Pictures of the Future    Spring 2006

Testing with Simulation

Whether it’s complex systems for transmitting power or developing microchips—simulations and extensive advance tests shorten commissioning time and eliminate errors at an early stage.

Long Island fits easily into a hall in Erlangen, Germany—at least that’s the case as far as researchers at Siemens Power Transmission and Distribution (PTD) are concerned. There, experts are exploring how to augment the power supply of the New York boroughs of Brooklyn and Queens, which have a population of 4.7 million energy-hungry inhabitants. The boroughs require additional energy because local power plants can no longer cope with demand. The extra power is to be provided using high-voltage direct-current transmission technology (HVDC, see Undersea Cables). Specifically, planners expect 750 additional megawatts of power to flow to Long Island via a 500-kV undersea cable connection in about two years. The electricity will be generated by a network of power plants near Sayreville, New Jersey.

Before that can happen, however, the entire control system will be built and tested, and the 105-km transmission distance will be simulated in Erlangen. "That way we can shorten on-site commissioning time as much as possible,"says Peter Bermel, the director of the Test and Simulation Center. "After all, the operator wants to earn money as quickly as possible. In addition, potential shortcomings and project planning errors can be eliminated at an early stage—and that will also save time and money."

The control system for the project is housed in 25 electronics cabinets, which are redundantly laid-out control and safety systems, and alarm, diagnosis and communication systems. "First we check the functional capability of all the components. Then we integrate them into the control center," says Paul-Heinz Esters from Industrial Solutions and Services (I&S), who is in charge of start-up operations. Esters then points to the control panels. 15 m of switchgear cabinets for Long Island are located on the right; the cabinet for Sayreville is on the left. That’s also where the power will feed in. The operator’s interface, which consists of about 20 workstations, is located in the center.

Last winter, Ester’s six-person team put the preliminary system into operation. Here, parallel computers simulate power transmission in real-time—including the conversion electronics, switching systems, transformers, filters, lines and networks. During the current testing of the system’s behavior, technicians and engineers can train on the complete system. With 300 tests they have plenty of scope for simulating operating conditions and examining short circuits, network faults or a generator failure. The simulation should also show that the system transmits power stably, reliably and without interruption—even if the networks are disrupted or a failure should arise in one of the redundant control systems.

In July 2006 the electrical cabinets and workstations will be disassembled in Erlangen, packed up and shipped to New York, where they will be reassembled. The engineers who developed the design software and checked the control technology in Erlangen will then carry out a few last acid tests at the customer’s installation. These will include short circuits and load disconnections.

Even as recently as the mid-1980s, the on-site commissioning of a control system took up to one and a half years. Integration tests at the plant cut this to a year. Thanks to simulation, it is now possible to do the job in six months. Naturally, some of this progress is due to the digitization of the control technology and the resulting reproducibility of operations and failure conditions.

Optimizing Chip Designs. In the ASIC Design Center at Siemens Program and System Development in Vienna, Austria, developers simulate the electrical and physical behavior of chips known as ASICs (Application Specific Integrated Circuits). ASICs are special microchips that are used in electronic systems in aircraft, medical instruments, and motor controls. Accordingly, they need to fulfill high safety requirements. The development of such a high-performance chip usually costs from 1 mill. to 3 mill. € and takes up to a year. That’s why customers want to ensure that the components will fulfill desired functions—before mass production begins. That’s possible, however, only if simulation is used. In addition to Siemens Groups such as Medical Solutions, Automation and Drives and Communications, customers of the ASIC Design Center and its 40 employees include small and medium-sized companies.

The complete ASIC design phase takes place on a computer. To ensure that the virtual product is given the desired properties, semiconductor producers supply the ASIC Design Center with models of circuit elements, which developers put together using software. In the process, customer specifications, such as housing type, voltage supply, permissible temperature range and maximum power consumption are specified. The functions are also defined and the circuits then created and simulated virtually.

"We repeat the simulation steps as long as necessary until the chip exhibits exactly the properties the customer has requested and has been optimized,"says chip designer Helmut Wirth. "If an error occurred during the design phase, it would be necessary to make a new chip later. And that would cost between 100,000 and 1 mill. € and delay production by up to six months. Twenty years ago we had to evaluate simulations manually, as the results were only available in printed lists."Today, the output is in graphic form, and comparisons with target values are automated. "That’s essential because of the huge increase in data,"says Wirth, referring to the number of logic elements as an example. In the 1980s each chip had 3,000 to 4,000 logic elements. At the end of the 1980s that figure had increased to about 50,000, before reaching one million in 2000. Today, we’re talking about tens of millions.

"The main challenge is dealing with the constant reduction in the size of structures,"says Wirth. "We’re now facing significant quantum effects for the first time."However, the effects that are dependent on details, such as material, alloy or transistor structure, still have to be described exactly by semiconductor manufacturers. These insights will then flow back into future simulation programs so that experts from the ASIC Design Center will be able to design the best and most effective testing methods for tomorrow’s chips too.
                                                                                                           Evdoxia Tsakiridou