KR101926008B1 - A control and operating method of power converter for power supply of hydrogen electrolytic device using solar energy - Google Patents

Abstract

The present invention relates to a control and operation method of a power converter for power supply of a hydrogen electrolytic device using solar light, which converts input power of a solar power generation part by using a DC/DC converter so as to control power supply to at least two water electrolysis devices which are connected in parallel. The method comprises: a step (a1) of receiving a current voltage and current of the solar power generation part; a step (a2) of primarily, setting each case to a power point state according to a result of combination of whether a power increment is negative or positive and whether a voltage increment is negative or positive, and secondarily, setting the power point state according a result of combination of whether the power increment is negative or positive and whether the voltage increment is negative or positive and the previously-set power point state, and increasing or decreasing the reference voltage according to each power point state; a step (a3) of generating a PWM control signal of the DC/DC converter through proportional integral (PI) control according to the increased or decreased reference voltage; and a step (b) of controlling power supply by turning on/off a part of the least two water electrolysis devices according to the magnitude of power output to the water electrolysis device. With the above system, the steps of a conventional P&O method are subdivided to improve the response of the power converter even when generated power fluctuation is very large, and the water electrolysis devices connected in parallel to each other are selectively turned on/off according to the generated power so as to prevent deterioration due to overvoltage and maximize the use of surplus power.

Description

TECHNICAL FIELD [0001] The present invention relates to a control method for a power converter for power supply of a hydrogen electrolytic device using solar light,

In the present invention, water is electrolyzed by using sunlight, and the improved P & O control function required to cope with the fluctuation of electric power generated by the sunlight according to the amount of sunshine and temperature is incorporated in the DC / DC converter, And more particularly, to a control method and an operation method of a power converter for power supply of a hydrogen electrolysis apparatus using solar light, which maximizes surplus power that can not be used when the solar power is below a certain power generation amount depending on the capacity.

We are establishing and implementing greenhouse gas reduction targets through climate agreements so that the global average temperature does not rise above 2 ℃ due to environmental problems caused by global warming. To this end, we are making efforts to reduce greenhouse gas emissions by reducing the use of chemical raw materials and expanding renewable energy sources.

Solar power and wind power are representative renewable energy, but the power generation amount is not constant, and there is a disadvantage that a large installation area is required according to the required power generation amount. In addition, the generated power is used in a way that is linked with the power system through the DC / AC inverter, which is a power converter, and it takes up a great deal of use of renewable energy. However, due to the limitation of the operating voltage range of this inverter and irregular power generation, the amount of power generation is limited.

On the other hand, as a clean energy source capable of replacing fossil fuels, a technology for producing hydrogen has been highlighted, and many technologies have been developed. Currently, hydrogen production is largely based on fossil raw materials such as coal, natural gas and petroleum, and renewable energy such as bio, solar and wind power, and nuclear power.

In the technology of producing hydrogen, the electrolytic device is very important as a core technology. The water electrolytic unit is required to produce hydrogen by using electric energy, but the electric energy cost is high from the economic point of view. From an economic point of view, it is most appropriate to produce hydrogen through a reformer, a natural gas that is a fossil raw material. However, since natural gas can be used as a direct energy source, other, more economical methods are needed.

Hydrogen production technologies are largely divided into the electrolysis of alkaline (AE) electrolysis, which is a cold water electrolysis technique, and the electrolysis of a solid polymer electrolyte membrane (PEM). Also, it is classified into High Temperature Electrolysis (HTE) technology using a solid oxide.

The power-receiving technique has advantages and disadvantages depending on the method. The alkaline method has a disadvantage in that it requires a lot of electric energy because the current density is lower than that of the polymer electrolyte method, and the polymer electrolyte method has a disadvantage in that an expensive catalyst such as platinum or iridium is used. However, it is predicted that the polymer electrolyte method will be advantageous in the price and performance competition in the future, and the technology using the polymer electrolyte method is being developed.

Therefore, there is a need for techniques for obtaining hydrogen as energy source while using less electrical energy. In particular, considering the cost of a simple installation, as well as the social cost, it is necessary to use renewable energy with a constant power output. To this end, it is necessary to supply power to the water electrolyzer, which is a load, in accordance with the generation output of renewable energy having a direct current output, and to maximize the production amount of hydrogen, since it can directly affect the lifetime of the electrolyzer and the hydrogen production .

In particular, in order to obtain hydrogen using solar energy, a technique of extracting maximum power from an irregular energy amount has been proposed [Patent Document 1]. Technologies for producing hydrogen using such solar energy have been proposed [Patent Literatures 2 and 3].

Korean Published Patent Application No. 10-2012-0027782 (published on March 22, 2012) Korean Patent Publication No. 10-2006-0131580 (published on December 20, 2006) Korean Patent Registration No. 10-0806168 (issued Feb. 21, 2008)

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and it is an object of the present invention to provide an improved P & O control function incorporated in a DC / DC converter in order to cope with fluctuation of electric power generated by sunlight, And a method of controlling and operating a power converter for supplying power to a hydrogen electrolysis apparatus using sunlight.

It is also an object of the present invention to provide a solar power generation system having a switch section for connecting a plurality of power receiving devices in parallel and turning on and off each of them, And to provide a method of controlling and operating a power converter for supplying power to a hydrogen electrolysis apparatus using light.

Particularly, an object of the present invention is to set a minimum voltage required by each of the water electrolytic apparatuses and a maximum voltage not exceeding an overvoltage by parallelly connecting a plurality of electrolytic water electrolysis apparatuses, And to provide a method of controlling and operating a power converter for powering a hydrogen electrolysis apparatus using solar light, which supplies electric power to a water electrolytic solution in the electrolytic cell.

