A Highly Reliable and High Efficiency Quasi Single-Stage Buck-Boost Inverter
Abstract
To regulate an output ac voltage in inverter systems having wide input dc voltage variation, a buck-boost power conditioning system is preferred. This paper proposes a novel high efficiency quasi single-stage single-phase buck-boost inverter. The proposed inverter can solve current shoot-through problem and eliminate PWM dead-time, which leads to greatly enhanced system reliability. It allows bidirectional power flow and can use MOSFET as switching device without body diode conducting. The reverse recovery issues and related loss of the MOSFET body diode can be eliminated. The use of MOSFET contributes to the reduction of switching and conduction losses. Also, the proposed inverter can be operated with simple PWM control and can be designed at higher switching frequency to reduce the volume of passive components. The detailed experimental results are provided to show the advantages of the proposed inverter. Efficiency measurement shows that using simple PWM control the proposed inverter can obtain peak efficiency of 97.8 % for 1.1 kW output power at 30 kHz switching frequency.
EXISTING SYSTEM:
Output voltages of renewable energy sources change in a wide range. To regulate an inverter output voltage in systems having wide input dc voltage variation, a buck-boost power conditioning system is preferred. The buck-boost inverters (BBIs) are also used for plug-in hybrid electric vehicles, uninterruptible power supplies, ac motor drives, and bidirectional buck-boost rectifier. Fig. 2 shows a two-stage BBI obtained by cascading a boost dc-dc converter with a VSI. It requires a bulky intermediate power decoupling capacitor C , to decouple the power between the boost dc-dc converter and VSI two-stage BBI obtained by cascading a buck dc-dc converter with a CSI. It requires a bulky input inductor L , which decreases the power density. qZ-source inverter (qZSI) which can be viewed as quasi in single-stage BBI. It can obtain both the buck and boost functions by placing impedance network between main power source and inverter bridge. It is immune to EMI noise and has no shoot-through and dead-time problems. However, during the boost operation it has high switch voltage and current stresses (see Table I) which go against its efficiency, and its attainable voltage gain is practically limited. In , an active BBI is developed. It has the desired buck-boost function by using more active switches in the output. However, like the traditional VSI, it is not resistant to the shoot-through problem at dc side and has commutation problem at ac side. Therefore, finite dead-time has to be used at the dc side and lossy snubber circuits have to be attached to switches at the ac side in order to avoid the commutation problem. Alternatively, as with conventional ac-ac converters, soft commutation strategy has to be used for the switches at the ac side by sensing output voltage polarity. The sensing technique increases control complexity and decreases converter reliability and quality of output waveforms.
PROPOSED SYSTEM:
In this paper, a new MOSFET based bidirectional quasi single-stage single-phase BBI is proposed. It can provide a regulated ac output voltage for wide input dc voltage variation owing to its buck-boost capability, and can solve the limited gain problem of the VSIs and CSIs. Unlike the conventional two-stage BBI, it does not require intermediate power decoupling capacitor. The proposed inverter has no current shoot-through problem and can eliminate the pulse width modulation (PWM) dead-time, which lead to greatly enhanced system reliability. The body diodes of MOSFETs do not conduct in the proposed topology, which avoids the risk of MOSFETs failure associated with the poor reverse recovery of MOSFET body diode. By using power MOSFETs in conjunction with externally selected fast recovery diodes, the proposed inverter can realize high frequency and high efficiency operation. The topology derivation, switching strategies for buck and boost operations, operation principle, and circuit analysis are given in the paper. A 1.1 kW hardware prototype is tested and detailed experimental results are provided to verify the advantages of the proposed inverter.
CONCLUSION
In this paper, a highly reliable and high efficiency quasi single-stage single-phase bidirectional buck-boost inverter is proposed. The proposed inverter takes the dual-buck structure at the input dc side and the switching cell structure at the ac output side. It is immune from both short-circuit and open-circuit problems. Therefore, PWM dead-times can be eliminated in the proposed inverter, which results in high quality output voltage waveforms. Moreover, it utilizes high speed power MOSFETs along with externally selected fast recovery diodes, which decrease the switching and conduction losses. Thus, high frequency and high efficiency operation is realized. The operation principle and circuit analysis of the proposed topology are presented in detail. To verify performance of the proposed inverter, a 1.1 kW laboratory prototype inverter is fabricated and experiments are performed for both buck and boost modes to obtain a 220 Vrms ac output voltage for wide range of input dc voltage (185 V-400 V) . The efficiency measurement shows that the proposed inverter can obtain maximum efficiency of 97.8 % and minimum efficiency of 96. 1 % at 30 kHz frequency with simple PWM control.
REFERENCES
[1] R. R. Errabelli, and P. Mutschler, “Fault-tolerant voltage source inverter for permanent magnet drives,” IEEE Trans. Power Electron., vol. 27, no. 2, pp. 500-508, Feb. 2012.
[2] B. Sahan, S. V. Araujo, C. Noding, and P. Zacharias, “Comparative evaluation of three-phase current source inverters for grid interfacing of distributed and renewable energy systems,” IEEE Trans. Power Electron., vol. 26, no. 8, pp. 2304-2318, Aug. 2011.
[3] S. Jain and V. Agarwal, “A single-stage grid connected inverter topology for solar PV systems with maximum power point tracking,” IEEE Trans. Power Electron, vol. 22, no. 5, pp. 1928-1940, Sep. 2007.
[4] S. Rajakaruna and L. Jayawickrama, “Steady-state analysis and designing impedance network of Z-source inverters,” IEEE Trans. Ind. Electron., vol. 57, no. 7, pp. 3245–3253, Jul. 2010.
[5] F. Z. Peng, “Z-source inverter,” IEEE Trans. Ind. Appl., vol. 39, no. 2, pp. 504–510, Mar./Apr. 2003.
[6] J. C. Rosas-Caro, F. Z. Peng, and H. Cha, “Z-source-converter-based energy-recycling zero-voltage electronic load,” IEEE Trans. Ind. Electron., vol. 56, no. 12, pp. 4894–4902, Dec. 2009. [7] Q. Tran, T. Chun, and J. Ahn, “Algorithms for controlling both the DC boost and AC output voltage of Z-source inverter,” IEEE Trans. Ind. Electron., vol. 54, no. 5, pp. 2745–2750, Oct. 2007.
[8] W. Qian, F. Z. Peng, and H. Cha, “Trans-Z-source inverters,” IEEE Trans. Power Electron., vol. 26, no. 12, pp. 3453–3463, Dec. 2011.
[9] Y. Tang, X. , and Y. He, “Active buck–boost inverter,” IEEE Trans. Ind. Electron., vol. 61, no. 9, pp. 4691-4697, Sep. 2014.
[10] Y. Tang, F. Xu, Y. Bai and Y. He, “Comparative analysis of two modulation strategy for active buck-boost inverter,” IEEE Trans. Power Electron., vol. 31, no. 11, pp. 7963-7971, Nov. 2016.
[11] H. Schmidt, “Current inverter for direct/alternating currents, has direct and alternating connections with an intermediate power store, a bridge circuit, rectifier diodes and a inductive choke,” Patent Applications DE10221592 A1, May 15, 2002