In this paper, a novel droop method to control the power sharing of parallel uninterruptible-power-supply (UPS) systems is presented. In a clear-cut contrast to the previously reported works, the controller is a proportional-resonant controller which ensures good transient response and steady-state objectives. Furthermore, the need for sensing the output current for the power-sharing control is removed by implementing it in a software routine. This brings a less complicated and less expensive structure in which the number of feedback sensors is reduced from three to two. The droop paralleling strategy is based on the drop in the inverter output frequency and amplitude. The application of proportional-resonant controllers based on internal model principle is also extended to parallel inverters, and its superior performance over the well-known proportional-integral-derivative controller is presented. In order to show the performance of the proposed system, two parallel-connected UPS systems are analyzed, and two types of linear and nonlinear loads are considered. The nonlinear load is compliant with IEC 62040-3 standard for class I UPS. The results show that the reduction of sensors does not result in any error, and the performance of the control system is excellent. To verify the proposed concept, the proposed strategy is implemented within two-625VA UPS systems. Several test results are provided for linear and nonlinear loads which validate the simulations results. The results indicate that the proposed parallel inverter structure offers a better system in terms of the number of feedback sensors, performance, and complication.

In battery/ultracapacitor (UC) electric vehicles (EVs), a bidirectional dc/dc converter is employed to process the power according to the power references obtained from the energy management controller. The selection of this converter is of critical importance for the overall system efficiency and size. This study proposes using a three-level dc/dc converter and provides a comprehensive comparison with the conventional twolevel and interleaved bidirectional buck/boost converters in terms of magnetic component size/weight and overall efficiency. Unlike the comparative studies presented in literature, where the efficiency comparison of converters is conducted based on given fixed input and output parameters, power references obtained from a wavelet-transform based energy management strategy with varying energy source voltages and traction power are considered in this manuscript. The results of the analyses show that three-level converter exhibits higher overall efficiency and has smaller size inductor. A 1-kW bidirectional three-level dc/dc converter is designed as a proof-of-concept, which exhibits 93.2% peak efficiency at 200 kHz switching frequency.

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This paper demonstrates a multi-platform hardware-in-the-loop approach to observe the operation of a high speed permanent magnet synchronous generator coupled with a micro-turbine in an all-electric-ship power system. The mathematical model of the gas-turbine and dynamic equations of the high speed generator are implemented in real-time on an FPGA. This real-time simulation interfaces with hardware via a serial peripheral interface to a supervisory DSP of a 3-phase voltage source inverter. The inverter output load is virtually emulated in the FPGA using received hardware measurements from DSP. A user input interface is introduced using dSPACE on a PC to acquire data and adjust the speed reference of the generator system through a serial communications interface to the DSP. The real-time simulation and hardware-in-the-loop experimental setup are validated in a scaled-medium-voltage-DC ship power system. Index Terms-Real-time emulation, gas-turbine (GT), high speed permanent magnet synchronous generator (PMSG), multi-platform hardware-in-the-loop (HIL), simulation, voltage source inverter (VSI), FPGA, DSP, dSPACE, all-electric-ship (AES). NOMENCLATURE , , PMSG phases electromotive forces (EMF), V. Stator resistance, Ω. Stator leakage inductance, H. Applied positive torque, N.m. Applied mechanical torque to shaft, N.m. , Direct and quadrature axis currents, A. , Direct and quadrature axis fluxes, Wb-turns. Synchronous frequency, electrical rad/s. Angular position, electrical rad/s. Total moment of inertia, kg.m 2 . Number of pole pairs. Magnetic flux linkage of permanent magnets, Wb. , Direct and quadrature axis voltages of stator, V. Equivalent Thévenin 3-phase resistances of the power factor corrected (PFC) load across the stator windings, Ω. , , Base torque, power, and speed of micro-turbine (MT), N.m, W, and rad/s, respectively. , Rotor mechanical speed and its reference, rad/s. ). , , Direct and quadrature axis currents and rotor mechanical speed calculated in each iteration, A, A, and rad/s, respectively. , τ, , FPGA arbitrary computational time-step and the desired time delay, SPI communication as well as pulse width modulation (PWM) timesteps, sec. , Generator 3-phase stator root-mean-square (RMS) voltages and currents, V and A. , , Generator 3-phase stator voltages, currents, and linkage fluxes V, A, and Wb-turns, respectively. Derivative operand. , , , Temperature controller parameters of GT. , , VSI output LC filter parameters, H, Ω and F, respectively. , Switching and output frequency of VSI, Hz. , VSI input DC and output RMS voltage, V. Amin Hasanzadeh (M'11) received his B.Sc., M.Sc. and Ph.D. degrees in Electrical Engineering from Sharif

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