Comparison of PV panels MPPT techniques applied to solar water pumping system

Received Apr 13, 2021 Revised Jul 1, 2021 Accepted Jul 12, 2021 This paper deals with an advanced design for a pump powered by solar energyto supply agricultural lands with water and also the maximum power point is used to extract the maximum value of the energy available inside the solar panels and comparing between techniques MPPT such as Incremental conductance, perturb & observe, fractional short current circuit, and fractional open voltage circuit to find the best technique among these. The solar system is designed with main parts: photovoltaic (PV) panel, direct current/direct current (DC/DC) converter, inverter, filter, and in addition, the battery is used to save energy in the event that there is an increased demand for energy and not to provide solar radiation, as well as saving energy in the case of generation more than demand. This work was done using the matrix laboratory (MATLAB) simulink program.


INTRODUCTION
Solar energy is one of the available renewable energy resources that can provide us with steady, reliable power [1]. However, because sunlight does not need any kind of fuel, solar energy can be used directly to create electricity. No gases or poisons are emitted into the air. Solar power systems need minimal maintenance. Solar modules have a service life of 25 years without lubrication or maintenance. Using solar energy does have one drawback, however: It is expensive. As long as the sun doesn't shine for 24 hours a day, the solution involves the combination of a photovoltaic system and a battery. It is useful in nearly any place, particularly if there is sunlight and access to clean water. When a user of a solar water application opens a faucet, water is applied to the tank from above [2]- [4]. Figure 1 depicts the daily supply of solar water.
PV systems frameworks are being used more to increase their energy-efficiency by using PV systems. But due to the low module efficiency, there is still a device capacity problem in photovoltaic systems [4]. As a result, matching the maximum electrical output to a photovoltaic device requires careful evaluation of its constituents. Placing only requires choosing the best PV modules and implementing an efficien maximum power point tracking (MPPT) algorithm.
In literature, a multitude of MPPT schemes for solar PV systems have been presented in books and journal articles. Many techniques vary in difficulty, hardware, popularity, and availability, among other variables. An approach which has found broad acceptance in PV tracking is based on this technique, but not limited to, perturbation & observation (P&O) (which is the most known), the incremental conductance (INC),  [7]. In this work, the emphasis will be on design and simulation of solar water pumping systems and comparison study between widely applied MPPT techniques, while considering weather conditions will be on assessing which method is the most capable of shifting resource patterns in short order.  Figure 2 shows the main block diagram of the proposed stand-alone system. The first block is represented by photovoltaic solar panels. The voltage and current that gets sent to the output of the MPPT controller will be measured by a sensing circuit. A boost converter DC/DC power electronic switch uses pulse width modulation (PWM) to vary its duty cycle. The battery is still charged, which means the rest of the blocks are represented by PWM. The inverter output voltage will be sensed by sensing circuit that to be used for modulation index control to stabilize the inverter alternating current (AC) voltage level [8], [9].

Photovoltaic generator model
When there is low electricity production from PV cells. As a result, the cells should be laid out in a parallel-serial fashion, where the energy is created in several modules. A photovoltaic panel is composed of series and parallel modules. The PV panel design begins with selecting CS6P-250P solar cell type Monocrystalline Maxeon Gen II PV modules. Table 1 also includes a summary of the spectifications of the PV panel parameters. PV panels will be used in this project, which will include 80 panels (total capacity is 20 Kw). These panels are organized into eight parallel lines, each of which contains ten serially linked panels 1815 [10]. Figure 3 shows solar cellsequivalent circuit in -series and -parallel is shown in and the formula for their and [11], [12]: where , is light-generated current; cell reverse saturation current; A is ideality factor (=1); T is cell temperature (in Celsius); K is Boltzmann's constant (= 1.3805 × 10 −23 N m/K); q is electronic charge (=1.6×10 −19 C); and is the series and parallel resistance respectively, is the solar shortcircuit current. To learn more about the differences in the impact of different irradiation levels on the P-V and I-V characteristics, see Figure 4 and Figure 5.

