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1.
The paper proposes an extended complex Kalman filter and employs it for the estimation of power system frequency in the presence of random noise and distortions. From the discrete values of the 3-phase voltage signals of a power system, a complex voltage vector is formed using the well known αβ-transform. A nonlinear state space formulation is then obtained for this complex signal and an extended Kalman filtering approach is used to compute the true state of the model iteratively with significant noise and harmonic distortions. As the frequency is modeled as a state, the estimation of the state vector yields the unknown power system frequency. Several computer simulations test results are presented in the paper to highlight the usefulness of this approach in estimating near nominal and off-nominal power system frequencies 相似文献
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自适应频率跟踪的谐波电流检测方法 总被引:3,自引:2,他引:1
针对电网电压的频率在运行过程中会发生变化,导致谐波电流检测精度下降并直接影响到有源电力滤波器的补偿效果,为此提出了一种基于自适应频率跟踪的谐波电流分频检测方法。该法根据普罗尼谱估法中电导矩阵的频率变化情况,采用LMS算法在线优化从而能独立实时地检测出各相电流中的基波和各次谐波分量,并且直接处理检测结果,具有优良的跟随性能。仿真结果证明了该方法的可行性。 相似文献
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A new optimal approach for improvement of active power filter using FPSO for enhancing power quality
In the recent years, development of industry cause to increase nonlinear and time variant loads in power systems. These loads bring about power quality phenomena such as voltage and current harmonics, current unbalance and flicker in power systems. In this paper, an optimal method for active power filter is proposed to improve power quality. The control system of APF is based on combination of the synchronous detection method, instantaneous power theory, and output of DC capacitor voltage regulator. To stabilize the DC voltage and improvement of reference currents, PID controller is suggested. Regarding to intense changes of load in power system due to nonlinear load, PID controller with fixed parameters could not adequate for the APF control. Therefore, Fuzzy Particle Swarm Optimization method is proposed for optimizing of PID controller. This method is found on PSO and Fuzzy algorithm. To evaluate the proposed method, the APF is modeled in the worst conditions with a power system loaded with two electric arc furnace. In addition, in order to make good use of frequency changes in the power system, the power frequency estimation is put to use. 相似文献
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《Electric Power Systems Research》2006,76(9-10):808-814
This paper introduces genetic algorithms (GA) as a powerful tool for monitoring and supervising power system disturbances generated due to dynamic performance of power systems. Monitoring power system disturbances involves monitoring fundamental voltage magnitude and its frequency as well as harmonic and sub-harmonic voltage magnitudes and their frequencies under different operating conditions for power quality evaluation purposes. The proposed method is based on genetic algorithms optimization technique. The method uses digital set of measurements for the voltage or current waveforms at power system bus to perform the estimation process digitally. The algorithm is tested using different simulated data to monitor power quality. Three different study cases are considered in this work. In the first part, the estimation of voltage flicker levels and its frequency is presented and discussed. In the second part, the frequency of a bus voltage signal that is contaminated with harmonics is estimated. The harmonic contents are also estimated in this case. In the third part, the analysis of a damped sub-harmonic signal is presented. Effects of number of samples, sampling frequency and the sample window size are studied. Effects of GA parameters and operators, such as population size, crossover, mutation probabilities and niching are also studied. Results are reported and discussed. 相似文献
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Proper estimation of voltage parameters has a significant meaning for power converters control systems. One of the measured parameter, directly associated with control process, is frequency of the basic voltage component at the converter output. Unfortunately, power converters generate a wide spectrum of harmonics as well as interharmonics, that makes difficulties in estimation this frequency. Measurement carried out in industrial applications exhibits complex nature of investigated signals often corrupted by resonances or overvoltages phenomena. It entails searching a new digital algorithms for frequency measurement. This work presents algorithm using modification of high-resolution Prony method connected with digital filtering. The investigations was based on simulations and real measured signals recorded in two different commercial PWM converters. Obtained results indicate accuracy of the method as well as its fast response. 相似文献
