KR101222090B1 - Maximum Power Point Tracking Power Conversion and Charging System - Google Patents

Abstract

A maximum power point tracking power conversion and charging system is disclosed. The maximum power point tracking power conversion and charging system includes a fuel cell unit for generating a voltage, a secondary battery unit for storing the generated voltage, and a boosted type for boosting a voltage generated in the fuel cell unit and providing the secondary battery unit. A power converter, a maximum power point tracking circuit that calculates a charging current command for maximum power point tracking using the current flowing into the fuel cell unit and a generated voltage, and boosts the current charged to the secondary battery unit to follow the charging current command And a charging current control circuit for controlling the type power converter. Accordingly, since the secondary battery unit may be charged at the maximum power point of the fuel cell unit, the energy conversion efficiency may be increased to maximize the energy utilization rate.

Description

Maximum Power Point Tracking Power Conversion and Charging System

 The present invention relates to a maximum power point tracking power conversion and charging system, and more particularly, a newly designed maximum power point tracking circuit is applied when charging a battery with power generated from an energy source such as a fuel cell or a solar cell. The present invention relates to a maximum power point tracking power conversion and charging system capable of maximizing energy conversion efficiency and utilization rate.

Recently, generation and application of electric power using new energy sources such as fuel cells and solar cells are increasing.

In order to continuously use the energy generated from the energy source, an energy storage device such as a battery is used, and the power conversion and charging circuit is a circuit for boosting the power generated from the energy source and storing it in the battery.

The power generated from the energy source varies in voltage depending on the load current, and the output of the generated power also changes. Therefore, in order to maximize energy utilization, a technique for charging a battery at a current and voltage value at which power generated from an energy source is maximum is required.

In the field of solar cells, the maximum power point tracking technology is applied to achieve the above-mentioned object. However, in the field of conventional fuel cells, only a constant voltage power source is used as the energy source, and the maximum power point tracking technology is not applied. However, in the case of fuel cells using biofuels in vivo, the maximum power point tracking technique is required to increase the energy utilization rate because of the intermittent power generated.

On the other hand, the conventional maximum power point tracking technology used in the field of solar cells has a problem that it is impossible to apply to a circuit that requires miniaturization, such as a biofuel cell due to the complex circuit and system.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and provides a maximum power point tracking power conversion and charging system capable of charging a battery at a maximum power point with power generated from a fuel cell using biofuel in vivo. There is a purpose.

Maximum power point tracking power conversion and charging system according to an embodiment of the present invention, the fuel cell unit for generating a voltage, the secondary battery unit for storing the generated voltage, by boosting the voltage generated in the fuel cell unit A boost type power converter provided to the secondary battery unit, a maximum power point tracking circuit for calculating a charging current command for maximum power point tracking using the current flowing into the fuel cell unit and the generated voltage, and the secondary And a charging current control circuit for controlling the boost type power converter so that the current charged by the battery unit follows the charging current command.

The boost type power converter may include a first boost inductor for storing energy generated by the fuel cell unit, a first transistor for controlling energy storage of the first boost inductor, and energy stored in the first boost inductor as an output capacitor. It may include a second transistor for transmitting and an output capacitor receiving the energy stored in the first boost inductor to generate an output voltage.

The maximum power point tracking circuit may include: a multiplier that calculates power by multiplying a voltage generated by the fuel cell unit and a current flowing into the fuel cell unit, a delay circuit that calculates a delay power by delaying the calculated power for a predetermined time period; A first subtractor that subtracts the calculated delay power from the calculated power, and a first proportional value that generates an increment value of the current command such that the amount of small change in power output from the first subtractor is zero for maximum power point tracking An integral controller, an adder that adds the incremental value of the current command and the initial value of the current command, and scales the value output from the adder to a predefined gain value to calculate a charge current command for maximum power point tracking; It may include an amplifier.

The charging current control circuit may include a second subtractor that calculates an error between a current charged in the secondary battery unit and a charging current command output from the amplifier, and generates and outputs a voltage command to minimize the calculated error. 2 a pulse width modulation (PWM) pulse for controlling a duty ratio of the first transistor by comparing a proportional-integration controller and a voltage command output from the second proportional-integrator with a preset sawtooth wave. And a comparator configured to generate the pulse width modulated pulse to the first transistor.

Each of the first proportional-integral controller and the second proportional-integral controller may be one of a lead-lag compensator and a proportional-integral-integral (PID) controller.

