Harmonic Resonance Mode Analysis Research Articles

Mathematical representation of harmonic resonance phenomenon and harmonic compensation in PMSG based wind farms under feedforward compensation of the grid voltages

This paper mainly focuses on harmonic resonance analysis and harmonic compensation in electrical power grid including PMSG-based wind turbines. In this way, first, harmonic resonance representation and impedance model of the study system is presented by taking the grid-side converter control into account. Then, it is mainly dealt with the harmonic resonance analysis in the study electrical power grid under feedforward compensation of the grid voltages. In this paper, under feedforward compensation of the grid voltage, impacts of the bandwidths of the voltage/current measurement filters on harmonic resonance response of the system are investigated by using frequency scan and harmonic resonance mode analysis (HRMA) approaches. It is shown that by increasing the voltage measurement filter bandwidth, resonance damping is weakened and the magnitudes of driving point impedances increase. Hence, feedforward compensation of the grid voltage in a limited frequency range results in better resonance damping in comparison with feedforward compensation in a wide frequency range. On the other hand, by increasing the current measurement filter bandwidth, the new resonant modes are not added to the network. It is also shown that employing passive filters significantly reduces the driving point impedances of all buses at the different harmonic orders.

Optimal power quality monitor placement to ensure reliable monitoring of sensitive loads in the presence of voltage sags and harmonic resonances conditions

Nowadays, sensitive nonlinear loads such as load commutated inverter drives are increasingly being used by industrial consumers. In one hand, sensitive nonlinear loads can induce parallel resonance condition to the network and in the other hand their continuous operation may be interrupted due to voltage sags. Therefore, power quality parameters associated with the secure performance of sensitive nonlinear loads must be monitored to avoid the adverse effects of parallel resonances and financial losses due to voltage sags. In this paper, a new approach based on the area of vulnerability to voltage sags and harmonic resonance mode analysis is proposed to determine the optimal number and the best location of power quality monitors (PQMs). The proposed method is formulated as a linear integer optimization problem which is simply solved. In addition, in case where a budget limitation does not allow to purchase the required number of monitors and the optimization problem does not converge an alternative approach is proposed for allocating very limited number of monitors in a hierarchical manner to ensure monitoring of the most severe conditions. The proposed approach is applied on the IEEE 30-bus system and an Iranian real industrial network. © 2017 Elsevier Inc. All rights reserved.

An improved harmonic resonance mode analysis method for distribution power grid

Harmonic resonance endangers seriously safe and reliable operation of power grid and an appropriate resonance harmonic analysis method is of great importance. The traditional mode analysis method is a kind of main method to analyze harmonic resonance of power grid so to obtain various harmonic information such as resonance frequency, maximum excitation node and observation node as well as participation factor. However, its calculation efficiency is lower and has no way to judge accurately the maximum excitation node in the harmonic resonance of the distribution power grid. The improved mode analysis method proposed in this paper combines the frequency spectrum analysis with the traditional mode analysis method, and the condition of whether the harmonic resonance could occur at the determined excitation node at resonance frequency is added. Taking the distribution power grid in Bonan Oil area of Shengli Oilfield as an example, this paper analyzes the harmonic resonance of distribution network by using traditional mode analysis method and improved mode analysis method respectively. By comparing the analysis results of the two methods, the superiority of the improved mode analysis method is verified. The analysis of harmonic resonance of distribution network in Bonan Oil area shows that the improved mode analysis method proposed in this paper can accurately determine the harmonic resonance frequency and the highest excitation node of distribution network, while the traditional mode analysis method could not accurately judge the highest excitation node. In addition, the calculation time of the improved mode analysis method is only 17% of that of the traditional mode analysis method, which greatly improves the analysis efficiency.

Harmonic Resonance Identification and Mitigation in Power System Using Modal Analysis

Due to a rising share of power electronic devices in power networks and the consequent rise in harmonic distortion, impedance resonances are an important issue. Nowadays, the frequency scan method is used for resonance phenomena identification and analysis. The main disadvantage of the method is its inability to decouple different resonance phenomena. This means that the method is also unable to provide sufficient information about the effects that the parameters of network elements have on different resonance phenomena. Furthermore, it was also noted that despite the fact that the harmonic resonance mode analysis is well described in the literature, there is a lack of systematic approach to the analysis procedure. Thus the main objective of this paper is to address this disadvantage and to propose a systematic approach to harmonic resonance analysis and mitigation, utilizing modal analysis. In the first part of the paper, dominant network nodes in terms of resonance amplification of harmonics are determined. This is done by analysis of the eigenvalues of the network admittance matrix. Using the eigenvalue analysis results, key parameters of network elements involved in a specific resonance are determined next. This is performed by calculating the critical mode (i.e., the mode that experiences resonance) sensitivity coefficients with respect to network parameters. In the second part of the paper, the procedure for modal resonance frequency shift is presented. The shift is performed by changing the value of a selected parameter so that the modal resonance frequency matches the desired resonance frequency value. The parameter value is calculated with the Newton–Rhapson method. Presented analysis considers both parallel and series resonances. The effectiveness of the proposed method is demonstrated on an actual industrial-network model.

