Voltage Support Provided by STATCOM in Unbalanced  Power Systems

Rodrı́guez, Ana; Bueno, Emilio; Mayor, Álvar; Rodríguez, Francisco; García-Cerrada, Aurelio

doi:10.3390/en7021003

Cited by 19 publications

(18 citation statements)

References 15 publications

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“…In distorted grids, there are higher even harmonic power ripples due to other harmonic sequence voltages (−5, +7, −11, +13). Hence, an effective multifrequency current reference calculator is required by the algorithm to accomplish the power ripple removal.The presented control objective has an unavoidable characteristic in three-phase three-wire systems-the elimination of active power oscillations implies more reactive power fluctuations [13,16]. Previous publications such as References [17][18][19] claimed the elimination of both active and reactive power oscillations, simultaneously.…”

mentioning

confidence: 91%

“…The current reference could be calculated by means of the active and reactive power theory, first introduced in Reference [11]. From that theory, many works have dealt with the regulation of active power oscillations when grid imbalances [12,13] or grid faults [14][15][16] are faced by the power converter. However, these methodologies only remove the second harmonic power ripple due to the appearance of fundamental negative sequence (FNS) voltage and its interaction with the fundamental positive sequence (FPS) current.…”

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confidence: 99%

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Enhanced Current Reference Calculation to Avoid Harmonic Active Power Oscillations

Serrano

Moriano²,

Rizo

et al. 2019

Energies

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Energy storage systems play a key role in the rise of distributed power generation systems, hence there is great interest in extending their lifetimes, which are directly related to DC current ripple. One of the ripple sources is the low-frequency active power fluctuations under unbalanced and distorted grid voltage conditions. Therefore, this paper addresses a multifrequency control strategy where the harmonic reference currents are calculated to reduce harmonic active power oscillations. The stationary reference frame (StRF) approach taken here improves the precision and computational time of the current reference calculation method. Additionally, in order to ensure safe converter operation when a multifrequency reference current is provided, a computational efficient peak current saturator is applied while avoiding signal distortion every time step. If the injected current harmonic distortion is to be minimized, which is a feature included in this work, the peak current saturator is a necessary requirement. Active power ripple is reduced even with frequency variations in the grid voltage using a well-known frequency-adaptive scheme. The simulation and experimental results prove the optimized performance for the control objective: power ripple reduction with minimum current harmonic distortion.Energies 2019, 12, 4075 2 of 21 torque pulsations [9]. Besides, on doubly fed induction generators (DFIGs) for wind turbines, active power oscillations are related to electromagnetic torque ripples that increase the mechanical stress on the turbine system [10].The harmonic power oscillations in three-phase three-wire AC electrical systems come from the presence of distorted or unbalanced grids. Therefore, the control strategy aims to regulate the instantaneous active power at a constant value by injecting the suitable currents into the grid. The current reference could be calculated by means of the active and reactive power theory, first introduced in Reference [11]. From that theory, many works have dealt with the regulation of active power oscillations when grid imbalances [12,13] or grid faults [14][15][16] are faced by the power converter. However, these methodologies only remove the second harmonic power ripple due to the appearance of fundamental negative sequence (FNS) voltage and its interaction with the fundamental positive sequence (FPS) current. In distorted grids, there are higher even harmonic power ripples due to other harmonic sequence voltages (−5, +7, −11, +13). Hence, an effective multifrequency current reference calculator is required by the algorithm to accomplish the power ripple removal.The presented control objective has an unavoidable characteristic in three-phase three-wire systems-the elimination of active power oscillations implies more reactive power fluctuations [13,16]. Previous publications such as References [17][18][19] claimed the elimination of both active and reactive power oscillations, simultaneously. However, this approach in three-wire systems leads to the injection of zero-sequence...

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confidence: 91%

mentioning

confidence: 99%

Enhanced Current Reference Calculation to Avoid Harmonic Active Power Oscillations

Serrano

Moriano²,

Rizo

et al. 2019

Energies

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“…Although one of the most classical control strategies for a DSTATCOM is the use of PI controllers in a rotating reference frame [7], various works deal with the problem of voltage regulation together with voltage imbalances: in [8], a control system based on resonant regulators is used to compensate voltage imbalances at the PCC. The control system is implemented in a stationary reference frame in order to reduce the number of resonant regulators needed for the compensation.…”

Section: Introductionmentioning

confidence: 99%

Harmonic and imbalance voltage mitigation in smart grids: A DSTATCOM based solution

Roncero‐Sánchez

Acha

2015

IEEE EUROCON 2015 - International Conference on Computer as a Tool (EUROCON)

