JP7275868B2 - Water electrolysis device abnormality diagnosis program and water electrolysis system - Google Patents

Description

TECHNICAL FIELD The present invention relates to a water electrolysis device abnormality diagnosis program and water electrolysis system, and more particularly, to a water electrolysis device for diagnosing whether or not a micro-short has occurred in a polymer electrolyte membrane type (PEM type) water electrolysis stack. The present invention relates to an abnormality diagnosis program and a water electrolysis system equipped with such a program.

Water electrolyzers include water electrolyzers using polymer electrolyte membranes as diaphragms (PEM water electrolyzers), water electrolyzers with alkaline electrolytes partitioned by partitions, and high-temperature water electrolyzers using solid oxides as electrolytes. etc. are known. Among these, the PEM type water electrolyzer has advantages such as being able to generate hydrogen using only water, containing no impurities other than water in the hydrogen gas, and operating at a low temperature.

The PEM type water electrolyzer has the same structure as the polymer electrolyte fuel cell, except that the application is different. That is, the PEM type water electrolysis apparatus includes a membrane electrode assembly (MEA) in which electrodes including catalyst layers are joined to both surfaces of an electrolyte membrane. Electrodes generally have a two-layer structure of a catalyst layer and a diffusion layer. Both sides of the MEA are further provided with current collectors (separators) having channels for circulating gas and water. A PEM type water electrolysis device usually has a structure (stack structure) in which a plurality of single cells each including such an MEA and a current collector are laminated.

When the PEM type water electrolysis device is repeatedly started and stopped, the temperature, pressure and/or water content of the electrolyte membrane fluctuate during that time, and the electrolyte membrane repeatedly swells and shrinks. Since a nonwoven fabric made of carbon fiber or metal fiber (for example, Ti fiber) is often used for the diffusion layer, when the electrolyte membrane repeatedly swells and contracts, the conductive fibers constituting the diffusion layer pierce the electrolyte membrane. happens. In particular, since metal fibers are very fine and hard, they are easily pierced.

A “micro-short” refers to a state in which a conductive substance (eg, conductive fibers forming a diffusion layer) penetrates an electrolyte membrane to electrically connect an oxygen electrode and a hydrogen electrode. If the electrolyte membrane is made thinner in order to increase the efficiency of water electrolysis, the probability of occurrence of such micro-shorts increases. When a micro-short occurs, an electric current flows through the conductive fibers during electrolysis, generating heat, and burning of the electrolyte membrane around the conductive fibers progresses. As a result, pinholes are formed in the electrolyte membrane. When a pinhole is formed, there is a problem that water or gas leaks from one electrode side toward the other electrode side.

In order to solve this problem, various proposals have been conventionally made.
For example, in Patent Document 1, in a solid polymer electrolyte membrane water electrolysis device in which a normal operating voltage is applied between an anode and a cathode by a main power supply device,
(a) suspending the main power supply and applying a pinhole detection voltage between the anode and the cathode by the auxiliary power supply;
(b) detecting the voltage between the anode and the cathode when the pinhole detection voltage is applied;
(c) A method for detecting pinholes in a solid polymer electrolyte membrane is disclosed which compares the detected voltage with a preset threshold voltage.

In the same document,
(A) When pinholes are not generated in the solid polymer electrolyte membrane, the voltage between the anode and the cathode is equal to the voltage applied to the auxiliary power supply, whereas pinholes are generated in the solid polymer electrolyte membrane. When the electrons flow through the solid polymer electrolyte membrane, the voltage between the anode and the cathode becomes a value smaller than the voltage applied to the auxiliary power supply, and
(B) It is described that the generation of pinholes can be detected by detecting the voltage between the anode and the cathode.

In order to prevent serious failure of the water electrolysis device, it is desirable to detect and determine abnormality at an earlier stage (that is, at the stage at which micro-shorts occur before pinholes are formed). However, there is no conventional example in which a method capable of accurately detecting the presence or absence of a micro-short has been proposed.
Patent Document 1 discloses a method of detecting the occurrence of pinholes using only voltage changes. However, this method is only a method of indirectly estimating the resistance value only from the voltage, and there is a possibility of misjudgment. It is difficult to predict the resistance from the single index of voltage, which is affected by crossover and gas permeation. In particular, when the gas pressure in the electrode changes (in a practical water electrolysis system, the hydrogen electrode pressure is high, but the pressure is not necessarily stable), the threshold value changes depending on the pressure. The method cannot detect micro-shorts.

Japanese Patent Application Laid-Open No. 2006-138004

The problem to be solved by the present invention is to provide a water electrolysis device abnormality diagnosis program capable of accurately detecting the presence or absence of micro-shorts in a water electrolysis system having a plurality of PEM type water electrolysis stacks. It is in.
Another problem to be solved by the present invention is to provide a water electrolysis system equipped with such a water electrolysis device abnormality diagnosis program.

In order to solve the above problems, a water electrolysis device abnormality diagnosis program according to the present invention is for causing a computer to execute the following procedures.
(A) In a water electrolysis system provided with n (n ≥ 1) PEM type water electrolysis stacks consisting of m (m ≥ 2) single cell laminates, the i-th PEM type water electrolysis stack (1 ≤ i ≤ n) is stopped.
(B) When the stop of the iPEM type water electrolysis stack is detected, electrolysis is performed using an auxiliary power supply for the j-th single cell (1≤j≤m) included in the iPEM type water electrolysis stack. The k-th voltage V _i,j,k (1 ≤ k ≤ p, p ≥ 1) at which neither reaction nor fuel cell reaction occurs is applied in the same direction as during electrolysis, and the V _i,j,k is stored in the memory. Procedure B for memorization.
(C) using a current detection device to detect the kth current Ii _,j,k of the jth single cell corresponding to the Vi _,j,k, and storing the Ii _,j,k in the memory; Procedure C for memorizing.
(D) Calculate the resistance R _i,j,k of the j-th unit cell from the k-th voltage V i _{,j,k and the k-th current I i ,j,k,} and calculate the R _i,j,k as Procedure D for storing in memory.
(E) In the case of p≧2, when calculating a plurality of R _i,j,k , a procedure E in which the procedures B to D are repeated (p−1) times.
(F) Step F of notifying that there is an abnormality in the i-PEM water electrolysis stack when at least one of Ri _,j,k or a combination thereof is equal to or less than the threshold value _Rc .

A water electrolysis system according to the present invention has the following configuration.
(1) The water electrolysis system is
n (n≧1) PEM type water electrolysis stacks with m (m≧2) single cells;
a main power source that individually supplies power to the i PEM type water electrolysis stack (1≤i≤n);
a water supply device for simultaneously or individually supplying water to the oxygen electrodes of the iPEM water electrolysis stack;
an auxiliary power supply that applies a voltage for abnormality diagnosis to the j-th unit cell (1≤j≤m) included in the i-th PEM water electrolysis stack when the i-th PEM water electrolysis stack is stopped;
a voltage detection device for detecting the voltage applied to the j-th single cell;
a current detection device that detects the current flowing through the j-th single cell;
and a control device for controlling the water electrolysis system.
(2) The controller stores a water electrolysis device abnormality diagnosis program according to the present invention.