The first boost inductor has one end connected to the fuel cell part, the other end connected to a first node, the first transistor, a drain terminal connected to the first node, and a gate terminal connected to the charging current control unit. A source terminal connected to the ground terminal, a source terminal connected to the first node, a drain terminal connected to a second node, and a gate terminal connected to a gate of the first transistor A signal opposite to a terminal is applied, and one end of the output capacitor is connected to the second node, and the other end thereof is connected to a ground terminal.

According to the present invention, in configuring a circuit for converting and charging power generated in a fuel cell, by applying a newly designed maximum power point tracking circuit and a charging current control circuit, the battery is charged at the maximum power point generated in the fuel cell. This can be done. Accordingly, in using energy sources such as fuel cells and solar cells, there is an effect of maximizing energy utilization by increasing energy conversion efficiency. In addition, compared with the conventional complex maximum power point tracking circuit and system that can be used as a simple analog circuit can be implemented, there is an advantage that can be miniaturized the power conversion and charging circuit.

1 is a view showing a maximum power point tracking power conversion and charging system according to an embodiment of the present invention.
2 is a graph for explaining the operation principle of the maximum power point tracking.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

1 is a view showing a maximum power point tracking power conversion and charging system according to an embodiment of the present invention.

Referring to FIG. 1, the maximum power point tracking power conversion and charging system 100 of the present invention includes a fuel cell unit 1, a secondary battery unit 2, a boost type power converter 3, and a maximum power point tracking circuit. (4), and a charging current control circuit (5).

In the maximum power point tracking power conversion and charging system 100, the fuel cell unit 1 and the secondary battery unit 2 are integrally fused and may be inserted into a living body or a blood vessel.

The fuel cell unit 1 is an energy source for generating a low voltage, and may include a battery or a solar cell for outputting a DC voltage. As an example, the fuel cell unit 1 may generate a voltage using a material in the living body such as glucose in the blood, in which case the generated voltage is low enough that charging is difficult to be performed in the secondary battery unit 2. It can have a voltage value.

The secondary battery unit 2 is configured to store or utilize the boosted voltage, and may be an electrochemical storage device having a direct current energy storage function or an electronic device using a direct current voltage.

The boost type power converter 3 boosts the voltage generated by the fuel cell unit 1 and provides the boosted voltage to the secondary battery unit 2.

The maximum power point tracking circuit 4 calculates a charging current command (or reference) for maximum power point tracking using the voltage and current of the fuel cell unit 1.

The charging current control circuit 5 controls so that the current charged in the secondary battery unit 2 follows the charging current command calculated by the maximum power point tracking circuit 4.

According to the present maximum power point tracking power conversion and charging system 100, by using the maximum power point tracking circuit 4 and the charging current control circuit 5, 2 at the maximum power point generated in the fuel cell unit 1 Since the secondary battery unit 2 can be charged, in using an energy source such as a fuel cell or a solar cell, the energy conversion efficiency can be increased to maximize the energy utilization rate.

The boost type power converter 3 according to an embodiment of the present invention includes a first boost inductor 31, a first transistor 32, a second transistor 33, and an output capacitor 35.

The first boost inductor 31 accumulates energy generated by the fuel cell unit 1. Here or below, the accumulation of energy refers to the storage of energy.

The first transistor 32 controls the boost operation. Specifically, energy accumulation of the first boost inductor 31 is controlled.

The second transistor 33 provides the output capacitor 35 with energy stored in the first boost inductor 31.

The output capacitor 35 receives and stores energy stored in the first boost inductor 31 and generates an output voltage.

Referring to FIG. 1, the circuit structure of the boost type power converter 3 will be described in more detail.

One end of the first boosted inductor 31 is connected to the fuel cell unit 1, the other end thereof is connected to the first node N ₁ , and the first transistor 32 has a drain terminal of the first node N _1. ), A gate terminal is connected to the output terminal of the comparator 53 of the charging current control circuit 5, which will be described later, and a source terminal is connected to the ground terminal.

In the second transistor 33, a source terminal is connected to the first node N ₁ , and a drain terminal is connected to the second node N ₂ . Meanwhile, a signal opposite to the gate terminal of the first transistor 32 may be applied to the gate terminal of the second transistor 33. Specifically, the NOT gate (not shown) is connected to the output of the charging current control circuit 5 (that is, the output of the comparator 53), so that the output signal of the comparator 53 is converted by the NOT gate (not shown). After that, the converted signal may be applied to the gate terminal of the second transistor 33.

