Switching to 1500 V DC System Voltages in Solar Power Plants: A Technical Review
lubi solar       May 6, 2019
The solar industry has become increasingly competitive over the years. It has become imperative to chase optimization across all units of a solar power plant.
The industry has seen significant research to develop better technologies on the input side that can help improve the system performance and possibly push the costs down. One of the areas under test, is the system voltage of a solar power plant. The industry has moved from systems designs which used 600 VDC to 1000 VDC, with significant improvement in performance along with a downward push on the prices of the overall system.
Considering the benefits realized with the upward push of the system voltages and recent technical developments in the products like inverters, industry has been demanding a vertical push towards 1500 V DC system voltages.
Considering the modernization of equipment, this shift may seem logical and natural. The decision however has to weighed thoughtfully for its advantages and disadvantages. Let us just have a glance at the advantages and disadvantages.
The advantages of using a 1500 V DC system voltage are as listed:
1: Decreased cable losses in transmission: Of the total DC power generated, some power is lost in the form of I2R losses in transmission through DC cables. By increasing the voltage of the system, the current flowing through the cable decreases to the corresponding power value. This reduces the value of the I2R, thereby decreasing the losses in transmission.
2: Reduced cost of equipments: Considering the mean voltage rating of typical solar modules to be around 36-37 V, it can be inferred that to attain a 1500V DC a larger number of panels have to be connected in series. This results in reduction in capital equipments installations like module mounting structures, DC combiner boxes, and array cables. The decreased array cable length also contributes eventually to decrease in the cable losses which is directly proportional to the cable length.
The disadvantages of the using 1500 V DC system voltage in plant design are as listed:
1: Higher system voltages accelarates the potential induced degradation (PID) of solar modules. It has been observed that PID is primarily affected by system voltage. However now, PID resistant raw material have become commercially available and can be utilized to mitigate the effects in the long run.
2: Highet O&M costs: Higher system volatges generally put the equipments under higher electrical stress, thereby requiring preventive maintainance, some times pushing the costs higher.