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This paper proposes a control design for enhancing current sharing among distributed reactive power generators by improving cooperation among voltage controllers in a Microgrid system. A novel control approach based on sharing information with immediate neighbours as modified by current droop is proposed to regulate the voltage and to control the reactive current injection sharing in a distribution feeder. In this paper, the control algorithm uses localized information as well as from the nearest neighbors. Modified consensus shows low communication requirements, good convergence, and good sharing of the compensation current among the inverters. To evaluate the performance of the algorithm, photovoltaic (PV) systems are included in the examples. The key contribution of this paper is to use the adjacency update with a form of droop control.

Driven by rising energy demand and the goal of carbon neutrality, renewable energy generations (REGs), especially photovoltaic (PV) generations, are widely used in the urban power energy systems. While the intelligent control of microgrids (MG) brings economic and efficient operation, its potential stability problem cannot be ignored. To date, most of the research on modeling, analyzing and enhancing the stability of MG usually assume the DC-link as an ideal voltage source. However, this practice of ignoring the dynamics of DC-link may omit the latent oscillation phenomena of autonomous PV-based MG. First, this paper establishes a complete dynamic model of autonomous PV-based MG including PV panels and DC-link. Different from previous conclusions of idealizing DC-link dynamics, participation factor analysis finds the potential impact of DC-link dynamics on system dynamic performance, and different influence factors including critical control parameters and non-linear V-I output characteristic of PV array are considered to further reveal oscillation mechanisms. Second, based on the average consensus algorithm, a distributed stabilization controller with strong robustness is proposed to enhance stability of the PV-based MG, which does not affect the steady-state performance of the system. Finally, the correctness of all theoretical analysis and the effectiveness of the proposed controller are verified by time domain simulation and hardware-in-loop tests. 10.13039/501100001809-National Natural Science Foundation of China (Grant Number: 51907031)

—This paper presents an anti-islanding protection scheme for a grid tied inverter. In this scheme, the oscillation variation in frequency is estimated by Estimation of Signal Parameters via Rotational Invariant Technique (ESPRIT). The proposed system is implemented in MATLAB and real time in OPAL-RT. Series of simulation results demonstrate that nondetection zone of proposed algorithm is negligible, and the scheme is also free from nuisance tripping to other transient events.

Compared with the traditional microgrid, a smart transformer (ST)-based microgrid shows advantages in terms of higher efficiency, increased hosting capacity, and enhanced reliability. However, this novel microgrid presents challenges because of the complex resonances within the system and the interactions between ST and power converter-based distributed energy resources (DERs). Both the ST and DERs might be severely affected by each other and leads to performance degradation and system instability. To solve these problems, this paper first develops equivalent circuits of a ST-based microgrid. Then, the resonance and interaction problems are investigated based on the equivalent circuits. The active damping method is used to fully address the resonance issue and mitigate the coupling effects. To guarantee superior performance, this paper also designs high-performance control strategies for both the ST and DERs. Simulation and experimental results are provided to verify the validity of the proposed control strategy.

The interactions of more and more power electronics-interfaced power systems can worsen the power quality and the system stability in distribution networks. System stability can be addressed analyzing the source and load impedances at the interaction section and well-established approaches exist for DC and three-phase AC networks. Some papers focused also on single-phase AC systems, whose study is generally more difficult due to their nonlinear and time-varying characteristics. One viable solution to address this issue is the use of equivalent dq rotating reference frame even for single phase system so as to identify a steady-state operating condition. This paper uses this approach and proposes the small-signal analysis of a single-phase AC system that includes a current-controlled inverter synchronized to the grid via a Phase-Locked Loop (PLL). Experimental validations are provided herein to asses the feasibility of this approach and to verify the stability criteria based on the source and load impedances.

A Pulse Width Modulation method is presented in this paper for the harmonics and circulating current reduction in the power converters system. The power converter considered for this research work is a boost converter connected in an interleaved topology in a single setup. The Common-Mode Circulating Current CMCC are studied in detail in this interleaved topology setup. For the Differential-Mode Circulating Current DMCC, these two identical interleaved setups are then connected in parallel. A PWM control method is suggested for harmonic elimination and control of circulating currents inside the circuit. This method results are compared with Feed Forward and AICMC control methods. Simulation results are presented to show the effectiveness of this proposed model.