It is also an object of the present invention to provide a method and apparatus for controlling and operating a power converter for powering a hydrogen electrolysis apparatus using sunlight, the operation time of each of the water electrolysis apparatuses being cumulatively counted to control crossing operation of the water electrolysis apparatus .

In order to achieve the above object, according to the present invention, there is provided a solar-powered hydrogen-electrolysis apparatus power source for controlling the supply of solar power to at least two water electrolysis devices connected in parallel by converting the input power of the solar power generator into a DC / (A1) receiving a current voltage and a current of the solar power generation unit; (a2) First, each case is set to the power point state according to the result of whether or not the power increment is negative or positive and whether or not the voltage increment is negative or negative. After the initial power increment is negative or positive Setting a power point state according to a previously set power point state and increasing or decreasing a reference voltage according to each power point state; (a3) generating a PWM control signal of the DC / DC converter through PI (proportional integral) control according to the increased or decreased reference voltage; And (b) controlling power supply by turning on / off at least a part of at least two power receiving units according to the magnitude of power output to the power receiving unit.

In addition, the present invention provides a method of controlling and operating a power converter for supplying power to a hydrogen electrolysis apparatus using solar light, the method comprising the steps of: (a2) when the power increment is negative and the voltage increment is negative, Sets the power point state to a third state when the power increment is negative and the voltage increment is positive and sets the power point state to a third state when the power increment is positive and the power increment Sets the point state to a second state and sets the power point state to a first state at first when the power increment is positive and the voltage increment is positive and if the power increment is positive and the voltage increment If it is negative, the power point state is set to the sixth state if the power point state is the first, fourth, and sixth states after the first time, otherwise, the power point state is set to the second state , If the power increment is positive and the voltage increment is positive, the power point state is set to the fifth state if the power point state is the second, third, and fifth states after the beginning; otherwise, the power point state state is set to a first state, and when the power point state is set to the first, fourth, and sixth states, the reference voltage is decreased, and the power point state is set to the second, third, The reference voltage is increased.

According to another aspect of the present invention, there is provided a method of controlling and operating a power converter for supplying power to a hydrogen electrolytic apparatus using solar light, wherein the power supplied to the water electrolytic apparatus (hereinafter, If the divided electric power is greater than a preset maximum electric power after dividing the electric power by the number of the devices, the controller selects one of the powered off devices to be turned on, and turns on the divided electric power. , One of the turned on water electrolytic devices is selected and turned off.

Further, the present invention provides a method of controlling and operating a power converter for supplying power to a hydrogen electrolysis apparatus using solar light, wherein, in step (b), one of the power electrolytic devices turned off to turn on When selecting one, select the faucet with a minimum cumulative usage time, and when selecting one of the faucet devices turned on to turn off, And a device is selected.

In addition, the present invention provides a method of controlling and operating an electric power converter for supplying power to a hydrogen electrolysis apparatus using solar light, wherein in step (b), it is checked whether a voltage developed for initial startup is increased, And one of the water electrolytic water electrolysis apparatuses is selected and turned on.

As described above, according to the control and operation method of the power converter for supplying power to the hydrogen electrolysis apparatus using sunlight according to the present invention, by dividing the steps of the conventional P & O method, The response of the converter is improved, so that the hunting phenomenon occurs in the output voltage or the output voltage is prevented from being seriously lowered.

According to the method for controlling and operating the power converter for supplying power to the hydrogen electrolysis apparatus using solar light according to the present invention, a plurality of water electrolysis apparatuses are connected in parallel, selectively turned on / off, The deterioration due to the overvoltage can be prevented, and the surplus power which can not be used when the power generation amount is less than the constant power generation amount can be utilized the most.

In addition, according to the control and operation method of the power converter for supplying power to the hydrogen electrolysis apparatus using solar light according to the present invention, by keeping the cumulative operation time of a plurality of water electrolysis apparatuses installed in accordance with the amount of sunlight power generation, The durability of the apparatuses can be uniformly maintained.

1 is a block diagram of a configuration of a hydrogen electrolysis apparatus using sunlight according to a first embodiment of the present invention.
2 is an equivalent circuit of a DC / DC buck converter of a DC / DC converter according to the first embodiment of the present invention.
3 is a flow chart illustrating a method of controlling and operating a power converter for powering a hydrogen electrolysis apparatus using sunlight according to a first embodiment of the present invention.
4 is a configuration diagram illustrating control steps of a DC / DC converter according to the first embodiment of the present invention;
5 is a graph showing a VP characteristic curve of a photovoltaic power generation to cope with the present invention.
6 is a flowchart illustrating a step of calculating a reference voltage following a maximum power point according to the first embodiment of the present invention.
FIG. 7 is a graph of a section according to power fluctuation for applying the improved P & O algorithm according to the first embodiment of the present invention; FIG.
8 is a diagram illustrating a criterion for determining a maximum power point according to a voltage variation according to the first embodiment of the present invention;
9 is a circuit configuration diagram for generating a PWM control signal of the converter through PI control according to the first embodiment of the present invention.
10 is a flowchart showing the operation of a power supply switch section for maintaining the operation time of the water electrolytic apparatus according to the first embodiment of the present invention.
11 is a flowchart for explaining on / off control of the water electrolytic apparatus according to the second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings.

In the description of the present invention, the same parts are denoted by the same reference numerals, and repetitive description thereof will be omitted.

First, a solar-light-based hydrogen electrolysis apparatus 100 according to a first embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 1, the solar-light-based hydrogen electrolysis apparatus 100 according to the present invention includes a solar power generation unit 10 for collecting sunlight to generate electricity, a DC / DC A switch 20 for turning on and off the power supply, a control unit 40 for controlling power conversion, a water electrolysis device 50 for producing hydrogen by decomposing water, And a storage device 60 for storing data.

