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In today's context of power generation from wind, the demand for reliable and high-performing inverters is on the rise. The quasi-Z-source inverters (q-ZSI) are gaining attention in grid-tied wind power generation systems (WPGS) when compared to conventional inverters for their inherent capability of single-stage power conversion and maximum power point tracking (MPPT) performance. However, the erratic nature of wind speed creates a constant challenge for engineers seeking to optimize the performance of wind turbines (WT). Therefore, this paper suggests a new grey wolf-optimized MPPT (GWO-MPPT) controller for q-ZSI-based grid-tied WPGS, which holds great potential for maximizing the power output of WTs. The conventional MPPT controller used in q-ZSI-based WPGS cannot guarantee stable operation during large variations in wind speed. The GWO-MPPT controller can immediately respond during wind speed variations and trace the maximum power point (MPP) without fluctuations around it, thus improving the MPPT performance. The GWO algorithm estimates the optimum rectifier DC voltage for each wind speed to locate the MPP and subsequently determines the shoot-through duty ratio for the q-ZSI. In addition, this work introduces a decoupling current control strategy supported by dual frequency modulation (DFM) for managing the grid's active and reactive power flows. The functionality of the proposed controllers is rigorously examined using the MATLAB/Simulink tool through extensive simulations. Finally, their practicality is evaluated through an experimental hardware setup. This integrated approach thoroughly investigates the controllers' effectiveness and suitability for practical implementation in WPGS. [ABSTRACT FROM AUTHOR]

To address problems that traditional two-stage inverters suffer such as high cost, low efficiency, and complex control, this study adopts a quasi-Z-source cascaded multilevel inverter. Firstly, the quasi-Z-source inverter utilizes a unique impedance network to achieve single-stage boost and inversion without requiring a dead zone setting. Additionally, its cascaded multilevel structure enables independent control of each power unit structure without capacitor voltage sharing problems. Secondly, this study proposes a current-predictive control strategy to reduce current harmonics on the grid side. Moreover, the feedback model of current and system state is established, and the fast control of grid-connected current is realized with the deadbeat control weighted by the predicted current deviation. And a grid-side inductance parameter identification is added to improve control accuracy. Also, an improved multi-carrier phase-shifted sinusoidal PWM method is adopted to address the issue of switching frequency doubling, which is caused by the shoot-through zero vector in quasi-Z-source inverters. Finally, the problems of switching frequency doubling and high harmonics on the grid side are solved by the improved deadbeat control strategy with an improved MPSPWM method. And a seven-level simulation model is built in MATLAB (2022b) to verify the correctness and superiority of the above theory. [ABSTRACT FROM AUTHOR]

In this research, a new Z-source inverter inspired by the quasi-inductor-switched Z-source inverter is presented. The new inverter has an acceptable boost factor, and gain voltage compared to the similar Z-source inverter. Also, in this new topology, the capacitors' voltage stress has been decreased compared to similar inverters. In this converter, a capacitor is replaced with the side diodes of the quasi-Z-source inverter. The input current in this inverter is continuous and it is a low figure that at the moment of switching off about 54 A (Vin = 120 V). The high inrush current damages the converter components. The operation of this inverter has been checked in different modes and the voltage and current equations of all elements have been calculated. The new converter can be extended to n-cascade, and it makes to achieve a higher boost factor with a low-duty cycle. The ingredients used in the new topology are fewer than those of the switched-inductor Z-source inverter. The analysis and extraction of all voltage stress such as capacitors, diodes, switches, all currents such as inductors, dc-link average, inrush current, voltage gain and boost factor of the new topology have been done and compared with other structures. The DC-link voltage (Vi) is 148 V with an input voltage of 120, so the boost factor is 1.43. [ABSTRACT FROM AUTHOR]

The quasi-Z-source inverter (qZSI) become one of the most promising power electronic converters for photovoltaic (PV) applications, due to its capability to perform a buck-boost conversion of the input voltage in a single stage. The control strategy based maximum power point tracking (MPPT) and proportional integral (PI) controller are well known in grid-connected with traditional configuration but not in qZSI. This paper presents a control strategy for qZSI grid-connected based on the MPPT algorithm and the linear control by PI controllers. This is complemented by the capability to efficiently transfer the harvested power to the grid, ensuring a unity power factor. The proposed control strategy effectively separates the control mechanisms for the direct current (DC) and alternating current (AC) sides by utilizing the two control variables, the shoot-through duty ratio and the modulation index. An adapted space vector modulation technique is then utilized to generate the switching pulse width modulation (PWM) signals, using these two control variables as inputs. The proposed approach was tested and validated under MATLAB/Simulink and PLECS software. [ABSTRACT FROM AUTHOR]

