FIELD OF THE INVENTION

The present invention relates to a system and a method for operating solar pumping system, more particularly, to the solar pumping system and the method for operating solar pumping system without tripping the solar pump.

BACKGROUND OF THE INVENTION

With the recent advancement in harvesting of power through solar energy, various systems have been developed to operate the AC load from a DC source by using a converter. However, with the conversion of DC power to operate AC load, various issues are predominant such as insufficient supply of power.

In addition, the voltage derived from the solar panel is highly variable due to the long and short term variations of solar energy incident on the panel, and the electric energy generated from solar cells has different electrical characteristics from those of the traditionally electric energy as the later one has the linear voltage source characteristics which maintain a constant voltage to obtain desired operation conditions irrespective of the load conditions.

One of the leading applications of the solar power is to operate solar pumps, which generally include three phase AC motors. The load curve of the AC pump motor shifts with varying conditions, e.g. water depth, and therefore, it can be difficult to operate an AC pump motor efficiently from solar panels. The controlling of AC motors at fixed frequency is very difficult and requires power to remain constant at a given frequency, because, a change in DC voltage must be accompanied by a change in DC current.

The Variable Frequency Drive (VFD) for solar pumping application is used to control the electric motor by varying frequency and voltage supplied for efficient operation. Frequency (or hertz) is directly related to the motor's speed. In other words, the higher the frequency, the faster the revolutions per minute (RPM) of the motor thereby pumping maximum water. If an application does not require an electric motor to run at full speed, the VFD can be used to ramp down the frequency and voltage to meet the requirements of the electric motor's load which reduces the energy costs.

Further, VFD for solar pumping application are found successful for 415V AC pump motor, but it faces technical issue or failure when it is applied to 220V AC pump motor as the VFD drive trips on over voltage when the DC supply from solar cell modules crosses 390V or 395V as these VFD are designed for industrial applications where DC supply rarely goes beyond 380V.

Therefore, the object of the present invention is to solve one or more of the aforesaid issue.

SUMMARY OF THE INVENTION

Before the present invention and its component are described, it is to be understood that this disclosure is not limited to the particular system and its arrangement as described, as there may be multiple possible embodiments which are not expressly illustrated in the present disclosure. It is also to be understood that the terminology used in the description is for the purpose of describing the particular embodiments only, and it is not intended to limit the scope of the claimed subject matter.

In one embodiment, a solar pumping system is provided where the system comprises plurality of solar modules, at least one switching device connected to the solar modules, at least one VFD connected to the switching device, at least one convertor connected to the solar modules and the VFD, at least one circuit breaker connected with the solar modules and the VFD; at least one diode bridge connected with the negative side of the solar modules and the VFD; and at least one AC motor connected to the output supply of the VFD. The switching device is used to control the supply of DC power transmitted to the VFD based on the input received from the controller of the VFD regarding variation in the voltage and the load requirement of the AC motor. The switching device is controlled by the controller of the VFD to provide appropriate voltage to the AC motor where the controller is configured first to operate the switching device to provide 90% of voltage to the AC motor initially and thereafter, when the DC voltage dips due to load, full voltage is provided. In accordance to the invention the initial voltage provided to the VFD to operate, preferably at 90% of full voltage.

In another embodiment, a method for operating solar pumping system is described. The method comprises the steps of controlling the supply of voltage output of solar module through the switching device so as to provide adequate power to the solar pump based on the requirement of the AC motor in order to avoid tripping by increasing or decreasing the voltage output of the solar modules to a predetermined fraction of voltage for a predetermined fraction of time.

