Operation Of Distribution Static Compensator Research Articles

CTF-based control technique for power quality enhancement in the SPV system tied to the grid

The solar photovoltaic (SPV) system tied to grid through distribution static compensator (DSTATCOM) is controlled by Character of triangular function (CTF)-based control technique. The reference currents are computed for synchronisation of SPV to the grid. The essential active and reactive components of load current are computed with above mentioned technique and firing pulses for the voltage source converter (VSC) are generated by comparing these currents with grid currents. It requires adders, multipliers and low pass filter blocks so it is a simple and fast technique. The proposed technique is used for harmonic suppression, load balancing and supply reactive power for local load demand. This technique has been tested for steady-state and dynamic conditions for the SPV system with varying nonlinear load in the power factor correction (PFC) mode of DSTATCOM operation. The proposed technique can reduce the grid current harmonics within IEEE standards which are observed in the simulation results.

Advanced adaptive algorithm controlled single‐phase DSTATCOM operation during weak grid conditions

SummaryThis paper presents the performance of a single‐phase utility‐tied distribution static compensator (DSTATCOM) with nonlinear load operating under weak grid conditions. The DSTATCOM is controlled by a complex kernel risk‐sensitive p‐power (CKRSP) algorithm. Ever‐increasing nonlinearity of the load, rapidly increasing renewable energy system installed capacity, and rising heating loads, especially during the winter season, lead to various power quality issues that worsen during weak grid conditions. An advanced adaptive control scheme, that is, CKRSP, enforces the system to perform various multifaceted operations, including harmonics suppression, handling rapid load variations, voltage sag and swell, and active and reactive power control at the point of common coupling (PCC) during weak grid conditions. The proposed CKRSP algorithm outperforms conventional control algorithms regarding steady‐state error, convergence speed, and accuracy. During weak grid conditions, the proposed system ensures stable DC bus voltage with a reduced second harmonic component. This further assists the CKRSP control in better extracting the fundamental load current component using a smoother loss component of current . The proposed system can handle various power quality issues during weak grid conditions while ensuring the overall system's stability. The laboratory prototype results show that the presented system performs satisfactorily under weak grid conditions per IEEE 519‐2014 standards.

A multi-objective control scheme of a voltage source converter with battery–supercapacitor energy storage system used for power quality improvement

Conventionally, an energy storage system and two Voltage Source Converters (VSCs) are required to combine the operation of Distribution Static Compensator (DSTATCOM) and Uninterruptible Power Supply (UPS). The DSTATCOM’s VSC can compensate for the source voltage sag and swell. However, it cannot compensate for the voltage interruption. On the other hand, the VSC of the UPS can compensate for the source voltage interruption, but it cannot compensate for the voltage sag and swell. This paper proposes a control algorithm that uses a single VSC and a battery–supercapacitor energy storage system to function as DSTATCOM and UPS. The VSC and the battery–supercapacitor energy storage system mitigates the sag, swell, and interruption of the source voltages. Under the normal source voltages, this system mitigates the load current harmonics, unbalance, and reactive power. The proposed control algorithm uses a State of Charge (SoC) based scheme to control the battery–supercapacitor energy storage system. This control scheme protects the battery and supercapacitors from overcharging. Also, it eliminates the ripples in the load angle and increases the battery cycle life. The efficacy of the proposed control scheme has been verified through the experimental setup of the VSC with the battery–supercapacitor energy storage system in the laboratory.

PQ Theory Based Power Quality Improvement in Distribution Level with D-STATCOM

The Transient response of the distribution static compensator (DSTATCOM) is very important while compensating rapidly varying unbalanced and nonlinear loads. Any change in the load affects the dc link voltage directly. The sudden removal of load would result in an increase in the dc link voltage above the reference value where as a sudden increase in the load would reduce the dc link voltage below its reference value. The proper operation of DSTATCOM requires variation of the DC link voltage within the prescribed limits. Conventionally, a proportional-integral (PI) controller is used to maintain the dc-link voltage to the reference value. It uses the deviation of the capacitor voltage from its reference value as its input. However, the transient response of the conventional PI dc-link voltage controller is slow. In this paper, a fast acting dc-link voltage controller based on the energy of the dc-link capacitor is proposed and proposed shunt controller method by using PQ-Theory. Mathematical equations are given to compute the gains of the conventional controller based on the fast-acting dc-link controllers to achieve similar fast transient response. The detailed simulation studies are carried out to validate the proposed controller..

