Comparative Analysis and Performance of DSTATCOM Device Using PI and Second-Order Sliding Mode Control

Proportional and Integral (PI) controllers are usually accustomed for the control operation of Distribution Static Compensator (DSTATCOM) for the distribution system. However, since the system is very nonlinear and subject to numerous disturbances, the PI controlled DSTATCOM cannot offer optimum performance for various operation points. Additional controllers like the Instant Power Theory (IPT) supported fuzzy logic approach is needed for the DSTATCOM to supply adequate dynamic current control and to enhance power quality and stability of the distribution system. This paper presents the planning of fuzzy logic Controllers (FLC) of a DSTATCOM for improving power quality for a distribution system. The IPT based FLC for the DSTATCOM is used for improving the power quality and the dynamic performance of a distribution system is compared with a DSTATCOM controlled IPT based PI controller. The performances of the DSTATCOM controllers are evaluated throughout grid-side currents with linear and non-linear loads of the distribution system. Simulation results show that the DSTATCOM with IPT based FLC will improve the power quality by reducing reactive currents and harmonic currents with higher system dynamic performance than the DSTATCOM with IPT based standard PI controller.

This paper presents the hysteresis controller, based scheme for distribution static compensator (DSTATCOM) for analysis of faults, line-line fault, line to ground fault, single line to ground fault for power quality improvement. DSTATCOM is used for power quality improvement. It provides the deficient reactive power in the distribution system. Conventionally hysteresis controller uses proportional and integral (PI) controller. In this paper, artificial neural network (ANN) and adaptive neuro fuzzy inference system (ANFIS) based DSTATCOM controllers are implemented for the analysis of different faults. This paper also provides the comparison of different faults for ANN and ANFIS based DSTATCOM with the help sequence analyzer. Sequence analyzer is used for the positive, negative and zero sequence analysis of three phase signal. Per unit study of the output voltage is carried out to compare the results of the different faults based on ANN and ANFIS controller. The simulation results show the improved results for the voltage profiles with ANFIS controller. The simulation of the proposed model is done with the help of MATLAB/Simulink software.

This article presents an original motion control strategy for robot manipulators based on the coupling of the inverse dynamics method with the so-called second-order sliding mode control approach. Using this method, in principle, all the coupling non-linearities in the dynamical model of the manipulator are compensated, transforming the multi-input non-linear system into a linear and decoupled one. Actually, since the inverse dynamics relies on an identified model, some residual uncertain terms remain and perturb the linear and decoupled system. This motivates the use of a robust control design approach to complete the control scheme. In this article the sliding mode control methodology is adopted. Sliding mode control has many appreciable features, such as design simplicity and robustness versus a wide class of uncertainties and disturbances. Yet conventional sliding mode control seems inappropriate to be applied in robotics since it can generate the so-called chattering effect, which can be destructive for the controlled robot. In this article, this problem is suitably circumvented by designing a second-order sliding mode controller capable of generating a continuous control law making the proposed sliding mode controller actually applicable to industrial robots. To build the inverse dynamics part of the proposed controller, a suitable dynamical model of the system has been formulated, and its parameters have been accurately identified relying on a practical MIMO identification procedure recently devised. The proposed inverse dynamics-based second-order sliding mode controller has been experimentally tested on a COMAU SMART3-S2 industrial manipulator, demonstrating the tracking properties and the good performances of the controlled system.

06/00918 Experimental and numerical study of three-dimensional flow field in mini-environment: Cheng, C.-S. and Hung, J.-S. Energy and Buildings, 2005, 37, (6), 579–586.

An adaptive neuro-fuzzy inference system (ANFIS) controller is developed and presented in this study to control hybrid energy storage system (HESS) which combines the battery and super-capacitor (SC). The battery compensates the energy requirement for a longer duration while the SC limits the stress on battery caused by the power fluctuations during transient period which alternately gives longer life span for the battery while regulate the DC link voltage constant. The proposed ANFIS controller is being compared for performance with various other controllers including the reinforcement controller based on Q-learning proportional and integral (PI) controller, fuzzy controller and conventional PI controller. Further, the state of charge (SOC) of the battery and SC are monitored in order to decide the required optimal amount of power or energy for the HESS in deficit/excess modes. The results of the simulation, in different loading conditions, indicate that the ANFIS's controller performance for the DC microgrid is superior compared to others.

