonic, interharmonic and odd harmonic distortions generated by a three-pulse cycloconverter. In addition, a passive double tuned filter was implemented to damp even and odd harmonics. As a result, the simulation performed in MATLAB/SIMULINK showed that the responses produced by the ANN are approximate to the distortions present in the electrical system. Consequently, the levels of total voltage distortions (THDV) and total current distortions (THDI) are reduced. Therefore, the ANN control system improves the quality in the electrical network because the current and voltage harmonics comply with the electrical standards. [ABSTRACT FROM AUTHOR]

The existence of the double grid frequency (100 Hz) ripple current in dc/ac dual active bridge (DAB) power converters can degrade their performance and as such these ripples need to be compensated. An active power decoupling method is proposed in this paper to attenuate the 100-Hz current ripple in single phase dc/ac DAB converters. Compared to other current ripple reduction methods for which additional switches are used, the proposed method does not require any additional switching components thus decreasing the system cost. In the proposed method, the existing switching devices of the primary side full bridge converter and an LLC circuit integrated to form a 100-Hz ripple current reduction circuit, which is controlled by regulating the duty cycle of the primary full bridge converter switching legs. The mathematical analysis and the circuit parameter design methods are proposed. In addition, a current sharing method is proposed to keep the currents of the inductors in the LLC circuit are balanced against any possible circuit parameter deviations. The effectiveness of the developed method is evaluated through the simulation and experimental tests.

Single-phase direct frequency converters are gaining attraction at the research and academic level as they are rapidly getting space over conventional multistage converters. The converters developed with a rectification and inversion process using a DC-link level are examples of multistage converters with some serious concerns such as an increase in the overall weight, losses, and cost. They also suffer from the low-reliability issue due to the issues involved with DC-link capacitors and problems linked with electromagnetic interference (EMI) caused by high-frequency pulse width modulation (PWM) switching. These problems are addressed with line frequency switching cycloconverters. In these converters, the power quality of the output voltage is improved by governing the amplitude of some selected output pulses or half-cycles. For this purpose, a low-frequency multiple tapping transformer may be used to obtain various voltage levels. However, its use is the main source of increased overall weight, losses, cost, and volume. In transformer eliminated topologies, high-frequency PWM control can be employed to control the magnitude of some selected half cycles of the output voltage. However, this approach may arise some problems related to EMI. In both control techniques, the attention is focused on the power quality of the output voltage only. The concern for the input current is ignored and not yet analyzed. This is one of the critical power quality concerns and requires further investigation. The magnitude control of the output half-cycles causes the variation in the amplitude of some half cycles of the input currents. As a result, all half cycles of the input current become non-symmetric. It generates harmonics that are always of low frequency and cannot be easily filtered out. It results in a high value of the harmonic factor (HF) of the input current. The improvement in the power quality of the output voltages severally degrades the power quality of the input currents. In this research, this problem is investigated with mathematically computed harmonic coefficients with a pulse selective approach. Also, a simple single-phase cycloconverter is introduced to improve the power quality index of the input current. The overall analysis is supported by the results obtained from a Simulink-based environment and a practically constructed prototype.

The paper presents electric Machine-Converter Voltage Source (MCVS) for systems of distributed power supply with shaping output voltage in an electric machine (generator). The MCVS consists of electric machine and a cycloconverter that has three-phase bridge circuit. Both synchronous generator and asynchronous exciter, which are located in one housing, operate as electric modulation generator. Functional diagram of complex MCVS, where the output voltage is stabilized by simultaneous or separate use of several control channels. We analyzed output voltages of MCVS and dependences of non-sinusoidality and distortion factors on ratio rotational speed of generator to output voltage frequency of MCVS for various amplitude modulation indexes and control modes of cycloconverter.

The paper is devoted to development of Machine-Converter Source (MCS), which forms the output voltage waveform of electric generator as sum of EMFs with near frequencies. As electric modulation generator is used a synchronous generator and asynchronous exciter that have both common driving shaft and common housing. We studied the automatic control systems for output electrical parameters of MCS when changing speed of driving shaft and load power in wide ranges.

