Maurice Apap

Gate drive level intelligence and current sensing for matrix converter current commutation

This paper is concerned with the process of current commutation in matrix converters. The mechanisms involved in the commutation process are described and practical waveforms are presented. A novel commutation strategy is described that uses gate drive level intelligence in the form of a field-programmable gate array. Current direction is determined using device voltages and, therefore, the measurement problems associated with all other commutation methods are overcome. Practical results from an 18-kW matrix converter induction motor drive are presented.

Reactive Power Sharing and Voltage Harmonic Distortion Compensation of Droop Controlled Single Phase Islanded Microgrids

When paralleling multiple inverters that are capable of operating as an island, the inverters typically employ the droop control scheme. Traditional droop control enables the decentralized regulation of the local voltage and frequency of the microgrid by the inverters. The droop method also enables the inverters to share the real and reactive power required by the loads. This paper focuses on some of the limitations of parallel islanded single phase inverters using droop control. Algorithms with the aim to address the following limitations in islanded operation were proposed: reactive power sharing and reduction of the voltage harmonic distortion at the point of common coupling (PCC). Experimental results were then presented to show the suitability of the proposed algorithms in achieving reactive power sharing and in improving the voltage harmonic distortion at the PCC.

Elimination of Waveform Distortions in Matrix Converters Using a New Dual Compensation Method

Matrix converters are becoming a real alternative to traditional topologies for many ac-ac power conversion applications. One of the less well-known advantages is the potential for reduced waveform distortion that arise from device characteristics and commutation delays. This paper describes the origin of distortion effects for a matrix converter with current sign-based commutation and gives a novel approach to the method that can, in principle, eliminate the distorting effects to give a power converter having excellent linear behavior. The effectiveness of compensation techniques are illustrated for both an open-loop matrix converter driving a passive load and a matrix converter as part of a vector-controlled drive.

Harmonic Loss Due to Operation of Induction Machines From Matrix Converters

This paper quantifies the extra harmonic losses in an induction motor that are associated with the use of a matrix converter topology as a motor drive. These extra losses are compared to the harmonic losses associated with an inverter-based motor drive. The technique employed in the determination of the harmonic losses is described. For the matrix converter, the extra harmonic losses associated with two commonly used modulation techniques are calculated and compared. The impact of these extra losses on the cooling requirements and operation of the motor is considered.

Analysis and comparison of AC-AC matrix converter control strategies

It is desirable that a matrix converter control strategy maintains both device power loss and distortion at the converter inputs and outputs at a minimum. A number of control methods are investigated according to these criteria and results showing their relative performance are presented. The effects of practical switching constraints are also discussed.

Single-Phase Microgrid With Seamless Transition Capabilities Between Modes of Operation

Microgrids are an effective way to increase the penetration of distributed generation into the grid. They are capable of operating either in grid-connected or in islanded mode, thereby increasing the supply reliability for the end user. This paper focuses on achieving seamless transitions from islanded to grid-connected and vice versa for a single phase microgrid made up from voltage controlled voltage source inverters (VC-VSIs) and current controlled voltage source inverters (CC-VSIs) working together in both modes of operation. The primary control structures for the VC-VSIs and CC-VSIs is considered together with the secondary control loops that are used to synchronize the microgrid as a single unit to the grid. Simulation results are given that show the seamless transitions between the two modes without any disconnection times for the CC-VSIs and VC-VSIs connected to the microgrid.

Secondary control for reactive power sharing in droop-controlled islanded microgrids

This paper focuses on the islanded operation of microgrids. In this mode of operation, the microsources are required to cooperate autonomously to regulate the local grid voltage and frequency. Droop control is typically used to achieve this autonomous voltage and frequency regulation. However, droop control has real and reactive power sharing limitations when there are mismatches between the microsources. This paper analyses the effect due to mismatches in the power line impedances connecting the source inverters to the microgrid. From the simulations results obtained, it was shown that the reactive power demand is unequally shared between the microsource inverters when there are mismatches between the power line impedances. To achieve equal reactive power sharing between the inverters, an external loop requiring low bandwidth communications was implemented in a central controller. Simulation results are presented showing the feasibility of the proposed solution in achieving reactive power sharing between the inverters connected to the microgrid.

A fully integrated 30 kW motor drive using matrix converter technology

This paper explores the viability of using direct power converter technology to realize integrated motor drives, at power levels significantly higher than is possible with traditional approaches, fitting within the same space envelope as an equivalent motor. The integrated motor design was targeted at pump and fan applications where the need to install motor drives in a separate location is often an impediment to the replacement of fixed speed motors. In order to achieve this objective the thermal and electrical design of the integrated drive have to be considered together. This paper presents the final design that achieves all these objectives, including fully tested and evaluated demonstrations of the power converter and the cooling arrangements. The final integrated motor drive design only differs from a standard motor in terms of one end plate, the terminal box and the shaft driven fan. Full practical results of the 30 kW demonstrator are presented in the paper

An Integrated 30kW Matrix Converter based Induction Motor Drive

This paper explores the viability of using direct power converter technology to realize integrated motor drives, at power levels significantly higher than is possible with traditional approaches, fitting within the same space envelope as an equivalent motor. The integrated motor design was targeted at pump and fan applications where the need to install motor drives in a separate location is often an impediment to the replacement of fixed speed motors. In order to achieve this objective the thermal and electrical design of the integrated drive have to be considered together. This paper presents the final design that achieves all these objectives, including fully tested and evaluated demonstrations of the power converter and the cooling arrangements. The final integrated motor drive design only differs from a standard motor in terms of one end plate, the terminal box and the shaft driven fan. Full practical results of the 30 kW demonstrator are presented in the paper

Secondary control for reactive power sharing and voltage amplitude restoration in droop-controlled islanded microgrids

This paper focuses on the islanded operation of microgrids. In this mode of operation, the microsources are required to cooperate autonomously to regulate the local grid voltage and frequency. Droop control is typically used to achieve this autonomous voltage and frequency regulation. However, droop control has real and reactive power sharing limitations between the microsource inverters when there are mismatches between the output filter components and power line impedances. In this paper, secondary control loops were implemented to achieve equal reactive power sharing between the inverters and to restore the voltage deviations caused by the droop control. Primary droop control loops where implemented in the inverters to supply the real and reactive power. Simulation results are presented showing the feasibility of the proposed algorithm in achieving reactive power sharing between the inverters connected to the microgrid while simultaneously restoring the voltage deviations due to the droop control.