Indirect Current Control Technique Research Articles

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.

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.

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.

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.

Recursive Digital Filter Based Control for Power Quality Improvement of Grid Tied Solar PV System

This article deals with the implementation of a control approach for an active power transfer between solar photovoltaic (PV) array and the grid/ load along-with power quality (PQ) improvement by eliminating harmonics and compensating reactive power required by the load in the distribution network. The PQ problems at the point of intersection, are increasing preeminently with respect to voltage and current harmonics due to integration of renewable sources. The recursive digital filter control implemented here for PV grid interfaced system is efficient in improving PQ indices by operating round the clock and ensuring power transfer between utility grid and connected loads. The prominence of the control algorithm lies in the efficient switching of voltage source converter (VSC), by generating reference grid currents, which are obtained through indirect current control technique. The recursive digital filter is utilized for processing the load currents and extracting the active power component of them. These active power components of load currents are used for generating the reference grid currents in this system. A prototype of the system is developed in the laboratory and its performance is studied for varying loads, changing solar insolation, and voltage swell, voltage sag and voltage distortion conditions.

Adaptive filter based current controller for Shunt Active filter

This paper deals with the harmonic mitigation and reactive power compensation using Shunt Active filter. The performance of the Shunt active filter depends on the design and current control technique for generating a reference current. The design of the filter involves the iterative procedure for choosing the filter components so that it compensates the harmonics and reactive power for maximum load condition. The current controller method adopted for indirect current control technique where the reference signal is similar to the supply current signal. The Adaptive filter used in current controller mitigates harmonics and reactive power and voltage control loop of SAF balancing the active power between the load and supply unit. The learning rate is fixed by repeated simulation. The SAF active filter is tested in four load condition ie., nonlinear load(37% Total Harmonic Distortion(THD)),highly nonlinear load(>100% THD), linear load(<8% THD, power factor(pf) <0.5) and both nonlinear and linear load(37% THD and 0.7 pf). The study is carried out in MATLAB Simulink and the results are presented.

Performance Enhancement of Wind Energy System with Distribution Static Compensator

Objectives: In this paper, dynamic performance of Wind Energy System (WES) comprising of Squirrel Cage Induction Generator (SCIG) is analyzed for grid connected operation with DSTATCOM. Methods/Statistical analysis: In the present work, modeling, analysis and working of a low voltage distribution system supported with wind energy conversion system is analyzed. A Distribution STAtic COMpensator (DSTATCOM) has been modeled and simulated using MATLAB. The effectiveness of the proposed system has been verified by simulation and analytical results. The indirect current control technique is employed for present analysis as it is simple, robust and favourable as compared to other methods. Findings: The DSTATCOM improves the performance of Wind Energy System (WES) under transient condition i.e. change in wind speed and sudden change in load. The DSTATCOM augmented with wind energy system addresses the power quality and grid stability issues. Application/Improvements: The DSTATCOM in present study provides transient voltage support and also maintains the stability of a WES.When wind penetration increases beyond 30%, the system loses stability. A detailed simulations study is carried out on the application of DSTATCOM to improve the stability of the system

A comparative analysis of shunt active power filter and hybrid active power filter with different control techniques applied for harmonic elimination in a single phase system

This paper presents a comparative analysis between a single phase shunt active power filter (SPSAPF) and a single phase shunt hybrid filter (SPSHPF) to improve the power quality using different control techniques such as hysteresis current control and hysteresis fuzzy combined current control technique along with a different fuzzy rule (7/7 and 5/5) to a distribution system. An indirect current control technique along with hysteresis current control strategy is implemented on both the filters to generate the switching signal used for turning on and off of the insulated gate bipolar transistor. The indirect current control technique that is implemented for both filters is based on extracting the source current reference from the distorted waveform of the load current. The Simulink models are prepared. Simulation results are obtained and compared for both the filters with the same control technique, and it is observed that in every case SPSHPF shows excellent results in comparison to SPSAPF.

STATCOM analysis of twin converter using PWM technique

This paper addresses a two different configuration of shunt connected static synchronous compensator (STATCOM) namely a six pulse voltage source converter-based static synchronous compensator (STATCOM) and a 12 pulse voltage source converter-based static synchronous compensator with two different dc link voltages to demonstrate its effectiveness in maintaining stability of the voltage in a 600 km transmission line. The main objective of this paper is to maintain simple and fast voltage regulation at any point in the transmission line with reduce total harmonic distortion (THD) by connecting the twin converter-based static synchronous compensator to the grid through accomplishing indirect current control (ICC) technique which in turn utilities four PI control loops. The indirect current controller is developed to produce the modulation signals in order to generate the gate signals for the two voltage source converters (VSCs) by using the phase shifted carrier-based pulse width modulation (PWM) topology. Here simulation studies is performed with the above mentioned static synchronous compensator configurations and finally concludes that twin converter-based static synchronous compensator operates satisfactorily under power quality problems such as voltage interruption, sag, etc. compared to conventional static synchronous compensator.

