Effects of limits in small signal stability analysis of power systems

Lerm, A.A.P.; Cañizares, Claudio A.; Mithulananthan, N.

doi:10.1109/pess.2001.970351

Cited by 13 publications

(4 citation statements)

References 12 publications

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“…Let x and y be respectively the input and output of the limiter. In the region y min ≤ x ≤ y max , y = x (15) . Otherwise, y assumes either y min or y max .…”

Section: Control Equationsmentioning

confidence: 99%

Design of an Autonomous Control for Parallel-Connected Uninterruptible Power Supplies

Sato

Kawamura

2006

IEEJ Trans. IA

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Some inherent characteristics of an electrical power system can be conveyed to control multiple uninterruptible power supplies (UPS) connected in parallel in an autonomous manner, i.e. without communication signal exchange. It results in an independent control with two control equations, where the controllable variables are the phase angle and the magnitude of the output voltage.The dynamic equation of a synchronous machine relates frequency of operation and active output power, so that it evolves to the control equation of output voltage phase angle hs:Note that, to deliver the value of the phase angle hs, Eq. 1 only requires information about the active currentÎ p .With respect to another control equation, from the existing relation between voltage magnitude and flow of reactive power, computer simulations using an elementary circuit for two voltage sources connected in parallel show a relation between lateral current (or circulating current) and voltage difference. With employment of (1), circulating current becomes only reactive. It suggests a control equation for output voltage amplitude dv by using the calculation of reactive currentÎ q as follows:where the term k cÎp constitutes the voltage drop compensator to reduce the effect of gain k q .(1) and (2) provide suitable values of phase angle and magnitude, respectively, of the output voltage v, which isIt means that, with only the measurement of the output current, control scheme calculates and filters (with a lowpass filter) the active and reactive components of the measured current; computes the phase angle hs and amplitude dv by using (1) and (2); and delivers a output voltage reference signal in order to achieve stability and load sharing.A small-signal model, which combines control and circuit equations, constitutes the theoretical proof for stability. It consists in a matrix state equation, where the locus of the eigenvalues give information about the stability of a parallel-connected UPS system and aid the selection of the control gains in a stable point. This equation also includes modeling for the voltage limiters and the voltage drop compensator.Gains of the control equations are also adjusted according to the output power rating, i.e.Doing that, it enables the employment of this control even for multiple UPSs with different ratings.Experimental results, using three UPSs connected in parallel with different output power ratings (the ratio is 6 : 3 : 2) and voltage limiters (±1%), confirm stable operation and good load sharing. The proposed independent control was implemented in a digital signal processor (DSP). Atsuo Kawamura * Member This paper proposes an autonomous control for parallel-connected uninterruptible power supply (UPS) systems based on electrical power system interrelations. The controllable variables are the output voltage phase angle and magnitude. Relation between active current and output voltage phase angle is derived from a synchronous machine model. Electrical power systems suggest that voltage regulation and reactive curren...

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“…Let x and y be respectively the input and output of the limiter. In the region y min ≤ x ≤ y max , y = x (15) . Otherwise, y assumes either y min or y max .…”

Section: Control Equationsmentioning

confidence: 99%

Design of an Autonomous Control for Parallel-Connected Uninterruptible Power Supplies

Sato

Kawamura

2006

IEEJ Trans. IA

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“…Other researchers have been working on the control of node voltage levels to improve voltage stability for transmission networks and distribution grids [8,18,19]. Although many different methods have been proposed for voltage stability analysis, such as small signal stability analysis [20], dynamic power flow analysis [21], time-domain simulation [22], direct method analysis and bifurcation theory analysis [6,23,24]. From the comparison results, it has been found that smallsignal stability analysis of power system stability when subjected to small disturbances is due to the integration of small PV cells.…”

Section: Introductionmentioning

confidence: 99%

Impact of grid‐tied large‐scale photovoltaic system on dynamic voltage stability of electric power grids

Refaat

Abu‐Rub

Sanfilippo

et al. 2017

IET Renewable Power Generation

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Perfect power system voltage stability is not possible in practice. Generally, the power grid is continually exposed to changes in its load and operating conditions. Therefore, dynamic stability analysis is one the most important and effective elements for greater security, stability and reliability of planning, design, operation and economic aspects of electric power networks. This study investigates and reports on the dynamic stability of the power system with a large-scale photovoltaic system (L-S PV). Two different scenarios with centralised PV power plants are considered in the medium voltage level without voltage regulation capabilities. Simulation results with these scenarios will show how the voltage instability decreases with the L-S PV based on the bus status, disturbance location, and disturbance duration. In addition, the study discusses network terminal voltage, generator's rotor angle, generator's terminal current, generator's reactive power and electrical power output. This study is an extension of the earlier published conference paper.

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“…e.g. Reference [1,2] discussed the impact of various exciter models to power systems small signal stability study. Reference [3] analyzed the relationship between power system instability modes and exciter limit.…”

Section: Introductionmentioning

confidence: 99%

Impact of the Exciter Voltage Limit to Power System Small Signal Stability Region

Cao

Jia

et al. 2007

2007 IEEE Power Engineering Society General Meeting

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We investigate the influence of non-differential components to the power system small signal stability region in this paper. A method named unified expression function (UEF) is introduced to describe the piecewise, continuous and nondifferential function in the small signal stability study. It converts non-differential points of the original function to poles of the UEF's derivative function. Then the derivative at those poles can be approximated by UEF's left-hand or right-hand derivative limits according to the requirement. Based on this method, impact of the exciter voltage limit to power system small signal stability region is then deeply discussed using a simple three-bus power system. We find that the exciter voltage limit can change elements of the system Jacobian matrix so as to cause jump of the system critical eigenvalue. As a result, two new Hopf bifurcation boundaries and a new instability hole emerge in the small signal stability region. When the exciter voltage limit varies, the new instability hole and the new Hopf bifurcation boundaries will change significantly. It makes the topological characteristics of the small signal stability region much more complicated. Since there are many non-differential components in power systems, they should be correctly considered in power system stability studies. . His current research interests include application of probabilistic method to system planning, power system stability and control, power system reliability and security, and AI application to power system.

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Effects of limits in small signal stability analysis of power systems

Cited by 13 publications

References 12 publications

Design of an Autonomous Control for Parallel-Connected Uninterruptible Power Supplies

Design of an Autonomous Control for Parallel-Connected Uninterruptible Power Supplies

Impact of grid‐tied large‐scale photovoltaic system on dynamic voltage stability of electric power grids

Impact of the Exciter Voltage Limit to Power System Small Signal Stability Region

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