Quasi Z-source

A hybrid PWM strategy similar to (dos Santos et al., 2010b) for a two-level Z-source inverter is implemented for the Z-source NPC topology (Muniz et al., 2011) to reduce its algorithm calculation by combining the theory of SVPWM and triangular comparison PWM. A reduced component count Z-source NPC converter with modified modulation technique is reported in (Poh Chiang et al., 2009; Gao et al., 2007) using a single Z-source network. This topology reduces the requirement of an additional impedance network to create a neutral point as explained in (Poh Chiang et al., 2007b; Muniz et al., 2011). The modulation scheme is modified to create a full DC-link (FDCL) and a partial DC-link (PDCL) shoot-through state to boost the output voltage without increasing the commutation time as in the conventional NPC modulation techniques (Poh Chiang et al., 2007b). An effective control method for a cascaded quasi Z-source inverter using multilevel space vector modulation (MSVM) is presented in (Galigekere and Kazimierczuk, 2011) for single phase and in (Liu et al., 2013b) for three-phase to generate seven-level voltage.

This paper overcomes the problem with voltage source inverter by using Quasi Z Source network. To decrease the shoot through duty cycle at same voltage boost factor cascaded connection of qZSI is used and for further decreasing the shoot-through duty cycle the number of stages of the qZS-network could be increased. The usage of voltage doubler rectifier (VDR) results in less turns of ratio in isolation transformer. To decrease the stresses on the switches the PWM inverter is replaced by diode clamped multi level inverter. From results it is proven that the proposed front end high step up conversion has ripple free intermediate dc voltage and it is also confirmed that the proposed converter ensures stable 3 × 400 Vac rms 50-Hz output voltage within the predefined input voltage.

The efficiency and the voltage gain of the conventional q-ZSI are limited and comparable with the traditional system of a voltage source inverter with the auxiliary step-up DC/DC converter in the input stage [2] [3]. The concept of extending the quasi ZSI gain without increasing the number of active switches has been reported in the literature [4] [5]. These new converter topologies are known as extended boost q-ZSI and can be generally classified as capacitor assisted, diode assisted topologies and hybrid topologies [5] [6]. In this paper, MDAEB q-ZSI with continuous input current [7] is presented, analyzed and compared for the simple boost control tech- nique. Simulation studies of the proposed inverter configuration are carried out in MATLAB/SIMULINK. The capacitor voltage in the impedance network, voltage gain, boost factor, voltage stress and THD are calculated and compared with the quasi z-source inverter. Hardware of the modified diode-assisted QZSI is developed and the simulation results are verified.

In Proposed system, we are using Z-Source inverter and hence due to that output voltage is boosting and will become equal or greater than input voltage as shown in Fig.21. Applied input voltage is same as applied to existing system also the PI controller is used in this proposed system to control the speed and torque ripple. As explained in PWM, the Hall sensor which works on Hall Effect gives signal to PWM generator and it generates pulses which are used to turn ON and OFF switches. Also as explained in Quasi Z-source network, there are two major working modes which are Shoot Through mode and Non-shoot through mode. In shoot through mode supply is cutting off and fifth switch is working as auxiliary switch which supply the voltage to inverter by discharging capacitor.

[10] L. Yushan, G. Baoming, H. Abu-Rub, F.Z. Peng “Control System Design of Battery- Assisted Quasi-Z-Source Inverter for Mesh-Tie Photovoltaic Power Generation”, IEEE Trans. Sustainable Energy, Vol. 4, no.4, pp. 994-1001 [11] L. Yuan, F.Z. Peng, J.G. Cintron-Rivera, S. Jiang, “Controllerdesignforquasi-Z- sourceinverterinphotovoltaicsystems”, Energy Conversion Congress and Exposition (ECCE), 2010 IEEE, pp: 3187 – 3194.

to convert the dc output from the PV panel into ac supply. The Z-source inverter and quasi Z-source inverter has been considered for photovoltaic (PV) application in recent years. These inverters feature single stage buck-boost and improved reliability due to shoot-through capability. It can be used for single phase and three phase applications. In three-phase applications, the Z-source network only needs to be designed to handle the high frequency ripples. But in single phase applications it also needs to handle the low frequency ripples.

