# A Novel Isolated Intelligent Adjustable Buck-Boost Converter with Hill Climbing MPPT Algorithm for Solar Power Systems

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## Abstract

**:**

_{A}, L

_{B}, L

_{C}, L

_{D}, and L

_{E}) and four power MOSFETs (S

_{A}, S

_{B}, S

_{C}, and S

_{D}) are used in the proposed novel isolated intelligent adjustable buck-boost (IIABB) converter to adjust the applied voltage across the load side. It also has a constant, stable output voltage. The new IIABB converter is simulated and verified using MATLAB R2021b, and the performances of the proposed IIABB converter and conventional SEPIC converter are compared. The solar photovoltaic module output voltages of 20 V, 30 V, and 40 V are given as inputs to the proposed IIABB converter, and the total output voltage of the proposed converter is 48 V. In the new IIABB converter, the duty cycle of the power MOSFET has a small variation. The proposed IIABB converter has an efficiency of 92~99%. On the other hand, in the conventional SEPIC converter, the duty cycle of a power MOSFET varies greatly depending on the relationship between the output and input voltage, which deteriorates the efficiency of the converter. As a result, this research contributes to the development of a novel type of IIABB converter that may be employed in renewable energy systems to considerably increase system performance and reduce the cost and size of the system.

## 1. Introduction

## 2. Conventional SEPIC Converter

_{O}of the SEPIC converter can be calculated.

_{i}represents the input voltage and D represents the duty cycle.

_{1}= L

_{2}is represented by the equation below:

_{imin}is the absolute minimum voltage that can be fed into the converter, D

_{max}represents the maximum duty cycle, f

_{sw}represents switching frequency, and $\Delta {\mathrm{i}}_{\mathrm{o}\mathrm{m}\mathrm{a}\mathrm{x}}$ represents an acceptable output current ripple.

_{1}is ON, the current I

_{L2}starts increasing, and the current across inductor L

_{1}, which comes from the instantaneous voltage source, is approximately equivalent to the input voltage V

_{in}, the diode D

_{1}is opened, the input capacitor C

_{1}supplies the energy, and it operates according to the waveform during time 0–t

_{0}as shown in Figure 3. When S

_{1}is OFF, the current across the capacitor C

_{1}becomes equal to the I

_{L1}, therefore the inductor does not allow instantaneous changes in current. The current flows across the inductor L

_{2}in a negative direction. This is because if the switch is closed long enough for a half cycle of resonance with inductor L

_{2}, the potential (voltage) across capacitor C

_{1}will remain the same, which can be seen clearly with the help of the waveform during time t

_{0}–t

_{1}as shown in Figure 3. Two inductors, L

_{1}and L

_{2}, a diode D

_{1}, a power MOSFET S

_{1}, an output capacitor C

_{2}, and a coupling capacitor C

_{1}are used in the converter. Due to the presence of a coupling capacitor with negative polarity, diode D

_{1}is reverse biased upon activation. When the coupling capacitor discharges, both the inductors L

_{1}and L

_{2}get charged. During this time, the diode is turned off, and it becomes forward biased. Inductor L

_{1}transfers energy to the coupling capacitor, while inductor L

_{2}delivers energy to the output terminal. The L

_{1}and L

_{2}inductors can be coiled on a single core, and they can receive the same switching period voltage. A coupled inductor minimizes the size of the whole circuitry and the overall cost of the system.

_{in}is the input voltage across the power MOSFET S

_{1}when it is turned on and off. I

_{S1}represents current across the power MOSFET S

_{1}, I

_{C1}represents current across the coupling capacitor, and I

_{L1}and I

_{L2}inductor currents build linearly. I

_{D1}is the diode current, I

_{C1}is the current through the coupling capacitor, and I

_{C2}is the current through the output capacitor.

