32 Dsp Power Distribution Monitoring Terminal Design

Distribution Automation is an effective means to enhance power-supply reliability and energy quality. As one of the most important components to the Distribution Automation, Transformer Terminal Unit(TTU) is developing quickly recent years and getting more and more applied to power distribution systems. Apparently,TTU need to sample many analog siganls and do much digital processing work, which necessitate the processor to have high performance in digital processing and A/D convertion. But now most TTU use traditional microcontroler as its processor, but the traditional microcontrolers have poor performance in digital processing and A/D convertion. For this reason, microcontrolers have to add such expensive peripherals to work with it, as high-precision ADC, off-chip high-speed storages and so on. This apparently makes the TTU complex, unreliable, expensive and imprecise.DSPs of C2000 family are specially designed by TI for control purpose. In this family, as We all know, DSPs of C24x (for example TMS320F2407) are 16-bit DSPs. Comparing with the traditional microcontroler, C24x gain great improvement in speed, storage and so on. But in terms of estimating parameters of 3-phase signals real-timely and precisely, their performance are still too poor to meet the critical requirement.C28x are newly-released 32-bit DSPs by TI, having gained a great improvement on their performance. Their excellent performance on digital processing and A/D convertion makes them good for estimating parameters of 3-phase voltage/current signals real-timely and precisely. And their abundant built-in function modules can simplify the design of circuit, save the costs. Their perfect development tools and documentation(for example datasheets, application reports) can speed up the developing process.After a series of analysis, the paper brings forth the design solution of the TTU cored by TMS320F2812. This product includes such functional modules as A/D conversion module, switch-signal input and output module, serial communication module, LCD module, history-record module and DC power supply module, all of which are introduced by this paper.In addition, the related theories and techniques applied in this product are alsodiscussed in detail, such as the basic knowledge of A/D convertion and its quantization error, the estimation of all kinds of electric parameters and their precision analysis, and the fundamental of FFT.On the basis of theory analysis, the software implementations of the modules mentioned above are also introduced. In this product, 128 samples are taken by DSP from each input analog signals per period. From these samples, F2812 works out all the electric parameters needed, such as the mean square roots of voltages and currents, active powers, reactive powers, apparent powers; active energies, reactive energies, power factor, frequency and so on. The software implementation of FFT is also introduced here. At last the test results of the product is also briefly introduced. By the way the paper also brings forward the software implementations of IEC870-5-101 protocol and the code for history record.The hardware of the product is simple, compact and reliable. For the convenience of future function expansion; the software has the feature of standardization and modularity. The model product has been completed by far and the elementary test of the product has passed.In conclusion, it is proved that the product can implement the major functions and meet the requirement of TTU. It is also proved that this product has high value of popularization and wide market prospect.