RU2313169C2 - Off-line power supply system - Google Patents

Abstract

FIELD: space power engineering.

SUBSTANCE: proposed off-line power supply system designed for feeding artificial earth satellites has solar battery connected to load through series-connected voltage regulator, storage battery connected through charger to solar battery output and through discharger, to series-connected voltage regulator output, input capacitive filter connected in parallel with solar battery output, and output inductive-capacitive filter at load input; connected in parallel with solar battery output buses is solar battery maximal limiter which opens circuit as soon as voltage rises to operating threshold and starts passing current whose magnitude varies so that sum of currents through limiter and through load correspond to point on solar-battery current-voltage characteristic at which solar battery output voltage equals limiter setting value.

EFFECT: optimized power system, enlarged its functional capabilities.

3 cl, 6 dwg

Description

The present invention relates to the field of space energy using solar panels, specifically to devices for regulating the voltage on the tires of the solar battery and load in autonomous power systems of artificial Earth satellites satellites.

Known autonomous power supply systems (BOT) of the satellite, for example, according to A.S. 1106407 dated 04/12/83. The system contains a solar battery (BS) connected to the voltage regulator through isolation diodes and a capacitive filter, a load connected to the regulator through an inductive-capacitive filter, and the control unit controls the operation of the regulator. The disadvantage of the system is that it provides power to the load only if there is a solar battery power exceeding the load power, because there is no additional energy source in the system - a rechargeable battery (AB).

Closest to the proposed invention is a stand-alone BOT, described in the monograph of the Power supply system of spacecraft. Novosibirsk, IN "SCIENCE". 1994. Authors B.P. Sustin, V.I. Ivanchura, A.I. Chernyshev, Sh.N. Islyaev (see Fig. 1.19, Section 1.5). The specified power supply system, a block diagram of which is shown in figure 1, is adopted as a prototype. BOT consists of a solar battery (BS) 1 as a primary energy source, a storage battery (AB) 2 as a secondary source, a series voltage stabilizer (CH) 3 connected between BS 1 and load 4, charging (charger) 5 and discharge ( RU) 6 devices AB, and the input of the charger is connected to the output of the BS, and the output of the discharge device is connected to the output of CH. A capacitive filter 7 is connected between the plus and minus outputs of the BS, and an inductive-capacitive filter 8 is output at the SN output.

The system works as follows

When the power of the solar battery 1 exceeds the power of the load 4, and when the battery is fully charged 2, the voltage at the load is regulated by SN 3. The voltage at the input of CH 3 (at the output of BS 1) is set at the point of the current-voltage characteristic (CVC) of the BS, determined by the ratio :

U _BS · I _BS = U _H · I _H = P _H ,

where U _BS , I _BS - voltage and current of the BS,

U _H , I _H , P _H - voltage, current and load power, respectively.

As P _H → 0, U _BS → U _XX , i.e. when the load tends to zero, a voltage close to idle will be established at the BS output (see Fig. 3, load characteristic 3), and vice versa, with an increase in load U _BS → U _H. If necessary, charge the battery charger 5.

When the battery is charged with all the excess BS power, U _BS = U _H + ΔU _CH , where ΔU _CH is the voltage drop across the open key SN. At this voltage, the ratio will be established:

P _BS = P _H + P ₃ ;

U _BS · I _BS = U _H · I _H + U ₃ · I ₃ ,

where U _З , I _З , P _З - voltage, current and battery power, respectively.

When the BS power decreases, for example, when the satellite enters the Earth’s shadow or when the load power increases beyond the BS capabilities (P _H > P _BS ), the voltage control on the load is provided by RU 6 with the CH 2 key fully open, i.e. U _BS = U _RU + ΔU _CH , where U _RU is the voltage at the output of the discharge device, and ΔU _CH is the voltage drop across the stabilizer key.

The input capacitive filter (7) is designed to reduce the ripple of the BS 1 voltage at the input to the CH 3, the output inductive-capacitive filter 8 is used to provide the required quality of voltage at the load 4 in stationary and transient modes.

The indicated autonomous BOT is widely used in domestic satellites in various orbits, has shown high reliability and efficiency of using the potential of current sources, high stability of the output voltage (U _H ) under any dynamics of load changes and external conditions (variable BS orientation, passage of shadow sections of the orbit and etc.).

At the same time, it has drawbacks arising from the specifics of regulating the voltage (power) of the BS, which limit the scope of such BOTs, especially when switching to higher values of the supply voltage (70-100 V and above).

In the process of flight operation during the passage of the shadow sections of the orbit, the solar battery undergoes thermal cycling, cooling at the end of the shadow section, for example, in a geostationary orbit from about plus 40 to minus 180 ° C.

In accordance with the properties of semiconductor photovoltaic converters, a cooled solar battery after a satellite leaves the Earth’s shadow has a significantly higher voltage than at a steady temperature when illuminated by the Sun.

The maximum open-circuit voltage (U _XX ) of the cooled BS immediately after the satellite leaves the Earth’s shadow can be written as:

- температурный коэффициент напряжения холостого хода от фотопреобразователей,here

- temperature coefficient of open circuit voltage from photoconverters,

Δt = Δt _RAB -t _MIN , i.e. the difference between the steady-state operating temperature in the illuminated portion of the orbit and the minimum temperature at the satellite exit from the Earth’s shadow;

K _RES - voltage reserve for the service life;

To _XX - the ratio of U _XX / U _{slave BS} .

Changes in the temperature and shape of the current-voltage characteristic (CVC) of the solar battery during the passage of the shadow portion of the orbit are shown in FIGS. 2 and 3, respectively.

