Merge pull request #117 from treepleks/PV_divert_ratio

divert_PV_ratio: adjustable requirement on available PV power before starting charge or incrementing current

Author: glynhudson

divert_sim/RapiSender.cpp

@@ -1,6 +1,5 @@
 #include <Arduino.h>
 #include "RapiSender.h"
-#include "debug.h"
 #include "openevse.h"
 #include "input.h"
 
@@ -9,6 +8,7 @@
 #ifdef ENABLE_DEBUG
 #define DBG
 #endif
+#define DBUGF
 
 static CommandItem commandQueueItems[RAPI_MAX_COMMANDS];
 

divert_sim/divert_sim.cpp

@@ -7,11 +7,9 @@
 #endif
 
 #include "Console.h"
-#include "emonesp.h"
 #include "RapiSender.h"
 #include "openevse.h"
 #include "divert.h"
-#include "emonesp.h"
 #include "event.h"
 
 #include "parser.hpp"
@@ -25,6 +23,7 @@ long pilot = 32;                      // OpenEVSE Pilot Setting
 long state = OPENEVSE_STATE_SLEEPING; // OpenEVSE State
 String mqtt_solar = "";
 String mqtt_grid_ie = "";
+uint32_t flags;
 
 int date_col = 0;
 int grid_ie_col = -1;
@@ -38,8 +37,9 @@ bool kw = false;
 extern double smoothed_available_current;
 double divert_attack_smoothing_factor = 0.4;
 double divert_decay_smoothing_factor = 0.05;
+double divert_PV_ratio = 0.5;
 uint32_t divert_min_charge_time = (10 * 60);
-double voltage = DEFAULT_VOLTAGE;     // Voltage from OpenEVSE or MQTT
+double voltage = 240; // Voltage from OpenEVSE or MQTT
 
 time_t parse_date(const char *dateStr)
 {

src/app_config.cpp

@@ -56,6 +56,7 @@ uint32_t flags;
 String ohm;
 
 // Divert settings
+double divert_PV_ratio;
 double divert_attack_smoothing_factor;
 double divert_decay_smoothing_factor;
 uint32_t divert_min_charge_time;
@@ -109,6 +110,7 @@ ConfigOpt *opts[] =
   new ConfigOptDefenition<String>(ohm, "", "ohm", "o"),
 
 // Divert settings
+  new ConfigOptDefenition<double>(divert_PV_ratio, 1.1, "divert_PV_ratio", "dpr"),
   new ConfigOptDefenition<double>(divert_attack_smoothing_factor, 0.4, "divert_attack_smoothing_factor", "da"),
   new ConfigOptDefenition<double>(divert_decay_smoothing_factor, 0.05, "divert_decay_smoothing_factor", "dd"),
   new ConfigOptDefenition<uint32_t>(divert_min_charge_time, (10 * 60), "divert_min_charge_time", "dt"),

src/app_config.h

@@ -46,6 +46,7 @@ extern String mqtt_announce_topic;
 extern String time_zone;
 
 // Divert settings
+extern double divert_PV_ratio;
 extern double divert_attack_smoothing_factor;
 extern double divert_decay_smoothing_factor;
 extern uint32_t divert_min_charge_time;

src/divert.cpp

@@ -23,10 +23,17 @@
 // Or modulate charge rate based on on excess power (if grid feed (positive import / negative export) is available) i.e. power that would otherwise be exported to the grid is diverted to EVSE.
 // Note: it's Assumed EVSE power is included in grid feed e.g. (charge rate = gen - use - EVSE).
 
-// If EVSE is sleeping charging will not start until solar PV / excess power > min chanrge rate
-// Once charging begins it will not pause even if solaer PV / excess power drops less then minimm charge rate. This avoids wear on the relay and the car
-
-#define GRID_IE_RESERVE_POWER   100.0
+// It's better to never import current from the grid but because of charging current quantification (min value of 6A and change in steps of 1A),
+// it may be better to import a fraction of the charge current and use the next charging level sooner, depending on electricity buying/selling prices.
+// The marginal fraction of current that is required to come from PV is the divert_PV_ratio. The requiring a pure PV charge is obtained by
+// setting divert_PV_ratio to 1.0. This is the best choice when the kWh selling price is the same as the kWh night buying price.  If instead the night tarif
+// is the same as the day tarif, any available current is good to take and divert_PV_ratio optimal setting is close to 0.0. Beyond 1.0, the excess of
+// divert_PV_ratio indicates the amount of power (in kW) that OpenEVSE will try to preserve. A value of 1.1 will start charging only when the
+// PV power - 100 W (reserve) reaches the minimum charging power (reproducing the legacy behavior of OpenEVSE).
+
+// If EVSE is sleeping, charging will start as soon as solar PV / excess power exceeds the divert_PV_ratio fraction of the minimum charging power.
+// Once charging begins it will not pause before a minimum amount of time has passed and this even if solar PV / excess power drops less then minimum charge rate.
+// This avoids wear on the relay and the car.
 
 // Default to normal charging unless set. Divert mode always defaults back to 1 if unit is reset (divertmode not saved in EEPROM)
 byte divertmode = DIVERT_MODE_NORMAL;     // default normal mode
@@ -162,7 +169,7 @@ void divert_update_state()
       if (Igrid_ie < 0)
       {
         // If excess power
-        double reserve = GRID_IE_RESERVE_POWER / voltage;
+        double reserve = (1000.0 * ((divert_PV_ratio > 1.0) ? (divert_PV_ratio - 1.0) : 0.0)) / voltage;
         DBUGVAR(reserve);
         available_current = (-Igrid_ie - reserve);
       }
@@ -184,11 +191,16 @@ void divert_update_state()
     }
     DBUGVAR(available_current);
 
-    double scale = available_current > smoothed_available_current ? divert_attack_smoothing_factor : divert_decay_smoothing_factor;
+    double scale = (available_current > smoothed_available_current ? divert_attack_smoothing_factor : divert_decay_smoothing_factor);
     smoothed_available_current = (available_current * scale) + (smoothed_available_current * (1 - scale));
     DBUGVAR(smoothed_available_current);
 
     charge_rate = (int)floor(available_current);
+    // if the remaining current can be used with a sufficient ratio of PV current in it, use it
+    if ((available_current - charge_rate) > min(1.0, divert_PV_ratio))
+    {
+      charge_rate += 1;
+    }
 
     if(OPENEVSE_STATE_SLEEPING != state) {
       // If we are not sleeping, make sure we are the minimum current
@@ -197,12 +209,13 @@ void divert_update_state()
 
     DBUGVAR(charge_rate);
 
-    if(smoothed_available_current >= min_charge_current)
+    // the smoothed current suffices to ensure a sufficient ratio of PV power
+    if (smoothed_available_current >= (min_charge_current * min(1.0, divert_PV_ratio)))
     {
       // Cap the charge rate at the configured maximum
       charge_rate = min(charge_rate, static_cast<int>(max_charge_current));
 
-      // Change the charge rate is needed
+      // Change the charge rate if needed
       if(current_charge_rate != charge_rate)
       {
         // Set charge rate via RAPI