Indirect Current Control Research Articles

Simulation and real time implementation of shunt active power filter for power quality enhancement using adaptive neural network topology

With the rise in non-linear loads, the need for a veracious power filter to alleviate voltage and current harmonics for meeting power quality has been a challenging requirement of the existing power system. This paper presents a systematic approach to improve power quality with a shunt active power filter (SAPF). The controller consists of a neural network approach to enhance the switching control of SAPF under dynamic and non-linear loading conditions. DC link voltage has been regulated using proportional-Integral (PI) control. To extract reference current, instantaneous-reactive power (IRP) theory has been used. IRP theory employing indirect current control strategy provides reference source current signals as well as regulated PWM switching signals for hysteresis control. An ADALINE network has been devised to extract fundamental signals from the polluted supply voltage. The model has been simulated on the MATLAB®/Simulink platform and validated by SAPF prototype in the laboratory using the TMS320F28335 floating-point DSP controller.

Stability Modeling and Analysis of Grid Connected Doubly Fed Wind Energy Generation Based on Small Signal Model

Stable wind power generation can ensure the quality of power transmitted by the grid. The application of large-scale grid-connected wind power systems will induce problems such as grid oscillation and frequency instability. In order to solve the problem of abnormal power system interaction caused by large-scale wind power access and improve the stability of grid-connected doubly-fed wind power generation, this paper proposes a stability modeling analysis of grid-connected doubly-fed wind power generation based on small signal model. First, the operating conditions of the grid-connected DFIG are analyzed, and the vector diagrams of the three operating conditions are given. When the grid-connected DFIG is in the super-synchronous working state, the sub-synchronous working state and the synchronous working state. According to the operating conditions of the grid-connected doubly-fed generators, the grid-connected doubly-fed wind power generation system is linearized. According to the relationship between the actual speed and the synchronous speed of the doubly-fed generator, the operating conditions of the doubly-fed generator are analyzed. By introducing the small-signal model, we analyze the small-signal of the grid-connected doubly-fed wind power generation system. The indirect current control circuit is used to perform reactive power compensation for grid-connected doubly-fed wind turbines. By calculating the reactive power loss of the grid-connected DFIG and the reactive power loss of the transmission line, the compensation capacity of the grid-connected DFIG is calculated. The transient voltage of the wind turbine is controlled by the rotor-side frequency converter, combined with the pitch angle control model. So far, this paper has realized the modeling analysis of grid-connected doubly-fed wind power generation stability. The simulation results show that the modeling analysis in this paper is reasonable for the small-signal analysis results of the stability of grid-connected doubly-fed wind power generation. In the rotor voltage simulation test, after the oscillation occurs for 1 s, the model starts to simulate and eliminate the fault. During the simulation period of 0.7 s∼1.0 s, the output voltage of the converter decreased to 168 V, and the voltage waveform did not fluctuate greatly after 1.0 s. The experimental results show that this method can improve the stability of grid-connected doubly-fed wind power generation.

Student psychology and social group optimizations based modified synchronous reference frame control topology for PV-DSTATCOM

This paper proposes the design of a modified synchronous reference frame (SRF) (MSRF) technique while incorporating student psychology based optimization (SPBO) and social group optimization (SGO) algorithms for solar photovoltaic (PV) and battery embedded distribution static compensator (DSTATCOM) for three-phase grid-tied system. For maximum power point tracking, the SPBO is used. The proposed MSRF controller provides satisfactory performance under different real-time cases. In case of night condition, the dc bus voltage is slightly reduced. MSRF may provide system stability under different faults. Due to the use of MSRF controller, the total harmonic distortion (THD) of grid current is 1.30% and the THD value is reduced by 9.72%, 23.98%, 26.14%, 66.23%, 36.59%, 38.97%, 56.38%, 30.85%, 41.44%, 75.05%, 77%, and 95.29%, respectively, as compared to the other techniques surfaced in the recent state-of-the-art literature such as (a) IT-2 fuzzy logic control (FLC), (b) type-I FLC, (c) PI control, (d) sliding mode control (SMC), (e) fuzzy and SMC, (f) indirect current control (ICC), (g) modified ICC, (h) SRF with teaching learning based optimization and SGO combination, (i) SRF with firefly and SGO combination, (j) SRF with particle swarm optimization and SGO combination, and (k) SRF control and without DSTATCOM.

