Analysis of distributed resources operating in unbalanced distribution circuits

The use of distributed resource (DR) electrical generation in distribution circuits is growing. DR generation comes in many forms including gas turbine driven synchronous generators, wind powered induction generators, fuel cells with inverter circuitry, and others. This work focuses on the operation of DRs in unbalanced distribution circuits. It is shown that a balanced DR, modeled as a voltage source, can cause unbalanced power flows in a distribution circuit with balanced loads. A three-phase model of a synchronous generator operating as a DR is derived. This derivation is used to justify a voltage-dependent current source model of the DR which is then used in subsequent power flow studies. A power flow study is presented where a circuit is operating with no constraint violations. A DR is then switched into the circuit, and following this switching operation, voltage constraint violations occur on some phases.