First, the solar power generating unit 10 is composed of a plurality of solar cell arrays, and is used for collecting sunlight incident from the outside to generate electricity, and silicon and a composite material are usually used.

Next, the DC / DC converter 20, as a power converter, converts the power input from the solar power generator 10 and supplies it to the water electrolytic solution 50.

In particular, as shown in FIG. 1, the DC / DC converter 20 receives input of renewable energy that is generated by DC, receives a buck type DC / DC converter to configure the power converter.

Also, the DC / DC converter 20 is controlled by the control unit 40, and supplies power required for the power receiving apparatus 50, which is a load, with an improved P &

Next, the water electrolytic solution 50 is a device for producing hydrogen by electrolyzing water. It is the most economical, reliable and easy to mass-produce the method of purifying water obtained from nature to produce hydrogen and electrolyzing it.

Preferably, the water electrolytic dissolution apparatus 50 is composed of at least two or more water electrolytic dissolution apparatuses (or unit devices), and the plurality of water electrolytic dissolution apparatuses are connected in parallel to each other.

When the power required for the load is reduced by the control of the control unit 40, the input power switch 30 of some of the power receiving devices 50 is shut off and the remaining power receiving devices 50 are continuously .

Next, the switch section 30 is constituted by a plurality of load switches, and each switch is connected to each of the plurality of the water electrolytic apparatuses 50. [ The output of the DC / DC converter 20 is supplied to or blocked from each of the power receiving units 50 in accordance with the on / off of each switch of the switch unit 30. [

The switch unit 30 is turned on / off under the control of the control unit 40.

Next, the control unit 40 is a device for controlling the DC / DC converter 20, the switch unit 30, and the like. In other words, the control unit 40 controls the power converter such as the DC / DC converter 20 to control the maximum power point (MPP) of the photovoltaic generation unit 10, So as to supply electric power. The control unit 40 controls the load switch of the switch unit 30 so as to limit the power supply to only a part of the plurality of the power receiving units 50 so as to control the power supplied to the power receiving units 50 do.

Looking at the I-V characteristics of the sunlight, the current will increase as the voltage decreases. Therefore, when the voltage of the electrolytic solution 50 is increased, the amount of current increases as the production of hydrogen increases due to the activation of the electrode catalyst. However, when the amount of renewable energy generated is the maximum, deterioration of the electrode and the electrolyte membrane progresses as the voltage increases. In order to protect this, the control unit 40 controls the voltage through the voltage limit of the power converter such as the DC / DC converter 20. Also, power is supplied to the water electrolytic solution 50, which is a load, through an improved P & O control method in which the amount of renewable energy generated varies or is improved.

In addition, when the minimum voltage required by the water electrolytic solution 50 is reached, hydrogen can not be produced even if there is an amount of generation of renewable energy. Therefore, the control unit 40 cuts off a part (or at least one) of the load switches of the switch unit 30 when the power is the minimum power required by the water electrolytic apparatus 50 as a load. Thus, power is supplied to the remaining water electrolytic solution 50 to control the continuous production of hydrogen.

On the other hand, as shown in Fig. 1, the control unit 40 receives power from the control power source. At this time, the control power source may be supplied from the solar power generating unit 10, or may be supplied from a commercial power source or a battery.

Next, the storage device 60 is a device for storing generated hydrogen.

Next, the configuration of the DC / DC converter 20 according to the first embodiment of the present invention will be described in detail with reference to FIG.

As described above, the DC / DC converter 20 is configured as a power converter in the present invention. The DC / DC converter 20 is preferably a buck converter for reducing the output of the DC / DC converter 20 or a boost converter for boosting the output in consideration of the power configuration of the renewable energy and the load characteristics of the power receiver. Can be configured.

Referring to the DC equivalent circuit of the buck converter as shown in FIG. 2, the secondary voltage V _PV and the output voltage V _out can be expressed by the following equations.

[Equation 1]

Where D is the duty ratio and R ₀ is the load resistance. Also, R _L is the inductor resistance inside the DC / DC converter. This results in conduction losses in the inductor.

The voltage gain G _V according to this equation is as follows.

&Quot; (2) "

The efficiency? Is expressed by Equation (3).

&Quot; (3) "

을 적용한다.here,

Is applied.

The efficiency of the buck converter is independent of the duty ratio D in Equation (3), and it can be confirmed that the larger the load resistance R ₀ is, the better the efficiency is.

Since the generated power of the renewable energy fluctuates greatly, when the generated power is lowered, the load power also decreases. Therefore, the efficiency is inevitably deteriorated. In addition, since the duty ratio fluctuates depending on the voltage fluctuation, the buck converter system independent of the duty ratio is advantageous in terms of efficiency.

Therefore, the DC / DC converter 20 is configured by a buck converter method.

Next, the construction of the water electrolytic solution 50 according to the first embodiment of the present invention will be described more specifically.

As described above, the water electrolytic solution 50 is a device for producing hydrogen by electrolyzing water.

Preferably, a PEM (Polymer Electrolyte Membrane) method with good electrolysis efficiency is applied. In addition, an alkaline electrolysis (AE) method can be applied. The solid polymer electrolyte (PEM) method has fast chemical response and high current density with respect to power fluctuation. On the other hand, the alkali water electrolysis (AE) method has a slow chemical response and low current density with respect to power fluctuation.

In PEM type PEM electrolysis, each electrode reacts as follows.

[Chemical formula 4]

Basically, a certain voltage is applied to the electrode for the electrolysis reaction, so that the electrode reacts to generate hydrogen. The reaction energy in the above reaction formula is as follows.

[Chemical formula (5)

As shown in Formula (5), theoretically, the hydrothermal reaction proceeds at 1.228 V or higher. It is known that, under actual conditions, hydrogen is generated at 1.7 V or more, depending on the electrolytic solution. In addition, it is known that as the voltage increases, the paradigm current used for the hydrogen generation reaction increases and the hydrogen production rate increases.

