The voltage level multiplier module is an emerging class of compact power electronic topologies that aims to maximize the power quality and conversion efficiency using minimum active and passive components. The promising merits of voltage-level multiplier module inverters (VLMMI) render them ideal for integrating renewable energy into microgrid environments. This paper presents a new intelligent direct power control (IDPC) technique for grid-connected VLMMIs to control the power flow directly through a distributed energy resource management system (DERMS). Furthermore, a robust control algorithm is developed using sliding mode control theory to regulate and stabilize the voltage and current of the VLMMI in the grid-connected mode of operation. Preliminary simulation results confirm that the proposed IDPC supported by the robust controller allows VLMMIs to effectively operate in microgrids and accurately respond to a DERMS.

This paper develops a robust artificial intelligent controller for a compact multilevel converter to operate in grid-following and grid-forming modes without islanding detection. The proposed controller is designed using sliding mode control, a multilayer Perceptron neural network, and a unique supervisor to select the operation mode of the converter automatically. Compared with islanding detection-based control methods, a single unit controller is required, which is more robust against false trips. The simulation tests also confirm that this technique is highly accurate and only causes a non-detection zone when the load demand is equal to the peak power of the converter.

Compact Multilevel Converters (CMLCs) as an emerging class of bidirectional Multilevel Converters (MLCs) offer the best trade-off between components count and power quality. Nonetheless, reducing the conduction passes as well as using minimum semiconductor devices cause reliability issues and impose maintenance costs, as voltage stress degrades the performance and lifetime of the components. Accordingly, this paper introduces a novel predictive form of voltage stress for semiconductor devices used in CMLCs to address the related issues. In the end, verification results provided through a grid-connected nine-level Packed E-Cell converter demonstrate the effectiveness of the proposed Voltage Stress-based Model Predictive Control (VSMPC) technique in dealing with voltage stress as well as tracking the other essential control objectives, simultaneously.

In this paper, an adaptive fuzzy passivity-based control strategy is proposed to provide stable operation for a grid-tied nine-level packed E-Cell (PEC9) converter. Passivity theory is developed in the first step to enable the error dynamics of the PEC9 converter currents to reach a much more effective convergence rate using the proposed damping coefficients. Moreover, various operating margins are achieved for the damping coefficients through PEC9 current errors-based 3D curves. In order to establish online estimation for the damping coefficients, the fuzzy controller and Artificial Neural Network (ANN) are combined. Experimental and simulation results are employed to validate the accuracy of the proposed control technique under load variation, parameter mismatch and DC-link voltage variation.

This article proposes a passivity method synthesized by an adaptive neuro fuzzy inference system (ANFIS) to control a grid-tied nine-level packed E-cell (PEC9) inverter. PEC9 is an optimized components count of single-phase, single-dc-source, compact multilevel converter with an appealing feature of dc capacitors horizontal extension. Indeed, PEC9 forms a single auxiliary dc-bus to actively balance its voltages so as grid-tied controller would not be charge of capacitors voltages balancing. Hence, the proposed intelligent-based passivity control (IPC) is designed using only the dynamical model of the PEC9 inverter current. The zero dynamics of state variable errors are obtained and a damping coefficient matrix is presented to theoretically analyze the convergence rate of PEC9 inverter currents under the proposed control functions. In addition, various operating margins of damping coefficients are inquired. So, using the margins, a trained ANFIS as an online estimator tracks the damping injections. It precisely regulates the damping coefficients in unstable conditions; thus, the excellent PEC9 inverter operation is guaranteed. Experiments and simulations validate high reliable performance of the proposed IPC technique under various grid-tied operational conditions.

The presence of nonlinear loads challenges the power quality regulation in stand-alone and grid-connected converters. Employing bulky passive or active filters is common to filter out the harmonics; but this is a costly solution. In this paper, an Intelligent Harmonic Suppressor (IHS) using fuzzy control theory and Second Order Band Pass Filter (SOBPF) is proposed to mitigate the harmonics caused by unknown nonlinear loads in a stand-alone nine-level Packed E-Cell (PEC9) inverter. PEC9 is a promising multilevel topology which can generate a quasi-sinusoidal voltage waveform only by a single dc source. In the proposed IHS technique, PEC9 is forced by the fuzzy controller to track the desired current reference that is provided by an adaptive control law based on the load impedance. Simulation results verify that since the undesired harmonics emerge in the measured signals applied to the control loop, using SOBPF before the fuzzy control inputs notably reduces THD while the references for the load current and the auxiliary dc capacitors voltages are accurately tracked.

