SAR satellite power system and control method thereof

Abstract

The present invention relates to a power system applied to a Synthetic Aperture Radar (SAR) satellite and a control method thereof. More specifically, it relates to a power system for a SAR satellite and a control method thereof that considers the load characteristics of a SAR satellite in which high-power loads such as radar antennas, intermediate-power loads such as thrusters, and low-power loads such as sensors and electronic equipment are mixed, and configures high-voltage and low-voltage batteries in a dual configuration, and efficiently controls the power flow to stably supply a voltage suitable for each load characteristic.

Description

Technology Field

[0001] The present invention relates to a power system applied to a Synthetic Aperture Radar (SAR) satellite and a control method thereof. More specifically, the invention relates to a SAR satellite power system and a control method thereof that efficiently controls the power flow to stably supply a voltage suitable for each load characteristic, by configuring high-voltage and low-voltage batteries in a dual configuration considering the load characteristics of a SAR satellite in which high-power loads such as radar antennas, intermediate-power loads such as thrusters, and low-power loads such as sensors and electronic equipment are mixed. Background Technology

[0002] Generally, SAR satellites possess a complex power demand structure that includes high-power loads requiring very high instantaneous power to drive radar antennas, as well as medium-power loads such as thrusters and low-power loads such as sensors and electronic equipment. Nevertheless, conventional SAR satellite power systems have primarily adopted a single-voltage-based structure that supplies all loads from a single power system, failing to adequately consider the specific power requirements of each load.

[0003] Figures 1 and 2 are schematic diagrams showing the power system of a conventional SAR satellite.

[0004] Referring to Figures 1 and 2, it can be seen that the power generated from the solar cell array is converted into a single bus voltage through a power regulator and a shunt regulator, then stored in a single battery pack, and the stored single voltage is distributed commonly to the SAR payload and platform load. This single battery and bus-based power architecture has been applied in many existing studies, and the method in which all loads are powered through a single voltage bus has become the standard configuration of conventional SAR power systems. Prior art literature

[0005] (특허문헌 0001) KR 10-1086752 B1, 2011.11.18.US 4,494,063 B2, 1985,01.15.US 5,359,280 B2, 1994.10.25.

[0006] Bronzini A. S., Li Z., Wang Y. 외, "Design of Power Supply System for High Power SAR Satellite," Journal of Physics: Conference Series, 제2361권, 제1호, 2022, doi:10.1088 / 1742-6596 / 2361 / 1 / 012016.Chen X., Zhang Y., Liu H., Zhou D., "A Fast-Dynamic Response Control Strategy for Power Supply Unit of SAR Satellites," Proceedings of ICEPE 2020, 2020, pp. 1-6.Liu J., Wang H., Chen X., Zhang Y., "Research on a Power Supply Scheme of Composite Bus for SAR Satellite," Proceedings of the China International SAR Symposium (CISS 2021), 2021, pp. 1-5.Zhang Y., Liu J., Wang H., Chen X., "The Influence of SAR Satellite Load Boot on Power Converter and Its Analysis," Proceedings of the China International SAR Symposium (CISS 2021), 2021, pp. 1-6. 해결하려는 과제

[0007] However, such single-voltage-based power systems have several technical limitations when considering the diverse load characteristics of SAR satellites. While high-power SAR antennas exhibit excellent power transfer efficiency when operated at high voltages, low-power loads, such as sensors and platform electronics, require relatively low voltages. Nevertheless, if single-voltage batteries are used, the voltage supplied to these low-voltage loads must be reduced through a step-down converter, and the step-down ratio increases as the battery voltage rises. An increase in the step-down ratio leads to increased conversion losses and device heat generation, resulting in a decrease in overall power conversion efficiency. Particularly in SAR satellites where heat dissipation environments are limited, this inefficiency exacerbates the limitations of the system design.

