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A reliable islanding detection method is one of the most important function of a well designed inverter based distributed generation (DG) system. Active islanding detection methods have negligible non-detection zone, but they bring some power quality issues to the network. In this paper an islanding detection method which addresses constant current inverter based DGs is introduced. It has both high...
As the output power of the photovoltaic (PV) cell changes with the insolation , PV cell temperature and cell voltage changing. It is necessary to control the operating point to draw the maximum power of the PV cell in order to increase system efficiency. In this paper, two-level single phase PV grid-connected system is designed, which mainly includes PV cell, BOOST circuit, inverter, filter and the...
This paper proposes a current control strategy with zero steady-state tracking error for grid-connected boost-inverters. Two boost converters are controlled separately to achieve both output current tracking and balanced output voltages. Based on cascading control and feedback linearization, the inner and outer-loop controllers are derived combining the inversion of boost converter model and the output...
DC/DC converters have been tremendously utilized nowadays. In some special applications such as military, aerospace, and precision instrumentation, the output voltage ripple of DC/DC converters has to be maintained in an acceptable level to achieve superior performance. For example, DC/DC converters are tied with inverter for adjustable speed motor controls or renewable energy interface with utility...
This paper proposes an indirect current control algorithm for seamless transfer of three-phase utility-interactive inverters. With the proposed method the inverter is able to provide critical loads with a stable and seamless voltage during the whole transition period including both clearing time and control mode change. The LCL filter design which is suitable for the indirect current control is also...
Modular multilevel converter (MMC) is one of the excellent selections for high voltage and high power conversion applications without transformers. It provides the advantages such as high modularity, availability, low generation of harmonics, etc. However, the circulating current distorts the leg currents and increases the rated current of power devices, which further increases system cost. By controlling...
This paper deals with design of a synchronous frame control strategy for single-phase inverter-based islanded distributed generation (DG) systems. Although, implementation of these regulators requires a minimum of two independent phases in the system, the required orthogonal phase is generated through the use of a first order all pass filter (APF). The essence of the proposed control strategy is to...
This paper presents a current control strategy to reduce the maximum common mode voltage levels of a three-phase inverter in adjustable speed drives application. Any reduction of the common mode voltage leads to a decrement of the high frequency related issues of AC drives such as leakage current, EMI noises, shaft voltage and motor bearing damages. Proposed strategy decreases the number of switching...
The unified power quality conditioner (UPQC) is a combination of back to back connected shunt and series active power filters (APFs) to a common DC link voltage, which compensates voltage and current based distortions, independently. Generally the power conditioning devices are designed for complete compensation, irrespective of the requirement/priority. In this paper flexibility of selective compensation...
In this paper, a novel hysteresis current control method based on the phase of the output of voltage loop by using a single LEM current sensor is proposed. Because of having two filter inductors, the Dual Buck Half Bridge Inverter has on bridge arm shoot-through problem. Each inductor current can be independently controlled, so the power switches and the free wheeling diodes can be optimally chosen,...
This paper investigates the feasibility of using an alternator as means of harvesting energy from a stationary exercise bicycle. A switch mode converter was designed to regulate the current in the alternator rotor winding, thus regulating the power required to pedal, and consequently the power output of the bike. The complete controller design consists of this power stage, a control circuit, a startup...
In most of the situations, power electronics converters are mainly used as an interfacing device between distributed generation (DG) system and utility grid in order to meet the following objectives: 1) grid synchronization 2) active and reactive power control through voltage and frequency control 3) improvement of power quality (i.e. harmonic elimination) etc. But due to wide variation of the reactive...
This work presents the design and simulation of an ultra-low-power voltage-controlled oscillator (VCO) for MICS (Medical Implant Communication Service) band applications. The VCO is based on a single ended CMOS inverter ring oscillator. For the voltage control, current starving has been employed. Current for the oscillator is provided by a beta multiplier reference (BMR) which is highly insensitive...
This paper analyzes the two commonly used current control methods for high power, low switching frequency applications involving half bridge inverter. First, the problem of voltage balancing of two DC link capacitors in the half bridge inverter has been discussed. The two current control methods used for the comparison are hysteresis current control and ramp comparison current control methods. It...
The control of the current distribution in a two leg interleaved inverter is analyzed in this paper. Feedback is used in order to control the current distribution on the inverter legs, avoiding the use of bulky and costly passive solutions. Low THD in the output voltage is ensured by a PI compensator and a repetitive controller. The design of the current compensators was accomplished by approximating...
With the progress of “More Electric Aircraft”, power capacity of aircraft electric power system is increased. It is not easy for the power-quality characteristics of the system to be in compliance with the harmonic standards by using traditional method to compensate the harmonics introduced by the nonlinear load. Active power filter (APF) gets increasing usage in 50Hz power system for its high performance...
The article focuses on control strategies of single-phase two-stage grid connected photovoltaic (PV) generation systems. The principle and digital implementation of instantaneous current control, based upon the parameters of the inverter, is presented. This method can be used to achieve accurate tracking results and lower Total Harmonic Distortion (THD) of current. A novel Phase Locked Loop (PLL)...
This paper proposes a new fine servo system based on a new over-modulation method with priority given to d-axis voltage for interior permanent magnet synchronous motor (IPMSM). The proposed over-modulation method gives priority to the d-axis voltage to avoid the d-axis voltage saturation, and increases the amplitude of inverter output voltage to achieve the quick torque and speed responses under voltage...
In this paper, a dual-loop control scheme is proposed for inverters in three-phase four-wire microgrid applications to improve the power quality within the microgrid and the power quality of the current flowing between the microgrid and the utility grid. The control scheme involves an inner voltage loop and an outer current loop, with both controllers designed using the H∞ repetitive strategy. This...
A dual-inverter allows to increase easily the maximum available power of a given inverter. When connecting two equal inverters to a machine with open end windings, the available power will raise by factor √3. However, the dual inverter also introduces a new degree of freedom for the current, which is the zero component current. The dual inverter is known for developing zero component currents, which...
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