Battery-based electric spring has a great potential of providing various ancillary services in distribution systems. However, by far, a half-bridge inverter has been mostly employed as a single-phase electric spring. Thus, in this work, a seven-level electric spring with superior efficiency and power quality performance using modified seven-level pack U-cell inverter suitable for both low and medium voltage applications has been introduced. The operation principles, topology, comparison with the conventional electric spring configuration, and sensorless seven-level pulse width modulation method of the introduced seven-level electric spring has been presented. Furthermore, an RCD based control method has been utilized for the seven-level smart load setup for the first time. Finally, extensive simulation results have verified operating characteristics and performance of the proposed multilevel electric-spring-based smart load for both stabilizing the point of common coupling voltage and improving the power factor of the noncritical load during various steady-state/transient conditions.

This paper proposes a control strategy for a nine-level Packed E-Cell (PEC9) converter to act as Static Synchronous Compensators (STATCOMs). The controller is aimed to support grid stability through controlling the injection of PEC9 active and reactive power. The controller is designed in such way which second-order responses for the errors of PEC9 power can be reached. By analyzing the responses, a tuning process is presented for the controller coefficients as well. Simulation results in MATLAB/SIMULINK verifies the ability of proposed PEC9-based STATCOM.

Compact Multilevel Converters (CMCs) are type of converter topology where both DC sources and AC loads are clamped by active switches and the load current directly passes though DC sources. The H-bridge has been emerged as the first generation of CMCs, but later H-bridge has been developed as Packed U-Cell (PUC) using auxiliary DC capacitors instead of extra DC sources and optimizing number of components. Recently, an advanced CMC based on the PUC has been introduced so-called as Packed E-Cell (PEC) which is further optimized compared to PUC topology. The main challenge in CMCs including PEC is to balance the auxiliary DC capacitors in a low switching frequency technique. In this paper, DC capacitor voltage balancing of PEC is investigated at a low switching frequency operation using Selective Harmonic Mitigation (SHM) modulation technique. Some theoretical and simulation analyses have been performed to evaluate the performance of PEC under low switching frequency operation.

In this paper, an improved Adaptive Neural Fuzzy Inference System (ANFIS) based controller has been designed to regulate the capacitor voltage and load current of Seven-Level Packed U-Cell (PUC7) inverter. PUC7 is an affordable topology due to the least power switches and DC sources; but, it suffers from unstable adjusting capacitor voltage level. Proportional Integral (PI) as a simple linear control method causes overshoots and undershoots in transient response and conducts the system to unstable mode when some uncertainties are existed in the load. However, the proposed ANFIS control method regulates the load current and balances the capacitor voltage without any overshoot or undershoot and transient response even in presence of nonlinear loads. Simulation results of stand-alone mode of operation of PUC7 obtained by MATLAB software also confirm usability of ANFIS control loop to achieve unity power factor, minimum Total Harmonic Distortion (THD) and minimum capacitor voltage ripple while the PUC7 inverter is connected to an AC dynamic load.

This paper presents a control strategy for a Multi-Terminal MMC-HVDC system to enhance the frequency response of AC grids. Using power sharing of both upper and lower arms of MMC combined with a basic equation of control functions, the proposed upper and lower control functions are extracted. In these proposed control functions, total wasted power in both upper and lower arms along with the power generated by the arm inductances are considered. The proposed control functions are capable of providing accurate performance with fast frequency response for AC grids with the existence of both load variations and DC voltage fluctuations. MATLAB/SIMULINK software is employed to demonstrate the merit of proposed controller.

This paper presents a robust fuzzy-based control strategy for single-phase five-level PUC5 inverter in grid-connected mode that can properly improve the grid power quality. The proposed control technique is able to provide unity power factor between grid voltage and current by accurately injecting the needed load currents in presence of unmolded uncertainties. To provide robust property, the proposed fuzzy-based control strategy for accurate operation of PUC5 in grid-connected conditions has been designed. Simulation results in MATLAB software verify the proposed control technique abilities at achieving very low THD grid current, unity power factor, appropriate output voltage and SPWM reference signal.