This paper investigates the development of pulse width modulation (PWM) schemes for three-phase quasi-Z-source inverters (qZSIs). These inverters are notable for their voltage boost capability, built-in short-circuit protection, and continuous input current, making them suitable for low-voltage-fed applications like photovoltaic or fuel cell-based systems. Despite their advantages, qZSIs confront challenges such as increased control complexity and a larger number of passive components compared to traditional voltage source inverters (VSIs). In addition, most existing PWM schemes for qZSIs lack the capability for independent control of the amplitude modulation index and duty cycle, which is essential in closed-loop applications. This study introduces innovative space-vector PWM (SVPWM) schemes, addressing issues of independent control, synchronization, and unintentional short-circuiting in qZSIs. It evaluates several established continuous and discontinuous PWM schemes, and proposes two novel decoupled SVPWM-based schemes that integrate dead time and in which the shoot-through occurrence is synchronized with the beginning of the zero switching state. These novel schemes are designed to reduce switching losses and improve qZSI controllability. Experimental validation is conducted using a custom-developed electronic circuit board that enables the implementation of a range of PWM schemes, including the newly proposed ones. The obtained results indicate that the proposed PWM schemes can offer up to 6.8% greater efficiency and up to 7.5% reduced voltage stress compared to the closest competing PWM scheme from the literature. In addition, they contribute to reducing the electromagnetic interference and thermal stress of the related semiconductor switches. [ABSTRACT FROM AUTHOR]

Abstract The appealing design known as the quasi‐Z‐source inverter (qZSI) can function in both buck and boost modes. In the meantime, model predictive control (MPC) for power transformers has attracted a lot of interest. In order to improve performance and solve the shortcomings of the current MPC, this paper suggests a low‐computation‐burden model predictive current control (LCB‐MPCC) for the grid‐tied qZSI. Two active vectors, one zero vector, and one shoot‐through (ST) vector are used in the production of the output voltage. To get around the weighting factor, a modified sliding‐mode control technique is suggested for instantly controlling the inductor current and capacitor voltage to their regulating spots. The duty cycle of the ST vector is acquired by the dead‐beat control to restrict the inductor current and significantly reduce the inductor current ripple. Additionally, an effective and quick optimal sector selection strategy is provided that uses a look‐up table to pick the optimal sector rather than a number of intricate calculations. Therefore, the proposed LCB‐MPCC greatly reduces the computational burden. To demonstrate the efficacy and benefits of the suggested technique, simulation and experimental results are presented.

A quasi-Z-source network is used to boost the DC bus voltage of a voltage source two-level H-bridge inverter to increase the voltage gain. With the increase in the DC bus voltage, the common mode voltage (CMV) also increases. The CMV is reduced using virtual space vector pulse width modulation (SVPWM). Due to the presence of a quasi-Z-source network, the expression of the CMV changes significantly with respect to the conventional voltage source two-level H-bridge inverter fed from a pure DC supply. In this paper, a detailed analysis of the origin of the CMV for the quasi-Z-source two-level H-bridge inverter is presented. Additionally, it is shown how the CMV is affected for a DC input supply taken from a three-phase diode bridge rectifier. The work also details the scheme for suitable placement of shoot-through time intervals required for boosting within the non-active time intervals in virtual SVPWM. The simulation and experimental results show the scheme is effective in increasing the voltage gain and reducing the CMV arising at the third harmonic of the desired output frequency by at least 33.33%.

Abstract Considering the non‐linear characteristics of both the input and output of photovoltaic (PV) modules and quasi‐Z‐source inverters, as well as the unpredictable natural factors such as large disturbances caused by changes in illumination and temperature, an average state model for the PV quasi‐Z‐source inverter is established. This paper uses the output current of photovoltaic module, DC‐link capacitor voltage and its integral as state variables, then an adaptive reaching law with second‐order sliding mode characteristics is designed by combining with power reaching law and variable speed reaching law. By using the sliding mode controller based on the adaptive reaching law to control the stability of the DC‐link voltage of the quasi‐Z‐source inverter and the small capacitor voltage ripple, the photovoltaic system can operate stably at the maximum power point when the temperature and illumination conditions change abruptly, and the grid‐connected effect is improved. Through SIMULINK and RT‐LAB real‐time simulation, the effectiveness of the proposed adaptive sliding mode control strategy is verified when the environment changes, which effectively improves the dynamic response speed and grid‐connected effect of the system, and ensures the global robustness of the grid‐connected system.

