Doktrin pengasingan kuasa : falsafah, praktis dan kerelatifan di Malaysia

Penulisan ini membincangkan tentang doktrin pengasingan kuasa berdasarkan kerangka teori institusionalisme. Doktrin ini dipraktiskan dalam trias politica atau politik tiga serangkai iaitu badan legislatif, eksekutif dan kehakiman. Falsafah dan praktis doktrin pengasingan kuasa ini adalah ditekankan bagi sesebuah negara bercorak demokrasi untuk mempamerkan wujudnya pengasingan kuasa serta autonomi bidangan di antara ketigatiga badan kerajaan. Hal ini penting untuk disoroti kerana Malaysia tidak terkecuali daripada mengamalkan sistem demokrasi dan pada masa yang sama mempraktiskan doktrin pengasingan kuasa dalam kerajaan federalisme berlapisnya sebagai satu pegangan fundamental. Akauntabiliti untuk menzahirkan doktrin pengasingan kuasa ini merupakan perkara yang penting memandangkan ia telah dimaktubkan dalam Perlembagaan Persekutuan

Distributed photovoltaic systems: Utility interface issues and their present status. Intermediate/three-phase systems

The interface issues between the intermediate-size Power Conditioning Subsystem (PCS) and the utility are considered. A literature review yielded facts about the status of identified issues

Integration of Utility-Scale Variable Generation into Resistive Networks.

Wind and solar power account for half of newly installed electricity generation capacity worldwide. Due to falling technology costs, this trend is expected to continue despite the global economic turmoil and uncertainty over policy incentives for these fledgling sectors. A sizable portion of this capacity is connected to sub-transmission networks that typically have mesh configurations and are characterized by resistive lines (i.e. lines with X=R 4). The resistivity of subtransmission networks creates a strong coupling between power flows and voltage magnitudes that is atypical in high-voltage transmission systems. In the presence of generation variability, this can lead to extreme voltages, unacceptable voltage fluctuations, unusual (active and reactive) power flow patterns throughout the network, line congestions and increased losses. This can also cause excessive tap-changing operation of transformers with On-Load Tap Changers (OLTCs). These issues can be substantially mitigated with flexible methods of network operation and control. This dissertation examines the impact of variable embedded generation on the voltage profile, structural stability and the OLTC operation of the DTE/ITC network serving Eastern Michigan. It introduces a number of tools and methods to analyze the impact of variable generation in meshed resistive networks. It investigates how network resistivity transforms the impact of the reactive compensation, associated with variable generation, on the structural stability of the system. Finally an optimal voltage control scheme is presented to better coordinate the voltage regulation of variable generation with OLTCs, reduce network losses and enhance the structural stability of the system. The scheme is a model predictive control with an equivalent mixed integer formulation which models the hybrid dynamics of OLTC tap operations.PhDElectrical Engineering: SystemsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/113584/1/sinasb_1.pd

A probabilistic method for the operation of three-phase unbalanced active distribution networks

YesThis paper proposes a probabilistic multi-objective optimization method for the operation of three-phase distribution networks incorporating active network management (ANM) schemes including coordinated voltage control and adaptive power factor control. The proposed probabilistic method incorporates detailed modelling of three-phase distribution network components and considers different operational objectives. The method simultaneously minimizes the total energy losses of the lines from the point of view of distribution network operators (DNOs) and maximizes the energy generated by photovoltaic (PV) cells considering ANM schemes and network constraints. Uncertainties related to intermittent generation of PVs and load demands are modelled by probability density functions (PDFs). Monte Carlo simulation method is employed to use the generated PDFs. The problem is solved using ɛ-constraint approach and fuzzy satisfying method is used to select the best solution from the Pareto optimal set. The effectiveness of the proposed probabilistic method is demonstrated with IEEE 13- and 34- bus test feeders

Volt/var control with high solar PV penetration in distribution systems and its impact on the transmision grid

With increasing distributed energy resources (DERs), both the distribution and transmission power systems are witnessing new challenges and opportunities. Voltage rise and voltage fluctuations are becoming major issues in the distribution network due to high solar PV penetration. Nevertheless, the volt/var control (VCC) capability of solar PV devices (inverter based DERs, in general) opens up various opportunities for both the distribution and transmission systems. In this work, we address the challenges in the distribution network and also explore the potential opportunities for the transmission system that can be provided by VCC capability of DERs in high PV penetration environment. The first part of our work addresses the voltage challenges faced by the distribution system due to solar PV penetration by utilizing VVC capabilities of PV smart inverters. In this part, we focus on the slope sensitive local droop VVC recommended by the recent integration standards IEEE1547, rule21 and addresses their major challenges i.e. selection of appropriate parameters under changing conditions, issue of control being vulnerable to instability (or voltage oscillations) and bad set-point tracking performance i.e. high steady state error (SSE). This is achieved by proposing a local real-time adaptive VVC which has two major features i.e. a) it is able to ensure both low SSE and control stability simultaneously without compromising any of the objectives, and; b) it dynamically adapts its parameters to ensure good performance in a wide range of external disturbances such as sudden cloud cover, cloud intermittency and substation voltage change. Moreover, the adaptive control does not depend on the feeder topology information. The proposed control is implementation friendly as it fits well within the integration standard framework and depends only on the local bus information. The performance is compared with the existing droop VVC methods under several scenarios on a large unbalanced 3-phase feeder (IEEE 123 bus test system) with detailed secondary side modeling. The second part of our work focus on investigating the impact of DER VVC on the bulk transmission grid. We present a hypothesis that the multitudes of inverter-based DERs can be envisioned as geographically distributed reactive power (var) devices (mini-SVCs) that can offer enhanced var flexibility to a future grid as an ancillary service. To facilitate this vision, a systematic methodology is proposed to construct an aggregated var capability curve of a distribution system with DERs at the substation level, analogous to a conventional bulk generator. Since such capability curve will be contingent to the operating conditions and network constraints, an optimal power flow (OPF) based approach is proposed that takes curtailment flexibility, unbalanced nature of system and coupling with grid side voltage into account along with changing operating conditions. Further, the influence of several other factors such as revised integration standard 1547 on the capability curve is thoroughly investigated on an IEEE 37 bus distribution test system. In the last part of the work, we investigate the DERs\u27 impact on the long-term voltage stability assessment on an integrated T-D system. Finally, a T-D cosimulation is employed to demonstrate how DER aggregated flexibility and var support can potentially enhance the transmission grid performance on an integrated T-D test system