Node Voltage Method Research Articles

AUTOMATIC ADJUSTMENT OF REACTIVE POWER BY FACTS DEVICES UNDER CONDITIONS OF VOLTAGE INSTABILITY IN THE ELECTRIC NETWORK

This article describes the problem of automatic regulation of reactive power using electronic devices FACTS (Flexible AC Transmission Systems): static synchronous compensator (STATCOM) and unified power flow controller (UPFC). With the help of a complex writing form, the following are determined: voltages at the installation nodes of the FACTS device and loads, currents of loads, power sources and electronic compensators in case of voltage instability at the load node of the electrical network. Voltages and currents are determined using the node-voltage method. The task of STATCOM is partial or full compensation of reactive power. During the reduction of the voltage at the load node, the reactive power generated by the power source decreases. The STATCOM should partially or fully compensate for the reactive power imbalance as quickly as possible. However, at the same time, it is not possible to fully compensate for the voltage reduction. A series-parallel or parallel-series UPFC can be used to solve this problem. As a result of using the UPFC, it is possible to automatically raise the voltage level to acceptable values with the help of the UPFC series compensator. The analysis shows that the parallel-serial UPFC is characterized by the stability of operation. In the case of using a series-parallel UPFC, there are restrictions on the ability to adjust the imaginary voltage component of the series compensator, since the angle of the voltage vector changes, which causes a failure in the operation of the regulator of the parallel compensator UPFC.

Assessing the Effects of Smart Parking Infrastructure on the Electrical Power System

The forthcoming surge in electric vehicle (EV) adoption demands the comprehensive advancement of associated charging infrastructure. In this study, an exploration of EV charging’s impact on the power distribution system is conducted via the simulation of a parking lot equipped with six distinct types of EVs, each showcasing unique charging curves, charging power, and battery capacities. A charging profile is synthesized and compared with laboratory-obtained data to ascertain the implications on the grid. To further understand the effects of smart parking on the power distribution system, a mathematical algorithm was created and applied to a segment of an urban electrical grid that includes 70 private residences. Basic electrical parameters were computed using the node voltage method. Four scenarios were simulated: (1) the existing distribution system, (2) the current system plus smart parking, (3) the current system plus 50% of houses equipped with 3.5 kW photovoltaic installations, and (4) the current system plus photovoltaics and smart parking. This paper examines the core distribution system parameters, namely voltage and current, across these four scenarios, and the simulation results are extensively detailed herein.

An efficient multidisciplinary design research for the integrated low speed permanent magnet motor system based on analytical and numerical hybrid analysis

This paper proposed an efficient high-accuracy multidisciplinary design process for the integrated system of low speed permanent magnet synchronous motor (PMSM). The method combined the analytical models and numerical models together to get an efficient way to design the integrated motor. In the proposed method, a magnetic equivalent circuit (MEC) model of the motor is established first based on one modular structure of the motor, and the finite element analysis (FEA) numerical model is used to correct the results of the analytical model next. Then the iron loss, copper loss, and switching loss from the results of the electromagnetic model are loaded to a proposed simplified lumped parameter fluid-thermal model. This fluid-thermal coupled analytical model cuts the fluid flow into several parts depends on the parameters of the cooling path, each parts act as a current controlled voltage source coupled with these parameters. And because this coupled model has controlled sources, the conventional node voltage method is not suitable anymore, so a more universal list parameter calculation method is proposed for this coupled model. Finally, the computational fluid dynamics (CFD) model is used to correct the results of the analytical model as well. The aim of the above analytical models is to quickly get the suitable multidisciplinary pre-design or design trends, and this pre-work or trends will reduce the design process time of the high-accuracy numerical models.

Efficient DC and AC Impedance Calculation for Arbitrary-Shape and Multilayer PDN Using Boundary Integration

This article presents an efficient methodology based on boundary integration to calculate the dc and ac impedance of power distribution networks (PDNs) for arbitrary-shape and multilayer printed circuit boards (PCBs). The proposed method adopts a boundary element method to extract inductances for the arbitrary parallel-plane shapes. Subsequently, the equivalent circuit formed by the via inductances and plane capacitances is solved using the node voltage method. By merging the parallel and serial inductances and simplifying the equivalent circuit, the computation time can be significantly reduced for a large number of vias and layers. This matrix manipulation strategy can be applied to various PCB structures without human intervention or commercial circuit solvers. Moreover, a contour integral method is employed to calculate the dc resistances for arbitrary shape and multilayer PDNs. Therefore, the wideband PDN impedance from dc to ac frequencies can be efficiently calculated through 1-D boundary integration, which can be performed more quickly than full-wave simulations. The proposed method can aid in the development of electronic design automation tools for PDN design.

