在 Pyomo 約束中定義循環/周期性邊界條件

Question

我正在嘗試在使用循環條件的 Pyomo 模型上定義約束。 下面是我認為它應該如何工作（來自 GAMS 的循環語法）。

from __future__ import division
from pyomo.environ import *

model = ConcreteModel()

## define sets
model.t                 = Set(initialize = [i for i in range(8760)]) 

## define variables
model.ESS_SOC           = Var(model.t, domain = NonNegativeReals) # battery state of charge
model.ESS_c             = Var(model.t, domain = NonNegativeReals) # battery charging
model.ESS_d             = Var(model.t, domain = NonNegativeReals) # battery discharging

## skip obj for this example

## define constraints
#SOC constraint
model.SOC_const = ConstraintList()
for i in model.t: 
    model.SOC_const.add( model.ESS_SOC[i] == model.ESS_SOC[i--1] + model.ESS_c[i] - model.ESS_d[i] )

但是當我運行上面的示例時，我收到以下錯誤消息：

KeyError: "Index '8760' is not valid for indexed component 'ESS_SOC'"

鑒於model.t的定義，我同意該錯誤，但該錯誤讓我相信它幾乎正在做我想要它做的事情，這將是：

model.ESS_SOC[0] == model.ESS_SOC[8759] + model.ESS_c[0] - model.ESS_d[0]
model.ESS_SOC[1] == model.ESS_SOC[0] + model.ESS_c[1] - model.ESS_d[1]
...
model.ESS_SOC[8759] == model.ESS_SOC[8758] + model.ESS_c[8759] - model.ESS_d[8759] 

有沒有辦法定義約束，這就是我得到的？

Answer 1

我建議使用索引約束而不是ConstraintList來執行此操作：

from __future__ import division
from pyomo.environ import *

model = ConcreteModel()

## define sets
model.t                 = Set(initialize = [i for i in range(8760)], ordered=True) 

## define variables
model.ESS_SOC           = Var(model.t, domain = NonNegativeReals) # battery state of charge
model.ESS_c             = Var(model.t, domain = NonNegativeReals) # battery charging
model.ESS_d             = Var(model.t, domain = NonNegativeReals) # battery discharging

## skip obj for this example

## define constraints
#SOC constraint
def _SOC_const(m, i):
    if i == m.t.first():
        return model.ESS_SOC[i] == model.ESS_SOC[m.t.last()] + model.ESS_c[i] - model.ESS_d[i]
    return model.ESS_SOC[i] == model.ESS_SOC[i-1] + model.ESS_c[i] - model.ESS_d[i]
model.SOC_const = Constraint(model.t, rule=_SOC_const)

請注意，您需要在Set上Set ordered=True選項才能使first()和last()方法工作。