Fixed power flow on a branch

answered 2023-08-27 21:53:27 -0600

Tassie Dave
91 ●3 ●4 ●7

updated 2023-08-28 10:02:23 -0600

jconto
2701 ●10 ●30 ●41

In order to get a load flow case with the P and Q flow between two busses at a particular level, do an iterative process: - run load flow - measure P and Q flow - adjust P and Q for the generator

here is some sample code:

def dispatch_p_and_pf(p_setpoint, pf_setpoint, p_gen_bus, q_gen_bus, Q_from_bus, Q_to_bus, P_from_bus, P_to_bus):
    # iteratively adjusts two machines in the load flow case, until the P and Q flows between the meas_bus and poc_bus match the setpoints.
    # The machines at which P and Q are adjusted are allowed to be different, for cases where P is set by a generator and Q by a STATCOM
    p_sched = p_setpoint  
    q_sched = default_p_sp *sqrt((1/pf_setpoint)**2 - 1) * np.sign(pf_setpoint)
    count = 0
    p_gen = p_sched 
    q_gen = q_sched
    print('Perror \tQerror \tPctrl \tQctrl \tPgen \tQgen' )
    while count < nbr_solve_iterations:
        psspy.machine_chng_2(p_gen_bus,r"""1""",[_i,_i,_i,_i,_i,_i],[ p_gen,_f,_f,_f,_f,_f,_f,_f,_f,_f,_f,_f,_f,_f,_f,_f])  
        psspy.machine_chng_2(q_gen_bus,r"""1""",[_i,_i,_i,_i,_i,_i],[ _f,q_gen,q_gen,q_gen,_f,_f,_f,_f,_f,_f,_f,_f,_f,_f,_f,_f])  
        psspy.fdns([0,2,0,0,0,0,99,0])
        psspy.fdns([0,2,0,0,0,0,99,0])
        ierr, p_control = psspy.brnmsc(P_from_bus, P_to_bus, '1','P')
        ierr, q_control = psspy.brnmsc(Q_from_bus, Q_to_bus, '1','Q')
        p_error = p_sched - p_control
        q_error = q_sched - q_control
        if abs(p_error) < error_tol and abs(q_error) < error_tol :
            break  # the systesm is now set up correctly
        p_gen = p_gen + p_error
        if p_gen > Pbase:
            p_gen = Pbase        
        q_gen = q_gen + q_error

        count +=1
    print('%3.2f \t%3.2f \t%3.2f \t%3.2f \t%3.2f \t%3.2f' % (p_error, q_error, p_control, q_control, p_gen, q_gen))

answered 2023-08-23 15:18:38 -0600

jconto
2701 ●10 ●30 ●41

To maintain a flow below a level: - Change the dispatch of nearby generation according to their generation shift factor relative to the branch whenever the branch flow is closed to reach its limit.

On higher power levels (Pflow > 50 MW), to maintain a fix flow on a branch: - Add a phase-shifter transformer in series with the branch. or - Add a HVDC line in series with the branch.