U=RIsolve: A Web-Based Application for Learning Electrical Circuit Analysis [Education

Learning circuit analysis is often a challenging issue for Electrical Engineering undergraduate students. During the course's early stages, procedures such as the correct identification of Branches, Nodes and Loops, the expression of Kirchhoff Current and Voltage Laws, as well as the application of analysis/simplification Theorems and Algorithms, usually embed tricky and error-prone steps for beginners. While circuit simulators offer a validation for theoretical and experimental analysis, they do not explain how to obtain the results nor the fundamental laws supporting them. In this regard, a new web-based framework, - dubbed U=RIsolve (read as you resolve) - for teaching and self-learning the Node Voltage Method (NVM) is presented in this paper. The U=RIsolve application goes far beyond the capabilities of traditional circuit simulators, as it outputs the fundamental circuit information, the methodology, the equations and the results related to the NVM. An outlook of the application main features, user interface and usage in electrical circuit analysis is provided, along with the future implementations.

Research on a current calculation method and characteristics of pole-to-ground faults in true bipolar MMC-HVDC grids considering line coupling✰

The pole-to-ground fault is the most common fault in the true bipolar modular multilevel converter based high voltage direct current (MMCHVDC) grid. The study of a fault current calculation method and characteristics is the theoretical basis for relay protection and fast fault isolation technology of MMCHVDC grid. Considering the mutual inductance coupling between lines, this paper proposes a general fault current calculation method for pole-to-ground faults in MMCHVDC grids. Firstly, considering the influence of AC system on MMC and the mutual inductance coupling between lines, the complex frequency domain equivalent model of the MMCHVDC grid and the simplified model of the remote converter station are studied. Based on the characteristics of the true bipolar MMCHVDC grids, the circuit is analyzed in the complex frequency domain, and an improved node voltage method combined with voltage current relation (VCR) is proposed to calculate the MMCHVDC fault current and obtain the corresponding expression. Finally, the proposed method is validated by comparing its calculation results with the simulation results performed on PSCAD/EMTDC, and the characteristics of the pole-to-ground fault in the MMCHVDC grid are further summarized.

Research on Influence of Converter Transformer Grouping and Receiving End Power Grid Structure on Converter Transformer DC bias

When ±800kV UHVDC project was put into operation, DC bias problem can not be ignored. In this paper, a calculation model for DC bias current is established based on Xiluodu-Zhexi UHVDC project data. Converter transformer grouping and receiving end power grid structure are considered. The converter transformer DC bias current is calculated by node voltage method. The influence of different converter transformer grouping modes, distance between grounding electrode and substation, and the feeder length and the number of feeder loop are analysed. The results show that, single-phase converter transformer bias current is maximum with full load and 6 converter transformers under 1/2 monopole earth mode. And bias current level of converter can be reduced in planning and designing.

<inline-formula> <tex-math notation="LaTeX">$N$ </tex-math> </inline-formula>-Way Gysel Power Divider With Arbitrary Power-Dividing Ratio

In this paper, N-way Gysel power dividers with arbitrary power-dividing ratio are studied by using node voltage and current method for the first time. Closed-form analytical equations are derived for the design of the proposed Gysel power divider with arbitrary power division on arbitrary terminated impedance. Parameters that might influence the frequency bandwidth are investigated and optimized to achieve balanced performance. For verification, 3-way and 6-way Gysel power dividers are, respectively, designed, fabricated, and measured at a center frequency of 3.45 GHz, with dividing ratio 1:1:1, 1:2:3, 1:1:1:1:1:1:1, and 1:1.2:1.2:1.5:1.5:2, respectively. Good agreements can be observed among expected, simulated, and measured results, indicating the validity of the proposed strategies.

Sensitivity analysis of method for harmonic state estimation in the power system

In this paper, a new algorithm for harmonic state estimation in power systems is represented. The algorithm is based on node voltage method, Kron reduction matrix, modeling of power system in frequency domain using phase values and optimization genetic algorithm. The algorithm uses measured voltage and current harmonics as an input data, with partially known data about transmission network. Algorithm estimates RMS and angle values of voltage harmonics in the unmonitored part of power system. Sensitivity analysis of proposed algorithm was conducted on a case study of 110kV transmission network. Admittance matrix of power system is identified by using genetic algorithm with an accuracy of 0.5%, while an error of harmonic voltage estimation is lower than 1.129%.