The appealing design known as the quasi‐Z‐source inverter (qZSI) can function in both buck and boost modes. In the meantime, model predictive control (MPC) for power transformers has attracted a lot of interest. In order to improve performance and solve the shortcomings of the current MPC, this paper suggests a low‐computation‐burden model predictive current control (LCB‐MPCC) for the grid‐tied qZSI. Two active vectors, one zero vector, and one shoot‐through (ST) vector are used in the production of the output voltage. To get around the weighting factor, a modified sliding‐mode control technique is suggested for instantly controlling the inductor current and capacitor voltage to their regulating spots. The duty cycle of the ST vector is acquired by the dead‐beat control to restrict the inductor current and significantly reduce the inductor current ripple. Additionally, an effective and quick optimal sector selection strategy is provided that uses a look‐up table to pick the optimal sector rather than a number of intricate calculations. Therefore, the proposed LCB‐MPCC greatly reduces the computational burden. To demonstrate the efficacy and benefits of the suggested technique, simulation and experimental results are presented. [ABSTRACT FROM AUTHOR]

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This paper presents a novel switched-capacitor enhanced-boost quasi-Z-source inverter (SCEB-qZSI) for renewable energy applications. The described topology is a novel power electronic converter that uses switched-capacitors to increase the voltage boost. In the meanwhile, a reduced shoot-through condition results in a higher dc-link voltage. Moreover, the proposed concept has the advantages of continuous input current, smaller current ripple, common grounding, and high output voltage gain. The proposed topology is thoroughly examined, and simulation data are used to support the theoretical analysis. The proposed SCEB-qZSI topology has potential uses in electric vehicles, industrial applications, and renewable energy systems which may develop by using the inexpensive components making it an attractive option for applications that have limited funds. D represents the shoot-through duty ratio of the inverter switches which can range from 0

Herein, we propose a novel three-phase quasi-Z-source inverter with a high voltage transmission ratio to address challenges such as high switching loss and sizeable magnetic components in the basic quasi-Z-source inverter. The proposed circuit topology, control strategy, and related analysis are presented. The circuit topology of the inverter comprises a quasi-Z-source network with an integrated magnetic inductor, an active clamp circuit, a three-phase inverter bridge, and an output LC filter, all of which are connected in series. An improved 12-sector space vector modulation scheme is proposed based on the root-mean-square value of the voltage and the instantaneous value of the current. Furthermore, analyses of the inverter voltage transmission ratio, resonant process, and parametric design guidelines for integrated magnetic inductor and zero-voltage switching conditions are presented. Experimental results on a 1-kVA prototype inverter demonstrate that the proposed inverter exhibits a higher transmission ratio and efficiency than existing inverters; thus, the proposed inverter would have broad prospects in low-voltage DC-AC applications. [ABSTRACT FROM AUTHOR]

Nowadays, renewable energy sources such as solar Photovoltaic (PV) and wind power systems play a significant part in the process of generating electricity. These systems are tremendously reliant on the present and forecasted weather conditions. The inconsistent behavior of the system has an impact on the production as well as the variances in the output. As a result, the requirement for energy transmission and distribution systems to compensate promptly is becoming crucial. This paper proposes a new smart grid application for power system operation. A Static Compensator (STATCOM) device is utilized to improve the power quality and power flow in the distribution system, reduce unwanted harmonics and compensate for reactive power in the power sources. A quasi-Z-Source Inverter (qZSI) based STATCOM is constructed in connection with a Three-Phase Four-Wire (3P4W) distribution system. The combination of a q Z-source and a PV system makes up the suggested compensator circuit that is employed here for switching. To control the suggested compensator, an Adaptive Frequency Fixed (AFF) - Second Order Generalized Integrator (SOGI) has been implemented. The Fuzzy Logic Controller (FLC) is used to optimize the parameters of the Proportional Integral (PI) controller, such as $K\text{p}$ and $K\text{i}$ . The experimental results demonstrate that the system effectively reduces the Total Harmonic Distortion (THD) of the source current, decreasing it from 25.5% to 1.3%. Moreover, the system has demonstrated its ability to supply active power to the load.