When the PEM type water electrolysis stack is stopped, when a predetermined voltage V is applied to each single cell included in the PEM type water electrolysis stack and the current I flowing through the single cell is detected, from the applied voltage V and the current I , the resistance value R between the electrodes of the single cell can be calculated.
The voltage V alone is susceptible to current generation factors other than micro-shorts in the single cell. Insensitive. Therefore, by comparing the calculated resistance value R with the threshold value _Rc , it is possible to accurately determine whether or not a micro-short has occurred.

It is a cross-sectional schematic diagram of a single cell. 1 is a schematic diagram of a water electrolysis system according to the present invention; FIG. 1 is a schematic diagram of a water electrolysis system with multiple PEM type water electrolysis stacks; FIG. It is an example of measurement results of current I when different voltages V are applied to a normal j-th single cell and a j-th single cell in which a micro-short has occurred.

It is an example of the measurement results of the resistance R when different voltages V are applied to the j-th unit cell in which micro-shorting occurs. FIG. 3 is a flowchart of a water electrolysis device abnormality diagnosis program according to the present invention; 7 is a continuation of the flow diagram shown in FIG. 6. FIG. FIG. 10 is a flow chart of a procedure for applying the k-th voltage V _i,j,k .

An embodiment of the present invention will be described in detail below.
[1. PEM type water electrolysis stack]
FIG. 1 shows a schematic cross-sectional view of a single cell. In FIG. 1, the single cell 22 includes a membrane electrode assembly (MEA) 24 and an oxygen electrode side separator 34 and a hydrogen electrode side separator 36 arranged on both sides of the MEA 24 . The MEA 24 also includes an electrolyte membrane 26 and an oxygen electrode 28 and a hydrogen electrode 30 bonded to both sides of the electrolyte membrane 26 .
The PEM type water electrolysis stack 20 is composed of a plurality of such single cells 22 stacked. In the present invention, the total number (m) of the single cells 22 included in the PEM type water electrolysis stack 20 is not particularly limited, and an optimal number can be selected according to the purpose. Further, when the water electrolysis system includes a plurality of PEM-type water electrolysis stacks 20, the total number (m) of the unit cells 22 included in each PEM-type water electrolysis stack 20 may be the same, or , can be different.

A solid polymer electrolyte such as perfluorocarbon sulfonic acid polymer is generally used for the electrolyte membrane 26 .
The oxygen electrode 28 has a two-layer structure of a catalyst layer 28a made of a composite of an electrode catalyst and a solid polymer electrolyte and a porous diffusion layer 28b made of a conductive material. Similarly, the hydrogen electrode 30 has a two-layer structure of a catalyst layer 30a made of a composite of an electrode catalyst and a solid polymer electrolyte and a porous diffusion layer 30b made of a conductive material. A nonwoven fabric made of conductive fibers is generally used for the diffusion layers 28b and 30b. Conductive fibers include, for example, carbon fibers, Ti fibers, stainless steel fibers, and the like.
Furthermore, the oxygen electrode side separator 34 and the hydrogen electrode side separator 36 are formed with channels for circulating gas and water, respectively.

While supplying water to the flow path of the oxygen electrode side separator 34 of such a single cell 22 (or PEM type water electrolysis stack 20), a main power supply 38 is used to apply a direct current between the oxygen electrode 28 and the hydrogen electrode 30. When flowing, the reaction of the following formula (1) proceeds on the oxygen electrode 28 side. The generated O ₂ gas is discharged to the outside through the channel in the oxygen electrode side separator 34 together with excess water. Also, the generated H ⁺ diffuses in the electrolyte membrane 26 and reaches the hydrogen electrode 30 side.
H ₂ O → 2H ⁺ + 2e ⁻ + 1/2O ₂ (1)

On the other hand, on the hydrogen electrode 30 side, the reaction of the following formula (2) proceeds. The generated H ₂ gas is discharged to the outside through the channels in the hydrogen electrode side separator 36 . At this time, if water is also circulated through the flow path in the hydrogen electrode side separator 36, the discharge of H ₂ gas is promoted.
2H ⁺ + 2e ⁻ → H ₂ (2)

When performing water electrolysis using the PEM type water electrolysis stack 20, the PEM type water electrolysis stack 20 is normally started and stopped repeatedly depending on the power situation and the amount of gas required. Repeated starting and stopping causes the conductive fibers to pierce the electrolyte membrane 26 due to deformation of the electrolyte membrane 26 and fluffing of the diffusion layers 28b and 30b.

When the conductive fibers penetrate the electrolyte membrane 26, the oxygen electrode 28 and the hydrogen electrode 30 are electrically connected through the conductive fibers, resulting in a so-called "micro-short" state. Furthermore, if electrolysis is continued with micro-shorts occurring, current also flows through the conductive fibers. As a result, the electrolyte membrane 26 around the penetrating conductive fibers is burned and pinholes are formed. If pinholes are formed, hydrogen and oxygen, which are reaction products, are mixed, and high-purity gas cannot be obtained. A micro-short is one step short of such a fatal trouble. In order to avoid fatal troubles, it is necessary to detect the occurrence of micro-shorts, which is a pre-stage of pinhole formation.

[2. Water electrolysis system]
FIG. 2 shows a schematic diagram of a water electrolysis system according to the present invention. In FIG. 2, the water electrolysis system 10 includes
n (n≧1) PEM type water electrolysis stacks 20 having m (m≧2) single cells;
a main power supply 38 that individually supplies power to the i-th PEM type water electrolysis stack 20 (1≤i≤n);
a water supply device 40 that simultaneously or individually supplies water to the oxygen electrodes of the iPEM water electrolysis stack 20;
an auxiliary power supply 60 that applies a voltage for abnormality diagnosis to the j-th single cell (1≤j≤m) included in the iPEM water electrolysis stack 20 when the iPEM water electrolysis stack 20 is stopped;
a voltage detection device 62 for detecting the voltage applied to the j-th single cell;
a current detection device 64 for detecting the current flowing through the j-th single cell;
and a control device (not shown) that controls the water electrolysis system 10 .

The water electrolysis system 10 shown in FIG.
(a) a multi-stage switch 66 for switching and supplying the applied voltage from the auxiliary power supply 60 to each j-th single cell, and/or
(b) A water circulation device 70 for circulating water to the hydrogen electrodes of the iPEM type water electrolysis stack 20 simultaneously or individually.
may be further provided.

