Grid-Tie Inverter Simulation Desktop App

This is a desktop-app for simulating grid-tied inverters, supporting various topologies, control strategies, DC sources, and grid conditions. It provides a graphical interface for configuring parameters, visualizing waveforms, and performing frequency-domain analysis (Bode plots). The software is designed for modeling inverter behavior under different operating conditions.

Functioning Logic

Main Application (main.c):
- Initializes a GTK application and creates a main window titled "Grid-Tie Inverter Simulator" (800x600 pixels).
- Manages the simulation loop using g_timeout_add (16ms interval, ~60 FPS) to call simulation_update.
- Handles user interactions via signal callbacks for start, pause, reset, and parameter changes (e.g., voltage, frequency, inverter type).
- Resets parameters to defaults and updates GUI elements when the reset button is clicked.
User Interface (interface.c, style.css):
- Features a horizontal layout with a scrollable control panel and a waveform drawing area.
- Control panel includes:
  - Dropdowns: Inverter type (Single-Phase, Three-Phase, NPC, Flying Capacitor, Cascaded H-Bridge), design (Transformerless, Transformer-based), MPPT (None, Perturb & Observe, Incremental Conductance), control (None, PI, PR, SMC, MPC), DC source (PV, Battery, Fuel Cell, Hybrid), and grid condition (Normal, Weak, Faults).
  - Sliders: Voltage (100–300V), frequency (40–60 Hz), phase (0–2π rad), PLL gains (Kp: 0.1–2, Ki: 1–50), and max time step (0.1–10ms).
  - Buttons: Start (toggle), Pause/Resume, Reset, Configure DC, and Frequency/Small-Signal Analysis.
  - Status labels: PLL lock, islanding status, grid condition, DC voltage/current/SoC/power.
- Uses a teal-themed CSS with Fixedsys font, outset/inset borders, and hover/active effects for a retro aesthetic.
DC Source Configuration (GleichstromquellenModellierung.c):
- Provides a separate window for configuring DC source parameters:
  - PV: Irradiance (200–1000 W/m²), temperature (0–50°C), series panels (1–10), parallel strings (1–5).
  - Battery: State of Charge (20–90%), type (Li-ion, Lead-acid), charging state.
  - Fuel Cell: Power demand (0–1000W).
- Updates parameters in real-time and recalculates DC voltage/current when changed.
Frequency Analysis (FrequenzbereichsUndKleinsignalanalyse.c):
- Creates a window for frequency-domain analysis, currently supporting Bode plots.
- Allows configuration of analysis type (Bode only), frequency range (0.01–100k Hz), operating voltage (100–300V), and load resistance (1–1000Ω).
- Draws gain (top half) and phase (bottom half) plots using Cairo on a logarithmic frequency scale.
Simulation Loop (Zeitbereichssimulation.c):
- Manages the simulation by calculating an adaptive time step and updating the inverter state via simulation_step.
- Updates MPPT, PLL, control, islanding detection, and DC source models each step.
- Refreshes GUI labels (PLL lock, islanding status, grid condition, DC parameters) and redraws waveforms.
Waveform Visualization (waveform.c):
- Draws inverter output waveforms (single-phase or three-phase) using Cairo.
- Uses a black background with a white grid (10 vertical, 9 horizontal lines) and colored lines (red for phase A, green for B, blue for C).
- Scales output voltages to ±400V, plotting one sample per pixel over a 1ms time step.

Simulation Logic

Time Step Calculation (calculate_time_step in Zeitbereichssimulation.c):
- Adapts the time step based on:
  - Frequency deviation: |PLL_frequency - 50| / 50
  - Output change: sqrt((output[0] - prev_output[0])^2 + (output[1] - prev_output[1])^2 + (output[2] - prev_output[2])^2)
- Scales time step:
  - 10% of max_dt for large deviations (>5% frequency or >10V output change).
  - 50% of max_dt for moderate deviations (>2% frequency or >5V output change).
  - Clamps between 0.1ms and max_dt (default 10ms, user-configurable).
- Ensures smooth simulation during transients while maintaining performance.
Simulation Step (simulation_step in Zeitbereichssimulation.c):
- Increments simulation time: sim_time = sim_time + dt
- Updates:
  - MPPT (Perturb & Observe or Incremental Conductance) if enabled.
  - PLL (phase, frequency, voltage) if enabled.
  - Control algorithm (PI, PR, SMC, MPC) if enabled.
  - Islanding detection if enabled.
  - DC source (PV, battery, fuel cell, or hybrid).
- Applies updates sequentially to reflect dependencies (e.g., MPPT affects DC voltage, PLL affects phase).
Simulation Update (simulation_update in Zeitbereichssimulation.c):
- Called every 16ms if the simulation is running.
- Calculates adaptive time step, performs simulation_step, and updates GUI:
  - PLL lock: “Locked” if phase error < 0.1 * grid_amplitude * inverter_voltage * sqrt(2), else “Not Locked.”
  - Islanding: “Islanding Detected” or “Grid Connected” based on detection.
  - Grid condition: Reflects user selection (e.g., “Voltage Sag”).
  - DC source: Updates Vdc, Idc, Battery SoC, and Power labels.
- Redraws waveforms via gtk_widget_queue_draw.
- Stops simulation if islanding is detected, resetting start button and pause label.