Comparison of Three leg and Four Leg VSC DSTATCOM for Power Quality Assessment

A new three-phase four-wire DSTATCOM (distribution static compensator) based on three-leg VSC (voltage source converter) and a star/delta transformer is proposed for power quality improvement. The star/delta transformer connection mitigates the neutral current and the 3-leg VSC compensates harmonic current, reactive power and balances the load. Three single phase transformers are connected as star/delta transformer for interfacing to a three phase four-wire power distribution system and the required rating of the VSC is reduced. However, a 4-leg VSC (voltage source converter) based DSTATCOM (Distribution Static Compensator) is used for the load compensation and neutral current compensation in 3-phase 4-wire distribution system. For extracting the reference source currents, Instantaneous Symmetrical Component Theory (ISCT) based control algorithm is modified for voltage regulation and used with indirect current control technique for controlling the DSTATCOM currents. The DSTATCOM is controlled for power factor correction and voltage regulation at PCC (point of common coupling). Simulations are performed for various load conditions such as a reactive linear load, an unbalanced load and a non-linear load in Power Factor Correction (PFC) mode and in Zero Voltage Regulation (ZVR) mode in MATLAB environment using SIMULINK and Sim Power System (SPS) toolbox.

Improvement of Power Factor and Harmonic Elimination in Distribution Line using PI with Hysteresis Current Controller

Power quality improvement is a major research area in current context. Though much work has been done by many researchers still scope is there to work on this area. In this paper an attempt is made to eliminate the harmonics as well as for the improvement of power factor. Here distribution static synchronous compensator (DSTATCOM) is used to improve power factor in distribution line & mitigate harmonics with an optional feature of voltage regulation. Further the frequency analysis of the distribution line is analyzed both before & after compensation. A relay based hysteresis current regulator is used for DSTATCOM controller in indirect current control technique. Simulation is carried out in standard MATLAB environment. Results of simulations are presented for linear & nonlinear load.

Improved Active Power Filter Performance Based on an Indirect Current Control Technique

This paper presents a method for the performance improvement of a shunt active power filter (SAPF) using the indirect current control (ICC) scheme. Compared to the conventional direct current control (DCC) scheme, the ICC gives better performance with a lower number of sensors. A simplified and efficient control algorithm using a low cost Intel 80C196KC microcontroller is implemented using only two current sensors for the source current and one voltage sensor for the DC-link voltage of the SAPF circuit. The objective is to eliminate harmonics and to compensate the reactive power produced by non-linear loads such as an uncontrolled rectifier feeding an inductive load. The APF is realized using a three phase voltage source inverter (VSI) with a dc bus capacitor. Experimental results are presented to prove the better performance of the ICC method over the DCC one.

New control approach for capacitor supported DSTATCOM in three-phase four wire distribution system under non-ideal supply voltage conditions based on synchronous reference frame theory

A large number of single-phase linear and non-linear loads may be supplied from three phase ac mains with neutral conductor. They cause excessive neutral current, harmonics and reactive power burden and unbalance. A four wire DSTATCOM (distribution static compensator) is used for neutral current compensation along with reactive power compensation, harmonics elimination and load balancing. A novel control approach is proposed for the control of four wire DSTATCOM under non-ideal supply voltage conditions. A four-leg voltage–source converter (VSC) with a dc capacitor is used as a four wire DSTATCOM. The proposed control approach is based on synchronous reference frame (SRF) theory and an indirect current control technique. The switching signals for the voltage–source converter (VSC) of the DSTATCOM are derived from the estimated reference supply currents. The load balancing, harmonics elimination and the neutral current compensation are demonstrated along with unity power factor (UPF) and zero voltage regulation (ZVR) modes of operation. Simulation results based on MATLAB software with its Simulink and power system blockset (PSB) toolboxes are presented to validate the control strategy. The DSTATCOM is able to maintain the self-supported dc bus under various disturbances.

