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An adaptive secondary-side digital control is proposed for the series resonant converter to solve the loss of ZVS under certain input and load conditions, making it a good candidate for MHz 48V voltage regulators (VRs). By means of varying AC equivalent resistance, the output voltage regulation is achieved by controlling the duty cycle of the synchronous MOSFET. An additional control variable has...
This paper presents a study of a generalized multilevel asymmetric inverter based on a H-Bridge Cell with one Arm Series (CHB-as) and five switches. It is shown several asymmetrical arrangements of input source combinations that produce several equally spaced voltage levels with few components. Equations for determining the switching frequency employed in the low power processing cells are developed,...
In this paper, a new method to balance the DC bus capacitor voltages of two-stage AC-DC-AC converters with split-capacitor inverters is proposed. Converters use such split-capacitor inverters for various reasons such as cost, improved harmonic content and lower switch voltage stresses than those of conventional two-level, six-switch inverters, but the effectiveness of such inverters is limited by...
With the increasing penetration of renewable energy sources into modern power system, power electronic converters are commonly employed as the interface to the utility grid nowadays. During the operation of the interfacing converters, LCL-filters are usually used in order to reduce the harmonics around the switching frequency and its multiples. Although the LCL-filters have several advantages compared...
An input filter is usually required in a power supply system in order to comply with regulations, reduce EMI, and ensure that input transients are properly handled. In systems with a single input power supply and multiple output converters, the phase positioning of the converters affects the input current/voltage ripple as well as the magnitude of the input harmonics. Optimizing the phase positioning...
A new interleaved three-phase PFC AC-DC singlestage multilevel is proposed in this paper. The proposed converter uses a flying capacitor structure with standard phase-shift PWM to improve efficiency, particularly at light load conditions. In the paper, the operation and its steady-state characteristics are explained and its design is discussed. The feasibility of the new converter is confirmed with...
This paper addresses the power delivery strategy on an aircraft application consisting on seven isolated DC loads to be supplied from the AC grid. Distributed or centralized power processing is evaluated taking into account weight and efficiency. Additionally, the rectifier switching frequency has to be synchronized with an external frequency clock to minimize the interference of the converter harmonics...
This paper proposes a simple control scheme to eliminate the lower order harmonics in the line currents of the Front End Converter (FEC) of a 100 kVA Transformerless Intelligent Power Substation (TIPS) connected to the medium voltage (13.8 kV) grid through an LCL filter. Due to medium voltage (13.8 kV) and low power (100 kVA) specification for the FEC, the control technique needs to be specially designed...
A strategy to improve the power factor (PF) at the point of common coupling (PCC) for microgrid applications is presented in this paper. The position of the compensating unit is selected to correct the power factor and reduce the harmonic levels of the grid current and PCC voltage in microgrid connected distributed renewable energy sources. The proposed compensation system for power factor improvement...
This paper proposes an improved modulated carrier control for single-phase shunt active power filter, which eliminates harmonic and reactive currents at ac sources drawn by nonlinear loads. This control method directly shapes line current to be sinusoidal and in phase with grid voltage by comparing a modulated carrier signal to the average line current and making duty ratio doubled. Since the line...
In recent years, embedding ancillary functions of distributed generation (DG) have drawn great attention due to the increasing penetration of renewable energy based DG such as photovoltaic, wind turbines and fuel cells. Among these ancillary functions, harmonics compensation is becoming more interesting and important with the growth of nonlinear loads in today's power distribution system. When controlled...
This paper presents a new grid-connected delta inverter system (DIS) for large scale photovoltaic (PV) power systems. The delta inverter achieves DC to three phase AC inversion by using only three power semiconductor devices instead of six devices as in a conventional full bridge three phase inverter. This reduction in the number of switching devices contributes to higher power density for PV energy...
This paper introduces a PLL characterized by fast dynamics, wide stability range and minimal deviations. The proposed PLL is based on a frequency adaptive filtering stage to minimize the frequency and phase deviations under unbalanced conditions and harmonic distortions. Furthermore, a simple mathematical formula is introduced to modify the conventional synchronous frame based PLL to provide more...
In this paper, the analysis and calculation of the dc-link current and voltage ripple are presented for three-phase inverter with unbalanced load. The average and rms values of the dc-link current are derived. It is found that the rms value is independent of the modulation strategy and switching frequency. Apart from the high frequency harmonics, the current and voltage ripple consists of double fundamental...
In this paper, the angle estimation error in the signal injection based sensorless control using analog band pass filter (BPF) is analyzed. The analog BPF has been used to minimize a level of the injection voltage. However, the current which pass through the analog BPF is distorted and the sampled q-axis current is not zero even though the additional voltage signal is injected on the real rotor position...
This paper reports on an investigation of power losses of converters and amorphous core AC-filter inductors for a bipolar 750 V low voltage direct current (LVDC) distribution network, using electrical and calorimetric measurements. The LVDC network is a promising solution, which brings new opportunities to electricity distribution development. High power quality, reliability and high cost efficiency...
The main objective of this paper is to minimize the 120 Hz output ripple component and improve the dynamic response of an AC-DC single-stage power factor correction (PFC) buck-boost converter by using a new control scheme. In the paper, the operation of the single-stage converter is briefly reviewed and the proposed control method is introduced and explained in detail. Key design considerations for...
This paper proposes a novel approach to compensate the voltage at the point of common coupling (PCC) and the grid line current harmonics through a distributed generation (DG) interfacing converter in a weak microgrid. In the proposed approach, the PCC voltage is indirectly derived from the measured converter output voltage, DG line current and line impedance. A voltage closed-loop controller and a...
This paper introduces a versatile unidirectional ac-dc converter with harmonic current and reactive power compensation. Since numerous unidirectional ac-dc converters can be connected with ac power systems, existing commercial converters possess the ability to improve substantially the stability of ac power systems by compensating harmonic current and reactive power. In this paper, the feasibility...
Soft-switching ac-link buck-boost converters, also known as ac-link universal power converters and partial resonant ac-link converters, have received remarkable attention during the last few years. These converters can be configured as dc-dc, dc-ac, ac-dc, or ac-ac (single-phase or multi-phase). Among the numerous advantages of these converters are compactness, higher reliability, and longer lifetime...
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