CONTROL STRATEGIES FOR ELECTRIC VEHICLE CHARGING INFRASTRUCTURE

Abstract

The Electric Vehicles (EVs)/ plug-in hybrid EVs (PHEVs) are slowly and steadily making inroads, in public as well as personal vehicle markets worldwide. The limited fuel reserves and pollution caused due to conventional internal combustion engine (ICE) driven vehicles are the main driving elements for allowing a paradigm shift towards EVs. However, with the rapidly increasing demand of EVs, many experts had a manifest concern regarding the charging infrastructure and thus, several studies have been presented over it. With the growing popularity of EVs, power distribution networks are under stress to accommodate the charging infrastructure. The large-scale penetration of EV charging loads in low voltage network may lead to severe voltage fluctuations, overloading of distribution transformer and harmonics related power quality issues. To subsides the negative effect of EVs on distribution system, smart charging technique must be required. During one of the two operating mode, EV charger transfers active power to grid as well as compensating reactive power and known as Vehicle to grid (V2G) mode. This mode requires a bidirectional EV charger which may operate in all over the active-reactive (P-Q) power plane. Moreover, single phase single stage EV chargers have inherent problem of producing second order ripple component on DC side. This problem is further exaggerated during vehicle-to-grid (V2G) mode of operation where it may be normally controlled to supply both active as well as reactive power. During the V2G reactive power compensation, the second order harmonics ripple component at DC side will increase which further reduces the life cycle and performance of battery pack. Therefore, the second order ripple component must be minimized for improving the life of battery pack. Therefore, the main aim of proposed study is to develop a robust control system for EV charger to operate it in wide range of G2V and V2G mode of operations while maintain the amount of ripple content on DC side within the permissible limit. The EV charger may supply active power to grid if required and compensate reactive power (inductive or capacitive) if a battery charges at slower rate. In that case, the remaining rating of charger is utilized for compensating the reactive power for optimally utilization

charger can work as an active power filter and improves the power quality.

viii

In this regard, total four control techniques based on proportional integral (PI), proportional resonant (PR), plant integrated proportional integrated (PIPI), repetitive controller (RC), and adaptive neuro-fuzzy inference system (ANFIS) have been presented in this thesis for two stage EV charger. The two control techniques have been presented for both ON board and OFF board EV charger. These EV chargers having two conversion stages i.e., AC-DC and DC-DC converter. Both the converters have their separate controller. Moreover, for single phase single stage ON board EV charger, a control technique has been proposed for minimization of second order ripple presented on DC side. For this, single phase AC-DC converter is utilized for charging purpose. Further, all the EV chargers are able to compensate the reactive power of local load. They all have active and reactive power input references where active command depends on customer desire charging rate and reactive command is requested by grid. All EV charger prototype is controlled by using dSPACE 1104 in laboratory.