RU2297706C2 - Artificial earth satellite power system - Google Patents

Abstract

FIELD: space power engineering.

SUBSTANCE: proposed system has sectionalized solar battery and individual series voltage regulator that incorporates extreme power regulator and is installed at input of each section. Voltage equal to optimal value of section current-voltage characteristic (CVC) is set across regulator input (across battery section output) and regulated voltage equal to load voltage, across output. All outputs of regulators are connected to load collecting bus. 100% power takeoff is ensured at all changes in section CVC for all battery components.

EFFECT: enhanced power capacity of solar battery.

1 cl, 8 dwg

Description

The present invention relates to the field of space energy, and more particularly to on-board power supply systems (BOT) of an artificial Earth satellite (AES) with solar panels (BS).

Known EPPs with sequential voltage stabilizers (SN) in the BS circuit are the load equipped with extreme power regulators (ERMs), for example, according to French patents No. 2684434, US No. 5609430 or RF patent No. 2101831 of 11.21.95. The principle of operation of the stabilizer with extreme BS power control is that the voltage at its input means, and a solar battery mounted in a point of the current-voltage characteristic (IV characteristic) corresponding to its maximum power at the current time (P _{BS OPT),} and the output voltage supported etsya stable and corresponds to a predetermined stable voltage at the load (U _STAB).

U _{BX SN} = U _{BS OPT}

U _{OUT CH} = U _STAB

The voltage regulation on the BS at the optimal point of its CVC is carried out by changing the charge currents or discharge of the battery.

This system provides conditions for the removal of maximum power from the BS in changing operating conditions of the BS in terms of illumination, temperature, and resource degradation, thereby increasing the energy capabilities of the solar cells.

As a rule, a solar battery is structurally composed of individual parts on which electrical sections are located as part of one or more electrical generators. For Sun-oriented BS, this can be one or two wings, consisting of separate panels, stacked in packages when the satellite is put into orbit. For non-oriented BSs, these can be flat or curved surfaces oriented in a certain way relative to the satellite’s body, and when designing such BSs, they try to ensure that the photoconverters within the same generator are as uniformly illuminated by the Sun and have the same temperature. Under these conditions, it is theoretically possible to achieve the ratio:

Here R _BS - the total power of the BS;

R _{BS i OPT} - the power of the i-th section of the BS at the optimal operating point of its CVC;

n is the number of BS sections.

However, to fulfill this ratio, it is necessary that all components of the BS have the same optimal voltage values. In addition, it is also necessary to fulfill one more condition: all BS component parts must have the same resource degradation, i.e. so that their current-voltage characteristics change synchronously. However, in real conditions this cannot be achieved, therefore, the effect of extreme regulation of the common BS bus will always be not 100%, i.e.

To illustrate this by way of example in Figure 1 shows a two-section BS ratio parameter, wherein at the relevant point in time section 1 (CVC BS1) and 2 (CVC BS2) have different optimum values of voltage (U opt _BS1 and _BS2 respectively U opt) for example, due to different lighting conditions or uneven resource degradation. Curves 1 and 2 of the corresponding change in power of BS1 and BS2, as well as curve 3 of the total power of BS1 and BS2, when the sections are connected to a common BS bus at the input of the stabilizer, are also shown here. The maximum value of the power of the BS corresponds to point A on curve 3 at U opt _BS , while the energy capabilities of the components of the BS provide the value:

P _{BS MAX} = P _{OPT BS 1} + P _{OPT BS2}

It is seen that P _{BS OPT} <P _{BS MAX} , and the difference between them can be expressed approximately as:

R _{BS MAX-} R _{BS OPT} = I _BS2 (U _{BS2 OPT-} U _{BS1 OPT} )

The closest agreement between the R _{BS MAKS} and the R _{BS OPT is} achieved for oriented BSs on geostationary spacecraft, where the operating conditions of the BS components are quite stable and predictable, and the greatest discrepancy is for non-oriented BSs, where at any time the BS components are in different conditions light and temperature. From this we can conclude that the principle of extreme regulation of the power of the solar battery is not universal, and in most cases the extremum of power P _{BS OPT is} less than its maximum.

