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TSUN DCU2000Lite Dynamic Output Limiter 🔋☀️

An intelligent, hardware-friendly control loop for Node-RED and Home Assistant designed to tame the sluggish regulation behavior of TSUN storage systems (SolarCan / DCU2000lite / Gen3 inverters).

This tool emulates a single-phase Shelly Pro EM data protocol and solves the hardware-related oscillation issues of the TSUN meter mode ("Power Consumption") purely through software-based mathematics. It provides soft zero feed-in as well as a stable fixed-value mode.

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🚀 Key Features

• Single-Phase Shelly Emulation: Prevents the well-known DCU firmware summation bug, where the inverter's own solar feed-in is incorrectly added on top of household consumption.

• 2-Minute Step-Level Damping with Post-Trigger Verification: Temporarily freezes the real gross household consumption. After the 2 minutes elapse, the current household consumption is re-fetched via a current state node — short-lived load spikes (e.g. coffee machine, kettle under 2 minutes) are completely ignored, protecting the battery and preventing feed-in overshoot.

• 10W/5W Stepped Slew-Rate Limiter (Ramp): Prevents feed-in power from collapsing when loads suddenly drop. Far from the target, the value glides in 10W steps per second; close to the target (< 40W difference), it switches to 5W steps for a smooth, oscillation-free lock-in.

• 800W Software Clipping: Hard-limits calculations for high-power consumers (e.g. a 3000W stove) at the physical 800W boundary. When the load drops, the ramp immediately starts descending from the 800W edge without dead time.

• Night Offset (+10W): Automatically adds 10 watts to the dashboard slider in fixed-value mode to overcome the TSUN inverter's hardware-side 20W deadband. At night, the battery locks precisely onto the desired target value (tolerance: ~4 watts).

• Adaptive Percentage Hysteresis & 1.0 Hold Logic: The comfort zone adapts proportionally (4%) to the current power level. Once the target is reached, a minimal 1.0 is sent instead of a critical 0.0. This maintains physical counterpressure in load mode and completely eliminates wave-like oscillations.

• Intelligent Mode-Switch Clutch (3 Seconds): When switching between day and night mode, the TSUN is frozen at act_power = 1.0 for 3 seconds. During this time, the internal ramp continuously synchronizes with the actual live value, guaranteeing a smooth, jolt-free transition after the clutch releases.

• Triple Fail-Safe Shield: Catches data gaps during deployment, brief Shelly sensor Wi-Fi dropouts, and unavailable/unknown states of all input sensors. Each sensor (feed-in, slider, household consumption) remembers its last valid value and uses it as a fallback — a hard 0W crash of the TSUN firmware is therefore impossible.

• Jump Filter in HA Template Sensor: The Real-Time Household Consumption sensor in HA filters out drops to below 20% of the last known value — brief sensor outages no longer distort the control loop.

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🛠️ System Architecture in Node-RED

The flow is divided into three physically autonomous lines that communicate conflict-free in the background via memory (flow and global):

1. Line 1 (Intelligent Household Consumption Brake & Peak Filter): Retrieves the current consumption every 2 minutes. Via a switch- and trigger-based branch, values up to 800W pass through immediately. Load peaks above 800W are blocked for 2 minutes. After the timer expires, a current state node re-fetches the then-current value — if the load has since dropped, the lower value is used. Short peaks under two minutes are therefore completely ignored.

2. Line 2 (HTTP Real-Time Poll): Responds every second to the TSUN /rpc/Shelly.GetStatus poll. Calculates the live difference while incorporating the ramp, hysteresis, mode-switch clutch, and all fallbacks.

3. Line 3 (Dashboard Switch): Switches the background logic between dyn (daytime) and fix (nighttime) based on the HA selection list.

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📦 Installation & Setup

1. Preparations in Home Assistant

Under Settings ➡️ Devices & Services ➡️ Helpers, create the following entities:

1. Dropdown (input_select.regelmodus): Options: Dynamic Consumption and Fixed Value
2. Number (input_number.wunsch_einspeisung): Range 0 to 800 (step size 1 or 5), display mode: slider
3. Number (input_number.netz_puffer): Range 0 to 100 (step size 1 or 5), display mode: slider

Also add the following jump filter to your Real-Time Household Consumption template sensor in configuration.yaml:

- name: "Real-Time Household Consumption"
  state: >
    {% set solar = states('sensor.solar_produktion_terrasse_positiv') | float(0) %}
    {% set feed_in = states('sensor.netzeinspeisung_echtzeit') | float(0) %}
    {% set grid = states('sensor.netzbezug_echtzeit') | float(0) %}
    {% set consumption = ((solar + feed_in) + grid) | round(2) %}
    {% set last = this.state | float(0) %}
    {% if last > 50 and consumption < (last * 0.2) %}
      {{ last }}
    {% else %}
      {{ [consumption, 0] | max }}
    {% endif %}

2. Settings in the TSUN App

• Set up your local virtual Shelly meter (c049efc02345).
• In the meter settings, make sure the installation location is set to "Power" (Power Consumption)!
• Logic note: Even though the app refers to it as "Power", the TSUN firmware internally always attempts to regulate the received value toward zero.

3. Node-RED Import

1. Copy the JSON code below.
2. In Node-RED, go to Menu ➡️ Import in the top right corner and paste the text.
3. Open the yellow/orange function Shelly node and enter your exact HA entity names for your inverter power sensor in the first lines.
4. Click Deploy.

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📄 Node-RED Flow (JSON Export)

Click here / Klicke hier

📄 Node-RED Function Shelly (JavaScript)

Click here / Klicke hier

🤝 Contributing & License

This project is open source. If you have optimizations for the control loop (e.g. adjustments for other battery manufacturers connected to the DCU), feel free to create a pull request or open an issue!

License: MIT