One end of the output capacitor 35 is connected to the second node N ₂ , and the other end thereof is connected to the ground terminal.

The diode D has an anode connected to the source terminal of the second transistor 33 and a cathode connected to the drain terminal of the second transistor 33.

The first transistor 32 and the second transistor 33 are shown as N-type MOS transistors, but may also be P-type MOS transistors. In addition, the first transistor 32 and the second transistor 33 may be bipolar transistors. As such, when the first transistor 32 and the second transistor 33 are changed, some of the circuit structures shown in FIG. 1 may be changed, and such a change will be apparent to those skilled in the art. The first transistor 32 and the second transistor 33 are preferably MOS transistors, but may also be bipolar transistors.

Referring to FIG. 1, the operation principle of the boost type power converter 3 will be described in more detail.

The output voltage and output current of the boost type power converter 3 are controlled by the first transistor 32, and when the first transistor 32 is turned on, the current flowing in the first boost inductor 31 increases linearly. The energy generated in the fuel cell 1 is accumulated in the first boost inductor 31. In this condition, when the first transistor 32 is turned off, the energy accumulated in the first boost inductor 31 transfers energy to the output capacitor 35 through the diode D added to the second transistor 33. . In this case, the second transistor 33 may be turned on to reduce the voltage drop generated by the diode D added to the second transistor 33.

The output voltage of the boosted power converter 3 (ie, the voltage of the second node) is controlled by the ON / OFF time ratio (ie, duty ratio) of the first transistor 32. Specifically, when the ON time of the first transistor 32 becomes long, the output voltage of the boost type power converter 3 becomes high. On the contrary, when the ON time of the first transistor 32 decreases, the output voltage of the boost type power converter 3 becomes low.

The maximum power point tracking circuit 4 includes a multiplier 41, a delay circuit 42, a first subtracter 43, a first proportional-integral (PI) controller 44, an adder 45, and an amplifier 46. ).

The multiplier 41 multiplies the voltage generated in the fuel cell unit 1 by the current flowing through the fuel cell unit 1 to calculate the power P _k .

The delay circuit 42 delays the calculated power P _k for a preset time to calculate the delay power delay power P _{k -1} .

First subtractor 43 calculates the difference (ΔP) of the power (P _k) and the delayed power (P _{k -1).}

The first proportional-integral (PI) controller 44 generates an increment value ΔI of the current command such that the small change amount ΔP of power is zero for maximum power point tracking.

The adder 45 generates a current command by adding the increment value ΔI of the current command and the initial value I _ini of the current command.

On the other hand, since the current command is composed of the initial value plus the incremental value, and the increment value is initially zero, an arbitrary current command is initially applied, which is described as the initial value of the current command. The initial value of the current command is given as an arbitrary value, and in the maximum power point tracking power conversion and charging system 100, as shown in FIG. 2 to be described later, the maximum power point tracking circuit starts with the initial value of the current command. Controls to find _MPP value.

The amplifier 46 scales the value output from the adder (i.e., the generated current command) to a predefined gain value k. Accordingly, the charge current command for maximum power point tracking can be calculated from the amplifier 46.

The charging current control circuit 5 includes a second subtractor 51, a second proportional-integral controller 52, and a comparator 53.

The second subtractor 51 calculates a current error. Specifically, the second subtractor 51 calculates an error (that is, a current error) between the current charged by the secondary battery unit 2 and the charging current output from the amplifier 46, and outputs the calculated error. do.

The second proportional-integral controller 52 controls the charging current to minimize the current error output from the second subtractor 51.

The comparator 53 generates a drive pulse of the first transistor 32. Specifically, a pulse width modulation (PWM) pulse for controlling the duty ratio of the first transistor 32 is compared by comparing a voltage command output from the second proportional-integrator 52 with a sawtooth wave of a predetermined type. And generate the generated pulse width modulation pulses to the first transistor 32.

The output current of the first boost inductor 31 of the boost type power converter 3, that is, the inductor current is equal to the generated current of the fuel cell unit 1, and in order to control this value, The width will be adjusted. Since adjusting the width of the pulse is the same as changing the voltage, the output value of the second proportional-integral controller 52 becomes a reference voltage for changing the pulse width. If the reference voltage is large, the pulse width is large, and if the reference voltage is small, the pulse width can be reduced. As a result, the inductor current can also be increased or decreased. Therefore, the reference voltage value is described herein as a voltage command.

