The efficiency of interior permanent magnet synchronous motors (IPMSM) can be directly influenced by Variable Frequency Drives (VFDs) implementing M̲aximum T̲orque P̲er A̲mpere (MTPA) algorithms. Model based optimization requires advanced knowledge of machine including non-linear properties which are quite pronounced in IPMSMs. This paper presents a novel online MTPA trajectory seeking scheme which is based on calculating the minimum current possible for every load operating point by dynamically adjusting the current angle during steady state operation. First, an offline MTPA trajectory is derived for the motor using simple datasheet parameters to get a baseline. Second, an online MTPA based on discrete extremum seeking state logic implemented using a model-based design approach is used to seek the least current for a given operating point. Key considerations have been made for efficient execution while minimizing computational resource requirements Experimental results obtained on a 3 HP IPMSM motor demonstrate the effectiveness of the proposed scheme in achieving the MTPA control objective while maintaining control stability across all operating regions.

This paper presents the design and implementation of a three-phase inverter that produces a symmetric ac output voltage of desired magnitude and frequency. Although the inverter has traditionally been designed as analog circuitry, now the digital inverters are preferred. These devices use low-cost microcontrollers and digital signal processors and offer sophisticated control algorithms with highly flexible software, the ability to add user interface, reduce and introduce testing procedures with increase reliability. The PIC18FXX2 of Microchip is used for the of inverter.

Wind energy systems based on doubly fed induction generators (DFIGs) have been dominantly used in high-power applications since they use power-electronic converters with ratings less than the rating of the wind turbine generators. The DFIG is very sensitive to unbalanced grid voltage as its stator is directly connected to the grid. The rotor and stator currents could be highly unbalanced even under a very small unbalanced grid voltage. So there is much more importance of designing and modelling of controllers for eliminating the fault and sustaining fault ride through condition. Modelling of controllers is different for steady state condition and transient conditions with fault ride through conditions. This paper presents an overview of trends and advancements in control strategies of DFIG based wind turbine system in transient conditions.

A systematic method of designing a zero terminal current ripple integrated magnetic Ćuk converter for photovoltaic (PV)-to-battery applications is presented in this paper. The four-winding-coupled inductor design consists of two inductors and a two-winding transformer coupled on a common EE-core. The core design uses a simplified flux-reluctance model to arrive at the area product formulation for this kind of a four-winding structure. The zero-ripple condition in the terminal currents is achieved by controlling the coupling coefficients by means of air-gap reluctances in the core. Unlike the earlier designs for this converter, it provides a completely analytical approach to design this converter for a range of duty ratio. The validity of the proposed method is confirmed using finite element analyses (both two dimensional and three dimensional), thermal validation, and circuit simulations in PSpice. The zero-ripple condition is verified experimentally.

Power transformers are an integral part of an isolated DC DC converter with a high voltage ratio. An essential requirement of such a transformer design is to achieve a low leakage inductance for power transfer. This paper proposes a transformer design using foil conductors with a half-turn high-current (HC) winding which has the following benefits: 1) less number of turns in both of the HC and low-current (LC) windings in comparison to a conventional design; 2) easy termination of the LC winding; 3) low leakage inductance by virtue of less number of turns and ease of interleaving of the LC and HC windings. The incorporation of half-turn HC windings provides openings through which the LC winding turns can pass. This allows the LC winding turns to be wrapped continuously, resulting in easy interleaving and termination. Analytical design followed by 3-D FEA results and bench top measurements on a hardware prototype are provided for a half-turn-winding transformer designed for a 12-288 V, 3 kW, 50 kHz DC-DC converter.

A high frequency ac link, transformer isolated three phase inverter capable of bidirectional power flow is presented in this paper. Such an inverter finds widespread use in applications like interfacing alternate energy sources to the grid, UPS systems. A resonant LC circuit is used to achieve natural commutation of leakage energy in the leakage inductance of the transformer. This natural commutation of leakage energy eliminates the need for additional circuitry otherwise needed to commutate the trapped energy. Additionally, the high frequency ac link makes it possible to reduce the size of the transformer resulting in a lower cost and a compact design. The ac link is utilized to achieve zero voltage switching in the output cycloconverter. A 3 phase, 5 kW inverter is simulated in the SIMULINK environment and the results are discussed.

Modular multilevel converters have become widely used in HVDC applications due to easy scalability and near sinusoidal output voltage synthesis. It is made up of an array of submodules comprising of semiconductor switches and floating capacitors. An important challenge in these multilevel topologies is voltage balancing of the floating capacitors. A voltage balancing technique has been proposed for a modular converter with 3-level submodules. This new converter submodule topology results in added benefits over conventional existing half-bridge submodule topologies. An intelligent commutation technique is proposed which results in 2/3rd of the switching transitions to be soft switched. The proposed control is validated by simulations in MATLAB/Simulink.

