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SIMULATION AND ASSESSMENT OF
SINGLE PHASE SEMI-Z-SOURCE
INVERTER (S-ZSI)
Ashok Kumar Jhala and Rajeev GuptaPacific Academy of Higher Education and Research, Udaipur ABSTRACT
The present investigation is a step towards the development of a single phase semi-Z-source inverter (s-ZSI) with photovoltaic, its topology and the assessment with respect to the voltage and current output. The proposed semi-Z-source inverter use only two active switches to achieve a desired output. The simulation was carried out using MATLAB and the results are discussed in various waveforms.
Key words: Z-Source Inverter, Switching, Simulation, Input Current/ Voltage, Output Current/ Voltage
Cite this Article: Ashok Kumar Jhala and Rajeev Gupta, Simulation and Assessment of Single Phase Semi-Z-Source Inverter (S-ZSI). International Journal of Electrical Engineering & Technology, 7(1), 2016, pp. 30-34. http://www.iaeme.com/IJEET/issues.asp?JType=IJEET&VType=7&IType=1
1. INTRODUCTION
World today is moving towards the utilization of green energy and solar energy is one of the most potential option. Photovoltaic or more commonly referred to as PV’s directly convert sunlight to electricity and it is potentially so efficient to be able to convert 28-40 percent solar radiations to electrical energy. The PV based power systems are designed with the aim of converting as much irradiant power as possible into real power especially for grids. However these clean energy applications have a limitation of fluctuating output voltage which can be overcome by using power converter or inverters that provide voltage boosting capabilities. Working on these aspects many of the inverter topologies have been proposed including both two level and multi-level, which have been applied to dc-ac power inversions such as motor drive, renewable energy interfacing and un-interruptible power supply. Also, to stabilize the output voltage a front end dc-dc boost converter is inserted between renewable energy source and a converter. This type of two stage mechanics increases
Probably the first Z-source inverter proposed by Peng (2003) used a symmetrical LC impedance network to replace the dc-link capacitor in traditional VSI. The operation states of Z-source inverter can be classified as shoot through states and non-shoot through states i.e., with six active states and two null states (Fig.1). During the active state the circuitry and the load of the inverter is taken as the constant current source, wherein the diode (D) naturally conducts because of capacitor discharging process and requirement of powering load from an Input source.
2. SIMULATION OF PROPOSED Z-SOURCE INVERTER
The proposed semi-Z-source inverter system consists of a photovoltaic (PV) source, the DC link circuit of the Z-source inverter and the inverter bridge. The basic network includes a two port network with a split inductor L1, L2 and capacitors C1 and C2.
These are connected on X-shape (Fig.2). It is used have to provide an impedance source coupling the inverter to the DC source.
The switches used are MOSFET’s that are more suitable in the proposed network.
3. VOLTAGE ASSESSMENT
A Z-source inverter has two states, first the shoot through state and second the non-shoot through state. Table 1 gives switching modes of a Z-source inverter (4). Similarly, in a single phase Z-source inverter, there are four active and shoot through states represent two switches on a single leg are turn on. The operating principle is based on the aim of turning zero states to the shoot through states and keep the active switching states unchanged. The switches S1 and S2 are conducted in a complementary manner.
The simulation of the proposed inverter was performed using MATLAB. To determine the variation in efficiency of the proposed confirmation a number of experiments were performed. In the present investigation, the parameters include L1=
L2 = 1.3mH and C1 = C2 =1µH, R= 4Ω with the input voltage of 160V. Fig.3 a&b
gives the simulation results of the proposed z-source network for input current (3a) and input voltage (3b) as obtained through photovoltaic. Fig. 4 revel the capacitor voltage of the proposed semi-Z-source inverter. The waveforms of the output current and voltage as in indicated in Fig. 5 a&b, respectively in the terms of ac. The waveforms for the input current and voltage as well as output voltage and current show stable performance in the proposed circuit.
Table 1 Switching modes of single phase Z-source inverter S4 S3 S2 S1 Switching mode 1 0 0 1 Active mode 0 1 1 0 0 1 0 1 Zero mode 1 0 1 0
0 /1 0/1 1 1 Shoot through mode
Figure 2 Simulation of semi- Z-source inverter
Figure 3b Input Voltage
Figure 4 Semi-Z-source capacitor voltage
Figure 5a Output Voltage
CONCLUSION
The present investigation reveals the importance of semi-Z-source inverter connected with PV system. The inverter at a time utilizes only two active switches to achieve the same output as in the traditional Z-source inverter. Both the switches are used complimentarily to achieve the boost function. The proposed system is a promising structure to be used with renewable energy options like the PVs. Where in the conventional models require two stages for power conversion, the proposed model uses only a single stage inverter for direct DC-AC conversion. The reduced number of switches reduces switching losses as well as cuts on the cost hence makes it more economical with increased efficiency.
REFERENCES
[1] Bialasiewicz, T. 2008. Renewable energy systems with photovoltaic power generators: Operation and Modeling. IEEE transactions on Industrial Electronics. 55(7): 2752-2758.
[2] Peng, FZ. 2003. Z-source inverter. IEEE transactions on Industrial Applications. 39(2): 504-510.
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