Single-phase inverters are widely employed in renewable energy applications. However, their inherent 2ω-ripple power can substantially affect system performance, leading to fluctuations in the maximum power points (MPP) of photovoltaic (PV) systems and shortening the lifespans of fuel cell (FC) systems. To alleviate input ripple, a three-leg quasi-Z-source inverter (QZSI) and its associated control strategy are proposed. The QZSI consists of a quasi-Z-source network, an H-Bridge inverter, and an active power filter (APF). The active filtering structure comprises filtering capacitors and the third bridge leg. The proposed control strategy consists of three loops: open-loop simple boost control, output voltage control, and 2ω-ripple suppression control. Open-loop simple boost control is utilized for shoot-through state modulation, output voltage control is applied to the two bridge-legs of the H-Bridge, and the additional third bridge-leg adopts a quasi-PR control (QPR) method that injects specific frequency harmonic voltage and suppresses newly generated low-frequency components of the input current. This method effectively avoids the drawbacks of utilizing passive filtering strategies, such as high-value impedance networks, low power density, and weak system stability. A simulation platform of 300W 144VDC/110VAC50Hz is constructed. The simulation results indicate that the addition of the third bridge leg under full load conditions reduces the input-side inductor current ripple ΔI from 1.89 A with passive filtering to 0.513 A, representing a reduction of 72.86%. The second harmonic ripple of the input current is reduced from 18.2% to 4.5%, and the fourth harmonic ripple is reduced from 16.5% to 2.1%. The DC bus voltage ripple ΔVPN falls from 70.75 V to 6.54 V, representing a reduction of 90.76%. The Total Harmonic Distortion (THD) of the output voltage and current are both less than 1%. The simulation results validated the feasibility of the proposed approach. [ABSTRACT FROM AUTHOR]

In recent years, the traditional power inverter systems have been replaced by the modern impedance source inverter (ZSI) circuit topology which became highly popular due to many benefits such as voltage boosting ability, reduced cost, flexibility, and, less sensitivity to electromagnetic noises. This paper presents an improved single-phase quasi-Z-source inverter (qZSI) circuit model. The input inductor of the qZSI circuit has been replaced by a switched-inductor (SL) configuration which is integrated into DC power source and impedance network. The proposed circuit can make use of the stored DC power with the help of the SL form within the shoot-through time interval. In comparison with the conventional qZSI topology, the proposed model increases the boost factor of the qZSI circuit significantly for the same shoot-through time. In addition to that, the circuit draws continuous input current and shares common ground with DC power source. The operation principle is analyzed with the help of the mathematical equations and simulations are carried out using Matlab/Simulink environment. A laboratory prototype is realized to validate the proposed circuit. Simulation and experimental results are presented to illustrate the performance of the proposed inverter topology. The presented circuit model is open to new developments and can be used for low power applications such as photovoltaic (PV) and fuel cell systems. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid renewable energy system (RES) including wind and photovoltaic (PV) power sources. The wind energy subsystem (WES) consists of a squirrel-cage induction generator (SCIG) driven by a variable-speed wind turbine (WT) and corresponding power electronic converter, by means of which a speed-sensorless indirect-rotor-field-oriented control of the SCIG is implemented. The outputs of both the WES and PV power source rated 1.5 kW and 3.5 kW, respectively, are connected to the DC bus, with the quasi-Z-source inverter (qZSI) acting as an interlinking converter between the DC bus and the AC grid/load. An advanced pulse-width-modulation scheme is applied to reduce the qZSI switching losses. The considered RES can operate both in grid-tie and island operation, whereas the battery storage system—integrated within the qZSI impedance network—enables more efficient energy management. The proposed control scheme includes successively executed algorithms for the optimization of the WES and PV power outputs under varying atmospheric conditions. A perturb-and-observe PV optimization algorithm is executed first due to the significantly faster dynamics and higher-rated power of the PV source compared to the WES. The WES optimization algorithm includes two distinct fuzzy logic optimizations: one for extraction of the maximum wind power and the other for minimization of the SCIG losses. To reduce the number of the required sensors, all three MPPT algorithms utilize the same input variable—the qZSI's input power—thus increasing the system's reliability and reducing the cost of implementation. The performance of the proposed hybrid RES was experimentally evaluated over wide ranges of simulated atmospheric conditions in both the island and grid-tie operation. [ABSTRACT FROM AUTHOR]

In this manuscript, a proficient control strategy-based improved Quasi-Z-Source Cascaded Multilevel Inverter (QZS-CMI) topology for interfacing photovoltaic (PV) system is proposed. The control strategy is joint execution of both recalling-enhanced recurrent neural network (RERNN) and Shell Game Optimization (SGO), therefore it is called RERNN-SGO technique. The major intention of proposed system determined the photovoltaic system efficiency and maximize the power extraction. The interface among load and PV dc source is to accomplish by the QZSI. At first, the objective function is determined depending on the control constraint and parameters, like current, voltage, modulation index, power. These parameters are utilized to propose RERNN-SGO method. The RERNN-SGO method is used to improve the power delivery, voltage profile and minimum power oscillation for power distribution with load. The maximal power delivered the load is to ensure the artificial intelligence (AI) strategy with the help of maximal power point tracking (MPPT). To regulate shoot through duty ratio and modulation load, the proposed AI method is used. The proposed system is inspired on MATLAB/Simulink site, and then efficiency is related with existing systems under various load conditions. The efficiency of proposed system in Case 1 and Case 2 is 87.363% and 85.3904%. [ABSTRACT FROM AUTHOR]

