Proc. of Int. Conf. on Control, Communication and Power Engineering 2010
A New Inverter Topology for Adjustable Speed Drive Systems Amitava Das1, Debasish Lahiri1, and Arup Kumar Goswami2 1
Electrical Engineering Department, TI, Kolkata, India Email: amitavadas@ieee.org, dlsir.ti@gmail.com 2 Electrical Engineering Department, NIT - Silchar, India Email: gosarup@gmail.com inverters (qZSI) [4, 5]. The main advantages of qZSI circuits are improved input profiles and a common DC rail between the Z-source and inverter, unlike the traditional ZSI circuits. Another approach to ZSI concept with use of transmission line model can be found in [7] and [8]. Present research indicates another possibility: that is, to incorporate different passive networks at the input to the inverters, a technique that differs from the symmetrical LC lattice network [1, 2, 3] which is typically used in ZSI. These alternative passive networks have been known from many years from circuit theory. Utilization of there will open new possibilities for onestep, energy processing Buck-Boost voltage converters. This paper outlines the most significant alternative passive networks (Fig. 1) and their selected applications in inverters. Simulation results are shown for this approach. The method involves the use of the T-source inverter (TSI). The goal of this paper is to present a topology similar to that of the ZSI with use of impulse transformer with small inductive leakage. The indirect goal is to demonstrate, with the help of above mentioned transformer, that in the topology presented here it is possible to increase the output voltage.
Abstract— This paper presents a new topologies of voltage source inverters with alternative input LC networks for adjustable speed drive system. The basic topology is known in the literature as a Z-source inverter (ZSI). Alternative passive networks were named as T-sources inverter (TSI). T-source inverter has fewer reactive components in comparison to conventional Z-source inverter. The most significant advantage of the T-source inverter (TSI) is its use of a common voltage source of the passive arrangement. Simulation results for the TSI are in agreement with theoretical prediction. PSIM software is used for simulation studies. Index Terms— LC network, ZSI, T-source inverter, motor drive, quasi Z –source inverter, PWM.
I. INTRODUCTION Fossil fuel reserve availability and environmental concerns are now the driving forces behind the use of new clean and renewable energy sources, such as photovoltaic (PV) energy, wind energy, and fuel cell, which are the input sources of alternative generation system [1]. Moreover, the inverter plays an important role in alternative generation system. Inverters with variable voltage which have an input from a low voltage DC source (eg., a PV cell) are mostly realized in the following three basic topologies: (a) PWM VSI+DC/DC boost converter without transformer (b) PWM VSI + DC/DC boost converter with transformer (c) PWM CSI. None of these solutions is fully satisfactory. Therefore there is a continuous effort to find newer and better solutions. A more interesting solution utilizes the Z – source inverter. The distinguishing feature of this inverter is its input symmetrical LC lattice network which has four impedances. In this design, ZSI provides the single stage voltage Buck-Boost operation, which results in lower costs and decreased losses. The ZSI can be made bidirectional by replacing the input diode with a bidirectional conducting, unidirectional blocking switch [3, 4]. There is also interesting research into NPC (Neutral Point Clamped) ZSI circuits which has been presented in detail in the following papers [5, 6, 7, 8, 9].These findings do not differ from those that result when using basic symmetrical LC lattice network [1, 2, 3]. Rather, they focus on changing the topology arrangement of the connections and don’t focus on either changing the basic structure or improving the ZSI. To eliminate the inconvenience of the typically Z-source inverter, there were modifications of its basic structure that consisted mainly in the change of primary source position. These modifications led to quasi-Z-source
Fig 1:Passive networks alternative to basic LC lattice network
II. T – SOURCE INVERTER The LC lattice applied in the ZSI successfully replaces the DC-DC input stage in boost-type voltage source inverters. To minimize the Z-source size, the couple inductors are designed, and the two inductors are built together on one core. To show the possibility of extending the operation range of the ZSI, the use of a low leakage inductance transformer and one capacitor instead of the LC-lattice is proposed here. A high frequency transformer based T-source inverter (TSI) is developed in this section. The topologies of TSI using modifications from Fig. 1(e) and Fig.1 (f) are shown in the Fig.2 (a) and 162
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