## 3. An Isolated Intelligent Adjustable Buck-Boost Converter Is Proposed

_{A}, L

_{B}, L

_{C}, L

_{D}, and L

_{E}) and four power MOSFETs (S

_{A}, S

_{B}, S

_{C}, and S

_{D}) are used in the proposed novel isolated intelligent adjustable buck-boost (IIABB) converter to adjust the applied voltage across the load side. Its advantage is that this IIABB converter has an intelligent control strategy so that the power MOSFETs (S

_{B}, S

_{C}, and S

_{D}) will not perform high-frequency switching caused by switching loss caused by those power MOSFETs (S

_{B}, S

_{C}, and S

_{D}) only for long ON or OFF times. As a result, the circuit has a different output power. To get the different output, further research can be performed on this design. In the proposed IIABB converter, the power MOSFET S

_{A}stores the output energy of the solar photovoltaic (PV) simulator in the inductor(s) L

_{A}, L

_{B}, L

_{C}, L

_{D}, and L

_{E}. When S

_{A}is ON, the inductor(s) L

_{A}, L

_{B}, L

_{C}, L

_{D}, and L

_{E}energy is transferred to the load side, which actuates the power MOSFETs S

_{B}, S

_{C}, and S

_{D}to further change the output voltage in order to stabilize the output power, as shown in Figure 4; the parameters for the proposed IIABB converter are given in Table 1.

_{pv}, the diode voltage V

_{DA}, the output voltage V

_{o}, and the relationship between the number of connected inductors N and the turn ratio n (taking the turn ratio of 1:1) as expressed by Equation (5) below:

_{pv}of 20 V, 30 V, and 40 V and a 48 V constant output voltage, which provides a consistent charging voltage for the various loads.

#### 3.1. Topology Analysis and Intelligent Control Strategy

_{A}is conducting and the output diode D

_{A}is reverse biased, and no currents will be conducting during this time. The magnetizing inductor L

_{MA}from inductor L

_{A}is subjected to a voltage, and its current rises according to Equation (6).

_{A}is ON and power MOSFETs S

_{B}, S

_{C}, and S

_{D}are OFF (as shown in Figure 4a), and the proposed IIABB converter operates according to the waveform during time t

_{0}–t

_{1}as shown in Figure 5. In the next interval of the proposed IIABB converter, the power MOSFET S

_{B}is ON and the power MOSFETs S

_{A}, S

_{C}, and S

_{D}are OFF (as shown in Figure 4b), and the proposed IIABB converter operates according to the waveform during the time t

_{1}–t

_{2}, as shown in Figure 5. In mode 1, the V

_{o}Equation (7) is as follows:

_{MB}from inductor L

_{B}, whose current begins to increase when V

_{CA}is applied.

_{21}–t

_{2}, the switch S

_{A}is not conducting a rectifying diode, and a coupled inductor will convert the energy stored in L

_{MA}and L

_{MB}into an output. According to Equations (9) and (10) below, the current on L

_{MA}and L

_{MB}will decrease when the voltage polarity is reversed on them.

_{2}. Figure 5 illustrates the key waveforms of the proposed IIABB converter.

_{A}is ON and the power MOSFETs S

_{B}, S

_{C}, and S

_{D}are OFF (as shown in Figure 4a), and the proposed IIABB converter operates according to the waveform during time t

_{0}–t

_{1}as shown in Figure 5. In the next interval of the proposed IIABB converter, the power MOSFET S

_{C}is ON and the power MOSFETs S

_{A}, S

_{B}, and S

_{D}are OFF (as shown in Figure 4c), and the proposed IIABB converter operates according to the waveform during time t

_{1}–t

_{2}as shown in Figure 5. The output voltage V

_{o}can be calculated with the help of Equation (11) below:

_{A}is ON. The rest of the switches S

_{B}, S

_{C}, and S

_{D}are turned OFF (as shown in Figure 4a), and the proposed IIABB converter operates according to the waveform during time t

_{0}–t

_{1}(Figure 5). In the next interval of the proposed IIABB converter, the power MOSFET S

_{D}is ON and the power MOSFETs S

_{A}, S

_{B}, and S

_{C}are OFF (as shown in Figure 4d), and the proposed IIABB converter operates according to the waveform during time t

_{1}–t

_{2}(as shown in Figure 5). The output voltage V

_{o}can be calculated with the help of Equation (12) below:

#### 3.2. Topology Analysis

_{pv}and the DC blocking capacitor C

_{A}are considered constants. D is the duty ratio of the switch, DT is the period in which the switch is closed, and (1 − D)T is the period during which it is open.

