Develop fix voltage violation detection (#1173)

* Update gridlabd-version
* Fix missing voltage_fluctuation_threshold global in powerflow
* Fixes to variable names
* Fix voltage violation logic
* Add hosting capacity documentation
* Add DER_violation_test global
* Fix child node voltage fluctuation test
* Update node.cpp

module/powerflow/node.cpp

@@ -3552,28 +3552,28 @@ EXPORT TIMESTAMP commit_node(OBJECT *obj, TIMESTAMP t1, TIMESTAMP t2)
 		{
 			pNode->add_violation(VF_VOLTAGE,"%s phase A voltage %.1f V is above %.1f%% violation threshold", pNode->oclass->name, pNode->voltage[0].Mag(), pNode->overvoltage_violation_threshold*100);
 		}
-		if ( pNode->has_phase(PHASE_A) && (pNode->voltage[0].Mag()-pNode->nominal_voltage)/pNode->nominal_voltage < -pNode->undervoltage_violation_threshold )
+		if ( pNode->has_phase(PHASE_A) && (pNode->voltage[0].Mag()-pNode->nominal_voltage)/pNode->nominal_voltage < pNode->undervoltage_violation_threshold )
 		{
 			pNode->add_violation(VF_VOLTAGE,"%s phase A voltage %.1f V is below %.1f%% violation threshold", pNode->oclass->name, pNode->voltage[0].Mag(), pNode->undervoltage_violation_threshold*100);
 		}
 		if ( pNode->has_phase(PHASE_B) && (pNode->voltage[1].Mag()-pNode->nominal_voltage)/pNode->nominal_voltage > pNode->overvoltage_violation_threshold )
 		{
 			pNode->add_violation(VF_VOLTAGE,"%s phase B voltage %.1f V is above %.1f%% violation threshold", pNode->oclass->name, pNode->voltage[1].Mag(), pNode->overvoltage_violation_threshold*100);
 		}
-		if ( pNode->has_phase(PHASE_B) && (pNode->voltage[1].Mag()-pNode->nominal_voltage)/pNode->nominal_voltage < -pNode->undervoltage_violation_threshold )
+		if ( pNode->has_phase(PHASE_B) && (pNode->voltage[1].Mag()-pNode->nominal_voltage)/pNode->nominal_voltage < pNode->undervoltage_violation_threshold )
 		{
 			pNode->add_violation(VF_VOLTAGE,"%s phase B voltage %.1f V is below %.1f%% violation threshold", pNode->oclass->name, pNode->voltage[1].Mag(), pNode->undervoltage_violation_threshold*100);
 		}
 		if ( pNode->has_phase(PHASE_C) && (pNode->voltage[2].Mag()-pNode->nominal_voltage)/pNode->nominal_voltage > pNode->overvoltage_violation_threshold )
 		{
 			pNode->add_violation(VF_VOLTAGE,"%s phase C voltage %.1f V is above %.1f%% violation threshold", pNode->oclass->name, pNode->voltage[2].Mag(), pNode->overvoltage_violation_threshold*100);
 		}
-		if ( pNode->has_phase(PHASE_C) && (pNode->voltage[2].Mag()-pNode->nominal_voltage)/pNode->nominal_voltage < -pNode->undervoltage_violation_threshold )
+		if ( pNode->has_phase(PHASE_C) && (pNode->voltage[2].Mag()-pNode->nominal_voltage)/pNode->nominal_voltage < pNode->undervoltage_violation_threshold )
 		{
 			pNode->add_violation(VF_VOLTAGE,"%s phase C voltage %.1f V is below %.1f%% violation threshold", pNode->oclass->name, pNode->voltage[2].Mag(), pNode->undervoltage_violation_threshold*100);
 		}
 	}
-	else
+	else if ( pNode->voltage_violation_threshold > 0.0 )
 	{
 		if ( pNode->has_phase(PHASE_A) && fabs(pNode->voltage[0].Mag()-pNode->nominal_voltage)/pNode->nominal_voltage > pNode->voltage_violation_threshold )
 		{