Traditional Z-source Inverter Research Articles

Performance Evaluation of Various Z-Source Inverter Topologies for PV Applications Using AI-Based MPPT Techniques

Recent research has been focussed on renewable energy due to the rising need for electrical energy. Renewable energy has a low environmental impact compared to other energy sources. As a result, renewable energy sources (RESs) are the best option for generating electricity. Solar photovoltaic is one of the largest renewable power generators. Solar photovoltaic (PV) is connected to the load via power electronic converters. Most PV installations need a two-stage conversion process consisting of a boost converter to increase the load voltage and an AC-to-DC voltage source inverter to power the load. The Z-source inverter (ZSI) can confront the shortcomings of VSI and two-stage conversions. ZSI connects the PV system to the load and is used to increase the system’s performance. This paper discusses the performance of various topologies of ZSI, such as traditional Z-source inverters (XZSIs); for integrating a PV source into a load, switched inductor Z-source inverters (SIZSIs) and transient Z-source inverters (TZSIs) are used. Also, artificial neural networks (ANNs), fuzzy logic controller (FLC), and adaptive neuro-fuzzy inference system (ANFIS)-based MPPT techniques are discussed for obtaining maximum power from PV panels. Based on the maximum power, the shoot-through duty ratio has been adjusted.

A QUASI-Z-SOURCE Converter Using a Single-Stage Switched-Inductor Boost DC-DC Converter

Abstract: This paper introduces a new topology, yet simple and efficient, for a grid-connected wind-solar cogeneration system. A permanent magnet synchronous generator-based full-scale wind turbine is interconnected to the utility grid. The dc-link capacitor has been utilized to directly interface a photovoltaic solar generator. No dc/dc conversion stages are required, and hence, the hybrid system is simple and efficient. Moreover, the proposed topology features an independent maximum power point tracking for both the wind and the solar generators to maximize the extraction of renewable energy. This paper presents a quasiZ-source inverter (qZSI) that is a new topology derived from the traditional Z-source inverter (ZSI). The qZSI inherits all the advantages of the ZSI, which can realize buck/boost, inversion and power conditioning in a single stage with improved reliability. In addition, the proposed qZSI has the unique advantages of lower component ratings and constant dc current from the source. All of the boost control methods that have been developed for the ZSI can be used by the qZSI. One of the more commonly used techniques is the incremental conductance method. In this paper, an improved particle swarm optimization- (IPSO-) based MPPT technique for photovoltaic system operating under varying environmental conditions is proposed. Basically, an Artificial Neural Network (ANN) based approach is utilized to automatically detect the global maximum power point of the PV array by using a preselected number of power measurements of the PV system. The approach of linearly decreasing scheme for weighting factors and cognitive and social parameters is modified. The proposed control scheme can overcome deficiency and accelerate convergence of the IPSO-based MPPT algorithm. Detailed small-signal models for the system components are developed to characterize the overall stability. The influence of the utility-grid faults on the performance of the proposed system is also investigated. Nonlinear time-domain simulation results under different operating conditions are presented to validate the effectiveness of the proposed topology.

A Family of High Step-Up Quasi Z-Source Inverters with Coupled Inductor

With the continuous development of new energy, there is more and more research on step-up inverters in photovoltaic and wind power generation systems. The Z-source inverter has become a research hotspot because of its small output THD (Total Harmonic Distortion) and high reliability. However, the traditional Z-source inverters cannot meet the higher boost requirements of new energy power generation. The quasi-z-source inverter with stronger boosting ability came into being. The high step-up Z-source inverters presented in existing literature is only focused on one or several topologies and lacks a comparative analysis on different topologies. Based on the quasi-Z-source inverter, this paper proposes a family of quasi-z-source inverters with a coupled inductor. The required voltage gain can be obtained by changing the turns ratio of the coupled inductor, which provides a new control variable for the system and makes the design of the system becomes more flexible. Through the analysis and comparison of each topology in terms of boost capacity, voltage stress, coupled inductor volume, circuit efficiency, and input ripple, the characteristics of each topology are summarized. The representative topology was simulated and analyzed, and a 1 kVA prototype was developed in the laboratory to verify the correctness of the theoretical analysis.

LC‐Z‐Source Inverter Design and Control

The paper presents a new Z-source inverter with a low-stress reduction in the voltage of capacitors compared to the traditional Z-source inverter with the same boost factor. The proposed structure reduces costs and weight by reducing voltage capacitors. The main difference between this inverter and the traditional Z-source inverter lies in the arrangement of the components. In addition, the superiority of the proposed inverter over the L-Z-source inverter is related to the use of two capacitors instead of two diodes, which increases the boost power factor and obviates the need for the snubber circuit. Furthermore, another advantage of the proposed inverter can be extended to n cases in cascade form and the proposed inverter is continues current. The analysis, derivation of boost factor, capacitor voltages, voltages gain, and switch stress of the proposed inverter topology are carried out and are compared with the similar inverters. The advantages of the proposed structure are verified by simulation and implementation.