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与电力系统静态估计不同,动态估计可以准确的跟踪系统状态,并在电力系统保护和控制中发挥重要作用。以往在做状态估计时,通常将非线性测量函数进行泰勒级数展开,舍弃二次及以上的高阶项,不可避免的造成估计误差。本文针对电力系统中的量测方程是直角坐标下电压实部和虚部的二次函数,借鉴保留非线性潮流算法中保留二次项的思想,结合无迹变换,提出基于保留二次项迭代的电力系统动态状态估计算法,该算法在卡尔曼滤波过程中进行泰勒级数展开时没有近似,精度更高。基于IEEE39节点标准系统进行仿真分析,仿真结果表明,本文所提算法是有效的,且估计精度相对不保留二次项得到了提高。 相似文献
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M.M. Canteli A.O. Fernandez L.I. Eguiluz C.R. Estebanez 《Power Delivery, IEEE Transactions on》2006,21(3):1101-1105
The utilization of Clarke's transformation in the estimation of power system frequency provides the classical single-phase methods with more robustness because the estimated frequency is computed using the information provided by the three-phase voltage. This approach is particularly important when asymmetric sags generate zero voltage in one of the three phases. In addition, the proposed algorithm exhibits good behavior during dynamic conditions. The Clarke components of the voltage signals are then used to compute the frequency of the system following an iterative approach based on a proportional-integral-derivative controller. The inverse component of the voltage is also used in order to detect unbalanced conditions. The proposed algorithm has been put to the test with distorted three-phase voltage supplied by an arbitrary waveform programmable power supply and with different signals generated with an Alternative Transients Program-Electromagnetic Transients Program model. 相似文献
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聂晓华 《电力系统保护与控制》2013,41(18):89-95
强跟踪UKF算法是采用Unscented策略逼近非线性分布且强跟踪系统突变的状态估计算法,该算法兼具强跟踪算法鲁棒性强、Unscented变换精度高、实现简单的优点。针对光伏系统在部分遮蔽情况下最大功率点误判问题,结合恒压法与强跟踪UKF算法,提出了一种新的光伏系统MPPT策略。采用恒压法快速定位最大功率点的电压范围;在该电压范围用尽量小步长的控制电压,以相应瞬时功率作为被估量,采用STUKF算法精确估算最大功率点,确定相应控制电压;保证光伏系统MPPT跟踪速度基础上,提高跟踪精度,通过状态跟踪判断状态突变,避免了误判问题。仿真和实验验证了所提策略的正确性、有效性。 相似文献
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In this paper, new digital instruments measuring power-quality indicators and harmonic analyzers are developed. A new technique for simultaneous local system frequency and amplitudes of the fundamental and higher harmonics estimation from either a voltage or current signal is presented. The structure consists of three decoupled modules: the first one for an adaptive filter of input signal, the second one for frequency estimation, and the third one for harmonic amplitude estimation. A very suitable algorithm for frequency and harmonic amplitude estimation is obtained. This technique provides accurate frequency estimates with error in the range of 0.002 Hz and amplitude estimates with error in the range of 0.03% for SNR = 60 dB in about 25 ms. The theoretical basis and practical implementation of the technique are described. To demonstrate the performance of the developed algorithm, computer simulated data records are processed. Data of the distribution power system voltage signals are also collected in the laboratory environment and are processed in a newly developed digital PC-based harmonic analyzer. It has been found that the proposed method really meets the need of offline applications. Even more, by using the parallel computation algorithms, this method should meet the need of online applications and should be more practical 相似文献
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基于阶跃扰动的惯量评估方式依赖难以准确测量的初始频率变化率(RoCoF)与稀少的频率事件,而基于类噪声扰动的惯量评估方法无法评估电流源型虚拟惯量且对数据要求高。对此,提出基于可再生能源机组主动输出斜坡渐变扰动功率的惯量评估方法。建立含RoCoF与斜坡渐变扰动功率的等效惯量评估基础模型。考虑RoCoF噪声阶跃易导致等效惯量评估产生较大误差,推导双二阶广义积分锁相环中的q轴电压分量变化量与RoCoF的线性关系,并将其代入基础评估模型替代RoCoF。采用改进的非线性最小二乘拟合斜坡渐变扰动下q轴电压分量变化量与时间的非线性表达式,从拟合的表达式中提取系统等效惯量。在改进的EPRI-36中验证了所提评估方法相较于常规方法的优越性。 相似文献
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ABSTRACT Frequency deviation from its rated value and its rate of change are indications of load imbalance in power systems. Frequency relays which detect frequency deviation and its rate of change and react accordingly are implanted in power systems to ensure the safe and efficient operation of power systems. This paper presents a new application for a discrete filtering based on least absolute value parameter estimation algorithm (DLAV), which was developed recently by the authors, for on-line measuring of the steady state frequency, the frequency deviation as well as the voltage magnitude and and its phase angle from a noisy measurements. The proposed algorithm uses the digitized samples of the power system voltage at the relay location. The proposed algorith can easily handle the time-varying magnitude of the power system voltage, if any. In this paper, two models are used,namely the two-state model and the six- state model. The order of the second model depends on the number of terms taken from Taylors series expansion. We assume, in this paper, that the power system frequency is constant during the data window size. In this paper we compare the proposed algorithm and the well-known Kalman filtering (KF) algorithm. Test results are reported in this paper, which forms the basis for our conclusion at the end of the paper. 相似文献
