From 1d6ab6b67bc1d77777ea834c4c6151cd81ee7682 Mon Sep 17 00:00:00 2001
From: andig <andi@evcc.io>
Date: Mon, 29 Dec 2025 17:37:07 +0100
Subject: [PATCH] HEMS: add FNN 3-relay (experimental) (#25851)

---
 hems/fnn/fnn-3.go | 140 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 140 insertions(+)
 create mode 100644 hems/fnn/fnn-3.go

diff --git a/hems/fnn/fnn-3.go b/hems/fnn/fnn-3.go
new file mode 100644
index 000000000..21424bcd1
--- /dev/null
+++ b/hems/fnn/fnn-3.go
@@ -0,0 +1,140 @@
+package fnn
+
+import (
+	"context"
+	"errors"
+	"time"
+
+	"github.com/evcc-io/evcc/api"
+	"github.com/evcc-io/evcc/core/circuit"
+	"github.com/evcc-io/evcc/core/site"
+	"github.com/evcc-io/evcc/hems/shared"
+	"github.com/evcc-io/evcc/plugin"
+	"github.com/evcc-io/evcc/util"
+)
+
+type Fnn3 struct {
+	log        *util.Logger
+	root       api.Circuit
+	s1, s2, w3 func() (bool, error)
+	maxPower   float64
+	interval   time.Duration
+}
+
+// NewFromConfig creates an Fnn3 HEMS from generic config
+func NewFromConfig(ctx context.Context, other map[string]any, site site.API) (*Fnn3, error) {
+	cc := struct {
+		MaxPower float64
+		S1       plugin.Config
+		S2       plugin.Config
+		W3       plugin.Config
+		Interval time.Duration
+	}{
+		Interval: 10 * time.Second,
+	}
+
+	if err := util.DecodeOther(other, &cc); err != nil {
+		return nil, err
+	}
+
+	// get root circuit
+	root := circuit.Root()
+	if root == nil {
+		return nil, errors.New("hems requires load management- please configure root circuit")
+	}
+
+	// register LPP circuit if not already registered
+	lpp, err := shared.GetOrCreateCircuit("lpp", "fnn-3")
+	if err != nil {
+		return nil, err
+	}
+
+	// wrap old root with new pc parent
+	if err := root.Wrap(lpp); err != nil {
+		return nil, err
+	}
+	site.SetCircuit(lpp)
+
+	// s1 getter
+	s1G, err := cc.S1.BoolGetter(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	s2G, err := cc.S2.BoolGetter(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	w3G, err := cc.W3.BoolGetter(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	return NewFnn3(lpp, s1G, s2G, w3G, cc.MaxPower, cc.Interval)
+}
+
+// NewFnn3 creates Fnn3 HEMS
+func NewFnn3(root api.Circuit, s1, s2, w3 func() (bool, error), maxPower float64, interval time.Duration) (*Fnn3, error) {
+	c := &Fnn3{
+		log:      util.NewLogger("fnn3"),
+		root:     root,
+		maxPower: maxPower,
+		s1:       s1,
+		s2:       s2,
+		w3:       w3,
+		interval: interval,
+	}
+
+	return c, nil
+}
+
+func (c *Fnn3) Run() {
+	for range time.Tick(c.interval) {
+		if err := c.run(); err != nil {
+			c.log.ERROR.Println(err)
+		}
+	}
+}
+
+func (c *Fnn3) run() error {
+	w3, err := c.w3()
+	if err != nil {
+		return err
+	}
+
+	if w3 {
+		// 0%
+		return c.curtail(0.0)
+	}
+
+	s2, err := c.s2()
+	if err != nil {
+		return err
+	}
+
+	if s2 {
+		// 30%
+		return c.curtail(0.3)
+	}
+
+	s1, err := c.s1()
+	if err != nil {
+		return err
+	}
+
+	if s1 {
+		// 60%
+		return c.curtail(0.6)
+	}
+
+	// 100%
+	return c.curtail(1.0)
+}
+
+func (c *Fnn3) curtail(frac float64) error {
+	c.root.Curtail(frac < 1.0)
+	// TODO make ProductionNominalMax configurable (Site kWp)
+	// c.root.SetMaxPower(c.maxPower*frac)
+	return nil
+}