Boost converter model
By interposing a power converter (DC-DC converter) between the photovoltaic generator and the load (battery), the MPPT can be achieved. By acting on the converter duty cycle (D), the operation point can be guaranteed to be the MPPT. It uses step-up methodology. The voltage the sensor produces is larger than the voltage that is fed into it. The circuit shown in Figure 6 has an inductor, a capacitor, a switch, and a diode [14]. When the switch is closed, the diode tends to be reverse biased and the current increases through the inductor. When the switch is switched off, the diode tends to be forward biased, the inductive voltage stored in the capacitor is discharged, and the current is allowed to flow through the inductance. Once the voltage has been increased, it is routed to the load. The duty cycle is calculated using the values of the input and output voltages specified in the (2).

MPPT techniques
The MPPT control is a key component of the PV system. It is critical to optimal system operation. This control approach is derived from the principle of optimal variation of the cyclic ratio D, and we will present and explain later the most popular control techniques. There are a number of common and practical models for estimating how much a PV power will increase with altitude, including perturb & observe, incremental conductance, and fractional short current circuit and fractional open voltage circuit [15], [16].

Perturb and observe (P&O) technique
This technique is widely used for tracking the maximum power due to its simple design. This method adjusts the PV module voltage and compares the new power output with that of the previous perturbation cycle in order to see if it has returned to normal. On the same principle as shown in Figure 7, the PV module voltage shifts the control system in this direction if the PV output voltage rises, and the power is limited if it doesn't [17], [18].

Incremental conductance (IC) MPPT technique
Incremental conductance technique employs an array terminal voltage that is based on the MPPT voltage. Here is the diagram for this technique in Figure 8. The general form of this technique is this [19], [20]. at MPPT (8) at the left of MPPT (9) at the right of MPPT (10)

Technique fractional open circuit voltage (FVOC) technique
This technique is based on the nearly linear relationship between the open circuit voltage VOC and the photovoltaic panel's optimal voltage VMPP [21]- [23]. The relationship between V OC and V MPP is given by the (11). (11) where Kv the coefficient of between between 0.71 and 0.8 varies. The flowchart in Figure 9 illustrates the FVOC technique.

Fractional short circuit current (FSCC) technique
This technique is linear in response and there is almost a direct correlation between the optimum I MPP and the short circuit current I SC change of the PV in different atmospheric conditions [24], [25]. The relation between I MPP and Isc is given by the (12): (12) where is the coefficient of between 0.78 and 0.92 varies. The flowchart in Figure 10 illustrates the FSCC technique.

RESULTS AND DISCUSSION
As illustrated in Figure 11, the considered photovoltaic system generates 20 kW and is designed, simulated, and implemented. This system is divided into six stages. The first stage is a photovoltaic array with 80 panels, the second stage is a boost converter DC/DC, and the inverter (3-level single-phase bridge, H voltage source). The fourth stage includes a passive LCL (LPF) filter connected to the main off-grid fifth dynamic load circuit, and the final stage is a battery. Figure 11. The simulation of PV system Table 2 show MPPT controller at fixed temperatures (T) with range of irradiance (G), while Table 3 show MPPT controller at different temperatures (T) with fixed irradiance (G). Figures 12 (a)-(d) and Figure  13 (a)-(d)illustrate the step response of power for various MPPT techniques at different temperatures (T) 25°, irradiance (G) 1000 W/ 2 and temperature (T) 15°, irradiance (G) 600 W/ 2 , respectively. Table 4 and Table 5 show comparison between the four MPPT techniques after take 10 (sec) of time operation temperature (T) 25°, irradiance (G) 1000 W/ 2 and temperature (T) 15°, Irradiance (G) 600 W/ 2 , respectively, mention overshoot, undershoot, rise time and setting time.

CONCLUSION
This study also includes the design and simulation of a 20-kW photovoltaic-powered pump that uses simple methods, such as PVP. In summary, the results can be stated is being as: The best oscillation in P&O MPPT technique; the best rise time, settling time in Fractional voltage current circuit (open, short) MPPT; At T=15°, G=600 W/ 2 the Incremental conductance MPPT best performance in settling time.