[2.1. PEM type water electrolysis stack]
A PEM type water electrolysis stack (hereinafter also simply referred to as “stack”) 20 is composed of a stack of m (m≧2) unit cells using a polymer electrolyte membrane as a diaphragm. The details of the stack 20 are as described above, so description thereof will be omitted.
In the example shown in FIG. 2, the water electrolysis system 10 is described with one stack 20, but this is merely an example. The total number (n) of stacks 20 may be 1 or more, and the optimum number can be selected according to the purpose.
When the water electrolysis system 10 has two or more stacks 20, the number of stacks 20 to be operated and the individual to be operated can be arbitrarily selected according to the purpose.

[2.2. Main power]
A main power supply 38 is for supplying power to the stacks 20 individually. In the present invention, the type of main power supply 38 is not particularly limited. The main power supply 38 may be a commercial power supply, or may be a power supply derived from renewable energy such as sunlight and wind power.
In addition, when the water electrolysis system 10 includes a plurality of stacks 20, when only some of the stacks 20 are operated, a power regulator (not shown) is used to adjust the required power to some of the stacks. 20 distributed.

[2.3. Water supply device]
The water supply device 40 is for supplying water, which is a raw material for electrolysis, to the oxygen electrode of the stack 20 . The structure of the water supply device 40 is not particularly limited as long as it can supply the required amount of water to the oxygen electrodes of each stack 20 simultaneously or individually.

Even if water is supplied to the oxygen electrode of the stack 20, electrolysis will not occur unless power is supplied. Therefore, even if the water supply device 40 supplies water to all the stacks 20 at the same time regardless of whether the water supply device 40 is in operation, there is no problem with the electrolysis itself. However, if water is continuously supplied to the oxygen electrode side during abnormality diagnosis, the state of the oxygen electrode side may not be stable because water in which oxygen is dissolved is supplied from the gas-liquid separator. Therefore, the water supply device is one that can supply water to each stack 20 individually (in other words, one that can stop the supply of water to the stack 20 that is the object of diagnosis at the time of abnormality diagnosis). is preferred.

In FIG. 2, the water supply device 40 includes an oxygen electrode side circulation pump 42 and an oxygen electrode side gas-liquid separator 44 . The oxygen electrode side circulation pump 42 is for supplying water to the oxygen electrode of the stack 20 . In order to individually supply water to the oxygen electrodes of each stack 20 when the number of stacks 20 is two or more,
(a) An oxygen electrode side circulation pump 42 is installed for each stack 20, or
(b) It is preferable to connect one oxygen electrode side circulation pump 42 to a plurality of stacks 20 via opening/closing valves.

The oxygen electrode side gas-liquid separator 44 temporarily stores water supplied to the oxygen electrode of the stack 20, and at the same time recovers a mixture of water and oxygen gas discharged from the oxygen electrode side of the stack 20 to to separate water and oxygen gas. When there are a plurality of stacks 20 , the oxygen electrode side gas-liquid separator 44 may be installed for each stack 20 or may be shared by the plurality of stacks 20 .

The inlet of the oxygen electrode side circulation pump 42 is connected to the drain port of the oxygen electrode side gas-liquid separator 44 via a pipe 46a. The pipe 46a is provided with a drain valve 48a for discharging water. The outlet of the oxygen electrode side circulation pump 42 is connected to the inlet of the oxygen electrode side manifold (not shown) of the stack 20 via a pipe 46b.

A waste water introduction port of the oxygen electrode side gas-liquid separator 44 is connected to an outlet of an oxygen electrode side manifold (not shown) of the stack 20 via a pipe 46c. A water supply port of the oxygen electrode side gas-liquid separator 44 is connected to a raw water supply source (not shown) via a pipe 46d. A water supply valve 48b is provided on the pipe 46d.
An exhaust port of the oxygen electrode side gas-liquid separator 44 is connected to an oxygen consumption source (not shown) via a pipe 46e, or is open to the atmosphere. A pressure gauge 50 is provided in the pipe 46e.

[2.4. Auxiliary power]
The auxiliary power supply 60 applies a voltage for abnormality diagnosis to the j-th single cell (1≤j≤m) included in the i-PEM water electrolysis stack 20 when the i-th PEM-type water electrolysis stack (1≤i≤n) 20 is stopped. is for applying
The auxiliary power supply 60 is not particularly limited as long as it can apply a voltage for abnormality diagnosis to the j-th single cell. In order to accurately diagnose the abnormality of the j-th single cell, it is preferable that the auxiliary power supply 60 have a capacity corresponding to the size of the j-th single cell.
If the main power supply 38 is a wide-range power supply, that is, if it is possible to apply a voltage suitable for abnormality diagnosis, instead of installing a separate auxiliary power supply 60, the main power supply 38 can also be used as the auxiliary power supply 60 .

[2.5. Voltage detection device and current detection device]
The voltage detection device 62 is for detecting the voltage applied to the j-th single cell. Also, the current detection device 64 is for detecting the current flowing through the j-th single cell. The voltage detection device 62 and current detection device 64 are not particularly limited as long as they can detect the voltage and current of the j-th single cell.
For example, the voltage detection device 62 and the current detection device 64 may be installed separately from the auxiliary power supply 60 . Alternatively, some power supplies that can be used as auxiliary power supply 60 include voltage and current sensing devices. In such a case, devices built into the auxiliary power supply 60 may be used as the voltage detection device 62 and the current detection device 64 .

[2.6. Multistage switch]
The water electrolysis system 10 may include a multistage switch 66 for switching and supplying the applied voltage from the auxiliary power supply 60 to each j-th single cell. For example, if the total number (m) of single cells included in the stack 20 is relatively small, the auxiliary power supply 60 can be installed for each single cell. However, as the total number (m) of single cells increases, it becomes more difficult to install the auxiliary power supply 60 for each single cell. In such a case, it is preferable to use the multistage switch 66 to switch the applied voltage from the auxiliary power supply 60 to each single cell. The structure of the multistage switch 66 is not particularly limited as long as it has such a function.

[2.7. Water circulation device]
The water electrolysis system 10 may further include a water circulator 70 for circulating water to the hydrogen electrodes of the iPEM type water electrolysis stack 20, either simultaneously or individually. When electrolyzing water, it is not always necessary to supply water to the hydrogen electrode side. However, if water is circulated to the hydrogen electrode side, it is possible to promote detachment of hydrogen gas from the hydrogen electrode.

In addition, if hydrogen gas remains in the hydrogen electrode at the time of abnormality diagnosis, there is an advantage that the potential of the hydrogen electrode can be maintained at 0 V.
(a) the possibility of hydrogen embrittlement of the member increases;
(b) the hydrogen electrode member is excessively reduced due to the reducing power of hydrogen (leading to deterioration in performance and life);
(c) Hydrogen may permeate the counter electrode and reduce the oxygen electrode member. In such a case, it is preferable to circulate water to the hydrogen electrode side and discharge residual hydrogen gas from the hydrogen electrode.

