Abstract: A sparse voltage measurement-based fault location determination system and method for an alternating current (AC) distribution network is described. This method can use sparse voltage measurements and Bayesian compressive sensing (BCS) algorithm to reconstruct a sparse current vector. A fault location is then determined based on the reconstructed sparse current vector. The disclosed method provides robust fault location results under a variety of asymmetrical fault scenarios. Fewer intelligent electronic devices (IEDs) allocated in the terminal buses are needed for determining the fault location; therefore, this implementation is relatively cost effective.

Abstract: A general design method for phasor estimation algorithms on different applications is described based on a complex finite impulse response (FIR) band-pass filter. To facilitate the design of the complex band-pass filter for different requirements and reduce the trial and error process, a design framework based on the error mathematical models is described. Using an absolute value inequality theorem, the general error models between the filter gain and the error limitations of all the valuables measured by phasor measurement units (PMUs) are established separately. The filter design criteria obtained by the error models can determine the passband and stopband gain range of complex band-pass filters.

Abstract: The wide application of power electronic components in power systems with renewable energy sources has changed the fault characteristics of conventional power systems, resulting in the performance degradation of conventional protections. To solve these problems, a novel principle of pilot protection based on structural similarity and square error criteria is provided. The structural similarity criterion utilizes the difference of fault characteristics between renewable sources and synchronous generators to identify internal faults, and the square error criterion is used to solve abnormal calculation of the conventional similarity based protection. Compared with conventional differential protections, the disclosed protection shows excellent performance in speed and reliability during various faults.

Abstract: A data recovery method framework is described, in which the data is classified as either ambient or disturbance data, and recovered by different methods to achieve good performance efficiently. An approach based on decision tree is described for identifying ambient and disturbance data. Then, an improved cubic spline interpolation based on the priority allocation strategy is described for ambient data loss, which can quickly and accurately recover ambient data. Simultaneously, a disturbance data recovery method based on singular value decomposition is described. It can achieve disturbance data recovery accurately by a single channel of measurement.

Abstract: A detection and location-based active protection method for flexible DC distribution systems with multi-terminal distributed photovoltaic sources is disclosed. The disclosed protection method actively utilizes the coordinated control between local protection and the converters in the DC distribution system. The converter can then be modified to become an injection source with characteristic signal, providing a known fault signal to build a clear protection boundary. The disclosed protection method can distinguish the correct faulted area by calculating the harmonic impedance of the characteristic signals. Compared with existing DC protection techniques, this disclosed method does not require additional injection equipment and modification of the DC distribution system configuration, nor does it need high data sampling frequency. The disclosed technique is also unaffected by measuring noise and cable-distributed capacitance.

Abstract: An improved phasor estimation method for M-class phasor measurement units (PMUs) with a low computational burden is described. The method contains three steps: 1) A phasor measurement filter is designed by selecting parameters of Taylor weighted least square method to prioritize dynamic phasor accuracy and a high level of suppression on high-frequency interferences; 2) A finite impulse response lowpass filter is designed by the equal-ripple method is put forward to suppress low-frequency interferences; and 3) Phasor amplitude is corrected under off-nominal conditions.

Abstract: A general design method for phasor estimation algorithms on different applications is described based on a complex finite impulse response (FIR) band-pass filter. To facilitate the design of the complex band-pass filter for different requirements and reduce the trial and error process, a design framework based on the error mathematical models is described. Using an absolute value inequality theorem, the general error models between the filter gain and the error limitations of all the valuables measured by phasor measurement units (PMUs) are established separately. The filter design criteria obtained by the error models can determine the passband and stopband gain range of complex band-pass filters.

Abstract: A distance protection system and method based on a high-frequency fault component is provided for a renewal energy source (RES) system. The voltage drop caused by a fault has a full frequency of components and this can be extracted by a wavelet transform. A frequency selection principle that renders high-frequency impedance models a stable impedance phase angle is determined. On this basis, internal and external faults with respect to a transmission line are determined by comparing the magnitude of a high-frequency operating voltage with the magnitude of a high-frequency voltage at the fault point. This disclosed protection system and method can eliminate the influence of frequency offset and weak feed of the RES system by using high-frequency signals generated by voltage drops at the fault point, and can also tolerate signal noises and fault resistance.

Abstract: A DC collection system for a PV power plant contains a large number of feeders. When a fault occurs, the fault current rapidly increases, causing electronic devices to block to protect themselves. This blockage presents a challenge to the protection of the DC collection system because of extremely short data windows. To address this challenge, a protection method based on active control of DC/DC converters is disclosed. The fault current control principle is analyzed and derived so that DC/DC converters can provide an injected low-amplitude and controllable post-fault stable current signal. The disclosed protection method is designed based on identifying the direction of the injected signal. Simulation results indicate that the fault section can be accurately identified and that the disclosed protection method performs efficiently against transition resistance and noise.

Abstract: A high-accuracy synchrophasor estimation algorithm for PMU calibration is disclosed. This method can construct a dynamic phasor fitting model. Then, an iterative solution algorithm based on nonlinear fitting can be used to estimate the phasor and frequency, which can include one parameter during the iterations. Moreover, a method is disclosed for calculating the ROCOF based on the least-squares method to improve the ROCOF dynamic accuracy.

Abstract: A high-accuracy synchrophasor estimation algorithm for PMU calibration is disclosed. This method can construct a dynamic phasor fitting model. Then, an iterative solution algorithm based on nonlinear fitting can be used to estimate the phasor and frequency, which can include one parameter during the iterations. Moreover, a method is disclosed for calculating the ROCOF based on the least-squares method to improve the ROCOF dynamic accuracy.

Abstract: A detection and location-based active protection method for flexible DC distribution systems with multi-terminal distributed photovoltaic sources is disclosed. The disclosed protection method actively utilizes the coordinated control between local protection and the converters in the DC distribution system. The converter can then be modified to become an injection source with characteristic signal, providing a known fault signal to build a clear protection boundary. The disclosed protection method can distinguish the correct faulted area by calculating the harmonic impedance of the characteristic signals. Compared with existing DC protection techniques, this disclosed method does not require additional injection equipment and modification of the DC distribution system configuration, nor does it need high data sampling frequency. The disclosed technique is also unaffected by measuring noise and cable-distributed capacitance.

Abstract: A synchrophaser measurement method applied to a P Class Phasor Measurement Unit (PMU), and is based on the dynamic phasor mathematical model. The method includes providing a low pass digital filter for phasor factors and applying Discrete Fourier Transform, so that the spectrum leakage caused by the dynamic phasor inputs is eliminated, and the raw phasor measurements after the spectrum leakage being eliminated can be obtained. In addition, the dynamic phasor inputs are fitted by using the second order Taylor series and the linear relationship between the measurement errors causing the Discrete Fourier Transform averaging effect and the second order coefficients of the Taylor series is explored. The linear relationship is used to correct for the raw measurement errors under a dynamic condition, and the accurate dynamic phasor measurements can thus be obtained. This measurement method can measure phasor accurately and rapidly under both static and dynamic conditions.