The Collapse of the Coalition of the Weak and Power Sharing in the 1980s

To address inaccurate power sharing problems in autonomous islanding microgrids, an enhanced droop control method through online virtual impedance adjustment is proposed. First, a term associated with DG reactive power, imbalance power, or harmonic power is added to the conventional real power-frequency droop control. The transient real power variations caused by this term are captured to realize DG series virtual impedance tuning. With the regulation of DG virtual impedance at fundamental positive sequence, fundamental negative sequence, and harmonic frequencies, an accurate power sharing can be realized at the steady state. In order to activate the compensation scheme in multiple DG units in a synchronized manner, a low-bandwidth communication bus is adopted to send the compensation command from a microgrid central controller to DG unit local controllers, without involving any information from DG unit local controllers. The feasibility of the proposed method is verified by simulated and experimental results from a low-power three-phase microgrid prototype.

As the numbers of microgrids (MGs) and prosumers are increasing, many research efforts are proposing various power sharing schemes for multiple MGs (MMGs). Power sharing between MMGs can reduce the investment and operating costs of MGs. However, since MGs exchange power through distribution lines, this may have an adverse effect on the utility, such as an increase in peak demand, and cause local overcurrent issues. Therefore, this paper proposes a power sharing scheme that is beneficial to both MGs and the utility. This research assumes that in an MG, the energy storage system (ESS) is the major controllable resource. In the proposed power sharing scheme, an MG that sends power should discharge at least as much power from the ESS as the power it sends to other MGs, in order to actually decrease the total system demand. With these assumptions, methods for determining the power sharing schedule are proposed. Firstly, a mixed integer linear programming (MILP)-based centralized approach is proposed. Although this can provide the optimal power sharing solution, in practice, this method is very difficult to apply, due to the large calculation burden. To overcome the significant calculation burden of the centralized optimization method, a new method for determining the power sharing schedule is proposed. In this approach, the amount of power sharing is assumed to be a multiple of a unit amount, and the final power sharing schedule is determined by iteratively finding the best MG pair that exchange this unit amount. Simulation with a five MG scenario is used to test the proposed power sharing scheme and the scheduling algorithm in terms of a reduction in the operating cost of MGs, the peak demand of utility, and the calculation burden. In addition, the interrelationship between power sharing and the system loss is analyzed when MGs exchange power through the utility network.

Power sharing is often offered as a strategy to resolve political crises. In contrast to power capture and power division, power sharing entails exercising power in cooperation with rival groups. The outcome of power sharing largely rests on the purpose and context of the agreement. Power sharing has proven effective at attenuating political violence and providing stability when enacted to guide a transition from white-minority to black-majority rule in former settler states (e.g., South Africa) or to bring persistent civil wars to an end (e.g., Sierra Leone and Burundi). However, in the context of an election dispute, power sharing fails to solve the underlying concerns that contribute to election-related conflict. Although power sharing may attenuate or end violence, the outcome is poor reconciling election winners and losers and deepening democratic practices (e.g., Kenya and Zimbabwe). Recognizing the failure of power sharing after election disputes, external mediators—particularly in West Africa (e.g., Côte d’Ivoire and The Gambia)—have tended to emphasize maintaining normal constitutional processes rather than power-sharing settlements.

AC/DC hybrid microgrids (HMGs) represent a promising architecture that allows the hosting of a mix of ac/dc energy resources and ac/dc loads. Despite their potential, when islanded, HMGs impose operational challenges among of which are precise and stable power sharing, frequency restoration, and voltage regulation. Imprecise power sharing can result in some distributed generators (DGs) being overloaded, while others being underloaded. This article proposes an optimal-power-flow-based optimal power sharing (OPS) scheme to optimize the droop characteristics of DGs and interlinking converters for global power sharing in a multi-DG HMG regardless of DG location and type. The optimized droop parameters might jeopardize the microgrid stability. Thus, the proposed OPS scheme preserves stable power sharing through stability-constrained optimization of the droop characteristics. In addition to DG overloading because of unequal power sharing, voltage-sensitive loads could possibly suffer from voltage deviations because of drooping the voltage with the load increase. The proposed OPS strategy enjoys the ability to regulate the ac/dc voltage within a desired range and restore the nominal frequency. Steady-state and time-domain simulations verify the effectiveness of the proposed sharing scheme in achieving the underlying objectives. Test results also prove the capability of the OPS scheme in zonal power sharing in the case of a distribution grid with multizone ac/dc microgrids.