This work presents the development of an electronic system prototype to assist in the drying of single-phase electrical transformers by injecting sinusoidal low-frequency currents. The main component of the prototype developed here is a cyclo-converter, which is controlled through a field programmable gate array. The prototype includes control and regulation structures for the electrical and thermal variables that are associated with heating of the transformer under drying. A basic design modeled in MATLAB was used to develop the proposed system. Based on the simulation results, the design was adjusted and the control and estimation strategies of the transformer's temperature under heating were evaluated. The operation of the system, including the control of the heating temperature of the transformer under drying, was experimentally assessed by laboratory tests. [ABSTRACT FROM AUTHOR]

In variable speed applications, the cycloconverter-based AC to AC power conversion technique has gained more attention among researchers and academics than the traditional rectifier-inverter-based AC to AC power conversion process. The conventional rectifier-inverter-based AC to AC power conversion process has several disadvantages. It uses multi-power stages that increase the converter power conversion losses and increase the cost, volume, and weight of power losses. Besides high conduction and switching losses, the electromagnetic interference problems also accompany the above issues. In this regard, this paper proposes a novel step-down Triac based cycloconverter for variable speed control applications. The proposed topology uses only five Triac devices for one-third and one-fourth frequency conversion of 50 Hz with reduced total harmonics distortion without using any pulse width modulation techniques. The proposed model is designed in the MATLAB/SIMULINK environment. The simulation results show that around 18.85% and 23.67% of total harmonics distortions are reduced in the proposed converter for one-third and one-fourth frequency conversion of 50 Hz, respectively. Two physical experiments are carried out to prove the validity of the simulation results.

This paper proposes a soft-switched modulation technique with synchronous rectification for an isolated single-stage single-phase matrix-type dc–ac converter. The dc side consists of a full bridge inverter, and the ac side is a 2×2 matrix converter-based cycloconverter. The proposed unipolar modulation strategy provides zero current switching/zero voltage switching (ZVS) for the ac side devices and ZVS-on for the dc side devices. It also allows natural commutation of the current flowing through the secondary side leakage inductor of the isolation transformer and the grid inductor during unity power factor (UPF) condition, thus eliminates the requirement of snubber circuit. An improved soft-switched flyback-based regenerative snubber circuit is also presented for non-UPF operation. Proposed snubber circuit recycles the energy stored in the snubber capacitors in every switching cycle. A guideline to design snubber circuit along with a comparative study is discussed in this paper. Performance of the proposed hybrid modulation technique is evaluated in an SiC mosfet based 1.2-kW dc–ac converter prototype. A detailed analysis of the converter performance has been presented in this paper considering the circuit non-idealities. [ABSTRACT FROM AUTHOR]

High efficiency and low-cost Static Frequency Changer (SFC) converters are widely used in electronic industry. SFC known as cycloconverter is installed to obtain variable output AC voltage or frequency. Fast dynamic response and slight size made these converters to occupy the potential space in switching world. Cycloconverter generates harmonics when connected to different types of loads. These harmonics pollute the purity of sinusoidal waveform and affect the quality of power system. Harmonic current is produced when an electrical device draws current in a nonsinusoidal manner. The harmonic voltage develops as harmonic current traverses the electrical system. Harmonic and current orders are inversely proportional to each other, respectively. These harmonics affect the execution of switching devices and causes breakdown of cable insulation, circuit breaker tripping, power transformer failures, limits on generator efficiency and UPS capacity. This paper comprises of odd harmonics that takes place in different load contiguous with cycloconverter. The 3rd, 5th, 7th and higher order harmonics are diagnosed by employing MATLAB platform. Simulation studies are depicted and proved the importance of single phase step down bridge - cycloconverter. [ABSTRACT FROM AUTHOR]

In this paper, a new topology for Interline Dynamic Voltage Restorer (IDVR) is proposed. This topology contains two direct three-phase converters which have been connected together by a common fictitious dc-link. According to the kind of the disturbances, both of the converters can be employed as a rectifier or inverter. The converters receive the required compensation energy from the gird through the direct link which is provided by the dual-proposed switches. Due to the lack of the huge storage elements, the practical prototype of the proposed topology is more economical in comparison with the traditional structure. Moreover, compensating for long time duration is possible due to the unlimited eternal energy which is provided from the grids. The low volume, cost and weight are the additional features of the proposed topology in comparison with traditional types. This topology is capable to compensate both of the balanced and unbalanced disturbances. Furthermore, restoring the deep sags and power outages will be possible with the support from the other grid. Unlike the conventional topologies, the capability of compensation is independent from the power flow and the power factor of each grid. The performance of the proposed IDVR topology is validated by computer simulation with PSCAD/EMTDC software.

