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This paper develops and discusses an improved MPPT approach for temperature variation with fast-tracking speed and reduced steady-state oscillation. This MPPT approach can be added to numerous existing MPPT algorithms in order to enhance their tracking accuracy and response time and to reduce the power loss. The improved MPPT method is fast and accurate to follow the maximum power point under critical temperature conditions without increasing the implementation complexity. The simulation results under different scenarios of temperature and insolation were presented to validate the advantages of the proposed method in terms of tracking efficiency and reduction of power loss at dynamic and steady-state conditions. The simulation results obtained when the proposed MPPT technique was added to different MPPT techniques, namely, perturb and observe (P&O), incremental conductance (INC), and modified MPP-Locus method, show significant enhancements of the MPP tracking performances, where the average efficiency of the conventional P&O, INC, and modified MPP-Locus MPPT methods under all scenarios is presented, respectively, as 98.85%, 98.80%, and 98.81%, whereas the average efficiency of the improved P&O, INC, and modified MPP-Locus MPPT methods is 99.18%, 99.06%, and 99.12%, respectively. Furthermore, the convergence time enhancement of the improved approaches over the conventional P&O, INC, and modified MPP-Locus methods is 2.06, 5.25, and 2.57 milliseconds, respectively; besides, the steady-state power oscillations of the conventional P&O, INC, and modified MPP-Locus MPPT methods are 2, 1, and 0.6 watts, but it is neglected in the case of using the improved approaches. In this study, the MATLAB/Simulink software package was selected for the implementation of the whole PV system.

The demand for electric energy has been increasing in recent years; in this sense, there are many sources to produce it, but there are also constraints related to its production, such as the effect of pollution and warming global climate. These constraints lead research towards the development of renewable and nonpolluting energy sources. Photovoltaic solar energy is certainly one of the most adequate sources of renewable energy [

In conclusion, when the performance of the PV cell degrades with the increase of the temperature, the power extracted from the PV cell degrades too, and the temperature variations leading to maximum power point (MPP) change. Thus, the temperature impact can be reduced by the exploitation of the maximum power available from the PV cell.

Extracting the maximum power requires a tracking mechanism of this point called MPP tracking (MPPT) [

Faster and more accurate MPPT algorithms, such as Beta algorithm [

In the all-existing classical and modern MPPTs, strategies rarely take into account the temperature variation effect, which limits their performance and reduces the global efficiency of the PV system. Many control calculations use temperature as an analysis parameter to recognize MPPT. For example, the authors in Ref. [

To deal with this problem, a novel MPPT approach is suggested in this paper, which can be easily added to many MPPT algorithms in order to improve their MPP tracking efficiency in various climatic conditions, especially under temperature variation as explained and discussed in our previous published work [

In this context, this paper is an extension of the previous work, in which the proposed MPPT approach has been successfully added to three MPPT algorithms, namely, P&O, INC, and modified MPP-Locus method in [

The remaining of the paper is as follows. Section

The PV generator consists of numerous solar cells, where the solar cell or PV cell is a device that converts the light energy into electrical energy based on the principles of the photovoltaic effect. The PV cell performance is highly dependent on temperature changes. The latter will affect the power energy generated from the PV solar cells, and the PV voltage is highly dependent on the temperature; an increase in temperature will decrease significantly the PV cell open-circuit voltage [

Figure

PV module output characteristics with different temperature variability effects and under different solar radiation levels: (a)

The PV cell short-circuit current (

With increasing temperature, PV current increases slightly, but PV open-circuit voltage (

Figure

Maximum power variations with temperature changes under different radiation levels.

The role of several MPPT techniques suggested till date is to regulate the duty ratio (

Schematic diagram of the complete PV system.

Thanks to its simplicity, ease of implementation, and low cost, perturb and observe (P&O) MPPT technique is the most widely used in the commercial PV system. Its principle is based on the PV voltage perturbation regarding the comparison of the extracted PV power [

Figure

Tracking issues in the

Flowchart of the basic perturb and observe (P&O) tactic.

The incremental conductance (INC) algorithm’s principle to track the real MPP is based on the slope

The maximum output power

This leads to

Therefore, by evaluating the derivative, one can test whether the PV generator is operating at near MPP or far away from it:

Thus, the MPP can be reached by comparing the actual conductance

Flowchart of the basic INC algorithm.

The flowchart of this method is represented in Figure

Flowchart of the modified MPPT method based on the MPP-Locus technique.