Peace accords usually involve top politicians and military leaders, who negotiate, sign, and/or benefit from an agreement. What is conspicuously absent from such negotiations is broad-based participation by those who should benefit in the first place: citizens. More specifically, the local level of security provision and insecurity production is rarely taken into account. The analysis of recent African peace agreements shows important variations in power-sharing devices and why it is important to ask who is sharing power with whom. Experiences with power sharing are mixed and far less positive than assumed by outside negotiators. POWER SHARING LOOKS LIKE A LOGICAL APPROACH to sustainable conflict management in multi-ethnic societies. In fact, it has been proposed time and again and often inscribed in peace agreements. As Jarstad notes, ‘power sharing is attractive to peace negotiators’.1 It might be less so for (all) warring parties and the general population. Negotiators and signatories may ignore and sideline security concerns of ordinary citizens, doing little to address the underlying causes of conflict, and thus reducing the usefulness of power sharing. It is also doubtful whether the power-sharing ingredients of peace agreements are conducive to peace. One problem of the current tendency to establish hasty power-sharing solutions from the outside is the widespread popular perception that democracy is thereby sacrificed in the name of peace. This problem is frequently overlooked in specialized academic debates. In this contribution I first summarize some relevant arguments in the academic debate on power sharing and war termination. In a second step, I screen all recent major African peace agreements (1999–2007) for their power-sharing content. Finally, I analyse two country cases of peace agreements (Liberia and Cote d’Ivoire) and one post-election crisis settlement (Kenya), all of which relied on powersharing ingredients. It will become obvious that power-sharing agreements Andreas Mehler (mehler@giga-hamburg.de) is Director of the Institute of African Affairs at the German Institute of Global and Area Studies, Hamburg. 1. Anna Jarstad, ‘Power sharing for peace and democracy?’ (Paper presented at the 47th annual meeting of the International Studies Association, San Diego, 22–25 March 2006), p. 9. 453 2010 at G IG A G rm an Intitute of G lobal nd A ea S tuies. Libniz Intitut fer G lo on S etem er 9, afraf.oxjournals.org D ow nladed fom

The article is devoted to the study of the influence of institutions of consociative democracy on the processes of pacification and democratization in post-conflict societies. The introductory part defines two approaches to the study of consociative democracy: the first, which recommends consociative democracy as a desirable democratic model for deeply divided societies, and the second, which considers consociation solely as a successful conflict management mechanism without democracy. This article also analyzes the possibility of implementing consociative democracy in Bosnia and Herzegovina as a vivid example of a post-conflict state, where even 30 years after the civil war, disorder and fear of a re-outbreak of interethnic conflict prevail. In this paper, the author tried to explain the reasons that make it difficult to apply consociative democracy in the Balkans in general and in Bosnia and Herzegovina in particular. The research is based on the methodology of A. Leiphart, which is based on a comparative analysis of empirical studies of the experience of political development in a number of states. The methodology is based on a systematic approach, which allows us to consider the object of research as an integral set of elements, as well as a cultural approach that helps to understand the specifics of the interaction of various segments of society in the state chosen for analysis. The novelty of the research lies in a special approach to the study of consociative democracy, which focuses more on the successful establishment of peace in post-conflict societies, rather than on the establishment of democracy in these territories. The author uses the model of A. Leiphart, which assumes consociative democracy as a political model with segmental pluralism, which includes many grounds for dividing people into representatives of certain groups in multi-component societies. Such differences may be religious, linguistic, racial, ethnic, or regional in nature. The main conclusions of this study are the theses that the main function of consociative institutions in post-conflict societies is to prevent the recurrence of violence, not to build democracy. Also, an analysis of the implementation of consociative democracy in Bosnia and Herzegovina shows that the theoretical doctrines of consociation are not easy to apply in practice in the conflict societies of post-Yugoslav states.

