Patient information leaflets (PILs) for UK randomised controlled trials : a feasibility study exploring whether they contain information to support decision making about trial participation

Peer reviewedPublisher PD

Allocation of fixed transmission costs by tracing compliant postage stamp method

Postage stamp allocation is unfair to those users who make limited usage of the network. MW power flow tracing was invented to assess the extent of network usage. MW power tracing, a post-facto analysis of power flow solution, is amenable to multiple solutions. This implies multiplicity of solution space of cost allocation problem. Existing tracing methods enforce a 'proportionate sharing rule' to solve the dilemma. Case studies indicate that with such a sharing rule, extent of network usage predicted for large and distant loads can be much higher than the postage stamp allocation. To alleviate this problem, we propose a tracing compliant modified postage stamp allocation method which computes a traceable solution that minimizes deviation from the postage stamp allocation. We show that tracing problem can be formulated as a linear constrained optimization problem. Thus, fairness among all network users is ascertained. Results on actual data of central transmission utility of Western Regional Grid of India demonstrate the claims.© IEE

New paradigm of tracing algorithms : application to fair loss allocation in Indian system

MW power flow tracing was invented to assess the extent of network usage by the participants so as to allocate the transmission charges and losses. MW power tracing, a post-facto analysis of power flow solution, is amenable to multiple solutions. This implies multiplicity of solution space of cost and loss allocation problem. Existing tracing methods enforce a 'proportionate sharing rule' to arrive at a solution. Case studies indicate that with such a sharing rule, extent of network usage predicted for large and distant loads can be much higher than the postage stamp or pro-rata allocation. To alleviate this problem, we suggest a new paradigm or MW power tracing algorithms wherein, we exploit the multiplicity of solution space so as to achieve a fair and equitable distribution of losses among the participants. We show that real power tracing represents a generic class of multi-commodity network flow problems and can be formulated as a linear constrained optimization problem. We propose a tracing compliant modified postage stamp allocation method which computes a traceable solution that minimizes deviation from the postage stamp allocation of losses. Results on practical data of central transmission utility of Western Regional Grid of India demonstrate the claims

Tractability of bilateral transactions considering multiplicity of solution space in real power tracing

Most of the tracing algorithms proposed so far are the variants of proportionality based tracing algorithm. However, proportional sharing is not an inherent characteristic of the system. It is a rule enforced to attain uniqueness of the solution in a fair manner. Under proportionate tracing regime, the bilateral transactions can be classified as tractable, partially tractable or intractable, based on degree of tractability. In this paper, we develop the concept of optimal tracing whose objective is to enforce maximum tractability of bilateral transactions, while attaining least deviation from the proportionate sharing results, using multiplicity of solution space. The resulting optimization formulation is shown to be a sparse linear programming (LP) problem. A unified formulation that models lossy MW flow network and provides consistent results for generation and load tracing is presented. The maximum tractability is modeled as soft constraint in the formulation. Illustrative examples and simulation results on IEEE-30 bus system demonstrate the claims.© IEE

Min-max fairness criteria for transmission fixed cost allocation

Conventionally, transmission fixed cost allocation is carried out on postage stamp basis. Amongst various other ways of solving the problem, the cost allocation under the "usage-based"domain has also been suggested, namely, based on proportionate tracing and recently, by optimization based real power tracing. Changing the cost allocation regime from postage stamp basis to usage-based methods, though technically sound, can pose fairness issue. The fairness criteria in its simplest form would allocate cost in equitable manner on per unit basis while meeting the constraints. The optimization-based tracing provides room for defining an objective, leading to tracing compliant postage stamp method, that strikes a balance in allocation between conventional postage stamp and proportionate tracing-based methods. In this paper, we address this complex cost sharing problem by suggesting a min-max fairness algorithm, using optimization-based real power tracing. The min-max algorithm achieves fairness by equalizing allocations within constrained space and reaching an equilibrium where further balancing cannot be achieved. We show that computing min-max fair solution simply corresponds to solving a sequence of sparse LP problems for real power tracing. The algorithm satisfies the property of aggregate invariancy. Results on actual data of central transmission utility of Western Regional Grid of India, as well as IEEE 30-bus system, validate the claims. The results are compared with the tracing compliant postage stamp method.IEE

Tractability of bilateral transactions considering multiplicity of solution space in real power tracing

