In this paper a Compatible Selective Harmonic Elimination (CSHE)-PWM is designed for three-leg four-wire (3L/4W) Neutral Point Clamped (NPC) inverter. The proposed CSHE-PWM is capable of eliminating both triplen and non-triplen harmonics from phase voltages and empowers 3L/4W NPC to handle both single/three-phase and linear/nonlinear loads. It has been mathematically proved that DC capacitors self-voltage balancing is achieved thanks to direct control of phase voltage waveform symmetry. Moreover, the cancellation of specified triplen and non-triplen orders has the advantage of having low capacitors voltage ripple. Therefore, the applied technique not only helps removing one leg of the inverter that reduces associate complex calculations and switching losses, but also directly controls phase voltage harmonic profile compared to SHE-PWM for four-leg four-wire (4L/4W) NPC. CSHE-PWM is practically tested on a NPC inverter prototype to validate the efficient harmonic elimination from the phase voltage waveforms along with capacitors voltages balancing under symmetrical/asymmetrical loads.

Foldable, origami-inspired, and laminate mechanisms are highly susceptible to deformation under external loading, which can lead to position or orientation errors if idealized kinematic models are used. According to dimensional scaling laws, laminate devices can often be treated as rigid bodies at millimeter and smaller scale deformations. However, foldable mechanisms enter the territory of soft robots at larger scales. In this paper, we show the effect of external loads applied to a laminate, 2-DOF parallel robot and the corresponding errors during a pointing task. We then present two control methods, based on deep learning, that compensates for errors caused by the material deformation in foldable robots. For each proposed control method, a Deep Neural Network (DeepNN) is trained to learn the end-effector's deformation model in no-load and loaded conditions. A DeepNN called an updating network is trained and applied in real-time using measured sensor data, in order to transfer updated weights into another DeepNN called the target network. The target network generates control signals with the aim of compensating for the end-effector's error in tracking a desired trajectory. We evaluate our proposed control methods when applied to a laminate robotic end-effector under different external loading conditions in tracking spiral paths. The experimental results show the effectiveness of our proposed control methods in compensating for material deformation in foldable robots.

In this paper, a new asymmetric multilevel inverter (MLI) topology proposed to avoid the drawbacks of using numerous DC voltage sources and H-bridge cells in asymmetric MLIs. This structure consists of two modules. The first module is a five-level neutral point clamped (NPC5) and the second module is a nine-level packed E-cell converter (PEC9) containing a few low-cost and low-size devices. These modules are connected to each other, and a hybrid PWM modulation is operated to result in the 41-level asymmetric inverter. The proposed hybrid PWM modulation causes to operate only five low voltage and low power switches at the switching frequency, while the rest of the switches operate at low frequency or at the fundamental frequency, which reduces the size and cost of the proposed 41-level inverter. The presented simulations by MATLAB SIMULINK confirm the suitable performance of the inverter as well as the proposed hybrid modulation method.

This paper presents a grid-integrated multilevel inverter based on Packed E-Cell (PEC) structure for connecting renewable energy sources to the existing power grids. This dual source topology benefits from low number of semiconductor devices, simple robust control strategy, and smooth current of the capacitors. The shunt-capacitors of the converter are charged or discharged simultaneously to a quarter of the input DC source via horizontally extension design of the circuit. Thus, by applying only one voltage sensor and simple phase disposition pulse width modulation approach (PD-PWM), the operation of the inverter to generate 17-levels for the output voltage is ensured. For improving the dynamic performance of the converter, a closed-loop controller is designed and a precise mathematical analysis is presented as well. Accurate performance of the proposed structure is assessed by calculating theoretical analyses and simulating the inverter in MATLAB Environment.

The presented article introduces a versatile multilevel inverter based on Packed E-Cell (PEC) topology. This structure is suitable for conversion of photovoltaic energy generations to supply AC loads and uninterruptible power supplies (UPS). Requiring a reduced number of power switches and capacitors compared to other inverters along its control simplicity are the prominent merits of this converter. Thanks to the horizontally extension of the shunt-capacitors, both of them can be charged or discharged to a quarter if the input source, at the same time. Hence, by applying two isolated input sources and one voltage sensor, the proposed inverter generates 17-levels for the output voltage. Simple level shifted pulse width modulation technique (LS-PWM) is used to control the operation of the proposed inverter. Finally, the accurate performance of the proposed multilevel structure is investigated through MATLAB simulations.

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.