2 is a graph illustrating an operation principle of maximum power point tracking.

1 and 2, the operation principle of the maximum power point tracking circuit 4 and the charging current control circuit 5 of the maximum power point tracking power conversion and charging system 100 will be described in more detail.

Referring to FIG. 2, the small change amount ΔP of power at the maximum power point is 0, and the voltage and the current generated in the fuel cell unit 1 are the maximum power point voltage V _MPP and the maximum power point current, respectively. (I _MPP ). When the current supplied from the fuel cell unit 1 is smaller than the maximum power point current I _MPP , the small change amount ΔP of power according to the increase of the current becomes a positive value, and the fuel cell current is the maximum power point current ( If larger than IMPP), the small change amount ΔP of power with increasing current becomes negative.

According to the maximum power point tracking method of the present invention, the amount of charge current can be controlled so that the amount of change ΔP becomes zero by calculating the amount of change ΔP of power.

By detecting the voltage and current of the fuel cell unit 1 shown in FIG. 1, the instantaneous power value P _k can be calculated by the multiplier 41. When the difference between the calculated instantaneous power value P _k and the instantaneous power value P _{k -1} delayed for a predetermined time is obtained by the first subtractor 43, the small change amount ΔP of power is calculated by the following equation (1). You can get it together.

Here, k may be a natural number having a size of 1 or more.

The first proportional-integral controller 44 shown in FIG. 1 generates an incremental value ΔI of the current command such that the small change amount ΔP of power is zero.

In this case, the first proportional-integral controller 44 has a function of making the small change amount ΔP of the power to zero. For example, a lead-lag compensator and a proportional-integral-integral ( It may also include a controller having a similar function, such as a PID) controller.

The adder 45 generates a current command by adding the increment value ΔI of the current command and the initial value I _ini of the current command, and multiplies the gain k of the amplifier 46 to generate a charge current command for tracking the maximum power point. Calculate

Here, the current command indicates a reference current for maximum power point tracking. Thus, when the present maximum power point tracking power conversion and charging system 100 is in the normal state, the current command becomes the same value as I _MPP . The maximum power point tracking power conversion and charging system 100 does not calculate the I _MPP value from the beginning, but instead of calculating the current value of the fuel cell unit 1 using the incremental value of the power, the second proportional-integral controller 52. ) Increases the reference current to gradually converge on the value of I _MPP (incremental value of the current command), and adds the incremental value of the current command to the initial value (I _ini ) of the current command and then tracks the maximum power point in the fuel cell unit 1. The current value that must be generated for this purpose can be calculated. Therefore, if the second proportional-integral controller 52 operates normally, the generated current of the fuel cell unit 1 may be equal to the calculated current value.

The charging current control circuit 5 controls the current charged in the secondary battery unit 2 to follow the charging current command output from the amplifier 46.

Here, multiplying the calculated current command by the gain k of the amplifier 46 calculates the current to be actually charged in the secondary battery unit 2, where the calculated current value is the charging current command. When the voltage is boosted by the boost type power converter 3, the charge current command may have a different magnitude from the current generated in the fuel cell unit 1 and the current charged in the secondary battery unit 2. Therefore, if the second proportional-integral controller 52 operates normally, the charging current of the secondary battery unit 2 may be equal to the current generated in the fuel cell unit 1.

The second subtractor 51 shown in FIG. 1 calculates an error between the charging current command and the battery charging current, and the second proportional-integration controller 52 generates a voltage command to minimize the error.

In this case, the above-described second proportional-integral controller 52 has a function for minimizing the charging current error, for example, a lead-lag compensator and a proportional-integral-integral (PID) controller It may also include a controller having a similar function such as.

The comparator 53 uses a pulse command generated by the second proportional-integral controller 52 and outputs a pulse width modulation (PWM) pulse to control the ON / OFF time of the first transistor 32 operating at a high frequency. Create and print

According to the present maximum power point tracking power conversion and charging system 100, since the ON / OFF time of the first transistor 32 can be controlled by the above-described method, the maximum power point generated in the fuel cell unit 1 can be controlled. In the secondary battery unit 2 is charged. Accordingly, in using energy sources such as fuel cells and solar cells, it is possible to maximize energy utilization by increasing energy conversion efficiency.