Power quality improvement of wind energy system using energy storage model and DSTATCOM

Nowadays power crises in different countries are observed and the main cause of the power crisis is the huge gap between the supply and demand of electricity, renewable energy sources are identified as an alternative to overcome the power crisis gap. Renewable wind energy is the most promising energy source. Increasing the integration of wind energy into the grid causes the exploitation of power quality. Hence there is a need to deal with this issue. In this case, supercapacitors and custom power devices are introduced as smart energy storage devices in grid-connected wind energy systems for power quality enhancement features. The indirect current control scheme has interfered with custom power devices based on DSTATCOM. The optimal MATLAB-based smart energy storage model and hardware results are compared and validated. power quality improvement feature of grid-connected wind energy system using DSTATCOM is highlighted. The main aim of this study is to determine and interface the optimistic energy storage device into grid connected wind energy system. So that the stability of the wind energy system is to be maintained and also able to enhance the overall efficiency of the wind energy system.

Modified CCF Based Shunt Active Power Filter Operation With Dead-Band Elimination for Effective Harmonic and Unbalance Compensation in 3-Phase 3-Wire System

The effect of reduction in the terminal voltage of a grid-tied inverter together with minimization in total harmonic distortion (THD) of terminal voltage and current, in the presence of dead-band in the switching remains always challenging for the researchers. With high switching frequency, this issue increases by many folds. The grid-tied inverter used for harmonic compensation acts as a shunt active power filter (SAPF). The implementation of the dead-band elimination technique is based on output current polarity detection, suffers from multiple zero-crossing due to the generation of high frequency switching harmonics during SAPF operation. This paper deals with a dead band elimination methodology together with harmonic compensation using SAPF under non-linear and unbalanced loading conditions. Here, SAPF uses a dual fundamental component extraction (DFCE) scheme with modified complex coefficient filter (MCCF) to extract fundamental components for reference current generation to implement an indirect current control PWM scheme. MCCF extracts fundamental components even in the presence of dc offset and unbalancing at the input. For incorporating dead-band elimination in control, exact polarity detection is done separately through SAPF output current estimation using sensed load current, and modified CCF computed reference source current. Since the estimated SAPF output current contains no high-frequency switching harmonics, the dead-band elimination technique can be correctly implemented. To synchronize the zero-crossing of the estimated and actual SAPF current, an adaptive delay control is used. The proposed MCCF based control logic’s performance together with the dead-band elimination technique is validated for SAPF operating under non-linear, unbalance, and dynamic load conditions. The proposed dead-band elimination scheme based SAPF model is developed and simulated using MATLAB/ SIMULINK. The simulation results show a significant reduction in source current harmonics due to the elimination of odd harmonic injection into the system by incorporating dead-band elimination in SAPF operation. The real-time simulation of the proposed method is also validated using OPAL-RT OP4510 real-time platform.

Indirect Current Control Method Based on Reference Current Compensation of an LCL-Type Grid-Connected Inverter

NPC (neutral point clamped converter) is widely used in medium- and high-voltage grid connection because of its small power devices, simple overall structure, and easy control. This paper presents an improved indirect current control strategy for an LCL-type NPC. Firstly, the reference current is compensated to suppress the resonant peak of the LCL filter and improve the tracking accuracy of the output current. Then, with the relationship between state variables, the control structure is optimized by introducing the non-PLL control method, so that the sensors are reduced to only two sets. Finally, the traditional differential operator is improved to compensate the calculation delay in digital control. The experimental results show that the amplitude of thee grid-connected current is consistent with the reference value, the phase deviation is reduced from 7° to about 1°, and the transient response time is shortened to 1/3 of that of the traditional method.

Comparative Analysis in the Case of Indirect Current Control in a Shunt Active Filtering System

In this paper, the performance of a three-phase four wire shunt active power filter (APF) using indirect current control with active load current calculation was compared with that corresponding to using indirect current control with prescribed current calculation from the voltage controller. It is clear that, under balanced and sinusoidal voltage conditions, these two methods give similar results. The variant of the indirect current control with prescribed current calculation from the voltage controller has the advantage of simplicity, but exhibits increased sensitivity to voltage ripples on the compensation capacitor, as they are reflected in the output of the voltage controller. The whole system was modeled using MATLAB-SIMULINK software. The simulation results demonstrate the applicability of both methods for APF control.