This paper discusses the switching properties of the behavioral models of integrated circuit output buffers. Present behavioral models are based on a two-piece structure defined by a linear combination of two submodels for the two logic states. These models are very accurate in the two logic states, but their state switching is sensitive to the driven loads. The analysis carried out in this paper shows that this load sensitivity stems from the linear combination defining the two-piece model. A new single-piece behavioral model is proposed, that solves this problem and has efficiency and complexity levels comparable to those of two-piece models.

The demand for high reliability and the performance-to-size ratio of multilevel inverters (MLIs) have triggered rapid growth in MLIs with the reduced number of controlled-switching devices, isolated dc sources, gate driver circuits, and voltage stress across the switching devices. However, the development of alternative MLIs away from traditional MLI mostly comes at the trade-offs amongst structural and control complexity, power loss, and industrial practicality as the number of voltage levels increase. Thus, this paper presents and analyzes a modest two-stage single-phase hybrid MLI with a high performance-to-size ratio, which generates a five-level voltage waveform across the load with a unity voltage gain, and reduced switches. In the first stage of inverter topology, the controlled-switching devices and gate drivers have been reduced by half as compared to its counterparts. Moreover, the inverter topology’s advantages have been demonstrated on an experimental setup using a recently developed phase-shifted PWM strategy.

Bifacial PV panels are emerging technologies that can increase the energy yield of the footprint in PV systems and thereby potentially reduce the cost of energy compared to the conventional monofacial PV panels. However, the increased energy yield due to the capability of harvesting the solar energy from both front and rare surfaces of the panel can potentially increase the loading of the inverters used in the system for doing grid connection, and as a consequence affect the inverter reliability performance. This paper thus provides a comparison between monofacial and bifacial PV modules in terms of reliability of the PV inverter and energy yield of the overall system. The analysis is carried out with a mission profile from Algiers, Algeria, where different Albedo and PV module installation heights are considered. The results show that both aspects can affect the lifetime of the PV inverter considerably, and they should be taken into consideration during the design of PV inverter.

The growing spread of renewable energy sources has brought the issue of providing virtual inertia to the electric power system. Virtual Synchronous Generators (VSGs) are a valid solution capable of adding inertial behavior to static grid-tied converters. While many VSG solutions are available in the literature, the proper tuning of the virtual parameters is an open issue. In particular, this paper focuses on the VSG damping using a virtual damper only on the q-axis. Starting from a brief summary of the q-axis damper winding structure, the linearized electromechanical model of such VSG is derived. This model is then used to obtain the analytical relationships between the virtual damper parameters and the dynamic behavior of the machine during electromechanical transients. Guidelines to tune the most suitable damper parameters are given, in order to obtain certain dynamic behavior from the grid side. Finally, the proposed design procedure is validated experimentally on a 15kVA grid-tied inverter.

When an open-switch fault occurs in the inverter-side of the series resonant dual-active-bridge (SRDAB) converter, the rectified DC voltage will drop by a half. One solution to maintain the continuous power supply of the converter is to regulate the duty-cycle of the rectifier output voltage. Nevertheless, it may excite the resonance between the resonant inductors and the DC capacitors and lead to severe low-frequency oscillations, which appears as the envelope of the high-frequency current. This phenomenon may trigger the over-current protection and make the SRDAB fail to ride through the fault. In this paper, a low-frequency equivalent model is proposed for the SRDAB, enabling frequency-domain analysis of the conventional single-loop voltage control. It is revealed that the oscillation depends on the duty-cycle and control parameters, and it is not possible to suppress such oscillations by the conventional control method. Thus, a dual-loop fault tolerant control method consists of an outer voltage control-loop, an inner current envelope control-loop. Also a non-linear correction unit is proposed to suppress the oscillation. Experimental tests on a 1-kW SRDAB are performed. The test results have validated the effectiveness of the proposal in terms of oscillation suppression.