The QZSI circuit differs from that of a conventional ZSI in the LC impedance networkinterface between the source and inverter. The unique LC and diode network connectedto the inverter bridge modify the operation of the circuit, allowing the shoot-throughstate which is forbidden in traditional VSI. This network will effectively protect the circuitfrom damage when the shoot through occurs and by using the shoot-through state, the(quasi-) Z-source network boosts the dc-link voltage. There are several differences betweenthe conventional and the current topology. The QZSI does not need a separateboost IGBT. The voltage boost is realized by switching a shoot through of the inverterduring zero state. Due to the higher boosting frequency the circuit devices L1, L2, C1,and C2 can be designed smaller accordingly, that is, the capacities are within a range of few Farads. In addition, the capacitors do not need to be electrolytic but can be film capacitors,whose life time is not dependent on ambient temperature. For regeneration the QZSI only needs one additional power electronic device, named VT5 when supply to load like electric vehicles engine. With the use of QZSI to supply the electric vehicle’s engine the electrolytic capacitor’s life time restrictions and the effort to control more additional power electronic devices do not apply, contrary to the conventional topology.

In this proposed ANFIS-based PV power generation system operating in a standalone mode . The interface between source and load is accomplished by quasi z source inverter. The shoot through duty ratio is controlled using ANFIS. The load sides voltage and frequency are regulated by controlling the modulation index of the interface of the qZSI. Maximum power is obtained using Maximum Power Point Tracking based ANFIS. The control objectives achieved. Simulations are provided to verify the proposed control approach.

To overcome the drawbacks of the conventional voltage source inverters Z source inverters are introduced by F. Z. Peng [2]. In a Z source inverter a X-shaped LC network is connected in between the input and output side. Thus the dc source is coupled with the impedance network hence it is termed as Z–source inverter. Z-source inverter can work in shoot through and non shoot through mode. It can overcome the drawbacks of conventional VSI, such as limited voltage and shoot through problem. It can also achieve power conversion in a single stage thus the cost and size of the system will be reduced. The quasi-Z-source inverters are the modified form of Z –source inverters.

This paper proposes a dedicated modulation scheme for a bidirectional quasi Z-source modular multilevel converter (BqZS-MMC). The operation principle and a suitable PWM method are proposed. The relation between the modulation index and shoot-through duty ratio is derived. A formula for calculating the required value of quasi Z-source capacitance is given. The simulation results presented in the paper validate the operation and the performance of the proposed topology.

Abstract— This paper explores Switched Inductor (SL) Quasi Z-source Inverter which has high boost factor and performance when compared to other Z-Source inverters along with three control methods: simple boost, maximum boost and maximum constant boost. The proposed inverter improves the input current, reduces the passive count and also the reliability. The simulations are done in MATLAB/Simulink environment by using same input voltage ratio and output load. From different control methods proposed, maximum constant boost provides the highest boost factor as well as reduces passive component requirement along with ripples.

In this paper, a new topology of quasi Z-source inverter (qZSI) based DVR is proposed. In the proposed system, the size of energy storage element is decreased in comparison with the conventional systems, lower component rating and harmonic factor. The simulation results of conventional VSI based DVR and quasi-Z-source based DVR are compared.

Regenerative braking can minimize the wear of the brake pads, and thus extend the driving range of EVs and also reduce the maintenance cost considerably. Operating principles and the equivalent power circuit of EVs under regenerative braking control are designated in this paper. The performance of the BLDC motor based regenerative braking system has been realized by PI controller. The quasi Z source regulates and also boosts up the voltage level. Regenerated energy is stored in the battery across the QZSI. This method of energy regeneration could achieve good dynamic performance, robust stability and improvement in the driving range.

Fig. 3 shows the proposed tapped inductor quasi-Z-source inverter (TL-qZSI). The combination of Lt, D2, and D3 acts as a switched tapped inductor cell. Compared to the traditional quasi-Z-source inverter with continuous input current, only one tapped inductor and two diodes are added. This configuration allows the impedance network with different inductances under shoot-through state and non-shoot-through state. Only the inductance of winding N1 is effective during the shoot-through zero state, while both the inductances of winding N1 and N2 are effective during the non-shoot-through state. It is impossible for the tapped inductor to achieve a complete coupling effect, so leakage inductance exists in the real circuit as shown in Fig. 4. As the turns ratio can be defined as N=N2/N1. The leakage inductor Lk and magnetizing inductor Lm can be described as [18]-[19]

