Javier Roldan-Perez

Modeling and Sensitivity Study of Consensus Algorithm-Based Distributed Hierarchical Control for DC Microgrids

Distributed control methods based on consensus algorithms have become popular in recent years for microgrid (MG) systems. These kind of algorithms can be applied to share information in order to coordinate multiple distributed generators within a MG. However, stability analysis becomes a challenging issue when these kinds of algorithms are used, since the dynamics of the electrical and the communication systems interact with each other. Moreover, the transmission rate and topology of the communication network also affect the system dynamics. Due to discrete nature of the information exchange in the communication network, continuous-time methods can be inaccurate for this kind of dynamic study. Therefore, this paper aims at modeling a complete dc MG using a discrete-time approach in order to perform a sensitivity analysis taking into account the effects of the consensus algorithm. To this end, a generalized modeling method is proposed and the influence of key control parameters, the communication topology, and the communication speed are studied in detail. The theoretical results obtained with the proposed model are verified by comparing them with the results obtained with a detailed switching simulator developed in Simulink/Plecs.

Space-Vector-Based Controller for Current-Harmonic Suppression with a Shunt Active Power Filter

Abstract Active power filters are often proposed as flexible solutions to tackle power quality problems in electric distribution systems. It is well known that the need for tracking harmonic currents and voltages with these electronic devices exceeds the capabilities of conventional Proportional+Integral controllers and more sophisticated algorithms are sought. This paper presents a control method based on multiple reference frames for tracking or rejecting periodic signals in this context. The proposed scheme allows recursive calculation when referring signals to reference frames rotating synchronously with harmonic equivalent space vectors whilst only a very small number of trigonometric-function evaluations are required. Furthermore, using the proposed approach, the control of each harmonic can be dealt with using the same simple Integral controller. Experimental results of a shunt active power filter are provided to validate the main contributions of the paper, including an scenario with grid-frequency variation to evaluate the adaptation capability of the proposed controller.

On the Power Flow Limits and Control in Series-Connected Custom Power Devices

Power electronic devices connected in series with electrical distribution lines have been proposed for some time to protect sensitive loads from voltage sags, voltage harmonics, and unbalances. Full understanding of active- and reactive-power consumption in the device is important in order to minimize losses and to provide reactive-power compensation while leaving the load undisturbed. However, a comprehensive description of power flow in series custom power devices has not been presented yet. This paper proposes a control framework where active and reactive power consumed by series devices can be analyzed and controlled. The method proposed is based on a reference frame synchronized with the load current, which greatly simplifies the power calculations and makes it possible to take into account the load-voltage constraints to guaranty safe operation of the load. The proposed method has been tested on a 5-kVA prototype of a series active conditioner.

Space-vector-based controller for current-harmonic suppression with a shunt active power filter

Active power filters are often proposed as flexible solutions to tackle power quality problems in electric distribution systems. The need for tracking harmonic currents and voltages with these electronic devices exceeds the capabilities of conventional Proportional+Integral controllers and more sophisticated algorithms are sought. This paper presents a control method based on multiple reference frames for tracking or rejecting periodic signals in this context. The proposed scheme allows recursive calculation when referring signals to reference frames rotating synchronously with harmonic equivalent space vectors whilst only a very small number of trigonometric-function evaluations are required. Furthermore, using the proposed approach, the control of each harmonic can be dealt with using the same simple Integral controller. Detailed simulation of a shunt active power filter is provided to validate the main contributions of the paper, including an scenario with grid-frequency variation to evaluate the adaptation capability of the proposed controller.

Versatile Control of STATCOMs Using Multiple Reference Frames

This chapter first reviews the fundamentals of active and reactive power control using STATCOMs. Then, two current control algorithms, namely selective/resonant controllers and repetitive controllers, are presented that provide a STATCOM with the capability of controlling the harmonics of the current injected into the PCC. Finally, the use of synchronously-rotating reference frames is generalized so that current harmonic control can also be achieved using PI controllers. An efficient application of the last technique is explained in detailed and a number of experimental results are presented. It will be demonstrated that versatile control of STATCOMs is straightforward using this technique even if the grid frequency varies. This technique can be applicable to both, traditional, strong and centralised electric power systems and those to come in the future with large amounts of distributed generation.