In this paper a novel single dc-source switch-capacitor compact multilevel topology is designed based on Packed E-Cell to have the boosting potency for the 11-level operation and to merit as a reliable AC-DC converter for fault tolerant capability. The proposed single-phase compact converter is reduced the active/passive components counts while the output voltage levels are increased which it includes 6 normal power switches and 3 bidirectional switches as well as 2 dc capacitors as the auxiliary dc sources. While the conventional compact converter is incapable of fault tolerant operation, the proposed topology could emerge as a reliable while it has the boosting ability due to its switched-capacitor feature. Moreover, the dc capacitors are actively balanced thanks to various switching states redundancy. The proposed single-phase switched-capacitor converter is validated by theoretical analyses as well as simulation results obtained by Matlab-Simulink where it shows the accurate dc capacitors voltages balancing and prefect 11-level generation in the AC output terminal.

An accurate reference current detection (RCD) algorithm with the ability of double-frequency oscillation cancellation (DFOC) is designed in this paper to control a nine-level packed E-cell (PEC9) as a single-phase active power filter (SPAPF). The reference current is detected through DFOC-based RCD and subsequently injected by the converter. The detected current contains all unnecessary components and is accurate enough to keep the grid current in sinusoidal form with the THD under the permitted threshold. The proposed PEC9-based SPAPF not only guarantees the power quality at the grid side, but also benefits all advantages of PEC multilevel converter. The effectiveness of the proposed SPAPF is assessed in comparison with conventional one and its performance is investigated via simulation studies by using MATLAB/SIMULINK software.

In this paper, a simple space vector modulation called 1D-SVM integrated with an active capacitor voltage regulation algorithm is applied to the appealing single-phase single DC source nine-level (PEC9) inverter. The proposed 1D-SVM reduces the switching losses by avoiding the additional switching in the middle of defined switching period and also provides the better capacitor voltage regulation compared to carrier based methods. Additional switching could be imposed when the carrier base methods integrated with the capacitor voltage regulation algorithm in PEC9. But, the proposed modulation technique not only prevents the additional occurrences but also decreases the ripples of the capacitors voltages so it can decrease the size of the capacitors. The 1D-SVM calculates and determines a duty cycle for the whole single-phase multilevel converter in each sampling time. The performance of the proposed 1D-SVM for the PEC9 capacitor voltage regulation has been investigated by simulation tests in Matlab-Simulink environment.

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.

This paper proposed a PI based control technique for grid-tied application of recent introduced compact multilevel inverter so called as Packed E-Cell. The nine-level Packed E-Cell (PEC9) benefits the advantage of single auxiliary and main dc source where the dc capacitors are placed in a horizontal extension on the single auxiliary dc link where simultaneous charging and discharging with effective redundant switching states are provided. Therefore, PEC9 is an active capacitor voltage-balancing converter where the capacitors voltages are adjusted to the right amplitude using only redundant switching states. Thanks to this prominent advantage, PEC9 is an appropriate nine-level topology for grid-tied inverter as the capacitors voltages are not required to be involved in grid-tied control technique. Therefore, it was shown that PEC9 inverter can be perfectly controlled with a simple PI technique for grid-tied configuration. The proposed PI-based technique has been tested using Matlab-Simulink on grid-tied PEC9 inverter under both steady-state and dynamical operation.

Tuning the stiffness of soft robots is essential in order to extend usability and control the maneuverability of soft robots. In this paper, we propose a novel mechanism that can reconfigure the stiffness of tubular structures, using pinching to induce highly directional changes in stiffness. When pinched, these tubes can be then utilized as flexure hinges to create virtual joints on demand; the orientation of the hinge axis can additionally be selected via control of the distribution of pinch forces on the surface of the tube. Through proper material and geometry selection, passive shape recovery is observed when pinching forces are removed; a proposed active shape recovery technique can further assist the tube to recover its initial shape in order to re-configure the hinge in a new orientation. The proposed mechanism has been validated in FEA as well as experimentally, looking specifically at the relation between pinching force and curvature change, as well as comparing tube stiffness between pinched and unpinched configurations. The experimental prototype detailed in this paper - and demonstrated in the associated video - is capable of controlling the generation and recovery of flexure hinges at multiple orientations around the radial axis of tubes on demand.

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.

