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This paper presents a novel hybrid direct power converter (HDPC) which overcomes the two main disadvantages of matrix converters: limited voltage transfer ratio and low immunity to grid disturbance. The proposed converter is formed by integrating a reversible auxiliary boost converter in the dc link of the two-stage matrix converter. Therefore, the HDPC can provide unity voltage transfer ratio even in the case where the supply voltage is highly unbalanced. The proposed converter also preserves most of the inherent advantages of the conventional matrix converter such as: controllable input power factor, sinusoidal supply currents, and bidirectional power flow. A novel predictive current control technique for the HDPC is also proposed for minimum energy storage in the converter. Important aspects of design, control, and implementation of the new HDPC are presented including theoretical analysis and simulations. Experimental waveforms at unity voltage transfer using a laboratory prototype are presented to confirm the viability of the proposed idea. Index Terms--AC-AC converters, matrix converters, predictive current control, unbalanced voltage, voltage transfer ratio.

A new two-stage multi-drive direct power conversion (DPC) topology suited for multi-drive application is proposed, having an input port for a three-phase power supply and several output ports to connect three-phase loads, which are independently controlled and allow for sine wave in-sine wave out operation. This is a cost effective topology compared to a standard matrix converter because the multiple three-phase loads share the cost of the controlled rectification stage. A new method to reduce the high frequency ripple from the input current is also proposed based on interleaving the switching patterns of the inversion stages, which have to form two groups, allowing for size reduction of the input current filter. This is validated by experiments on a realistic laboratory prototype, while its limitations are determined by simulations. Index Terms--Direct power conversion (DPC), high frequency ripple, input current filter, standard matrix converter, three-phase loads.

The new trend in adjustable speed drives (ASD) is to integrate the inverter and the motor into a single unit in order to reduce the production cost, the commissioning time, and the physical size of the equipment. This last issue becomes more important, making the matrix converter topology more attractive. Sinusoidal input currents and bidirectional power flow are other advantages of the matrix converter but it is less immune to power grid disturbances compared to a standard ASD. In hoisting applications, short-term braking capability during a power outage is needed until the mechanical brake engages or to perform more effective a combined braking. This paper proposes a new method to provide short-term braking capability during a power outage for matrix converters. A braking chopper is needed in the clamp circuit, which allows for a drastically reduction of the capacitor size. The power flow in the clamp circuit may be reduced by increasing the harmonic content in the motor currents, which causes higher motor losses. Experiments prove the validity of the proposed method. Index Terms--ASD, braking method, clamp circuit, induction motor, matrix converter, power interruption.

The trend in electrical drives is to integrate the frequency converter, the electrical motor, and even the gear or the pump into a single unit, in order to reduce the costs, to increase the overall efficiency and the equipment reliability. This paper presents the first integrated regenerative frequency converter motor for industry applications, based on a matrix converter topology. The low volume, the sinusoidal input current, the bidirectional power flow, and the lack of the bulky and limited-lifetime electrolytic capacitors recommend this topology for this application. This paper shows how the matrix converter disadvantages--the lack of bidirectional power devices, the lower voltage transfer ratio, and the overvoltages caused by the input filter during power-up--that have delayed the industrial implementation have been overcome. In order to demonstrate the validity of the solution, a 4-kW matrix converter motor prototype is built using a standard frequency converter motor enclosure for testing the requirements for an industrial drive. The tests demonstrate the good performance of the drive. Index Terms--AC-AC power conversion, bidirectional switch, integrated motor drive, power electronic building block, space-vector modulation.

This paper analyzes some aspects of integrating the matrix converter (MC) bidirectional switches into a power module. The analysis produces two optimal topologies for a power module: one for low-power and another for medium/high-power MCs. A new power module topology for a low-power three-phase-to-three-phase MC is proposed. By using bootstrap circuits to feed the gate-drivers, the proposed configuration requires only three insulated power supplies for a complete MC. This proposal constitutes a solution recommended in the low-power range, where low cost and low volume are the main objectives. Furthermore, a configuration of a power electronic building block for MCs is proposed. This includes the commutation control logic and the overcurrent protection, provides safe operation, and eliminates the specific problem of operating the bidirectional switches. Index Terms--AC-AC power conversion, bidirectional switch, bootstrap circuit, packaging, power electronic building block, power integrated circuits.

The matrix converters, which are direct power electronic converters, are able to provide important benefits such as bidirectional power flow, sinusoidal input currents with adjustable displacement angle, and a great potential for size reduction. Still, two major disadvantages exist: a lower than unity voltage transfer ratio and high sensitivity to power grid disturbances. Many solutions to provide continuous operation of adjustable speed drives (ASDs) during power grid disturbances have been proposed, but they are all applied to dc-link ASD. In this paper, a new solution to provide limited ride-through operation is presented with a matrix converter using a scalar controlled induction motor for a duration of hundreds of milliseconds, without any hardware modification. During the ride-through operation, the drive is not able to develop torque or to control the motor flux. By recovering the necessary power to feed the control hardware of the matrix converter, it is able to keep the ASD operating. When normal grid conditions are reestablished, the matrix converter is able to accelerate the motor from nonzero speed and flux by initializing the modulator with the estimated frequency and the initial angle of the reference output voltage vector. The maximum duration of the ride-through operation depends on the initial motor flux, speed level, rotor time constant, load torque, and inertia. This method is verified on a laboratory setup with a matrix converter. Index Terms--AC-AC power conversion, flying start, ride-through operation, variable-speed drives.

In this paper, the input current performance of matrix converters is analyzed, especially with reference to the operating conditions determined by unbalanced supply voltages. The space-vector modulation (SVM) technique is utilized to calculate the duty cycles of the active voltage vectors that must be applied, in each switching cycle period, in order to satisfy the input and output requirements. A detailed theoretical analysis of the input current harmonic content under unbalanced input voltage conditions is presented for two different current modulation strategies. On the basis of numerical simulations as well as measurements on a laboratory prototype setup, the strategies' performance are compared and the validity of the theoretical investigation confirmed. It is concluded that, when the input voltages are unbalanced to a significant extent, a dynamic input current modulation strategy has to be preferred, since a lower harmonic line current distortion will appear. Index Terms--Harmonic analysis, harmonic distortion, matrix converters, modulation strategies, power conversion harmonics, power system harmonics, power quality.

In the last years many solutions to provide continuous operation of adjustable speed drives (ASDs) during power grid disturbances are proposed, but they are all applied to dc-link ASD. In this paper a new solution to provide limited ride-through operation of a scalar controlled direct frequency converter (DFC) for a duration of hundreds milliseconds, without any hardware modification, is presented. During the ride-through operation, the drive is not capable to develop torque or to control the motor flux. By recovering the necessary power to feed the control hardware, the DFC is able to keep the ASD operating. When normal grid conditions are re-established, the DFC is also able to accelerate the motor from nonzero speed and flux by initializing the modulator with the estimated frequency and initial voltage vector angle. The duration of the ride-through operation depends on the initial motor flux, speed level, rotor time constant, load torque and inertia. Index Terms--AC-AC conversion, adjustable speed drives, direct frequency converter, flying start, power interruptions, ride-through operation, voltage source converter.