Current Related Power Quality Issues Research Articles

Reduced Sensor Based Control of PV-DSTATCOM with Switch Current Limiting Scheme

The work delineated in this paper deals with the reduced sensor-based operation of PV-DSTATCOM (Photovoltaic distribution static compensator) focusing on the voltage source inverter (VSI) switch current limiting control. In this study, the soft computing technique of PV-DSTATCOM control based on the variable leaky least mean square (VLLMS) algorithm is modified to incorporate both reduced sensor and switch current limiting schemes. DSTATCOM is predominantly introduced to improve current related power quality issues by providing non-real power (i.e., the reactive and harmonic component) of the load demand. However, during uncertain increase in the non-real power requirement at the load end due to sudden change in the load demand or any other transient conditions, the non-real current injected by the DSTATCOM may increase to a level which is beyond the current handling capacity of the DSTATCOM switches. As a consequence, the switches may become permanently damaged and, subsequently, the performance of the DSTATCOM will deteriorate. Hence, the current through the VSI switches can be limited by controlling the amount of non-real power flow from the DSTATCOM. During this transient or high current condition, the control transits from power quality improvement mode to protection mode. As a result, unity power factor operation at P.C.C (common point of coupling) is compromised for that period or few cycles of transient condition. Moreover, the efficient operation of any control demands proper information about the current and the voltage of the system, which are determined by sensors. However, the faults in these sensors may deteriorate the controller performance and degrade the system efficacy. Therefore, to mitigate this issue, the numbers of measurement units are reduced i.e., the measurement of current in only two phases for load as well as grid, and the measurement of line voltages using two voltage sensors instead of three sensors for each phase. The reduction of sensors is accomplished without compromising the controller efficiency. Further, the system is studied using MATLAB/Simulink under different condition of steady- state, varying solar irradiance, increasing load above rated capacity.

The Improved Unified Power Quality Conditioner with the Modular Multilevel Converter for Power Quality Improvement

Nowadays, researchers focus on the modular multilevel converter (MMC), due to its modularity structure, effective sharing of voltages among the submodule switches, and betterment in the quality of the voltage and current waveforms. First, the conventional unified power quality conditioner is developed with two level voltage source converters connected back-to-back, which are proposed to mitigate both the voltage and current related power quality problems. Later, to improve the performances (voltage sag, swell, current harmonics, etc.) of the conventional method, multilevel inverters are used. In this paper, a modified unified power quality conditioner based on a modular multilevel converter is implemented to mitigate the voltage and current related power quality issues. The design of the MMC is very simple with a modular structure, and it also improves the performance of the system compared to the conventional methods. In this proposed topology, the voltage related compensation is implemented with a seven-level MMC, and the current compensation is achieved with a reduced four switch voltage source inverter. The developed system is simulated in the MATLAB platform, and results are validated by hardware implementation with a FPGA controller. It is observed that the developed system has less % of total harmonic distortion and reduction in voltage sag as per the prescribed IEEE 519–2014 standards and practices.

A Nonlinear Controller for Neutral Point Piloted (T-Type) Multilevel Inverter-Based Three-Phase Four-Wire DSTATCOM

In recent times, neutral point piloted (NPP) or half-leg T-type multilevel inverter (MLI) becomes a promising topology for medium-voltage high-power applications. This T-type MLI is the best substitute for diode clamped multilevel inverter (DCMLI) due to its simple structure and absence of clamping diodes. However, the neutral point voltage control or dc bus capacitors' balance of NPP T-type MLI is a challenging task. Therefore, this paper presents a nonlinear sliding mode controller (SMC) for dc-link voltage balance and reference current control in distribution static compensator (DSTATCOM). For this, a three-level T-type MLI-based three-phase four-wire DSTATCOM is considered to eliminate current-related power quality issues such as harmonics, reactive power, load unbalance, and neutral current. The proposed NPP T-type-based DSTATCOM is compared with DCMLI and active DCMLI-based DSTATCOMs in terms of switching losses and cost. Simulation studies are carried out in MATLAB Simulink environment and further corroborated with experimental studies. Furthermore, the ability of the proposed SMC-based controller is compared with the PI controller under different operating conditions.

