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This paper presents a voltage-power droop/frequency-reactive power boost (VPD/FQB) control scheme that allows multiple voltage source converters (VSCs) to operate in parallel in a VSC fed microgrid. Each current controlled VSC in such a microgrid has its own VPD/FQB controller that sets its current references to regulate the voltage and frequency of a common microgrid bus. By drooping the voltage reference of each controller against its real power output, multiple VPD/FQB controllers jointly regulate the microgrid voltage while sharing a common load power in proportion to a predetermined ratio. Similarly, by boosting the frequency reference of each controller against its reactive power output, multiple VPD/FQB controllers jointly regulate the microgrid frequency while sharing the reactive load in proportion to a predetermined ratio. The proposed control scheme can also operate in grid connected mode. Experimental results are provided to validate the VPD/FQB control scheme. Index Terms--dq-frame current control, frequency boost, instantaneous synchronization, load sharing, microgrid control, voltage droop, voltage source converter.

Multiphase converters require a current-sharing loop to maintain equal or desired current sharing between phases or paralleled modules. The current-sharing loop is highly sensitive to current-sensing accuracy. In this letter, a method is presented to achieve auto-tuning of the current-sharing loop in multiphase converters while adaptively calibrating the current sensing based on power conversion efficiency. This is achieved without the need for a precise calibration reference or resistor and with no dependency on sensing accuracy. A digital controller implementation of the method is described and experimental results are obtained for a 0.84 V/30 A two-phase buck voltage regulator. Index Terms--Auto-tuning, calibration, converter, current sensing, current sharing, dc-dc, efficiency, multiphase, voltage regulator.

A fuzzy-neural sliding-mode (FNSM) control system is developed to control power electronic converters. The FNSM control system comprises a neural controller and a compensation controller. In the neural controller, an asymmetric fuzzy neural network is utilized to mimic an ideal controller. The compensation controller is designed to compensate for the approximation error between the neural controller and the ideal controller. An online training methodology is developed in the Lyapunov sense; thus, the stability of the control system can be guaranteed. Finally, to investigate the effectiveness of the FNSM control scheme, it is applied to control a pulsewidth-modulation-based forward dc--dc converter. Experimental results show that the proposed FNSM control system is found to achieve favorable regulation performances even under input-voltage and load-resistance variations. Index Terms--Adaptive control, asymmetric Gaussian membership function, converter, fuzzy neural network, sliding-mode control.

This paper presents system modeling, modified space vector PWM implementation (MSVPWM), and control system design of a Z-source converter. For an electrical analysis of the fuel cell powered systems, the fuel cell system is modeled by an R-C circuit including its voltage-current polarization characteristics. A discrete-time state space equation is given to implement digital control and a space vector pulse-width modulation technique is modified to realize the shoot-through zero vectors that boost the dc-link voltage. Three discrete-time controllers and an asymptotic observer are designed. Index Terms--Digital control, distributed generation systems, dynamic model, fuel cells, space vector PWM, Z-source converter.

This paper presents a control strategy for a variable-speed pitch-controlled wind turbine (WT) generation scheme for the supply of an autonomous system with no energy storage units. The synchronous generator includes two three-phase stator windings displaced by 30[degrees] that are connected to the transformer load through two dc links with voltage source inverters (VSI). Following priority rules, the load is divided into steps. Each load step can be supplied by the WT when the wind speed varies between two predefined speed levels. The first goal of the WT control system is to supply the load with constant real power under constant voltage as the wind speed varies between two levels and the second is to operate smoothly interchanging the load steps when the wind speed breaks through a speed level. There are two controllers: the inverter controller that keeps the load voltage constant and the pitch controller acting on the blade's angle. Using simulation techniques, the operation of the WT system and the efficiency of the proposed control strategy are demonstrated for a wide range of wind speeds. Index Terms--Converters, synchronous generators (SGs), variable-speed drives, wind power generation.

This paper discusses issues that are pertinent to the design of a linear permanent magnet generator for application in a free-piston energy converter. To achieve the required high power density, high efficiency, and low moving mass, a tubular machine equipped with a modular stator winding and a quasi-Halbach magnetized armature is employed. It is shown that the machine design can be optimized with respect to three key dimensional ratios while satisfying other performance requirements. It is also shown that, when the generator is interfaced to an electrical system via a power electronic converter, both the converter volt-amps rating and the converter loss should be taken into account when optimizing the machine design. The performance of such a tubular generator is demonstrated by measurements on a 10-pole/9-slot prototype machine. Index Terms--Design optimization, free-piston IC engine, linear machine, permanent magnet machine.

In this paper, a new voltage modulation technique named 'unified pulsewidth modulation (PWM)' is described for high-performance voltage generation in a three-phase voltage-fed inverter. By considering the operation of the inverter, a simple but useful concept named 'effective time' can be established and, by fully employing this concept, a new voltage modulation technique is presented with a detailed explanation and actual test results. The results show that various carrier-based PWM schemes can be implemented with reduced computational burden and a seamless change from one modulation scheme to another is possible. Index Terms - Carrier-based pulsewidth modulation, effective time, three-phase voltage-fed inverter.

Charge pump power-factor-correction (CPPFC) technologies, including voltage-source (VS) CPPFC, current-source (CS) CPPFC, and continuous input current (CIC) CPPFC, are presented in this paper. The charge pump concept for achieving PFC and its unity power factor conditions are derived and analyzed. The developed CPPFC techniques use a capacitor to achieve PFC function. It will be shown that the CPPFC technologies are attractive for the electronic ballast applications in Part II of this paper. Index Terms--Charge pump, power factor correction, resonant converter.

This paper introduces a true zero-current and zero-voltage transition (ZCZVT) commutation cell for dc-dc pulsewidth modulation (PWM) converters operating with an input voltage less than half the output voltage. It provides zero-current switching (ZCS) and zero-voltage switching (ZVS) simultaneously, at both turn on and turn off of the main switch and ZVS for the main diode. The proposed soft-switching technique is suitable for both minority and majority carrier semiconductor devices and can be implemented in several dc--dc PWM converters. The ZCZVT commutation cell is placed out of the power path, and, therefore, there are no voltage stresses on power semiconductor devices. The commutation cell consists of a few auxiliary devices, rated at low power, and it is only activated during the main switch commutations. The ZCZVT commutation cell, applied to a boost converter, has been analyzed theoretically and verified experimentally. A 1-kW boost converter operating at 40 kHz with an efficiency of 97.9% demonstrates the feasibility of the proposed commutation cell. Index Terms--High-performance dc--dc power conversion, IGBT's, zero--current-zero-voltage switching (ZCZVS).

Charge pump power-factor-correction (CPPFC) converters using voltage-source (VS) CPPFC, current-source (CS) CPPFC, and continuous input current (CIC) CPPFC techniques are developed in this paper. Design considerations and the performance of the CPPFC electronic ballasts are discussed, analyzed, and evaluated. The experimental results show that 0.99 power factor and 10% total harmonic distortion (THD) can be achieved. It is shown that the CPPFC techniques are very attractive. Index Terms--Charge pump, electronic ballast, power factor correction, resonant converter.

The realization of line and load regulation in switched-capacitor (SC)-based converters is discussed. A duty-cycle control is based on partial charging of the capacitors in the circuit. The influence on the efficiency is pointed out. The use of inductors in SC-based converters is discussed. Index Terms--Efficiency, switched-capacitor (SC) converter, voltage regulation.