Physics Models

Inverter Output (inverter.c, Wechselrichtertopologie.c, MehrstufigerWechselrichter.c):
- Single-Phase (single_phase_output):
  - output[0] = V_rms * sqrt(2) * sin(2 * pi * f * t + phase)
  - output[1] = 0, output[2] = 0
- Three-Phase (three_phase_output):
  - output[0] = V_rms * sqrt(2) * sin(2 * pi * f * t + phase)
  - output[1] = V_rms * sqrt(2) * sin(2 * pi * f * t + phase + 2 * pi / 3)
  - output[2] = V_rms * sqrt(2) * sin(2 * pi * f * t + phase + 4 * pi / 3)
- NPC Inverter (npc_inverter_output):
  - Peak voltage: V_peak = V_rms * sqrt(2)
  - Angle: angle = mod(2 * pi * f * t + phase, 2 * pi)
  - Output: -V_peak if angle < pi/3 or >= 5 * pi/3; V_peak if 2 * pi/3 <= angle < 4 * pi/3; else 0
  - output[0] = level, output[1] = 0, output[2] = 0
- Flying Capacitor (flying_capacitor_output):
  - Peak voltage: V_peak = V_rms * sqrt(2)
  - Angle: angle = mod(2 * pi * f * t + phase, 2 * pi)
  - Output: -V_peak if angle < pi/5 or >= 9 * pi/5; -V_peak/2 if angle < 2 * pi/5; V_peak/2 if angle < 4 * pi/5; V_peak if 4 * pi/5 <= angle < 7 * pi/5; else 0
  - output[0] = level, output[1] = 0, output[2] = 0
- Cascaded H-Bridge (cascaded_h_bridge_output):
  - Similar to NPC but applied to three phases with angles: phase, phase + 2 * pi/3, phase + 4 * pi/3
Transformer Effects (TransformatorlosUndTransformatorbasiert.c):
- Transformerless (apply_transformerless):
  - output[i] = output[i] * 0.98 (98% efficiency)
- Transformer-Based (apply_transformer_based):
  - output[i] = output[i] * 1.1 * 0.90 (1.1 turns ratio, 90% efficiency)
DC Sources (GleichstromquellenModellierung.c):
- PV Model (pv_current):
  - Photocurrent: Iph = (Isc + Ki * (T - 25)) * (G / 1000) * Np
    - Isc = 8.21A, Ki = 0.00065 A/°C, Gref = 1000 W/m², Tref = 25°C
  - Thermal voltage: Vt = Ns * n * k * T / q
    - n = 1.3, k = 1.381e-23 J/K, q = 1.602e-19 C
  - Saturation current: Io = Isc / (exp((Voc + Kv * (T - 25)) / Vt) - 1)
    - Voc = 37.6V, Kv = -0.123 V/°C
  - Current (Newton-Raphson, 5 iterations): I = Iph - Io * (exp((V / Ns + I * Rs) / Vt) - 1) - (V / Ns + I * Rs) / Rsh
    - Rs = 0.221Ω, Rsh = 415.405Ω
  - Total current: I * Np
- Battery Model (battery_voltage):
  - Nominal voltage: Vnom = 48V (Li-ion) or 12V (Lead-acid)
  - Efficiency: eta = 0.95 (charging) or 0.98 (discharging) for Li-ion; *0.9 for Lead-acid
  - Open-circuit voltage: V0 = Vnom * (1 + 0.1 * (SoC - 0.5))
  - Internal resistance: R_int = 0.05 * (1 / SoC)
  - Voltage: V = V0 - I * R_int
  - SoC update: dAh = (I * eta if charging else -I / eta) * (dt / 3600), SoC = SoC + dAh / capacity
    - Clamped: 0.2 <= SoC <= 0.9
- Fuel Cell Model (fuel_cell_voltage):
  - Nominal voltage: V0 = 48V
  - Voltage: V = V0 - A * ln(I + 1) - I * R - m * exp(n * I)
    - A = 0.06, R = 0.01Ω, m = 0.05, n = 0.0001
  - Limits I to meet power demand: I = P_demand / V if V * I > P_demand
- Hybrid Model:
  - Fuel cell provides base current: I = P_demand / V
  - Battery supplies additional current: I_extra = control_ref_current - I
  - Voltage from fuel cell or battery based on demand.
Grid Model (GridSimulation.c):
- Grid impedance:
  - Normal: R = 0.4Ω, L = 0.001H
  - Weak: R = 1.0Ω, L = 0.005H
  - Reactance: X = 2 * pi * 50 * L
- Nominal: V_nom = 220V RMS, f_nom = 50 Hz
- Voltage: V_grid = V_nom * fault_factor * sqrt(2) * sin(2 * pi * (f_nom + freq_shift) * t) + harmonic
  - Faults (t = 1–1.5s):
    - Sag: fault_factor = 0.5
    - Swell: fault_factor = 1.2
    - Harmonics: harmonic = 0.05 * sin(3 * 2 * pi * f_nom * t) + 0.03 * sin(5 * 2 * pi * f_nom * t) + 0.02 * sin(7 * 2 * pi * f_nom * t)
    - Frequency Shift: freq_shift = 2 Hz
- PCC voltage: V_pcc = V_grid - I_inverter * R - I_inverter * X * cos(2 * pi * f * t)
- Random disconnection: 5% chance per second after t > 1s.