The use of a topological list for calculating the parameters of electric-power systems on the basis of the node-voltage method

The software implementation of the node-voltage equations for calculating the parameters of electric-power systems on the basis of the topological list is considered. Of the well-known modifications of the node-voltage method, it is proposed to use the equations for node voltages in the form of a current balance when specifying a constant-conductivity load. To eliminate the harmonic components during calculations, the equation for each element of the electric-power system is represented in the Park–Gorev axes. When forming the matrices of the nodal conductivities and specifying currents, a topological list that is based on the principle of piecemeal contributions is used. The key advantages of the method that is based on the topological list are that it is unnecessary to observe the order of numbering rows and that this method is highly algorithmic, thus providing the minimization of the computational efforts in compiling equations on a computer. The essence of the piecemeal-contribution principle lies in the successive formation of matrix coefficients, as row-by-row processing of the topological list is performed. An algorithm for the formation of equations according to the node-voltage method using the topological list in the form of a block diagram is presented. Calculation using the node-voltage method on the basis of the topological list is an independent task, as well as representing a component of more complex types of calculations, such as optimization of the normal modes, stability analysis, reliability assessment, etc. The interrelations between individual components of the process of solving the problem of calculating stationary and quasi-stationary operating modes of the electric-power system with respect to input and output information are shown. The formation of the equations of the structural elements in stationary and quasi-stationary modes of the electric-power system of a factory is based on the linearization of the initial node-voltage equations.

Analysis of DC/DC converters by mean node voltage method

Analysis of DC/DC converters by mean node voltage method

The Study on Numerical Calculation of Unequal Potential Grounding Parameters of Large Hydropower Plant

To solve the problem of grounding parameters of large hydropower, which is in a special soil environment, we deduced unequal potential calculation formula ,based on the model of unequal potential in ground grid and combined with the boundary element method and node voltage method. Through example calculations, the paper analyzes the impact of the ground grid size, soil resistivity and conductor permeability on unequal potential and proves the accuracy of the results, compared with CDEGS software. This method can be used in grounding calculation and analysis of large hydropower stations.

A Comprehensive MPPT Algorithm of the Solar Batteries Energy-Saving Control System

The comprehensive MPPT algorithm, which is combined with three approaches including the constant voltage tracking method (CVT), the perturbation and observation method (P&O), and the incremental node-voltage conductance method (INC), aims to study how to improve the solar energy utilization of the solar battery energy-saving control system of field monitoring equipment. To obtain the parameters needed for numerical simulation, solar power meter is used to measure light intensity curve within 30 seconds in spring. Then we establish the photovoltaic array simulation model and get the power tracking curve. Comparing with the curves based on the comprehensive MPPT algorithm with the mainstream MPPT algorithms, its proven that the time consumption of tracking MPP is shorter and that the efficiency of photovoltaic power generation is higher.

Power flow calculation method of large shipboard power system

The effect of line voltage drop is considered larger on loads, especially on asynchronous motor, transformers and other non-linear load parameters in power system of large ships. A novel power flow method based on improved node voltage method is proposed, and a typical ship power system, which has 2 power stations and 10 nodes, with closed-loop design but open-loop operation, is taken as an example. Simulation results show that the improved power flow calculation method has achieved higher accuracy and better convergence.

Node-Voltage Method Using ‘Virtual Current Sources’ Technique for Special Cases

A new technique based on the use of ‘virtual current sources’ makes any planar or nonplanar electric circuit solvable using the node-voltage method. The node-voltage method is systematized and it is shown how difficulties encountered until now with special circuit categories can be overcome.

Efficient simulation of the dynamic behaviour of large-scale electric power systems

A new algebro-differential equation system for the computation of dynamics and transients in electric power systems is formulated with the extended node voltage method exclusively on the basis of Kirchhoff's current law. Using the Singular Perturbation method, the systematic derivation of reduced-order power system models, which are adapted to the respective setting of tagles, is shown. The complete power system can be decomposed into a non-linear slow and a mid and a fast subsystem, which are homogeneous and usually linear and can thus also be solved analytically. Simulation examples show a good agreement with the results of the complete state equation system as well as large computing time gains.