Rafael Cisneros-Magana

Experimental time domain harmonic state estimation using partial measurements

The harmonic state estimation analysis has been conventionally developed in the frequency domain. This methodology needs to measure the amplitude and phase angle of the harmonic components of the related waveforms. This paper presents an alternative time domain formulation based on a simplified network model and Kalman filter to assess the global harmonic steady state estimation. Measurements are sampled waveforms registered by a data acquisition system. The proposed methodology has been successfully tested on an experimental electric power test system developed in the laboratory. The reported case study consists of a three phase balanced system with a nonlinear load. An under-determined measurement model case has been tested. The results have been validated by direct comparison of the state estimation response against the actual data taken from laboratory experimental measurements and have also been compared against the simulated values obtained from Simulink®.

Time-domain harmonic state estimation using filtered measurements based on Fourier transform

Power quality monitoring is required to provide an evaluation of the harmonic status of the power system. However, only a few buses can, with acceptable costs, be equipped with measuring devices. As a consequence, lack of information has to be covered by means of suitable harmonic state estimation techniques. A technique recently developed in the time-domain where Kalman filter has been used for this purpose; however, it requires the harmonic sources, the error covariance matrices associated with the measuring process, the plant model and an initial condition. Besides, it uses serial branch measurements, which in practical cases are not available. The proposed methodology relates the measurement vector with state variables in the time-domain where measurements at sending or receiving end of lines instead of serial branch measurements are used. In order to ensure the appropriate differentiation process needed by the time-domain solution, filtered noisy measurements based on Fourier transform are used. The proposed methodology is validated with a 5-bus test system including linear and nonlinear-balanced loads. A direct comparison of the state estimation response against the actual response obtained from the time-domain power system simulation is performed. Partial measurements have been used to evaluate the harmonic state of the power system. The obtained results indicate that the proposed methodology can adequately assess the harmonic state of the power network.

A Methodology for Transient State Estimation Based on Numerical Derivatives, Optimal Monitoring, and Filtered Measurements

This paper proposes a methodology for transient state estimation in power systems. The proposed methodology is formulated using approximation methods for derivatives to relate the state variables to measurements. It does not require knowledge of the steady state to establish the predisturbance operation conditions. The method uses an optimal monitoring system based on topological analysis to obtain full observability. A saving index is introduced to analyze the effectiveness of the instrumentation used. The adverse effect of noisy measurements in the estimation process is mitigated by using an infinite impulse response filter. A transient index is introduced to estimate the fault location. The transient state estimation is assessed using two test systems. The results are validated through direct comparison against those obtained by simulation using SimPowerSystems toolbox of Simulink. With the proposed methodology, the transient state estimation can be obtained with an important saving in the implementation of the measuring system and with considerably less computational effort.

Harmonic and transient state assessment in the time-domain

Power quality simulation is required to provide an evaluation of the adverse phenomena such as transients, harmonics, and voltage sags in a power system, among others. This paper details a methodology to assess adverse power quality effects. In this methodology, the power system is modeled in the continuous-time by an ordinary differential equations set. The equations set are solved through a numerical integration procedure. The methodology is applied to the modified New Zealand test power system including linear and nonlinear loads. The results are validated through a direct comparison of the state response against the actual response obtained from the time-domain power system simulation performed using the SimPowerSystems toolbox of Simulink®. The obtained results indicate that the methodology accurately estimates power quality harmonic and transient state, respectively.

Methodology for optimal bus placement to integrate wind farm optimizing power flows

This paper proposes an alternative algorithm to locate the optimal bus placement to integrate wind farms based on the criterion of minimizing the electrical losses using the solution of the power flow problem to identify the best connection point. The wind farm is modeled as a negative load being possible to connect this power generation to the possible connection buses and obtaining the power flow solution for each different connection point as a generation change or displacement. The IEEE 14, 30 and 57 bus test systems have been used to validate the proposed methodology. The results have shown the optimal bus among a possible set of them that causes minimum losses when a wind farm is integrated to it.

Parallel Kalman filter based time-domain harmonic state estimation

A time domain methodology is proposed for the harmonic state estimation (HSE) in power systems based on parallel Kalman filter (PKF) algorithm implemented on a graphical processing unit (GPU). The output variable measurements to be used by the HSE are taken from the simulation of the harmonics propagation in the power system. The time domain HSE solution process is based on the application of the PKF algorithm to estimate the waveforms for nodal voltages and line currents with various sources of harmonics, time-varying harmonics and inter-harmonics. The results obtained with the PKF to solve the HSE are validated against the transient program PSCAD/EMTDC. The PKF algorithm is implemented using the Compute Unified Device Architecture (CUDA) platform and the CUDA Basic Linear Algebra Subprograms (CUBLAS) library on a NVIDIA GPU card. Case studies show the effectiveness of the PKF to solve the HSE on the GPU, the speed-up is dependent of the size and complexity of the network model.