_{A}is open, the diode is ON, and Kirchhoff’s voltage law applies as follows:

_{LA}= V

_{pv}

_{A}is closed, the diode is OFF. The voltage across L

_{A}for the interval DT is as follows:

_{pv}, V

_{LA}, and V

_{CA}gives the following:

#### 3.3. Hill-Climbing Algorithm

- (1)
- With its disturbance characteristics, it will cause power loss and lower the system’s performance.
- (2)
- It is not suitable for partially shaded environments; it will operate at the local maximum power point, resulting in low system efficiency.

## 4. Simulation and Experimental Results

#### Simulation Result

_{o}, irrespective of the solar PV module output voltage V

_{pv}.

_{pv}of 20 V and N = 1. Figure 6a shows the switching modulation of the gate pulse of four switches by showing that switches S

_{A}and S

_{B}are in conduction mode whereas S

_{C}and S

_{D}are not conducting, and the duty cycle of the power MOSFET S

_{A}is calculated to be 0.7 by choosing the value of N = 1 with the help of Equation (7).

_{pv}20 V is applied with a duty cycle of 0.7, an output voltage of 48 V is achieved, as shown in Figure 6b for the use of battery charge.

_{pv}of 20 V and N = 2. Figure 7a shows the switching modulation of the gate pulse of four switches with switches S

_{A}and S

_{C}in conduction mode, whereas S

_{B}and S

_{D}are not conducting, and the duty cycle of the power MOSFET S

_{A}is calculated to be 0.55 by choosing the value of N = 2 with the help of Equation (11). When V

_{pv}= 20 V is applied with a duty cycle of 0.55, an output voltage of 48 V is achieved, as shown in Figure 7b for the use of battery charge.

_{pv}of 30 V and N = 3. Figure 8a shows the switching modulation of the gate pulse of four switches with switches S

_{A}and S

_{D}in conduction mode, whereas S

_{B}and S

_{C}are not conducting, and the duty cycle of the power MOSFET S

_{A}is calculated to be 0.35 by choosing the value of N = 3 with the help of Equation (12). When V

_{pv}= 30 V is applied with a duty cycle of 0.35, an output voltage of 48 V is achieved, as shown in Figure 8b.

^{2}and a temperature of 25 °C; we have taken 50 V and 5.5 A for the open circuit voltage and short circuit current, respectively, and 200 W as the maximum power achieved.

_{pv}and the constant output voltage variation because a battery charger requires constant output voltage with various advantages. As the number of inductors increases, the current ripple of the proposed converter reduces, providing high gain with a low duty ratio when compared to a conventional SEPIC converter. Moreover, the coupled inductor reduces the size of the whole circuitry.

_{pv}of 20 V and number of inductors N = 1. Figure 11a displays the switches S

_{A}and S

_{B}are operating, while S

_{C}and S

_{D}are not operating, and the switches work via an intelligent control strategy. Figure 11b shows the waveform of V

_{pv}= 20 V and an output voltage of V

_{out}= 48 V at a duty cycle of 0.7 according to Equation (5). Figure 11 shows the experimental waveform of the proposed IIABB converter for a V

_{pv}of 30 V and N = 1. Figure 12a displays the switches S

_{A}and S

_{B}are operating; the switches S

_{C}and S

_{D}are not operating via an intelligent control strategy. Figure 12b shows the waveform of V

_{pv}= 20 V and an output voltage of V

_{out}= 48 V at a duty cycle of 0.62 according to Equation (5), as shown in Table 4.

^{2}and a temperature of 25 °C, the experimental waveform of the proposed IIABB converter, and N = 1, 2, and 3, respectively. In these cases, the proposed IIABB converter has an intelligent control strategy and HC algorithm. First, switch S

_{A}works by the HC algorithm. Second, switches S

_{B}, S

_{C}, and S

_{D}work via an intelligent control strategy. Finally, V

_{pv}= 40 V, i.e., the HC algorithm, catches the maximum power point voltage V

_{mpp}, and V

_{out}= 48 V can offer battery charging, as shown in Table 4.