Improved Topology of Quasi - Z - Source Inverter and Its Grid-Connected Control

In order to solve the problems of low voltage boost capability, high capacitance voltage stress, narrow voltage boost range and small gain of traditional z-source inverters, a new topology structure of quasi-Z source cascade H-bridge multilevel inverters is proposed. The simulation was verified by MATLAB/SIMULINK software and compared with other Z source topologies. The results show that the new topology makes up for the problems of insufficient voltage boost capacity and narrow voltage boost range of the traditional Z source inverter, and the output power is high when the inverter is connected to the grid.

Series-type switched-inductor Z-source inverter

To solve the disadvantages of the traditional Z-source inverter (ZSI), this paper investigates a series-type switched-inductor Z-source inverter (SSI-ZSI) topology. It not only preserves the advantages of the traditional ZSI, but also improves the voltage gain. On the condition of the same voltage gain, the capacitor voltage stress is reduced, the soft start characteristic can be achieved and the inverter can be immune to the damage of the inrush current. The circuit structure and operating principle are analyzed in detail; the simulation model and the experimental platform are built. The simulation and experimental results verify the rationality and superiority of the circuit topology.

Improvement in Performance of Series Z-Source Inverter with an Application as Solar PV Fed Water Pump

For a stand-alone solar pump, Z-source inverter (ZSI) is being preferred because of its single-stage power conversion capability with buck-boost ability. As compared to traditional ZSI, series Z-source inverter (SZSI) reduces the voltage stress on capacitor and inrush current of the inductor significantly. In this paper, modes of operation of the SZSI for an induction motor load are explained. When an induction motor runs at a low power factor, an additional mode exists. In this mode, high-magnitude pulses appear on the DC link voltage if the decoupling capacitor is not used with an unidirectional source like solar photovoltaic (PV). In addition, an improved modulation technique is proposed to improve the performance of SZSI. This paper presents a performance of SZSI with solar photovoltaic as a source and an induction motor coupled with the centrifugal pump as a load. Simulation results show the performance of the proposed scheme. Experimental and simulation results demonstrate the validity of analysis. Therefore, SZSI is a promising topology for the solar PV stand-alone system.

Single-Phase Three-Level Neutral-Point-Clamped Inverter Based on Modified Z-Source Network With Reduced Voltage Stress on Capacitors

This article presents a new topology for single-phase three-level neutral-point-clamped inverter. The proposed topology uses a modified Z-source network that for the same boost factor has lower voltage stress across the capacitors in comparison to the traditional Z-source inverters. Therefore, this topology leads to a lower capacitor size as well as decreased cost. In this article, the different operating modes of the proposed inverter in steady-state are analyzed. Moreover, voltage stress across capacitors, voltage ripple of capacitors, and current ripple of inductors are calculated using dc and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\omega $ </tex-math></inline-formula> components analyses. Then, the proper values of inductors and capacitors are designed. The proposed inverter is compared with the traditional inverter topologies to show its advantages and disadvantages. The effectiveness of the proposed inverter is tested by using a laboratory-built prototype and simulation under MATLAB/Simulink environment.

Analysis of Steady-State Characteristics for a Newly Designed High Voltage Gain Switched Inductor Z-Source Inverter

This paper aims to develop a new switched inductor assisted strong boost Z-source inverter (SL-SBZSI) topology with high voltage gain and analyze the steady-state characteristics of the proposed topology. In the proposed topology, two switched inductors are used within the series impedance structure of the Z-source inverter (ZSI) in order to achieve the high voltage gain. The steady-state characteristics of the proposed topology are analyzed to disseminate its several advantages as compared to traditional ZSIs. The key advantages include the higher boost factor with lower shoot-through duty ratio and lower voltage stresses on capacitors as well as on switches of the inverter bridge. Furthermore, the proposed topology has the soft-start ability which significantly reduces the inrush start-up current while comparing with the traditional ZSI. In the proposed topology, a common ground is shared between the output AC voltage and the input DC voltage source which categorizes this topology to the doubly grounded inverter. The characteristics of the proposed SL-SBZSI are analyzed by considering two operating condition where the simple boost pulse width modulation (PWM) scheme is used to extract the shoot-through pulses. The characteristics of the proposed topology are also compared with different existing topologies along with the conventional modified capacitor assisted Z-source inverter (MCA-ZSI), whose boost factor is much closer to the proposed topology. Rigorous mathematical analyses are presented to clearly demonstrate the benefits of the proposed topology while simulation studies are carried out to demonstrate its distinct features as compared to the existing topology. Finally, experimental studies are conducted to further validate the theoretical and simulation results.

