What is the Difference Between Digital and Analog?

Real-time digital simulation (RTDS for short) is the product of the development of digital simulation technology, computer technology and parallel processing technology. It not only has the characteristics of digital simulation, but also more important is the use of parallel processing technology and specialized hardware The design guarantees the real-time performance of RTDS and the ability of closed-loop testing, and can complete the real-time simulation of large-scale power systems in 50 S steps.

The requirements for real-time digital control, real-time digital simulation, and general non-real-time digital simulation are different. The latter is not limited by time. It allows to reduce the step size as much as possible and increase the calculation time to ensure that the Stable and achieve high simulation accuracy; however, in real-time control or real-time simulation, due to time constraints and limited digital machine operation speed, all calculations are required to be completed within a specified time. Therefore, we must first focus on the speed and stability. Some classical numerical methods often cannot meet this requirement. Not only do they have a large calculation workload, but they also become unstable after the step size is increased to a certain degree. Even in a critical state, the system can be stable and its simulation accuracy is very high. Poor.

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Digital simulation refers to mathematical or physical simulation performed by discrete or digital computers. The known parameters or reversed parameters of the seepage area are used to debug the model with an electronic computer, and then the groundwater level (head), discharge or water quality is forecasted based on the selected mathematical model.

A real-time system means that the correctness of the calculation depends not only on the logical correctness of the program, but also on the time when the results are generated. If the time constraints of the system are not met, a system error will occur.

The so-called "real-time" means "in time", and the real-time system refers to the system's ability to respond to requests for external events in a timely manner, complete the processing of the event within a specified time, and control the coordinated and consistent operation of all real-time tasks.

The correctness of a real-time system (RTS) depends not only on the logical result of the system's calculations, but also on the time it takes to produce the result. A real-time system is a system that can perform system functions and respond to external or internal, synchronous, or asynchronous time within a specified or determined time. Therefore real-time systems should be able to identify and process discrete events within a predefined time frame; the system can process and store

This paper summarizes several fast and stable digital simulation methods that can be used for real-time control or real-time simulation, and compares the frequency characteristics of these methods through examples. ^[1]

RTDS is essentially a parallel computer system specially designed for real-time simulation of transient processes in power systems. ^[2]

RTDS, as a product in the real-time digital simulation field, has the following main application fields: traditional TNA type research; circuit breaker overlap sequence test research; various relay protection closed-loop tests; power system swing research under large disturbances; AC and DC hybrid systems Research and analysis; DC system control research; SV C application and control; Geomagnetic current effect analysis; Operator training.

Based on the research fields and product characteristics of the Electric Power Automation Research Institute of the Ministry of Power, RTDS is mainly used in the following areas:

Use RTDS in the research and development of new types of relay protection products. As a means of performing some special tests, provide a simulated environment in which relay protection devices actually operate in a power system. Through closed-loop testing with RTDS, ensure relay protection products. Advanced in design and development and reliability in field operation. The main test contents of relay protection products that have been gradually carried out are: simulation tests of relay protection devices under common faults of various types of conventional lines; the impact of series compensation of high-voltage long-distance transmission lines on protection; cross-line faults on double-circuit lines on the same pole Protective action under the circumstances; the impact of the excitation inrush current generated by the transformer airdrop on the protective action; the correctness of the protective action of the shunt capacitors and shunt reactors; the motor protection test; rare faults such as gap discharges, wire breaks, and Ground fault simulation studies.

In general, when using RTDS to test relay protection products, voltage amplifiers and current amplifiers should be provided to amplify the analog output signals of voltage and current simulated by RTDS to replace the secondary of PT and CT in the actual power system. Side output. Some corresponding interface circuits or supporting devices are necessary in specific simulation tests. I used RTDS to simulate the real-time simulation of the second and long-distance line wiring scheme proposed in the "Technical Conditions for Dynamic Relay Test of Line Relay Protection Products". . In the real-time simulation, the effects of considering PT, CT and neglecting the effects of PT, CT, etc. were compared, and the ideal results were obtained. The power monitoring method provided in the real-time operation module is very useful.

RTDS for AVR testing is also one of the application goals. RTDS is used to simulate the primary system and other components in the excitation system to form a closed-loop test environment with the actual AVR. ^[2]

RTDS can also be used for simulation research of high-voltage DC systems, performance analysis of DC control devices, and testing and analysis of other power system safety control devices.