Operating point resulted by a PV module connected with a DC-DC converter.

A PV module consists of numbers of solar cells connected in series or parallel, and the total power generated is the sum of the power contributed by all of the individual solar cells. A DC-DC converter is connected in between the PV module and the load, as shown in Figure

Schematic diagram of the complete PV system.

The relationships of the voltage and current of the DC-DC converter between the input and output sides are shown in

where

Divide (

In a PV system, Equation (

where

Equation (17) can be defined at the instant (

The relationship of the duty cycle of the boost converter can be derived as

The improved method idea is based on the PV panel’s

Operating point (OP) movement for the improved method under sudden increase of temperature.

Operating point (OP) movement for the improved method under sudden decrease of temperature.

At this time, the PV panel OP is perturbed by the improved method to point

Operating point (OP) movement procedure under sudden increase of temperature.

Finally, only a few steps by a traditional MPPT method (P&O, INC, HC, etc.) are used to track the new maximum power point (MPP of 50°C).

Like the previous case, when the temperature suddenly decreases, the PV panel OP moves from point

Operating point (OP) movement procedure under sudden decreasing of temperature.

Figure

Flowchart of the proposed method.

It can be concluded from [

The MPPT performance has become an interesting argument for manufacturers. However, there are no standards, which define how to evaluate MPPT performance, but some proposals are presented in the scientific literature [

The static MPPT efficiency is the ability of the MPPT algorithm to find and hold the MPP under steady-state conditions (normal solar radiation and cell temperature), while the dynamic MPPT efficiency is the capacity of an MPPT algorithm to survey the MPP under variable conditions [

The average MPPT tracking efficiency is given as

where

In order to assess the performance of the suggested MPPT approach, a simulation comparison of the proposed MPPT approach with other MPPT methods, namely, P&O, INC, and the modified MPP-Locus in [^{2}, 800 W/m^{2}, and 600 W/m^{2}. To verify the performance of the proposed method, a MATLAB/Simulink model of the overall PV system shown in Figure

Scenario of temperature variation.

Schematic of the proposed PV system with MPPT algorithm.

The 1Soltech 1STH-215-P is the PV panel used in this simulation, where its electrical specifications are shown in Table

Parameter of the 1Soltech 1STH-215-P PV module at STC:

Parameters | Value |
---|---|

Maximum power | |

Voltage at MPP | |

Current at MPP | |

Open-circuit voltage | |

Short-circuit current | |

Temperature coefficient of | |

Temperature coefficient of |

The simulation results of the improved P&O MPPT method compared with the conventional P&O MPPT method under the scenario of temperature with constant irradiation are shown in Figure ^{2}, (b) 800 W/m^{2}, and (c) 600 W/m^{2}. Furthermore, thanks to its tracking mechanism, the tracking speed is significantly faster than the P&O algorithm, and it is noticeable that the improved MPPT tactic is able to reduce significantly the power losses especially at temperature variation. Moreover, it is clear from Figure

Simulation result comparison between the P&O method and the P&O-IMP method under the scenario of temperature variation with constant solar radiation: (a) 1000 W/m^{2}; (b) 800 W/m^{2}; (c) 600 W/m^{2}.

Figure

Comparison of the voltage and power in the steady state at

The response speed comparison for Figure

To demonstrate the effectiveness and robustness of tracking of the proposed MPPT tactic, a calculation of the dynamic ^{2}, (b) 800 W/m^{2}, and (c) 600 W/m^{2}.

Efficiency profile comparison between the P&O MPPT algorithm and the improved P&O MPPT under the scenario of temperature variation with normal solar radiation (a) 1000 W/m^{2}, (b) 800 W/m^{2}, and (c) 600 W/m^{2}.

From Figure ^{2} of solar radiation, 97.92% and 99.81% at 800 W/m^{2}, and 97.99% and 99.87% at 600 W/m^{2}, whereas the improved P&O MPPT method shows the best efficiency in the variation of temperature, which is above 95% during the whole test time, and in the steady-state operation, the instantaneous efficiency is significantly stable and varies in the range of 99.9% to 99.99%. As shown in Figure ^{2} of solar radiation, 98.64% and 99.97% at 800 W/m^{2}, and 98.2% and 99.98% at 600 W/m^{2}.

Figure ^{2}, (b) 800 W/m^{2}, and (c) 600 W/m^{2}, where it is clear that the good performance of the improved INC MPPT tactic provides the MPP with high accuracy and limits the power losses at temperature variation.