If 20 water-electrolytic electrodes with a voltage of 1.7 V capable of producing hydrogen are connected in series, the minimum voltage for producing hydrogen should be 34V. Even if power generation amount is present in renewable energy such as solar power, if the minimum voltage is less than 34V, it will be impossible to produce hydrogen for energy.

Therefore, preferably, the water electrolytic dissolution apparatus 50 is composed of at least two or more water electrolytic dissolution apparatuses (or unit devices), and the plurality of water electrolytic dissolution apparatuses are connected in parallel to each other. When the power required for the load is lower than the power required for the load, some of the power receiving apparatus input power switch 30 is turned off and the remaining power receiving apparatus 50 is continuously supplied with power.

That is, if the generated voltage of the renewable energy becomes the minimum voltage required by the water electrolytic solution 50, the hydrogen can not be produced in all of the three electrolytic electrolytic devices 50 despite the amount of renewable energy generated. At this time, when the power supply to one of the water electrolysis apparatuses 50 is stopped, the remaining two water electrolysis apparatuses 50 can continuously produce hydrogen because they are within the voltage range capable of producing hydrogen.

At this time, when the amount of new renewable energy is reduced, the load is calculated and another water receiving apparatus is stopped. And the amount of the renewable energy generated by the remainder of the unit can be reduced to within the voltage range required by the water electrolytic unit 50.

On the other hand, when all three of the water electrolytic water treatment apparatuses 50 are operated at the time when the solar water power generation amount increases, the voltage of the electrodes of the water electrolytic water treatment apparatus 50 becomes insufficient due to a shortage of power generation amount. Therefore, it is possible to utilize the power generation amount of sunlight by adding one by one while confirming the generation amount of solar light and supplying power to the water electrolytic solution 50.

In order to maximize the power generation of solar power as described above, a plurality of water electrolysis apparatuses 50 are installed to maximize the amount of renewable energy generated.

On the other hand, it is assumed that the water electrolytic solution 50 has 18 2V cells connected in series. At this time, the operation characteristics of the PEM water electrolytic device are as follows. When 38 VDC is supplied from the power source device, the voltage of the electrode of the water electrolytic device gradually increases. And as the voltage gradually increases, the amount of current increases as well. The production of hydrogen is proportional to the current.

That is, when 30VDC 1A is required, electrolysis of water starts to produce hydrogen. And consumes a current of 20A at 38V. This is the maximum current consumption. When the voltage and current are applied, the electrolyte membrane of the water electrolytic apparatus is deteriorated and the durability is reduced.

In addition, the starting voltage and the voltage after 2 hours are reduced from 38VDC to 35VDC. This is because the water electrolytic device itself drops in voltage due to internal deterioration. Therefore, when 18 electrodes (CELL) are used in series, the voltage range is 30 ~ 38V, 1 ~ 20A. In the water electrolytic apparatus, the amount of hydrogen production varies depending on the electric current.

Next, a method of calculating the installed capacity of the solar power generation unit 10 according to the first embodiment of the present invention will be described.

As described above, when the voltage range of the electrolytic electrolysis electrode capable of producing hydrogen is 1.7 to 2.0 VDC, when one electrolytic electrolysis unit 50 uses 20 electrodes, it produces hydrogen in the range of 34 to 40 VDC . If a current of 20A is required at a maximum of 40V, 800W of electric power is required.

When three power receiving devices are used as in the example of Fig. 1, a power of 2400 W is required. Here, the power capacity for the control power source for driving the power converter and the efficiency of the power converter must be further calculated. In addition, when the solar cell I-V characteristic is observed, the voltage of the solar cell decreases rather than the solar power when the amount of sunshine is the maximum. Therefore, the maximum power standard is calculated as about 80% of the solar photovoltaic capacity, and the capacity of the renewable energy is installed. The formula for calculating the installed capacity of new and renewable energy is as follows.

&Quot; (6) "

Renewable energy installation capacity = load capacity + control power + power converter efficiency + solar capacity reduction

Next, a method of controlling and operating the power converter for supplying power to the hydrogen electrolysis apparatus using solar light according to the first embodiment of the present invention will be described with reference to FIG. 3 to FIG.

As shown in FIG. 3, the control and operation method of the power converter for supplying power to the hydrogen electrolysis apparatus using solar light according to the present invention largely comprises the step of controlling the DC / DC converter 20 following the maximum power point of the sunlight (S10) for selecting the water electrolytic solution 50 and supplying power (S20).

First, step S10 of controlling the DC / DC converter 20 will be described.

The DC / DC converter 20 is controlled by the control unit 40, and the control unit 40 may be configured in the DC / DC converter 20.

As shown in Fig. 3, the control unit 40 detects the voltage and current of the sunlight (V _pv , I _PV ) (S11). From this, the power P _PV is calculated. Then, the reference voltage V _ref is calculated using the improved P & O algorithm (S12). The PWM control signal of the DC / DC converter 20 is generated through PI (proportional integral) control according to the reference voltage V _ref (S13).

FIG. 4 schematically shows a configuration for controlling the DC / DC converter 20. As shown in FIG.

4, the control unit 40 includes a P & O algorithm unit for calculating and generating a control target reference voltage V _ref to control the voltage of the DC / DC converter 20, And a PI controller that controls the actual PV direct-current voltage (V _pv ) to a target value in accordance with the output voltage V _ref . In particular, the control unit 40 controls the output voltage V _PV and the output current I _PV of the PV panel of the solar power generation unit 10 to track the maximum power point MPP of the solar power generation unit 10, And feeds back the supply voltage V _out and the supply current I _out supplied to the load (the water electrolytic device, etc.).

