Member of JNC for ICEE, Masakazu Kato Member of JNC for ICEE,

1. Methodology and Perspectives

The importance of studying a global power system is now deeply understood among people in the world, as has discussed on many well known occasions. (1)

Electric power is one of the most efficient and safest energies in the modern society. Accordingly, interconnection of electric power systems will go a long way as an environmental protective measure, if it is designed to meet the needs of society in the future.

However, we must be careful that such an important issue as "environmental effect and strategy of power generation in Asia to the year 2030" should not be discussed in a sensational or political manner. Discussions must be grounded in sound data and facts.

This paper provides the public with a tool for rational and fruitful discussion of the issue: the computer model composed of mathematical formula which deal with reasonable and practical data.

The computer model is a flexible decision support system, under the uncertainty that can be used in discussions between decision makers and specialists for issues like power systems interconnection, because participants can exchange practical views and rational opinions on the data and scenarios shown on the view panel.

Every engineer interested in the subject of power systems interconnection must know that organizers of both IEEE and CIGRE activities are very attentive to the subject and have held several sessions and symposia in this field, e.g. the CIGRE Bangkok Symposium 1989, "Operation of electric Power Systems in Developing Countries" and the panel in IEEE 96 SM, "African Electricity Infrastructure, Interconnection and Electricity Exchanges."

In the session entitled "Project Development." Chaired by Mr. Arakawa, at the International Symposium on "Sustainable Energy Development in Asia" (Hong Kong, 9th May 1996) Mr. Prutichai of EGAT introduced eight interconnection projects initiated by ASEAN member countries in 1982 and highlighted the difficulty of promoting the ASEAN Grid Project due to geographical and financial constraints, low load demand and dependency on power plant projects. (2)

In August 1996 ICEE '96 was held in Beijing at which time a panel under the title of "Interconnection of power grids" was organized and four papers from China, Korea, Russia, and Japan were presented. Mr. Zheng Meite (CEPRI) focused on the energy excess in Siberia and the shortage in North China expected the year 2000 and 2010 (3)

Dr. Sae-Hyuk Kwon (KU), et. al., of Korea cited the current loosening of socio-political tensions in Korea could be a positive stimulus to promote the program. He recommended that ICEE create a Working Group for the promotion and study of the Far East Asian Interconnection to encircle the Japan Sea with transmission lines and cables. (4)

Mr. N. I. Voropai and G. V. Shutov (SEI) Focused on energy resource allocation and load curve difference between widely separated areas on the Eurasian Continent. They estimate 15GW of potential power exchanges between East Siberia and Japan, 18-20GW of potential savings in the installed capacities in Japan. (5)

Mr. Arakawa (EPDC) discussed interconnection as follows: It is now quite important to study global power systems not only for technical reasons but also for the sake of environmental protection. Interstate power grid interconnection is technically and financially feasible, when a project is commercially attractive. As the difficulty is composed of social, political and cultural factors, mutual understanding among peoples concerned will be the key to the success. Electrical engineers are supposed to provide people at the socio-political level with reliable data for the project. The Japanese people are eager to contribute to the peace and prosperity of the world. (6)

2. Technology to Support the plan

The electricity trade is quite popular and productive in Western Europe and between Canada and the US because both of these areas geographically close, economically interdependent and share similar political orientation and cultural heritages. Also, it must be pointed out the HVDC technology provides a reliable infrastructure which facilitates an interconnected system.

In Korea recently, an interconnection system with HVDC of 150MW was put into service between the Peninsula and Cheju island. In China, it is considered a magnificent milestone in the history of power development that a +- 500kV HVDC project was successfully completed to transmit power from Gezhouba Hydro-power Plant to Shanghai, interconnecting the two major regional networks of Central China and East China. In Japan, the Kii Channel HVDC Link, with 48 km of 500kV submarine cable. 51 km of overhead line and 2800MW converter stations, is currently under construction and planned for completion in the year 2000. This follows the successful connection of Hokkaido-Honshu with an HVDC link in 1979.

Due to the development of semiconductor technology, high power self-turn off devices such as GTO (Gate Turn Off Thyristor), which can turn off current at any time are now available. Because the self-communication converter is operated by the voltage source, it has several advantages over the HVDC system with conventional line commutation converters.

The self-commutation converter technology has been applied to the Static Var Compensator (STATCOM), Eight GTOs of 6kV-2.5kA for a 50 MVA STATCOM at Shin-Shinano substation, installed in 1993, are connected in series to reach DC 16.8 kV and operated with high reliability.

