10-kVA grid following converter with LCL filter, power control

This example simulates a grid following controlled converter connected to a strong grid through an LCL filter. The control system includes a phase-locked loop (PLL) to synchronize with the grid, a current reference generatior and a PI-based current controller.

Imports.

import numpy as np
from gritulator import model, control
from gritulator import BaseValuesElectrical, plot_grid

# To check the computation time of the program
import time
start_time = time.time()

Compute base values based on the nominal values (just for figures).

base_values = BaseValuesElectrical(
    U_nom=400, I_nom=14.5, f_nom=50.0, P_nom=10e3)

Create the system model.

# grid impedance and filter model
grid_filter = model.LCLFilter(L_fc=3.7e-3, C_f=8e-6, L_fg = 3.7e-3, L_g=0, R_g=0)
# AC grid model (either constant frequency or dynamic electromechanical model)
grid_model = model.StiffSource(w_N=2*np.pi*50)
converter = model.Inverter(u_dc=650)
mdl = model.ac_grid.StiffSourceAndLCLFilterModel(
    grid_filter, grid_model, converter)

Configure the control system.

# Control parameters
pars = control.grid_following.GridFollowingCtrlPars(
            L_f=3.7e-3,
            f_sw = 8e3,
            T_s = 1/(16e3),
            i_max = 1.5*base_values.i,
            on_u_cap = 1,
            )
ctrl = control.grid_following.GridFollowingCtrl(pars)

Set the time-dependent reference and disturbance signals.

# Set the active and reactive power references
ctrl.p_g_ref = lambda t: (t > .02)*(5e3)
ctrl.q_g_ref = lambda t: (t > .04)*(4e3)

# AC-voltage magnitude (to simulate voltage dips or short-circuits)
e_g_abs_var =  lambda t: np.sqrt(2/3)*400
mdl.grid_model.e_g_abs = e_g_abs_var # grid voltage magnitude

Create the simulation object and simulate it.

sim = model.Simulation(mdl, ctrl, pwm=False)
sim.simulate(t_stop = .1)

# Print the execution time
print('\nExecution time: {:.2f} s'.format((time.time() - start_time)))

Execution time: 0.73 s

Plot results in SI or per unit values.

plot_grid(sim, base=base_values,plot_pcc_voltage=True)

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