That is, the DC / DC converter 20 receives electric power from the solar power generation unit 10 constituted by the PV panel. At this time, the output voltage (V _PV ) of the PV panel of the solar power generation unit (10) and the output current (V _PV ) of the PV power generation unit I _PV ) is controlled. Specifically, a reference voltage (V _ref ) is calculated and generated through an improved P & O algorithm. Further, the difference from the actual PV direct-current voltage (V _pv ) is calculated by the reference voltage (V _ref ), and the calculated difference is supplied to the proportional integral gain (PI). The difference between the output and the actual PV direct current (I _pv ) becomes a reference control value of the current source to generate the PWM control signal of the DC / DC converter 20.

Specifically, the MPPT algorithm is required because the PV panel has a nonlinear voltage-current characteristic with a unique point at which the generated power is maximized. The maximum power point (MPP) depends on the temperature and solar radiation conditions of the panel. Both conditions change day by day and depend on the season. In addition, solar radiation can change rapidly because it changes with the state of the atmosphere, such as clouds. It is very important to accurately track the MPP under all possible conditions to always get the maximum power point.

In other words, the I-V characteristics of solar energy, which is a renewable energy, can be minimized when the voltage is maximum. Therefore, the maximum power follow-up (MPPT) is required to maximize the generated power while reducing the voltage. The control unit 40 basically uses a P & O (Perturbation and Observation) control method as a technique for following the maximum power point MPP. The P & O control method periodically increases or decreases the output voltage of the PV panel and compares the previous output power with the current output power to find the maximum power operating point. That is, the conventional P & O algorithm controls power comparison for linear changes.

Particularly, the present invention is intended not only to deal with solar power generation on a clear day and a cloudy day, but also to cope with solar power generation on a day when the generation amount fluctuates very much, such as a cloudy sunny day.

FIG. 5 shows a curve for the power (P) characteristic versus the voltage (V) of the solar power generation. In FIG. 5, curve A represents the V-P characteristic curve of the sunlight optimal for a clear day, and curve B represents the V-P characteristic curve of the cloudy day. Curve C is the V-P characteristic curve of solar power generation on a clear cloudy day.

The existing P & O algorithm is mainly a method corresponding to the case of the curves A and B of FIG. In this case, there is no problem in supplying power to the water electrolytic apparatus as a load even by using the conventional MPPT algorithm. However, as shown by the curve C, the power fluctuation is severe on a clear cloudy day. Therefore, if the corresponding control operation is delayed, the output voltage may cause a hunting phenomenon, or the output voltage may be severely lowered. As a result, the power supply to the water electrolytic apparatus becomes ineffective. This is due to the characteristics of the water electrolyzer, which is a load. In other words, when the sudden increase or decrease of the amount of sunshine is shown, it is limited to respond.

In particular, the advantages of the conventional P & O algorithm are that the controller is simple and widely used, but it has the greatest disadvantage that microvariation occurs when reaching the maximum power point and deviates from follow-up to abrupt change of the irradiation dose. In the method of linking with the system, even if it deviates from the maximum power follower, it has a strong voltage source of system, so that generation power is transmitted and recovered after a lapse of time. However, if an independent load such as a water electrolytic unit is used, it is not suitable due to the problem that the load is turned off.

When the sunshine fluctuation occurs, the MPPT control does not respond properly and the output voltage often drops. When measuring the recovery time due to the fluctuation of the sunshine caused by the cloud, It takes about 4 minutes to recover. It is also confirmed that the output voltage hunts when the water electrolytic unit is connected according to the fluctuation of the sunshine quantity.

Therefore, there is a limit to cope with sudden increase or decrease of the amount of sunshine. Therefore, the present invention improves the conventional P & O algorithm for maximum power follow-up (MPPT) against fluctuation of sunshine and power supply load. That is, the new power follow-up method is improved to improve the response to the power fluctuation due to the fluctuation of the sunshine amount.

FIG. 6 illustrates an improved P & O control method in accordance with an embodiment of the present invention.

As shown in FIG. 6, first, the current voltage V (n) and the current I (n) are measured, and the output power P (n) at this time is calculated as a product of the voltage and the current. (Difference between current power and previous power,? P = P (n) -P (n-1)) is positive or negative. When the power increment ΔP is 0, the reference voltage V _ref is not adjusted.

If the power increment ΔP is negative, the voltage increment ΔV = V (n) -V (n-1) is compared with zero. If △ V is negative, set the power point state to ④ (or 4). At this time, the reference voltage V _ref is decreased. When? V is positive, the power point state is set to? (Or 3). At this time, the reference voltage V _ref is increased.

Next, when the power increment ΔP is positive, the voltage increment ΔV = V (n) -V (n-1) is compared with zero. If ΔV is negative, first set the power point state to ② (or 2) and increase the reference voltage. Thereafter, it is set differently according to the previous power point state. That is, if the power point state is ①, ④, ⑥, set the power point state to ⑥ (or 6) and reduce the reference voltage. Otherwise, set the power point state to 2 (or 2) and increase the reference voltage.

7, the state where the power point state is ①, ④ and ⑥ is the left side at the maximum power point and the state where the power point state is ②, ③ and ⑤ is the right side at the maximum power point .

When? V is positive, the power point state is first set to 1 (or 1) and the reference voltage is decreased. Thereafter, it is set differently according to the previous power point state. That is, if the power point state is ②, ③, ⑤, the power point state is set to ⑤ (or 5) and the reference voltage is increased. Otherwise, set the power point state to 1 (or 1) and reduce the reference voltage.

That is, as shown in FIG. 7, the P & O control algorithm according to the present invention is configured to refine the steps of the conventional algorithm to improve the response of the power converter according to the generated power variation. That is, the P & O control algorithm is improved by applying the ⑤ and ⑥ sections in contrast to the C in Fig. 5 where the generated power fluctuation is severe. This makes it possible to optimally respond to power fluctuations.

