An Optimal Current Controller Design for a Grid Connected Inverter to Improve Power Quality and Test Commercial PV Inverters

Grid connected inverters play a crucial role in generating energy to be fed to the grid. A filter is commonly used to suppress the switching frequency harmonics produced by the inverter, this being passive, and either an L- or LCL-filter. The latter is smaller in size compared to the L-filter. But choosing the optimal values of the LCL-filter is challenging due to resonance, which can affect stability. This paper presents a simple inverter controller design with an L-filter. The control topology is simple and applied easily using traditional control theory. Fast Fourier Transform analysis is used to compare different grid connected inverter control topologies. The modelled grid connected inverter with the proposed controller complies with the IEEE-1547 standard, and total harmonic distortion of the output current of the modelled inverter has been just 0.25% with an improved output waveform. Experimental work on a commercial PV inverter is then presented, including the effect of strong and weak grid connection. Inverter effects on the resistive load connected at the point of common coupling are presented. Results show that the voltage and current of resistive load, when the grid is interrupted, are increased, which may cause failure or damage for connecting appliances.

[1]  Dahaman Ishak,et al.  Deadbeat-based PI controller for stand-alone single-phase voltage source inverter using battery cell as primary sources , 2011, 2011 IEEE Conference on Clean Energy and Technology (CET).

[2]  Marco Liserre,et al.  Grid Converters for Photovoltaic and Wind Power Systems , 2011 .

[3]  Bader N. Alajmi.  Design and control of photovoltaic systems in distributed generation , 2013 .

[4]  M. A. Elsaharty,et al.  Passive L and LCL filter design method for grid-connected inverters , 2014, 2014 IEEE Innovative Smart Grid Technologies - Asia (ISGT ASIA).

[5]  Ali Algaddafi.  Advanced Modelling and Designing of an Optimal Controller Converter , 2016 .

[6]  Vinod John,et al.  Filter Optimization for Grid Interactive Voltage Source Inverters , 2010, IEEE Transactions on Industrial Electronics.

[7]  Yibin Tong,et al.  Analysis of voltage distortion for parallel PWM inverters with L filter , 2012, Proceedings of The 7th International Power Electronics and Motion Control Conference.

[8]  Jian Sun,et al.  Impedance-Based Stability Criterion for Grid-Connected Inverters , 2011, IEEE Transactions on Power Electronics.

[9]  Huai Wang,et al.  A Robust Passive Damping Method for LLCL-Filter-Based Grid-Tied Inverters to Minimize the Effect of Grid Harmonic Voltages , 2014, IEEE Transactions on Power Electronics.

[10]  F.B. Libano,et al.  A PIC controller for grid connected PV system using a FPGA based inverter , 2000, ISIE'2000. Proceedings of the 2000 IEEE International Symposium on Industrial Electronics (Cat. No.00TH8543).

[11]  Yun Wei Li,et al.  Investigation and resonances damping of multiple PV inverters , 2012, 2012 Twenty-Seventh Annual IEEE Applied Power Electronics Conference and Exposition (APEC).

[12]  Hiranmay Saha,et al.  AN EFFICINT TECHNIQUE FOR CONTROLLING POWER FLOW IN A SINGLE STAGE GRID-CONNECTED PHOTOVOLTAIC SYSTEM , 2014 .

[13]  Neil Brown,et al.  An Analogue Computation based Photovoltaic Emulator for realistic Inverter Testing , 2015 .

[14]  Gerd Griepentrog,et al.  Towards next generation photovoltaic inverters , 2011, 2011 IEEE Energy Conversion Congress and Exposition.

[15]  E. Torres,et al.  Impact of wind power in isolated power systems , 2012, 2012 16th IEEE Mediterranean Electrotechnical Conference.

[16]  Stephen J. Finney,et al.  A Modified Stationary Reference Frame-Based Predictive Current Control With Zero Steady-State Error for LCL Coupled Inverter-Based Distributed Generation Systems , 2011, IEEE Transactions on Industrial Electronics.

[17]  E. Olias,et al.  Digital control based on the shifting phase for grid connected photovoltaic inverter , 2008, 2008 Twenty-Third Annual IEEE Applied Power Electronics Conference and Exposition.

[18]  Wuhua Li,et al.  Effect of connection cable impedance on multi-inverter parallel system and an optimized controller with zero steady circulating current , 2008, 2008 34th Annual Conference of IEEE Industrial Electronics.

[19]  Daniel Pizarro-Perez,et al.  LQG Servo Controller for the Current Control of $LCL$ Grid-Connected Voltage-Source Converters , 2012, IEEE Transactions on Industrial Electronics.

[20]  K. Elnaddab,et al.  Review: Grid-Connected Inverter with Its Filter and Providing Suggestions for Designing a Transformerless Inverter , 2016 .

[21]  J.H.R. Enslin,et al.  Harmonic interaction between large numbers of photovoltaic inverters and the distribution network , 2003, 2003 IEEE Bologna Power Tech Conference Proceedings,.

[22]  Frede Blaabjerg,et al.  Active Damping of LLCL-Filter Resonance Based on LC-Trap Voltage or Current Feedback , 2016, IEEE Transactions on Power Electronics.

[23]  S. Premrudeepreechacharn,et al.  Power control of single-phase voltage source inverter for grid-connected photovoltaic systems , 2011, 2011 IEEE/PES Power Systems Conference and Exposition.

[24]  Bin Li,et al.  Research on grid-connected interleaved inverter with L filter , 2013, 2013 1st International Future Energy Electronics Conference (IFEEC).

[25]  Yuen-Haw Chang,et al.  A Closed-Loop High-Gain Switched-Capacitor-Inductor-Based Boost DC-AC Inverter , .

[26]  S. Ali Khajehoddin,et al.  Control design in μ-synthesis framework for grid-connected inverters with higher order filters , 2016, 2016 IEEE Energy Conversion Congress and Exposition (ECCE).

[27]  Donald Grahame Holmes,et al.  Grid current regulation of a three-phase voltage source inverter with an LCL input filter , 2003 .