Variable damping injection control of PMSM drive systems based on isolated shoot‐through Z‐source inverter

This study proposes a novel permanent magnet synchronous motor (PMSM) driven system based on isolated shoot-through Z-source inverter (IST-ZSI). The IST-ZSI is utilised to replace the traditional Z-source inverter. Compared with the conventional Z-source inverter-based PMSM drive system, the new drive system can not only solve the coupling of the boost factor and modulation but also provide a large regulation range of the output voltage. For the PMSM drive system, a variable damping injection controller is proposed via the passivity-based control and maximum torque per ampere control principle. Then, the load torque observer is designed to improve the stability of the PMSM system with uncertain load torque. The simulation and experimental results show that the variable damping injection control has satisfactory dynamic and static control performance.

Comparative analysis of a novel topology for single-phase Z-source inverter with reduced number of switches

Z-source inverter has recently been introduced to overcome the limitations of conventional voltage source inverter. This paper deals with a novel topology of single-phase Z-source inverter (ZSI). This topology reduced the number of passive elements and active switches in order to make the inverter cheaper and smaller in size compared to traditional ZSI. Detailed analysis of the proposed topology is presented in this paper which includes calculations of boost factor, total harmonic disorder, magnitude of output voltage etc. Modulation technique used to control the switching of the proposed inverter is explained in detail. This paper also compares the proposed topology with conventional topologies of Z-source inverter. Simulation results of MATLAB and real-time simulators are shown to explain the working of the proposed topology.

Switched-Boost-Modified Z-Source Inverter Topologies With Improved Voltage Gain Capability

This paper presents three-phase switched-boost-modified Z-source inverter (ZSI) topologies with improved boost capabilities. In the proposed ZSIs, the voltage gain is increased significantly by adding one auxiliary switch and one diode without using additional passive components. The concept is applied to traditional ZSI, discontinuous input current quasi-ZSI (DC-qZSI), and continuous input current qZSI (CC-qZSI) resulting into three new inverter topologies: switched-boost ZSI, DC-qZSI, and CC-qZSI. Anatomization of operating principle, steady-state analysis, voltage gain, voltage stress, current stress, stored energy analysis, power loss, total harmonic distortion, and efficiency analysis are carried out to highlight the advantages of the proposed inverters as compared to the conventional ZSIs. Finally, the operation of the proposed CC-qZSI is validated through simulation and experimental results.

A comparative study of Z-source inverter and enhanced topologies

This paper does some theoretical analysis and simulation studies on the most common topologies of Z-source inverter. As we all know, the traditional Z-source inverter has some problems, such as the voltage of the capacitor which belongs to this topology is higher and there is a startup shock, which caused researchers proposed a variety of improved Z-source topologies to solve these problems. Some of these topologies can increase boost capacity, and some can reduce the capacitor voltage. However, these topologies can improve only part of the problems of the traditional Z-source inverter, which leads to that the users are hard to choose which topologies. Faced with this situation, eleven Z-source topologies are analyzed in terms of boost capacity, inductance start-up current, capacitance stress and economy in this paper. Finally, two kinds of promising topologies were gotten.

A Modified Single-Phase Transformerless Z-Source Photovoltaic Grid-Connected Inverter

In a grid-connected photovoltaic (PV) system, the traditional Z-source inverter uses a low frequency transformer to ensure galvanic isolation between the grid and the PV system. In order to combine the advantages of both Z-source inverters and transformerless PV inverters, this paper presents a modified single-phase transformerless Z-source PV grid-connected inverter and a corresponding PWM strategy to eliminate the ground leakage current. By utilizing two reversed-biased diodes, the path for the leakage current is blocked during the shoot-through state. Meanwhile, by turning off an additional switch, the PV array is decoupled from the grid during the freewheeling state. In this paper, the operation principle, PWM strategy and common-mode (CM) characteristic of the modified transformerless Z-source inverter are illustrated. Furthermore, the influence of the junction capacitances of the power switches is analyzed in detail. The total losses of the main electrical components are evaluated and compared. Finally, a theoretical analysis is presented and corroborated by experimental results from a 1-kW laboratory prototype.

Control of Industrial Drives through Multicell Impedance Source Inverter

In this paper, various power quality issues that occur while driving an industrial motor drive such as voltage sag, swell, interruptions are discussed. A solution for such issues is proposed drives during various conditions of power quality issues is discussed in detail and a comparison with traditional Z-source inverter is made. The results are validated for mathematically modelled using Multicell Z-source inverter. By controlling shoot-through duty cycle using various techniques such as Simple boost control, Maximum boost control, constant boost control these issues are addressed. Multicell Z-source inverter has come as a replacement for traditional Z-source inverter due to its less EMI noise; increased voltage level with increase in cell as well as reduced voltage stress makes it more advantages than traditional one. In this paper, control of industrial system of 3 kW induction drive in MATLAB/Simulink environment and the results are summarised.