This paper proposes a proportional resonant and proportional integral based control strategy for single phase quasi-Z-source inverters (qZSIs) which is able to operate in buck and boost modes. Switching signals of the qZS inverters can be generalized as shoot through and non-shoot through states. The DC-link voltage of the qZSIs can be controlled by generating proper shoot through signals. The control strategy for qZSIs should be able to control both DC and AC-sides at the same time. First, the average state–space model of qZSI is obtained for closed loop control in this paper. Thereafter, the proportional resonant control is designed to achieve AC-side voltage control. Also, voltage control of DC-side capacitor is achieved by using proportional integral control method. Finally, the switching signals are obtained by applying the control outputs to modulation strategy. Experimental results are presented to demonstrate the effectiveness of the control method. The results verify that the proposed control strategy successfully regulates both DC and AC-side control variables.

This paper proposes a novel topology, named a single-phase active switched-capacitor embedded quasi-Z-source inverter (ASC-EqZSI), and two pulse-width modulation (PWM) methods, namely, PWM1 and PWM2 methods for the proposed ASC-EqZSI topology to improve the boost capability and reduce switching loss. The boost capability can be improved by using an additional non-shoot-through (NST) state, referred to as the NST2 state, besides conventional shoot-through (ST) and NST states. In the NST2 state, the switch in the impedance network is switched on to boost the dc-link voltage while generating the ac output voltage. A PWM1 method is suggested to control both the NST2 and ST time intervals with one carrier signal for improving the boost capability. A PWM2 method aims to reduce the commutation count of the switches and diodes in the proposed topology while maintaining the enhanced boost capability. The switching loss can be reduced by almost 40%. A comparative analysis between the proposed topology with the PWM2 method and five other topologies with an active switched Z-network is performed. The proposed topology with the PWM2 method has a higher ac voltage gain and efficiency with fewer components. Simulation and experimental results are carried out to validate the performances of the proposed topology and PWM methods.

Grid-connected inverter-based photovoltaic (PV) systems play an important role in Distributed Power Generation (DPG). For this application, quasi impedance source inverter is very suitable due to its ability to increase or decrease the output voltage of the inverter in a single-stage and high reliable condition. Conventionally, to remove the harmonics, which are yielded by switching the grid-connected inverter, LCL filters are utilized at the inverter output. These filters can cause some problems at the Point of Common Coupling (PCC). The aim of this paper is to improve the quality of the injected power of the photovoltaic array, which is connected to the low voltage grid by quasi-Z-source inverter (QZSI). For this purpose, a two-stage control procedure containing DC and AC stages is performed. In the DC stage, the dynamic characteristics of the quasi-Z-source network are investigated by small-signal analysis. Using the transfer functions obtained from the dynamic model, the capacitor voltage of the quasi-Z-source network is suitably controlled to generate the appropriate voltage to the grid interface inverter. In the AC stage, in order to inject high-quality current into the grid as well as eliminating the resonance peak caused by the LCL filter, a systematic procedure is used to design the PR controller parameters and active damping coefficient. Simulation of the overall system includes solar panels, maximum power point tracking algorithm, quasi-Z-source inverter, and LCL filter to model the grid-tied PV system with the possible details. Simulations are carried out in MATLAB/Simulink environment, and results depict suitable performance of the studied power conditioning system with designed parameters.

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In this paper, a battery pack and a supercapacitor bank hybrid energy storage system (HESS) with a new control configuration is proposed for electric vehicles (EVs). A bidirectional quasi-Z-source inverter (Bq-ZSI) and a bidirectional DC-DC converter are used in the powertrain of the EV. The scheme of the control for the proposed HESS Bq-ZSI using finite control set model predictive control (FCS-MPC) is first deduced to enhance the dynamic performance. With the idea of managing battery degradation mitigation, the fractional-order PI (FOPI) controller is then applied and associated with a filtering technique. The Opal-RT-based real-time simulation is next executed to verify the performance and effectiveness of the proposed HESS control strategy. As a result, the proposed HESS Bq-ZSI with this control scheme provides a quick response to the mechanical load and stable DC link voltage under the studied driving cycle. Moreover, the comparative results also show that the proposed HESS Bq-ZSI equipped with the new control configuration enables the reduction of the root-mean-square value, the mean value, and the standard deviation by 57%, 59%, and 27%, respectively, of the battery current compared to the battery-based inverter. Thus, the proposed HESS Bq-ZSI using these types of controllers can help to improve the EV system performance. [ABSTRACT FROM AUTHOR]

