Glossary

Power system terminology used in Cobre, with Portuguese equivalents where they appear in documentation or Brazilian regulatory context.

Power System

English	Portuguese	Definition
Block	Patamar	An intra-stage time period (e.g., peak, shoulder, off-peak) representing load level variation within a stage; can be parallel (independent) or chronological (sequential)
Bus	Barramento	A node in the electrical network where components connect
Line	Linha / Circuito	A transmission line or transformer connecting two buses
Subsystem	Subsistema	A region of the interconnected grid (e.g., SE/CO, S, NE, N in Brazil)
Exchange	Intercâmbio	Power transfer between subsystems
Load	Carga / Demanda	Electrical power consumption at a bus
Deficit	Déficit	Unmet demand — load that cannot be served by available generation

Hydro Generation

English	Portuguese	Definition
Hydro plant	Usina hidrelétrica (UHE)	A hydroelectric generating station
Reservoir	Reservatório	Water storage volume behind a dam
Storage	Armazenamento	Current water volume in a reservoir (hm³)
Inflow	Afluência / Vazão natural	Natural water flow arriving at a reservoir
Turbined outflow	Vazão turbinada	Water passing through turbines to generate electricity
Spillage	Vertimento	Water released from a reservoir without generating electricity
Cascade	Cascata	Sequence of hydro plants along the same river
Downstream	Jusante	Direction of water flow; the plant that receives outflow from upstream
Upstream	Montante	Direction against water flow
Productivity	Produtibilidade	Conversion factor from water flow (m³/s) to power (MW)
Run-of-river	Fio d’água	Hydro plant with no significant storage capacity
Diversion	Desvio	Water bypassed to a separate channel, not passing through turbines
Evaporation	Evaporação	Water loss from the reservoir surface due to heat
Forebay level	Nível de montante	Water level at the upstream face of the dam, a function of reservoir storage
FPHA	-	Four-Point Head Approximation — piecewise-linear model of hydro generation as a function of storage, flow, and spillage
Head	Queda	Height difference between reservoir level and tailrace level, determining generation efficiency
Tailrace level	Nível de jusante	Water level at the downstream channel below the dam, a function of total outflow

Thermal Generation

English	Portuguese	Definition
Thermal unit	Usina termelétrica (UTE)	A fossil-fuel or nuclear generating station
Minimum generation	Geração mínima / Inflexibilidade	Minimum output when the unit is committed
Operating cost	Custo variável unitário / CVU	Variable cost per MWh of generation
Startup cost	Custo de partida	Cost incurred when bringing a unit online

Stochastic Modeling

English	Portuguese	Definition
Scenario	Cenário	One realization of uncertain quantities (inflows, wind, etc.)
Stage	Estágio	A time period in the planning horizon
State variable	Variável de estado	Variables that link one stage to the next (storage, lagged inflows)
PAR(p)	PAR(p)	Periodic Autoregressive model of order p for inflow generation
Historical record	Registro histórico	Observed inflow data used to fit stochastic models
Innovation	Inovação	The independent noise term $ε_{t} \sim N (0, 1)$ in the PAR(p) model, representing the unpredictable component after removing autoregressive structure
Yule-Walker equations	Equações de Yule-Walker	System of linear equations relating autoregressive coefficients to sample autocorrelations, used to fit PAR(p) model parameters

SDDP Algorithm

English	Portuguese	Definition
Cut (Benders cut)	Corte (de Benders)	A linear inequality approximating the future cost function
Cost-to-go function	Função de custo futuro (FCF)	Expected cost from the current stage to the end of the horizon
Forward pass	Passagem direta	Simulation phase: solve stages sequentially under sampled scenarios
Backward pass	Passagem reversa	Optimization phase: generate cuts by solving from the last stage backward
Lower bound	Limite inferior	Estimate from the first-stage problem (improves with more cuts)
Upper bound	Limite superior	Statistical estimate from simulation (converges to true cost in risk-neutral setup)
Optimality gap	Gap de otimalidade	Difference between upper and lower bounds, as a percentage
Dual variable	Variável dual / Multiplicador	Shadow price from LP solution; indicates marginal value of a resource
Marginal cost (CMO)	Custo Marginal de Operação	Shadow price of the demand constraint — the cost of one additional MWh
Cut pool	Conjunto de cortes	Collection of all generated Benders cuts for a given stage
Discount factor	Fator de desconto	Multiplicative factor $d \in (0, 1]$ applied to future costs reflecting the time value of money; required for infinite-horizon SDDP convergence
Epigraph variable	-	The auxiliary LP variable $θ$ that lower-bounds the true cost-to-go function $V_{t + 1} (x_{t})$ ; named after the epigraph of a convex function
Infinite horizon	Horizonte infinito	Policy graph with cyclic transitions, used for long-term planning
Opening	Abertura	A pre-generated scenario noise vector used in the backward pass
Opening tree	Árvore de aberturas	The fixed set of pre-generated noise vectors used in the backward pass; generated once before training begins and reused across all iterations. Each stage has `num_scenarios` noise vectors. See Scenario Generation.
Outer approximation	Aproximação exterior	The piecewise-linear lower bound on the cost-to-go function constructed from Benders cuts; the primary output of SDDP training
Policy graph	Grafo de política	Directed graph defining the stage structure and transitions in an SDDP problem
Relatively complete recourse	Recurso relativamente completo	Property that every LP subproblem is feasible for all incoming states and scenario realizations; ensured in Cobre via penalty slack variables
Trajectory record	Trajetória	Data structure capturing one stage’s forward pass result: primal solution, dual solution, stage cost, and end-of-stage state. Used for cut coefficient extraction in the backward pass and for simulation output
Trial point	Ponto amostral	The state visited during a forward pass, used to construct cuts in the backward pass

