Untitled

function duty = mppt_po(Vpv, Ipv)
% Simple P&O MPPT for Simulink MATLAB Function block
% Call rate: Ts_mppt (e.g., 0.02 s)
persistent V_prev I_prev P_prev step sign
if isempty(V_prev)
    V_prev = 0;
        I_prev = 0;
            P_prev = 0;
                step = 0.5;   % perturbation in volts (tune 0.2-1.0)
                    sign = 1;     % +1 means increase V, -1 decrease
                    end

                    % Current measurements
                    P = Vpv * Ipv;

                    % If first valid measurement, just set previous and return nominal duty
                    if V_prev == 0
                        V_prev = Vpv; I_prev = Ipv; P_prev = P;
                            duty = 0.5; % initial guess
                                return
                                end

                                % Decision logic (P&O)
                                if P > P_prev
                                    % power increased: keep direction
                                        if Vpv > V_prev
                                                sign = 1;
                                                    else
                                                            sign = -1;
                                                                end
                                                                else
                                                                    % power decreased: reverse direction
                                                                        sign = -sign;
                                                                        end

                                                                        % update reference voltage
                                                                        V_ref = Vpv + sign*step;

                                                                        % Simple mapping V_ref -> duty (assuming boost converter)
                                                                        % Duty = 1 - (Vpv / V_ref) (not exact; use closed-loop to control)
                                                                        % Use PI/clip mapping to keep duty in [0.01,0.99]
                                                                        duty = 1 - (Vpv / max(V_ref, 0.1));
                                                                        duty = max(0.01, min(0.99, duty));

                                                                        % update history
                                                                        V_prev = Vpv;
                                                                        I_prev = Ipv;
                                                                        P_prev = P;
                                                                        end