RANCANG BANGUN CYCLOCONVERTER UNTUK SINKRONISASI PEMBANGKIT TENAGA LISTRIK

High-power industrial rolling mills rely heavily on the sustained operation of cycloconverters, a type of variable-frequency drive. This research proposes a methodology, which observes and diagnoses the operation of cycloconverters as either normal or abnormal by use of time–frequency signature analysis. Various features of the cycloconverter's input current in the time–frequency domain are identified and used to derive parameters that describe these two states in a quantitative manner. A reference model using the parameters is then developed, and comparisons in the time–frequency domain to real data are implemented. Based on these comparisons, a statistical decision boundary is delineated that is used to classify the health status of the cycloconverter. [ABSTRACT FROM AUTHOR]

The paper presents electric Machine-Converter Voltage Source (MCVS) for systems of distributed power supply with shaping output voltage in an electric machine (generator). The MCVS consists of electric machine and a cycloconverter that has three-phase bridge circuit. Both synchronous generator and asynchronous exciter, which are located in one housing, operate as electric modulation generator. Functional diagram of complex MCVS, where the output voltage is stabilized by simultaneous or separate use of several control channels. We analyzed output voltages of MCVS and dependences of non-sinusoidality and distortion factors on ratio rotational speed of generator to output voltage frequency of MCVS for various amplitude modulation indexes and control modes of cycloconverter. [ABSTRACT FROM AUTHOR]

This paper discusses the operation of a single-stage, isolated, high-frequency ac-link-based single-phase dc–ac converter, suitable for photovoltaic microinverter applications, controlled using phase modulation of the secondary-side cycloconverter devices. A detailed analysis is presented explaining the impact of prominent circuit nonidealities such as device capacitance and transformer leakage inductance on circuit behavior. The proposed extended-dead-time based modulation scheme helps in achieving zero-voltage-switching of the primary devices over the entire line cycle of the ac output and also offers the benefit of reduced transformer rms current due to absence of circulating current in the zero state. A flyback-based regenerative clamp circuit is used for mitigating voltage spikes on the secondary devices arising due to leakage inductance induced oscillations. A generic commutation strategy is also discussed, which makes operation with nonunity power factor loads also possible. Experimental results on a 260-W laboratory prototype under different load conditions are presented to illustrate the discussed principles and highlight the performance improvements. [ABSTRACT FROM PUBLISHER]

Two carrier-based unipolar-sinusoidal pulse width modulation (SPWM)-oriented modulation techniques for an isolated bidirectional dc–ac converter are proposed, compared, and validated in this paper. The dc–ac converter is composed of a full-bridge (FB) inverter cascaded with a cycloconverter through a high-frequency transformer. Both modulation techniques proposed in this paper can realize zero-voltage switching (ZVS) for the FB inverter and zero-current switching or ZVS for the cycloconverter in all load range, and are able to suppress the voltage spikes introduced by the transformer leakage inductance as well. In order to increase the converter efficiency and power density, we propose to utilize SiC MOSFETs for the converter. The first modulation technique enables the utilization of Si-SiC hybrid switches with no synchronous rectification (SR), for the purpose of lowering the converter cost. The second modulation technique requires all switches to be SiC MOSFETs, but with SR, which increases the converter efficiency. A 400-V dc to 240-V ac 1.2-kW prototype has been developed to validate the effectiveness and performance of the proposed carrier-based unipolar-SPWM-oriented modulation techniques. [ABSTRACT FROM PUBLISHER]

The paper is devoted to development of Machine-Converter Source (MCS), which forms the output voltage waveform of electric generator as sum of EMFs with near frequencies. As electric modulation generator is used a synchronous generator and asynchronous exciter that have both common driving shaft and common housing. We studied the automatic control systems for output electrical parameters of MCS when changing speed of driving shaft and load power in wide ranges. [ABSTRACT FROM AUTHOR]

Mathematical model of double-fed motor was analyzed and relationship between stator current and rotor current of the motor was derived theoretically. Double-variable cycloconverter was used to provide frequency conversion excitation power for double-fed motor, and rotor current was controlled by controlling amplitude and frequency of output voltage of the converter. The impact of rotor current on stator power factor of double-fed motor was studied experimentally, and conclusions was derived that power factor of the motor can be adjusted by controlling rotor current.

