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SinglePhase AC–AC Converter Based on QuasiZSource Topology
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02012013, 11:10 AM
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SinglePhase AC–AC Converter Based on QuasiZSource Topology
[46104] Abstract This paper dealswith a new family of singlephase ac– ac converters called singlephase quasiZsource ac–ac converters. The proposed converter inherits all the advantages of the traditional singlephase Zsource ac–ac converter, which can realize buck–boost, reversing, or maintaining the phase angle. In addition, the proposed converter has the unique features that the input voltage and output voltage share the same ground and the operation is in the continuous current mode. The operating principles of the proposed converter are described, and a circuit analysis is provided. In order to verify the performance of the proposed converter, a laboratory prototype was constructed with a voltage of 84 Vrms /60 Hz. The simulation and experimental results verified that the converter has a lower input current total harmonic distortion and higher input power factor in comparison with the conventional singlephase Zsource ac–ac converter. INTRODUCTION FOR ac–ac power conversion, the most popular topologies are indirect ac–ac converters with a dc link [1]–[3], matrix converters [4]–[6], and direct pulsewidth modulation (PWM) ac–ac converters [7]–[16]. The indirect ac–ac converters and matrix converters can provide variable output voltage and variable frequency. However, for applications, where only voltage regulation is needed, the direct PWM ac–ac converters are used to perform as ac choppers or power line conditioners with the following features: the provision of a better power factor and efficiency, low harmonic current in line, singlestage conversion, simple topology, ease of control, smaller size, and lower cost [8], [14]–[16]. CIRCUIT ANALYSIS Circuit analysis of the proposed singlephase quasiZsource ac–ac converter begins with the following assumptions: 1) all capacitors and switches are ideal and lossless; 2) the parasitic resistances of L1 and L2 are the same and equal and denoted by r and due to the parasitic resistance of LLf is much smaller than the load impedance, it is neglected in the analysis; 3) the converter is operating in the continuous conduction mode; and 4) the switching frequency is more than the cutoff frequency of the output filter and the frequency of the input and output voltages. The proposed converter has two operational states in one switching period, which are denoted as state 1 and state 2, as shown in Fig. 4(a) and (b), respectively. In state 1, S1 is turned ON and S2 is turned OFF, as shown in Fig. 4(a). The time interval in this state is (1−D)T, where D is the equivalent duty ratio of S2 and T is the switching period. SIMULATION RESULTS In order to verify the advantages of the proposed singlephase quasiZsource ac–ac converter, the PSIM simulation is used in comparison with the conventional singlephase Zsource ac– ac converter presented in [15]. We selected the simulation parameters L1 = L2 = 1 mH, C1 = C2 = 6.8 μF, Lf = 1.4 mH, Cf = 10 μF, and R = 20 Ω. The bidirectional switches were implemented with two IGBTs connected oppositely. The diode voltage drop was set to 2 V and the switching frequency was set to 20 kHz. The input voltage was 84 Vrms/60 Hz. In the simulation, the parasitic resistances of L1 and L2 were set to zero (r = 0 Ω). Table II provides a list of the parameters used in the simulation of the conventional converter in Fig. 1 [15] and the proposed converter in Fig. 2. EXPERIMENTAL VERIFICATIONS We have constructed a laboratory prototype based on TMS320F2812 DSP to verify the properties described earlier. The same parameters were used in the prototype as in the simulation. The input voltage was produced by an ES2000S singlephasemaster (NF Corporation). The bidirectional switches were implemented with two FAIRCHILD G60N90D IGBTs connected oppositely. The input power and input power factor were measured by the ES2000S; the output power was measured by a WT210 digital power meter (YOKOGAWA). CONCLUSION A kind of quasiZsource converter for ac–ac power conversion has been presented in this paper. The proposed converter inherits all the advantages of the traditional singlephase Zsource ac–ac converter, which can realize buck–boost as well as reversal or maintenance phase angle. In addition, the proposed singlephase quasiZsource ac–ac converter has unique advantages in that the input voltage and output voltages share the same ground and the operation of the input current is in CCM. Comparison of the principles of operation and the simulation results with those for the conventional singlephase Zsource ac–ac converter are presented. 
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Marked Labels: erport on quasi z source converter, z source ac to ac convert6er, single phase ac ac converter based on quasi z source topology, 
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