In addition, since the maximum power point tracking circuit 4 and the charging current control circuit 5 can be realized by a simple analog circuit compared to the conventional complex maximum power point tracking circuit and system, the maximum power point tracking circuit 4 can be realized. And the charging current control circuit 5 can be miniaturized, and further, the maximum power point tracking power conversion and charging system 100 can be miniaturized.

On the other hand, the maximum power point tracking power conversion and charging system according to another embodiment of the present invention, a boost type power converter, a maximum power point tracking circuit, and a charging current control circuit.

The maximum power point tracking power conversion and charging system flows into the booster type power converter 3 and the fuel cell unit 1, which boost the voltage generated by the fuel cell unit 1 and provide it to the secondary battery unit 2. The maximum power point tracking circuit 4 for calculating the charging current command for the maximum power point tracking using the current generated and the voltage generated in the fuel cell unit 1, and the current charged in the secondary battery unit 2 And a charging current control circuit 5 for controlling the boost type power converter 3 to follow the charging current command.

According to the present maximum power point tracking power conversion and charging system, the secondary battery unit 2 can be charged at the maximum power point of the fuel cell unit 1.

While the above has been shown and described with respect to preferred embodiments of the invention, the invention is not limited to the specific embodiments described above, it is usually in the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

1 fuel cell unit 2 secondary battery unit
3: boost type power converter 4: maximum power point tracking circuit
5: charging current control circuit 31: first boost inductor
32: first transistor 33: second transistor
35 output capacitor 41 multiplier
42 delay circuit 43 first subtractor
44: first proportional-integral controller 45: adder
46 amplifier 51 second subtractor
52: second proportional-integral controller 53: comparator
100: maximum power point tracking power conversion and charging system

Claims (6)

A fuel cell unit generating a voltage;
A secondary battery unit storing the generated voltage;
A boost type power converter which boosts the voltage generated by the fuel cell unit and provides the boosted voltage to the secondary battery unit;
A maximum power point tracking circuit configured to calculate a charging current command for maximum power point tracking using the current flowing into the fuel cell unit and the generated voltage; And
And a charge current control circuit configured to adjust a turn-on / turn-off duty ratio of the boost type power converter so that the current charged by the secondary battery unit follows the charge current command.
The maximum power point tracking circuit,
A multiplier for calculating electric power by multiplying the voltage generated by the fuel cell unit with a current flowing into the fuel cell unit;
A delay circuit for delaying the calculated power for a predetermined time to calculate delay power;
A first subtractor which subtracts the calculated delay power from the calculated power;
A first proportional-integral controller for generating an increment value of the current command such that the amount of change in power output from the first subtractor is zero for maximum power point tracking;
An adder for adding an increment value of the current command and an initial value of the current command; And
And an amplifier for scaling a value output from the adder to a predetermined gain value to calculate a charging current command for maximum power point tracking. The method of claim 1,
The boost type power converter,
A first boost inductor storing energy generated by the fuel cell unit;
A first transistor for controlling energy storage of the first boost inductor;
A second transistor transferring energy stored in the first boost inductor to an output capacitor; And
And an output capacitor configured to receive the energy stored in the first boosted inductor to generate an output voltage. delete The method of claim 1,
The charging current control circuit,
A second subtractor for calculating an error between a current charged by the secondary battery unit and a charging current command output from the amplifier;
A second proportional-integral controller for generating and outputting a voltage command for minimizing the calculated error; And
By comparing the voltage command output from the second proportional-integrator with a sawtooth wave of a predetermined type, generates a pulse width modulation (PWM) pulse for controlling the duty ratio of the first transistor, the generated pulse And a comparator for providing a width modulated pulse to the first transistor. 5. The method of claim 4,
Each of the first proportional-integral controller and the second proportional-integral controller,
A maximum power point tracking power conversion and charging system, characterized in that either one of a lead-Lag compensator and a proportional-differential-integral (PID) controller. The method of claim 2,
The first boosted inductor has one end connected to the fuel cell part and the other end connected to the first node.
In the first transistor, a drain terminal is connected to the first node, a gate terminal is connected to the charging current control circuit, a source terminal is connected to the ground terminal,
In the second transistor, a source terminal is connected with the first node, a drain terminal is connected with a second node, and a gate terminal is applied with a signal opposite to that of the first transistor,
The output capacitor, the maximum power point tracking power conversion and charging system, characterized in that one end is connected to the second node, the other end is connected to the ground terminal.

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