Investigation into Photovoltaic Distributed Generation Penetration in the Low Voltage Distribution Network

Significant integration of photovoltaic distributed generation (PVDG) in the low voltage distribution network (LVDN) could potentially pose threats and challenges to the core activity of distribution system operators (DSO), which is to transport electrical energy in a reliable and cost-effective way. The main aim of this research is to investigate the active planning and operation of LVDNs with increased PVDG integration through steady state power system analysis. To address the impacts of voltage profile fluctuation due to power flow modification, this research proposes a probabilistic risk assessment of power quality (PQ) variations and events that may arise due to significant PVDG integration. A Monte Carlo based simulation is applied for the probabilistic risk assessment. This probabilistic approach is used as a tool to assess the likely impacts due to PVDG integration against the extreme-case scenarios. With increased PVDG integration, site overvoltage is a likely impact, whereas voltage unbalance reduces when compared with no or low PVDG penetration cases. This is primarily due to the phase cancellation between the phases. The other aspect of the work highlights the fact that the implementation of existing volumetric charges in conjunction with net-metering can have negative impacts on network operator’s revenue. However, consideration of capacity charges in designing the existing network tariff structure shows incentivising the network operator to perform their core duties under increased integration of PVDG. The site overvoltage issue was also studied and resolved in a novel way, where the active and reactive power of the PVDG inverters at all the PV installed premises were optimally coordinated to increase the PV penetration from 35.7% to 66.7% of the distribution transformer rating. This work further explores how deficiencies in both reactive power control (RPC) and active power control (APC) as separate approaches can be mitigated by suitably combining RPC and APC algorithms. A novel “Q” or “PF” limiter was proposed to restrict frequent switching between the two droop characteristics while ensuring a stabilizing (smoothened) voltage profile in each of the PV installed nodes. This novel approach not only alleviates the voltage fluctuation but also reduces the overall network losses

Probabilistic Risk Assessment of Power Quality Variations and Events under Temporal and Spatial Characteristic of Increased PV Integration in Low-Voltage Distribution Networks

The aim of this paper is to perform a probabilistic risk assessment of power quality variations and events that may arise due to high photovoltaic distributed generation (PVDG) integration in a low-voltage distribution network (LVDN). Due to the spatial and temporal behavior of PV generation and load demand, such an assessment is vital before integrating PVDG at the existing load buses. Two power quality (PQ) variations such as voltage magnitude variation and phase unbalance together with one PQ abnormal event are considered as the PQ impact metrics. These PQ impact metrics are assessed in terms of two PQ indices, namely site and system indices. A Monte Carlo based simulation is applied for the probabilistic risk assessment. From the results, site overvoltage shows a likely impact to observe as the PVDG integration increases. The probability of 20% of customers violating 1.1 p.u. at 100% penetration level is 0.5. Integration of PVDG reduces the voltage unbalance as compared with no or low PVDG penetration. There is a higher probability of observing deep sag at the site as PVDG integration increases. This probabilistic approach can be used as a tool to assess the likely impacts due to PVDG integration against the worst-case scenarios

Probabilistics Risk Assessment of Power Quality Variations and Events Under Temporal and Spatial Characteristic of Increased PV Integration in Low Voltage Distribution Networks

Integration of PVDG reduces the voltage unbalance as compared with no or low PVDG penetration. There is a higher probability of observing deep sag at the site as PVDG integration increases. This probabilistic approach can be used as a tool to assess the likely impacts due to PVDG integration against the worst-case scenarios

Enhanced Network Voltage Management (NVM) Techniques Under the Proliferation of Rooftop Solar PV Installation in Low Voltage Distribution Network (LVDN)

Proliferation of rooftop solar PV distributed generator (PVDG) installation in low voltage distribution network (LVDN) imposes voltage fluctuation challenges that are a threat to distribution system operators. Reactive power control (RPC) methods are insufficient in isolation to combat the overvoltage fluctuations manifested in LVDN with significant grid-tied PVDG installations. Whereas active power curtailment (APC) control can alleviate the voltage fluctuation in such situations and it is achieved at the cost of reduced active power injection. This paper explores how deficiencies in both RPC and APC as separate approaches can be mitigated by suitably combining RPC and APC algorithms. Strategies combining two RPCs and one RPC in conjunction with APC are proposed as two coordinating algorithms by means of instantaneous measurement of node voltage and active power. These coordinating algorithms are embedded in all the rooftop PVDG grid-tied-inverters (GTI), where the GTI coordinates among them for voltage support without exceeding individual inverter VA rating. The result of the combined approach show significant improvement in managing and stabilising the voltage and allows the penetration of PVDG to be increased from 35.65% to 66.7% of distribution transformer (DT) kVA rating

Application of demand response to improve voltage regulation with high DG penetration

The ability of a consumer friendly demand response based voltage control (DR-VC) program to improve the voltage regulation in a low voltage distribution network (LVDN) with high penetration of DG is investigated. The use of active and reactive power management to regulate the nodal voltage in a distribution network with simple incremental reduction algorithm, in conjunction with DR, is proposed as a solution for over voltage and undervoltage issues in the LVDN. The algorithm micromanages the load and generation in the network enabling the operator to utilize grid resources economically and efficiently while maintaining fairness between consumers with minimum inconvenience. The algorithm is tested on a representative. 74-load radial urban distribution network (Dublin, Ireland) using consumer load and DG generation profiles. The system is modelled and analysed using COM interface between OpenDSS and MATLAB. The DR is modelled through a mixed integer linear programming (MILP), implemented in CVX, such that consumer inconvenience is prioritized. The DR-VC algorithm is capable of regulating load and generation within normal operation limits during undervoltage and overvoltage scenarios