5, and 6 will be described in more detail with reference to FIG.

In FIG. 8, the maximum power follow-up time is divided into left and right based on red as a judgment of voltage fluctuation. When the voltage P rises, it is compared with the past value. If the voltage V rises, it is on the left side, and when the voltage V decreases, on the right side.

That is, when the voltage rises, the power is followed as shown in (1) in FIG. 8 (a), and when the voltage is decreased, the power is followed as shown in (2) in FIG. 8 (b). In Fig. 8 (c), ④ is a voltage reduction period due to fluctuation of generated power at the maximum power point, and ③ is a voltage rising period due to fluctuation of generated power at the maximum power point.

The above ① ~ ④ are the same in the existing P & O algorithm to distinguish the left or right at the maximum power point and the voltage increase and decrease conditions according to the voltage judgment in order to cope with the fluctuation of the sunshine amount.

[Existing P & O Algorithm] From the condition P (n) -P (n-1)> 0 to the lower condition V (n) -V (n-1)> 0

If yes, increase the voltage; if no, decrease the voltage.

[Improvement P & O Algorithm] The condition P (n) -P (n-1) >

If yes, increase the voltage; if no, decrease the voltage.

In order to overcome the delay of the response of power fluctuation which is the biggest disadvantage of P & O, the conventional algorithm judges and controls in order to check the power fluctuation due to the fluctuation of the sunshine amount. That is, if the voltage is simply changed without judging by the fluctuation of the amount of sunshine, a voltage hunting phenomenon occurs.

In the present invention, the control algorithm is added to the existing P & O algorithm in order to cope with the fluctuation in the amount of sunshine, as shown in (d) and (e) of FIG. As shown in (d) and (e) of FIG. 8, according to the voltage rise judgment, the left side and the right side are divided based on the maximum power point.

In (d) of FIG. 8, in the determination of the voltage reduction period, when the amount of sunshine fluctuates, the voltage rise is determined to be?. In this case, the voltage is immediately raised and the voltage is not decreased to follow the maximum power point. Continue to increase the voltage to check the state of the sunshine variation as described above. Then, it is judged that the fluctuation of the sunshine is the voltage, and if it is the decrease period, the voltage is decreased as shown in ②, and the maximum power point is followed. If the amount of sunshine is reduced here, it is judged as ④ and it operates.

In (e) of FIG. 8, in the determination of the voltage rising period, if the voltage decreases due to the variation in the amount of sunshine, it is determined to be?. In this case, the voltage is not reduced but the voltage is not immediately increased. Instead, the voltage is decreased in order to confirm the fluctuation of the sunshine quantity, and when the sunshine variation is judged as the voltage, the maximum power point is followed by increasing the voltage as shown in (1). If the amount of sunshine increases here, it is judged as ③ and it operates.

The left and right judgment criteria based on the maximum power point are determined by supplying power and following the maximum power according to the variation of the voltage.

On the other hand, the water electrolyzer has the minimum voltage that can produce hydrogen. Further, the maximum voltage is set for preventing deterioration of the electrode or the insulating film.

Between the minimum voltage and the maximum voltage as described above, PWM switching moves to step. For example, assume that P (n-1) = 1000W, V (n-1) = 39V, P (n) = 800W, and V (n) = 37V. At this time, if the voltage of the current value is decreased by 2V and the step is set to 100 because of the past value, the PWM switching is performed by reducing to 2/100 = 0.02V. In addition, when the voltage increases, PWM switching is performed to increase by 0.02V.

The size of this step can be adjusted while checking the power fluctuation and the transient voltage of the water electrolytic device which is a load in a steady state. If the transient is bad, the step value is set to 200 and the voltage is increased or decreased to 0.01V. The step value fluctuates between the maximum voltage and the minimum voltage setting that can produce hydrogen.

When the power generation amount decreases and reaches the minimum voltage, the current continuously decreases from this point.

9 is an explanatory diagram of the operation of the PI controller. The PI controller controls the actual PV direct voltage (V _pv ) to the target value according to the reference voltage (V _ref ) generated by the improved P & O algorithm. That is, power calculation is first performed by MPPT first, and secondarily ripple is removed. It also has voltage and current limit functions to supply stable voltage and current to the load. In addition, it consists of a control circuit for supplying power to the power receiving device by operating a semiconductor device by PWM switching through a PI controller.

Next, a step S20 of selecting the water electrolytic solution 50 and supplying electric power will be described with reference to Fig.

First, as shown in FIG. 10A, when the generated power increases, the power receiving apparatus is further supplied with power.

The solar power can not make the total power generation required at the same time of the sunrise (the power receiver). Therefore, the output switch of the power converter is turned on to one of the power receiving devices 50 connected in parallel to supply power to the power receiving device. At this time, as described above, the power with maximum power follow-up (MPPT) is supplied. In addition, since the water electrolytic solution 50 needs a minimum voltage capable of producing hydrogen as shown in Formula 5, the control unit 40 may supply power to the second or more water electrolysis devices 50 according to the generated electric power of the sunlight. Can be determined.

That is, when more electric power is produced by comparing the generated electric power, the output switch is further turned on to operate more of the water electrolytic apparatus 50. This process is repeated to supply power to the water electrolytic solution 50. In other words, the switch-on state can be sequentially set through the maximum power estimation of the renewable energy generation amount at the time when the amount of sunshine increases.

The concrete steps are as follows.

1) Verify that the developed voltage is increased for initial start-up.

2) The cumulative operation time of the water electrolytic solution is compared, and the switch n (the first) having a small accumulated operation time is turned on.

3) The DC / DC converter powers the load while performing MPPT.