Ethiopia’s 1995 Constitution ostensibly created an accommodative multicultural federal governance structure often known in the academic literature as ‘ethnic federalism’. Since then, political inclusion, socio-economic justice and the federal system’s ability to accommodate diversity as well as end conflict in Ethiopia have dominated government rhetoric. However, this chapter argues that the federal system has also harboured exclusion and stoked conflict because of one ethnic group’s claim to domination of an administrative territory. The multi-ethnic community of Yeki Woreda in southern Ethiopia is examined as an example of a common phenomenon elsewhere in the country to illustrate the federal system’s failure to accommodate dispersed ethnic communities and the ensuing ethnic conflict. A more responsive governance alternative based on a ‘consociational democracy’ model is proposed, which would enable ethnic-based power-sharing agreements for minorities in the same political arena at sub-national level. While it suffers from some limitations, Lijphart’s ‘consociational democracy’ model appears to be the most capable of dealing with, if not eliminating, these problems and ultimately regaining peace among multi-ethnic communities.

Institutional engineering offers a solution to the increasing political dissatisfaction in several representative democracies, since studies suggest that introducing elements of institutional power sharing may decrease negative attitudes. However, it may be important to distinguish different mixes of political attitudes since these can have different implications for the functioning of democracy. This article therefore examines the link between horizontal and vertical institutional power sharing and four citizen profiles differing on the extent of political support and subjective political empowerment. The data come from the fourth round of the European Social Survey [ESS (2008) European Social Survey Round 4 Data. Data File Edition 4 (Norway: Norwegian Social Science Data Services)] and comprise 39,376 respondents from 24 democracies. The links between institutional power sharing and kinds of political dissatisfaction are examined with multinomial logistic regression analysis to examine the connections between horizontal and vertical power sharing and different attitudinal profiles to establish the possibilities for institutional engineering. The results suggest that horizontal power sharing is connected to a higher extent of satisfied citizens, but also certain kinds of dissatisfaction. Furthermore, vertical power sharing is connected to a lower probability of satisfied citizens. The effects of power sharing are therefore more intricate than what has previously been assumed when taking into account the multidimensional nature of political attitudes.

The power-sharing literature lacks a review that synthesizes its findings, despite spanning over 50 years since Arend Lijphart published his seminal 1969 article ‘Consociational Democracy’. This review article contributes to the literature by introducing and analysing an original dataset, the Power Sharing Articles Dataset, which extracts data on 23 variables from 373 academic articles published between 1969 and 2018. The power-sharing literature, our analysis shows, has witnessed a boom in publications in the last two decades, more than the average publication rate in the social sciences. This review offers a synthesis of how power sharing is theorized, operationalized and studied. We demonstrate that power sharing has generally positive effects, regardless of institutional set-up, post-conflict transitional character and world region. Furthermore, we highlight structural factors that are mostly associated with the success of power sharing. Finally, the review develops a research agenda to guide future scholarly work on power sharing.

Summary In this paper, a multi-agent-based locally administrated power distribution hub (PDH) for social welfare is proposed that optimizes energy consumption, allocation, and management of battery energy storage systems (ESSs) for a smart community. Initially, formulation regarding optimum selection of a power storage system for a home (in terms of storage capacity) is presented. Afterwards, the concept of sharing economy is inducted in the community by demonstrating PDH. PDH is composed of multiple small-scale battery ESSs (each owned by community users), which are connected together to form a unified-ESS. Proposed PDH offers a localized switching mechanism that takes decision of whether to buy electricity from utility or use unified-ESS. This decision is based on the price of electricity at ‘time of use’ and ‘state of charge’ of unified-ESS. In response to power use or share, electricity bills are created for individual smart homes by incrementing or decrementing respective submeters. There is no buying or selling of power from PDH; there is power sharing with the concept of ‘no profit, no loss’. The objective of the proposed PDH is to limit the purchase of electricity on ‘high priced’ hours from the utility. This not only benefits the utility at crucial hours but also provides effective use of power at the demand side. The proposed multi-agent system depicts the concept of sharing power economy within a community. Finally, the proposed model is analyzed analytically, considering on-peak, off-peak, and mid-level (mid-peak) prices of a real-time price signal during 24 h of a day. Results clearly show vital financial benefits of ‘sharing power economy’ for end users and efficient use of power within the smart community. Copyright © 2017 John Wiley & Sons, Ltd.