Algorithms

MPPT Algorithms (MaximaleLeistungspunktverfolgung.c):
- Perturb & Observe (mppt_perturb_observe):
  - Perturbs voltage by delta_v = 1V.
  - If power > prev_power, continue in same direction; else reverse.
  - Updates: mppt_voltage = mppt_voltage ± delta_v, prev_power = V * I, prev_voltage = mppt_voltage
  - Limits: 100V <= mppt_voltage <= 300V
- Incremental Conductance (mppt_incremental_conductance):
  - Calculates: g_inc = delta_i / delta_v, g = I / V
    - delta_i = I - (prev_power / prev_voltage), delta_v = V - prev_voltage
  - If |g_inc + g| < 0.01, at MPP; else if g_inc + g > 0, increase V; else decrease V.
  - Perturbs by delta_v = 1V if delta_v < 0.01.
  - Updates and limits similar to Perturb & Observe.
PLL (Phasenregelkreis.c):
- Simulates grid: V_grid = (220 + sin(0.2 * t) * 10) * sqrt(2) * sin(2 * pi * (50 + sin(0.1 * t)) * t)
- Frequency estimation via zero-crossing:
  - Detects positive zero-crossings, calculates period after two crossings: period = (time - last_zero_cross) / (cross_count - 1)
  - Frequency: f = 1 / period
- Voltage tracking: V_pll = V_pll + 0.1 * (grid_ampl - V_pll) * dt
- Phase detector: error = V_grid * V_inv
- PI controller: phase_correction = Kp * error + Ki * integral, integral = integral + error * dt
- Phase update: pll_phase = mod(pll_phase + phase_correction * dt, 2 * pi)
- Lock status: locked if |error| < 0.1 * grid_ampl * V_inv * sqrt(2)
Control Algorithms (StromUndSpannungsregelung.c):
- Plant Model:
  - V_inv = duty * V_rms * sqrt(2) * sin(2 * pi * f * t + phase)
  - V_grid = V_grid_rms * sqrt(2) * sin(2 * pi * f * t)
  - Current: di/dt = (V_inv - V_grid - R * I) / L, I = I_prev + di/dt * dt
    - R = 10Ω, L = 0.01H, dt = 0.05s
- PI Control:
  - error = I_ref - I_meas, I_ref = I_ref_ampl * sin(2 * pi * f * t + phase)
  - u = Kp * error + Ki * integral, integral = integral + error * dt
  - Kp = 0.1, Ki = 5.0
- PR Control:
  - Adds resonant term: u = Kp * error + Ki * integral + Kr * sin(2 * pi * f * t) * error
  - Kr = 50.0
- SMC (Sliding Mode Control):
  - Sliding surface: s = error + c * (error - prev_error) / dt
  - u = k * (s > 0 ? 1 : -1)
  - c = 0.01, k = 0.5
- MPC (Model Predictive Control):
  - Tests duty cycles (0 to 1, step 0.1) over 2 steps (100ms horizon).
  - Cost: sum((I_ref_future - I_future)^2) for t_future = t + j * dt
  - Selects duty with minimum cost.
- Clamps duty: 0 <= control_output <= 1
Islanding Detection (IslandingDetectionMechanism.c):
- Passive Methods:
  - OUV: Detects if V < 193.6V or V > 242V (0.88–1.1 pu).
  - OUF: Detects if f < 49 Hz or f > 51 Hz.
  - ROCOF: |f - prev_f| / (t - prev_t) > 1 Hz/s.
- Active Method (AFS):
  - Perturbs frequency: f = f + 0.5 * sin(2 * pi * 0.1 * t) if grid connected.
  - Detects islanding if |f - 50| > 0.7 Hz in islanded mode.
Frequency Analysis (FrequenzbereichsUndKleinsignalanalyse.c):
- Models controller: G_controller = Kp + Ki / s
  - Kp = pll_kp (default 0.5), Ki = pll_ki (default 10)
- Models plant: G_plant = 1 / (s * L + R + 1 / (s * C))
  - L = 0.001H, C = 10e-6F, R = analysis_op_load
- Transfer function: G = G_controller * G_plant
- Gain: 20 * log10(|G|) dB
- Phase: arg(G) * 180 / pi degrees
- Evaluates over 1000 points from f_min to f_max (logarithmic).