Typically, permanent magnet synchronous generator (PMSG)-driven wind turbines (WTs) present a two-stage power converter topology based on a DC/DC boost converter and voltage source inverter. In this study, this configuration is substituted by a quasi-Z-source inverter (qZSI), which is an attractive solution for boosting and converting the voltage from DC to AC in a single stage. A 2 MW PMSG WT with qZSI was studied herein. A switched dynamic model (SDM) of the qZSI (including the modeling of all switches and firing pulses) is not recommended for steady-state stability studies, long-term simulations, or large electric power systems. For such studies, two averaged dynamic models are proposed in this work. Both models present the same control system as the SDM, except for the generation of firing pulses, which is not necessary in the averaged models. The two proposed models were evaluated and compared with the SDM in the large-scale WT under different operating conditions, such as wind speed fluctuations, variable power references, and grid disturbances (voltage sag and 3rd and 5th order harmonics injection), in order to demonstrate their adequacy to represent the system response with a high reduction in the simulation time and computational efforts.

In this study, single phase quasi-Z-source inverter (QZSI) circuit was designed and realized which is an improved version of ZSI and offers a unique power conversion concept by eliminating the conceptual and theoretical limitations of the conventional current and voltage source inverters. Simple boost PWM control technique has been employed to the switches using NUCLEO-F411RE development board since this technique doesn't involve low-frequency ripples on the passive components of the impedance network and has lower distortions at the output. It has been shown that the developed QZSI circuit can work as a buck-boost converter at different shoot-through duty ratios. At the output of the circuit up to 300W, the AC output voltage is obtained with 85% efficiency. It has been observed that simulation and experimental results carried out in the laboratory environment are compatible. [ABSTRACT FROM AUTHOR]

Low voltage stress on the impedance source network devices is the main reason for the advent of DC-linked type quasi-switched boost inverters (DqSBIs). However, the DqSBI has become less attractive due to its low voltage gain. This paper presents a novel PWM control strategy for the DqSBI and its comparative performance evaluation to the conventional inverters. The modified PWM control strategy based DqSBI improves the voltage gain and reduces the conduction loss and the inductor current ripple. Circuit analysis and comparison study between the DqSBI, the quasi-Z-source inverters, and the two-stage inverter with a boost DC-DC converter are presented. 1-kVA three-phase inverter prototypes were set up to compare and evaluate the performance of the DqSBI with the improved PWM method for voltage gains of 0.85 to 1.6. The measured efficiency and total harmonic distortion (THD) values are also presented.

In this paper, a battery pack and a supercapacitor bank hybrid energy storage system (HESS) with a new control configuration is proposed for electric vehicles (EVs). A bidirectional quasi-Z-source inverter (Bq-ZSI) and a bidirectional DC-DC converter are used in the powertrain of the EV. The scheme of the control for the proposed HESS Bq-ZSI using finite control set model predictive control (FCS-MPC) is first deduced to enhance the dynamic performance. With the idea of managing battery degradation mitigation, the fractional-order PI (FOPI) controller is then applied and associated with a filtering technique. The Opal-RT-based real-time simulation is next executed to verify the performance and effectiveness of the proposed HESS control strategy. As a result, the proposed HESS Bq-ZSI with this control scheme provides a quick response to the mechanical load and stable DC link voltage under the studied driving cycle. Moreover, the comparative results also show that the proposed HESS Bq-ZSI equipped with the new control configuration enables the reduction of the root-mean-square value, the mean value, and the standard deviation by 57%, 59%, and 27%, respectively, of the battery current compared to the battery-based inverter. Thus, the proposed HESS Bq-ZSI using these types of controllers can help to improve the EV system performance.

This Editorial summarizes the papers of the Special Issue entitled ‘Advanced Control Techniques for Wind/Solar/Battery Systems’ published in Energies. The Special Issue includes four scientific articles published in 2021 and 2022 in the field of quasi-Z-Source inverter control, photovoltaic energy conversion, battery charge control, wind turbine speed control, and solar irradiance prediction. New scientific achievements with experimental verifications of the achieved results are presented in all articles.

The accurate estimation of rotor position and speed before flying restart is of great significance to improve the operation reliability of permanent magnet synchronous motor systems. The traditional multizero vector short-circuit method can improve the estimation accuracy of speed and rotor position, but the increased number of short-circuits reduces the electromagnetic torque response speed after the power supply recovers. In order to accurately estimate the initial speed and rotor position before the flying restart and effectively improve the electromagnetic torque response speed, a shoot-through zero vector short-circuit method based on quasi-Z-source inverter (qZSI) is proposed. This method breaks the limitation of regulating DC link voltage under the normal operation of the motor in the conventional methods, and puts forward a new idea of advancing the regulation of the DC link voltage to the stage of abnormal operation before the motor restarts. By designing the insertion mode of the mixed vectors and analyzing the action time of each vector before the flying restart, the accurate estimation of position and speed is realized and, meanwhile, the boost of the qZSI’s DC link voltage is achieved, thus giving the sensorless flying restart method a faster torque response speed for the PMSM system driven by qZSIs.