Simulation results from the comparison between the INC and INC-IMP methods under the scenario of temperature variation with constant solar irradiance: (a) 1000 W/m^{2}; (b) 800 W/m^{2}; (c) 600 W/m^{2}.

From the simulation results, the improved INC MPPT method provides a good tracking of the MPP during the time simulation, especially when the temperature changes, where it can minimize significantly the power loss. On the other hand, Figure

Comparison of the voltage and power in the steady state at

The response speed comparison for Figure

Figure ^{2}, (b) 800 W/m^{2}, and (c) 600 W/m^{2}. From Figure

Efficiency profile comparison between the conventional INC and improved INC MPPT methods under the scenario of temperature variation with normal solar radiation (a) 1000 W/m^{2}, (b) 800 W/m^{2}, and (c) 600 W/m^{2}.

The simulation results presented in Figure ^{2}, 800 W/m^{2}, and 600 W/m^{2}, respectively. The results show clearly the high tracking performance of the improved Mod-MPP-Locus MPPT method compared with the Mod-MPP-Locus MPPT method, which losses the tracking direction due to temperature change. Furthermore, the improved Mod-MPP-Locus MPPT method tracks the MPP at any temperature level easily with a neglected oscillation around the MPP and the MPP is accurately reached in case of the fast change of temperature, whereas the Mod-MPP-Locus MPPT method presents a high power loss due to fast temperature change, which is clearly observed in Figure

Simulation results from the comparison between the modified and the improved modified MPP-Locus-IMP MPPT methods under the scenario of temperature variation with constant solar irradiance: (a) 1000 W/m^{2}; (b) 800 W/m^{2}; (c) 600 W/m^{2}.

Figure

Comparison of the voltage and power in the steady state at

The response speed comparison for Figure

The simulation results presented in Figure ^{2}, (b) 800 W/m^{2}, and (c) 600 W/m^{2}.

Efficiency profile comparison between the Mod-MPP-Locus MPPT method and the improved Mod-MPP-Locus MPPT method under the scenario of temperature variation with a normal solar radiation (a) 1000 W/m^{2}, (b) 800 W/m^{2}, and (c) 600 W/m^{2}.

Due to the repeated loss of the tracking direction, we can observe from Figure ^{2}, 98.61% and 99.96% at 800 W/m^{2}, and 98% and 99.98% at 600 W/m^{2}, respectively.

Finally, Table

Simulation result performance from the comparison of different MPPT control methods.

Algorithm | P&O | P&O-IMP | INC | INC-IMP | Mod-Locus MPPT | Mod-Locus MPPT-IMP |
---|---|---|---|---|---|---|

Tracking speed | Medium | Faster | Medium | Faster | Slow | Faster |

Steady-state oscillation | Large | Small | Medium | Small | Medium | Small |

Accuracy/efficiency | Low | High | Medium | High | Medium | High |

Dynamic efficiency range (%) | 97.92–97.99 | 98.2–98.64 | 97.94–98 | 98–98.64 | 97.93–98 | 98–98.64 |

Static efficiency range (%) | 99.63–99.87 | 99.9–99.98 | 99.45–99.83 | 99.9–99.7 | 99.51–99.83 | 99.89–99.98 |

Time response (ms) | 11.03 | 8.97 | 9.77 | 4.52 | 19.47 | 16.9 |

Power steady-state error (W) | 2 | Neglected | 1 | Neglected | 0.6 | Neglected |

Voltage steady-state error (V) | 1.5 | Neglected | 1 | Neglected | 1 | Neglected |

Power overshoot | High | Insignificant | High | Insignificant | High | Insignificant |

This work proposes an improved MPPT algorithm, which can be easily added to other existing MPPT algorithms to enhance their tracking performance, especially under temperature variation. A comparative study with three MPPT algorithms, namely, perturb and observe (P&O), incremental conductance (INC), and modified MPP-Locus, has been done under MATLAB/Simulink software. The simulation results demonstrate good contributions on the dynamic response to the temperature variation, as well as on the steady-state performance, where there is a significant improvement in the response time, minimization of oscillation size around the MPP, and the tracking efficiency; as a result, a high amount of power loss can be significantly reduced. Furthermore, the improved MPPT tactic can significantly enhance the tracking efficiency of the existing MPPT methods.

Data are available on request.

The authors declare that there is no conflict of interest regarding the publication of this paper.