Four-leg parallel Z-source inverter based DG systems to enhance the grid performance under unbalanced conditions

This paper presents a DG system based on four-leg parallel Z-source inverters in integrating a renewable generation system into the grid. Particularly, four-leg distribution schemes give flexibility into the DG system by supporting other functions of power distribution like control of zero sequence components and unbalance mitigation. To increase the capacity and to have redundancy, a parallel structure for the Z-source inverter is proposed. The emphasis is given to component count and the modular structure, thereby reducing the cost while achieving the system reliability. A modulation method is proposed based on interleaved carriers to reduce the output current ripple. Separate controllers are designed in stationary reference frame for the AC side of each inverter. The AC side controller is designed using a combination of p+resonance and negative feedback time delay. The combined controller would deliver good reference tracking and harmonic rejection properties. Another controller is designed for the DC side Z-source impedance network to mitigate the fluctuations in the renewable source. The whole system is driven from a higher level controller that would generate current references to operate the total system in two operating modes, to deliver specified power and to control the unbalances and zero sequence. Proposed control method is tested with simulation results obtained using Matlab/Simulink and PLECS. Subsequently, it is experimentally validated using a laboratory prototype.

[1]  F.Z. Peng,et al.  Low cost fuel cell inverter system for residential power generation , 2004, Nineteenth Annual IEEE Applied Power Electronics Conference and Exposition, 2004. APEC '04..

[2]  A. M. Tuckey,et al.  A low-cost inverter for domestic fuel cell applications , 2002, 2002 IEEE 33rd Annual IEEE Power Electronics Specialists Conference. Proceedings (Cat. No.02CH37289).

[3]  F. Blaabjerg,et al.  An interleaved active power filter with reduced size of passive components , 2006, Twenty-First Annual IEEE Applied Power Electronics Conference and Exposition, 2006. APEC '06..

[4]  F.Z. Peng,et al.  Z-source inverter for adjustable speed drives , 2003, IEEE Power Electronics Letters.

[5]  Poh Chiang Loh,et al.  Pulse-width modulation of Z-source inverters , 2004, Conference Record of the 2004 IEEE Industry Applications Conference, 2004. 39th IAS Annual Meeting..

[6]  Donald Grahame Holmes,et al.  Stationary frame current regulation of PWM inverters with zero steady-state error , 2003 .

[7]  Donald Grahame Holmes,et al.  Stationary frame current regulation of PWM inverters with zero steady state error , 1999, 30th Annual IEEE Power Electronics Specialists Conference. Record. (Cat. No.99CH36321).

[8]  Paolo Mattavelli,et al.  A Negative Feedback Repetitive Control Scheme for Harmonic Compensation , 2006, IEEE Transactions on Industrial Electronics.

[9]  Jinjun Liu,et al.  A Transformerless 2-Level Inverter Based Static Var Generator with Multiple Functions in Medium Voltage Application , 2006, Conference Record of the 2006 IEEE Industry Applications Conference Forty-First IAS Annual Meeting.

[10]  Poh Chiang Loh,et al.  Modeling and design of multi-loop closed loop controller for Z-source inverter for Distributed Generation , 2006 .

[11]  T. Kawabata,et al.  Parallel Operation of Voltage Source Inverters , 1986, 1986 Annual Meeting Industry Applications Society.

[12]  Gerard Ledwich,et al.  Negative-phase-sequence reduction with adjacent static reactive-power compensators , 1994 .

[13]  J.-W. Jung,et al.  Modeling and control of a fuel cell based Z-source converter , 2005, Twentieth Annual IEEE Applied Power Electronics Conference and Exposition, 2005. APEC 2005..

[14]  Poh Chiang Loh,et al.  Small-signal and signal-flow-graph modeling of switched Z-source impedance network , 2005, IEEE Power Electronics Letters.

[15]  F.Z. Peng,et al.  Low cost fuel cell converter system for residential power generation , 2004, IEEE Transactions on Power Electronics.

[16]  Hirofumi Akagi,et al.  The theory of instantaneous power in three-phase four-wire systems: a comprehensive approach , 1999, Conference Record of the 1999 IEEE Industry Applications Conference. Thirty-Forth IAS Annual Meeting (Cat. No.99CH36370).

[17]  Fang Zheng Peng.  Z-source inverter , 2002 .