RU2543487C2 - Operating method for nickel-hydrogen batteries in power supply system of spacecraft - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention can be applied in operation of nickel-hydrogen accumulator batteries (AB) in autonomous power supply systems (PSS) of spacecrafts operating at low circumterrestrial orbit. Operation method for nickel-hydrogen accumulator batteries (AB) of spacecraft power supply system involves two or more batteries cycling in charge-discharge mode set by the onboard automation of power supply system, parameter monitoring for each battery, such as current electric capacity, voltage, temperature, regular (once in 6-9 months) prohibition of charging for one of the AB to perform forming cycle, with onboard equipment used as discharge load, AB voltage value selected as a criterion limiting discharge depth, so that border level of voltage is set in Volts, equal to the number n or (n+1) of accumulators in the battery, upon achievement of which an AB charging prohibition is released, and maximum AB voltage for charging, determined during completion of forming cycle, is used for assessment of battery state and battery degradation forecast; similar procedure is repeated for the next AB with the only difference that battery charging degree is limited either by unconditional logics of hardware or by conditional logics of software, where AB charging control by conditional logic is selected as the main variant, and unconditional logic is assigned as a backup variant, AB disconnection from charging by unconditional logic is performed when gas medium pressure in the AB exceeds i^th threshold value selected as operational value out of multiple discrete preset threshold pressure values, and transition to another operational threshold pressure value out of this multitude is performed by one-time command depending on AB temperature, and AB disconnection from charging by conditional logic is controlled discretely upon transition between temperature ranges and smoothly within each temperature range, using a linear equation system depending on temperature t and applicable in a particular relevant range of AB temperature change.

EFFECT: improved functioning reliability of nickel-hydrogen batteries by operation life extension and longer routine operation.

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Description

The present invention relates to the electrical industry and can be used in the operation of nickel-hydrogen storage batteries (AB) in autonomous power supply systems (BES) of spacecraft (SC), operating in low Earth orbit.

During the entire period of active existence of modern spacecraft in low Earth orbit, 10,000 or more charge-discharge AB cycles are performed, and a similar mode of operation of solar cells is best provided by nickel-hydrogen storage batteries (NAB).

A feature of NVAB is that all series-connected batteries are charged and discharged with the same amount of electric charge (Ah). In the ideal case, if the initial state of the batteries is the same, there should be no change in their relative degrees of charge. However, due to the difference in the self-discharge rate, the batteries connected in series acquire a different state of charge. Any deviation caused by the dispersion of the initial characteristics of the self-discharge, the temperature gradient inside the NVAB and the aging process can increase the spread in the degrees of charge of the batteries, which leads to the degradation of the characteristics of the NVAB, and moreover, in the absence of systems for balancing the state of charge, it can lead to a decrease in the reliability of the operation of the NVAB . There is also the so-called “memory effect” associated with a decrease in the capacity of NVAB with prolonged citation to a shallow depth of (10-20)%. The reason for the decrease in the capacity of NVAB is the crystallization of a certain part of the material of the electrodes of the batteries due to its alienation for a long time from the current-forming chemical reaction. It is precisely this citation depth that is chosen when operating the AB in low Earth orbits. Therefore, in order to equalize the batteries in terms of capacity, eliminate the so-called “memory effect” and evaluate the state of the battery, it is necessary to periodically conduct recovery (molding) cycles, which represent an almost complete discharge and charge of the battery.

On the resource, and, consequently, on the reliability of its functioning, the NWAB is significantly affected by its temperature regime. So, the operating mode at elevated temperatures leads to increased degradation of the main characteristics of the batteries, and at low temperatures, to an increase in the internal resistance of NVAB.

The temperature regime of NVAB depends both on the temperature of the coolant cooling the batteries and on its own heat. The greatest heat generation occurs when the NVAB is recharged, when the batteries are charged in the low-efficiency region with oxygen evolution (B.C. Bagotsky, A.M. Skundin. Chemical current sources. M: Energoizdat, 1981). Therefore, the selection of the optimal from the point of view of minimum own heat emission mode of operation of the NVAB as part of the spacecraft power system is an urgent task.

A known method of operating the battery according to patent RU No. 2289178 (analogue) is that charge-discharge cycles are carried out, the voltage of each battery and the battery as a whole are monitored, the current discharge and charging capacities are determined, as well as the charge current; the battery charge is carried out by direct current to a value (0.6-0.8) of the nominal capacity. Before the start of the shadow sections of the geostationary orbit, a recovery discharge-charge cycle of the batteries is performed, while the batteries are discharged to discharge resistance for 40-50 hours, and the charge is stopped after the battery voltage drops to a predetermined value, then the batteries are charged by connecting it to the standard BOT circuit.

