RU2305349C2 - Operating process of nickel-hydrogen storage battery incorporated in geostationary artificial earth satellite - Google Patents

Abstract

FIELD: electrical engineering; off-line power systems for geostationary satellites.

SUBSTANCE: proposed nickel-hydrogen storage battery operating process involves checkup of steady-state self-discharge current and degree of battery charge against analog pressure transducers, battery storage in charged state with periodic additional charges to compensate for battery self-discharge in solar orbits, and conduction of charge-discharge cycles in shadow orbits; steady-state self-discharge current is maintained in battery between 0.003 and 0.006 of its rated capacity; additional charge is ceased according to arithmetic mean of analog pressure transducer readings whose value affords desired steady-state self-discharge current during additional charge ranging between 0.01 and 0.012 of battery rated capacity under charge-discharge cycle conditions. In addition battery location temperature is checked, and battery self-discharge steady-state current is maintained between 0.003 and 0.006 of rated capacity at battery location temperature below 10-12 °C both in additional-charge mode and during charge-discharge cycles; additional impulse charge is conducted, its parameters (period and relative pulse duration) being chosen to provide for mean charge current higher in magnitude by two or three times than battery steady-state self-discharge current.

EFFECT: enhanced use factor and operating reliability of battery.

1 cl, 2 dwg

Description

The present invention relates to the electrical industry and can be used in the operation of nickel-hydrogen storage batteries mainly in stand-alone power supply systems for geostationary artificial Earth satellites (AES).

When using nickel-hydrogen storage batteries as part of a geostationary satellite, the main work falls on the period of shadow orbits (2 times a year for 45 days, the maximum duration of the “shadow” is 70 minutes). The rest of the time, the battery mainly works in storage mode with periodic charges, to compensate for self-discharge in solar orbits.

A distinctive feature of the operation of such batteries is the combination of intense charge-discharge cycles for 45 days (the period of shadow orbits), followed by a long, 4.5 months, storage in a charged state in solar orbits.

The operating experience of geostationary satellites showed that when using known methods of operating batteries, negative moments such as the temperature gradient of the batteries, “thermal acceleration” and the imbalance of the batteries in capacity can occur, which significantly limit the energy capabilities and resource of nickel-hydrogen batteries, which reduces the effectiveness of the use of the latter.

A known method of operating a nickel-hydrogen storage battery (patent No. 2084055, H01M 10/44) according to which the charge of the battery is limited based on the density of hydrogen, calculated on the basis of the measured pressure and temperature of the batteries, which provides battery charge to a level of (60-80) % of rated capacity.

A known method of operating a Nickel-hydrogen battery (ed. St. No. 1746443, H01M 10/44, 12/06), in which the control of charge-discharge cycles is carried out by a two-set pressure sensor with a difference in pressure settings ΔP and temperature, and the discharge ends minimum voltage, when the battery reaches the minimum voltage value, periodically increase the settings of the pressure sensor, and the lower setting is increased to the upper level, and the upper - by ΔР.

In the practical application of the known methods of operating nickel-hydrogen storage batteries, the following features of the behavior of the batteries were revealed.

So, on one of the existing geostationary satellites, to control the charge of a nickel-hydrogen storage battery with a nominal capacity of 70 Ah, two batteries with two-set pressure sensors were used, the upper set point of which was set in the interval (60-80)% of the nominal capacity, and the lower one by 4 Ah less. To compensate for the resource changes of the AB battery, the battery contains two more batteries with two-set pressure sensors, the upper set point of which is increased by ΔР≈4 Ah, and the lower one is raised to the level of the previous upper one. To control the hydrogen pressure level, all four accumulators were equipped with analog pressure sensors (ADD).

During operation of the battery, a gradual decrease in hydrogen pressure was observed in individual batteries. Considering that the hydrogen pressure is proportional to the degree of charge of the nickel-hydrogen battery, we note that a gradually increasing imbalance of the batteries appeared in the battery. A more thorough analysis of the battery voltage showed that there is a certain number of batteries that tend to decrease in capacity. Under the imbalance of capacity refers to the difference in the degree of charge control batteries and batteries without pressure sensors.