Droop control method is a popular method for power sharing in islanded microgrids with parallel-connected inverters. Virtual flux droop control is a simple strategy based on the direct flux control (DFC) and hysteresis controllers, in which the active and the reactive powers are proportional to the phase angle and the amplitude of the virtual flux (integral of the output voltage of the inverter), respectively. However, because of the hysteresis controllers, it suffers from a drawback that is the variable switching frequency, which leads to the voltage and current ripples. In this paper, novel phase angle and virtual flux controllers with simple structure have been proposed which lead to a fixed switching frequency, while there is no need for the space vector modulation. Therefore, the ripples of voltage and current have been reduced. In order to evaluate the effectiveness of the proposed method, simulation studies have been carried out in Matlab/Simulink. The results show that the proposed controllers can reduce the voltage and power ripples, while the switching frequency has been fixed.

This paper deals with dual three-phase winding synchronous reluctance motor designed for increasing the drive fault-tolerance. The two three-phase windings are supplied by separate inverters. In the event of fault of either a winding phase or an inverter, the faulty three-phase winding is disconnected and the motor is operated feeding the healthy winding only. Various winding configurations are considered and compared, in terms of average torque, radial force and mutual coupling between the two windings, during the faulty operations. Considerations are given regarding the winding arrangements so as to avoid excessive torque ripple and unbalanced radial force in this operating conditions.

The BLDC-MRM is a brushless d.c. multi-phase reluctance motor with bipolar two flat tops currents in the stator with a q=1 slot/pole/phase diametrical multiphase (m>3) a.c. stator winding and a magnetically anisotropic (Ld> Lq) passive rotor. The absence of rotor windings, the not so small air-gap, the around 90° natural power angle, good torque density, simple iE, i T control, high fault tolerance and good d.c. link input voltage usage in the inverter make BLDC-MRM tempting for many applications, including heavy traction. The present paper aims a first attempt to introduce a rather complete analytical sizing method accompanied by key FEM validation for emf (by i F ) waveform, torque pulsations and realization. Thermal stress is also investigated by FEM with promising results for 1.2 MW 2/6krpm traction applications.

This paper proposes an architecture design approach for a wideband continuous-time (CT) ΣΔ modulator with ultra-low oversampling ratio (OSR). The ultra-low OSR is beneficial in terms of power consumption for both the clock distribution network and the subsequent decimation filter. In this work, three signal feedforward paths and an additional feedback path are used to reduce the power consumption. Extensive system-level simulations demonstrate the effectiveness of the proposed solutions. Furthermore, this work verifies the proposed methods by transistor-level design and simulations of a 2 GHz 4th-order CT ΣΔ modulator achieving an SNDR of 46 dB in a signal band of 250 MHz while consuming only 1.91 mW of power in 40 nm CMOS. The proposed solutions enable CT ΣΔ modulators for low power ultra-wideband (UWB) applications.

Multilevel inverter can obtain low distortion output voltage and current wave. However, dead time causes an output voltage error in the phase of inverter. Dead time error causes nonlinearity of output voltage and phase currents ripples with 5th and 7th order ripples of fundamental frequency. Current ripple decreases motor control performance. This paper presents dead time compensation for three-level flying capacitor inverter which is operated by phase shift pulse width modulation. This method is focused on the fact that power switching devices, which cause voltage error by dead time, depend on current polarities. The algorithm is simple, and the dead time is inserted at the instant of turning-on and turning-off of switching devices so as not to affect output voltage. The simulation result shows that high order harmonics which caused by dead time effect are eliminated using this method.

Coupled inductors can be used to connect cells in parallel in a voltage source inverter to increase both rated power and bandwidth. To successfully implement this strategy it is critical to achieve a balanced contribution to the output current by all paralleled cells. Circulating currents should also be controlled and minimized to prevent additional losses in the switching devices. This paper presents an effective method to achieve current sharing between inverter cells paralleled via magnetically coupled inductors, using a state feedback controller. Experimental results are presented validating the performance of the proposed balancing method.