In FIG. 2, the water circulation device 70 includes a hydrogen electrode side circulation pump 72 and a hydrogen electrode side gas-liquid separator 74 . The hydrogen electrode side circulation pump 72 is for supplying water to the hydrogen electrode of the stack 20 . In order to individually circulate water to the hydrogen electrodes of each stack 20 when the number of stacks 20 is two or more,
(a) A hydrogen electrode side circulation pump 72 is installed for each stack 20, or
(b) It is preferable to connect one hydrogen electrode side circulation pump 72 to a plurality of stacks 20 via open/close valves.

The hydrogen electrode side gas-liquid separator 74 temporarily stores the water to be circulated to the hydrogen electrode of the stack 20, and at the same time recovers the mixture of water and hydrogen gas discharged from the hydrogen electrode side of the stack 20, and separates the mixture. It is for separating water and hydrogen gas. When there are a plurality of stacks 20 , the hydrogen electrode side gas-liquid separator 74 may be installed for each stack 20 or may be shared by the plurality of stacks 20 .

The inlet of the hydrogen electrode side circulation pump 72 is connected to the drain port of the hydrogen electrode side gas-liquid separator 74 via a pipe 76a. The pipe 76a is provided with a drain valve 78a for discharging water and a flow stop valve 78b. The flow stop valve 78b is for preventing hydrogen and water from flowing back into the stack 20 when the flow path sealing is insufficient when the pump 72 is stopped. By providing the flow stop valve 78b in the pipe 76a, it is possible to prevent the in-plane conditions such as the in-plane temperature distribution in the hydrogen electrode from becoming unintended due to the reverse flow of hydrogen or water. The outlet of the hydrogen electrode-side circulation pump 72 is connected to the inlet of the hydrogen electrode-side manifold (not shown) of the stack 20 via a pipe 76b.

A drain inlet of the hydrogen electrode side gas-liquid separator 74 is connected to an outlet of a hydrogen electrode side manifold (not shown) of the stack 20 via a pipe 76c.
A drain port of the hydrogen electrode side gas-liquid separator 74 is connected to the oxygen electrode side gas-liquid separator 44 via a pipe 76d. Further, the pipe 76d is provided with a needle valve 78c and a water transfer line intermediate valve 78d. When water electrolysis is performed, up to about five water molecules move from the oxygen electrode to the hydrogen electrode accompanied by protons moving in the electrolyte membrane. The pipe 76d is for returning a large amount of water that has moved to the hydrogen electrode side to the oxygen electrode side.

The needle valve 78c is for avoiding rapid movement of water from the hydrogen electrode side gas-liquid separator 74 to the oxygen electrode side gas-liquid separator 44 . In particular, when a back pressure valve (not shown) is provided on the downstream side of the flow meter 84 to increase the pressure in the hydrogen electrode, when the water transfer line intermediate valve 78d is opened, water is rapidly released into the oxygen electrode side gas-liquid separator. 44, the pressure in the hydrogen electrode may drop rapidly. Sudden pressure changes may accelerate deterioration of the stack 20 . With the needle valve 78c, such sudden pressure changes can be suppressed.

The water transfer line intermediate valve 78 d is provided between the hydrogen electrode and the oxygen electrode side gas-liquid separator 44 to reuse the water that has moved to the hydrogen electrode due to the electrode reaction for the electrode reaction. The presence of the water transfer line intermediate valve 78d can suppress gas mixing between the hydrogen and oxygen electrodes. Moreover, when there is a pressure difference between the hydrogen electrode and the oxygen electrode, the pressure difference can be maintained.

An exhaust port of the hydrogen electrode side gas-liquid separator 74 is connected to a hydrogen consumption source (not shown) through a pipe 76e. Furthermore, a dehumidifier 80, a pressure gauge 82, and a flow meter 84 are provided on the pipe 76e.

[2.8. Control device]
A controller (not shown) is for controlling the operation of the water electrolysis system 10 . The controller, in addition to means for controlling the general operation of the water electrolysis system 10, has means for detecting micro-shorts in the jth single cell. The details of the means for detecting micro-shorts will be described later.

[2.9. Multi-phase water electrolysis system]
FIG. 3 shows a schematic diagram of a water electrolysis system with a plurality of PEM type water electrolysis stacks. In FIG. 3 , the water electrolysis system 10 ′ includes a total of 12 stacks 20 , main power supply 38 , power regulator 52 , secondary battery 54 and hydrogen tank 56 .

As described above, the number of stacks 20 to be operated and the individuals to be operated can be arbitrarily selected according to the purpose. In the example shown in FIG. 3, a total of four stacks 20 are operated. Regardless of the number of active stacks 20 , hydrogen gas produced at the hydrogen electrodes of active stacks 20 is stored in hydrogen tank 56 .
Note that oxygen is generated at the oxygen electrode of the stack 20 during electrolysis. The produced oxygen is normally discharged into the atmosphere, but the produced oxygen may be stored in an oxygen tank (not shown) and used for other purposes.

Power conditioner 52 is for distributing all or part of the power supplied from main power supply 38 to any one or more of stacks 20 . A secondary battery 54 is connected to the power regulator 52 . The secondary battery 54 is for temporarily storing surplus power when the supply and demand balance between power and hydrogen is lost. The power stored in the secondary battery 54 is supplied to the stack 20 and used for electrolysis when the power runs short.
Other points regarding the water electrolysis system 10′ are the same as those of the water electrolysis system 10 shown in FIG. 2, so description thereof will be omitted.

[3. Macro short detection method]
A micro-short detection method according to the present invention includes the following steps.
(a) In the water electrolysis system 10 provided with n (n≧1) PEM type water electrolysis stacks 20 consisting of m (m≧2) single cell laminates, the i-th PEM type water electrolysis stack 20 _i ( 1.ltoreq.i.ltoreq.n) is stopped.
( _b ) When it is detected that the i-th PEM type water electrolysis stack _20i is stopped, the _auxiliary power supply 60 to apply the k-th voltage V _i,j,k (1≤k≤p, p≥1) in the same direction as during electrolysis, at which neither the electrolytic reaction nor the fuel cell reaction occurs.
(c) using a current detection device to detect the k-th current I i,j,k of the j-th single cell 22 _j corresponding to V _{i ,j,k} ;
(d) Step d of calculating the resistance R i _,j, k of the j-th single cell 22 _j from the k-th voltage V _i,j,k and the k-th current I _i,j,k .
(e) Step e of repeating steps (b) to (d) further (p−1) times when calculating a plurality of R _i,j,k when p≧2.
(f) determining whether at least one or a combination of R _i,j,k is less than or equal to threshold R _c ;

[3.1. step a]
First, in the water electrolysis system 10 provided with n (n≧1) PEM type water electrolysis stacks 20 consisting of m (m≧2) single cell laminates, the i-th PEM type water electrolysis stack 20 _i (1 ≤i≤n) is stopped (step a).
The i-th stack _20i must be stopped in order to determine the presence or absence of a micro-short. This is because the current value flowing through the micro-shorted portion is weaker than the total current value flowing during electrolysis.

