The nonlinear portion of electrical loads has increased significantly in recent years. Harmonic currents injected by these loads into the distribution system should be considered when solving the capacitor placement problem in order to assure that the optimal solution does not result in excessive harmonic distortion. A voltage-dependent current injection load model is presented to determine voltage waveform characteristics and additional losses at harmonic frequencies. Computer simulations show that the optimal capacitor sizes and locations depend heavily on the load model used at fundamental frequency and on harmonic signals, especially when limits are imposed on voltage waveforms. >

Effects of nonlinear loads on optimal capacitor placement in radial feeders

Increasing use of power electronic loads on distribution feeders together with greater use of power factor correction capacitors on the distribution system can result in poor operating conditions in the form of high harmonic levels propagating through a distribution system. HARMFLO (Harmonic Power Flow Study Program) was developed by EPRI (Electric Power Research Institute) for use in the analysis of harmonics on a power system. However, for a typical analysis of a distribution system, data for some of the parameters required by HARMFLO are not available. Furthermore, exact load information is usually not available. Harmonic levels determined from field tests on a distribution system are compared to results of HARMFLO simulations to determine if this analysis tool can provide useful results despite the lack of exact information for load modeling and other system parameters. >

Harmonic propagation on an electric distribution system: field measurements compared with computer simulation

An alternate method of determining the harmonic currents of a six pulse AC-DC converter is described. This method uses the harmonic voltages to predict the firing angles and the resulting injected harmonic currents. The model avoids the complexities of power flow solutions methods and offers more accuracy than the usual current injection techniques. Also, the model is able to operate under balanced or imbalanced conditions. Its accuracy is shown with time domain solutions.

Modified current injection technique

In this paper a non-divergent harmonic load-flow calculation method is developed. The proposed method, which is called h-Newton, is a modification of the Newton method and its aim is based on differential equations theory. A parameter h is included in the Newton algorithm, and is calculated to ensure the convergence of the method to the correct solution. The execution time of the new method is comparable to the Newton method when this is convergent. Several examples are studied to analyse the proposed method and a mathematical justification about the convergence of the h-Newton method is developed.

Non-divergent numerical method for the harmonic load-flow resolution

A New Digital Relay for Dispersed Storage and generation (DSG) Units

While the appearance of nonlinear devices as loads in electric power systems is not a new phenomenon, this sector of the total demand is significantly increasing and has reached substantial levels in many areas. Experience has shown that the configuration of the power system to which these devices are attached can be such as to cause a resonance condition to develop [1], [2]. This paper proposes a method to readily evaluate a system configuration so that an evaluation of possible problems due to harmonic voltage resonance can be made. This method will produce results with enough accuracy to reduce the need to run multiple modified Newton-Raphson power flow studies [3], [4].

L. A. Kraft

Papers

A Method to Analyze Voltage Resonance in Power Systems