On the use of ultracapacitor to support microgrid photovoltaic power system

Why Do Electricity Policy and Competitive Markets Fail to Use Advanced PV Systems to Improve Distribution Power Quality?

“…While the existing conventional capacitors and inductors used in inverters consequently attenuate some of the shortterm system variability of PV ramping, the introduction of supercapacitor banks now gives an additional technical ability to maintain stable voltages and currents along a distribution feeder by either being switched off or absorbing electricity during high PV output intervals, complementing the ability for PV inverters to absorb or produce reactive and active power to maintain network stability. These new options enable the expansion of microgrid which cluster loads and generators to operate as a single controllable islanded system or within a main grid [33]. At present microgrids are often overloaded causing localised blackouts, and both power and energy demand limiting are generally required [43].…”

“…Mitigating large and rapid PV ramp rates is unsuitable for conventional batteries due to high cycling and high efficiency requirements [22]. More modern energy and power capacity technologies give the ability for high penetration PV systems to provide power balancing and an ability to ride through transients to reliably power a distribution network, microgrid, or a stand-alone power system and avoid dumping any of the valuable PV generation output [33]. In contrast to conventional batteries, an example is the addition of supercapacitors to provide the needed large amplitude and frequency variations that batteries or other mitigation technologies are unable to effectively provide by themselves; supercapacitors can be utilised as a power source for both rapid cycling and rapid storage [9,35].…”

“…Rapid fluctuations in PV shading patterns make MPP tracking difficult with each system string MPP value dependent on upstream PV module characteristics. In cases of shaded PV systems with bypass diodes, the power-voltage curve contains multiple local maxima which perturb and observe (P&O) MPPT algorithms have difficulty handling [20,33].…”

“…However, the large "power" (in terms of kW) supply required to deliver a relatively small amount of energy (in terms of kWh) is a challenge for conventional energy storage technologies. Traditional electrochemical battery systems are expensive and extremely limited by their depth of discharge and expire after a relatively low numbers of charge/discharge cycles [33,34]. Mitigating large and rapid PV ramp rates is unsuitable for conventional batteries due to high cycling and high efficiency requirements [22].…”

Ultracapacitor-based distributed energy resources to support time-varying smart-grid power flows

“…In a previous paper [6], the authors discussed on a storage-integrated PV microsource, which was constituted by equipping a PV system (PV source and electronic power converters) with an ultracapacitor device. The aim of the work was to test the hybrid system behaviour under several load requirements.…”