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This paper presents a control system for a DSTAT-COM with which to compensate the voltage sags, unbalanced voltages and voltage harmonics caused by unbalanced loads and nonlinear loads, which can be use to enhance the power quality in smart grids. The compensation of the voltage sags is carried out by injecting reactive power, while the voltage harmonics and voltage imbalances are ameliorated by canceling out the harmonics and the imbalances of the grid current. The control scheme is designed in the synchronous reference frame with a nested control structure which contains PI controllers and resonant regulators. These regulators are tuned at the harmonic frequencies to be eliminated and can be implemented to incorporate an update of those frequencies. Simulation results show the resultant time response of the voltage at the point of common coupling and the grid current.

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“…With this approach, unbalanced-voltage control and current harmonic control in a STATCOM are treated within the same framework. This is an alternative viewpoint to the one presented in [49] where positive-sequence and negative-sequence controllers are investigated separately. …”

Section: Voltage Unbalance Compensation Using Emrf Controllermentioning

confidence: 99%

“…This can be important for sensitive loads that could disconnect if the AC voltage does not meet restrictive voltage standards. This task can also be accomplished by means of a STATCOM, above all in weak grids whose significant grid impedance may lead to large PCC voltage variations [49].…”

Section: Problem Descriptionmentioning

confidence: 99%

Versatile Control of STATCOMs Using Multiple Reference Frames

Ochoa-Gimenez

García-Cerrada

Roldán-Pérez

et al. 2014

Static Compensators (STATCOMs) in Power Systems

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This chapter first reviews the fundamentals of active and reactive power control using STATCOMs. Then, two current control algorithms, namely selective/ resonant controllers and repetitive controllers, are presented that provide a STATCOM with the capability of controlling the harmonics of the current injected into the PCC. Finally, the use of synchronously-rotating reference frames is generalized so that current harmonic control can also be achieved using PI controllers. An efficient application of the last technique is explained in detailed and a number of experimental results are presented. It will be demonstrated that versatile control of STATCOMs is straightforward using this technique even if the grid frequency varies. This technique can be applicable to both, traditional, strong and centralised electric power systems and those to come in the future with large amounts of distributed generation.Keywords STATCOM Á VSC Á Harmonic control Á Selective control Á Repetitive control Á Multiple reference frames M. Ochoa-Giménez Á A. García-Cerrada (&) Á J. Roldán-Pérez Á J.L. Zamora-Macho Á P. García IntroductionSTATCOMs are typical shunt power electronics-based devices (see Fig. 7.1), used in power systems for multiple purposes [1]. Originally, STATCOMs were intended for reactive power control as a superior alternative to thyristor-controlled devices such as Thyristor-Controlled Reactors (TCRs) or Thyristor-Switched Capacitors (TSCs) [2]. Reactive power compensation in TCRs and TSC depends on the point of common coupling (PCC) voltage unlike in STATCOMs which could overcome this limitation thanks to the use of electronic switches capable of controlled ON-OFF and OFF-ON commutation. Also thanks to their controlled commutation, STATCOMs provide a much faster dynamic performance [3]. STATCOMs rapidly evolved from square wave multi-pulse converters [4-6] to pulse width modulation (PWM)-controlled converters [7][8][9] making it possible a fast and accurate active and reactive power control at the PCC.Nowadays STATCOMs are used for reactive power compensation mainly, in applications such as improving fault-ride-through of wind generators [10] or compensating voltage drops at the transmission level or voltage fluctuations at the distribution level [11,12]. When STATCOMs are used in distributions systems they are often called Distribution Static Compensators (DSTATCOMs) [13].The most classical approach to the control of a STATCOM [9] (reactive power control) only addresses the control of the fundamental components of the current injected in the PCC: the positive-sequence current of the grid frequency. Meanwhile, the same shunt-connected components in Fig. 7.1 (left) namely, a voltage source converter (VSC), a transformer (optional) and a connection filter, are.1 STATCOM schematics (left) and simplified model (right), nomenclature: p and q are the instantaneous real and reactive power injected by the STATCOM into the PCC, p R is the power lost in the filter resistance, p L is the power consumed in the filter plus ...

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Voltage Support Provided by STATCOM in Unbalanced Power Systems

Cited by 19 publications

References 15 publications

Enhanced Current Reference Calculation to Avoid Harmonic Active Power Oscillations

Enhanced Current Reference Calculation to Avoid Harmonic Active Power Oscillations

Harmonic and imbalance voltage mitigation in smart grids: A DSTATCOM based solution

Versatile Control of STATCOMs Using Multiple Reference Frames

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