According to bargaining theory, one would expect that governments in intrastate conflicts will only be willing to concede to power sharing agreements when they face relatively strong rebel groups. Previous empirical studies have not found support for this hypothesis because they have not operationalized the capability of civil war combatants in relative terms. I show that once one uses a relative measure of capability, one finds that power sharing is more likely as the strength of a rebel group increases. Additionally, the analysis indicates that the relationship between rebel strength and power sharing is stronger for political power sharing than for territorial or military power sharing.

In an islanded hybrid ac/dc microgrid (IHMG), ac and dc subgrids are connected via interlinking converters (ICs). For reliable operation of an IHMG, achieving distributed generators’ power sharing (DGPS) throughout the entire IHMG and ICs’ power sharing (IPS) is the main objective in an IHMG. To improve efficiency of an IHMG, minimizing operating costs of DGs is required and thus cost-minimized DGPS needs to be achieved. Similarly, when multiple ICs operate in an IHMG, efficiency-maximized IPS can further improve the efficiency of an IHMG, as total loss of ICs can vary by the IPS ratios. Thus, this paper proposes a distributed power sharing strategy to achieve cost-minimized DGPS and efficiency-maximized IPS simultaneously, without any communication lines for DGs. Incremental cost-based droop controlled DGs and distributed controlled ICs are coordinated for cost-minimized DGPS and a distributed optimal power sharing method of ICs is proposed to achieve efficiency-maximized IPS. The proposed strategy secures both cost-minimized DGPS and efficiency-maximized IPS, with only sparse communication lines among ICs, thus resulting in a significant improvement in IHMG efficiency and reliability.

The stability and power sharing properties of droop-controlled inverter-based microgrids are adversely affected by model uncertainty, and inverter parameter drifts. Even when frequency stability may be guaranteed, power sharing remains sensitive to clock/frequency drifts. A novel coordinating control law is proposed to overcome these issues. It guarantees both stability and power sharing in the presence of parameter uncertainty, including frequency drift. The new control law uses sparse inter-node communications. Conditions to achieve (local) stability with power sharing are presented. It is also shown that our power sharing control is robust to reasonable clock drifts and very small droop coefficients. Simulation and experimental results illustrate the performance of the proposed control law under clock drift scenarios.

Due to the uncertainty of feeder impedance, conventional droop control-based power sharing scheme presents poor reactive power sharing accuracy in microgrid. As microgrid configuration becomes more and more complicated, reactive power sharing between various distributed generation (DG) equipment is very challenging. To achieve proper power sharing with a simple control method in microgrid, a new structure and power sharing method is proposed in this paper. Instead of using complicated reactive power sharing scheme, this paper proposes separated energy server (ES) units to provide reactive power. Then, active power supplying and reactive power supplying can be achieved separately by energy routers (ERs) and ESs, respectively. With the introduction of ES, the power sharing between DG units can be easily achieved without any supplementary communications or control algorithms. In addition, to reduce costs,a hybrid reactive power compensation configuration with capacitor banks and ESs is provided. Operation principle and power control strategy for DG units and ESs are explained and analyzed in this paper. In order to properly select the coefficients of the power controllers, sensitivity and stability of the system are investigated. Simulation and experimental results are presented to prove the validity of the proposed power sharing method, showing that ERs can effectively share the active power and ESs can effectively share the reactive power according to their capacity.

Nigeria is composed of plural and multi-complex societies with multiple ethnic groups of up to 500 cultural diversities. This country surmounts the obstacles of managing diversity through an informal setting popularly identified as a zoning formula and power sharing among the federating units. The pattern and trend in which the practice maintains Nigeria's diversity is a good lesson for a study of plural societies and consociationalism. The study aimed to examine the nature and dimension of zoning formula and power sharing in Nigeria and analyze how the strategies of zoning formula and power sharing helped manage diversity in Nigeria. The study was identified as a descriptive qualitative method that sought to describe Nigeria's strategy for managing diversity. The study uncovered that power sharing and zoning consist of constitutional and unconstitutional ones, with the former supported by legal provisions. Simultaneously, the latter is designed based on principles and gentleman agreements. The study recommended that constitutional provisions should never be sacrificed on the altar of the personal elite agreement. Instead, sharing power through zoning should be retained to prevent suicide for credibility and competency. It is a plausible shock absorber that will continue to sustain Nigerian federalism, and other plural societies can borrow this model as a political means of resolving diversities.