Design of Smart Grid Scheme Based on AD7606 Synchronous Sampling ADC

With the advent of low-carbon era, the smart grid is the latest trend in the development and transformation of the world's power system, and it is also a huge system project. China's smart grid [1] is based on a strong grid with coordinated development of UHV grids as backbone grids and voltage-level grids, and combines modern advanced sensing and measurement technologies, communications technologies, information technologies, computer technologies, and control technologies. The new grid formed by the highly integrated physical grid. The smart grid is centered on “safety, economy, efficiency, cleanliness, and low carbon”. It fully satisfies users' needs for electricity and optimizes resource allocation to ensure the safety, reliability, and economy of electricity supply, meet environmental constraints, and ensure the quality of electricity. .

The increasing signal processing technology makes the accuracy of the next-generation system better than 0.1%. The improvement in accuracy is mainly due to the use of high-performance analog-to-digital converter ADC, which provides the needs of future intelligent substation systems. The resolution and performance [2]. The latest generation of 8-channel simultaneous sampling ADC family from Analog Devices, Inc. (ADI) in the US can achieve excellent signal-to-noise ratio (SNR), and optional oversampling mode can further improve SNR performance. The multi-channel integration of the AD7606 facilitates the measurement and monitoring of multi-channel I&V (current and voltage) in intelligent substation equipment. This enables the power line monitoring system to monitor and manage the various abnormal events occurring on the power grid in real time, enabling intelligentization. Substation function integration, system protection, control, and measurement equipment are digitized, and operation management is intelligent to adapt to the development of the power market, ensuring the robustness of China's smart grid.

2 System Architecture A typical electrical secondary device system is illustrated in Figure 1 below. The voltage and current signals of the primary side are connected to the secondary transformer PT/CT. After the signal conditioning, the ADC is input. The data after sample conversion is processed by the CPU/DSP. The control signal is output after isolation, and the status signal is input after isolation.

Figure 1: Schematic diagram of a typical electrical secondary equipment system Traditional grid transformation to smart grid requires secondary electrical equipment to have stronger interface capabilities, control capabilities, protection capabilities, measurement capabilities, communications capabilities, and data processing capabilities, so CPU/DSP And ADCs are generally two key devices that need to be considered in system design.

ADI's Blackfin family of processors meets the development direction of the secondary market for power equipment with its powerful processing capabilities, high performance, and low cost, enabling equipment manufacturers to easily implement versatile or customized functions that can be changed without ( Or rarely change) in the case of hardware quickly adapt to evolving standards and new functional requirements, and greatly reduce product development risk and manufacturing costs. At the same time, on the peripherals, the Blackfin series offers a wealth of choices, thereby providing customers with great design convenience and a wealth of available on-chip design resources. See ADI application engineer Cheng Tao's article "Application of ADI DSP Processors in the Field of Secondary Electric Power Equipment" for more information.

The following will focus on the ADC related parts. ADC is an important part of the data acquisition system. In the traditional design, the resolution of the ADC selected by the system is generally 14 bits, such as the popular 4-channel AD7865 in the industry, the input can accept true bipolar input signals, and provides an 80dB SNR. With the increasing demand for 16-bit resolution and multi-channel ADCs in the industry, Analog Devices has developed a 6-channel 16-bit AD7656 to meet design requirements. With an 86.5dB SNR, the AD7656 provides the performance required to measure small ac signals. However, in the new design requirements, the number of current/voltage transformer CT/PTs included in the system will be many, and the total number of ADC channels is often in excess of 12. As a key supplier of power secondary equipment manufacturers, Analog Devices deeply understands the needs of Chinese customers. Based on the successful application experience of the AD7656, it again introduced the 16-bit AD7606 series of 8-channel simultaneous sampling to better meet the needs of users. Technical challenges in meeting these difficulties.