Generalised single-phase p-q theory for active power filtering: simulation and DSP-based experimental investigation

The single-phase p-q theory for the purpose of active power filtering in the case of single-phase loads is dealt with here. A simple modification is proposed to develop a generalised single-phase p-q theory that can be utilised under the condition of distorted utility voltage. A systematic study is presented by realising both direct and indirect current control techniques. The simulation as well as the digital signal processor (DSP) (DS1104 of dSPACE) based experimental results are discussed. The developed single-phase shunt active power filter (APF) prototype is tested under different operating conditions with different loads to evaluate the full capabilities of the proposed generalised theory for practical uses. The shunt APF reduces the source current total harmonics distortion (THD) from 27.2 to 3.4% under a distorted supply voltage with a THD of 16.2%.

A comparative study of shunt hybrid and shunt active power filters for single-phase applications: Simulation and experimental validation

The aim of this paper is to compare the performance of the single-phase shunt active power filter (SPSAPF) and the single-phase shunt hybrid power filter (SPSHPF) that adopt both an indirect current control scheme with a unipolar pulse width modulation (U-PWM) strategy. The SPSHPF topology includes, in addition to the components of the SPSAPF, a power factor correction capacitor connected in series with a transformer. The primary winding of the transformer is connected to the single-phase voltage–source inverter, which is the main part of the filter. The indirect current control technique that is implemented for both filters is based on extracting the source current reference from the distorted waveform of the load current. The U-PWM control technique is based on comparing simultaneously a triangular high frequency carrier signal with a slow-varying regulation signal and its opposite. The double comparison process results in the gate signals for the semiconductors. A laboratory prototype for each filter is built. It is demonstrated that the rating of the inverter used in the SPSHPF is three to four times lower than the one corresponding to the SPSAPF. In addition, the performance of the SPSHPF is found to be much better than that of the SPSAPF as far as the line current distortion is concerned.

Modified PWM with a new indirect current control technique applied to a single-phase shunt active power filter

Modified PWM with a new indirect current control technique applied to a single-phase shunt active power filter

Indirect current control of active filter for harmonic elimination with novel observer-based noise reduction scheme

Active power filters have been developed recently to solve the harmonics disturbance problems on power system networks. The direct current control scheme is generally used to control the harmonic compensating current directly for current source active power filters. To improve the characteristics of harmonic elimination, the voltage regulation scheme is proposed which regulates the filter capacitor voltage at the input side. Hence the voltage regulation scheme is an indirect current control technique for making sinusoidal line current. To implement this proposed scheme, the electronic differentiator should be used. By using the conventional differentiator, high frequency noise is generated in the controller. This deteriorates both the accuracy and reliability of the controller. To reduce this noise, a novel observer-based noise reduction scheme is proposed for our active filter system. The observer-based algorithm and characteristics of indirect current-controlled active filters are investigated through simulations and experiments.

Simulation and digital implementation of a simple technique of active filter for elimination of switching ripples/distortion in the supply current

AbstractThis paper deals with a digital signal processor (DSP) based implementation of a three‐phase shunt active filter (AF) to compensate harmonics and reactive power of nonlinear loads. A three‐phase diode bridge rectifier with R‐L and R‐C loads is taken as the nonlinear load. It is observed that the AF systems suffer from the problems of switching ripples (in case of R‐L nonlinear load) and distortion (in case of R‐C nonlinear load). The switching ripples and distortion in the supply currents contribute considerably to its Total Harmonics Distortion (THD). This investigation proposes a new, cost free and simple approach for the elimination of switching ripples and distortion in the supply current. A pulse width modulation (PWM) current controlled voltage source inverter (CCVSI) is used as the AF. The AF system is tested with two types of PWM switching techniques, namely, carrier‐less (hysteresis) and carrier based techniques. Two types of current control techniques, namely, direct current control and indirect current control are designed to obtain PWM switching signals for the devices of the AF. The capability of the indirect current control technique towards the elimination of switching ripples and distortion is established. Simulated and experimental results for steady state and transient operating conditions of the AF for R‐L as well as R‐C nonlinear loads are given and discussed in detail.

DSP-based indirect-current-controlled STATCOM. Part 2: Multifunctional capabilities

For pt.I see ibid., vol. 147, no.2, p.107-12 (2000). The multifunctional capabilities of a DSP-based three-phase static compensator (STATCOM) are covered. An IGBT-based voltage source inverter (VSI) with indirect-current control technique is taken as a STATCOM. Four different types of loads consisting of linear/nonlinear and single/three-phase elements are used. Fuzzy-logic-based closed-loop control of the system reduces the size of capacitor in the DC busbar of the VSI and it also imparts a good level of performance. The steady state and transient results of a laboratory prototype are given and discussed.