## 5. Conclusions

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 2.**SEPIC Converter’s operate mode: (

**a**) power MOSFET S

_{1}during the ON state, (

**b**) power MOSFET S

_{1}during the OFF state.

**Figure 4.**Operation of the proposed IIABB converter with an intelligent control strategy: (

**a**) the power MOSFET S

_{A}is ON and the power MOSFETs S

_{B}, S

_{C}, and S

_{D}are OFF, (

**b**) the power MOSFET S

_{B}is ON and the power MOSFETs S

_{A}, S

_{C}, and S

_{D}are OFF, (

**c**) the power MOSFET SC is ON and the power MOSFETs S

_{A}, S

_{B}, and S

_{D}are OFF, and (

**d**) the power MOSFET S

_{D}is ON and the power MOSFETs S

_{A}, S

_{B}, and S

_{C}are OFF.

**Figure 5.**Voltage and current waveforms show V

_{DS}, I

_{DS}, I

_{DA}, I

_{CA}, I

_{LA}, and I

_{LB}along with the duty cycle of the proposed IIABB converter.

**Figure 6.**Simulation result of the proposed IIABB converter for solar PV module input voltage V

_{pv}of 20 V and corresponding output voltage V

_{o}= 48 V and number of connected inductors N = 1 with duty cycle 0.7 (

**a**) gate pulse waveform where S

_{A}and S

_{B}are in operating condition and S

_{C}and S

_{D}are not operating, and (

**b**) the V

_{pv}and output voltage V

_{o}.

**Figure 7.**Simulation result of the proposed IIABB converter for solar PV module input voltage V

_{pv}of 20 V and corresponding output voltage V

_{o}= 48 V and number of connected inductors N = 2 with duty cycle 0.55 (

**a**) gate pulse waveform where S

_{A}and S

_{C}are in operating condition and S

_{B}and S

_{D}are not operating, and (

**b**) the V

_{pv}and output voltage V

_{o}.

**Figure 8.**Simulation result of the proposed IIABB converter for solar PV module input voltage V

_{pv}of 30 V and corresponding output voltage V

_{o}= 48 V and number of connected inductors N = 3 with duty cycle 0.35 (

**a**) gate pulse waveform where S

_{A}and S

_{D}are in operating condition and S

_{B}and S

_{C}are not operating, and (

**b**) the V

_{pv}and output voltage V

_{o}.

**Figure 10.**Experimental waveforms of the proposed IIABB converter for V

_{pv}of 20 V and N = 1: (

**a**) experimental waveforms of switches S

_{A}and S

_{B}are operating; S

_{C}and S

_{D}are not operating; and (

**b**) waveforms of V

_{pv}= 20 V and output voltage V

_{out}= 48 V via an intelligent control strategy at a duty cycle of 0.7.

**Figure 11.**Experimental waveforms of the proposed IIABB converter for V

_{pv}of 30 V and N = 1: (

**a**) experimental waveforms of switches S

_{A}and S

_{B}that are operating; S

_{C}and S

_{D}are not operating; and (

**b**) waveforms of V

_{pv}= 30 V and output voltage V

_{out}= 48 V via an intelligent control strategy at a duty cycle of 0.62.

**Figure 12.**Experimental waveforms of the proposed IIABB converter for V

_{pv}of 40 V and N = 1: (

**a**) experimental waveforms of switches S

_{A}and S

_{B}are operating; S

_{C}and S

_{D}are not operating; and (

**b**) waveforms of V

_{pv}= 40 V and output voltage V

_{out}= 48 V via an intelligent control strategy and HC MPPT algorithm at a duty cycle of 0.55.

**Figure 13.**Experimental waveforms of the proposed IIABB converter for V

_{pv}of 40 V and N = 2: (

**a**) experimental waveforms of switches S

_{A}and S

_{C}are operating; S

_{B}and S

_{D}are not operating; and (

**b**) waveforms of V

_{pv}= 40 V and output voltage V

_{out}= 48 V via an intelligent control strategy and HC MPPT algorithm at a duty cycle of 0.38.

