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Journal ArticleDOI

Power Quality Enhancement Using Linear Quadratic Regulator Based Current-controlled Voltage Source Inverter for the Grid Integrated Renewable Energy System

TL;DR: An optimal control strategy using linear quadratic regulator applied in current-controlled voltage source inverter (CCVSI) to control the real and reactive power flow between the renewable energy system (RES) and the grid is presented.
Abstract: This paper presents an optimal control strategy using linear quadratic regulator (LQR) applied in current-controlled voltage source inverter (CCVSI) to control the real and reactive power flow betw...
Citations
More filters
Journal ArticleDOI
TL;DR: The SMC using equivalent control function outperforms the other methods in terms of chattering, THD and PF in the grid during balanced and unbalanced grid voltage conditions even in the existence of nonlinear loads.
Abstract: Development of control technologies facilitates the integration of renewable energy sources to the grid through power electronic converters. In this study, the inverter acts as shunt active power filter along with the power conversion operation. Various sliding mode control (SMC) techniques namely relay and signum method, hysteresis method and equivalent control method are implemented to control the real, and reactive power flow between Renewable Energy System (RES), load and grid using an inverter. To reduce the complexity, the control law (u eq) for equivalent control method is derived using a simple single-phase equivalent circuit of a three-phase voltage source inverter. In this study, the robustness is enhanced by choosing the integral sliding surface. These controllers are used to reduce the total harmonic distortion (THD) and to ensure unity power factor (PF) in the grid during balanced and unbalanced grid voltage conditions even in the existence of nonlinear loads. The SMC using equivalent control function outperforms the other methods in terms of chattering, THD and PF. To illustrate the effectiveness, three different modes are considered: (i) no RES power, (ii) insufficient RES power and (iii) excess RES power. The performance of controllers is validated by the simulation and experimental results.

7 citations

Journal ArticleDOI
24 Apr 2020-Symmetry
TL;DR: This article constructed Lyapunov-Krasovskii functionals containing several symmetric positive definite matrices to obtain robust finite-time stability and stabilization of the uncertain linear system with a non-differentiable time-varying delay.
Abstract: Practical systems such as hybrid power systems are currently implemented around the world. In order to get the system to work properly, the systems usually require their behavior to be maintained or state values to stay within a certain threshold. However, it is difficult to form a perfect mathematical model for describing behavior of the practical systems since there may be some information (uncertainties) that is not observed. Thus, in this article, we studied the stability of an uncertain linear system with a non-differentiable time-varying delay. We constructed Lyapunov-Krasovskii functionals (LKFs) containing several symmetric positive definite matrices to obtain robust finite-time stability (RFTS) and stabilization (RFTU) of the uncertain linear system. With the controller and uncertainties in the considered system, there exist nonlinear terms occurring in the formulation process. Past research handled these nonlinear terms as new variables but this led to some difficulty from a computation point of view. Instead, we applied a novel approach via Cauchy-like matrix inequalities to handle these difficulties. In the end, we present three numerical simulations to show the effectiveness of our proposed theory.

7 citations

Journal ArticleDOI
TL;DR: This paper presents a control to mitigate these power quality issues in addition to the control of power flow between solar photovoltaic system and non-linear load, using linear quadratic regulator.

4 citations

References
More filters
Journal ArticleDOI
TL;DR: In this paper, the instantaneous power theory was introduced for steady and transient states and for generic voltage and current waveforms, and an example showing how this theory can be used to design and control an active power filter is presented.
Abstract: Conventional active and reactive power theory, valid for the steady-state analysis is reviewed. The instantaneous power theory, introduced by H. Akagi et al. (1983, 1984) is also presented. This instantaneous theory is valid for steady and transient states and for generic voltage and current waveforms. Some examples explaining the physical meaning of the new concepts are presented. By using the concepts of symmetrical components together with the new theory, the powers in an unbalanced system are analyzed, including the zero-sequence instantaneous power. An example showing how this theory can be used to design and control an active power filter is presented. Some simulation results are presented and discussed. >

361 citations

Journal ArticleDOI
TL;DR: In this paper, a current controller for voltage-source inverters in microgrids is proposed to inject a clean sinusoidal current to the grid, even in the presence of nonlinear/unbalanced loads and/or gridvoltage distortions.
Abstract: In this paper, a current-control strategy is proposed for voltage-source inverters in microgrids. The main objective of the proposed controller is to inject a clean sinusoidal current to the grid, even in the presence of nonlinear/unbalanced loads and/or grid-voltage distortions. The repetitive control technique is adopted because it can deal with a very large number of harmonics simultaneously. The proposed current controller consists of an internal model and a stabilizing compensator, which is designed by using the H∞ control theory. It turns out that the stabilizing compensator may be simply an inductor. This leads to a very low total harmonic distortion (THD) and improved tracking performance. In order to demonstrate the improvement of performance, the proposed controller is compared with the traditional proportional-resonant, proportional-integral, and predictive deadbeat controllers. The control strategies are evaluated in the grid-connected mode with experiments under different scenarios: steady-state and transient responses without local loads, and steady-state responses with unbalanced resistive and nonlinear local loads. The proposed controller significantly outperforms the other control schemes in terms of the THD level, with the price of slightly slower dynamic responses.