Summary: Battery energy stored single‐phase quasi‐Z‐source inverter photovoltaic (BES‐qZSI‐PV) power system shows many advantages in comparison with other tri‐port inverter‐based PV power systems. However, the existing BES‐qZSI‐PV power system does not work at night or cloudy day because of its circuit limitation. This paper proposes a 24‐h operational BES‐qZS‐PV system by the following approaches: (1) the main power circuit is proposed for the day and night operation; (2) the detailed circuit models including the DC model and the second‐harmonics ripple model are built by considering scenarios of day and night operations; (3) the design method of quasi‐Z‐source network parameters is proposed to meet the requirement of day and night operations; and (4) the control strategy is proposed to achieve the high‐performance system operation all the time and seamless transition between day and night operation. After theoretical modeling and analysis, the built models are verified by comparing their calculation results with the circuit‐based simulation and experimental results. The proposed single‐phase BES‐qZSI‐PV power system is tested; experimental and simulation results are captured when the system operates in day, night, and transition to validate the proposed 24‐h operational BES‐qZSI‐PV system. [ABSTRACT FROM AUTHOR]

A common mode voltage (CMV) reduction method is proposed for the active power filter (APF) integrated single-phase quasi-Z-source inverter (qZSI) based photovoltaic (PV) power system. The APF integrated qZSI completely compensates the dc-side double-line-frequency (2ω) ripple through the APF capacitor, while maintaining low qZS inductance and capacitance. The proposed method reduces the CMV amplitude to half of that using the traditional sinusoidal pulse width modulation (SPWM). The switching and conduction power losses are analyzed. Simulation and experimental results demonstrate the proposed method reduces CMV without comprising performance and efficiency of the APF integrated single-phase qZSI.

The promising quasi-Z-Source inverter (qZSI) can regulate the DC-link voltage. In the study, a permanent magnet synchronous motor (PMSM) drive system is established with the qZSI. Based on the small-signal model, a feedback and feedforward compound control strategy is proposed and the dynamic performance of the converter is analyzed. The simulation and experimental results indicate that the compound control strategy effectively improves the static and dynamic characteristics of the DC-link voltage and reduces the influence of power variation on the DC-link voltage.

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Summary: Pulse width‐amplitude modulation (PWAM) have been widely used in recent years to mitigate switching losses as well as reducing passive components' size. This paper precisely investigates this modulation approach in quasi‐Z‐source inverters (qZSI). It will be concluded that the existence of capacitive paths from load to source in such converters causes two undesired behaviors while utilizing PWAM, which increases total harmonic distortion and semiconductor stresses. Bypassing the capacitive paths is proposed in this paper to alleviate these issues. In order to implement this approach, a bidirectional quasi‐Z‐source inverter is studied. A design procedure is presented to achieve a fast dynamic response for tracking reference voltage. The operation of both conventional and bidirectional qZSI under different loads including resistive and resistive–inductive loads is investigated in the simulation and experiment. According to experimental results, by utilizing bidirectional qZSI, THD is improved from 12.34% to 3.51% for a lag load. Moreover, the voltage stress of the semiconductor no longer exists. [ABSTRACT FROM AUTHOR]

This paper presents a novel strategy to indirectly control the peak dc-link voltage (PDV) of grid-connected quasi-Z-source (qZS) inverter supplied with renewable energy sources (RES). The method is directed to indirectly determine and regulate the pulsating PDV through the qZS network capacitor voltages. The small signal model is developed by representing ac- and dc-sides separately. The ac-side control is designed with higher bandwidth to avoid interference from dc-side. The dc-side control utilizes shoot-through duty ratio to PDV transfer function and controller is designed to minimize the effect of its right-half-plane zero (RHPZ) characteristics. The gating signals are realized through maximum constant boost control in conjunction with one-sixth of third harmonic injection. The strategy is implemented through MATLAB/Simulink and is verified experimentally with real-time simulations (RTSs) in OPAL-RT. [ABSTRACT FROM AUTHOR]

This paper deals with a photovoltaic (PV) system containing a quasi-Z-source inverter (qZSI) and batteries connected in parallel with the qZSI’s lower-voltage capacitor. The control system design is based on knowledge of three transfer functions which are obtained from the novel small-signal model of the considered system. The transfer function from the d-axis grid current to the battery current has been identified for the first time in this study for the considered system configuration and has been utilized for the design of the battery current control loop for the grid-tied operation. The transfer function from the duty cycle to the PV source voltage has been utilized for the design of the PV source voltage control loop. The PV source voltage is controlled so as to ensure the desired power production of the PV source. For the maximum power point tracking, a perturb-and-observe algorithm is utilized that does not require the measurement of the PV source current, but it instead utilizes the battery current during the stand-alone operation and the d-axis reference current during the grid-tied operation. The corresponding tracking period was determined by using the transfer function from the duty cycle to the battery current and in accordance with the longest settling time noted in the corresponding step response. The proposed control algorithm also has integrated protection against battery overcharging during the stand-alone operation. The considered system has been experimentally tested over wide ranges of irradiance and PV panel temperature.