Risk Measures

English	Portuguese	Definition
Coherent risk measure	Medida de risco coerente	A risk measure satisfying monotonicity, translation equivariance, positive homogeneity, and subadditivity; CVaR is the canonical example used in SDDP
CVaR	CVaR	Conditional Value at Risk — expected cost in the worst α% of scenarios
EAVaR	-	Expectation plus Average Value-at-Risk; the convex combination $(1 - λ) E [Z] + λ \cdot CVaR_{α} [Z]$ used as Cobre’s risk measure
Risk-neutral	Neutro ao risco	Optimization that minimizes expected cost only
Risk-averse	Averso ao risco	Optimization that penalizes high-cost tail scenarios

Brazilian Ecosystem

Term	Definition
NEWAVE	Long-term hydrothermal dispatch model (monthly, 5–10 years)
DECOMP	Medium-term model (weekly resolution)
DESSEM	Short-term model (hourly/half-hourly, day-ahead)
GEVAZP	Synthetic scenario generation tool
ONS	Operador Nacional do Sistema Elétrico — Brazilian grid operator
CCEE	Câmara de Comercialização de Energia Elétrica — electricity trading chamber
CEPEL	Centro de Pesquisas de Energia Elétrica — R&D center that develops the official programs
SIN	Sistema Interligado Nacional — the Brazilian interconnected power system

Solver

English	Portuguese	Definition
Basis	Base	The set of basic variables defining a vertex of the LP feasible region
CLP	-	Open-source LP solver from COIN-OR, used as a reference backend in cobre-solver
HiGHS	-	Open-source LP/MIP solver used as the default backend in cobre-solver
LP (Linear Program)	Programa Linear	An optimization problem with a linear objective and linear constraints
RowBatch	-	A batch of LP rows (constraints) in CSR sparse format for bulk addition to a solver instance via the `add_rows` method
Simplex method	Método Simplex	Algorithm for solving linear programs by traversing vertices of the feasible polytope
Warm-start	Partida a quente	Reusing a previous solution basis to accelerate solving a modified LP

Data Formats

English	Portuguese	Definition
Arrow	-	In-memory columnar data format for analytics; Parquet is its on-disk counterpart
CSC (Compressed Sparse Column)	-	Column-major sparse matrix format used for stage LP templates passed to solvers
CSR (Compressed Sparse Row)	-	Row-major sparse matrix format used for batch cut addition via solver addRows APIs
FlatBuffers	-	Zero-copy serialization library used for policy data (cuts, states)
Parquet	-	Columnar file format for efficient storage and retrieval of large tabular datasets

HPC (High-Performance Computing)

English	Portuguese	Definition
MPI	-	Message Passing Interface — standard for distributed-memory parallel computing
NUMA	-	Non-Uniform Memory Access — hardware topology where memory access time depends on processor-memory proximity
OpenMP	-	API for shared-memory parallel programming via compiler directives; Cobre uses Rayon (Rust data-parallelism library) instead of OpenMP for intra-node thread parallelism
Rayon	-	Rust data-parallelism library used for intra-node thread parallelism in Cobre; provides work-stealing parallel iterators as a safe, idiomatic alternative to OpenMP
Rank	-	An MPI process; each rank has its own address space
Thread affinity	-	Binding of threads to specific CPU cores to prevent migration and ensure NUMA-local memory access

Cobre Ecosystem

English	Portuguese	Definition
Solver vertical	-	A complete solver algorithm stack built on the Cobre ecosystem (e.g., SDDP for hydrothermal dispatch, OPF for power flow)
Ecosystem vision	-	The design goal of Cobre as a generic power system ecosystem with multiple solver verticals sharing a common data model and HPC infrastructure

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