4) If the load supply power is 90% based on the connected load, turn on the switch n with the second operation time less. For example, if the generated power is constant at 90% on a single load basis, the load is powered by 45%.

5) Supply power to the load while MPPT according to power generation variation. At this time, when the power generation amount is 90% based on two loads, the third output switch n is turned on. That is, the current generation amount is 90% × 2 = 180%. When three loads (power dissipation devices) are shared, 180% / 3 units = 60%. That is, the load by each water electrolytic device supplies power at the level of 60%.

6) Supply power to the load according to the increased power generation. In addition, when the generated power becomes the maximum, the load capacity can be increased due to the increase in efficiency. In this case, by controlling the maximum output voltage of the load, the durability due to deterioration due to the overvoltage of the power receiver is prevented.

Next, as shown in FIG. 10B, when the generated power decreases, some of the power-receiving units to which power is supplied are selected and the power is cut off stepwise.

In addition, the control unit 40 compares the renewable energy generation power and the load power in real time, and if the renewable energy generation power is insufficient relative to the load power consumption amount of the water electrolytic apparatus 50 necessary for producing hydrogen, The converter output switch 30 is turned off and power is supplied to the remaining water receiver load. Further, when the generated power is insufficient, the output switch 30 is further turned off to minimize the surplus power of the renewable energy to produce hydrogen.

That is, the control unit 40 compares the photovoltaic generation power with the power required by the power receiving unit 50 at a time when the generated power decreases, as opposed to the time when the generated power increases, and turns off the power converter output switch And supplies power to the remaining water electrolytic solution 50. By repeating this process, the output switch is further turned off according to the generated power to minimize the surplus power of the sunlight to produce hydrogen.

The concrete steps are as follows.

7) If the power generation is reduced to 50% of the total load, turn off the most used water electrolyzer switch n. For example, since three units are operating, 50% x 3 units = 150%. One of them is stopped and the rest is divided into two, so 150% / 2 = 75%. That is, power is supplied to two units at 75% of the load power consumption.

8) If the remaining two loads become 50% due to the decrease in power generation, turn off the most used water electrolyzer n.

9) The remaining one unit is operated at a 100% load, and the power consumption of the load decreases as the generation power decreases.

10) Turn the DC / DC converter off when it is the minimum voltage of the last one power take-off.

On the other hand, the control unit 40 counts the operation time of each of the power receiving units 50, and controls the power receiving units 50 to operate in an intersecting manner. Accordingly, the operation time of the plurality of power receiving units 50 installed according to the amount of renewable energy generation is maintained in a similar manner. The durability of the water electrolysis apparatuses 50 can be uniformly provided through the above-described cross operation method.

Specifically, the water electrolytic apparatus 50 of the solid polymer electrolyte (PEM) type is composed of a positive electrode, a negative electrode, and an ion exchange membrane. The ion exchange membrane has an electrolyte function that separates hydrogen and oxygen and moves them from the anode to the cathode. Since the ion exchange membrane is a strong acid electrolyte, a platinum series which is an acid-resistant noble metal catalyst is widely used. Since the catalyst uses a precious metal material such as platinum or iridium, durability is important.

In addition, deterioration of the electrode and insulating film due to overvoltage and overvoltage greatly influences the hydrogen yield, and in the durability, the oxygen generating anode catalyst technology directly influences performance. Thus, by restricting the overvoltage through control over the DC / DC converter 20, deterioration due to the overvoltage can be prevented.

However, the durability of ion exchange membranes and precious metal catalysts due to the use of water electrolytic devices can not be protected by the power converter. Therefore, in order to protect the chemical safety due to durability and to maintain the yield, the power is supplied according to the total operation time (or cumulative operation time) of the water electrolysis apparatus 50 through the output switch 30 connected to the water electrolysis apparatus 50 And controls the selection of the device 50.

That is, in the time zone where the generated power increases due to the increase in the amount of sunshine, the power-receiving device 50 having a small cumulative operation time is preferentially selected and the power is supplied. On the contrary, in the time period during which the generated power decreases, the power receiving device 50 having a large cumulative operation time is preferentially selected and the power supply is stopped. That is, the cumulative operation time of the water electrolytic solution 50 is checked according to the generated power amount, and the durability is controlled to be maintained.

In summary, each switch on time for power supply to the water electrolytic apparatus 50 as a load is cumulatively counted. Therefore, the total cumulative operation time of each water electrolytic apparatus 50 is monitored, and the cumulative operation time is selected as described above when selecting the electrolytic apparatus 50 to supply or block the electric power.

Next, a solar-light-based hydrogen electrolysis apparatus according to a second embodiment of the present invention will be described with reference to FIG.

The second embodiment of the present invention is the same as the first embodiment. However, the second embodiment differs in the step S20 of turning on / off the water electrolytic solution 50. Only the different parts are described below. Unless explained, the description of the first embodiment described above is referred to.

11, the control unit 40 divides the power P _out supplied to the power receiving unit 50 by the number n of the power receiving units currently connected, and then divides the divided power (that is, power shared in parallel) Is greater than the power P ₁ (S21). That is, it is determined whether the following expression (7) is satisfied.

&Quot; (7) "

If Equation (7) is satisfied, one of the water electrolytic solution apparatus 50 is selected (S22), and the selected water electrolytic apparatus 50 is added (S23). At this time, the water electrolytic water treatment apparatus 50 having the smallest cumulative operation time is selected.

Here, P ₁ represents the maximum power applied to one of the water electrolytic devices 50. As described above, when too large voltage and current are supplied to the water electrolytic solution 50, durability due to deterioration is reduced. Therefore, the appropriate power at which deterioration is minimized is set to the maximum power.

n is the number of the water electrolysis devices 50 connected in parallel. Therefore, dividing the supply power P _out by n is the power supplied to one of the power receiving units connected in parallel. If this power is greater than the maximum power P ₁ , there is room for degradation to proceed, thus adding one more power receiver to lower the power supply.