LCL filter is becoming an attractive choice over conventional L filters for grid-connected voltage source inverters (VSI) due to smaller inductor size and better attenuation of the ripple components in the grid current. The modulation of the VSI generates switched voltages which results in distorted currents. In this paper, a simple closed form analytical expression is derived for the higher order switching components present in the inverter voltage. This is used in a systematic design procedure to design the LCL filter components for allowable grid current harmonics. A passive damping resistor is designed ensuring minimum power loss. The design is validated by simulations in MATLAB/Simulink and experiments on a laboratory prototype.

High frequency transformers are widely used in Switched-mode power supplies and now are being proposed to be used with power electronic converters to replace line-frequency transformers. This paper presents a winding design procedure for minimizing the power losses using foils and solid round wires under sinusoidal excitation to limit the temperature rise. This paper derives the range from which the thickness of the layers can be chosen to obtain the minimum power loss. This thickness range is a function of the number of layers and does not include the “optimum” based on the previous literature. Using this design procedure, it is shown that interleaving is not necessary in foil-wound transformers to obtain the minimum loss. A comparison of winding losses between foil windings and round conductors is also given. The analytical results are verified by designing six different winding configurations for the same specifications using 2-D Ansys Maxwell finite element design package.

Flywheel energy storage technology has been successfully commercialized for applications requiring high power, high cycle-life, and short storage intervals. High idling losses have prevented the use of flywheel technology in applications that require longer storage intervals, such as grid-based, load-following energy storage. This paper proposes the use of an outer-rotor ac homopolar motor to significantly decrease idling losses, increase energy density, and decrease cost. Motor sizing equations, a comparison to the typically-used permanent magnet motor, and 3D finite element analysis of an example design are presented. It is shown that for high-performance flywheel designs, the ac homopolar motor can have a torque density comparable to that of a permanent magnet motor.

An indirect capacitor clamped multi-level matrix converter has been proposed in this paper. In comparison to the conventional matrix converter the proposed converter makes available half line voltages in addition to the line voltages at the converter output. This increased level comes at the cost of additional bi-directional switches and clamp capacitor. Indirect space vector modulation scheme, for synthesizing the required input current and the output voltage while balancing the clamp capacitor voltage, is presented. This converter offers reduced THD and lower switching stress compared to conventional matrix converter. The effectiveness of the proposed converter has been verified by means of simulation.

The bearingless ac homopolar motor has numerous advantages over classical machines for applications such as flywheel energy storage and as a superconducting machine. In this paper, the bearingless ac homopolar motor is analyzed. Inductance matrices, alignment and reluctance torque calculations, suspension winding configurations, and radial suspension force calculations are presented for two rotor structures. Unlike previous literature, expressions for torque interference caused by suspension force winding configurations and effects of d-axis flux on suspension forces are developed and presented. Furthermore, it is demonstrated that each rotor structure can be analyzed as an equivalent classical machine to allow for easy comparison.

This paper explores various options for increasing power transfer in the electric grid, such as compact transmission lines, high phase order (6 phase) system and use of high temperature low sag (HTLS) conductors. These methods were selected as they could be readily employed without the need for additional right-of-way. Changes in the electric and magnetic field, fault current due to the new methods employed have been calculated and compared with a traditional 3 phase single and double circuit lines. It has been shown that the increase in power transfer ranges from 17-53% when compared with traditional line configurations.

High frequency ac link three phase ac to three phase adjustable speed and magnitude PWM ac converters with single stage power conversion and bidirectional power flow are important in the generation of power from renewable energy sources or where isolation is necessary. Due to the use of high frequency these type of converters achieve high power density. Open loop power factor correction, higher efficiency and reliability are important features of these type of converters. One major problem in this type of converter is the commutation of leakage energy which results in power loss, reduction in switching frequency, distortion and loss of output voltage. The topology based on the indirect modulation of matrix converters uses minimum amount of copper and has relatively less number of semiconductor switches. This paper presents a lossless source based commutation strategy along with a modulation technique that minimizes the frequency of leakage inductance commutation. It also results in the soft switching of the output converter (Zero current switching : ZCS). The topology along with the proposed control has been analysed and simulated. Simulation results confirm the operation.

