What is the impact of unbalanced load on Zero Export for Solar Power Plants
Inverters can only produce equal power on all the 3 phases and due to this restriction from inverter for maximum solar output balance load should be present.
Controllers provides following operating modes to support such cases with implication
Option 1: Average power for all phases: This assumes the load is balance and accordingly set Power output of all inverters.
Option-2: Minimum power on anyone phase-In case of unbalanced load controller can assume minimum power of any one phase and assume same is being produced by other two phases by doing this it ensures there is no export happening on all the 3 phases, but this will also result in low production.
Sample Calculations
P = P1 + P2 + P3
Where P = Total power in the circuit and P1, P2, P3 = Power in each phase
The below chart is divided into three rows, 1 for No-load, 2 for Balance Load,3 for Unbalance Load. Each colum define Power of each Phase
Zero Export in Balance Load Scenario: Inverter produces equal output on all phases.
| S .No | Power in kW-P1 | Power in kW-P2 | Power in kW-P3 | Total Power P = P1+P2+P3 |
|---|---|---|---|---|
| Balance Load | 10 | 10 | 10 | 30 |
| Inverter Produces | 10 | 10 | 10 | 30 |
| Grid Import | 0 | 0 | 0 | 0 |
| Grid Export | 0 | 0 | 0 | 0 |
Zero Export in Unbalanced Load Scenario: Inverter Produces as per minimum load of all the 3 phases to avoid export on any phase.As load is not balanced, remaining power will be imported as per the unbalanced load
| S .No | Power in kW-P1 | Power in kW-P2 | Power in kW-P3 | Total Power P = P1+P2+P3 |
|---|---|---|---|---|
| Unbalanced Load | 15 | 5 | 10 | 30 |
| Inverter Produces | 5 | 5 | 5 | 15 |
| Grid Import | 10 | 0 | 5 | 15 |
| Grid Export | 0 | 0 | 0 | 0 |