Previous work conducted in the unified harmonic domain has been primarily focused on HVDC systems. The paper outlines the extension of this technique to a hard switched FACTS device. A unified harmonic domain model is developed for a STATCOM and solved using a Newton solution based on DC side current mismatches alone. This generic formulation maintains modularity, allowing the interaction between multiple STATCOMs to be studied. The model has been verified against a time domain solution using PSCAD/EMTDC. The proposed technique provides practically identical results, without the time domain's inherent problems with respect to steady-state simulation.

A widened harmonic power flow algorithm is described capable of determining the interaction between the fundamental, harmonic, and interharmonic frequency components. The algorithm is multiphase and can include any number of nonlinearities. The New Zealand power system is used to illustrate the ability of the algorithm to determine the harmonic interaction between an HVDC link and an aluminum smelter.

An algorithm is described that calculates the optimum dispatch of an electrical energy storage (EES) facility taking into account the short-term power exchange and the expected imbalance penalties of a wind farm. The effect of daily price variation, imbalance price spread, market closure lead-times, and wind contracting errors on the added value (AV) of an EES is shown for a range of different EES configurations. Finally, it is demonstrated that significant AV with more than one wind farm is possible where the combined rated power of wind is much greater than that of EES.

Even with state of the art forecasting methods, the short-term generation of wind farms cannot be predicted with a high degree of accuracy. In a market situation, these forecasting errors lead to commercial risk through imbalance costs when advance contracting. This situation is one that needs to be addressed due to the steady increase in the amount of grid connected wind generation, combined with the rise of deregulated, market orientated electricity, systems. In the presence of imbalance prices and uncertain generation, a method is required to determine the optimum level of contract energy to be sold on the advance markets. Such a method is presented here using Markov Probabilities for a wind farm and demonstrates substantial reductions in the imbalance costs. The effect of market closure delays and forecasting window lengths are also shown.

A full Newton algorithm, also referred to as the Harmonic Domain, is used to investigate the charac- teristics of the line commutated voltage sourced converter (VSC). An efficient method is developed for the accurate derivation of the converter harmonic impedances from the Jacobian matrix. The impedances are then used to show the significant effect that the VSC has on the low and high frequency system resonances. It is also shown that the behaviour of a VSC under resonant conditions is different to current sourced converter.

As the numbers of converters and other power electronic devices of large rating increase, the search for the 'ultimate Jacobian' capable of representing the overall system behaviour continues. This paper describes the structure of a flexible Newton framework capable of incorporating the three-phase power flow and harmonic analysis in networks containing multiple AC-DC converters and, potentially, any other types of nonlinearities.

A fast numerical-linearisation technique is used with the harmonic-domain algorithm to calculate the harmonic impedances of AC-DC converters. The accuracy of the new method is illustrated by comparison with existing simplified models. The method is then used to determine the effect of local and remote converter plant on the harmonic impedances throughout the power system. It is shown that it is essential to represent the converter impedance accurately at frequencies below 500 Hz, a region where these impedances have considerable effect on the damping of parallel resonances.

The effect of power converter impedance is mostly ignored when performing harmonic analysis since it is complicated to calculate and a common assumption is that it has minimal effect. This paper compares the use of simplified techniques against a rigorous calculation of the converter impedance and demonstrates their effect on the frequency response of the system.

The unified Newton solution used to derive converter/system interactions in the harmonic domain is extended in the paper to systems with multiple AC/DC converters in different locations. The extended solution is used to investigate potential interactions between the HVDC link and aluminium smelters in the New Zealand system. The inaccuracies of conventional direct harmonic solutions are highlighted by comparison with the results obtained with the proposed general iterative solution

Advanced frequency domain software is used, via graphical interfaces, to provide fast and accurate information of the ac-dc system harmonics, interharmonics and converter impedances on the interactive PC platform.

This paper describes a modular algorithm for solution of power systems containing active nonlinear devices such as power converters. The solution is a unified real-valued Newton method allowing simultaneous solution of electrical and nonelectrical variables. The algorithm is demonstrated using the reduced equivalent of a real power system which includes both load-flow busbars and a large uncontrolled rectifier. The solution process is fast, robust and exhibits excellent convergence

A method for accurate calculation of the harmonics generated by a bipolar HVDC link is described. The method illustrates the importance of including detailed representation of the mutual coupling effects of DC transmission lines, even when smoothing reactors are included. The overall solution is achieved by means of a unified Newton algorithm in the harmonic domain.

To reduce the excessive computation time required to model the generation of interharmonics with Newton-based iterative harmonic analysis, this paper presents an adaptive harmonic domain solution which exploits the inherent sparsity that exists in the harmonic and interharmonic arrays. It is shown that the proposed method produces identical results to the full solution in a fraction of the time

This paper describes an HVDC link modelled within the harmonic domain using a full Newton method for solution. The solution is rapid and robust for a variety of cases and shows excellent agreement with time domain simulation. The HVDC link is also modelled with an extended control system for realistic specification of the steady-state operating point.

A technique is described to model phase-shifting converter transformers in the harmonic domain. The model has been incorporated into a unified Newton solution technique which permits solution of high-pulse installations with parallel DC connections. A variety of test cases are included to illustrate the characteristics of a 24-pulse installation under both ideal and non-ideal conditions. The results show that the characteristic DC harmonics for an individual converter in a multi-pulse parallel connection installation increase with pulse number rather than decrease as with a series connection.

Detailed modelling of the modulation process performed by a converter, especially under unbalanced operation, is a difficult task. Although it can be achieved in time domain analysis it is too slow for interactive work using PC's and does not represent the frequency response of the components accurately, therefore the Harmonic Domain solution is the best option. This paper presents an interactive program (ICHA Interactive Converter Harmonic Analysis) that combines the harmonic domain solution with pre and post-processing graphics to analyse and display ac/converter/dc system harmonic interactions.