In this paper, the perfect harmonic cancellation (PHC), unity power factor (UPF) control strategies of distribution static compensator (DSTATCOM) are compared along with a newly proposed control strategy. In the proposed strategy, to get the best power factor, the conductance factors for the compensated load are evaluated for a specified source current total harmonic distortion (THD) limit. The performance of this method along with perfect harmonic cancellation (PHC) and unity power factor (UPF) strategies is evaluated on a distribution system model developed using PSCAD 4.2.1. In the distribution system, harmonic resonance is one of the prime factors for the harmonic propagation. Hence, in damping the harmonic resonance, selection of an appropriate control strategy for the DSTATCOM is crucial and this is verified with a detailed study. The simulation results are presented to show the performance of these strategies in load compensation and damping the harmonic propagation in the distribution system.

Solar power generation is intermittent in nature. It is nearly impossible for a photovoltaic (PV) system to supply power continuously and consistently to a varying load. Operating a controllable source like a fuel cell in parallel with PV can be a solution to supply power to variable loads. In order to coordinate the power supply from fuel cells and PVs, a power management system needs to be designed for the microgrid system. This paper presents a power management system for a grid-connected PV and solid oxide fuel cell (SOFC), considering variation in the load and solar radiation. The objective of the proposed system is to minimize the power drawn from the grid and operate the SOFC within a specific power range. Since the PV is operated at the maximum power point, the power management involves the control of SOFC active power where a proportional and integral (PI) controller is used. The control parameters of the PI controller Kp (proportional constant) and Ti (integral time constant) are determined by the genetic algorithm (GA) and simplex method. In addition, a fuzzy logic controller is also developed to generate appropriate control parameters for the PI controller. The performance of the controllers is evaluated by minimizing the integral of time multiplied by absolute error (ITAE) criterion. Simulation results showed that the fuzzy-based PI controller outperforms the PI controller tuned by the GA and simplex method in managing the power from the hybrid source effectively under variations of load and solar radiation.

Large penetration of PV in a microgrid connected distribution system impacts the weak utility distribution system by creating various power quality (PQ) problems such as voltage sag or swell, unbalance, harmonics and DC current injection etc. These power quality (PQ) issues and they are broadly classified as current related PQ issues and voltage related PQ issues. The current related issues are mitigated by one of the custom power device connected in parallel namely distribution static compensator (DSTATCOM), by operating in current controlled mode (CCM). The dynamic voltage restorer (DVR) is another custom power device (CPD) for mitigating voltage related PQ problems. It is reported in literature that, a suitable modification of a DSTATCOM can achieve the capability to compensate voltage disturbances also. A multiple functions of DSTATCOM is thus achieved by operating the device so as to mitigate the current and voltage related PQ issues. Thus a multi-functional control strategy allow DSTATCOM to compensate voltage and current related PQ problems. This paper presents a hybrid DSTATCOM which can be used in highly PV penetrated distribution system to control the voltage and current related PQ issues. The topology uses a suitably designed foreign inductor, connected between the grid and load. A dynamic reference load voltage generation algorithm using instantaneous symmetric component theory (ISCT) is presented. The simulation is done with real time voltage level using MATLAB/SIMULINK.

<p class="Abstract"><span lang="EN-US">Voltage sags are the most common power quality disturbances in electrical facilities. It may cause malfunction in sensitive equipment and process interruption. The distribution static compensator (DSTATCOM) is a device that can compensate voltage sags by injecting reactive power into distribution system. This paper shows the influence on voltage sags characteristics by the presence of twelve-pulse DSTATCOM in the modified IEEE-13 distribution system. The analysis is performed by means of a random generation of disturbances using a MATLAB routine to identify the critical buses of the test system. Further, the DSTATCOM model taking advantage of the available elements from ATP/EMTP software is described. Simulations show that when DSTATCOM is placed directly to affected bus it is possible to obtain a complete mitigation of the voltage sag. Finally, the relation between the reactive power injected by DSTATCOM, the type of voltage sag and the location of affected bus is considered.</span></p>

An increasing growth of non-linear load in the three-phase four-wire distribution system, results in various power quality problems in the distribution system. Custom power devices (CPD) have been evolved to solve the power quality problems in the distribution system. Among the various custom power devices, Distribution Static Compensator (DSTATCOM) is one of the effective solutions for solving the power quality problems. This paper reveals about Distribution static compensator (DSTATCOM) for balancing of source currents, harmonic mitigation and neutral current compensation in three-phase four-wire distribution system. A synchronous reference frame (SRF) theory is projected for the control of DSTATCOM. Four-leg voltage source converter (VSC) with a dc capacitor is used as four-wire DSTATCOM. Here DSTATCOM is operated in load compensation mode. The first three-legs are used for balancing of source current and harmonic mitigation and the fourth leg is used for neutral current compensation. The compensation performance of DSTATCOM using the proposed control strategy is demonstrated using simulation results obtained from MATLAB/SIMULINK.