CVC 1 of FIG. 3 corresponds to time point 1 on the temperature curve of FIG. 2, and CVC 2 corresponds to point 2 on the same curve.

As an example, consider the conditions for using BS:

- geostationary orbit;

- type BS - silicon photoconverters;

- t _RAB = + 50 ° C; t _MIN = -180 ° C;

- K _RES ≈1.2;

- K _XX ≈1.25;

- ∂U _XX / ∂t · U _XX = -0.004 1 / ° С.

Hence, U _{XX MAX} = 2.88 U _H.

Those. the power supply system must be designed to operate in the BS voltage range from U _H to 2.88 U _H. For example, with U _H = 100 V, this range is 100-288 V.

This leads to the following disadvantages.

1. The efficiency and specific gravity characteristics of the solar cells (W / kg) are reduced due to the non-optimal operation of the converters and voltage stabilizers (SN, ZU), forced to work in a wide voltage range.

2. There are increased requirements for BOT electro-radio elements installed at the BS output (capacitors, transistors, etc.), which makes the circuit more complicated and reduces its reliability. In particular, in the input filters it is necessary to apply a series connection of capacitors with a corresponding increase in mass. Thus, the indicated property of the SES circuits with a series voltage stabilizer BS limits the scope of such systems to voltage levels, permissible capacities of radio electronic elements.

In the present invention, these drawbacks are eliminated by introducing a BS voltage limiter parallel to the solar battery in the solar cell circuit, the role of which is to limit the voltage cooled in the shadow of the BS to a level acceptable for the elements used in the power supply system. This level should be selected in the range U _H · K _RES · K _XX <U _OGR <U _{XX MAX} .

As shown above, in the case of using the system on a geostationary satellite, the upper voltage level at the BS can be limited to 1.5U _H , i.e. significantly lower BS open circuit voltage (2.88 U _H )

Thus, at U _H = 100 V, the voltage of the limiter can be set at 150 V.

The duration of the limiter is determined by the heating time BS t _NAGR , which according to the calculations and flight measurements is 5-8 minutes, i.e. for a geostationary orbit, the total operating time of the limiter will not exceed 12 hours per year.

The essence of the invention is illustrated in figure 4-6.

The proposed system consists of a solar battery 1, a battery 2, a series voltage stabilizer 3, connected to the circuit between the solar battery 1 and the load 4, the battery 2 is connected through the charger 5 to the output of the solar battery and through the discharge device 6 to the output of the stabilizer. An input filter 7 is installed in parallel with the solar battery, and an inductive-capacitive filter 8 is installed between the outputs of the stabilizer 3 and the discharge device 6 on the one hand and the load 4 on the other. A limiter 9 of the maximum voltage of the solar battery 1 is installed parallel to its outputs to the output of the solar battery.

The operation of the circuit is as follows.

After the satellite leaves the Earth’s shadow for about one minute (twilight period), the current and voltage of the solar battery increase from zero to maximum values. When the threshold voltage of the limiter 9 is reached, it opens and starts passing a current through itself, the value of which changes so that the sum of the shunt current (i.e., the current through the limiter) and the current to the load corresponds to a point on the BS current-voltage characteristic at which BS output voltage is equal to the limiter setpoint voltage.

As its voltage limiter, any type can be used, for example, a linear stabilizer. The block diagram of the SES with such a limiter 9 is shown in figure 4.

You can also apply a shunt limiter (SHO) with pulse-width modulation (PWM), which is based on a transistor switch. In this case, to protect the transistor switch of the SHO from high currents when the input filter capacity is discharged, a diode 10 is installed in the forward direction of the BS current passage to the connection point of the input filter SN in the BS output circuit. The block diagram of the BOT with SHO is shown in figure 5. The operation of the circuit is similar to the work described above in FIG. 4, with the difference that here the voltage at the output of the BS is carried out by the pulse operation of the SHO key.

In those cases when the voltage drop across the diode is a critical parameter for the BOT and it is necessary to exclude additional power losses of the BOT on it, a switch 11 is installed in parallel with the diode, which is closed during those periods of time when the SHO does not work (the SHO key is closed).

The block diagram of the SES with the switch is shown in Fig.6. The switch is closed continuously, except for periods of operation of the SHO in the voltage limiting mode. To simplify the management of the switch in a real BOT, it can be turned off when the satellite enters the Earth’s shadow and turned on 5-8 minutes after leaving the shadow, or it can be turned off for a longer period, for example, for a geostationary orbit for the entire period of shadow orbits, i.e. . twice a year for 45 days each.

The proposed stand-alone power supply system is planned for use at one of the enterprise’s development satellite.

Claims (3)

1. Autonomous satellite power supply system, including a solar battery connected through a series voltage stabilizer to the load, a battery connected through a charger to the output of the solar battery and through a discharge device with the output of a series voltage stabilizer, an input capacitive filter connected in parallel with the output of the solar battery and output inductive-capacitive filter at the input to the load, characterized in that a facet is connected parallel to the output buses of the solar battery an indicator of the maximum voltage of the solar battery, which opens when the threshold voltage is reached and starts passing a current through it, the value of which changes so that the sum of the currents through the limiter and the current to the load corresponds to a point on the current-voltage characteristic of the solar battery, at which the output voltage of the solar the battery is equal to the voltage limiter setting. 2. The self-contained satellite power supply system according to claim 1, characterized in that a shunt voltage limiter with pulse-width modulation is installed as a voltage limiter, and a diode is installed between the limiter input and the input capacitive filter in the forward direction of the solar cell current flow. 3. Autonomous satellite power supply system according to claim 2, characterized in that a switch is installed parallel to the diode.

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