Power quality improvement in a photovoltaic based microgrid integrated network using multilevel inverter

Abstract The increasing use of power electronics devices as well as the integration of renewable source-based microgrids (MG) has seriously affects the power quality (PQ) of the three-phase power system. Therefore, for the improvement of PQ, it is required to reduce the total harmonics distortion (THD) in the utility network. In this work, the improvement of PQ is discussed in a photovoltaic (PV) based MG integrated three-phase system using a three-level H-bridge (3LHB) multilevel inverter (MI). The MI is used for compensating the source current harmonics and reducing the THD by meeting the IEEE standard guidelines. Besides, the proposed model helps manage the reactive power with control of DC link bus voltage through the PV system. The proposed model is helpful not only in reducing the harmonics but also in providing additional active power to the load if any electrical disturbances occur on the grid side. The maximum power point tracking (MPPT) technique employed in PV is of an improved form of Perturb and Observe (P&O). Further, the reference current generation is derived using the direct current control (DCC) and indirect current control (ICC) techniques. The MG integrated MI is investigated in both DCC and ICC method using three different DC bus voltage controllers; proportional-integral (PI), fuzzy logic controller (FLC), and fuzzy sliding mode control (FSMC). The proposed microgrid integrated system is analyzed with the MATLAB/Simulink tool.

Improving Power Quality by a Four-Wire Shunt Active Power Filter: A Case Study

This paper presents the use of a three-phase four-wire shunt active power filter to improve the power quality in the Department of Industrial Electronics of a large enterprise from Romania. The specificity is given by the predominant existence of single-phase consumers (such as personal computers, printers, lighting and AC equipment). In order to identify the power quality indicators and ways to improve them, an A-class analyzer was used to record the electrical quantities and energy parameters in the point of common coupling (PCC) with the nonlinear loads for 27 h. The analysis shows that, in order to improve the power quality in PCC, three goals must be achieved: the compensation of the distortion power, the compensation of the reactive power and the compensation of the load unbalance. By using the conceived three-leg shunt active power filter, controlled through the indirect current control method in an original variant, the power quality at the supply side is very much improved. In the proposed control algorithm, the prescribed active current is obtained as a sum of the loss current provided by the DC voltage and the equivalent active current of the unbalanced load. The performance associated with each objective of the compensation is presented and analyzed. The results show that all the power quality indicators meet the specific standards and regulations and prove the validity of the proposed solution.

Performance improvement of shunt active power filter under variable grid frequency condition using complex coefficient filter‐frequency locked loop

SummarySynchronizing methodology for shunt active power filter (SAPF) based on the resonant controller using generalized integrator (GI) in the stationary reference frame is of great interest for researchers now a day. In this paper, a phase synchronizing technique based on the complex coefficient filter (CCF) embedded with a frequency locked loop (FLL) is proposed for the fundamental active and reactive component extraction of load current and unit template generation from grid supply. The proposed CCF‐FLL–based control works effectively under varying grid frequency, distorted and unbalance grid voltage conditions to generate the reference source current at a unity power factor for proper harmonic compensation using an indirect current control method. In this work, a detailed mathematical modeling for development of control logic for CCF‐FLL is done, and its feasibility with the bode plot is also confirmed. Simulation for SAPF is performed using both CCF and CCF‐FLL–based control strategy separately to judge the performance of each. Simulation confirms that the proposed CCF‐FLL based control is capable of maintaining the source current with low total harmonic distortion (THD) as per the IEEE‐519 standard with the nonlinear load. The effectiveness of the proposed controller for desired harmonics compensation is also validated through real‐time simulation using OPAL‐RT OP4510 platform.

Experimental investigations on three-phase interleaved SAPF with modified indirect current control algorithm

This paper presents a novel inverter topology, called three-phase interleaved inverter for three-phase shunt active power filter (SAPF). This proposed topology is used for compensating current harmonics, reactive power to improve the power factor of the system. In addition, it eliminates the shoot-through problem which is the hazardous problem in conventional voltage source inverter (VSI)-based SAPF. This proposed topology uses reference current generation techniques to control the flow of compensating currents and reactive power. The existing feed forward control techniques results in switching notches and distortions in the reference source current, hence, poor harmonic compensation. Modified indirect current control (MICC) technique is implemented in this paper to generate a reference current without distortions. Therefore, no switching notches and ripples present in the source current, hence, the source current %THD will be improved. The proposed system is modelled by using MATLAB®/Simulink software to test its performance. Also, a laboratory prototype has been designed and developed using dSPACE1104 controller to validate the simulation results. The test results show the viability of the control algorithm and performance of the proposed interleaved inverter in power quality applications.