Analysis of Levenberg Marquardt - ANN based reference current generation for control of shunt active power filter

Shunt active power filter (SAPF) is an inevitable solution that needs to be installed by industrial consumers to prevent the power quality issues due to the non-sinusoidal currents drawn by non-linear loads. SAPF provides harmonic current compensation and reactive power management to eliminate the current related power quality issues. Various reference current generation schemes such as d-q theory, instantaneous reactive power theory, discrete Fourier transform, PI controller, fuzzy logic etc. are reported. Artificial neural network (ANN) is an emerging concept in SAPF for reference current generation. In this paper, detailed analysis of Levenberg Marquardt–feedforward ANN based reference current generation scheme for the control of SAPF is presented. This paper mainly focuses on successful implementation of Levenberg Marquardt algorithm for training the feedforward ANN network for reference current generation with different non linear and unbalanced load condition. Performance analysis of Leven Marquardt – ANN based reference current generation for the control of SAPF under different operating condition is carried out in MATLAB/SIMULINK platform.

Recent Trends in Power Quality Improvement: Review of the Unified Power Quality Conditioner

The electrical power sector is currently focusing on power quality (PQ) issues and their mitigation. Industrial automation and the use of power electronic converters for the integration of distributed generation create various PQ problems. This necessitates PQ enhancement, which in turn helps to improve the life span of the equipment as well as the reliability of supply for feeding critical loads within the system. This paper presents a comprehensive review of the Unified Power Quality Conditioner (UPQC) and its widespread application in the distribution system. The UPQC belongs to the family of active power filters. It contributes to the alleviation of voltage and current-related PQ issues along with power factor correction and the integration of renewable energy systems in the distribution network. This paper discusses various topologies, compensation methods, control theories, and the technological developments in recent years. More than 160 research papers have summarized the features of UPQC for further applications. Based on the outcomes of the investigation, the future direction of the UPQC is discussed. This paper is expected to play a major role in guiding research scholars in the application of the UPQC.

Application of Fuzzy Controller for Improvement of Power Quality using UPQC

Generally, one of the custom power device in FACTS called unified power quality conditioner, which is used to compensate the voltage and current-related Power Quality issues in the distribution systems. The proposed UPQC technology have an advantage of reduced dc-link voltage without compromising its compensation capability. This new method also helps to meet the requirement of dc-link voltage for the shunt and series active filters of the UPQC. This type of topology has a capacitor in series with the interfacing inductor across the shunt active filter for filtering purpose, and the system neutral is also considered and directly connected to neutral of distribution system avoid the requirement of the fourth leg in the voltage source inverter. This paper also presents a concept for improving power quality of a power distribution system such as an FUZZY logic controller along with the UPQC control strategy. The simulation results are compared for both conventional PI controller and FUZZY controller.

Model predictive control with constant switching frequency for four‐leg DSTATCOM using three‐dimensional space vector modulation

In this study, model predictive control (MPC) with constant switching frequency is proposed for four-leg distribution static compensator (FL-DSTATCOM) to compensate the current related power quality issues. MPC techniques having many advantages compared to conventional pulse width modulation and hysteresis control techniques. In MPC, the future behaviour of the controlled variable is predicted using the model of the system and a cost function is formed using reference and predicted variable. MPC for DSTATCOM applications consider the difference between the reference and actual DSTATCOM current as a cost function and selects the switching state which minimises the cost function. However, while using MPC, the switches of DSTATCOM operate in variable switching frequency and sometimes the values are also very high. Due to this reason higher switching losses, unequal stress appear across the inverter switches and it also reduces the lifetime of the switch. Therefore, in this study, the concept of three-dimensional space vector modulation is adopted to achieve a constant and user-defined switching frequency MPC for FL-DSTATCOM to conquer the limitations of conventional variable switching frequency MPC. The validation of the proposed work is achieved using simulation and experimental studies.