This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (
This paper proposes a novel Maximum Power Point Tracking (MPPT) control method of thermoelectric power generation for the constant load. This paper reveals the characteristics and the internal resistance of thermoelectric power module (TM). Analyzing the thermoelectric power generation system with boost chopper by state space averaging method, the output voltage and current of TM are estimated by with only single current sensor. The proposed method can seek without calculating the output power of TM in this proposed method. The basic principle of the proposed MPPT control method is discussed, and then confirmed by digital computer simulation using PSIM. Simulation results demonstrate that the output voltage can track the maximum power point voltage by the proposed MPPT control method. The generated power of the TM is 0.36 W when the temperature difference is 35 °C. This is well accorded with the VP characteristics.
Currently attention is focusing on the energy harvesting technologies to electrify the smallrated electric devices by environmental energy such as waste heat energy and machine vibration. One of the power generation methods by waste heat energy is the thermoelectric power generation by Seebeck effect of thermoelectric power module (TM) [
We have proposed a method of suppressing the thermal leakage using heat pipes. The heat pipes were used for heat transfer from TM to heat sink avoiding thermal leakage. We confirmed to supply the electric power to the selfcontained wireless telemetry by using the heat pipes and boost converter continuously. However, the boost converter controlled the output voltage of TM only. In [
One of the MPPT control methods is the hillclimbing method, which is employed to seek the maximum power point by calculating the power with a voltage and current sensors [
This paper proposes a novel MPPT control method for thermoelectric power generation system of the constant load with only single current sensor. Estimating the output of the TM, the MPPT controller can track the maximum power point. Analyzing the thermoelectric power generation system with boost chopper by state space averaging method [
In this paper, the six TMs (FPH112702AC), which consist of three seriesconnected TMs and two parallelconnected TMs is used. The cool side of the TM is set on a heat sink. The hot side of the TM is set on a tray with hot water.
VI Characteristic of the thermoelectric module.
VP Characteristic of the thermoelectric module.
We approximate the TMs for modeling on the PSIM. The output current
From Equation (1), the power
At the maximum power point of
From Equation (3), the maximum power point voltage
From Equation (4) and Equation (1),
From this equation, the internal resistance
System configuration of the thermoelectric power generation system using a boost chopper.
This section reveals that the output of the TM can estimate by using the linear analyzing result of the system. This paper uses the state space averaging method [
Relationship between the switching condition and
Equivalent circuits of the thermoelectric power generation system. (
During the MODE 1, the switch G is ON, and
From these equations, the matrix is given by
The switching time is very short. So, the right side of Equations (6), (7) and (8) are assumed the constant value. As a result, we approximate these equations as follows
During the MODE 2, the switch G is OFF, and the current flows into D.
From these equations, the matrix is given by
The right side of Equations (13), (14) and (15) are assumed the constant value. We approximate these equations as follows
During the MODE 3,
From these equations, the matrix is given by
The right side of Equations (20), (21) and (22) are assumed the constant value. We approximate these equations as follows
Therefore, the difference equations in one switching cycle are given as follows
From these difference equations, the differential equations are given as follows:
The averaging state vector is assumed as follows
The state averaging equation can be derived as
Therefore
The average value
The output voltage
The output current
Therefore
The PI controller uses to track the reference and reduce the error, which is obtained by subtracting
A circuit diagram with the proposed MPPT control method.
Thus the MPPT control method in this paper can be estimated the output of the TM with only current sensor by analyzing the boost chopper using state space averaging method. The internal resistance of the TM is constant at the maximum power point whether the temperature difference or not. Hence, the voltage of the maximum power point can be decided without calculation of the power.
Digital computer simulation using PSIM software is implemented to confirm the validity and practicability of the proposed MPPT control method. The TM is demonstrated current source in PSIM software, where the output of the current source is decided by Equation (1).
In this paper, the cutoff frequency
Circuit parameters of the thermoelectric power generation system.
Parameter  Symbol  Value 

Input capacitor 

100 μF 
Inductor 

150 μH 
Output capacitor 

1000 μF 
Load resistor 

1 kΩ 
Winding resistor of the inductor


0.26 Ω 
Conduction resistance of the diode D 

0.1 Ω 
ONresistance of the MOSFET 

8.5 mΩ 
Simulation results by using the proposed MPPT control when the thermal difference is 35 °C. (
This paper implements the simulation by using the conventional hillclimb method.
Simulated results by using the conventional hillclimb method when the thermal difference is 35 °C. (
Simulation results in the case of the thermal difference fluctuation. (
Simulation results of
This paper proposed a novel MPPT control method for thermoelectric power generation using the state space averaging method. Estimating the output of the TM with only a current sensor, the MPPT controller can track the maximum power point. In the proposed method, the maximum power point voltage can be decided by the estimated values and the internal resistance at the maximum power point.
This paper revealed the electric characteristics and internal resistance of the TM. Analyzing the thermoelectric power generation system with boost chopper by state space averaging method, the output voltage and current of TM were estimated with only single current sensor. The maximum power point voltage can track without calculating the output power of the TM. Digital computer simulation was implemented to demonstrate the validity and practicability of the proposed method using PSIM. From the simulation results, the output power was about 0.36 W with the proposed MPPT control method when the temperature difference was 35 °C. Simulation results demonstrate that the proposed MPPT controller can track the maximum power point regardless of the temperature variation perfectly.