A wavelet modulation strategy applied to a quasi-Z-source inverter was proposed. The regulating range of the shootthrough duty ratio could be increased by changing the locations of the sampling points set using traditional wavelet-modulation. The proposed modulation strategy divided the shoot-through zero vector into two portions, which were then individually inserted into both ends of the sampling time. Under the proposed strategy, the quasi-Z-source inverter could obtain a theoretical maximum constant shoot-through duty ratio without any extra switching frequencies. In addition, the proposed strategy was compared with traditional modulation strategies used in quasi-Z-source inverters. The boosting capacity, efficiency, harmonic and modulation ratio of the different modulation strategies for quasi-Z-source inverter were analyzed thoroughly. Finally, the performance of the proposed method was verified by simulation. Both the simulation results and theory verify that the strategy can reduce harmonic, increase voltage utilization rate, and enhance the boosting capacity.

Photovoltaic (PV) power systems are increasingly being used as renewable power generation sources. Quasi-Z-source inverters (qZSI) are a recent, high-potential technology that can be used to integrate PV power systems into AC networks. Simultaneously, concerns regarding the stability of PV power systems are increasing. Converters reduce the damping of grid-connected converter systems, leading to instability. Several studies have analyzed the stability and dynamics of qZSI, although the characterization of qZSI-PV system dynamics in order to study transient interactions and stability has not yet been properly completed. This paper contributes a small-signal, state-space-averaged model of qZSI-PV systems in order to study these issues. The model is also applied to investigate the stability of PV power systems by analyzing the influence of system parameters. Moreover, solutions to mitigate the instabilities are proposed and the stability is verified using PSCAD time domain simulations.

A quasi-Z-source inverter (qZSI) is a single-stage inverter that enables a boost of the input dc voltage through the utilization of a so-called shoot-through state (STS). Generally, the efficiency of the qZSI depends on the utilized STS injection method to a significant extent. This paper presents a novel method of STS injection, called the zero-sync method, in which the STS occurrence is synchronized with the beginning of the zero switching states (ZSSs) of the three-phase sinusoidal pulse width modulation (SPWM). In this way, compared to the conventional STS injection method, the total number of switchings per transistor is reduced. The ZSSs are detected by utilizing the SPWM pulses and the logic OR gates. The desired duration of the STS is implemented by utilizing the LM555CN timer. The laboratory setup of the three-phase qZSI in the stand-alone operation mode was built to compare the proposed zero-sync method with the conventional STS injection method. The comparison was carried out for different values of the switching frequency, input voltage, duty ratio, and load power. As a result of the implementation of the zero-sync method, the qZSI efficiency was increased by up to 4%. In addition, the unintended STSs, caused by the non-ideal switching dynamics of the involved transistors, were successfully eliminated by introducing the optimal dead-time as part of the modified zero-sync method. As a result, the efficiency was increased by up to 12% with regard to the conventional method.

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper proposes a bipolar quasi-Z-source active neutral point clamped inverter (QZS-ANPCI) topology. It acts as a buck/boost inverter (3-phase, 3-level) to integrate renewable energy resources under their fluctuating DC voltages. We propose a symmetrical/unsymmetrical boost modulation control technique to mitigate the DC-link unbalance voltage problem in an ANPC inverter. This worthwhile control technique exploits voltage-current closedloops on AC and DC sides to regulate the desired parameters. Moreover, the constant boost control (CBC) modulation has provided a switching sequence that generates a symmetrical/unsymmetrical full shoot-through (FST) state for boosting input DC voltage in the proposed inverter. Detailed loss and efficiency analysis is carried out to show its superior performance under the proposed scheme. Furthermore, the total harmonic distortion (THD) of the proposed QZS-ANPCI meets IEEE Standard-519. Simulink/MATLAB (MathWorks, USA) and PSIM (Powersim, USA) software programs are used to simulate the proposed topology. To verify the theoretical proposals and simulation results, we have developed an experimental prototype setup (1 kW). Both simulation results and experimental data show satisfactory agreement and support the theoretical postulates. [ABSTRACT FROM AUTHOR]