Probabilistic Assessment of DSTATCOM Operation in Distribution Systems Using Data Clustering Method

The importance of probabilistic assessment in distribution systems is very high due to the increasing penetration of renewable energy sources (RESs) with their fluctuating behavior. Also, there are some other uncertain variables in distribution systems such as loads fluctuations. More awareness of the system state by considering many uncertainties provides more certainty in decision making and causes better risk management. Moreover, the distribution static compensator (DSTATCOM) has been recently implemented due to its efficient abilities in the distribution systems operation especially when RESs are integrated into them. This article investigates the probabilistic assessment of DSTATCOM operation in a distribution system using the k-means-based data clustering method (DCM). The uncertainty of load demands, wind speed, and solar radiation are considered in this study. The performance of DCM is compared to the Monte Carlo simulation (MCS) and Latin Hypercube sampling (LHS) methods in terms of accuracy and computational burden. The efficiency of k-means-based DCM is investigated in the IEEE 69-node test system.

A new voltage control strategy to improve performance of DSTATCOM in electric grid

A new voltage control strategy of distribution static compensator (DSTATCOM) has been proposed in this paper for electric grid applications. The proposed control scheme combines two methods of DSTATCOM operation to improve its performance. Considering power factor and voltage magnitude as degree of freedom, the DSTATCOM provides features such as mitigation of voltage and current harmonics, balancing of source currents, improvement of power factor, voltage regulation during voltage sag and swell, reduction in inverter losses, and control of load power to achieve energy conservation. The performance of proposed DSTATCOM control is better as compared to its conventional operation at any time of operation. PSCAD simulation and experimental results validate the performances.

Control of Grid Fed PV Generation Using Infinite Impulse Response Peak Filter in Distribution Network

An upsurge in the integration of renewable sources to the utility grid has resulted into escalating concerns regarding power quality (PQ) improvement. In order to provide efficient operation under weak grid conditions, the necessity of a competent control technique is dominant. Consequently, the implementation of an infinite impulse response (IIR) peak filter is used here for harmonics mitigation, power factor correction, and alleviating other PQ issues by providing distribution static compensator (DSTATCOM) capabilities. In addition, this control technique also works during conditions when solar photovoltaic (PV) power is not procurable. During day, the requirement of load is fed from the solar PV array and the stored grid power. On the other hand, at night when the power from solar PV array is unavailable, the requirements of load are fulfilled from the grid and DSTATCOM operation ensures power quality improvement. In order to validate this system, it is maintained according to the IEEE-519 standard. The considered weak grid conditions include load unbalancing, intermittent solar insolation, voltage sag, voltage swell, voltage distortion, and voltage unbalance conditions. The benefits of IIR peak filter include adaptive computation during filtering, thereby alleviating the computational complexity. Moreover, less memory space is required during execution guaranteeing fast performance during weak grid conditions. Simulated results are utilized to depict the behavior of the system during abnormal grid conditions. Moreover, its comparative performance with the existing control techniques, is also presented. For further substantiation and in order to observe reliable operation, a laboratory prototype is developed and tested during weak grid conditions such as voltage distortion, voltage unbalance, voltage sag, voltage swell, and load unbalancing.

Performance evaluation of digital filters in distribution static compensator for non‐linear loads

This study deals with the performance analysis of three digital filters viz. multiple complex coefficient filter (MCCF), moving average (MA) and Butterworth in distribution static compensator (DSTATCOM) for non-linear loads. The filters are designed to extract the fundamental component of load current and tested in the closed-loop control of DSTATCOM. The filters are used to extract fundamental signal from the non-linear distorted source/load currents and all the lower-order harmonics present in the non-linear current drawn by the load. The performance of MCCF filter is compared to conventional filters such as Butterworth and MA filter. The detailed frequency response of MCCF is analysed. The magnitude and phase response plot of the MCCF suggest that this filter has unity gain and zero phase shift at fundamental frequency. All the three filters are implemented on a DSTATCOM for three-phase, three-wire distribution system. The DSTATCOM is implemented using a three-phase voltage source converter controlled using dSPACE 1104 controller. The closed-loop operation of DSTATCOM designed using MCCF is tested under steady state and dynamic system conditions. Simulation and experimental results are demonstrated with relevant waveforms under different load conditions.

