Voltage rise mitigation for solar PV integration at LV grids Studies from PVNET.dk

Solar energy from photovoltaic(PV)is among the fastest developing renewable energy systems worldwide.Driven by governmental subsidies and technological development,Europe has seen a fast expansion of solar PV in the last few years.Among the installed PV plants,most of them are situated at the distribution systems and bring various operational challenges such as power quality and power flow management.The paper discusses the modelling requirements for PV system integration studies,as well as the possible techniques for voltage rise mitigation at low voltage(LV)grids for increasing PV penetration.Potential solutions are listed and preliminary results are presented.

Effect of pulse voltage rising time on discharge characteristics of a helium-air plasma at atmospheric pressure

In this paper,the influence of voltage rising time on a pulsed-dc helium-air plasma at atmospheric pressure is numerically simulated.Simulation results show that as the voltage rising time increases from 10 ns to 30 ns,there is a decrease in the discharge current,namely 0.052 A when the voltage rising time is 10 ns and 0.038 A when the voltage rising time is 30 ns.Additionally,a shorter voltage rising time results in a faster breakdown,a more rapidly rising current waveform,and a higher breakdown voltage.Furthermore,the basic parameters of the streamer discharge also increase with voltage rise rate,which is ascribed to the fact that more energetic electrons are produced in a shorter voltage rising time.Therefore,a pulsed-dc voltage with a short rising time is desirable for efficient production of nonequilibrium atmospheric pressure plasma discharge.

Enhancement of Large Renewable Distributed Generation Penetration Levels at the Point of Common Coupling

The occurrence of distortion and over voltage at the Point of Common Coupling(PCC)of Renewable Distributed Generation(RDG)limits its penetration levels to the power system and the RDG integration is expected to play a crucial role in power system transformation.For its penetrations to be sustained without disconnection from the system,there must be a solution to the voltage rise,distortion,unbalanced current and grid reactive power control strategy at PCC.It is an IEEE-1547 requirement that RDG integration to the power system should be regulated at PCC to avoid disconnection from the network due to power quality criteria.RDG integration must meet up with this specification to uphold power quality and avoid damage to the sensitive equipment connected at PCC.In this paper,voltage rise,unbalanced current,reactive power and distortion are being managed at PCC while Distribution Network(DN)accepts more RDG penetration levels without violation of the IEEE and South Africa grid code act.Active Power Filter and Full Bridge Multi-Level Converter(FBMC)are considered to safeguard power quality to the grid,they are modelled in MATLAB/SIMULINK and the results obtained shown that the proposed strategy can successfully regulate voltage rise,distortion,unbalanced current and continuously improve power quality with RDG integration at PCC.The proposed method’s key innovation is the strategic generation and absorption of reactive power to curtain an overvoltage,reverse power flow,and distortion at the PCC,allowing more RDG penetration levels to the grid without disconnection while maintaining the standard requirement for power quality at the PCC.The simulation outcomes validate the superiority of the FBMC over the active power filter with respect of reactive power generation/absorption,dynamic response,and damping capability.

Online voltage estimation and control for smart distribution networks

The increasing deployment of Distributed Generation(DG) technologies introduces power quality challenges to the grid, in particular steady state voltage rise at the connection point for DG units. In most distribution networks,control and monitoring of grid parameters is missing, as well as system security is at risk. Smart grid technologies have the capability to realize the real-time measurements and on-load voltage controls. With the steady implementation of smart grid technologies throughout the existing distribution networks, the online voltage control can be achieved ensuring the power quality and voltage levels within the statutory limits. This study presents a methodology for the estimation of voltage profile in a smart distribution network with DG for the online voltage control, taking into account different line X/R ratios and laterals. This method is based on maximum and minimum voltage estimation by remote terminal units(RTUs) placed only at DG connected bus and at capacitor connected bus. Voltage regulation is carried out based on RTUs estimated values. This work is tested on two radial distribution networks with/without DGs and laterals. Comparative results for voltage magnitudes estimated with different methodology are presented. The reported simulation results show that the method presented is capable of estimating the voltage profile along the distribution network with DGs for the online voltage control, considering different line X/R ratios and laterals.