For example, assume that a cell with an area of 400 cm ² is pierced by a fiber with a resistance of 0.3Ω. When the electrolysis conditions are current density: 3 A/cm ² and voltage: 2 V, the total current is 400 cm ² ×3 A/cm ² =1200A. On the other hand, the current flowing through the fiber is 2V/0.3Ω=0.7A, which is only 0.6% of the total current. Therefore, it is difficult to detect the presence or absence of micro-shorts based on current changes during electrolysis.

To solve this problem, it is also conceivable to measure AC resistance. However, even if the AC resistance measurement is performed, it is still undetectable. In addition, since the hydrogen concentration is not affected immediately even if puncture occurs, it is not possible to judge the puncture based on the amount of gas permeation. Furthermore, since the drop in overall efficiency due to sticking is slight, and the resulting heat release is small, it is not possible to determine the presence or absence of sticking from changes in cell temperature.

Therefore, it is necessary to stop the i-th stack 20 _i to be inspected in order to determine the presence or absence of sticking. In a multi-phase system as shown in FIG. 3, only the i-th stack 20 _i to be inspected can be intentionally stopped without stopping the entire system. Therefore, a multiphase system is well suited as a system for performing such deterioration determination.

Immediately after the electrolysis of the i-th stack _20i is stopped, it is preferable to continue supplying water by the oxygen electrode side circulation pump 42 for a certain period of time to discharge oxygen gas from the oxygen electrode. This is because when a voltage for abnormality diagnosis is applied to the j-th single cell 22 _j in a state in which oxygen gas remains on the oxygen electrode side and hydrogen remains on the hydrogen electrode side, the current is likely to flow (for example, an electrolytic reaction or a fuel cell reaction may occur). An optimum time can be selected for the time during which the water on the oxygen electrode side is continuously supplied, depending on the purpose. Generally, when the same pump output as that during the electrolysis reaction is given, most of the oxygen gas can be discharged from the oxygen electrode side by continuing the supply of water for about one minute.

On the other hand, when the water electrolysis system 10 includes the hydrogen electrode side circulation pump 72, the hydrogen electrode side circulation pump 72 is preferably stopped at the same time as the electrolysis is stopped. This is because if hydrogen gas remains on the hydrogen electrode side at the time of abnormality diagnosis, the potential of the hydrogen electrode is maintained at 0 V, which facilitates control of the applied voltage within an appropriate range.

[3.2. Step b to step d]
Next, when it is detected that the i-th PEM type water electrolysis stack _20i is stopped, the _auxiliary power _supply 60 is used to apply the k-th voltage V _i,j,k (1≤k≤p, p≥1) at which neither electrolysis reaction nor fuel cell reaction occurs in the same direction as during electrolysis (step b). Next, the current detection device 64 is used to detect the k-th current I i,j,k of the j-th single cell 22 _j corresponding to V _{i ,j,k} (step c). Furthermore, the resistance R i _,j, k of the j-th unit cell 22 _j is calculated from the k-th voltage V i _,j,k and the k-th current I i _,j,k (step d).

[3.2.1. Magnitude of Applied Voltage]
The k-th voltage V _i,j,k applied to the j-th single cell 22 _j must be a voltage at which neither the electrolytic reaction (ie, the oxygen generation reaction) nor the fuel cell reaction (ie, the oxygen reduction reaction) occurs. There is This is for minimizing the current that flows due to causes other than micro-shorts. The magnitude of the k-th voltage V _i,j,k is not particularly limited as long as it is a voltage at which neither electrolytic reaction nor fuel cell reaction occurs.

The "voltage at which neither the electrolytic reaction nor the fuel cell reaction occurs" depends on the amount of oxygen gas and the amount of hydrogen gas remaining in the j-th unit cell _22j . Also, the amount of gas remaining in the j-th single cell 22 _j can be indirectly known by detecting the cell voltage CV _i,j of the j-th single cell 22 _j . Therefore, it is preferable to select the optimum magnitude and application timing of the applied voltage according to CV _i,j . A method of determining the magnitude of the applied voltage and the voltage application timing using CV _i,j will be described below.

[A. When CV _i,j >1.3V]
Immediately after the i-th stack 20 _i is stopped, relatively large amounts of oxygen gas and hydrogen gas remain in the oxygen electrode and hydrogen electrode, respectively. In this case, the cell voltage CV _i,j of the j-th single cell 22 _j normally exceeds 1.3V. When CV _i,j exceeds 1.3 V, when a voltage is applied to the j-th single cell 22 _j using the auxiliary power supply 60, an electrolytic reaction may progress in the j-th single cell 22 _j . . In such a case, it is preferable to wait until CV _i,j becomes 1.3 V or less.

During this time, it is preferable to continue to supply water to the oxygen electrode using the oxygen electrode side circulation pump 42 and to discharge the oxygen gas remaining in the oxygen electrode.
On the other hand, in a system equipped with the hydrogen electrode side circulation pump 72, in order to maintain the potential of the hydrogen electrode side at 0 _V when the voltage for abnormality diagnosis is applied, the hydrogen electrode side circulation pump must be 72 is also stopped, and hydrogen gas is preferably left in the hydrogen electrode.

[B. 1.0 V ≤ CV _i,j ≤ 1.3 V]
After stopping the i-th stack _20i , when the supply of water to the oxygen electrode (discharge of oxygen gas from the oxygen electrode) is continued for a predetermined time, high-concentration hydrogen gas remains on the hydrogen electrode side. In addition, a medium to low-concentration oxygen gas remains on the oxygen electrode side. In this case, the cell voltage CV _i,j of the j-th single cell 22 _j is in the range of 1.0 to 1.3V. When CV _i,j is in this range, no water electrolysis reaction occurs. Further, even if the fuel cell reaction occurs, the amount of reaction is very small.

Therefore, when CV _i,j is in the range of 1.0 to 1.3 V,
(a) when the supply of water to the oxygen electrode of the i-th stack _20i is continued, stop the supply of water to the oxygen electrode;
(b) Using the auxiliary power supply 60, apply the k-th voltage V _i,j,k of 1.0 to 1.3 V to the j-th single cell 22 _j , measure the current I _i,j,k and measure the resistance value R A calculation of _i,j,k is preferably performed.

Current is measured even when there is no micro-short, but the value is usually not stable. This is because charging and discharging of the so-called capacitor component of the electric double layer occur.
On the other hand, if there is a micro-short, the current will flow stably in a few seconds after starting the measurement. After a sufficient period of time (within several seconds depending on the auxiliary power supply 60) for the completion of the charging and discharging of the capacitor component, the current _Ii,j,k flowing through the j-th unit cell _22j is reduced to the current due to the capacitor component. value is relatively large. The resistance R _{i,j,k can be obtained by dividing the k-th voltage V i, j,k} by the current I _i,j,k .