Power systems are also known in which the solar battery is electrically divided into a number of sections, and voltage regulation is carried out individually for each section. An example of such a SES is the system described in the article by L. Croci, P. Galantini, C. Marana. A POWER SUBSYSTEM FOR A TELECOMUNICATION SATELLITE. (Proceedings of the European Space Power Conferece held in Graz, Austria, 23-27 August 1993 / ESA WPP - 054, August 1993 /.

The specified BOT is taken as a prototype.

The system uses partitioned solar batteries (SA5-SA16) connected via decoupling diodes to the main bus of the system (Main Bus), and shunt voltage regulators (Shunt5-Shunt10) connected in parallel to each battery section, connected to the busbar through discharge devices (BDR) rechargeable batteries (BTR), special (charging) sections of the solar battery (SA1-SA4) are connected to them through chargers (BCRE).

Shunt stabilizers and discharge devices in the complex provide the necessary voltage stabilization on the busbar to which the consumers are connected, in all operating modes, both when powered by a solar battery and when batteries are discharged when the satellite is in the shadow of the Earth or in other cases when the power of the solar battery is not enough to power the load, for example during maneuvers of a satellite. In all modes of operation, a stabilized voltage is maintained on the busbar.

Under stationary operating conditions, in particular, on high-orbit satellites with solar panels oriented to the sun, when the parameters of the BS sections are stable in time and close to their calculated values, the SES has rather high energy characteristics, namely:

- relatively insignificant losses of energy of the solar battery, caused only by voltage losses at the decoupling diodes (D) and the cost of power to control the keys of the shunt stabilizers;

- high efficiency of energy conversion of rechargeable batteries, achieved through the use in BCRE and BDR of modern electronic components and optimal circuit solutions.

However, on the other hand, the system in question has the disadvantage that it limits the use of the potential of the solar battery. This limitation is due to the fact that an integral property of the shunt control of the BS voltage is the forced maintenance of the voltage at the battery output equal to the value of the stable voltage on the load power bus (U _STAB ).

Let us explain this in more detail.

When designing a solar battery, its parameters are calculated in such a way that during the calculated period of time, after exposure to the BS of all space factors causing the degradation of the characteristics of photoconverters (radiation, ultraviolet, micrometeorites, etc.) and in the worst operating conditions (orientation, temperature), the voltage BS buses, supported by a shunt stabilizer, coincided with the voltage corresponding to the optimum operating point of the CVC of the BS:

U _{BS OPT} = U _STAB

Since the same voltage is supported on all BS sections, the indicated condition must be satisfied for each section.

This equality can be achieved only theoretically and only at a single moment of the satellite’s existence and in real practice is not ensured. As a rule, BS developers provide some safety margin for unforeseen cases, so that for the worst case, it is guaranteed to provide the ratio:

U _OPT ≥U _STAB

And this means that in all cases the system does not allow to take its maximum power from the BS.

To an even greater extent, a mismatch will occur for non-oriented BS due to different lighting conditions and temperature of the components.

The proposed solution eliminates the disadvantages of analogues and prototype and its essence is as follows:

- BS is divided into n sections in such a way that the conditions of constant illumination and temperature for all photoconverters are satisfied within one section;

- each section is equipped with a voltage stabilizer with extreme power control of the section by setting the voltage on it corresponding to the optimal voltage of its I-V characteristic, and at the output of the stabilizer a stable voltage is maintained equal to the required voltage on the busbar.

- the outputs of the regulators are connected to the busbar, the voltage on which is equal to the voltage at the output of the regulators.

The block diagram of the proposed BOT is shown in figure 2.

BOT consists of n sections 1 of the solar battery (BS _1- BS _n ) connected via n current sensors 2 and n sequential voltage regulators 3 with extreme power regulators 4 to the busbar 5, the battery 6 connected to the charger 7 and the discharge device 8, which are connected to the busbar 5 by other inputs, and the load 9 is connected to the busbar. Each extreme power regulator 4 is connected to a corresponding current sensor 2 and stabilizer 3, as well as to a charging 7 and a discharge 8 devices. A common output all sections of the BS are interconnected, the battery and the load. The diagram shows the voltage at the output BS sections (U -U _{BS1 BSn),} and the voltage on the busbar U _STAB.

