In this paper, a grid connected PV system acting as shunt active power filter for power quality enhancement is presented. Further, a DC-DC boost converter is used to interface the photovoltaic generator with the grid, which provides a continuous power flow from the PV generator into the grid through a Voltage Source INVERTER (VSI). Hence, a nonlinear backstepping control method with predictive direct power control for the shunt active power filter side is presented, and a suitable backstepping DC-DC boost converter is also developed, with a view to reduce harmonic currents and insuring reactive power compensation under nonlinear loads variations on the utility grid, and also extracts the maximum amount of power from the photovoltaic generator. Processor in the Loop (PIL) co-simulation results prove the performances efficiency of the implemented control algorithms under a nonlinear load operating condition.

In this paper a new topology based on “Z source INVERTERs” is introduced. In the proposed structure, two inductors of the impedance network in conventional Z Source INVERTER are replaced by two transformers with three windings. Voltage gain of the new INVERTER is higher than other Z Source networks with any duty cycle. In order to access high output power quality, the proposed INVERTER operates at a higher modulation index (near 1). Thereby, stress of switching devices is reduced. The performance of the proposed INVERTER is verified using the MATLAB/SIMULlNK software.

This paper proposes a single-phase five-level INVERTER with a modified pulse width-modulated (PWM) control scheme. The modified pulse width-modulation technique is developed to reduce switching losses. Also, the proposed multilevel INVERTER can reduce the requirement of power switches compared to a conventional cascaded multilevel INVERTER. The modes of operation, control signals, and operating principle of the proposed INVERTER are analyzed. The INVERTER is capable of producing five levels of output-voltage (Vs, Vs / 2, 0, − Vs, − Vs/2) from the dc supply voltage. In particular, aspects of total harmonic distortion (THD) for the proposed multilevel converters are discussed. The hybrid cascaded H-Bridge INVERTER with very low switching losses is ideal for such operations. The behaviour of the INVERTER has been analyzed with the simulation and experimental results. In this paper a new five level INVERTER with reduced number of switches is proposed and MATLAB/SIMULINK results are presented.

Direct torque control with Current Source INVERTER (CSI) instead of voltage source INVERTER is so appropriate because of determining the torque of induction motor with machine current and air gap flux. In addition, Space-Vector Modulation (SVM) is a more proper method for CSI because of low order harmonics reduction, lower switching frequency and easier implementation. This paper introduces the SVM method for CSI and uses the proposed INVERTER for vector control of an induction motor. The simulation results illustrate fast dynamic response and desirable torque and speed output.Fast and accurate response to changes of speed and load torque reference completely proves the prominence of this method.

Microgrids harness the benefits of non-INVERTER and INVERTER-based Distributed Energy Resources (DER) in GRID-CONNECTED and island environments. Adoption of them with the various types of electric loads in modern MGs has led to stability and power quality issues. In this paper, a two-level control approach is proposed to overcome these problems. A state-space dynamic model is performed for Micro-Grids, for this goal, the state-space equations for generation, network, and load components are separately developed in a local DQ reference frame, and after linearization around the set point, then combining them into a common DQ reference frame. In the first level, the control of INVERTER-based DERs and some types of loads with fast response are activated, and in the second level, the control of synchronous diesel generator resources with slower response is used. In order to validate and evaluate the effectiveness of the proposed control approach, numerical studies have been established on a standard test MG under normal and symmetrical three-phase fault conditions. Finally, the simulation results are summarized.

In this paper, a new topology for boost Z-source INVERTER based on switched-inductor cell is proposed. The operating modes of the proposed INVERTER are analyzed and also a suitable control method to generate the trigger signals of the INVERTER is presented. Having a common earth between the input source and INVERTER and capability to generate a higher voltage gain by using lower amounts of the duty cycles are some advantages of the proposed Z-source INVERTER. Comparison of the proposed INVERTER with conventional Z-source INVERTERs is presented from different points of the view. Finally, the accuracy performance of the proposed INVERTER is reconfirmed through the simulation results in EMTDC/PSCAD software program.

The stability analysis of islanded INVERTER-based microgrids (IBMGs) is increasingly an important and challenging topic due to the nonlinearity of IBMGs. In this paper, a new linear model for such microgrids as well as an iterative method to correct the linear model is proposed. Using the linear model makes it easy to analyze the eigenvalues and stability of IBMGs due to the fact that it derives the eigenvalues directly and the linearization around an operating point to study the small signal stability and also use the newton-raphson method or other load flow solutions to solve these systems are no longer needed. An effective eigenvalue calculator is developed which is able to calculate the eigenvalues of IBMGs in the first few iterations of the proposed method. The proposed method provides the superior performance considering the simulation time compared to the conventional methods. The validation and comparison of the results show the performance of the proposed method.

A common method for controlling a group of parallel converters in decentralized control strategy structure in an island microgrid, the use is the droop-down characteristics of frequency ω-P and voltage E-Q. However, the problem with using this method is that the reactive power is not properly distributed (in proportion to the capacity of the micronutrients) between the micronutrients, which may lead to overload in the converters. Microgrids may also suffer from dynamic stability problems such as power fluctuations, which can be increased by switching between active and reactive power control. To avoid this problem, the X / R ratio of transmission lines is an important parameter that should be carefully considered in the design of micronutrient controllers. By linearizing and simplifying conditions, the control system conversion function model becomes a single input-single output system, which is efficient enough to show the relationship between control parameters such as slope of droop characteristics and derivative sentences, virtual impedance, and voltage controllers. Using this model, stability conditions for different parameters are analyzed. Also, to improve power distribution stability, common droop strategies are modified by adjusting the slope as well as adding nonlinear sentence sections. This approach reduces the coupling between active and reactive power control and reduces the dependence of power distribution on grid parameters such as the X / R ratio. To evaluate the reliability of the proposed model, the simulation results in a sample island microgrid in MATLAB software are presented.

INVERTERs have been widely used in renewable energy as a means of converting extracted power to grid standards. However, this power electronics equipment is highly vulnerable to failures due to its complex architecture and components. One of the main sources of failure is semiconductor switches that are critically sensitive to abnormal conditions such as high voltage. With the advent of multilevel INVERTERs, this concern has been raised considerably due to the increase in the number of switches. This paper has proposed a novel method with a neural network that can detect open circuit failure of switches and replace them with some new arrangement in the INVERTER so that it can run effectively. Simulations with MATLAB/Simulink for a seven level INVERTER, illustrate that with a switch failure, the multilevel INVERTER can work successfully. Results also demonstrate that this method is fast and can compensate for the output in less than two cycles. Therefore, it can be used in reliable multilevel applications in which the power flow should be achieved even if a semiconductor switch is broken.