This paper presents a three-phase converter architecture with a reduced common mode voltage to be used in photovoltaic power systems. The full-bridge architecture is modified by adding two additional switches in the DC path that allow decoupling the load from the source during the freewheeling phases. Optimized modulation strategies are analyzed and compared against the space vector modulation for the full-bridge. Extensive measurements show an improved efficiency when SiC devices are used, and a theoretical analysis links this efficiency to a marked extension of the converter lifetime.

Multilevel Modular Cascade Converters (MMCC) can be used to provide higher effective switching frequencies and reduce harmonic distortion in classical converter problems such as BESS and STATCOM. To successfully implement a MMCC in a STATCOM application it is necessary to balance dc-link voltages of the individual modules and track a reference output current. This work presents master and individual module controls utilizing feedback linearization and sliding mode control. Simulation results demonstrate that the control strategy presented in this paper can balance dc-link voltages of individual modules and provide output current tracking within the first cycle.

This paper deals with measurement and evaluation of electromagnetic noise generated by induction electric motor fed by inverter controlled by PWM. It suggests and describes possible method of evaluation the electromagnetic noise which can be used in real-time applications.

International audience; In this paper, we propose a novel TFET Flip-Flop (TFET-FF) designed to address the requirements of ULP (Ultra-Low-Power) applications, like IoT (Internet of Things), while maintaining high performance. The performance of the proposed design in terms of power, area and speed is compared with different flip-flop designs present in literature for MOSFETs, TFETs and FinFETs. The proposed flip-flop supports voltage scaling and works for supply voltages from 0.3V to 0.6V. Leakage is improved by 4 to 7 decades in comparison to state-of-the-art TFET, FinFET and MOSFET designs. With neither feedback for latch implementation nor device stacking, the TFET-FF speed is comparable or exceeds the speed of High-Performance FinFET implementation for VDD = 0.3V/0.5V. The number of transistors used for the proposed TFET-FF is reduced by 50% in comparison to CMOS and FinFET implementations.

Quazi Z-Source inverter (qZSI) is a promising inverter topology that can buck or boost input voltage without a DC-DC converter and hence can be used in transformerless configuration. This is a high efficiency solution because of single stage processing and conversion. In this paper a novel modified qZSI topology is proposed and new modulation technique is presented to reduce common mode leakage current that is generally present in non-isolated transformers feeding utility grid. The proposed inverter offers a, high efficiency and a high reliability solution in a single-phase solar photovoltaic system for grid integration. Presented topology, (1) uses phase-leg shoot through for boosting the DC voltage to the required level which eliminates the additional DC-DC converter, (2) eliminates the PWM dead-time and provides freewheeling through additional switches (smoothens output AC grid current), (3) minimizes leakage current, (4) avoids body diode conduction for main devices increasing the efficiency of the system because body diode have poor reverse recovery characteristics, (5) effectively utilizes magnetic components, (6) common mode leakage current will be reduced to 0.2% of the rated current which is negligibly small. Simulation and experimental results are verified for a 120V (peak), 15A (peak) at 0.99pf. Qatar National Research Fund Scopus

The market of PV systems is rapidly expanding during the last years and the transformerless DC/AC inverters are key components in this evolution. Despite its design and control simplicity, a transformerless full-bridge DC/AC inverter may exhibit a high leakage ground current, due to capacitive coupling between the solar panels and ground, which prohibits its employment in single-phase PV systems. Thus, multiple alternative transformerless PV inverter topologies have been developed in the past, which, however, comprise additional power devices and/or passive components. In this paper, a new modulation method is proposed for optimally controlling the power switches of transformerless single-phase full-bridge PV inverters, such that their leakage ground current is minimized. The design results demonstrate that by using the proposed technique, the leakage ground current of transformerless full-bridge inverters is reduced below the maximum limit imposed by the VDE 0126-1-1 standard, thus enabling their application in single-phase PV installations, instead of more complex PV inverter structures.

The finite reluctance approach is very well suited for fast modeling and dynamic simulation of permanent magnet synchronous machines with inverter feeding. This paper shows validating simulations, in both steady-state and transient conditions, carried out for a permanent magnet linear motor designed for on board ship load actuation. The basics of the method are resumed. The simulations obtained by using the finite reluctance approach are compared with FEM simulations, showing good agreement. Keywords—Dynamic model, dynamic simulation, linear machine, magnetic network, reluctance.