BOT works as follows.

With a fully charged battery, the voltage on each section of the BS is set based on the actual ratio of the load power to the BS, i.e. stabilizers SN _i limit the voltage on the sections of the BS to a level at which the ratio is provided:

where η _CHi is the stabilizer efficiency.

With a small load, the voltage in the sections approaches the values of the open circuit voltage (U _XXi ); and with its increase - to U _{OPT i} . If it is necessary to charge (turn on the charger) or if the load power increases above the maximum total power of the BS sections and the discharge of the battery, extreme power regulators of the BS sections (ERM _i ) are activated, and each of them sets the voltage corresponding to the P _{BSi OPT} at the input of its section . T.O. the charge current of the battery increases and is set at the maximum level determined by the charging power from the ratio:

When discharging AB (inclusion of RU), the value of the discharge current is set at the minimum level determined by the discharge power from the ratio:

In the proposed system, for any current changes in the CVC of individual BS sections, the condition is always satisfied:

As an example, Fig.6-8 shows the results of the calculation of the changes in the parameters of the BS on a revolution for a low-orbit spacecraft, oriented by one axis to the Earth. The calculation was performed for the use of silicon photoconverters with known temperature dependences of the parameters on temperature and for the most critical case of the satellite in orbit with a maximum duration of the shadow region, i.e. when the direction to the sun coincides with the plane of the orbit. BS is made in the form of 4 hinged panels installed at an angle of 45 degrees to the longitudinal axis - X KA, see Fig.3-5. Here, FIG. 3 shows a side view of a spacecraft with BS panels, and FIG. 4 is a top view. The numbers indicate the numbers of the BS panels. Figure 5 shows the position of the spacecraft in orbit with respect to the Earth and the solar flux (shown by arrows). The shaded part is the shaded area of the orbit. Figure 6 shows the change in temperature of the panels during the turn (the numbers correspond to the designations of the numbers of the panels in Figs. 3, 4), and in Fig. 7 - the change in the total power of 4 panels. The calculations were performed for 3 options for regulating the voltage of the BS:

1. BS operates at the point of removal of the maximum power of the overall CVC of the BS (analog of the BOT)

2. BS sectional, operates at a stable voltage of 30 V (prototype SES)

3. Each panel of a sectional BS is regulated at the point of optimal power of its I-V characteristic (according to the invention)

On Fig further explains the formation of the CVC of the BS panels for one fixed time, namely, corresponding to the angular position of the satellite in orbit φ = 160 degrees. For this point in time, the BS power values corresponding to the above application cases are equal to:

1) 82.5 units; 2) 78.5 units; 3) 89 units.

Here, the current and power values are indicated in arbitrary units. One conventional unit is equal to the current or, accordingly, the power taken from one panel with a perpendicular incidence of sunlight and a panel temperature of 40 ° C. The values of the average over the illuminated part of the turn of the power of the BS (figure 5) were respectively:

1. In the BOT, made by analogy (BS non-sectional, with optimal voltage on the common bus BS) 48.2 units.

2. In the EPA, made according to the prototype (BS sectional, stable voltage in each section) 45 units

3. In the BOT according to the proposed option (BS sectional, with optimal voltage in each section) 55.5 units

Thus, for the considered design option of the BS and the spacecraft type, the effect of the proposed solution is expressed in an increase in the average power revolution of the BS by 15% compared to the analogue and by 23% with the prototype.

It is planned to use the proposed power supply system at PM KA developed by NPO.

Claims (1)

AES power supply system, consisting of a partitioned solar battery, a busbar with a load connected to it, a battery connected to the busbar via a charging and discharge device, characterized in that each section of the solar battery is connected to the busbar through an autonomous current sensor, autonomous stabilizer voltage, equipped with an extreme power regulator connected to the aforementioned current sensor, charging and discharge devices, and the outputs of the stabilizers are connected to the busbar.

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