In this paper, we propose a wind energy conversion system (WECS) at variable speed using a doubly fed induction generator (DFIG) controlled on the rotor side through a cycloconverter. The dynamic behavior of the WECS, including the models of the wind turbine, the DFIG, the cycloconverter, and the power control of this system, is investigated. The power control of this system is applied to achieve the independent control of the active and reactive powers exchanged between the wind generator and the grid. In addition, a maximum power point tracking (MPPT) control is included in the control system to capture the maximum power from the wind. Moreover, the cycloconverter with DFIG are used to test the possibility to operate in two quadrant modes (sub-synchronous and super-synchronous modes). The description of the proposed system is presented with the detailed dynamic modeling equations. The simulation results are presented, to demonstrate the performance and the efficiency of this system.

Voltage model has been widely used in the field of motor control due to the advantages of the simple structure and less parameters required. A novel motor flux estimator based on phase-locked loop and proportional-integral (PI) regulator is proposed in this paper. This estimator calculates the set point of the torque component of electromotive force (EMF) through synchronous frequency and flux. Then, errors between the set point and the actual value of the EMF torque component are corrected by PI regulator to estimate the flux. This method avoids the problem of the saturation brought by the traditional integrator and the problem of the initial phase error. It also solves the magnitude and phase error problems at low speed in the flux estimator based on the low-pass filter. Finally, the simulation and the experiments are implemented on a cycloconverter-fed motor drive system to verify the effectiveness of this method. Simulation results show that this algorithm works very well at 0.2 Hz, and experimental results show that this algorithm can work well at 0.5 Hz. Meanwhile, this algorithm could detect the initial position of the rotor of separately excited synchronous motor. [ABSTRACT FROM AUTHOR]

A novel carrier-based unipolar-sinusoidal pulse width modulation (SPWM)-oriented modulation technique with synchronous rectification for isolated bidirectional single-stage high-frequency-ac link dc–ac converters using SiC MOSFET is presented in this paper. The dc–ac converter is composed of a full-bridge (FB) inverter cascaded with a cycloconverter through a high-frequency transformer. A carrier-based unipolar-SPWM-oriented modulation technique with synchronous rectification is proposed to realize zero-voltage-switching (ZVS) for the FB inverter and zero-current or zero-voltage-switching (ZVS/ZCS) for the cycloconverter in all load ranges, and to suppress the voltage spikes introduced by the transformer leakage inductance as well. In order to increase the switching frequency, efficiency, and power density, this paper proposes to utilize SiC MOSFETs for the converter. Synchronous rectification is implemented to further increase the converter efficiency. With the novel modulation technique, there are two switches in the cycloconverter that are continuously on at each interval, which eliminates on-fourth of the switching loss. A simulation model and a 400 VDC–240 VAC, 1.2=kW prototype have been developed to validate the effectiveness and performance of the proposed unipolar soft-switching modulation technique and SiC converter. [ABSTRACT FROM AUTHOR]

In this paper, the independent control of the doubly fed induction machine speed and stator reactive power using cycloconverter is designed and investigated. The proposed system is constituted of the doubly fed induction machine with the stator connected directly to the line grid while the rotor is connected and controlled by the cycloconverter. In order to separate the speed and the stator reactive power conrol, the stator-flux oriented control and cosine-wave crossing control techniques are applied. In addition, the whole system is used to operate in the two quadrant modes (sub-synchronous and super-synchronous modes). The detailed dynamic modeling equations of the proposed system are described. Simulation results are presented to demonstrate the performance and the effectiveness of this system. [ABSTRACT FROM AUTHOR]