Development of Generalised Integrator with a Feedback Loop Based Dynamic Voltage Restorer for Fast Mitigation of Voltage Sag/Swell

Power-electronic converter-based device called the Dynamic Voltage Restorer (DVR) is intended to shield delicate loads from supply-side voltage perturbations. It is connected in series to the distribution feeder and has the ability to generate or absorb real and reactive power at its AC terminals. This work presents the use of a control scheme based on Generalized Integrator with a Feedback Loop (GIFL) gain choosing technique for the purpose of fast voltage sag/swell detection to enable the DVR to carry out a fast and effective voltage compensation in power distribution system. This helps in significantly reducing the impact of voltage sag/ swell and in turn improve the power quality of the system. Two scenarios were used to analyze the effectiveness of the developed technique: incorporation of voltage sag and swell independently on the distribution system. The results obtained showed that the distortions introduced to the system as a result of the sag and swell was significantly reduced. The results obtained from the developed scheme was further compared with that obtained when the conventional DVR was used in mitigating the voltage sag and swell using total harmonic distortion (THD) as performance metrics. All modelling and analyses were carried out using MATLAB 2019 software

Load-ability Analysis during Contingency with Unified Power Flow Controller Using Grey Wolf Optimization Technique

Voltage stability enhancement with optimal placement of a unified power flow controller considering load-ability analysis is investigated in this paper. It is essential, because when voltage instability is left unattended, it leads to voltage collapse and, consequently, in a partial or total blackout of the whole network resulting from cascading effect. The optimization process is achieved by increasing the percentage load demand index to the maximum load-ability and under single contingency. This method will be of great benefits to bulk dispatcher of power to plan ahead of how to wheel and deliver power to the end-users during both normal and contingency conditions at the least cost and time. A grey wolf optimization technique is utilised to find the optimal location and sizing of UPFC on the network. The line’s voltage stability and load margin are then evaluated with and without UPFC under different loading conditions using optimal power flow technique. The approach’s effectiveness is carried out on 31-bus, 330kV Nigeria National Grid (NNG) based on two scenarios: load-ability analysis under maximum loading of the network and load-ability analysis under single contingency. The results show that power can be transmitted to meet the growing energy demand over an existing network during normal and contingency conditions without violating voltage stability by making use of the proposed method in this pape

An Analysis of Transient Stability Enhancement Capability of UPFC in a Multi-machine Power System

This study presents the transient stability enhancement capability of Unified power flow controller (UPFC) as an effective Flexible AC Transmission System (FACTS) device in a multi-machine power system. The test system was a reduced Nigerian 330kV power system and the focus was on the effect of disturbances on the largest generating unit (Egbin) in the system. The analysis was conducted by simulating a 3-phase fault at two locations; on the terminal of the largest generator unit at Egbin bus and the bus with the largest load at Ikeja–west. The response of the system in both cases was compared with and without the device in operation. Simulations were carried out using the Power System Simulation for Engineering (PSS/E) software. Results showed that, with the UPFC in the network, system transient stability was enhanced considering that critical clearing time of the system was increased from 380ms to 590ms when the fault was at Egbin generator terminal and from 470ms to 510ms following the fault at Ikeja-west. In addition, the device was able to damp power oscillations resulting from the disturbance created by the faults

Glance into solid-state transformer technology: a mirror for possible research areas

Solid-State Transformer (SST), a power electronics based transformer is an emerging technology in electric power system. The transformer is being investigated to completely replace existing Line/Low Frequency Transformer (LFT). SST is composed of either of the two topologies: AC-DC-AC, two steps approach; or AC-AC, single-step approach. The two steps approach consists of three stages: AC-DC; DC-DC; and DC-AC stages. The DC-DC stage is made up of a boost DC-DC converter, a DC-AC inverter and a High Frequency Transformer, HFT. Therefore, SST performs the tasks of LFT by means of power electronic converters and HFT.  The main essence of SST is to provide solution to the problem of bulkiness and heaviness of the LFT in the power distribution network. This is with the view to providing reduction in construction cost, cost of maintenance and transportation. The power electronics transformer provides numerous advantages which are grouped into: The transformer has high power density; it functions in blackouts and brownouts; and it provides easy means of distributed renewable energy integration into associated grid. Therefore, this paper provides a glance into the technology of the SST for its better understating and promotion of research activities in the area

Energy Router Applications in the Electric Power System

Energy router is being investigated to replace conventional transformer in the electric grid. Improvement so far observed in use of converter makes possible the intelligent integration between systems with different characteristics’ in terms of frequency and voltage levels as well as exploitation of generation sources and storage systems typically operating in DC. Consequently, it is believed that Energy Router is able to interconnect different portions of electrical networks and at different voltage levels and types. The Energy Router is an assembly of converters isolated by a medium or high frequency transformer. In its design, different voltage levels and types are made available to achieve high results in terms of system integration, efficiency and flexibility. This paper evaluates the main potentials of this technology if widely introduced in the main power system. Starting from the single component description, a couple of possible applications are presented and discussed