As an example of its application to HVDC and FACTS (Flexible AC Transmission Systems), the control strategy for multinational HVDC with self-commutation converters has already been developed and reported.

At present, the losses and the costs of self-commutation converters are higher than that of line commutation converters. However, significant development in self-commutation converter technology, as well as semiconductor technology, promise to make self-commutation converters economically feasible in the coming years. Interstate interconnections will be even more advantageous due to the application of these advanced technologies in the near future. (7)

Due to its remarkable characteristic of "zero resistance." SC (superconductivity) is another important and effective technology in establishing a reliable and sophisticated power system, particularly in terms of long-distance interconnection. Though high temperature SC material is not yet produced industrially, SC will play an active role in various aspects of power systems and social life in the form of SC generators, SC cables, SC converter stations, SMES and medical facilities, electronic equipment for multimedia systems, etc. The characteristics of SC are not limited to "zero resistance." There is much to be gained from utilization of other SC characteristics such as pinning by magnetic force and Josephsson Effect.

The Silk Road Model ("SRM") (8)

3.1 Area in "SRM"

The simulation model, "SRM," for a feasibility study of interconnection in the Eastern area of the Eurasian Continent for around the year 2020, is composed of seven power systems in a heavy demand area in central Russia, a hydropower supply area on the River Yenisei, a solar power supply area in the Gobi desert, a fossil fuel power supply area in Siberia, a large demand and supply area in central China, Korea and Japan

Another simulation case includes hydraulic power, planned to be developed in Chinsha Chiang on the River Yanze in China, instead of solar power in the Gobi Desert. Fig. 1 shows "SRM with solar power in the Gobi Desert. The capital costs are figured to the simulation for hydraulic power plants in central Russia and natural gas combustion power plants in Siberia as well as hydraulic power plants along the Chinsha Chiang as they will be newly installed. Solar power plants in the Gobi Desert, of which maximum available capacity is 50 GW, however, have already been installed, so, the capital cost is not counted. Instead M&O (maintenance & operation) costs are figured into this simulation.

3.2 Simulation Data

Since the purpose of this simulation is to evaluate possible interconnections from an economic point of view, technical data regarding converter stations and transmission lines are actual and up to date, while the other data are generated from reasonable assumptions.

Simulation data include: Seasonal daily load curves (every four-hours) for each system. Combination of generation plants in each power system. Transmission line resistance.

Data for the objective function includes: Production unit cost for each kind of generation plant in each power plant in each power system. Equipment and installation cost for a converter station per MW, annum. Equipment and installation cost for a transmission lines per MW, per Km, per annum.

Production unit cost is introduced based on the future energy source cost estimation, transportation cost and so on. Equipment and installation costs are estimated at a little less than current costs due to expected technology development.

3.3 Objective Function

Objective function is as follows; Total Annual Cost (V)= Constraints: Generation Plant Capacity Converter Station Capacity Transmission Line Capacity Demand Supply Balance where

In "SRM," the value (V) of objective function, that is the sum of cost for power generation, transmission and converter stations, shall be minimized under the constraints of transmission loss, supply-demand balance, generation capacity, transmission capacity, and converter capacity. A hypothetical node (H) is set on a branch in the system to evaluate the feasibility of the interconnection. If the transmission capacity between the two nodes, or two power systems, is positive under the minimum value condition of V, then interconnection is feasible. The simulation should be conducted to minimize the objective function under the constraints given by the parametric data of peak load, load curve, generation capacity, generation cost, load factor of hydropower station, converter station capacity and transmission loss.

In the model, transmission loss is a very important factor in such long transmissions. As its characteristics are a quadratic expression of transmission power, it is introduced as piece-wise linear to the model.

3.4 Simulation Cases

Following scenarios are simulated for a feasibility study by "SRM." As a base case (Case-0), we evaluate the total annual cost without interconnections. Two types of base case simulations have been conducted, one case (Case-1-*) being with solar power in the Gobi Desert and the other case (Case-2-*) being with hydraulic power along the Chinsha Chiang. Simulation cases are summarized in Table 1.

In two types of simulations, besides base cases (Case 1-1, 2-1), cases with double annual cost for a transmission line between Korea and Japan (Case 1-2, Case 2-2) have been simulated. "Double annual cost" includes a submarine power cable. Another case includes a converter station installed at the east end of the Russian UHV transmission network (point in Fig. 1) (Case 1-3). This leads to shorter power transmission lines between the Russia System and China System than the base case (Case 1-1).