The disadvantage of this method is also the low reliability of the operation of the EPA, in particular, and the insufficient survivability of the spacecraft as a whole. This is due to the fact that the process of conducting a recovery discharge charge (molding cycle) takes a long time, and at this time the battery is taken out of normal operation. For geostationary orbits, this is acceptable because shadow orbits take 90 days a year, the rest of the spacecraft’s time is in the illuminated portion of the orbit, the power is supplied from solar panels and the decommissioning of one battery for a long time practically does not affect the survivability and reliability of the spacecraft. For low-orbit spacecraft, the decommissioning of one of the batteries for a long time can significantly reduce the survivability and reliability of operation of the AB, in particular, and the spacecraft as a whole, because shadow portions of the orbit occur every hour and a half.

A known method of operating a nickel-hydrogen storage battery of the spacecraft’s power supply system according to patent RU No. 2399122 (prototype), which consists in the fact that two or more batteries are cycled in a charge-discharge mode defined by the on-board automation of the power supply system, the degree of charge of the batteries is limited by the level of response of the pressure signal sensors located in the individual batteries of each battery, control the parameters of each battery, for example current electric capacity, voltage, temperature, periodically carry out AB molding cycles by deep discharge, evaluate the state of the AB, periodically, for example, once every 6-9 months, charge prohibition for one of the ABs is introduced, space-borne onboard equipment is used as a discharge load apparatus, the criterion for limiting the depth of the discharge is selected the value of the voltage AB, and the value of the boundary voltage level is set in volts equal to the number n or (n + 1) of batteries in the battery, when reaching They remove the ban on the battery charge, thereby including it in regular operation, the values of the charging capacity of the alarm pressure sensor and the maximum battery voltage when charging, determined during the completion of the molding cycle, used to assess the state of the battery and predict its degradation, repeat the same sequence of operations for the subsequent AB, while the period from the completion of the molding cycle of one AB to the start of the molding cycle of another AB is selected based on the temperature th mode molded AB.

The disadvantage of the prototype is the relatively low reliability of the power supply system associated with a decrease in battery life during its long-term operation at elevated temperatures. Indeed, conducting periodically molding cycles significantly increases the battery life and, as a rule, the reliability of its operation as part of the SEP spacecraft. However, in the case of improper normal operation, when the battery is disconnected from the charge when the specified charge level is reached, which is in the low efficiency range, it can overheat, leading to a significant limitation of the resource and, as a result, to a decrease in the reliability of operation.

The objective of the invention is to increase the reliability of the functioning of the NWAB by increasing its resource, i.e. duration of normal operation.

This object is achieved by the fact that in the method of operating the nickel-hydrogen storage batteries (AB) of the spacecraft’s power supply system, which consists in the fact that two or more batteries are cycled in a charge-discharge mode specified by the on-board automation of the power supply system, the parameters of each battery are controlled , for example, the current electric capacity, voltage, temperature, periodically once every 6-9 months, a charge ban is introduced for one of the batteries to perform the molding cycle, in As a discharge load, the onboard equipment of the spacecraft is used, the voltage value of the battery is selected as a criterion for limiting the depth of the discharge, and the value of the boundary voltage level is set in volts equal to the number n or (n + 1) of batteries in the battery, upon reaching which the battery charge ban is removed, and in the process of completing the molding cycle, the value of the maximum battery voltage during charging is used to assess the state of the battery and predict its degradation, similar to the sequence of operations is repeated for the subsequent battery, in which the degree of charge of the batteries is limited either hardware by “hard” logic or software by “flexible” logic, and battery charge control by “flexible” logic is chosen as the main option, and by “hard” "Logic - as a backup option, while disconnecting the battery from the charge according to" hard "logic is performed on the basis of excess pressure of the gaseous medium in the battery of the i-th threshold value, selected as a working one from the set of discrete ones, in advance for data of pressure threshold values, and transferring to another working pressure threshold value from this set is carried out according to a one-time command, based on the temperature of the battery, and disconnecting the battery from the charge according to the "flexible" logic is controlled discretely when moving from one temperature range to another and smoothly inside of each range, using a system of linear equations depending on its temperature t, which are valid, respectively, in a specific range of changes in temperature AB:

R _por. = α ₁ (P ₀ - k · t) in the range t ₁ ≤t≤t ₂ ;

R _por. = α ₂ (P ₀ - k · t) in the range of t ₂ ≤t≤t ₃ ;

………………………………………………

R _por. = α _n - (P ₀ - k · t) in the range t _n <t≤t _{n + 1} ;

t _then ≥ · t _crit in the range t≥t _crit. ,

where R _{pore. is the} threshold value of the pressure of the gas medium in the battery, at which the battery is disconnected from the charge, in MPa;

P ₀ - value (nameplate value) of the pressure of the gas medium in the battery at a temperature of 0 ° C;

k is a constant coefficient, in MPa / city;

t is the temperature of the battery, in ° C;

α _i is a constant dimensionless coefficient that varies discretely, for example, from 1 to 0.6;

t _crit - temperature critical for functioning, at which the battery is disconnected from the charge regardless of the pressure of the gas medium in the battery;

α ₁ > α ₂ >·> α _n ;

t _i <t ₂ <· <t _n <t _crit.

The drawing shows a simplified block diagram of the operation of the EPA.

The power supply system consists of AB batteries (AB1, AB2, AB3) 1, a photovoltaic (BF) 2 battery, a complex of automation and voltage regulation (CAS), which includes RU (RU1, RU2, RU3) 3 discharge devices, charger chargers (ЗУ1, ЗУ2, ЗУ3) 4, voltage stabilizer and automatics (СНА) 5. On-board equipment (БА) 6 can be powered from the RU (РУ1, РУ2, РУ3) 3 or СНА 5, as well as during testing from a ground power source E _naz through the remote switch 7. AB batteries (AB1, AB2, AB3) 1 before starting the spacecraft charge Xia auxiliary charger _{charge E.}

In certain operating modes of the power supply system RU (RU1, RU2, RU3) 3 and СНА 5 can supply electrical energy together with the load, which is BA 6. During abnormal operation of RU (РУ1, РУ2, РУ3) 3 or charger (ЗУ1, ЗУ2, ЗУ3 ) 4 to change the configuration of the SES, an emergency bus with switching equipment 8 can be used, for example, if 3RU1 fails, the battery AB1 is connected in parallel with AB2 to 3RU2, etc.

If necessary, one-time commands (RC) can be issued from the on-board control complex (BCU) 9 to change the operation modes of the electronic control system, including such control devices as “Prohibition of charge ABi”, “Recovery of CAS”, “Shutdown of ABi”, “Shutdown of 3PYi emergency bus. " During the normal operation of the solar cells, the batteries (AB1, AB2, AB3) 1 are charged in the light portion of the orbit of the spacecraft, and in the shadow portion of the batteries (AB1, AB2, AB3) 1 they feed the BA 6 with stabilized RU (RU1, RU2, RU3) 3 voltage. Photovoltaic battery 2 in the light section provides stabilized SNA 5 with voltage of BA 6 and at the same time charges AB (AB1, AB2, AB3) 1.

From FIG. it can be seen that the “negative” AB buses are not switched and are galvanically connected to each other, therefore, the emergency bus switching equipment 8 provides for the change of the SES configuration only on the “positive” bus.

Since a significant variation in the parameters of AB batteries (AB1, AB2, AB3) 1 occurs after 6–9 months, the frequency of molding cycles is selected once every 6–9 months. At the same time, a specific period of their holding within 6–9 months can be established based on other requirements, for example, during the period of the minimum duration of the shadow sections of the spacecraft’s orbit, etc. Molding cycles are carried out in turn on one of the ABs (AB1, AB2, AB3) 1 in an arbitrary order, using a charge-discharge device (3RU) 10, consisting of RU (RU1, RU2, RU3) 3 and ZU (ZU1, ZU2, ZU3 ) 4, and the emergency bus with switching equipment 8, if necessary. A day before the molding cycle, during normal operation of the power supply system, information is collected (in the spacecraft telemetry monitoring system is not shown) about the operation of the formable battery (maximum charge voltage, minimum discharge voltage, maximum current capacity, maximum temperature).

Prohibition of charge by AB formable is introduced by issuing from the ground control complex (GCC) through BKU 8 of the Republic of Kazakhstan "Prohibition of AB charge". In this case, there is a discharge of the formable AB to the load (on-board equipment 6) in the shadow areas of the orbit. Thus, the energy stored in the battery is used for its intended purpose. After the necessary deep discharge has been performed, the AB charge ban is lifted by issuing the “CAS Recovery” RK and the molded AB is charged against the background of the regular operation of the solar cells in the solar orbit. The molding cycle is considered completed if the formed AB will be replenished to a predetermined value of the current capacity.