If the equation (7) is not satisfied, the control unit 40 divides the power P _out by the number n of the power receiving apparatuses currently connected and determines whether the divided power sharing is less than the minimum power P ₀ (S24). That is, it is determined whether the following expression (8) is satisfied.

&Quot; (8) "

If Equation (8) is satisfied, one of the water electrolytic dissolution apparatus 50 is selected (S25), and the selected water electrolytic dissolution apparatus 50 is shut off (S26). At this time, the water electrolytic water treatment apparatus 50 in which the accumulated operation time is the maximum is selected.

Here, P ₀ is set in advance as the minimum power to be applied to one of the water electrolysis apparatuses 50. As described above, when too little power (or voltage) is applied to the water electrolytic solution 50, no chemical reaction occurs and hydrogen is not produced. Therefore, the power required for hydrogen production is preset to the minimum power P ₀ .

n is the number of the water electrolysis devices 50 connected in parallel. Therefore, dividing the supply power P _out by n is the power supplied to one of the power receiving units connected in parallel. If this power is less than the minimum power P ₀ , the hydrogen production may be interrupted, thereby turning off at least one of the power receiving devices in operation to increase the power supply of the remaining power receiving devices.

Next, a solar-light-based hydrogen electrolysis apparatus according to a third embodiment of the present invention will be described.

The third embodiment of the present invention is the same as the first embodiment described above, and differs in that an auxiliary power source is additionally used. Only the different parts are described below. Unless explained, the description of the first embodiment described above is referred to.

When the power converter is driven only by the renewable energy, the power converter can be automatically stopped due to a lack of control power required for driving the power converter when the generated power of the renewable energy is changed rapidly. In order to prevent this, it is necessary to install the renewable energy generating capacity at a capacity that does not exceed the transient range of the control power source. However, this causes surplus power as compared with the load capacity.

Therefore, as shown in FIG. 1, the control power source necessary for driving the power converter constitutes a new renewable energy generation power and a separate external power source in parallel. Therefore, when the power of the renewable energy is used as the control power source and the power of the renewable energy generation is compared in real time, when the power of the control power source is insufficient, the circuit is automatically configured to be supplied to the auxiliary power source.

Although the invention made by the present inventors has been specifically described according to the above embodiments, the present invention is not limited to the above embodiments, and it goes without saying that the present invention can be modified in various ways without departing from the gist of the present invention.

10: Solar power generating part 20: DC / DC converter
30: Switching unit 40:
50: water electrolytic device 60: storage device

Claims (5)

A method of controlling and operating a power converter for power supply of a hydrogen-electrolytic device using sunlight, the method comprising: converting input power of a solar power generator into a DC / DC converter and controlling supply of the power to at least two power- In this case,
(a1) receiving the current voltage and current of the solar power generation unit;
(a2) whether the power increment is negative or positive, whether the voltage increment is negative or positive, and a result of the combination of the current power point state and the current power point state according to the previously set power point state, Increasing or decreasing the reference voltage;
(a3) generating a PWM control signal of the DC / DC converter through PI (proportional integral) control according to the increased or decreased reference voltage; And
(b) controlling power supply by turning on / off at least some of the at least two power receiving devices according to the magnitude of the power output to the power receiving device,
In the step (a2)
In order to follow the maximum power point, the previous power point state is set to the voltage rising state when the voltage is in the raised state (hereinafter referred to as the voltage rising state), even if the power increment is positive and the voltage increment is negative,
If the previous power point state is a state where the voltage is decreasing (hereinafter referred to as a voltage decreasing state) in order to follow the maximum power point, setting the current power point state to the voltage decreasing state even if the power increment is positive and the voltage increment is positive A method of controlling and operating a power converter for powering a hydrogen electrolysis apparatus using solar light.
The method according to claim 1,
Setting the current power point state to a fourth state if the power increment is negative and the voltage increment is negative in step (a2); and if the power increment is negative and the voltage increment is positive, The third state is set,
If the power increment is positive and the voltage increment is negative, the current power point state is set to a sixth state if the previous power point state is in a voltage up state, otherwise the current power point state is set to a second state ,
If the power increment is positive and the voltage increment is positive, sets the current power point state to the fifth state if the previous power point state is in the voltage decrease state, otherwise sets the current power point state to the first state ,
If the power point state is the first, fourth, or sixth state, and if the power point state is the second, third, or fifth state,
The reference voltage is decreased when the current power point state is set to the first, fourth, and sixth states, and the reference voltage is increased when the current power point state is set to the second, third, and fifth states A method of controlling and operating a power converter for powering a hydrogen electrolysis apparatus using solar light.
The method according to claim 1,
In the step (b), if the electric power supplied to the water electrolytic apparatus (hereinafter referred to as supplied electric power) is divided by the number of the water electrolytic apparatuses currently connected and the divided electric power is greater than the predetermined maximum electric power, One of the devices is selected and added, and when the divided electric power is smaller than the preset minimum electric power, one of the on-powered devices is selected and turned off A method of controlling and operating a power converter for powering a hydrogen electrolysis apparatus using solar light.
The method of claim 3,
In the step (b), when selecting one of the power-receiving devices turned off to turn on, the power-receiving device having the smallest accumulated use time is selected and turned on to turn off and selecting a water electrolysis apparatus having a maximum cumulative use time when selecting one of the water electrolysis apparatuses that are turned on when the water electrolysis apparatus is turned on. .
The method according to claim 1,
Wherein in the step (b), it is determined whether the voltage developed for the initial startup is high, and when the voltage is increased, one of the electrolytic electrolysis devices is selected and turned on. Control and operation of a power converter for powering a device.

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