determine solar inverter maxIncrease based on shaded mppts

src/PowerLimiterSolarInverter.cpp

@@ -18,8 +18,61 @@ uint16_t PowerLimiterSolarInverter::getMaxIncreaseWatts() const
 {
     if (!isEligible()) { return 0; }
 
-    // TODO(schlimmchen): left for the author of the scaling method: @AndreasBoehm
-    return std::min(getConfiguredMaxPowerWatts() - getCurrentOutputAcWatts(), 100);
+    // the maximum increase possible for this inverter
+    int16_t maxTotalIncrease = getConfiguredMaxPowerWatts() - getCurrentOutputAcWatts();
+
+    if (!isProducing()) {
+        // the inverter is not producing, we don't know how much we can increase
+        // TODO(AndreasBoehm): should we increas by only 100W in this case? Or go for the max?
+        return 100; // TODO(AndreasBoehm) or maxTotalIncrease
+    }
+
+    auto pStats = _spInverter->Statistics();
+    std::vector<MpptNum_t> dcMppts = _spInverter->getMppts();
+    size_t dcTotalMppts = dcMppts.size();
+
+    // 98% of the expected power is good enough
+    auto expectedAcPowerPerMppt = (getCurrentLimitWatts() / dcTotalMppts) * 0.98;
+
+    float inverterEfficiencyFactor = pStats->getChannelFieldValue(TYPE_INV, CH0, FLD_EFF);
+
+    // fall back to hoymiles peak efficiency as per datasheet if inverter
+    // is currently not producing (efficiency is zero in that case)
+    inverterEfficiencyFactor = (inverterEfficiencyFactor > 0) ? inverterEfficiencyFactor/100 : 0.967;
+
+    size_t dcNonShadedMppts = 0;
+
+    for (auto& m : dcMppts) {
+        float mpptPowerAC = 0.0;
+        std::vector<ChannelNum_t> mpptChnls = _spInverter->getChannelsDCByMppt(m);
+
+        for (auto& c : mpptChnls) {
+            mpptPowerAC += pStats->getChannelFieldValue(TYPE_DC, c, FLD_PDC) * inverterEfficiencyFactor;
+        }
+
+        if (mpptPowerAC >= expectedAcPowerPerMppt) {
+            dcNonShadedMppts++;
+        }
+    }
+
+    if (dcNonShadedMppts == 0) {
+        // all mppts are shaded, we can't increase the power
+        return 0;
+    }
+
+    if (dcNonShadedMppts == dcTotalMppts) {
+        // no mppt is shaded, we can increase the power by the maximum
+        // TODO(AndreasBoehm): If none of the mppts are shaded we assume that we can increase the power by the maximum. is this correct?
+        return maxTotalIncrease;
+    }
+
+    // maximum increase per mppt, required to calculate how much the non-shaded mppts can increase
+    int16_t maxIncreasePerCMppt = maxTotalIncrease / dcTotalMppts;
+
+    // maximum increase based on the non-shaded mppts
+    int16_t maxIncrease = maxIncreasePerCMppt * dcNonShadedMppts;
+
+    return maxIncrease;
 }
 
 uint16_t PowerLimiterSolarInverter::applyReduction(uint16_t reduction, bool)