In the proposed method of operation of the NVAB, the battery disconnection from the charge is controlled using either “flexible” logic (the main option) or “hard” logic (the backup option) without using pressure signal sensors. The battery is disconnected from the charge according to both “flexible” logic and “hard” logic according to the calculated or specified threshold value of the pressure of the gaseous medium in the NVAB (hereinafter referred to as the threshold pressure value), respectively, which is hydrogen, which is the active substance of the batteries . Depending on the degree of charge, the pressure of the gaseous medium in the NVAB practically proportionally changes, moreover, when charging, the pressure increases, and when discharging, it decreases. (B.C. Bagotsky, A.M. Skundin. Chemical sources of current. M: Energoizdat, 1981).

The "flexible" logic for controlling the battery disconnection from the charge, based on the automatic selection of the threshold pressure value depending on the temperature, is based on the following principles:

the choice of an array of ranges of changes in temperature AB;

selection of a threshold pressure value at a temperature of t = 0 ° C;

selection of an array of constant coefficients for a discrete programmed reduction of the threshold pressure value, in the case of an increase in the temperature of the battery and when it goes beyond the specified i-th range;

the choice of an analytical linear dependence of the threshold pressure on temperature within each i-th range;

selection of the critical temperature at which the battery is disconnected from the charge, regardless of its current capacity.

These conditions are fully satisfied by the system of linear equations of the form:

$$\begin{array}{l}{R}_{P\mathrm{about}R.}={\alpha }_{\mathrm{one}}\cdot (R_0-k\cdot t)\mathrm{at}d\mathrm{and}\mathrm{but}P\mathrm{but}s\mathrm{about}ne{t}_{\mathrm{one}}\le t\le {\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="00000002.png"\; state="\{\{state\}\}">t</figure-callout>}}_2;\\ R_{P\mathrm{about}R.}={\mathrm{<figure-callout\; id="2"\; label="\alpha "\; filenames="00000002.png"\; state="\{\{state\}\}">\alpha </figure-callout>}}_2\cdot (R_0-k\cdot t)\mathrm{at}d\mathrm{and}\mathrm{but}P\mathrm{but}s\mathrm{about}ne{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="00000002.png"\; state="\{\{state\}\}">t</figure-callout>}}_2<t\le {\mathrm{<figure-callout\; id="3"\; label="t"\; filenames="00000002.png"\; state="\{\{state\}\}">t</figure-callout>}}_3;\\ ...............................................................(\mathrm{one})\\ R_{P\mathrm{about}R.}={\alpha }_n\cdot (P_0-k\cdot t)\mathrm{at}d\mathrm{and}\mathrm{but}P\mathrm{but}s\mathrm{about}ne{t}_n<t\le t_n{}_{+\mathrm{one}};\\ t_{P\mathrm{about}R.}\ge t_{\mathrm{to}R\mathrm{and}t.}\mathrm{at}d\mathrm{and}\mathrm{but}P\mathrm{but}s\mathrm{about}net\ge t_{\mathrm{to}R\mathrm{and}t.},\end{array}$$

where P _then. - the threshold value of the pressure of the gas medium in the battery, at which the battery is disconnected from the charge, in MPa;

P ₀ - value (nameplate value) of the pressure of the gas medium in the battery at a temperature of 0 ° C;

k is a constant coefficient, in MPa / city;

t is the temperature of the battery, in ° C;

α _i is a constant dimensionless coefficient that varies discretely, for example, in the range from 1 to 0.6;

t _crit - the temperature critical for functioning of the battery, at which the battery is disconnected from the charge, regardless of the pressure of the gas medium in the battery;

α ₁ > α ₂ >·> α _n ;

t _i <t ₂ <· <t _n <t _crit.

From the system of equations (1) it can be seen that for each temperature range AB the corresponding constant coefficient α _{i is set} , for a discrete change in the dependence of P _then. on temperature t. In the range from t _i to t _{i + 1, the} dependence of P _then. temperature t is linear. The value of q varies from about 1 to 0.6, i.e. the decrease in the maximum possible capacity during its replenishment of the battery can reach up to 50%, however, this mode can occur only in case of abnormal operation of the temperature control system and is not regular.