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A new approach to the design of a digital algorithm for direct estimation of voltage phasor, frequency and its rate of change is presented. The algorithm derived is based on Newton's iterative method, very commonly used in the field of unconstrained optimization studies. A five-parameter voltage model was assumed, so the result of the estimation was a parameter vector, consisting of the following unknown parameters of the voltage signal processed: its DC component, magnitude, phase angle, frequency and its rate of change. To demonstrate the performance of the algorithm, off-line computer simulation results are presented. The algorithm showed high measurement accuracy over a wide range of frequency changes. The algorithm ‘order two convergence’ provided a very good dynamic response as well as a fast algorithm adaptability. The new algorithm seems to be a particularly useful tool in the field of frequency relaying as well as in various aspects of power engineering applications. 相似文献
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An approach to the design of a digital algorithm for network frequency estimation is proposed. The algorithm is derived by using the Fourier and zero crossing techniques. The Fourier method is used for digital filtering and the zero crossing technique is applied to the cosine or sine components of the original signal, which is usually corrupted by higher harmonics. The algorithm showed a very high level of robustness as well as a high measurement accuracy over a wide range of frequency changes. It can be used for frequency tracking in power networks when higher harmonics are present in the voltage or current signals. The theoretical basis and practical implementation of the technique are described. The performance of the developed algorithm has been verified by the computer simulations, and the field and laboratory tests. 相似文献
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Harmonic estimation in a distorted signal along with additive noise has been an area of interest for researchers in many disciplines of science and engineering. This paper presents a new algorithm to estimate the harmonics in power systems using genetic algorithms (GAs). The harmonic estimation problem is linear in amplitude and nonlinear in phase. The proposed hybrid algorithm takes advantage of this structure and iterates between linear least squares amplitude estimation and the nonlinear GA-based phase estimation. Improvement in both convergence for solution as well as processing time is demonstrated from this algorithm. 相似文献
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Frequency recording units (FRUs), designed to measure power systems' frequency at low voltage, are affected by the connection of large loads causing sudden phase shifts and magnitude changes in the voltage. These phase shifts introduce spikes in the frequency measured by FRUs. In this paper, we propose an algorithm to detect the phase shifts and to produce an accurate frequency estimation regardless of load changes. 相似文献
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Boris A. Alcaide-Moreno Claudio R. Fuerte-Esquivel Luis M. Castro Enrique A. Zamora-Cárdenas 《电力部件与系统》2015,43(13):1534-1547
This paper proposes a practical approach to incorporate the mathematical models of both fixed-speed and variable-speed wind turbine generators, automatic load frequency controls as well as voltage magnitude and frequency dependent loads into a weighted least squares-based state estimation algorithm suitable for the analysis of flexible alternating current (AC) transmission systems. As opposed to conventional static state estimators, where the inclusion of these electric components has been neglected so far, the proposed approach permits the determination of the steady state operation of a power system in the event of a supply-demand unbalance by estimating the magnitude of the frequency deviation from its nominal value. The state estimation is based on measurements related to those that should be obtained by a supervisory control and data acquisition (SCADA) system and phasor measurement units. For the purpose of this paper, the set of values associated with SCADA measurements (nodal power injections, power flows, and voltage magnitudes) and phasor measurement unit (PMU) measurements (voltage and current phasors) are generated from a power flow analysis of the network under study. Lastly, numerical simulations are reported to demonstrate the effectiveness of the proposed approach. 相似文献