DESSEM is an optimization model that utilizes a mathematical programming solver to address the dispatch problem

To provide consumers with accurate, real-time information on energy consumption, utilities have had to invest in new technologies and adapt to new measurement and reading procedures. This was necessary to comply with Normative Resolution Aneel nº 863/19, which went into effect in January 2021.

Since June, the Electric Energy Trading Chamber (CCEE) has been promoting the development and implementation of a feature within the Integration Platform designed to collect measurement data through distributors’ own infrastructure.

The Electric Energy Research Center (CEPEL), whose activities include conceiving and providing technological solutions specifically geared towards the generation, transmission, distribution, and commercialization of electricity in Brazil, has developed and refined an optimization model for the daily scheduling of electric system operations (DESSEM) for more than two decades.

Recent improvements to the model, especially with the introduction of constraints involving integer variables, led the Center to seek an optimization solver that could be coupled with DESSEM to enable the resolution of the complex mixed-integer optimization problem modeled by the program. After evaluating several alternatives, CEPEL selected IBM’s IBM ILOG CPLEX solution, whose implementation in the DESSEM model was supported by Scala, a Stefanini Group company.

DESSEM is an optimization model for the Daily Operation Scheduling (PDO) of hydrothermal-wind power systems, which considers the modeling of unit commitment constraints of combined cycle or simple cycle thermal power units, a DC modeling of the electrical grid with security constraints, and a detailed modeling of cascade hydroelectric plants.

By coupling IBM ILOG CPLEX, which uses algorithms to solve mathematical problems, the CEPEL model was able to solve the mixed-integer optimization problem in a viable computational time, allowing the National System Operator (ONS) to use the tool for the official dispatch of the operation of the Brazilian electrical system, which has been occurring since January 2020. It has also enabled the Electric Energy Trading Chamber (CCEE) to use the tool for determining hourly pricing, which has been occurring since January 2021. Since both processes are performed daily by these institutions, the adoption of high-quality solutions with very short computational times is essential.

Testing Phase

Scala, a company specializing in Processes, Analytics, and Artificial Intelligence applied to business, was chosen to make this project viable due to achieving the best results in the testing phases. With the contracted solution, which analyzes more than 500,000 variables, CEPEL achieved faster processing times and reproducibility, meaning it ensured the same result in all rounds, an indispensable requirement for the business model. In this way, the accuracy of the measurements, which are capable of precisely stipulating the value down to the 13th decimal place, was guaranteed.

“Several rounds of testing were conducted to further refine the results offered by CPLEX. We assembled a team of specialists who supported the homologation tests in the task force carried out by CEPEL, CCEE, and the National Electric System Operator (ONS) to ensure that the software met all previously defined requirements (execution time and reproducibility), until the ideal solution was found and implemented,” highlights Cristiane de Oliveira Pinto, Business Manager at Scala.

Reproducibility was achieved based on a solution proposed by the CCEE, the AVX, for the execution of DESSEM with CPLEX. André Diniz, Head of the Energy Optimization Department (DEA) at CEPEL, who followed the entire process of validation, acquisition, and implementation of the tool, says that the technical support provided from the beginning of the project was a differentiating factor in the selection.

Advanced Techniques

“It was a long process until we were able to achieve the desired results with the adoption of a mixed-integer programming solver, due to the large size of the problem solved by the DESSEM model. CEPEL developed an iterative strategy for solving the problem, which includes advanced integer programming techniques and, combined with the quality of CPLEX and the effort in adjusting parameters of the package, resulted in obtaining a very robust solution. Scala was willing to provide the necessary support in this last aspect to make the use of the DESSEM CPLEX solver viable. They demonstrated the competence of the product without sparing any effort, with a highly specialized team, which was important in the process of adopting the solution as the official solver for the DESSEM model,” says Diniz.

The electricity sector has numerous agents (power generation, transmission, and commercialization companies) interested in using the DESSEM model. The fact that CPLEX has been adopted by CEPEL for the mathematical optimization of the DESSEM model means that most of these companies acquire the IBM solution, marketed by Scala, as a prerequisite for the operation of the model, which has the basic principle of coordinating the operation of hydroelectric, thermoelectric, and wind power plants, in order to produce a solution with the lowest thermal generation cost and, mainly, ensuring the operational safety of the system from an electrical and energy perspective.

“Since the end of last year, several system agents have been acquiring the DESSEM model. There are still a number of companies interested, as the official operation of the model begins on January 1, 2021. The trend is that we will have a high demand for new implementations over time,” says José Carlos Pires, CEO of Scala.

Once CPLEX is coupled with DESSEM, it is no longer necessary to perform new parameterizations in the latest versions of the model, which simplifies new implementations. “It is essential that companies seek fast optimization models that can bring significant improvements and results to the business,” explains Fabricio Lira, Data and Artificial Intelligence Leader at IBM. “Various industries are undergoing digital transformation, and the energy sector could not be different. We are happy to help CEPEL on its journey, especially in this project that will ultimately bring benefits directly to the consumer,” he concludes.