J. Arrillaga

Power quality following deregulation

Utility deregulation will have tangible and intangible effects on power quality requiring industry-wide action to maintain adequate standards. These effects are discussed in the first part of the paper. The increasing trend towards more extensive use of power electronic control at the generation, transmission and utilization systems following deregulation has power quality implications that will affect the standards, system simulation and monitoring tools. The paper reviews the present methods available in these areas to achieve specified levels of power quality in the deregulated environment.

An adaptive Kalman filter for dynamic harmonic state estimation and harmonic injection tracking

Knowledge of the process noise covariance matrix Q is essential for the application of Kalman filtering. However, it is usually a difficult task to obtain an explicit expression of Q for large time varying systems. This paper looks at an adaptive Kalman filter method for dynamic harmonic state estimation and harmonic injection tracking. The method models the system as a linear frequency independent state model and does not require an exact knowledge of the noise covariance matrix Q. As an alternative, the proposed adaptive Kalman filter switches between the two basic Q models for steady-state and transient estimation. Its adaptive function allows for the resetting of the Kalman gain to avoid Kalman filter divergence problems under steady-state and allow fast tracking of system variations in transient conditions. Simulation results on the 220 kV network of the lower South Island of New Zealand are presented to validate this approach.

Newton-type algorithms for the harmonic phasor analysis of nonlinear power circuits in periodical steady state with special reference to magnetic nonlinearities

Computer algorithms of the Newton-Raphson type are derived for the harmonic analysis of systems containing nonlinear dynamic components in periodic steady state. The problem is formulated in the complex conjugate multiharmonic space that inherently represents the harmonic coupling between the different harmonic frequencies. The theory is applied to single-phase systems, including magnetic nonlinearities. >

The Harmonic Domain. A frame of reference for power system harmonic analysis

The Harmonic Domain is a general frame of reference for power system analysis in the steady state which models the coupling between phases and between harmonics. In this frame of reference the nonlinear components, converted into harmonic Norton equivalents, are combined with the rest of the system and solved iteratively by the Newton-Raphson technique. This paper describes the structure of the new domain and illustrates its potential applications in a small power system with multiple nonlinearities. >

Three Phase Transmisssion System Modelling for Harmonic Penetration Studies

Three phase modelling of an a.c. transmission system is presented for harmonic penetration studies. Circuit coupling and impedance unbalance are incorporated in a simulation programme which models an 86 bus equivalent of the New Zealand South Island system. A comparison of measured and simulated results at the current injection busbar is used to select system component models; then results of impedances and sequence voltages are presented for selected busbars when the system is subjected to current unbalance and circuit configuration changes.

Computation of A.C.-D.C. System Disturbances - Part I. Interactive Coordination of Generator and Convertor Transient Models

In the presence of h.v.d.c. links the conventional quasi - steady state simulation of power system disturbances is not justifiable. This paper describes a realistic solution which combines the efficiency of single-phase multimachine transient stability analysis and the accuracy of detailed transient convertor simulation. Versatility and moderate computing requirements establish the proposed solution as a viable alternative to the use of analogue simulators.

The application of satellite time references to HVDC fault location

An HVDC fault location scheme is described. It relies on very precise detection of the time of arrival of fault-created surges at both ends of the line. Such detection is achieved by a very accurate data acquisition and processing system combined with the time reference signals provided by a Global Positioning System receiver. Extensive digital simulation is carried out to determine the voltage and current waveforms, to identify the main sources of error, and to suggest possible compensation techniques. >

Transient Stability Improvement Using Thyristor Controlled Quadrature Voltage Injection

A thyristor controlled quadrature voltage injection transformer is used to improve the transient stability performance of a generator connected, through a transmission circuit, to a power-system. The paper discusses the effect of alternative control strategies and shows that not only can first swing maximum angle be reduced, but the subsequent transients can be damped.

The frequency dependent impedance of an HVDC converter

A linear and direct method of determining the frequency dependent impedance of a 12 pulse HVDC power converter is presented. Terms are developed for both the DC and AC side impedances of the power converter, including the effect of the firing angle control system, the commutation period, and the variability of the commutation period. The impedance predictions are verified by dynamic simulation. >

A new STATCOM configuration using multi-level DC Voltage reinjection for high power application

A new STATCOM configuration is described in this paper that combines the advantages of the diode clamped, d.c. voltage reinjection VSC and soft switching concepts. The new scheme uses asymmetrical switches instead of diodes in a common clamping switching circuit for the three-phases of the converter bridges. Detailed analysis is provided of the steady state output voltage and current waveforms. It is shown that this configuration provides very low distortion levels with greatly simplified auxiliary switching arrangements and reduced switching losses.