The new topology for a dc to ac converter based on the switched capacitor circuit was introduced recently. The promising features of low harmonic content, high efficiency, MPPT facility and voltage step up characteristics makes it a good candidate for grid connected-renewable energy sources. The harmonic content is further minimised in this paper by introducing multiple current modulators, each connected to a PV panel. It is also shown that the circuit also tracks the Maximum Power Point of the output power of the photovoltaic panel with varying irradiation from the sunand ambient temperature. The work is carried out by extensive simulations on PSIM.

Frequency and voltage regulation in droop-based microgrids is generally modeled using small-signal analysis. In order to ensure accuracy, existing models do not decouple real and reactive power responses. However, the models become complicated and hide the real decoupled dynamics. This paper proposes a simple linear model which makes it possible to discern the different dynamic properties and to readily design the control parameters. The proposed model is validated by comparison with an accurate small-signal model and by simulation results. The effect of not considering the load is also evaluated. This work was partially funded by the Spanish Ministry of Economy and Competitiveness under Grants DPI2010-21671-C02-01 and DPI2009-14713-C03-01, and by the Public University of Navarra through a doctoral scholarship.

This paper recapitulates an analytic control model for arbitrary island grids and presents findings on the dynamic behaviour of purely inverter driven island grids. Pole zero plots of different grid structures are presented and the influence of several inverter parameters on the grid stability is analysed. Findings show that for improved grid stability the inverter’s time constants should also relate to their rated power. Further it is shown how P-Q rotation in the droop control can improve the integration density of renewable power sources in the distribution grid.

In this paper a model-based predictive control (MBPC) scheme for the current control of induction machines is presented. The controller directly selects the optimal switch state of the inverter. The proposed scheme uses a longer prediction horizon and a limited amount of optimal switching instants to reduce the average switching frequency. The next iteration of the MBPC-scheme is performed at the established optimal switching instant, as such suppressing the receding horizon property for short time spans. The proposed method is compared to a more conventional MBPC-scheme with a very short prediction horizon. Both simulations and experiments clearly show a significant reduction in average switching frequency. However, with a reduction in switching frequency the torque ripple is increased. To correctly asses the properties of the different schemes, a key performance indicator is proposed that offers a fair and unbiased comparison in terms of switching frequency and torque ripple.

If the switches of two resonant SEPIC converters are capacitively coupled, it is possible to obtain a self-oscillating converter in which the two power stages operate in interleaved mode. This paper describes a topology where the inputs of two SEPIC converters are connected in series, thereby sharing the input voltage. For the same output power and switching frequency, the voltage stress of the switches is reduced by a factor of two while the voltage transformation ratio is doubled. This modification is possible with addition of only two capacitors in the power stage and a biasing circuit. Design considerations and challenges are investigated. To verify the proposed design, a 70 V input, 37 MHz prototype was built using low-cost switching and passive components, and experimental results are presented. Peak observed efficiency was 82%.

The growing diffusion of single-phase distributed generators in LV distribution networks, already stressed by unbalanced loadings, is likely to give rise to further power quality problems, mainly voltage magnitude and unbalance issues. This paper first focuses on some recent normative decisions regarding the reactive power management for LV active users, then investigates the effects of a stronger participation of the latter to the network voltage regulation, enabled by a suitable local control strategy based on these standards. Simulations on a case study LV network are conducted for a 24 h time window, using a Backward-Forward sweep solution method.

Inverter-fed Induction motor performance is known to be noticeably affected by the supply voltage waveform. Nevertheless, the prediction of how supply voltage harmonics impact on motor operation in terms of losses, noise and thermal behavior is still a problem that can be hardly approached through simulations and analysis, therefore experimental data constitute an important source for information. In this paper the test results of two high-power induction-motor drives are presented showing their performance under different voltage waveforms. Among the other things, it is shown how low-frequency distortions in the supply voltage may have considerably stronger impacts on motor behavior than PWM harmonics, although the overall THD under PWM supply is higher.