Now a day's distributed generation (DG) system uses current regulated PWM voltage source inverters (VSI) for connecting the utility grid with DG source in order to meet the following objectives: 1) To ensure the grid stability 2) active and reactive power control through voltage and frequency control 3) Improvement of power quality (i.e. harmonic mitigation) etc. In this paper the comparative study between adaptive hysteresis and SVPWM current controller is presented in order to ensure the sinusoidal current injected in to the grid. The performance indices include THD of the grid current, fast current tracking during steady state and transient conditions. SVPWM current controller ensures less THD of the grid current at PCC, better dc-link voltage utilization over adaptive hysteresis current controller. The studied system is modeled and simulated in the MATLAB Simulink environment. Keywords-adaptive hysteresis control; voltage source inverter (VSI); total harmonic distortion (THD); utility grid; current control; distributed generation (DG). I. NOMENCLATUREi La ,i Lb ,i Lc Three-phase load currents i Ld ,i Lq d and q axis current components ω Angular frequency θ Transformation angleVoltage at PCC II. INTRODUCTIONDistributed generation (DG) systems becomes more prominent in the world electricity market due to the increased demand for electric power generation, the deregulation of the electric power industry and the requirements to reduce the greenhouse gas emissions etc. DG sources and their interconnection should satisfy certain requirements and specifications when interconnecting with existing electric power systems (EPS). For an inverter-interfaced DG system, the power quality of the utility grid largely depends on the inverter's controller performance. For the past couple of decades, current regulated VSI is widely used for gridconnected inverter system in order to meet the following objectives. 1) To ensure the grid stability 2) active and reactive power control through voltage and frequency control 3) Improvement of power quality (i.e. harmonic mitigation) etc [1]. As compared with the open loop voltage PWM converters, the current-controlled PWM has several advantages such as fast dynamic response, inherent peak-current protection, good dc-link utilization, instantaneous current control etc [2].Basically current control schemes have similar structures that include an inner current feedback loop, and it performs dual tasks: the current error compensation and the PWM modulation. The current control strategies, based on the space vector PWM (SVPWM) is widely employed for three-phase VSI essentially, the SVWPM-based current controller is a kind of linear control strategies and has clearly separated current error compensation and PWM parts, which makes it possible to exploit the advantages of SVWPM as well as to independently design the overall control structure. SVPWM has many advantages such as constant switching frequency, well-defined harmonic spectrum, optimum switching patterns, and excellent DC-link utilizat...

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This paper presents a comparative study between two current control techniques, namely, a basic delta modulator and novel deltasigma modulator. The delta modulator is used widely in induction motor drives as a known method for converting analog signal in to digital form; to optimize (harmonic minimization) pulse width modulated (PWM) inverter waveforms on-line without conventional optimization processes, like selective harmonic elimination or harmonic weighting techniques. The quantization noise arises from the A/D conversion is distributed uniformly to the frequency axis. But in the delta-sigma modulator the noise varies. It provides several advantageous over Delta modulation. It can be successfully applied to over-sampling digital-to-analog and analog-to-digital data converters switch mode power supplies and switch mode inverters. The spread spectrum nature of delta-sigma modulator, noise level within unnecessary band is much reduced. It is relatively easy to implement, smooth inverter operation and provides low harmonics at the inverter output. The comparative study between delta and delta-sigma current controllers has been verifi ed by the simulation undertaken by the MATLAB/SIMULINK environment in terms of the high switching frequency power spectra density, average switching frequency, rms current error and total harmonic distortion of load current waveforms. The obtained theoretical results are validated with experimental platform based on TMS320F2812 digital signal processor for effectiveness of the study.