Design and operation of DSTATCOM for power quality improvement in distribution systems

This study provides a control scheme for distribution static compensator (DSTATCOM) which compensates three-phase, four-wire distribution system and operates the DSTATCOM in voltage control mode (VCM). This algorithm provides achievement of advantages of current control mode operation while DSTATCOM operated in VCM. Compensator injects reactive and harmonic component of load current and it provides fast voltage regulation at the load terminal with maintaining nearly unity power factor (UPF). Deadbeat voltage control law is used for generating switching pulses for insulated gate bipolar transistor (IGBT) switches and reference terminal voltage is generated by system in such a way that point of common coupling maintains nearly UPF. The proposed design is implemented to mitigate power quality issues induced by source as well as load and it is found to be efficient and robust which is validated through performance under nominal operation, unbalance and distorted source voltage, sag-swell and unbalancing in load for any types of load. Capability of this arrangement has been verified using result obtained from MATLAB–SIMULINK-based environment. Different types of loads have been considered (balanced and unbalanced, linear and non-linear) to check the performance of this arrangement.

Design of External Inductor for Improving Performance of Voltage Controlled DSTATCOM

A distribution static compensator (DSTATCOM) is used for load voltage regulation, and its performance mainly depends upon the feeder impedance and its nature (resistive, inductive, stiff, nonstiff). However, a study for analyzing voltage regulation performance of DSTATCOM depending upon network parameters is not well defined. This paper aims to provide a comprehensive study of design, operation, and flexible control of a DSTATCOM operating in voltage control mode. A detailed analysis of the voltage regulation capability of DSTATCOM under various feeder impedances is presented. Then, a benchmark design procedure to compute the value of external inductor is presented. A dynamic reference load voltage generation scheme is also developed, which allows DSTATCOM to compensate load reactive power during normal operation, in addition to providing voltage support during disturbances. Simulation and experimental results validate the effectiveness of the proposed scheme.

Operation and Control of an Improved Performance Interactive DSTATCOM

This paper proposes an improved performance interactive distribution static compensator (DSTATCOM) to address the limitations of conventional current control mode (CCM) and voltage control mode (VCM) operations. The proposed interactive scheme provides smooth transfer of modes of operation while remaining connected in the distribution system. In normal operation, the DSTATCOM operates in CCM to make source currents balanced, sinusoidal, and at a unity power factor. During voltage disturbances, the CCM operation cannot improve load voltage. In that case, DSTATCOM operation is changed to VCM, which maintains a constant voltage across the sensitive loads. Hence, this interactive DSTATCOM ensures continuous, flexible, and robust operation of the load. Moreover, the filter current requirements are reduced in the proposed scheme, which reduces the losses in the filter and feeder, improves inverter efficiency, and requires a reduced-rating inverter for sag mitigation. The principle of operation and control for both operating modes is analyzed. The detailed process of the flexible transfer between the two modes is derived. Deadbeat predictive control algorithms for CCM as well as VCM operation are developed for fast operation during mode transfers. The performance of the proposed scheme is validated by both simulation and experimental results.

Variable Forgetting Factor Recursive Least Square Control Algorithm for DSTATCOM

This paper proposes an implementation of distribution static compensator (DSTATCOM) for the three-phase distribution system. The functions of DSTATCOM are harmonics elimination, compensation of reactive power, and load balancing in power factor correction and voltage regulation modes. A variable forgetting factor recursive least square (VFFRLS)-based control algorithm is proposed for effective operation of DSTATCOM to estimate weighted values of active and reactive power components of load current. The proposed control algorithm is fast in convergence and has quick response. A prototype of DSTATCOM is developed in the laboratory using a digital signal processor (dSPACE 1104) and voltage-source converter and tested for various operating conditions under nonlinear load. The performance of DSTATCOM is found satisfactory in mitigating various power-quality problems with the VFFRLS-based control algorithm.

An Adaptive Hysteresis Band Current Controller Based DSTATCOM for Enhancement of Power Quality with Various Load

The Distribution Static Compensator (DSTATCOM) is used for development of power quality in power distribution network with various loads such as linear, nonlinear and variable load. The dc link capacitor voltage is directly affected by any alteration made in the load. Proper operation of DSTATCOM requires maintenance of capacitor voltage within the limits. Right from the beginning, conventional controller has been used to maintain the converter dc-link capacitor voltage. In spite of it, the transient response of the PI and Hysteresis controller is still slow. In this paper, an adaptive hysteresis band current controller is proposed for DSTATCOM to eliminate harmonics and compensate the reactive power of three-phase converter. The adaptive hysteresis band current controller is varied from the hysteresis bandwidth with respect to modulation frequency, source voltage, dc link voltage and slope of the reference compensator current wave. Mathematical expressions are given to design the adaptive hysteresis band current controller to achieve the fast transient response. The results of simulation study of the proposed method have been carried out using MATLAB simulation software.

