Guerrero watt: fast from the monitoring data to find the shadow of failure

Now install photovoltaic power station monitoring system is almost become a standard, a monitoring system, can not only understand the operation of photovoltaic power station in anytime and anywhere, but also from the monitoring parameters and operation in the graph, there may be a problem, find the system to determine the type of fault, so as to solve the problem quickly, reduce the loss. Dark shade is one of the most common fault photovoltaic system, and dynamic shadows shade doesn't always have, want to look at the scene for a long time to see, but from the monitoring parameters can also be found in the law.

due to clouds, trees, buildings, and the impact of birds excrement, pv array by local shadow screening, photovoltaic modules at this time of received light intensity changes, the inverter output power reduction.

shadow shadow is divided into subjective and objective, subjective shadow and shadows can be divided into dynamic and static shadow, objective shadow refers to because of the weather reason caused by the light intensity is abate, such as fog, rain and snow weather, subjective shadow is caused by a nearby obstacles blocking the sun and shadow, subjective static shadow especially covering on the surface of the components, such as bird droppings, leaves, dirt, snow, etc. Subjective dynamic shadows is generalized & other; Shadow & throughout; , it consists of a photovoltaic system around tall buildings, smokestack, trees, telephone poles, or square front row, shape changes along with the movement of the sun, at noon when the sun did not commonly, in the morning or evening.

crystalline silicon components are composed of 60 or 72 cell, usually 20 or 24 cell constitute a string, each string has a bypass diode, when there was a local shelter or damaged components, from power generation unit to unit power consumption, produce hot spot effect, resistance increases, the diode voltage rise at both ends and conduction, allowing other components produced by the current, system continue to generate electricity.

when shadows shade the area is not large, the bypass diode conduction, group's working voltage rise slightly, reduce the large current, power down to 80% above.

　　（ 1) Shadows at the beginning, is generally the voltage rise, fall again, current down first, then rise, set of string I - V curve shows bimodal or multimodal.

　　（ 2) Square power decrease, the time regularly, when it is sunny, and the sunlight intensity, the greater the power declined more; 2 it is every time and recovery time.

according to the principle of the circuit in series, when there is shadow shade of square matrix has a component, the MPPT circuit power will be affected, therefore in the process of photovoltaic power station site selection and design, choose more gentle terrain area, and avoid the large gradient slope to decorate a photovoltaic modules, ensure that keep the appropriate line spacing between components, to avoid tall buildings, pole or tree shadows are formed of photovoltaic modules.

if you can't avoid, to have the shadow of shade components installed in the same group of string, as far as possible the same MPPT, avoid other square matrix to be affected.

if the environment is complex, try to choose MPPT because many inverter, because each MPPT circuit are separate tracking, will not affect other circuits.