Distribution Voltage Profile Research Articles

Development of utility assisting controllers for solarised irrigation system

Several initiatives were taken by the Government of India (GoI) to increase the solar energy generation and had set a target of installing 100 GW grid-connected, solar power projects by 2020. Due to the unreliability of the solarised system and limitations of energy storage systems, grid-connected PhotoVoltaic (PV) has its own advantage over the stand alone systems. Analysis of distribution voltage profile indicates its dependence on the loading of the house and can be slightly different for different utility companies. An attempt is made to develop the irrigation pump controller which will perform the switching while considering the PV generation availability, utility voltage conditions, water availability and other field conditions for irrigating paddy crop in clay loam soil. The low cost, microcontroller-less switching module being developed can perform the pump switching according to PV and water availability, utility voltage and soil moisture condition. In contrast, the microcontroller based system is more flexible and can operate the pump switching according to several sensing quantities like PV generation, trend of the utility voltage over a finite time, crop ripening input, water availability in the reservoir, soil moisture level and temperature and humidity condition in the field. This will ensure the automatic protection of the pump against under-voltage, overvoltage, frequent voltage fluctuations and dry running while assisting the utility grid throughout the day and thereby providing the basic requirements of demand response. Although the microcontroller-less switching system will be simpler and cheaper, the microcontroller based system will have greater versatility and reliability.

Dissipativity of nonlinear ODE model of distribution voltage profile

In this paper, we consider a power distribution system consisting of a straight feeder line. A nonlinear ordinary differential equation (ODE) model is used to describe the voltage distribution profile over the feeder line. At first, we show the dissipativity of the subsystems corresponding to active and reactive powers. We also show that the dissipation rates of these subsystems coincide with the distribution loss given by a square of current amplitudes. Moreover, the entire distribution system is decomposed into two subsystems corresponding to voltage amplitude and phase. As a main result, we prove the dissipativity of these subsystems based on the decomposition. As a physical interpretation of these results, we clarify that the phenomena related to the gradients of the voltage amplitude and phase are induced in a typical power distribution system from the dissipation equalities. Finally, we discuss a reduction of distribution losses based on the dissipation rate of the subsystem of voltage amplitude.

Asymptotic assessment of distribution voltage profile using a nonlinear ODE model

The promising increase of Electric Vehicles (EVs) in our society poses a challenging problem on the impact assessment of their charging/discharging to power distribution grids. This paper addresses the assessment problem in a framework of nonlinear differential equations. Specifically, we address the nonlinear ODE (Ordinary Differential Equation) model for representing the spatial profile of voltage phasor along a distribution feeder, which has been recently introduced in literature. The assessment problem is then formulated as a two-point boundary value problem of the nonlinear ODE model. In this paper we derive an asymptotic charcterisation of solutions of the problem through the standard regular perturbation method. This provides a mathematically-rigor and quantitative method for assessing how the charging/discharging of EVs affects the spatial profile of distribution voltage. Effectiveness of the asymptotic charcterisation is established with simulations of both simple and practical configurations of the power distribution grid.

Distribution Voltage Regulation Through Active Power Curtailment With PV Inverters and Solar Generation Forecasts

Distribution voltage profiles are subjected to overvoltage limit violations from high penetration of grid-connected photovoltaic (PV) systems. Such voltage rises seen at the point of PV interconnection can be mitigated by adaptively changing the active and/or reactive power injection from the PV inverter. This work proposes a local voltage regulation technique that utilizes very short-term (15 s) PV power forecasts to circumvent imminent upper voltage limit violation or an overvoltage scenario. To provide these PV generation forecasts, a hybrid forecasting method is formulated based on Kalman filter theory, which applies physical PV generation modeling using high-resolution (15 s) data from on-site measurements. The proposed algorithm employs an active power curtailment based on these PV power forecasts, when the reactive power estimate given by a droop-based method cannot provide the desired voltage regulation within predefined power factor limits. The curtailment threshold values are calculated in such a way that this voltage regulation technique can reduce possible voltage limit violations. The effectiveness of the proposed method is demonstrated with case studies developed on a standard test feeder with realistic load and PV generation profiles.

A new approach for real time voltage control using demand response in an automated distribution system

The main goal of Distribution Automation (DA) is the real-time operation, usually without operator intervention, of distribution systems as a consequence of load demand or power generation variations and failure conditions in the distribution systems. As real time voltage control is known as a legacy system that can be fully activated by DA equipments, in this paper an analytical study is reported to demonstrate the effects of load curtailments on voltages profile in distribution network. A new method for real time voltage control, based on emergency demand response program, is also proposed. The proposed method uses the real-time measured data collected by RTUs and determines the tap changer condition and load curtailment required in order to maintain the distribution voltage profile. Emergency conditions include outages of generators and lines, and fluctuations due to unpredictable load demand and renewable generation. A novel voltage sensitivity matrix, based on performed voltage sensitivity analysis due to load participation in demand response program, is also proposed. In order to verify the effectiveness and robustness of the proposed control scheme, it is tested on a typical automated distribution network. Simulation results show that the proper selection of load curtailment can improve voltage profile and that, in emergency conditions, demand response is an effective way to keep the voltage in a permissible range.