Experimental investigations on three-phase interleaved SAPF with modified indirect current control algorithm

This paper presents a novel inverter topology, called three-phase interleaved inverter for three-phase shunt active power filter (SAPF). This proposed topology is used for compensating current harmonics, reactive power to improve the power factor of the system. In addition, it eliminates the shoot-through problem which is the hazardous problem in conventional voltage source inverter (VSI)-based SAPF. This proposed topology uses reference current generation techniques to control the flow of compensating currents and reactive power. The existing feed forward control techniques results in switching notches and distortions in the reference source current, hence, poor harmonic compensation. Modified indirect current control (MICC) technique is implemented in this paper to generate a reference current without distortions. Therefore, no switching notches and ripples present in the source current, hence, the source current %THD will be improved. The proposed system is modelled by using MATLAB®/Simulink software to test its performance. Also, a laboratory prototype has been designed and developed using dSPACE1104 controller to validate the simulation results. The test results show the viability of the control algorithm and performance of the proposed interleaved inverter in power quality applications.

A Comprehensive Study of Harmonic Pollution in Large Penetrated Grid-Connected Wind Farm

Novel grid code allows heavy penetration of wind electric power into the grid which leads to new challenges of power quality like harmonic pollution in variable speed wind turbines with asynchronous generator. The article provides an analysis of the existing methods for identifying wind farm contribution to harmonic distortion at a point of common coupling. The considered methods do not allow correct and fair determining of the source of harmonic distortions, or they have limited application and difficulties in implementation. The paper proposes new methods for determining the source of high harmonics. A wind farm model is prepared using MATLAB software, and harmonic analysis is described for different wind velocities. Causes of harmonics generation in wind farm and harmonics pollution mitigation by DSTATCOM modeling with unbalanced grid disturbance of grid side wind mill inverter have been mentioned. The custom power device (CPD) is developed based on nature of harmonics and interface with grid-connected wind farm to enhance the power quality of wind farm. Results obtained from MATLAB-based harmonic analyses are compared with practical case study results that have been presented as per IEEE standard 519-1992, IEC 61000-2-2 and EN 50160 standard harmonic limits. Identified indirect current control scheme of custom power device can be supported to uncertainty analysis.

Assessment of Direct and Indirect Current Control Techniques Applied to Active Power Filters

Background: In this paper, an assessment of active power filter (APF) performance is presented under direct and indirect current control schemes through on-line compensation theory. Methods: Conventional Direct Current Control (DCC) measures both load current and filter current beside source and DC-link voltages, while Indirect Current Control (ICC) measures only source current beside voltage measurements. Both DCC and ICC control algorithms are implemented using 80C196KC low-cost microcontroller. Results: The performance parameters of APF are compared under two methods, and it is assigned that ICC gives a better performance with lower cost due to reduced number of sensors. The DC-link output voltage is controlled through simple PI-controller, and the PWM switching signals required by APF power circuit is obtained by hysteresis current controller. Conclusion: The comparative simulation and experimental results exhibit that performance of APF due to ICC scheme is superior than DCC one.

Adaptive notch filter under indirect and direct current controls for active power filter

This study presents the implementation of adaptive notch filter (ANF) as reference signal extraction for shunt active power filter (APF) in indirect current control (ICC) and direct current control (DCC) modes for three phase system. The ANF functions to filter the signal that inputted to it by producing a fundamental signal and harmonics signal. The advantage of applying the ANF algorithm is based on its simple design that giving the ANF advantages to be utilize in microcontroller. The performance of the ANF is validated though MATLAB simulation in ICC dan DCC configurations. Based on the simulation results, the ANF is capable to work efficiently for both ICC and DCC modes, but in term of efficiency, the ICC mode is clearly showing a better harmonics mitigation result. Base on the result also it shown that the ANF is capable of mitigate the harmonics below the standard required by the IEEE 519-92. The application of ANF is useful to be applied due to its simple design and filtering method.