When a micro-short occurs, the calculated resistance R _i,j,k matches in order with the resistance of the conductive fiber that causes the micro-short. For example, if the conductive fibers used for the diffusion layers 28b and 30b have a resistance of 50 mΩ, the resistance R _i,j,k when a micro-short occurs is about 50 to 500 mΩ. It is considered that the reason why R _i,j,k has a width is that the conductive fibers do not necessarily pierce the electrolyte membrane 26 perpendicularly.

[C. 0.6V<CV _i,j <1.0V]
After the i-th stack 20 _i is stopped, the supply of water to the oxygen electrode side is also stopped when a certain period of time has passed. When the supply of water to the oxygen electrode side is stopped and a certain period of time elapses, oxygen and hydrogen are consumed by crossover, and hydrogen and oxygen remaining as bubbles are discharged outside the system, and the gas pressure inside the cell increases. descend. At a stage where the cell voltage is about 1.0 to 0.6 V, the potential on the hydrogen electrode side is still around 0 V, and the situation on the hydrogen electrode side has little effect on the cell voltage CV _i,j . is a factor that determines CV _i,j . Therefore, the CV _i,j of the j-th single cell 22 _j drops below 1.0 V as the oxygen in the electrode decreases.

However, when CV _i,j is about 1.0 to 0.6 V, oxygen still remains in the oxygen electrode. When a voltage for abnormality diagnosis is applied to the j-th unit cell 22 _j in this state, a current flows through the circuit used for the application, so that a fuel cell reaction of the cell may occur. Therefore, information other than the micro-short information is detected.
At least, when CV _i,j is 0.6 V or less, the oxygen on the electrode surface is quickly consumed when the voltage is applied. In addition, since it takes time for the oxygen to compensate for the consumed amount to reach the electrode surface, the fuel cell reaction hardly occurs. Therefore, in such a case, it is preferable to wait until CV _i,j becomes 0.6 V or less.

[D. When CV _i,j ≤ 0.6 V]
If CV _i,j is 0.6 V or less, a considerable amount of time has passed since the i-th stack 20 _i was stopped, oxygen gas has been discharged considerably from the oxygen electrode side, and there is little residual gas. considered as a state. However, hydrogen gas may remain on the hydrogen electrode side.

If the k-th voltage V _i,j,k is applied in a state in which hydrogen remains at a relatively high concentration, a negative voltage is applied to the original hydrogen electrode (a DC power supply to the original hydrogen electrode ), hydrogen evolution occurs at the oxygen electrode. Conversely, when hydrogen gas is contained on the oxygen electrode side, when a positive voltage is applied to the original hydrogen electrode (connecting the negative electrode of the DC power supply to the original hydrogen electrode), the hydrogen on the oxygen electrode side is become protons, which are transported to the original hydrogen electrode and converted to hydrogen gas on the catalyst surface. This is the electrochemical transport of hydrogen (the so-called hydrogen pump). In this case, the information of the micro-short is buried, which is not preferable.

For example, water on the oxygen electrode side usually contains oxygen gas. In that case, the potential of the oxygen electrode is about 0.8V. On the other hand, when a small amount of hydrogen gas remains on the hydrogen electrode side, the potential of the hydrogen electrode is about 0.2V, so CV _i,j is about 0.6V. When no hydrogen gas remains on the hydrogen electrode side, the potential of the hydrogen electrode is about 0.4V, so CV _i,j is about 0.4V.

When the hydrogen electrode potential is 0.2 V or 0.4 V and the k-th voltage V _i,j,k of 1.0 to 1.3 V is applied to the j-th single cell 22 _j , the hydrogen electrode potential is high and the applied As the voltage is higher, the potential of the oxygen electrode momentarily exceeds the equilibrium potential of oxygen of 1.2 V, and an oxidation current begins to flow slightly. The corresponding current begins to flow as a reduction current at the counter electrode, and hydrogen begins to adhere to the electrode surface. As a result, the hydrogen electrode potential becomes close to 0V. Thus, an electrolytic reaction may occur in the j-th unit cell 20 _j .

If CV _i,j is 0.6V or less, the hydrogen electrode potential may be 0.2V or 0.4V. However, at this time, even if the k-th voltage V _i,j,k of 0.1 to 0.3 V is applied to the j-th single cell 22 _j using the auxiliary power supply 60, the oxygen electrode potential is at most 0.7 V. This is not a condition for an oxidation current to flow. Therefore, the counter electrode never becomes 0V. Thus, under these conditions, no electrode reaction occurs and, therefore, no current generation occurs. Therefore, when CV _i,j is 0.6 V or less, the auxiliary power supply 60 is used to apply the k-th voltage V _i,j,k of 0.1 to 0.3 V to the j-th single cell 22 _j. , the current I _i,j,k and the resistance R _i,j,k calculation.

When CV _i,j is 0.6 V or less and no hydrogen gas remains on the hydrogen electrode side, no current due to electrochemical transport of hydrogen flows.
On the other hand, when hydrogen gas remains on the hydrogen electrode side, current due to electrochemical transport of hydrogen may flow. In such a case, when the hydrogen electrode side circulation pump 72 is provided, the hydrogen electrode side circulation pump 72 is restarted before and after CV _i,j becomes 0.6 V or less to discharge hydrogen gas from the hydrogen electrode side. preferably.

[3.3. step e]
The level (p) of the k-th voltage V _i,j,k (1≦k≦p) applied to the j-th unit cell 22 _j during abnormality diagnosis may be one, or two or more. . Further, even when the number p of preset levels is two or more, one of them may be used for abnormality diagnosis.
On the other hand, when p≧2, when calculating a plurality of R _i,j,k , steps (b) to (d) are repeated (p−1) times (step e). As described above, when diagnosing an abnormality, a current may flow due to a factor other than a micro-short. In such a case, a plurality of levels of voltage are set in advance, the resistance R _i,j,k is measured under different conditions for one j-th unit cell 22 _j , and a plurality of R _i,j,k are used to It is preferable to judge comprehensively.

In FIG. 4, different voltages (first voltage V _i,j,1 to third voltage V _i,j,3 ) are applied to the normal j-th single cell and the j-th single cell in which a micro-short occurs. An example of measurement results of currents (first current I _i,j,1 to third current I _i,j,3 ) when applied is shown. As shown in FIG. 4, even if different voltages are applied to the normal j-th single cell 20 _j , the current hardly changes.
On the other hand, when a different voltage is applied to the j-th single cell 20 _j in which micro-shorting has occurred, the current increases in proportion to the voltage.

FIG. 5 shows an example of the measurement results of the resistance R when different voltages V are applied to the j-th single cell in which a micro-short occurs. If a micro-short occurs, current is approximately proportional to voltage. Therefore, when the resistance (first resistance R _i,j,1 to third resistance R _i,j,3 ) is calculated for each voltage, ideally each calculated resistance R _i,j,k is approximately match.
In practice, the plurality of resistors R _i,j,k may not always match. In such a case, it is preferable to consider the magnitudes of a plurality of resistors _Ri,j,k and make a comprehensive judgment.