After switching to charge control from two other batteries with settings increased by ΔР, the decrease in capacity stopped while maintaining the unbalance value.

However, during the passage of the shadow portions of the orbit during the charge-discharge cycles, the process of increasing imbalance resumed and with the end of the shadow portions, the imbalance stabilized again.

The appearance of a number of batteries with a reduced capacity in the battery dramatically reduces the energy capabilities and resource of the battery and the satellite as a whole.

To increase the capacity of batteries with an imbalance in capacity, another increase in the charge control settings was made. The process of unbalancing the batteries by capacity was completely stopped, however, several batteries were detected in the next shadow orbits, the discharge voltage of which was about 1-1.05 V, while the rest had a voltage of about 1.25 V.

Studies have shown that the cause of the low discharge voltage of these batteries was the occurrence of a temperature radial gradient in them. As a result of this, water “leaves” the electrolyte in the central region of the active mass (to the colder boundary regions) and, as a result, the internal resistance of the battery increases with a corresponding decrease in the discharge voltage.

In addition, when the temperature of the batteries rises above the calculated value, for this design of the battery, the phenomenon of the so-called “thermal acceleration” may develop, consisting in the fact that a further increase in temperature during recharging causes a more intense oxygen evolution from the positive electrode and increases the activity of the negative electrode , which, in turn, increases the rate of recombination of oxygen with hydrogen and intensifies heat release. As a result, the process develops with positive feedback.

The closest in technical essence is the method of operating a nickel-hydrogen storage battery as part of a geostationary artificial Earth satellite (application No. 2005122357 dated July 14, 05), which consists in monitoring the steady state self-discharge current and the state of charge of the battery using analog pressure sensors, stored in a charged the state with periodic recharges to compensate for self-discharge of the battery in solar orbits and in charge-discharge cycles in shadow orbits, moreover, the steady-state self-discharge current of the battery is maintained in the range (0.003-0.006) of its nominal capacity with the termination of the charge according to the arithmetic mean of the analog pressure sensors, the value of which provides the required steady-state self-discharge current in the mode of recharging and in the range (0.01-0.012) of the nominal capacity battery in charge-discharge cycles. This method is adopted as a prototype.

The disadvantage of this method (application No. 2005122357) is that it does not take into account the temperature operating conditions of the battery. As a result, when the battery is operated at a temperature below (10-12) ° С, the charge, when conducting charge-discharge cycles in shadow orbits, is carried out until the steady-state self-discharge current reaches the value (0.01-0.012) of the nominal battery capacity, while while, even with a steady-state self-discharge current of (0.003-0.006) nominal capacity, the battery has a capacity of the order of (0.8-0.9) Sn and its further charge will lead to an unjustified increase in temperature.

The aim of the invention is to increase the efficiency and reliability of the Nickel-hydrogen battery.

This goal is achieved by the fact that they additionally control the temperature of the battery’s seat, and the steady-state self-discharge current of the battery in the range (0.003-0.006) of the nominal capacity is maintained at a battery seat temperature below (10-12) ° C, as in the recharge mode , and when carrying out charge-discharge cycles, and at a battery seat temperature above (12-14) ° C, after the charge ceases in shadow orbits in the mode of conducting charge-discharge cycles, according to the arithmetic mean An analogue pressure sensor, the value of which provides a steady-state self-discharge current in the range (0.01-0.012) of the nominal capacity of the battery, carries out an additional pulse charge, the parameters of which (period and duty cycle of the charging current) are selected from the condition of providing an average charging current of a value greater than steady-state self-discharge current of batteries 2-3 times.

The essence of the proposed method is illustrated by drawings, where Fig. 1 shows graphs of the dependence of the self-discharge currents of the batteries on the degree of their charge, and Fig. 2 is a functional diagram of an autonomous power supply system explaining the operation of the proposed method.