Equations

Inverter Output:
- Single-Phase: V = V_rms * sqrt(2) * sin(2 * pi * f * t + phase)
- Three-Phase: V_i = V_rms * sqrt(2) * sin(2 * pi * f * t + phase + i * 2 * pi / 3), i = 0,1,2
- NPC/Flying Capacitor: Multi-level outputs based on angle thresholds
- Transformerless: V_out = V_in * 0.98
- Transformer-Based: V_out = V_in * 1.1 * 0.90
PV Model:
- Iph = (8.21 + 0.00065 * (T - 25)) * (G / 1000) * Np
- Vt = Ns * 1.3 * 1.381e-23 * T / 1.602e-19
- Io = 8.21 / (exp((37.6 - 0.123 * (T - 25)) / Vt) - 1)
- I = Iph - Io * (exp((V / Ns + I * 0.221) / Vt) - 1) - (V / Ns + I * 0.221) / 415.405
Battery Model:
- V0 = Vnom * (1 + 0.1 * (SoC - 0.5))
- R_int = 0.05 * (1 / SoC)
- V = V0 - I * R_int
- dAh = (I * eta if charging else -I / eta) * (dt / 3600), SoC = SoC + dAh / capacity
Fuel Cell Model:
- V = 48 - 0.06 * ln(I + 1) - I * 0.01 - 0.05 * exp(0.0001 * I)
- I = P_demand / V if V * I > P_demand
Grid Model:
- V_grid = V_nom * fault_factor * sqrt(2) * sin(2 * pi * (f_nom + freq_shift) * t) + harmonic
- V_pcc = V_grid - I_inverter * R - I_inverter * X * cos(2 * pi * f * t)
PLL:
- error = V_grid * V_inv
- phase_correction = Kp * error + Ki * integral
- pll_phase = mod(pll_phase + phase_correction * dt, 2 * pi)
- V_pll = V_pll + 0.1 * (grid_ampl - V_pll) * dt
Control:
- Plant: di/dt = (V_inv - V_grid - R * I) / L, I = I_prev + di/dt * dt
- PI: u = Kp * error + Ki * integral
- PR: u = Kp * error + Ki * integral + Kr * sin(2 * pi * f * t) * error
- SMC: s = error + c * (error - prev_error) / dt, u = k * (s > 0 ? 1 : -1)
- MPC: cost = sum((I_ref_future - I_future)^2), select min cost duty
Frequency Analysis:
- G = (Kp + Ki / s) * (1 / (s * L + R + 1 / (s * C)))
- Gain = 20 * log10(|G|)
- Phase = arg(G) * 180 / pi

Screenshots

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