[3.4. process f]
Next, it is determined whether or not at least one of R _i,j,k or a combination thereof is equal to or less than threshold value R _c (step f).
When a micro-short occurs in the j-th single cell 22 _j , the resistance R _{i,j,k of} the j-th single cell 22 j becomes smaller than when there is no micro-short. Therefore, a threshold value _Rc is set in advance, and if at least one of Ri _,j,k or a combination thereof is equal to or less than the threshold value _Rc , it can be determined that a micro-short has occurred.

Here, "determine whether at least one of Ri _,j,k or a combination thereof is equal to or less than the threshold value _Rc "
(a) Directly comparing the calculated one or more R _i,j,k with the threshold value R _c , and when the one or more R _i,j,k is less than or equal to R _c , a micro-short occurs. or
(b) comparing a variable calculated based on two or more R _i,j,k (for example, the average value of R _i,j,k ) with R _c , and when the variable is less than or equal to R _c This means judging that a micro-short has occurred.
The value of the threshold value R _c is not particularly limited, and an optimum value can be selected according to the composition of the micro-short-causing substance and the purpose.

[4. Water electrolysis device abnormality diagnosis program]
6 and 7 show flow charts of the water electrolysis apparatus abnormality diagnosis program according to the present invention. A program for diagnosing abnormality of a water electrolysis device according to the present invention comprises a program for causing a computer to execute the following procedures.

First, in step 1 (hereinafter also simply referred to as "S1"), an initial value of 1 is substituted for the variable i for identifying the PEM type water electrolysis stack.
Next, in S2, in a water electrolysis system provided with n (n≧1) PEM type water electrolysis stacks consisting of m (m≧2) single cell laminates, the i PEM type water electrolysis stack (1 ≤i≤n) is stopped (procedure A). When the i-th stack (here, the first stack) is in motion (S2: NO), it is difficult to detect a micro-short. In this case, go to S3. In S3, 1 is added to the variable i.

Next, in S4, it is determined whether or not the variable i exceeds the total number of stacks (n). If i>n is not true (S4: NO), it means that there remains a stack that has not been diagnosed. In this case, the process returns to S2. Then, the above steps S2 to S4 are repeated until i>n.
On the other hand, if i>n (S4: YES), it means that there is no stuck stack at that point. In this case, go to S5. In S5, it is determined whether or not to continue the control. If the control is to be continued (S5: YES), the process returns to S1, and the steps S1 to S5 are repeated until the control is terminated.

On the other hand, if the i-th stack is stopped in S2 (S2: YES), the process proceeds to S11. In S11, an initial value of 1 is substituted for a variable j for identifying a single cell included in the i-th stack. Next, in S12, an initial value of 1 is substituted for the variable k for identifying the level of the voltage applied to the j-th unit cell.
Next, in 13, an auxiliary power supply is applied to the j-th unit cell (1≤j≤m) included in the i-PEM type water electrolysis stack, and the k-th voltage at which neither the electrolysis reaction nor the fuel cell reaction occurs is applied. V _i,j,k (1≤k≤p, p≥1) is applied in the same direction as during electrolysis, and V _i,j,k is stored in the memory (procedure B). The details of the procedure for applying V _i,j,k will be described later.

Next, in S14, the current detector is used to detect the k-th current Ii _{,j, k of the j-th single cell corresponding to Vi,j,k,} and _Ii,j,k is stored in the memory. (procedure C). Further, in S15, the resistance R _i,j,k of the j-th unit cell is calculated from the k-th voltage V _i,j,k and the k-th current I _i,j,k, and R _i,j,k is stored in the memory. Store (procedure D). Next, the process proceeds to S16. In S16, 1 is added to the variable k.

Next, in S17, it is determined whether or not the variable k exceeds the total number (p) of applied voltage levels. If k>p is not true (S17: NO), it means that selectable applied voltages remain. In this case, the process returns to S13. Then, the above steps S13 to S17 are repeated until k>p (procedure E).
On the other hand, if k>p (S17), it means that there are no selectable applied voltages left. In this case, the process proceeds to S18. If the applied voltage is level 1, S12, 16 and S17 can be omitted.

Next, in S18, it is determined whether at least one of Ri _,j,k or a combination thereof is equal to or less than a threshold value _Rc (hereinafter simply referred to as "Is Ri _{,j,k ?} or not) is determined. If not R _i,j,k ≦R _c (S18: NO), there is a high possibility that the j-th single cell is not micro-short-circuited. In this case, the process proceeds to S19 to add 1 to the variable j.
Next, in S20, it is determined whether or not the variable j exceeds the total number of single cells (m). If j>m is not true (S20: NO), it means that selectable single cells remain. In this case, the process returns to S12, and the steps S12 to S20 described above are repeated until j>m. Furthermore, if j>m (S20: YES), it means that there are no selectable single cells left. In this case, the process returns to S3, and the steps S3 to S5 and S11 to S20 described above are repeated.

On the other hand, if R _i,j,k ≤R _c (S18: YES), there is a high possibility that a micro-short has occurred in the j-th single cell. In that case, the process proceeds to S21, and an abnormality of the i-th stack is notified (procedure F) . A notification method is not particularly limited. For example, as a notification method,
(a) A method of displaying the identification number i of the stack 20 in which an abnormality has occurred on the monitor of the control device,
(b) There is a method of notifying the operator using a warning sound, a warning lamp, or the like.
After that, the process returns to S3. Then, the above steps S1 to S5 and S11 to S30 are repeated until the control is terminated (S5: YES).

FIG. 8 shows a flowchart of the procedure for applying the k-th voltage V _i,j,k . The application of the k-th voltage V _i,j,k to the j-th single cell (1≦j≦m) (S13) at which neither the electrolysis reaction nor the fuel cell reaction occurs is specifically performed in the following procedure. is preferred.

That is, in S12 of FIG. 7, after substituting the initial value 1 for the variable k, the process proceeds to S131 of FIG. In S131, the voltage detection device is used to detect the cell voltage CV _i,j of the j-th unit cell of the i-PEM water electrolysis stack in the stopped state (procedure B1). Next, in S132, it is determined whether or not CV _i,j is 1.0 V or more and 1.3 V or less (procedure B2). When CV _i,j is 1.0 V or more and 1.3 V or less (S132: YES), the process proceeds to S133.
At S133, if the oxygen electrode side circulation pump is operating, it is stopped. Next, in S134, V _i,j,k of 1.1 V or more and 1.3 V or less is applied to the j-th single cell (procedure B3). Then, proceed to S14 in FIG. 7 to repeat the above-described procedure (that is, detection of I _i,j,k , calculation of R _i,j,k , and comparison of R _i,j,k and R _c ). .