3.5 Simulation Results

Simulation results for total annual costs and optimal installation capacities of converter stations and transmission lines are shown in Table 2. In this table, total annual costs are calculated in relation to the Case-0 (no interconnection).

For Case 1-1 as well as Case 2-1 (base cases), interconnections, excluding Russia System, are economically advantageous. The total cost in each of these cases is lower than that of Case-0by 1.7% in Case 1-1 and by 1.0% in Case 2-1. Two new bulk generating areas, solar power in the Gobi Desert (Case 1-1) and hydraulic power along the Chinsha Chiang (Case 2-1), and natural gas combustion power in Siberia, are interconnected as well in these cases. China System generates more power than its demand, while Korea and generate less than their demands. Since all systems pay or take surplus production costs from each another, it is possible for all to benefit even when equipment and installation costs are paid.

The simulation results, conducted with reasonable equipment and installation costs, show the economical feasibility of interconnections between China, Korea, and Japan. It is quite notable that economic feasibility was shown even when annual costs for the transmission line between Korea and Japan included as double.

It will be interesting that, in both cases (Case 1-2, Case 2-2), interconnection capacity is lower than that of the base cases. And natural gas combustion power in Siberia is economically attractive.

If the Russian UHV transmission network reaches the east end and interconnection there is available, in Case 1-3, interconnections with Russia System will bring much more economic merit. In this case, the direction of electric power flow along interconnections changes, depending on the demand of each system for the day.

Fig. 2 shows an example of power flow profiles during summer period in Case 1-1.

4. Conclusion

Japanese power systems engineers have long dreamed of encircling the Japan Seas with transmission lines and cables. This dream is now popular among people throughout Asia. Then, why has not the dream been made into reality?

So far as available technology is concerned, there are almost no difficulties to overcome, as noted in the second chapter of this paper.

How about money? In the 16th Congress of the World Energy Council, Mr. A. A. Churchill, an American energy consultant, displayed the English sense of humor in his presentation entitled "Money is not the problem: It is the answer." (9) If I understand him correctly, it means that people would like to invest in any project, as long as it is commercially attractive. (9)

Then, there are political and diplomatic issues. Today, as Dr. Kwon (4) tells us, the political climate in East Asia is becoming more conductive to the successful promotion of power systems interconnection beyond national borders. But should we be so optimistic?

As we have witnessed regional disputes break out all over the world after the end of the Cold War, we must ensure a sound basis for international cooperation among the countries concerned. This is not only a political issue but, much more importantly, a social and cultural problem to be solved not necessarily by politicians but by people in all walks of life. This is the reason why I put much more importance on education and grass root activity. It takes time for people from different societies and cultures to achieve mutual understanding necessary for successful international cooperation. (10)

References

1. World Energy Council 16th Congress: "Technical Program," Oct. 1995
   
   
2. Prutichai Chonglertvanichkul; "Planning of ASEAN Grid," Panel on Project Development at the International Symposium on "Sustainable Energy Development in Asia," May 1996 Hong Kong.
   
   
3. Zheng Meite; "A Study on the Interconnection of Power System in China," Panel on Interconnection of Power Grids, August 1996 ICEE'96, Beijing China
   
   
4. S-H Kwon et al: "Consideration on Interconnecting Electric Utility Companies in Far East Asia," Panel on Interconnection of Power Grids, August 1996 ICEE'96, Beijing China
   
   
5. N.I. Voropai, G.V. Shutov; "The Conditions and Possible Trends in Formation of Interstate Interconnection in East Asia," Panel on Interconnection of Power Grids, August 1996 ICEE'96, Beijing China
   
   
6. F. Arakawa "Panel 3 Interconnections of Power Grids-The Japanese Point of View-" ICEE'96, Beijing China
   
   
7. K. Sakamoto, et. Al. "Development of a Control System for a High Performance Self-Commutated AC/DC Converter" IEEE SM 1997 held in Berlin
   
   
8. M. Kato, et. Al." A Feasibility Study on Interstate Interconnections of Electric Power Systems in Asia by the Application of Advanced HVDC Technology" Sino-Japanese Symposium on Sustainable Development and Advanced Science and Technology, Lanzhou Aug. 1997
   
   
9. Churchill, Anthony A.; "Money is not the Problem: It is the Answer," 16th World Energy Congress, Tokyo Oct. 1995
   
   
10. Arakawa, Fumio; "Power System Planning in Japan-Contribution of Engineers to the Global Society--," IEEE/PES-WM, Feb. 1991

---