Design and implementation of maximum constant boost switched inductor z-source inverter for three-phase on-line uninterrupted power supply

Purpose – The purpose of this paper is to present the Switched Inductor Z-Source Inverter (SLZSI) topology for three-phase on-line uninterruptible power supply (UPS) by employing third harmonic injected maximum constant boost pulse width modulation (PWM) control. Conventional UPS consists of step-up transformer or boost chopper along with voltage source inverter (VSI) which reduces the efficiency and increases energy conversion cost. The proposed three-phase UPS by using SLZSI has the voltage boost capability through shoot through zero state which is not available in traditional VSI and current source inverter. Design/methodology/approach – Performance of three-phase on-line UPS based on ZLZSI by using third harmonic injected maximum constant boost PWM control is analyzed and evaluated in MATLAB/Simulink software and the results are compared with Z-source inverter (ZSI) fed UPS. Experimental results are presented for the validation of the simulation and theoretical analysis. Findings – The output voltages, currents, THD values, voltage stress and efficiencies for different loading condition are determined and compared with the theoretical values and UPS with ZSI. The experimental results validate the theoretical and simulation results. Originality/value – Compared with the traditional ZSI, the SLZSI provides high-voltage boost inversion ability with a very short shoot through zero state. This proposed UPS by using SLZSI increases the efficiency with less number of components, reduces the harmonics, increases the voltage gain and reduces the voltage stress.

ESL-𝚪-Z- Source Inverter

On the basis of the traditional ZSI (Z-source inverter), this paper presents a ESL-Γ-ZSI, which uses a unique Γ-shaped impedance network and an extended SL network for boosting its output voltage in addition to their usual voltage-buck behavior. The inverter can increase the boost factor through adjusting shoot-through duty ratio and increasing the number of inductors. Capacitor voltage stress of ESL-Γ-ZSI is a constant when 1>D>0, and ESL-Γ-ZSI has small inductor current stress. The working principle of ESL-Γ-ZSI and comparison with the classical ZSI and SL- ZSI are analyzed in detail. The power loss comparison between ESL-Γ-ZSI and Cuk converter is analyzed detailedly. Simulation and experimental results are given to demonstrate the operation features of the inverter.

Switching algorithm for single Z ‐source boost multilevel inverter with ability of voltage control

This study proposes a new topology of cascaded transformer-based multilevel inverter using single Z-source. The suggested circuit consists of only one Z network and one DC voltage source; as a result installation area is reduced. In this topology, the output voltage amplitude is not limited to DC voltage source similar to traditional cascaded transformer-based multilevel inverter and can be increased with Z network shoot-through state control flexibly. Besides, the same as traditional Z-source inverter, it is more reliable against short circuit. Also, a particular switching algorithm has been suggested for presented inverter, which can obtain total harmonic distortion (THD) of output voltage nearly constant for different boost ratio. Moreover, as compared to traditional Z-source inverter, the THD of output voltage is decreased in the suggested topology. The performance of proposed inverter and switching algorithm are validated with simulation results using MATLAB/SIMULINK software and experimental results based PCI-1716 data acquisition system.

A Three Phases Z-Source Inverter Topology

Now Z-Source inverter is replacing traditional inverter and becoming a research focus. But traditional Z-source inverters bring high voltage stress both in DC input and the Z-source network, which restricts its wide application. In order to solve this problem, a new type Z-source structure with third harmonic injection control strategy is proposed in this paper. The principle and operation models are analyzed. Compared with traditional boost-type Z-Source topologies, the proposed topology offers lower voltage stress, whats more, soft-start strategy can be implemented to suppress the inrush surge arising in the start process. Finally, simulation results demonstrate the good performance of the proposed inverter.

Modeling and Novel Modulation of Enhanced Z-source Inverter

In this paper, an Enhanced Z-source inverter is proposed. Compared to the traditional Z-source inverter, it can obtain high voltage conversion factor with a short shoot-through duration, and can decrease Z-source capacitor voltage stress significantly. In order to identify its inherent character, the transient modeling of continuous conduction mode (CCM) in dc side is presented. Through the detailed analysis, a right-half-plane zero is found in its control-to–output function. Moreover, an improved control method for the Z-source inverter is proposed in this paper. In comparison with traditional maximum constant boost control method, this improved control method has noticeable advantages. Not only switching frequency can be reduced significantly but also the volume of the Z source can be lessened as a result of six shoot through states per carrier period while obtaining the same voltage boost gain. Simulation and experimental results have demonstrated the validity of small-signal models and the merits of the proposed control method.