If CV _i,j is not equal to or greater than 1.0 V and equal to or less than 1.3 V (S132: NO), the process proceeds to S135. In S135, it is determined whether or not CV _i,j is 0.6 V or less (procedure B4). If CV _i,j is not less than 0.6 V (S135: NO), the process returns to S132 because accurate diagnosis of abnormality cannot be performed. Then, steps S132 and S135 described above are repeated until CV _i,j becomes 0.6 V or less.
On the other hand, if CV _i,j is 0.6 V or less (S135: YES), proceed to S136 and apply V _i,j,k of 0.1 V or more and 0.3 V or less to the j-th single cell. (Procedure B5). Then, proceed to S14 in FIG. 7 to repeat the above-described procedure (that is, detection of I _i,j,k , calculation of R _i,j,k , and comparison of R _i,j,k and R _c ). .

[4. action]
The resistance per micro-short is several tens of mΩ to several hundred mΩ. However, in the case of a cell with a large area of several tens cm ² to several hundred cm ² , which is a practical size, the resistance of the electrolyte membrane is even smaller (several mΩ or less). Therefore, even if the voltage change of the single cell is measured during operation of the water electrolysis device, it is difficult to detect the micro-short because the voltage change due to the micro-short is significantly smaller than the applied voltage. In addition, depending on the electrolysis conditions, the reaction current of the electrolysis reaction and the fuel cell reaction and the charging/discharging current of the double layer component flow.

Furthermore, unlike the case where the potential or current is controlled using an external power supply, or the case where the electrode potential is controlled by coexisting an active gas that responds to the electrode (for example, oxygen or hydrogen), the gas environment around the electrode and the electricity If you try to measure the voltage without controlling the physical connection, the state of the power supply and the state of the residual gas cannot be defined, and as a result the potential of the electrode will not stabilize. Therefore, depending on the history before the measurement, there is a possibility that some kind of reaction may occur at the electrode and the information of the micro-short may be buried. In addition, depending on the state, there is also the possibility that information on micro-shorts can be seen. It is not certain whether micro-short information can be detected if the measurement is performed without specifying the conditions.

In addition, since gas cross-leakage, crossover, etc. are also reflected in the voltage change after stopping, the speed of change changes according to the gas pressure difference between the electrodes. In this way, since information other than micro-shorts is also reflected, stable measurement cannot be performed. Therefore, the method of detecting the voltage between electrodes (Patent Document 1) cannot stably detect the occurrence of a micro-short. Furthermore, in a method like this method that detects only voltage, the existence of resistance is only inferred from the rate of change, and it cannot be said to be a direct measurement. can't judge

On the other hand, when the PEM type water electrolysis stack is stopped, if a predetermined voltage V is applied to each single cell included in the PEM type water electrolysis stack and the current I flowing through the single cell is detected, the applied voltage V and the current I, the resistance value R between the electrodes of the single cell can be calculated. Accordingly, if the resistance value R is within the range of general values for micro-shorts, it can be determined that the detected phenomenon is highly likely to be micro-shorts.
In this way, when the measurement is performed in a configuration in which a current flows to the outside, the current V and the corresponding current I are obtained, and the resistance value R can be calculated. If this value does not appear to be stable, it can be determined that the measurement conditions may not be stable.

The voltage V alone is susceptible to current generation factors other than micro-shorts in the single cell. Insensitive. Therefore, by comparing the calculated resistance value R with the threshold value _Rc , it is possible to accurately determine whether or not a micro-short has occurred.

Although the embodiments of the present invention have been described in detail above, the present invention is by no means limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present invention.

The water electrolysis system according to the present invention can be used as a hydrogen source installed in a hydrogen station for supplying hydrogen to fuel cell vehicles.

10 water electrolysis system 20 PEM type water electrolysis stack 22 single cell 38 main power supply 60 auxiliary power supply

Claims (5)

A program for diagnosing water electrolysis equipment to cause a computer to perform the following procedures.
(A) In a water electrolysis system provided with n (n ≥ 1) PEM type water electrolysis stacks consisting of m (m ≥ 2) single cell laminates, the i-th PEM type water electrolysis stack (1 ≤ i ≤ n) is stopped.
(B) When the stop of the iPEM type water electrolysis stack is detected, electrolysis is performed using an auxiliary power supply for the j-th single cell (1≤j≤m) included in the iPEM type water electrolysis stack. The k-th voltage V _i,j,k (1 ≤ k ≤ p, p ≥ 1) at which neither reaction nor fuel cell reaction occurs is applied in the same direction as during electrolysis, and the V _i,j,k is stored in the memory. Procedure B for memorization.
(C) using a current detection device to detect the kth current Ii _,j,k of the jth single cell corresponding to the Vi _,j,k, and storing the Ii _,j,k in the memory; Procedure C for memorizing.
(D) Calculate the resistance R _i,j,k of the j-th unit cell from the k-th voltage V i _{,j,k and the k-th current I i ,j,k,} and calculate the R _i,j,k as Procedure D for storing in memory.
(E) In the case of p≧2, when calculating a plurality of R _i,j,k , a procedure E in which the procedures B to D are repeated (p−1) times.
(F) Step F of notifying that there is an abnormality in the i-PEM water electrolysis stack when at least one of Ri _,j,k or a combination thereof is equal to or less than the threshold value _Rc . The procedure B is
a step B1 of detecting the cell voltage CV _i,j of the j-th single cell of the i-th PEM water electrolysis stack in a stopped state using a voltage detection device;
A procedure B2 for determining whether the CV _i,j is 1.0 V or more and 1.3 V or less;
a step B3 of applying the V _{i,j ,k of 1.1 V to 1.3 V to the j-th unit cell when the CV i,j is} 1.0 V to 1.3 V;
The water electrolysis device abnormality diagnosis program according to claim 1, comprising: The procedure B is
a procedure B4 for determining whether the CV _i,j is 0.6 V or less;
When the CV _i,j is 0.6 V or less, a step B5 of applying the V _i,j,k of 0.1 V to 0.3 V to the j-th unit cell.
The water electrolysis device abnormality diagnosis program according to claim 2, further comprising: A water electrolysis system with the following configuration:
(1) The water electrolysis system is
n (n≧1) PEM type water electrolysis stacks with m (m≧2) single cells;
a main power source that individually supplies power to the i PEM type water electrolysis stack (1≤i≤n);
a water supply device for simultaneously or individually supplying water to the oxygen electrodes of the iPEM water electrolysis stack;
an auxiliary power supply that applies a voltage for abnormality diagnosis to the j-th unit cell (1≤j≤m) included in the i-th PEM water electrolysis stack when the i-th PEM water electrolysis stack is stopped;
a voltage detection device for detecting the voltage applied to the j-th single cell;
a current detection device that detects the current flowing through the j-th single cell;
and a control device for controlling the water electrolysis system.
(2) The control device stores the water electrolysis device abnormality diagnosis program according to any one of claims 1 to 3. 5. The water electrolysis system according to claim 4, further comprising a multistage switch for switching and supplying the applied voltage from the auxiliary power source to each of the j-th unit cells.

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