Active and Reactive Power Control of Single Phase Transformerless Grid Connected Inverter for Distributed Generation System

ABSTRACT:

This paper presents a novel approach by which enhancement in power quality is ensured along with power control for a grid interactive inverter. The work presented in this paper deals with modeling and analyzing of a transformer less grid-connected inverter with active and reactive power control by controlling the inverter output phase angle and amplitude in relation to the grid voltage. In addition to current control and voltage control, power quality control is made to reduce the total harmonics distortion. The distorted current flow can compensate for the disturbance caused by nonlinear load.

INVERTER

The Simulation of the grid interactive inverter is carried out in MATLAB/SIMULINK environment and experimental results were presented to validate the proposed methodology for control of transformer less grid interactive inverter which supplies active and reactive power to the loads and also makes the grid current to a sinusoidal one to improve the power factor and reduce the harmonics in grid current. This work offers an increased opportunity to provide distributed generation (DG) use in distribution systems as reliable source of power generation to meet the increased load demand which helps to provide a reasonable relief to the customers and utilities to meet the increasing load demand

KEYWORDS:

  1. Grid interactive inverter
  2. Voltage Controller
  3. Current Controller
  4. THD improvement
  5. Reactive power compensation
  6. Intelligent power module

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Figure 1: Schematic diagram of grid connected system

Figure 2: grid tie inverter

EXPECTED SIMULATION RESULTS:

Figure 3: Simulation waveforms of current a) when load is controlled rectifier b) inverter current c) grid current d) the reference current

Figure 4: Power flow graph.

Figure 5: grid voltage, load current & grid current

Figure 6: FFT analysis

Figure 7: load current

Figure 8: Injected current

 CONCLUSION:

 The simulation of single phase grid interactive inverter has been carried out with non-linear load and the results obtained from the simulations shows that this control technique improves the power quality ie THD and the power factor. The simulation also shows that power transfer of active and reactive power from the inverter to grid is possible. The reactive power required for the load is completely provided from the inverter. The hardware implementation of the interactive inverter has been conducted using real time workshop in the MATLAB Simulink environment.

SINGLE PHASE

The half wave rectifier is used as load in the hardware implementation. The results show that the controller is capable for reactive power compensation, and maintaining constant voltage at the grid satisfying standard for grid interconnection. That is the THD is lessthan5% 3.74 and the power factor is .9977 which is near to unity. Energy conservation by load management is possible and a reasonable relief to the customer and voltage profile is maintained at the grid. This work can be extended to cascaded inverter configuration and reliability analysis has to be made as a better option for future studies.

REFERENCES:

[1] EPRI-white paper “Integrating Distributed Resources into electric utility systems ”Technology Review.December2001

[2] Thomas Ackerman “Distributed Generation, a definition’’ Electric power system research,57(3),2001,pp195-204

[3] G. Joos, B.T Ooi, D. McGill is, F.D. Galiana, and R. Marceau, “The potential of distributed generation to provide ancillary services,” at IEEE Power Engineering Society Summer Meeting, 16-20 July 2000, vol. 3, pp. 1762 – 1767

[4] Frede Blaabjerg, Zhechen, Soreren Baekhoej Kjaer “Power electronics as efficient interface in dispersed power generation system” IEEE Transactions on Power Electronics vol:19,no.5, sept2004 pp1184-1194

[5] Yong Yang, Yi Ruan, Huan-qing Shen, Yan-yan Tang and Ying Yang; “Grid-connected inverter for wind power generation system” Journal of Shanghai University, Page(s):.51-56, Vol. 13, No 1,Feb,2009.