are photovoltaic (PV), wind farms, fuel cell, and biomass. These distributed power generation sources are widely accepted for microgrid applications. However, the reliability of the microgrid relies upon the interfacing power converter.The quasi z-source concept can be applied to all dc-ac, ac-dc and dc-dc power conversion whether two-level. The input voltage and output voltage share the common ground, the size of the inverter is reduced, and it operates in a continuous current mode.BLDC motor is connected at the output side which acts as a load and efficiently utilizes the power obtained from solar using PI. The qZSI acts as the interface in between the PV dc source and the BLDC motor. PI promises the maximum power delivery to the load based on maximum power point tracking (MPPT). The proposed PI-based MPPT offers high efficiency and accuracy. The closed loop control regulates the speed of the BLDC motor for different load conditions and also maintains regulated voltage and current.

This paper has proposed the Implementation of Quasi-Z- Source Four-Leg Inverter with PV by using Model Predictive Control Scheme. The main aim of this paper is to achieve single-stage power converter topology for photo voltaic system under balanced and unbalanced conditions with high control capability. To do that, QZS three-phase four-leg inverter topology was proposed in this study. To improve control capability of the controller, the MPC scheme was employed in the controller stage. The performance of the proposed inverter topology and its control strategy was simulated. The results show that the proposed technique not only has an excellent steady-state and transient performances, but also it is robust against fault conditions.

source magnitude by quasi-Z-source converter, the reliability of proposed topology is increased and the output voltage is not limited to the DC voltage source. To provide a large number of output steps without increasing the number of inverters, asymmetric structures was used and three algorithms to determine the magnitude of DC voltage sources was proposed. The proposed topology has been optimized for various purposes of obtaining minimum switch numbers and DC voltage sources, and maximum numbers of voltage level. Also, to provide output steps and ST state for quasi-Z-source converter, proposed control method was explained. The operation and performance of the proposed topology has been verified with simulation and experimental results. It was shown that the proposed topology has a good performance.

ABSTRACT-This paper presents a model predictive control (MPC) scheme with pv system using quasi-Z-source (qZS) three-phase four leg inverter. Photovoltaics (PV) is a term which covers the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. In order to cope with the drawbacks of traditional voltage source inverters (VSIs), a qZS three-phase four-leg inverter topology is proposed. This topology features a wide range of voltage gain which is suitable for applications in renewable energy-based power systems, where the output of the renewable energy sources varies widely with operating conditions such as wind speed, temperature, and solar irradiation. To improve the capability of the controller, an MPC scheme is used which implements a discrete-time model of the system. The controller handles each phase current independently, which adds flexibility to the system. Simulation and experimental studies verify the performances of the proposed control strategy under balanced and unbalanced load conditions as well as single- phase open-circuit fault condition.

This paper proposes a topology of switched-inductor/capacitor quasi z-source inverter (SIC-qZSI) based on the classic qZSI. This topology is symmetric with a high boost factor in the low duty cycle and high modulation index, the low voltage stress on the capacitors, and the low current of the inductors and the input source. In addition, the current of all inductors and the input current are equal, and the voltage across all the inductors, as well as the voltage across all diodes, are equal. The performance of the proposed topology is confirmed with MATLAB/SIMULINK software and the simulation results and obtained relations are certified by using a prototype of the proposed inverter.

In this paper, a new topology of switched-inductor/capacitor quasi impedance source inverter is suggested, which in comparison with the other topologies possesses higher boost voltage inversion at high modulation index and low shoot through duty cycle. Also, this topology has features like continuous input current, common ground between the input source and the inverter bridge and, low shoot-through current. To express the proposed topology properties, it is compared experimentally in similar conditions relative to the Enhances Boost quasi Z-Source inverter (EB-qZSI). Similar to the EB-QZSI, because of the presence of a series inductor with input voltage source, the inrush current at start-up is limited in the proposed topology. Also, the low voltage stress on the capacitors and the low current ripple of the inductors and the input source are other advantages. Due to the lower number of diodes in the proposed inverter, the efficiency is higher compared to the EB-qZSI inverter. The performance of the proposed topology is confirmed with MATLAB/SIMULINK software. The results of simulation and experimental validate the theoretical analysis of the proposed topology. The experimental results validate the simulation results and there is a good agreement between the simulation results and the experimental results.