**Figure 14.**Experimental waveforms of the proposed IIABB converter for V

_{pv}of 40 V and N = 3: (

**a**) experimental waveforms of switches S

_{A}and S

_{D}are operating; S

_{B}and S

_{C}are not operating; and (

**b**) waveforms of V

_{pv}= 40 V and output voltage V

_{out}= 48 V via an intelligent control strategy and HC MPPT algorithm at a duty cycle of 0.3.

Component/Parameter | Specification | Quantity |
---|---|---|

Solar PV simulator output voltage (V_{pv}) | 20–40 V | -- |

Switching frequency | 20 kHz | -- |

Rated power | 200 W | -- |

Capacitor (C_{A}, C_{B}) | 220 µF, 500 µF | 2 |

Inductors (L_{A}, L_{B}, L_{C}, L_{D}, L_{E}) | 1 mH | 5 |

Output voltage (V_{o}) | 48 V | -- |

References | Parameters | ||||
---|---|---|---|---|---|

Voltage Gain | Number of Switches | Number of Diodes | Number of Inductors | Continous Input Current | |

Proposed | $\frac{\mathrm{D}{\mathrm{V}}_{\mathrm{pv}}}{1-\mathrm{D}}\mathrm{N}\xb7\mathrm{n}$ | 4 | 2 | 5 | Yes |

SEPIC | $\frac{\mathrm{D}}{1-\mathrm{D}}$ | 1 | 2 | 2 | Yes |

Boost | $\frac{\mathrm{D}}{1-\mathrm{D}}$ | 1 | 1 | 1 | Yes |

[27] | $\frac{1+\mathrm{D}}{1-\mathrm{D}}$ | 1 | 2 | 2 | Yes |

[28] | $\frac{3\mathrm{D}}{1-\mathrm{D}}$ | 1 | 2 | 2 | Yes |

[29] | $\frac{2\mathrm{D}}{1-\mathrm{D}}$ | 1 | 2 | 2 | No |

[30] | $\frac{-3\mathrm{D}}{1-\mathrm{D}}$ | 1 | 3 | 3 | No |

Parameters | Specification |
---|---|

Open circuit voltage (V_{oc}) | 50 V |

Short circuit current (I_{sc}) | 5.5 A |

Maximum power point voltage (V_{mpp}) | 40 V |

Maximum power point current (I_{mpp}) | 5 A |

Maximum power point (P_{mpp}) | 200 W |

Number of Inductors | V_{pv} | V_{o} | D | Efficiency |
---|---|---|---|---|

N = 1 | 20 V | 48 V | 0.70 | 92% |

30 V | 48 V | 0.62 | 94% | |

40 V | 48 V | 0.55 | 96% | |

N = 2 | 20 V | 48 V | 0.55 | 96% |

30 V | 48 V | 0.47 | 98% | |

40 V | 48 V | 0.38 | 99% | |

N = 3 | 20 V | 48 V | 0.45 | 98% |

30 V | 48 V | 0.35 | 99% | |

40 V | 48 V | 0.30 | 99% |

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## Share and Cite

**MDPI and ACS Style**

Sabir, B.; Lu, S.-D.; Liu, H.-D.; Lin, C.-H.; Sarwar, A.; Huang, L.-Y. A Novel Isolated Intelligent Adjustable Buck-Boost Converter with Hill Climbing MPPT Algorithm for Solar Power Systems. *Processes* **2023**, *11*, 1010.
https://doi.org/10.3390/pr11041010

**AMA Style**

Sabir B, Lu S-D, Liu H-D, Lin C-H, Sarwar A, Huang L-Y. A Novel Isolated Intelligent Adjustable Buck-Boost Converter with Hill Climbing MPPT Algorithm for Solar Power Systems. *Processes*. 2023; 11(4):1010.
https://doi.org/10.3390/pr11041010

**Chicago/Turabian Style**

Sabir, Bushra, Shiue-Der Lu, Hwa-Dong Liu, Chang-Hua Lin, Adil Sarwar, and Liang-Yin Huang. 2023. "A Novel Isolated Intelligent Adjustable Buck-Boost Converter with Hill Climbing MPPT Algorithm for Solar Power Systems" *Processes* 11, no. 4: 1010.
https://doi.org/10.3390/pr11041010