A new AHP – based reactive power valuation method

In Malaysia, the electricity tariff is based on the active energy consumed and does not include any reactive (energy) power required. In order to recover the extra cost incurred in supplying the reactive power required by the consumers, the utility imposes a surcharge on a consumers whose power factor averaged over a month is below the value of 0.85pf. However, the surcharge is imposed on medium to large commercial and industrial consumers only. This paper proposes a new method for valuation of Reactive Power in power system. This method uses two important factors to determine the most important Reactive Power source power system. These two factors are: Voltage Sensitivities and Voltage Adequacy and Stability (PV Curve). In this paper AHP method has been used to classify the Reactive power sources according to their importance in power system. The effectiveness of the proposed method is verified under IEEE 9-bus system

Can Distribution Grids Significantly Contribute to Transmission Grids' Voltage Management?

Power generation in Germany is currently transitioning from a system based on large, central, thermal power plants to one that heavily relies on small, decentral, mostly renewable power generators. This development poses the question how transmission grids' reactive power demand for voltage management, covered by central power plants today, can be supplied in the future. In this work, we estimate the future technical potential of such an approach for the whole of Germany. For a 100% renewable electricity scenario we set the possible reactive power supply in comparison with the reactive power requirements that are needed to realize the simulated future transmission grid power flows. Since an exact calculation of distribution grids' reactive power potential is difficult due to the unavailability of detailed grid models on such scale, we optimistically estimate the potential by assuming a scaled, averaged distribution grid model connected to each of the transmission grid nodes. We find that for all except a few transmission grid nodes, the required reactive power can be fully supplied from the modeled distribution grids. This implies that - even if our estimate is overly optimistic - distributed reactive power provisioning will be a technical solution for many future reactive power challenges

Reactive power minimization of dual active bridge DC/DC converter with triple phase shift control using neural network

Reactive power flow increases dual active bridge (DAB) converter RMS current leading to an increase in conduction losses especially in high power applications. This paper proposes a new optimized triple phase shift (TPS) switching algorithm that minimizes the total reactive power of the converter. The algorithm iteratively searches for TPS control variables that satisfy the desired active power flow while selecting the operating mode with minimum reactive power consumption. This is valid for the whole range of converter operation. The iterative algorithm is run offline for the entire active power range (-1pu to 1pu) and the resulting data is used to train an open loop artificial neural network controller to reduce computational time and memory allocation necessary to store the data generated. To validate the accuracy of the proposed controller, a 500-MW 300kV/100kV DAB model is simulated in Matlab/Simulink, as a potential application for DAB in DC grids

Reactive Power Control in Power System using Modified UPFC

The power system is a exceptionally nonlinear system that works in an always showing signs of change condition, loads, generator yields, topology and key working parameters changes consistently. The stability of the system depends on the nature of the disturbance as well as the initial operating condition. The power congestion known as the limitations to how much power can be transferred across a transmission interfaces and further that there is an incentive to actually desire to transfer more power. The old approach was to correct congestion lies in reinforcing the system with additional transmission capacity. Although easy to perform, this approach is complex, time consuming and costly. It is ending up noticeably progressively hard to get the licenses to building new transmission passages, or even grow existing ones. This issue can be solved by introducing Facts devices in the transmission system. Facts Devices play an imperative part in controlling the reactive and active power flow to the power network and thus both the system voltage variances and transient stability. Among Facts device Unified Power Flow Controller (UPFC) is the most versatile and complex power electronic equipment which can increase reliability and can serve as an alternative to new investments in overhead lines, which are difficult due to a lack of public support. The proposed work is based on control of reactive power in power system utilizing modified Unified Power Flow Controller (UPFC). The impact of customary UPFC and modified UPFC on the power flow of transmission lines were analyzed

PI-based controller for low-power distributed inverters to maximise reactive current injection while avoiding over voltage during voltage sags

This paper is a postprint of a paper submitted to and accepted for publication in IET Power Electronics and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at the IET Digital Library.In the recently deregulated power system scenario, the growing number of distributed generation sources should be considered as an opportunity to improve stability and power quality along the grid. To make progress in this direction, this work proposes a reactive current injection control scheme for distributed inverters under voltage sags. During the sag, the inverter injects, at least, the minimum amount of reactive current required by the grid code. The flexible reactive power injection ensures that one phase current is maintained at its maximum rated value, providing maximum support to the most faulted phase voltage. In addition, active power curtailment occurs only to satisfy the grid code reactive current requirements. As well as, a voltage control loop is implemented to avoid overvoltage in non-faulty phases, which otherwise would probably occur due to the injection of reactive current into an inductive grid. The controller is proposed for low-power rating distributed inverters where conventional voltage support provided by large power plants is not available. The implementation of the controller provides a low computational burden because conventional PI-based control loops may apply. Selected experimental results are reported in order to validate the effectiveness of the proposed control scheme.Peer ReviewedPostprint (updated version

Remote power control strategy based on virtual flux approach for the grid tied power converters

The control of active and reactive power for the Renewable Energy Sources (RES) based power plants are very important. The injection of active and reactive power to the grid is normally controlled at the Point of Common Connection (PCC) where this point is typically far away from the power converter station. This paper proposed a controlling principle which is based on virtual flux approach that permits to control remotely the power injected at the PCC. The results will show that the Virtual Flux (VF) estimation is capable to estimate the grid voltage in any point of the network as well as the capability of the control principle to inject the specific amount of active and reactive power at a point that can be some kilometers away. In this paper, the basic principle for the remote power control is presented and the effectiveness of the proposed system has been validated by experimental studies.Postprint (published version