Optimal Positioning of Power Quality Meters for Monitoring Potential Conditions of Harmonic Resonances in a MV Distribution System

This research proposes an optimized allocation methodology of power quality (PQ) meters in medium voltage (MV) distribution system (DS), considering the potential harmonic resonance conditions. The allocation methodology uses the harmonic resonance mode analysis (HRMA) to calculate the critical modal impedances and identify the harmonic resonance frequencies. Thereby, using the HRMA, it is possible to build a binary observability matrix, which contains the information of nodes' observability for potential harmonic resonance frequencies. The allocation problem is modeled as a constraint integer linear programming that minimizes the number of necessary PQ meters, ensuring the complete observation of the determined harmonic resonance frequencies. The final feasible solution indicates the best locations to install the PQ meters, considering the harmonic resonance conditions, which include distinct operation scenarios of the DS, regarding the capacitor banks of the customers for power-factor correction. The allocation algorithm was applied in two test DSs, based on a CIGRÉ MV network and on the IEEE 34-node test feeder. The results show that four PQ meters are required to completely monitor the potential harmonic resonance frequencies in both the test DSs. It is also shown that the final allocation solution is applicable even for certain variability of the considered capacitor banks.

Probabilistic Harmonic Resonance Assessment Considering Power System Uncertainties

The presence of power system uncertainties results in variations of the harmonic resonance behaviors. There is, therefore, a need to perform the probabilistic assessment in harmonic resonance study. In this paper, a systematic methodology for probabilistic harmonic resonance assessment considering power system uncertainties is presented. First, potential system uncertainties are analyzed and modeled. The stochastic behavior of harmonic resonance due to system uncertainties is then studied using both Monte Carlo approach and harmonic resonance mode analysis technique. A modified power iteration method is further used to efficiently reduce the calculation time. Three indices, including probabilistic expressions of 1) resonance frequency band, 2) modal impedances in the resonance band, and 3) sensitivity information at the bus-level and the element-level are used to represent the stochastic behaviors of harmonic resonance. In addition, the resonance mitigation scheme based on probabilistic resonance frequency band shift technique is described. The effectiveness of the proposed method is demonstrated through case studies in an uncertain power system. Its potential applications are also discussed.

Modal Frequency Sensitivity for Power System Harmonic Resonance Analysis

Resonance-mode analysis is effective to determine the contributions of different network components to a resonance in power system harmonic studies. There are two forms of modal sensitivity in harmonic resonance mode analysis, that is, the modal impedance sensitivity and the modal frequency sensitivity. This paper presents a method to compute the modal frequency sensitivity index. The analysis results are compared with those obtained by using the modal impedance sensitivity index to clarify the differences and similarities between the two sensitivity indices. The comparison shows that these indices complement each other and should be used to jointly diagnose power system harmonic resonance problems.

Harmonic Resonance Mode Analysis Using Real Symmetrical Nodal Matrices

Harmonic resonance mode analysis (RMA) is an effective tool for power system harmonic study. It can determine not only the harmonic resonance potentials, but also the contributions of various network components to a resonance situation. RMA is based on the eigen-decomposition of complex symmetrical nodal matrices, which is known to be difficult and inefficient compared with the decoupling of real symmetrical matrices. The complex eigenvalues also makes the consequent sensitivity analysis complicated. In this paper, an alternative modal formulation utilizing real symmetrical nodal matrices is proposed. The validity of this new formulation is confirmed through theoretical analysis and case studies.

Application of Modal Sensitivity for Power System Harmonic Resonance Analysis

Harmonic resonance is closely related to the singularity of a network admittance matrix. The smallest eigenvalue of the matrix defines the mode of harmonic resonance. This paper applies this eigenvalue theory and proposes a method to determine which network components have significant contributions to a harmonic resonance phenomenon. The basic idea is to calculate the sensitivities of a resonance mode to the parameters of network components. The sensitivity results are then ranked to quantify the impact of each component. In this paper, the eigen-sensitivity theory as applied to harmonic resonance mode analysis is presented. Case studies are used to verify the theory. A practical example is given to illustrate the application of the proposed method. In addition, this paper further conducts extensive comparative analysis on three types of network-oriented modal analysis techniques. The results have clarified the similarities and differences among the techniques