In the drawing, FIG. 1, the averaged graphs of the dependence of the self-discharge currents of the NV-70 batteries (developed by Saturn OJSC, Krasnodar) on the degree of their charge relative to the capacitance ratings (SN), which are selected as the charge control nickel-hydrogen battery

In this case, graph 1 corresponds to the batteries of the battery with a seat temperature below (10-12) ° C, and graph 2 corresponds to the batteries of the battery with a temperature of the seat above (12-14) ° C. Graph 3 conditionally shows the moment of the beginning of the pulse charge.

From the point of view of long-term storage in a charged state, it is necessary to ensure minimal heat dissipation of the batteries, which eliminates the possibility of thermal acceleration and the emergence of a temperature gradient. This condition is satisfied by the operation of the batteries on a gentle branch of the self-discharge current graph and by finding the steady-state self-discharge current in the interval (0.003 ÷ 0.006) Sn. In this case, the working capacity of the battery may be less than that required for the passage of the shadowed portion of the Earth.

When switching to charge-discharge cycles in the shadow areas of the orbit to increase the working capacity sufficient to pass the shadow areas of the Earth, the arithmetic mean values of the settings are raised to the level at which the steady-state self-discharge current of the battery is in the range (0.01 ÷ 0.012) Sn, which corresponds to battery operation in the vertical section of the graph of the dependence of the self-discharge current on the degree of charge, and the degree of charge corresponds to the value of (0.8 -0.9) Sn.

In this case, after reaching the steady state self-discharge current of the battery (0.01 ÷ 0.012) Cn, the pulse charge mode is switched on, the parameters of which (period and duty cycle of the charging current) are selected from the condition of ensuring the average charging current by a value 2-3 times greater than the steady-state self-discharge current of the batteries .

For example, the self-discharge currents of the NV-70 batteries in this operating mode are (0.7-0.84) A. Therefore, the average charging current of the pulse charge must be selected in the range (1.4-2.52) A.

It was experimentally established that such a mode of recharging does not lead to further heating of the batteries and promotes the message of the battery to an additional capacity to achieve a charge level close to 0.9 Sn (or more).

At a battery seat temperature below (10-12) ° С, a transition to a steady-state self-discharge current in the interval (0.01 ÷ 0.012) Cn is not required, since at this temperature the battery capacity falls into the range (0.8-0, 9) Sn at self-discharge currents in the interval (0.003 ÷ 0.006) Sn.

A distinctive feature of such control is that the charge control law is not discrete, but continuous (analog) in nature, which allows you to take into account any nuances of battery behavior, which is impossible with the discrete nature of the settings. At the same time, despite higher heat generation, the risk of thermal acceleration and the appearance of a temperature gradient are eliminated due to the fact that the charge-discharge cycle of nickel-hydrogen batteries is an alternation of exothermic reactions with heat generation at the discharge and endothermic ones with heat absorption in the first phase of the charge to achieve a voltage corresponding to thermoneutral. Thus, in the regime of charge-discharge cycles, conditions are provided for a higher charge without the occurrence of a temperature gradient.

In the drawing, figure 2, shows a functional diagram of an autonomous power supply system, explaining the work of the proposed method.

The device contains a solar battery 1 connected to the load 2 through a voltage converter 3, a battery 4 connected through a charging converter 5 to the solar battery 1, and through a discharge converter 6 to the input of the output filter of the voltage converter 3.

At the same time, load 2 in its composition contains an on-board computer, a telemetry system and a command-measuring radio line.

In parallel with the battery 4, a battery monitoring device 7 (in particular, the pressure of the batteries, which determines their current capacity and the temperature of the battery’s seat) is connected to the battery, connected to the input with the battery 4, and the output to the load 2 (with the on-board computer).

A measuring shunt 8 is installed in the charge-discharge circuit of the battery.

The charging converter 5 consists of a control key 9 controlled by a control circuit 10, a boost booster made on a transformer Tr, transistors T1 and T2 and a rectifier on diodes D1 and D2.

Bit Converter 6 consists of a control key 11, controlled by a control circuit 12.

The voltage converter 3 consists of a control key 13, controlled by a control circuit 14, an input filter C1 and an output filter on a diode D, inductor L and capacitor C.