A new nine level inverter is presented in this paper. It combines PUC and NPC topologies to create a new competitive converter that makes use of small count of power devices to generate more voltage levels. A PWM technique is designed to insure the self balancing of capacitors voltages. Moreover, no filters or regulation loop is required which permits a low inverter and installation cost. Authors make use of Matlab Simulink environment to perform the simulation of the proposed concept. Dynamics of the latter was verified against load and DC source voltage change.

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.

A control technique based on dynamic model of stand-alone single-phase voltage-source converter (SPVSC) in dq reference frame and droop curve equation is proposed in this paper to stable the voltage of point of common coupling (PCC) when renewable energy resources (RERs) are linked in a microgrid structure. The proposed control strategy is designed with respect to the aimed state variables of PCC frequency and voltage magnitude as well as the droop curve specifications. Moreover, an evaluation on PCC voltage frequency and voltage magnitude-based curve is presented for further analyzing the proposed controller performance. Simulation results in MATLAB/SIMULINK software prove the abilities of proposed controller in reaching stable operation of PCC voltage in microgrid application under load alteration.

This paper presents a thorough study on Five-Level Packed U-Cell inverter called PUC5. The main advantage of PUC5 topology over other popular multilevel ones is the redundant switching states, which facilitate the voltage balancing of the flying capacitor in its configuration. Switching states of the PUC5 inverter are analyzed to ensure an easy voltage balancing process. That voltage controlled auxiliary capacitor helps generating five identical voltage levels at the output using a single DC source. A full comparison is done to other 5-level inverter topologies to reveal the dominant features of the PUC5 structure. Moreover, some discussion on the controller design for the PUC5 inverter is conducted in grid-connected applications which indicates similar procedure performed for conventional 2-level ones due to featuring single-dc-source configuration. Various experimental results are shown in each discussion for better understanding.

In this paper, Selective Harmonic Mitigation (SHM) and Selective Harmonic Elimination (SHE) modulation techniques are combined to generate the appropriated firing pulses for a 4-leg 3-Level Neutral Point Clamped (NPC) inverter. SHM modulation technique is applied to the phase legs in order to get a desired modulation index (ma) and to mitigate the lower order odd non-triplen harmonics (5th, 7th, ...) while the fourth leg firing pulses are generated using SHE modulation technique to eliminate the major low order odd triplen harmonics (3rd, 9th, ...) completely. It is demonstrated that this hybrid modulation technique can reduce significantly a vast range of harmonic orders in the NPC inverter output voltage when compared with the results achieved when using only SHE modulation technique in the four legs of the inverter. To avoid the generation of odd non-triplen harmonics in the SHM phase legs that can not be eliminated with the fourth SHE leg, the Simulated Annealing (SA) heuristic algorithm used to find the SHM switching angles is tuned in order to provided suitable oddnon-triplen harmonics distortions which can be eliminated with SHE technique. Moreover, since in dynamical applications the modulation index has to be changing continuously, the SA algorithm has also been designed in order to provide a smooth switching angles set to avoid undesired transients harmonic contents.

This paper presents a 7-level cascaded H-bridge (CHB) multilevel inverter using a single DC source. The second DC bus is a capacitor that its voltage is controlled by switching sequences. The capacitor voltage is regulated at half of the DC source amplitude to have seven voltage levels at the output. Seven voltage levels include each DC bus voltage, their sum and subtraction. Switching pattern is designed based on the redundant switching states and multicarrier level-shifted pulse width modulation (PWM) technique to help controlling the capacitor voltage at the desired level. Simulation results are presented to validate the effective voltage balancing procedure integrated into switching technique and consequently generating the 7-level voltage waveform at the output with low harmonic contents.

Three-phase four-leg neutral point clamped (NPC) inverter is more suitable in dealing with all sort of the loads especially unbalanced/nonlinear due to harmonics issues. Most control strategies applied on four-leg NPC are classified as high switching frequency lead to high power losses and low efficiency. In this paper, selective harmonic elimination pulse width amplitude modulation (SHE-PWAM) technique has been implemented on a four-leg NPC inverter to reduce the switching frequency properly. In SHE-PWAM technique, the amplitude of input voltage is considered flexible in order to eliminate one more harmonic order without increasing switching frequency. The obtained switching angles of phase legs and amplitude of input voltage are used to eliminate the non-triplen harmonics (5th,...,23th) from the output voltage. On the other hand, switching angles calculated for the fourth leg are considered to eliminate the triplen harmonics (3th,...,21th) from phase voltage. The performance of proposed technique is verified by Matlab/SPS simulations.