Most of the tracing algorithms proposed so far are the variants of proportionality based tracing algorithm. However, proportional sharing is not an inherent characteristic of the system. It is a rule enforced to attain uniqueness of the solution in a fair manner. Under proportionate tracing regime, the bilateral transactions can be classified as tractable, partially tractable or intractable, based on degree of tractability. In this paper, we develop the concept of optimal tracing whose objective is to enforce maximum tractability of bilateral transactions, while attaining least deviation from the proportionate sharing results, using multiplicity of solution space. The resulting optimization formulation is shown to be a sparse linear programming (LP) problem. A unified formulation that models lossy MW flow network and provides consistent results for generation and load tracing is presented. The maximum tractability is modeled as soft constraint in the formulation. Illustrative examples and simulation results on IEEE-30 bus system demonstrate the claims.© IEE

Multiple solutions approach to tackle circular flows in real power tracing

Real power tracing algorithms were invented to find the network usage by various generators and loads. Two versions of real power tracing are popularly quoted: linear equations based and graph theoretic based. Both the methods make use of proportional sharing assumption. When the directed graph of power flow is cyclic, the graph theoretic approach is not able to proceed further, while the linear equations based approach may or may not fail depending on the distribution matrix structure. In this paper, we propose a new paradigm of real power tracing algorithms in which we show that the tracing problem can be formulated as a linear constrained multi-commodity network flow optimization problem. By exploiting multiplicity of solution space in real power tracing, it is shown that the proposed method converges to a solution even in the presence of circular flows by virtue of its constraint modeling. Results on practical data of Western Regional Grid of India demonstrate the usefulness of the method.© IEE

Optimization approach to real power tracing: an application to transmission fixed cost allocation

Megawatt (MW) power flow tracing can assess the extent of network usage by the participants that can be effectively used for multiple objectives like transmission pricing, loss allocation, etc. MW power tracing, a post-facto analysis of power flow solution, is amenable to multiple solutions. This implies multiplicity of solution space of transmission cost and loss allocation problems. The conventional tracing methods enforce a "proportionate sharing rule" to calculate the shares. These shares are sensitive to quantity and distance as against the postage stamp method, which is immune to distance. Any of these methods will result in penalizing a set of constituents, which raises a fairness issue. This is evident from the experiences of developing countries like India. In this paper, a new paradigm is suggested that attempts to capture the best of the two methodologies by exploring multiplicity of the solution space of the tracing problem, within the given constraints. We show that the tracing problem can be formulated as a linear constrained optimization problem. We propose a tracing compliant modified postage stamp allocation method that computes a traceable solution that minimizes overall deviation from the postage stamp allocation. Results on actual data of central transmission utility of Western Regional Grid of India demonstrate the claims.IEE

New paradigm of tracing algorithms: application to fair loss allocation in Indian system

MW power flow tracing was invented to assess the extent of network usage by the participants so as to allocate the transmission charges and losses. MW power tracing, a post-facto analysis of power flow solution, is amenable to multiple solutions. This implies multiplicity of solution space of cost and loss allocation problem. Existing tracing methods enforce a 'proportionate sharing rule' to arrive at a solution. Case studies indicate that with such a sharing rule, extent of network usage predicted for large and distant loads can be much higher than the postage stamp or pro-rata allocation. To alleviate this problem, we suggest a new paradigm or MW power tracing algorithms wherein, we exploit the multiplicity of solution space so as to achieve a fair and equitable distribution of losses among the participants. We show that real power tracing represents a generic class of multi-commodity network flow problems and can be formulated as a linear constrained optimization problem. We propose a tracing compliant modified postage stamp allocation method which computes a traceable solution that minimizes deviation from the postage stamp allocation of losses. Results on practical data of central transmission utility of Western Regional Grid of India demonstrate the claims

Reduced grid operating costs and renewable energy curtailment with electric vehicle charge management

Widespread adoption of plug-in electric vehicles (PEVs) and renewable energy (RE) can help to jointly decarbonize the transportation and electricity sectors. Previous studies indicate strategies to manage PEV charging facilitate integration of RE into electricity grids, but the value of such strategies at scale is unclear because electricity markets and PEV charging have been inadequately represented together. This analysis focuses on the state of California in 2025, and improves on prior work by linking high-resolution mobility and grid dispatch models to quantify the value of managed charging under a 50% RE grid and PEV adoption scenarios up to California's 5 million vehicle target. Even after accounting for practical charging and grid constraints, 0.95 to 5 million “smart” charging PEVs avoid $120 to$690 million in California grid operating costs annually (up to 10% of total costs) and reduce RE curtailment up to 40% relative to unmanaged PEVs. Overnight time-of-use (TOU) charging provides similar cost savings but increases curtailment. Both of these managed strategies defer system infrastructure expansion at the 5 million PEV deployment. The results suggest residential smart charging complemented by TOU tariffs with added daytime periods are policies with most potential to advance California's dual PEV and RE goals