基于Logistic回归模型的电力新能源频率响应方法

常规的电力新能源频率响应方法以频率波动提取为主,易受到频率二次跌落的影响,导致频率响应效果不佳。因此,设计了一种基于Logistic回归模型的电力新能源频率响应方法。首先提取电力新能源共模频率响应降阶特征,从电力新能源频率数据中提取与频率响应相关的特征,简化回归模型处理的复杂性;然后基于Logistic回归模型建立频率响应模式矩阵,映射新能源发电功率与频率响应之间的复杂关系;最后量化电力新能源频率响应限制功率,根据等效惯性常数、负荷变化等指标,确定新能源发电产生的不平衡功率,从而维系电力系统频率的稳定性。试验结果表明,该方法的频率响应效果较佳,具有实际应用价值。

Effects of surface finish and treatment on the fatigue behaviour of vibrating cylinder block using frequency response approach

This paper presents the effects of surface finish and treatment on the high cycle fatigue behaviour of vibrating cylinder block of a new two-stroke free piston engine at complex variable amplitude loading conditions using frequency response approach. Finite element modelling and frequency response analysis was conducted using finite element analysis software Package MSC.PATRAN/MSC.NASTRAN and fatigue life prediction was carded out using MSC.FATIGUE software. Based on the finite element results, different frequency response approach was applied to predict the cylinder block fatigue life. Results for different load histories and material combinations are also discussed. Results indicated great effects for all surface finish and treatment. It is concluded that polished and cast surface finish conditions give the highest and lowest cylinder block lives, respectively; and that Nitrided treatment leads to longest cylinder block life. The results were used to draw contour plots of fatigue life and damage in the worst or most damaging case.

Particle swarm optimization based RVM classifier for non-linear circuit fault diagnosis

A relevance vector machine (RVM) based fault diagnosis method was presented for non-linear circuits. In order to simplify RVM classifier, parameters selection based on particle swarm optimization (PSO) and preprocessing technique based on the kurtosis and entropy of signals were used. Firstly, sinusoidal inputs with different frequencies were applied to the circuit under test (CUT). Then, the resulting frequency responses were sampled to generate features. The frequency response was sampled to compute its kurtosis and entropy, which can show the information capacity of signal. By analyzing the output signals, the proposed method can detect and identify faulty components in circuits. The results indicate that the fault classes can be classified correctly for at least 99% of the test data in example circuit. And the proposed method can diagnose hard and soft faults.

A unified approach of PID controller design for unstable processes with time delay

This paper addresses a unified approach of the PID controller design for low as well as high order unstable processes with time delay.The design method is based on the direct synthesis(DS)approach to achieve the enhanced load disturbance rejection.To improve the servo response,a two-degree of freedom control scheme has been considered.A suitable guideline has been provided to select the desired reference model in the DS scheme.The direct synthesis controller has been approximated to the PID controller using the frequency response matching method.A consistently better performance has been obtained in comparison with the recently reported methods.

The Representation of a Broadband Vector Field

Compared to a scalar pressure sensor, a vector sensor can provide a higher signal-to-noise ratio （SNR） signal and more detailed intbrmation on the sound field. Study on vector sensors and their applications have become a hot topic. Research on the representation of a vector field is highly relevant for extending the scope of vector sensor technology. This paper discusses the range-frequency distribution of the vector field due to a broadband acoustic source moving in a shallow-water waveguide as the self noise of a surface ship, and the vector extension of the waveguide impulse response measured over a limited frequency range using an active source of known waveform. From theory analysis and numerical simulation, the range-frequency representation of a vector field exhibits an interference structure qualitatively similar to that of the corresponding pressure field but, being quantitatively different, provides additional information on the waveguide, especially through the vertical component. For the range-frequency representation, physical quantities that can better exhibit the interference characteristics of the wavegaide are the products of pressure and particle velocity and of the pressure and pressure gradient. An image processing method to effectively detect and isolate the individual striations from an interference structure was reviewed briefly. The representation of the vector impulse response was discussed according to two different measurement systems, also known as particle velocity and pressure gradient. The vector impulse response representation can not only provide additional information from pressure only but even more than that of the range-frequency representation.