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This paper proposes a synergistic operation of distributed compensators. By a synergistic operation, a part of a distribution system can behave as a single element. Two distributed compensators are responsible for achieving the operation. The grid may demand three requirements from the element: cancellation of the input current, operation under unit power factor and injection of active power into...
In this work, a Shunt Active Power Filter (SAPF) using a multilevel inverter operating in low switching frequency is used to improve the power quality in electric metro power supply systems. The proposed topology is a three level/phase voltage source Neutral Point Clamped (NPC) and the Conservative Power Theory (CPT) is used to extract the harmonic currents. A current control schema sensing only the...
Shunt active power filter, when used with non linear loads, provides an elegant solution to reactive power compensation as well as harmonic mitigation leading to improvement in power quality. The present study deals with fuzzy logic and neuro based controllers' viz. neural network control and neuro fuzzy control for shunt active power filter. Their superiority over PI type of controller is demonstrated...
Second and third-order passive filters (LC and LCL) are interesting filters used for grid-connected inverters. Due to the stability problems of this filter regarding resonance frequency, additional damping resistor suggested for an LCL filter. However, the resistor value has a considerable impact on the response of the filter, voltage and current harmonic distortion and system power loss. In this...
In electrified vehicles, distinct harmonic currents and corresponding ripple voltages exist mainly on the DC-links of the traction inverter and single-phase high voltage (HV) battery charger. Those harmonic currents are normally filtered by a bulk capacitor or an additional active filter (AF) circuit. This presents an obstacle for improving the power density as well as reducing the cost. This paper...
Due to the rapid increase of nonlinear and unbalanced reactive loads in 4-wire distribution systems, various power quality issues such as harmonics current, unbalanced load currents, neutral current and low power factor occur. The need for green and renewable energy sources increases daily due to increase in demand for electrical power. Photovoltaic (PV) energy is an important renewable technology...
This paper discusses a circuit configuration for a single-phase current source inverter that features power decoupling capability. This converter consists of a resonant type isolated DC/DC converter, power decoupling circuit, and a current source inverter (CSI). The proposed converter can be achieved the low input voltage ripple without a large smoothing inductor or electrolytic capacitor. In this...
This paper presents a current dependent droop control method for equal load sharing of parallel connected inverters without any communication between them. Voltage droop in d and q axis voltage is achieved by using d and q axis currents. Each inverter works on voltage controlled mode where it controls the filter capacitor voltage. The outer voltage control loop generates current reference for filter...
In this paper a new active output filter” (AOF) for variable speed constant frequency power system in aerospace applications is proposed. The proposed AOF is envisioned as a power semiconductor filter block. In the proposed system the passive L-C output filter components are replaced by an H-bridge. The H-bridge is operated at high frequency to inject voltage harmonics to achieve a sinusoidal output...
An analytical solution in a closed form of current responses of the B4 converter connected to the three-phase unbalanced grid via the LCL filter is presented in the contribution. The method can serve as a tool to analyze quickly current responses in steady states for a selected grid filter topologies and parameters.
In this paper, a control scheme to improve load sharing among inverters of different power ratings in an ac microgrid is proposed. The proposed control scheme shapes the output impedance of the inverters independent of the voltage controller parameters and minimizes the requirement of the virtual impedance for proper load sharing. Results show that system stability improves. Simulation and experimental...
This paper presents LCL-filter configurations for parallel connected grid inverters. Three different configurations can be used in an LCL-filter implementation. All of these can be dimensioned to produce the same harmonic attenuation. However, the filter resonance frequencies and how they vary with respect to the number of inverters differs between the configurations. This paper presents and analyses...
In open-end winding AC motor drives, terminals of stator phases are normally connected between two inverters, normally, of the same type and size. In the present paper, an alternative configuration is studied where the machine is supplied exploiting two different converters: a main multi-level inverter and an auxiliary two-level inverter. The last operates as active power filter in order to eliminate...
Parallel-connected inverters are used for high power application. Due to the parallel-connection, there exists a circulating current which does not contribute to the ac side current. The analysis presented in the paper shows that the circulating current is affected by the dead-time. The effect of the dead time on the circulating current for the space vector pulse width modulation (PWM) and a discontinuous...
Several types of energy recovery systems (i.e. shaft generators etc.) have been installed in marine vessels, in order to reduce the fuel consumption and ultimately improve the efficiency of the vessels. In this paper, an energy recovery system utilizing the thermal losses of a real ship is investigated. The main goal of this work is to improve the overall efficiency of the ship. Therefore, a theoretical...
The objective of this paper is to propose a simple structure for reactive power control (RPC) of AC Photovoltaic (AC PV) modules. With the proposed structure, a cost-effective microcontroller can be adopted to achieve an effective reactive power control in order to support the grid voltage within acceptable bounds by absorbing or supplying reactive power. Moreover, the sliding mode control (SMC) is...
A space-vector hysteresis modulation (SVHM) technique is presented in this paper for three-level neutral-point-clamped (TL-NPC) multilevel inverter for active power filter (APF) applications. The main responsibility of this modulation technique is to force the actual current to reach the reference current and, simultaneously, balance the capacitor voltages. This scheme is implemented in the stationary...
The massive spread of distributed generation has created problems difficult to solve. Grid connected system models allows to perform simulations to study how these systems interact with the grid. In literature there are no complete model of single phase grid connected systems. The aim of this work is the study and the complete description of a single phase grid connected system in all its part: inverter,...
The paper describes design and control of LCL filter with active damping. The LCL filter is used in a single phase grid connected inverter. The performance of two different active damping methods is compared to passive damping by simulation.
This paper develops a flexible control strategy for DG inverters in a microgrid application with load current decomposition based on Instantaneous Power Theory (PQ). For grid connected mode of operation, the control strategy simultaneously supply all or part of the load current components allowing the DG system to inject its available energy, as well as to work as an active power filter, mitigating...
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