Performance enhancement of shunt active power filter with the application of an adaptive controller

In this study, an adaptive controller is proposed for shunt active power filter (SAPF) to improve the harmonic compensation performance. The proposed controller forces the source current to become sinusoidal, with less total harmonic distortion and also maintained in phase with the supply voltage. The merits of modified adaptive controller over existing controller are verified in terms of harmonic compensation ratio factor for various perturbations of load and filter parameters. The eficacy of the proposed indirect current control with model reference adaptive controller (ICC-MRAC) control approach is tested by comparing the existing indirect current control with propertional–integral controller (ICC-PI) with the ICC-MRAC algorithm and then justified through laboratory prototype studies followed by using dSPACE 1104. It is observed from the result of implementation that the proposed controller-based SAPF performs superior than the existing ICC-PI in terms of robustness, adaptability, reliability and flexibility to various grid perturbations, such as harmonics, noise etc. Thus, the improvement occurs in power quality is due to the perfect harmonic rejection from current.

Performance of three-phase three-wire cascaded H-bridge multilevel inverter-based shunt active power filter

<span lang="EN-US">Multilevel inverter (MLI) becomes more significant in Active Power Filter (APF) application due to capability to its produce low harmonic output current in which at the same time improving performance of APF. Among the topologies of MLI, Cascaded H-Bridge (CHB) is the most popular topology with less power devices requirement and simple design. MLI CHB is also capable to produce possible output voltage at twice of the number of DC source which in this case of APF is the best suited topology to replace with the conventional six -step inverter. This paper presents the performance of three- phase three-wire CHB MLI used in Shunt Active Power Filter (SAPF) based on Direct Current Control (DCC) and Indirect Current Control (ICC) schemes. Both schemes are developed and verified in MATLAB/Simulink. The simulation results show that both current control algorithms are capable to mitigate load current with Total Harmonic Distortion below than the permissible value based on IEEE 519 standard.</span>

Integration of wind power generation through an enhanced instantaneous power theory

This study deals with the operation of the wind power generation system (WPGS) having active filter capabilities using the grid-interfacing converter (GIC) control approach. A novel current decomposition technique based on enhanced instantaneous power theory (EIPT) is suggested for controlling the GIC to realise an improved power quality (PQ) in WPGS and to provide the requisite reactive power support. To reduce the sluggish response of the numerical filters, a novel mathematical average algorithm is proposed. Furthermore, to reduce the non-linear load effects at GIC, a 13-level reduced switch multi-level inverter (RSMLI) is integrated. Real-time application point of view in the proposed approach, to improve the GIC performance, a novel indirect current control (ICC) technique-based EIPT approach is proposed. ICC technique is used to decompose the power component into a much more detailed component by which it is easier to cancel out the non-linear components and make the system more flexible and reliable for practical applications. The rotor interfacing converter control approach is used to attain the optimum power. Considering different test conditions, the performance of the proposed EIPT-based 13-level RSMLI approach is investigated through MATLAB/Simulink software.

High Buck in Buck and High Boost in Boost Dual-Mode Inverter (Hb2DMI)

The application of the dual-mode time-sharing technique in novel transformerless photovoltaic (PV) inverters is proposed and investigated. The simultaneous high step-down or high step-up conversion with 97.6% peak efficiency and injected current with total harmonic distortion <; 2% are achieved. The leakage current problem, which is a main concern with the transformerless PV inverters, is around 20 mA. The indirect current control, especially at transition of modes of operation is highly improved by utilizing a fast dead-beat control scheme. The working principles of the proposed converter show that the step-down and the step-up voltage gains are (D/(1-D)) <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and D/(1-D) <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , respectively. Furthermore, a 1 kW, 220 VAC and 200 VDC experimental prototype is implemented to confirm the theoretical achievements.

A Self-Adaptive Controller for Inverter With Seamless Transfer and Automatic Pre-Synchronization Capability

A self-adaptive controller is proposed to operate inverter in both grid-connected (GC) state and stand-alone (SA) state and ensure seamless transfer between them without reconfiguring the control structure. The controller is mainly composed of phase-locked-loop (PLL) and two cascaded control loops. The role of PLL is not only to estimate the frequency but also to generate the reference of voltage loop. When the grid is normal, the reference and the feedback value of voltage loop are always equal and the proposed controller accurately regulates the grid current of inverter. When islanding occurs, the inverter can automatically convert from current control mode to voltage control mode without critical islanding detection. The self-adaptive controller has several advantages. First, compared with direct current control, it can operate in both strong and weak grid conditions. Second, its dynamic performance in the GC state is much better than that of indirect current control. Third, when the grid returns to normal, the pre-synchronization of inverter's output voltage and grid voltage can be achieved automatically without any extra control algorithm. Finally, simulation and experimental results are provided to verify the effectiveness of proposed self-adaptive controller.