Advanced Materials Research Vols. 960-961

Abstract: Research of power flow evenness has great significance for grid steady state analysis. This paper researched for a method for power flow evenness analysis through entropy theory. According to current power flow distribution and branch power limits, the branch load ratio distribution could be obtained, and the power flow entropy was calculated based on discrete information entropy theory. The study case indicates that the power flow entropy effectively describes the power flow evenness. With certain system load level, the system security level will be dramatically declined when power flow evenness reduces to a certain level, which is demonstrated in the case meanwhile. Power flow evenness analysis based on entropy theory is applicable in power system static security assessment.

Abstract: Nowadays, unbalanced loads or nonlinear loads produce a bad effect on the power quality of utility mains. Also, it is necessary for reactive power to be compensated because the most of industrial loads is inductive and make a lagging displacement power factor. Reactive power compensation utilizing STATCOM is one of the most important methods to improve power quality. In this paper, the technical feature of STATCOM is introduced and then a comparison with SVC is made. The effect of STATCOM on static voltage stability in power systems has been studied. Based on PSD-BPA software, effect of STATCOM is determined. Static voltage stability margin enhancement using STATCOM and SVC is compared in the modified IEEE 14-bus test system. Test results show very encouraging result.

Abstract: Nowadays the main electrical wiring in medium-size and large-size thermal power units is mostly unit wiring. In the quarter of small reactive power load, some generators need to work in phase-lag operation during the daytime and in phase-advancement operation at night to meet the demand of voltage quality of their plant’s high-voltage side. This operation, however, will lower the voltage of auxiliary power and do harm to system’s stability. This paper proposes a kind of coordinated control strategy for generator-transformer’s voltage regulation. In this strategy, the main transformer should be on-load tap charger and the controller regulate the generator voltage and transformation ratio simultaneously when needed, thus the voltage quality of both high-voltage side and auxiliary power side can be insured and the generator no longer work in phase-advancement operation. This control strategy can be a meaningful proposal for AVC in smart grid in the future. Simulation result shows the stability and reliability of the proposed control strategy.

Abstract: Based on polytrophic process of air compression and gas combustion inside the turbine isothermally, an approximate gas-turbine with General Carnot cycle and relevant implementing schemes are suggested. Its performance was predicted with mathematics model compared with traditional one. The results show that the heat efficiency of the suggested gas turbine is higher than the traditional one. The suggested cycle combines the gas cycle and steam cycle, of which the NOx emission can be easily decreased

Abstract: For the output requirements of low ripple voltage and high precision exciting current for ferromagnetic power, The combination of DSP and FPGA is put forward to the magnet power supply controller design scheme, First ,The power source controller hardware system is given, then the signal conditioning circuit, the intermediate link of data processing and the backend driver circuit of system is Introduced in detail, Finally gives control process of the program of the controller software design for the main program and PWM dead zone.

Abstract: Saturable magnetic circuit is a common phenomenon in power system. It can lead to waveform distortion, coefficient of self-inductance decrease and measurement error increase. So establishing a mathematical model for saturable magnetic circuit and revealing the mathematical relationships in saturable phenomenon. It is helpful to reliable and safe operation of power system. This paper base on double expontential function fitting algorithm and simplex algorithm to establish the function relationship between relative permeability and magnetic field intensity. Applying for the model,we can obtain the waveform of magnetic flux in transformer core and transformer voltage waveform. The research has certain significance in the abstract and foreground in the application for the study of saturable phenomenon.

Abstract: Considering decentralization of the micro-source units and loads in the micro-grid and concentrating on generation types and models of the storage devices, droop control strategy is used in controller design for the distributed generation units. The generation units adopting droop control method based on the droop characteristics can facilitate load power sharing when the powers of loads vary, and can also maintain the system frequency when a unit fault occurs and the micro-grid islands. Then, the operation variations of the micro-grid are analyzed when it runs with load changes in islanding mode and runs with the load power of micro-source varied suddenly. The corresponding rules of the active power, voltage and current for each micro-source and the frequency for the micro-grid are obtained. The simulation data results show the correctness and validity of the droop control strategy.

Abstract: PID controllers are widely used in industrial process control. The determination of the conventional PID controller parameter tuning is based on obtaining the mathematical model of controlled objects and according to certain rules, which is difficult to adapt to complex control systems. In this paper ,against its adverse effect parameter tuning, long time debugging, defects and poor adaptability of the controlled object,the fuzzy control and PID control are combined and the fuzzy PID controller is proposed. Then, I combine the examples of thermal power units using MATLAB to simulate. The simulation results show that the fuzzy self-tuning PID controller not only has the advantages of fuzzy control such as fast, adaptability, etc, but also the characteristics of high accuracy PID control, which make the system has a good control effect.

Abstract: Hydropower is the most widely used renewable energy for electricity generation in China, and small hydro power plant (SHPP) is a flexible way of electricity generation in water-rich remote area. Voltage at the end of distribution network may be increased over the acceptable range due to the connection of SHPPs. Magnetic control reactor (MCR) is usually used to reduce the voltage by consuming reactive power. A mathematical model for calculation of the optimal capacity of MCR is proposed in this paper, and particle swarm optimization (PSO) is adopted to solve the optimization problem. Two cases based on the IEEE 33-bus test system are used to validate the proposed method. In the given cases, system voltage is adjusted to the acceptable range.

Abstract: Aiming at the digital device test, design a automatic test system, introduced the concept, architecture and technology. The PC sends SMV to digital device based on IEC61850-9-2, Then receive real data from device through the PC serial based on IEC103, constructing a loop, then completed the test. Software static structure adopts the modular programming, dynamic data exchange uses multithread. According to the configured test case, test items can be completed automatically. The system is based on PC, compared with the traditional test instrument to save hardware cost. With the help of calculation and control capabilities of the PC, realize the automatic testing, make people liberation from repetitive work, more focused on the analysis of test results, improve test quality and efficiency.