The main goal of vehicle active suspension system is to upgrade the ride quality and stability of heavy duty vehicle (HDV) regardless of road surface. The mathematical modelling of HDV with two degrees of freedom is developed and simulated in MATLAB/Simulink environment. The simple and effective control techniques such as proportional integral and derivative (PID) controller, sliding mode controller (SMC) and fractional order sliding mode controller (FOSMC) are designed to detach the vibration from the passenger under step, sinusoidal and random road profile. Literature reveals that the FOSMC can eliminate steady state error and chattering effect unlike SMC and PID. The dynamic analysis of designed controllers is examined in terms of time domain, frequency domain and ride comfort analysis as per ISO 2631. The stability of SMC and FOSMC is confirmed by Lyapunouv stability for three different road profiles. The FOSMC shows satisfactory simulation results than SMC, PID and passive suspension system in reducing suspension deflection and body acceleration of HDV to upgrade the ride quality. Further, the efficacy of proposed FOSMC is proved by comparing the simulation results against existing results of PID controller.

Voltage sag is considered to be the most serious problem of power quality. It is caused by faults in the power system or by the starting of large induction motors. Voltage sag causes about 80% of the power quality problems in power systems. One of the main reasons for voltage sag is short circuit fault, which can be compensated for by a distribution static compensator (DSTATCOM) as an efficient and economical flexible AC transmission system (FACTS) device. In this paper, compensation of this voltage sag using DSTATCOM is reviewed, in which a sliding mode control (SMC) technique is employed. The results of this control system are compared with a P+Resonant control system. It will be shown that this control system is able to compensate the voltage sag over a broader range compared to other common control systems. Simulation results are obtained using PSCAD/EMTDC software and compared to that of a similar method.

This article proposes new and simplified unit templates instead of standard phase locked loop (PLL) for Synchronous Reference Frame Theory Control Algorithm (SRFT). The extraction of synchronizing components (sinθ and cosθ) for parks and inverse parks transformation using standard PLL takes more execution time. This execution time in control algorithm delays the extraction of reference source current generation. The standard PLL not only takes more execution time but also increases the reactive power burden on the Distributed Static Compensator (DSTATCOM). This work proposes a unit template based SRFT control algorithm for four-leg insulated gate bipolar transistor based voltage source converter for DSTATCOM in distribution systems. This will reduce the execution time and reactive power burden on the DSTATCOM. The proposed DSTATCOM suppress harmonics, regulates the terminal voltage along with neutral current compensation. The DSTATCOM in distribution systems with proposed control algorithm is modeled and simulated using MATLAB using SIMULINK and Simpower systems toolboxes.

The paper seeks analysis of unbalance radial distribution system (URDISY) with distributed generator (DG) and distribution static compensator (D-STATCOM). The paper's main objectives are optimal allocation DG and D-STATCOM through a metaheuristic technique known as Atom Search Optimization (ASO) algorithm, intending to provide real and reactive power support by enhancing voltage profile reducing total real and reactive line losses. Also, impact of DG and D-STATCOM on total savings in cost of energy losses. Further, different loading conditions and load growth model are considered for better planning of the power distribution system. The DG and D-STATCOM power factors are considered unity and zero pf lag, respectively. The results are obtained for standard 25-bus URDISY using simulation in MATLAB.

This paper deals with a software phase locked loop (SPLL) based control algorithm for a three phase distribution static compensator (DSTATCOM) for power quality improvement under linear/nonlinear loads in a distribution system. In this control approach, amplitude of fundamental active and reactive power components of load currents is extracted for estimation of reference source currents. The DSTATCOM is modeled in the Matlab environment using Simulink and Sim Power System (SPS) toolboxes. Matlab based developed model of DSTATCOM is used to simulate its performance. Simulated performance of DSTATCOM is found satisfactory under time varying and unbalanced linear and nonlinear consumer loads.