The control circuits of the converters 10, 12, 14 are made in the form of pulse-width modulators input connected to the stabilized voltage buses. The control circuit 10 of the charging Converter 5 is additionally associated with the measuring shunt 8 and the load 2.

The device operates as follows. During operation, the battery 4 operates mainly (98% of the resource) in the storage mode and periodic recharges from the solar battery 1 through the charging converter 5. This operating mode allows you to keep it in constant readiness in case of emergencies (loss of satellite orientation on the Sun).

The load 2 is powered by a solar battery 1 through a voltage converter 3.

When passing shadow portions of the orbit or in violation of the orientation, the load 2 is powered by the battery 4 through the discharge converter 6.

The battery monitoring device 7 monitors the pressure in the batteries and transmits information about their condition to the load (on-board computer).

A program for processing analog pressure and temperature sensors and charge control is “laid in” the on-board computer:

1. The data of analog pressure sensors in “m” accumulators are processed with calculation of the arithmetic mean value of pressure (or degree of charge).

2. The arithmetic mean pressure “m” of the batteries (or degree of charge) is compared with the values of the upper and lower pressure settings embedded in the charge control logic. If the upper set point is exceeded, the charging converter is turned off; if it decreases below the lower set point, it is turned on again.

3. The steady-state value of the self-discharge current of the battery is calculated by the formula: Jc = ΔP _i / Δt, where

ΔP _i is the difference between the settings in Ah;

Δt is the self-discharge time in hours.

4. The data of the analog temperature sensors of the battery seat are processed.

5. When storing a battery with periodic additional charges, the settings (upper and lower) are set so that the steady-state value of the self-discharge current of batteries with analog pressure sensors is in the range (0.003-0.006) of the nominal capacity of the battery, and when carrying out charge-discharge setting cycles are adjusted to a level that ensures that the value of the steady-state self-discharge current is in the range (0.01-0.012) of the nominal capacity of the battery, provided that the landing temperature battery space above (12-14) ° C.

6. After the battery charge is turned off, at a battery seat temperature above (12-14) ° C, the pulse charge mode is activated, which compensates for the current self-discharge and provides an effective (without heating) message of additional capacity.

Thus, the proposed method of operating a nickel-hydrogen storage battery allows the latter to be maintained at a high level of charge (up to 0.9 Sn and higher) during the passage of shadow orbits and to provide storage in a charged state in solar orbits without compromising performance and, therefore, increasing efficiency the use and reliability of operation of a nickel-hydrogen storage battery, as well as the reliability of an autonomous power supply system and a satellite as a whole.

Claims (1)

A method of operating a nickel-hydrogen storage battery as part of a geostationary artificial satellite of the Earth, which consists in monitoring the steady-state self-discharge current and the degree of charge of the battery using analog pressure sensors, storing it in a charged state with periodic recharges to compensate for self-discharge of the battery in solar orbits and in conducting charge -bit cycles in shadow orbits, and the steady-state self-discharge current of the battery is maintained in in the range of 0.003-0.006 of the nominal capacity with the termination of the charge according to the arithmetic mean of the analog pressure sensors, the value of which provides a steady-state self-discharge current in the mode of recharging and in the range of 0.01-0.012 of the nominal capacity of the battery in the mode of charge-discharge cycles, characterized in that additionally control the temperature of the battery seat, and the steady state self-discharge current of the battery in the range of 0.003-0.006 of the nominal capacity of support at a battery seat temperature below 10-12 ° C, both in recharge mode and during charge-discharge cycles, and at a battery seat temperature above 12-14 ° C, after the charge ceases in shadow orbits in the holding mode charge-discharge cycles according to the arithmetic mean of the analog pressure sensors, the value of which provides a steady-state self-discharge current in the range of 0.01-0.012 of the nominal capacity of the battery, an additional pulse charge is carried out, the parameters of which (ne the period and duty cycle of the charging current) is selected from the condition of ensuring the average charging current in magnitude 2-3 times greater than the steady-state self-discharge current of the batteries.

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