The introduction of Plug-in Hybrid Electric Vehicles (PHEV) and Electric Vehicles (EV) into the consumer market provides opportunities and challenges to implement Vehicle-2-Grid (V2G). V2G is a vehicle that can connect to the grid and consume power to charge its battery pack or supply power to the grid. This paper presents research on a novel converter that implements bidirectional power flow between the grid and a vehicles battery pack. The main advantages of this converter are the following: i) soft switching for all switches of the input converter independent of the load, Zero Current Switching (ZCS) ii) The switching of the input converter is simplified i.e four-step commutation is not required for the four quadrant switches of the input side converter iii) The average power flow through the converter is a linear function of the control variable so the control is simple iv) open loop input power factor correction, v) high power density, vi) isolation. The entire topology has been simulated with the proposed modulation method and simulation results confirm the analytical predictions.

This paper proposes a novel strategy of control of the active power flow from the power system grid to a micro grid by a power electronic transformer (PET), consisting of controllable loads and distributed energy resources (DER), both renewable and non-renewable. A 60 Hz, step down transformer is generally used at the Point of common coupling (PCC) of a micro grid to connect to the power system grid. A power electronic transformer at the PCC 1) Restricts the active power flow at a desired value determined by the utilities. 2) Allows the micro grid to utilize the change in its local grid frequency, due to a restricted macro grid power, to dynamically control the active power generation or consumption within the micro grid. 3) Ensures decentralized control of the DERs as well as the controllable loads that operate synchronously to supply to the demand within the micro grid. 4) Provides smooth transition from islanding to grid-dependent mode without the need of grid synchronization. To investigate the dynamic power control a simplified representation of the smart micro grid as interconnected power systems is considered and simulated in MATLAB/Simulink. The results obtained demonstrate the dependence of dynamic control of the micro grid's DERs on the change in its grid frequency.

This paper proposes a matrix converter fed, sinusoidal input output high frequency transformer. A single phase three winding transformer is used in the proposed topology. The primary side of the transformer is connected to a low pass filter, and a three phase to single phase matrix converter. The two secondary windings of the transformer are connected to two low pass filters, and a three phase to three phase matrix converter. Because of the low pass filters, the transformer sees high frequency sinusoidal voltages and currents. A novel pulse density modulation scheme is proposed for matrix converters. The modulation scheme is used in the matrix converter connected to secondary of the transformer. Zero common mode voltage is achieved with the proposed power electronic transformer. The switching frequency of power electronic transformer, proposed in this paper, is independent of the value of leakage inductance. A mathematical model is developed to design the two low pass filters. The proposed power electronic transformer has been simulated in MATLAB/SIMULINK and results have been presented.

This paper proposes a novel dc/ac converter topology with a high frequency ac-link for three-phase adjustable speed PWM ac drives. Such drives find applications in UPS systems and renewable energy sources like solar and fuel cells. This topology provides single-stage power conversion with bidirectional power flow capability. The high frequency transformer offers the benefits of galvanic isolation and high power density. The topology proposed in this paper minimizes the number of switching transitions between the transformer winding and the load. This reduces common-mode voltage switching and improves the output voltage profile. A lossless source based commutation technique has been developed for the commutation of the energy stored in the leakage inductances of the high frequency transformer. This method also results in zero current switching (ZCS) of all four-quadrant switches in the load side converter. The proposed topology has been analyzed and simulated. Simulation results that verify the operation of the proposed topology are presented.

High frequency linked ac/ac converters are important in harnessing energy from renewable energy sources and connecting them to the high voltage ac grid. Theoretically, these converters provide single stage power conversion and obviates the need for any storage elements. Any switching transition in the load side converter causes overvoltages due to the presence of non-ideal leakage inductances in the windings of the high frequency transformer. A clamp circuit is needed for commutation of this leakage energy and to protect the power electronic devices. This paper provides a detailed analysis of the power loss incurred in the clamp circuit along with a method to design the clamp components. The entire circuit has been simulated along with non-ideal leakage inductance and the presented simulation results confirm the analytical predictions.

This paper proposes a source based commutation method for a matrix converter fed power electronic transformer. Two converters produce high frequency voltage across a transformer, with open ended primary. A third matrix converter converts the high frequency chopped voltage to line frequency. The leakage inductance of the transformer creates a commutation delay in the primary side to secondary side voltage transfer. During the commutation interval, difference in the load current and secondary leakage current flows to the clamp circuit. Thus, power is lost in the clamp circuit during every commutation interval. The source based commutation described in this paper minimizes the power loss during commutation interval. No additional switching is needed at the primary side power converters for source based commutation. The proposed method has been simulated in SIMULINK and the results have been presented.