Epilog

Electric power system transformation is possible by deploying new technologies, structured design and verification methods and proven project management method and tools. Modernized electric power systems get the stamp of modern by using renewable resources, energy from far away to close, from hydropower plants, from wind farms, offshore and onshore, from photovoltaics, from biomass, from solar-thermal and geothermal plants. The steady improvement of power semiconductor technologies regarding functions they can cover and their ratings turns concepts not thinkable before to solutions.

Initially mercury arc converer valves were used for DC power transmission. With the advent of thyristors the converter valves were assemblies of many thyristors connected in series to make up for the voltage and initially also in parallel to increase the current rating. Oil cooled open air converter valves were installed at Cabora Bassa. Very soon water cooled thyristor valves took over, e.g. in the Nelson River II project. Thyristors were fired via electromagnetic coupling circuits, but then fiber optical signals were transmitted to the thyristors and converted to an electrical pulse firing the thyristor. Lateron thyristors had the firing circuit integrated. This is in short the history regarding the converter valves. Voltage and current ratings of the thyristors were stepwise increased which makes now a DC voltage of 1000 kV per pole possible. With a current rating of 4 kA the power per pole is 4000 MW. The bipole transmits 8000 MW. Besides these LCC HVDC systems the VSC based HVDC systems evolved and form now an essential component for the transmission of energy from renewable resources.

In summary we can conclude:

The past of engineering developments shows that confidence in ideas and their realization to solutions is justified. Not all ideas will come through, but at least some will. And this is essential. Diverging knowledge on the subject matter, diverging interests and limited investment capacities (money/personnel) can be reasons for nonacceptance of ideas and dismissing of proposed solutions.

It is the nature of science to develop ideas and concepts, to verify, to falsify, to validate, to sort out, to resume work. Innovations are not possible, at least not possible within a given narrow time frame, without making assumptions on functions, equipment, systems. This generates discussions and finally solutions.

The future power system, its feasibility, its efficiency, robustness and stability must be designed now and continuously in the forthcoming years and decades. Many uncertainties still exist, technical wise and regarding geopolitical impacts. Florence Gaub's  "Future" develops and suggests operating instructions to approach, define and finally master tasks, to navigate through uncertainties, in our context making power and energy supply certain. This is truely an engineering approach. It is not correct to assume that at schools and universities the right thinking is not taught. The experience page shows a model plant. It was part of a doctoral dissertation. That is about 50 years ago. Ideas on stability analysis and controls were developed and verified in the model plant and later implemented in real HVDC installations (items 1 and 2) by the author when working with ASEA BROWN BOVERI and later, when he returned to the university, in education on modern power system technologies.

Universities train critical thinking and orientation towards the future in the engineering disciplines. Training in mathematics, electrical engineering theory, has always to do with making things work, under which conditions are approximations permissible, what needs to be done to replace complex relationships in theory by equivalents and in practice to find smart solutions, to design and build for sustainabiliy, to minimize efforts for best output. It is not the narrow thinking from today to tomorrow, but it goes further and deeper, to implement in design and solutions already the next steps - prepared through research and development. In the larger time frame the future products determine the competitiveness of the enterprise, and in the whole of the country.

Engineering work is per se oriented to the future and continuously reflected: Why do we do this and this? What happens if assumptions fail? What are the scenarios we have to consider? This starts in the first semesters. The theory is not an end in itself, but steadily reflected, used and checked in its application. It is the substance of engineering, the foundation of success and further development. All engineers are trained this way, whether it is fruitful depends to a great deal on the interest and on the persistance of the student.

In the industry the well trained engineer gives his input to the sales group. The best use of the input can be expected when the business structure of a bidding company has a clear focus on core business areas. The various components and subsystems belonging to the total system must be optimized such that best performance and minimum costs are achieved. It is the experience of the author, that this can best be achieved when systems engineering, detailed engineering, the factories, the administration are "one player" working for common success, not split in profi centers where own interests are valued more than the common success. Of course, there must be competition between internal and external supply. However, low price bids from outside sources must be correctly interpreted. In the longer run the own internal supply competence must not be decreased.