The "rigid" logic for controlling the battery disconnection from the charge provides for the presence of several predetermined threshold pressure values. When the threshold value of the pressure selected as the working one is reached, a battery charge ban is introduced. If it is necessary to switch to another working threshold pressure value from the NKU, the corresponding RK is issued (not shown in the NKU). The choice of one or another threshold pressure value, as a rule, depends on the temperature regime of the battery, and the higher the temperature, the lower the threshold pressure value.

In the power supply system of the spacecraft, they provide protection against high temperature, which is critical for the functioning of the battery. A sharp increase in temperature usually occurs when the battery is charged, when oxygen is released, therefore, the most effective measure to protect the battery from overheating is to disconnect from the charge for a time sufficient to reduce its temperature to a safe value.

Increasing the resource, therefore, and the reliability of the battery’s functioning is achieved by using “flexible” logic as the main option and “hard” logic as the backup option.

The really used system of equations (1) allows you to “flexibly” disconnect the battery from the charge: in this case, when the temperature rises by a certain amount, the threshold pressure decreases proportionally and the battery charge ends in the high efficiency region and the battery heat loss decreases, and then, as a result, decrease in its temperature. A discrete change in the threshold pressure value when moving from one temperature range to another significantly reduces the likelihood of the battery disconnecting from the charge in the region of low efficiency with high heat generation.

In case of failure of the “flexible” logic, the battery is disconnected from the charge by the “hard” logic. The “hard” logic is practically inferior in effectiveness to the “flexible” logic, and in some cases, when the temperature of the battery goes beyond the normal operating conditions, it expands the ability to control the operating mode of the battery. The disadvantages of controlling the disconnection of the battery from the battery according to the “hard” logic include the need for a large number of RCs and interference in the operation of the solar cells from the low-voltage switchgear.

Thus, the application of the proposed method for the operation of nickel-hydrogen storage batteries of the spacecraft’s power system will increase the resource and, as a result, the reliability of the battery

Claims (1)

A method of operating nickel-hydrogen storage batteries (AB) of the spacecraft’s power supply system, namely, that two or more batteries are cycled in a charge-discharge mode specified by the on-board automation of the power supply system, control the parameters of each battery, for example, current electric capacity, voltage , temperature, periodically once every 6-9 months a charge ban is introduced for one of the batteries to perform the molding cycle, the discharge board is used the spacecraft’s equipment, the AB voltage criterion is chosen as the criterion for limiting the depth of the discharge, and the value of the boundary voltage level is set in volts equal to the number n or (n + 1) of batteries in the battery, upon reaching which the ban on the charge of the battery is removed, and determined during molding of the cycle, the value of the maximum voltage of the battery when charging is used to assess the state of the battery and predict its degradation, a similar sequence of operations is repeated d I subsequent battery, characterized in that the degree of charge of the batteries is limited either hardware by “hard” logic, or software by “flexible” logic, and battery charge control by “flexible” logic is chosen as the main option, and by “hard” logic - as a backup option, in this case, the battery is disconnected from the charge according to “hard” logic by the sign of excess of the gas pressure in the battery of the i-th threshold value selected as a working one from a set of discrete, predetermined threshold values ny, and the transfer to another working threshold pressure value from this set is carried out according to a one-time command, based on the temperature of the battery, and the battery is disconnected from the charge according to the "flexible" logic discretely when switching from one temperature range to another and smoothly inside each range, using a system of linear equations depending on its temperature t, which are valid respectively in a specific range of changes in temperature AB:
R _por. = α ₁ · (P ₀ - k · t) in the range t ₁ ≤t≤t ₂ ;
R _por. = α ₂ · (P ₀ - k · t) in the range of t ₂ ≤t≤t ₃ ;
R _por. = α _n · (P ₀ - k · t) in the range t _n <t≤t _{n + 1} ;
t _then ≥ · t _crit in the range t≥t _crit. ,
where R _then is the threshold value of the pressure of the gas medium in the battery, at which the battery is disconnected from the charge, in MPa;
P ₀ - value (nameplate value) of the pressure of the gas medium in the battery at a temperature of 0 ° C;
k is a constant coefficient, in MPa / city;
t is the temperature of the battery, in ° C;
α _i is a constant dimensionless coefficient that varies discretely, for example, from 1 to 0.6;
t _crit - temperature critical for functioning, at which the battery is disconnected from the charge regardless of the pressure of the gas medium in the battery;
α ₁ > α ₂ >·> α _n ;
t _i <t ₂ <· <t _n <t _crit.

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