Volt/var/THD control in distribution networks considering reactive power capability of solar energy conversion

• The paper presents novel method for optimal volt/var/THD control in presence of PVs.
• Considers PVs’ inverter var capability as well as its harmonic distortion.
• New time-intervals based on load demand and PVs active power curves is introduced.
• Presents a new substation capacitors dispatch to satisfy operational constraint.
• Uses a hybrid joint programing method for precise calculations.

Voltage and reactive power (volt/var) control have been widely employed to reduce power losses and satisfy the main distribution system operational constraints. In the proposed volt/var/THD control the reactive power capability from PV solar is considered as additional control variable in presence of non-linear loads. So, the limitations on deliverable power for each operation point affect inverter reactive power scheduling. Therefore, the main aim is to find proper dispatch schedules for the substation capacitors (SCs), along feeder capacitors (FCs), on-load tap changer (OLTC) tap positions, and photovoltaic systems (PVs) inverter reactive power considering power quality constraints. In order to reduce effect of uncertainty in the forecast plan and to reduce switching operations for OLTC, a new load and generation time-interval division (over 24-h period) is introduced based on both load curve and solar power output curve. Optimization problem is formulated for minimizing fuzzy membership functions values based on a multi-objective genetic algorithm solution method. For improving the search ability by multi-objective approach a method which guarantees the suppression of maximum allowable daily SCs switching and effectively corrects the convergence process is utilized. For more practical application of the proposed method, simulation is carried out in the large distorted distribution system with a number of non-linear loads and solar energy generation system.