I am currently using Python. However, I am struggling with one error. This is the tool I have made so far.
from gekko import GEKKO
import numpy as np
m = GEKKO(remote=False)
m.options.SOLVER = 1
hour = 24
Num_EV = 1
p_i =m.Array(m.Var,(hour,Num_EV))
TOU = [64.9,64.9,64.9,64.9,64.9,64.9,64.9,64.9,152.6,239.8,
239.8,152.6,239.8,239.8,239.8,239.8,152.6,152.6,
152.6,152.6,152.6,152.6,152.6,64.9]
n=len(TOU)
inp = m.Array(m.Var, (n), value=0.0, lb=0.0, ub=7.0, integer=True)
# EV min/Max setting
for tt in range(0,hour):
p_i[tt,0].lower = 30
p_i[tt,0].upper = 70
# EV Charger min/Max setting
Num_EV_C = 1
p_j = m.Array(m.Var, (hour, Num_EV_C))
for tt in range(0,hour):
p_j[tt,0].lower = 0
p_j[tt,0].upper = 7
# s.t : EV SOC
p_i[0,0] = 30 # inital EV SOC
eq_EV_SOC = np.zeros((hour,1))
eq_EV_SOC = list(eq_EV_SOC)
for tt in range(0,hour):
for i in range(0,Num_EV):
eq_EV_SOC[tt] = p_i[tt-1,i] + p_i[tt,i] == p_i[tt,0]
m.Equation(eq_EV_SOC)
# s.t : EV charging rate
p_j[0,0] = 0
eq_EV_C = np.zeros((hour,1))
eq_EV_C = list(eq_EV_C)
for tt in range(0,hour):
for i in range(0,Num_EV_C):
eq_EV_C[tt] = p_j[tt,0] >= p_j[tt,i]
m.Equation(eq_EV_C)
# Object Function : sum[i=n]*sum[t=T]()
F = np.zeros((hour*Num_EV))
F = F.tolist()
for tt in range(0,hour):
for i in range(0,Num_EV):
F[i+tt*Num_EV] = p_i[tt,i] * p_j[tt,i]
F_Obj = m.sum(F)
m.Minimize(F_Obj)
m.solve(disp=True)
Exception: @error: Equation Definition
Equation without an equality (=) or inequality (>,<) true STOPPING...
I want to know this problem. Below is a description of constraints and objective functions.
st is constraint. First constraint is EV SOC range. EV SOC minimum is 30 and Maxmium is 70. EV SOC form is (inital SOC + time by EV SOC). Second constraint is EV Charging range. EV Charging range is from 0 to 7. Finally, Object function is to minimize the product of tou and charging rate.
There are a few problems with the model that can be observed by opening the model file in the run directory. Use m.open_folder()
and open the gk_model0.apm
file with a text editor. Here are some of the equations that indicate that there is a problem with the formulation:
True
v50>=v50
v51>=v51
v52>=v52
v53>=v53
The True
expression is because a constant is evaluated with another constant in the first cycle of:
for tt in range(0,hour):
for i in range(0,Num_EV_C):
eq_EV_C[tt] = p_j[tt,0] >= p_j[tt,i]
This gives a Boolean True
result.
The initial EV SOC should either be changed to fixed
or else include a simple equation:
# s.t : EV SOC
m.Equation(p_i[0,0]== 30) # inital EV SOC
# s.t : EV charging rate
m.Equation(p_j[0,0]==0)
It appears that the charging rate should decrease over time with this constraint:
m.Equation(p_j[0,0]==0)
for tt in range(0,hour):
for i in range(1,Num_EV_C):
m.Equation(p_j[tt,0] >= p_j[tt,i])
The index is changed to p_j[tt,0] >= p_j[tt,i]
so that p_j[tt,0] >= p_j[tt,0]
is not included as an equation. Should the range for time also be adjusted here to start at 1
?
for tt in range(1,hour):
for i in range(0,Num_EV):
m.Equation(p_i[tt-1,i] + p_i[tt,i] == p_i[tt,0])
The problem is currently infeasible, even with these corrections. Maybe this problem can help:
from gekko import GEKKO
import numpy as np
import matplotlib.pyplot as plt
m = GEKKO()
m.options.SOLVER = 1
m.options.IMODE = 3
Num_car = 1
TOU = [64.9,64.9,64.9,64.9,64.9,64.9,64.9,64.9,152.6,239.8,
239.8,152.6,239.8,239.8,239.8,239.8,152.6,152.6,
152.6,152.6,152.6,152.6,152.6,64.9]
n=len(TOU)
inp = m.Array(m.Var, (n), value = 0.0,
lb = 0.0, ub = 7.0, integer = True)
SOC_Min = 30; SOC_Max = 90
# set bounds 30-90
SOC_t = m.Array(m.Var,(n, Num_car),lb=SOC_Min,ub=SOC_Max)
# set new bounds 30-70
for tt in range(0,n):
for j in range(Num_car):
SOC_t[tt,j].lower = 30
SOC_t[tt,j].upper = 70
for j in range(Num_car):
# initial SOC
m.Equation(SOC_t[0,j]==30) # initial charge at start
m.Equation(SOC_t[n-1,j]==70) # desired charge at end
for tt in range(1,n):
m.Equation(SOC_t[tt,j] == SOC_t[tt-1,j] + inp[tt])
for tt in range(n):
m.Minimize(TOU[tt]*inp[tt])
m.options.IMODE = 3
m.options.SOLVER = 1
m.solve(disp=True)
plt.figure(figsize=(8,5))
plt.subplot(3,1,1)
for j in range(Num_car):
p = np.empty(n)
for tt in range(n):
p[tt] = SOC_t[tt,j].value[0]
plt.plot(p,'r.-',label='vehicle '+str(j+1))
plt.legend(); plt.ylabel('SOC'); plt.grid()
plt.subplot(3,1,2)
p = np.empty(n)
for tt in range(n):
p[tt] = inp[tt].value[0]
plt.plot(p,'ko-',label='charge rate')
plt.legend(); plt.ylabel('charge'); plt.grid()
plt.subplot(3,1,3)
plt.plot(TOU,'bs-',label='electricity price')
plt.ylabel('price'); plt.grid()
plt.legend(); plt.xlabel('Time (hr)')
plt.tight_layout()
plt.savefig('soc_results.png',dpi=300)
plt.show()
This is a solution to this question: How to optimize the electric vehicle charging cost using Gekko? It looks like you may be working on a similar problem.
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