LCL Filter with Active Damping using PI and SSI Regulators in Synchronous Rotating Reference Frame Current Controller for DSTATCOM

Abstract This article proposes a distribution static compensator (DSTATCOM) with interface LCL (inductor-capacitor-inductor) filter for load compensation in three-phase four-wire distribution system. DSTATCOM, consisting of voltage source inverter (VSI), is connected in parallel to the load and injects currents corresponding to load reactive, harmonic powers. But this injected current consists of unnecessary high-frequency switching ripple generated by VSI. This LCL filter has superior switching ripple attenuation capability compared to L filter. Moreover, this can be achieved with small value of overall LCL filter inductance than L filter. Thus providing high slew rate for output current to track the desired reference current closely, reducing voltage drop across it, as well as cost and size of filter. However, one major concern with LCL filter is its resonating frequency (determined from its L, C, L values), which can create high-resonance oscillating currents and results in improper load compensation. Therefore, in this study, proper design of LCL filter with high switching ripple attenuation and a current controller with proportional integral (PI) plus harmonic compensation (HC) regulators along with active damping feature of LCL filter in synchronous rotating reference (dq0) frame are presented. HC regulator minimizes the steady-state error in the non-sinusoidal filter currents (fundamental and harmonic) which are tracked by the VSI. Active damping feature (obtained by capacitor current feedback control of LCL filter) is used to overcome resonance oscillations and provides proper control, operation of DSTATCOM under steady-state and dynamic load conditions. Stability studies for designed LCL filter and current controller using Bode and root locus plots are also performed and presented. Extensive simulation study, to understand the compensation performance of LCL filter DSTATCOM with two types of current controllers (PI and PI plus HC) under steady-state and dynamic load conditions, is carried out in PSCAD simulator and the corresponding results along with THDs of various parameters are presented.

A Fast-Acting DC-Link Voltage Controller for Three-Phase DSTATCOM to Compensate AC and DC Loads

The transient response of the distribution static compensator (DSTATCOM) is very important while compensating rapidly varying unbalanced and nonlinear loads. Any change in the load affects the dc-link voltage directly. The sudden removal of load would result in an increase in the dc-link voltage above the reference value, whereas a sudden increase in load would reduce the dc-link voltage below its reference value. The proper operation of DSTATCOM requires variation of the dc-link voltage within the prescribed limits. Conventionally, a proportional-integral (PI) controller is used to maintain the dc-link voltage to the reference value. It uses deviation of the capacitor voltage from its reference value as its input. However, the transient response of the conventional PI dc-link voltage controller is slow. In this paper, a fast-acting dc-link voltage controller based on the energy of a dc-link capacitor is proposed. Mathematical equations are given to compute the gains of the conventional controller based on fast-acting dc-link voltage controllers to achieve similar fast transient response. The detailed simulation and experimental studies are carried out to validate the proposed controller.

Stability Analysis Based on Bifurcation Theory of the DSTATCOM Operating in Current Control Mode

This paper presents the stability analysis for a distribution static compensator (DSTATCOM) that operates in current control mode based on bifurcation theory. Bifurcations delimit the operating zones of nonlinear circuits and, hence, the capability to compute these bifurcations is of important interest for practical design. A control design for the DSTATCOM is proposed. Along with this control, a suitable mathematical representation of the DSTATCOM is proposed to carry out the bifurcation analysis efficiently. The stability regions in the Thevenin equivalent plane are computed for different power factors at the point of common coupling. In addition, the stability regions in the control gain space, as well as the contour lines for different Floquet multipliers are computed. It is demonstrated through bifurcation analysis that the loss of stability in the DSTATCOM is due to the emergence of a Neimark bifurcation. The observations are verified through simulation studies.

A flexible DSTATCOM operating in voltage or current control mode

The topology and control are discussed of a distribution static compensator (DSTATCOM) that can be operated flexibly in the voltage or current control mode. In the voltage control mode, the DSTATCOM can force the voltage of a distribution bus to be balanced sinusoids. In the current control mode, it can cancel distortion caused by the load, such that current drawn by the compensated load is pure balanced sinusoid. Both these objectives are achieved, irrespective of unbalance and harmonic distortions in load currents or source voltages. The chosen DSTATCOM topology includes three single-phase voltage source inverters connected in parallel to a filter-capacitor, which allows the high-frequency component of the current to pass. A switching control scheme is proposed, and its suitability is proved for this problem. The proposed scheme is verified using computer simulation studies.