272 citations


"Power Quality Enhancement Using Lin..." refers background in this paper

  • ...In comparison with conventional controllers, H controller provides better performance by offering low grid current THD even in the presence of non-linear loads, but it has slow dynamics [32]....

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  • ...Several current control techniques are proposed in the literature to integrate the renewable sources in the grid [18]– [32]....

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Journal ArticleDOI
TL;DR: The obtained experimental results show that the proposed adaptive SRF-PLL highly rejects the undesired harmonics even if the fundamental harmonic frequency of a highly polluted grid voltage abruptly varies.
Abstract: The proper operation of grid-connected power electronics converters needs using a synchronization technique to estimate the phase of the grid voltage. The performance of this synchronization technique is related to the quality of the consumed or delivered electric power. The synchronous-reference-frame phase-locked loop (SRF-PLL) has been widely used due to its ease of operation and robust behavior. However, the estimated phase can have a considerable amount of unwanted ripple if the grid voltage disturbances are not properly rejected. The aim of this paper is to propose an adaptive SRF-PLL which strongly rejects these disturbances even if the fundamental frequency of the grid voltage varies. This is accomplished by using several adaptive infinite-impulse-response notch filters, implemented by means of an inherently stable Schur-lattice structure. This structure is perfectly suited to be programmed in fixed-point DSPs (i.e., it has high mapping precision, low roundoff accumulation, and suppression of quantization limit cycle oscillations). The proposed adaptive SRF-PLL has been tested by means of the TI TMS320F2812 DSP. The obtained experimental results show that the proposed synchronization method highly rejects the undesired harmonics even if the fundamental harmonic frequency of a highly polluted grid voltage abruptly varies.

268 citations

Journal ArticleDOI
TL;DR: In this article, a suitable pole placement strategy is proposed, which ensures fulfilling the requirements, which are commonly specified with respect to rise time, overshoot, and proper resonance damping.
Abstract: Design and analysis of PI state space control for grid-connected pulsewidth modulation (PWM) converters with LCL filters based on pole placement approach is addressed. State space control offers almost full controllability of system dynamic. However, pole placement design is difficult and usually requires much experience. In this paper, a suitable pole placement strategy is proposed, which ensures fulfilling the requirements, which are commonly specified with respect to rise time, overshoot, and proper resonance damping. Controller parameter expressions are derived in terms of system parameters and specified poles and zeros. Hence, straightforward controller tuning for a particular system setting is possible. Performance is analyzed by means of transfer function-based calculations, simulations with MATLAB, and experimental tests. Dynamic performance and robustness against grid impedance variations are addressed as well as harmonic rejection capability and other practical issues.

250 citations

Journal ArticleDOI
TL;DR: In this paper, a detailed comparison of voltage-controlled and current-controlled voltage source inverters (VSI) for DGS applications is presented, and the advantages and limitations of each control technique in a single-phase DGS, without incorporating additional hardware and/or extra complex control techniques.
Abstract: Voltage source inverters (VSI) have been widely used in uninterruptible power supplies, unified power flow controllers or unified power quality conditioners, and distributed generation systems (DGS) VSIs are inherently efficient, compact, and economical devices used to control power flow and provide quality supply VSIs can be classified as voltage-controlled VSIs (VCVSIs) and current-controlled VSIs (CCVSIs), depending on their control mechanism In this paper, a detailed comparison of VCVSIs and CCVSIs for DGS applications is presented This paper examines the advantages and limitations of each control technique in a single-phase DGS, without incorporating additional hardware and/or extra complex control techniques Discussions on the concepts, hypotheses, and computer simulations of different VSIs in the presence of different loads and conditions are presented The experimental results confirm the validity of the analysis and simulations outlined The paper provides design recommendations for the use of VCVSIs and CCVSIs in various applications

198 citations


"Power Quality Enhancement Using Lin..." refers background in this paper

  • ...Several current control techniques are proposed in the literature to integrate the renewable sources in the grid [18]– [32]....

    [...]