[0008] Furthermore, in conventional structures based on a single bus, fluctuations in bus voltage inevitably occur when pulse loads requiring large instantaneous power, such as driving a SAR antenna, are in operation, and these voltage drops or ripples can be transmitted directly to the platform load side. This not only degrades the overall power quality of the satellite but can also directly affect the reliability of precision sensors or communication equipment that require stable operation. In addition, in a single battery structure, if the battery voltage is designed to be high to match the voltage requirements of high-output loads, step-down losses on the low-power load side increase; conversely, if the voltage is lowered towards low-power loads, overcurrent occurs when driving high-output loads, leading to a problem where the burden on the battery and power wiring increases. Consequently, the conventional single-battery and single-bus-based power architectures shown in FIGS. 1 and 2 cannot provide voltages optimized for each load in a SAR satellite environment that requires various voltage levels, which leads to structural limitations such as reduced power conversion efficiency, reduced bus stability, and reduced power quality. For this reason, conventional systems have a fundamental limitation in that it is difficult to ensure the efficiency and reliability of the entire power system in an environment where high-power and low-power loads of SAR satellites are mixed.

[0009] Accordingly, the present invention is proposed to solve the problems of the prior art, and aims to provide a power system for a SAR satellite and a control method thereof that can effectively resolve structural limitations such as increased conversion losses, bus voltage fluctuations, interference between loads, and power quality degradation associated with conventional single-voltage and single-battery based power systems in a load characteristic environment of a SAR satellite where high-power loads such as radar antennas, intermediate-power loads such as thrusters, and low-power loads such as sensors and electronic equipment are mixed. means of solving the problem

[0010] A SAR satellite power system according to an embodiment of the present invention comprises: a first charger that converts power supplied from a solar cell array into power of a first voltage level; a first battery that stores power of a first voltage level supplied from the first charger; a second charger that converts power of a first voltage level supplied from either the first charger or the first battery into power of a second voltage level; a second battery that stores power of a second voltage level supplied from the second charger; and a power conversion and distribution unit that converts power of a first voltage level supplied from either the first charger or the first battery into a driving voltage of the first load group and supplies it, and converts power of a second voltage level supplied from either the second charger or the second battery into a driving voltage of the second load group and supplies it.

[0011] Additionally, a SAR satellite power system according to an embodiment of the present invention includes: a first charger that converts power supplied from a first solar cell array into power of a first voltage level; a first battery that stores power of a first voltage level supplied from the first charger; a second charger that converts power supplied from a second solar cell array into power of a second voltage level; a second battery that stores power of a second voltage level supplied from the second charger; and a power conversion and distribution unit that converts power of a first voltage level supplied from either the first charger or the first battery into a driving voltage of the first load group and supplies it, and converts power of a second voltage level supplied from either the second charger or the second battery into a driving voltage of the second load group and supplies it.

[0012] Additionally, a SAR satellite power system according to an embodiment of the present invention comprises: a first charger that converts power supplied from a solar cell array into power of a first voltage level; a first battery that stores power of a first voltage level supplied from the first charger; a second charger that converts power of a first voltage level supplied from either the first charger or the first battery into power of a second voltage level; a second battery that stores power of a second voltage level supplied from the second charger; a first power conversion and distribution unit that converts power of a first voltage level supplied from either the first charger or the first battery into a driving voltage of the first load group and supplies it; and a second power conversion and distribution unit that converts power of a second voltage level supplied from either the second charger or the second battery into a driving voltage of the second load group and supplies it.

[0013] Additionally, a SAR satellite power system according to an embodiment of the present invention comprises: a first DC-DC converter that converts power supplied from a first solar cell array into power of a first voltage level; a first battery that stores power of a first voltage level supplied from the first DC-DC converter; a second DC-DC converter that converts power supplied from a second solar cell array into power of a second voltage level; a second battery that stores power of a second voltage level supplied from the second DC-DC converter; a first power conversion and distribution unit that converts power of a first voltage level supplied from either the first DC-DC converter or the first battery into a driving voltage of the first load group and supplies it; and a second power conversion and distribution unit that converts power of a second voltage level supplied from either the second DC-DC converter or the second battery into a driving voltage of the second load group and supplies it.

[0014] In addition, the power of the second voltage level may be a power of a voltage level lower than the power of the first voltage level.

[0015] In addition, the first battery has a higher discharge rate than the second battery.

[0016] Additionally, the first load group may include a load requiring a high discharge rate, and the second load group may include a load requiring a lower discharge rate than the first load group.

[0017] In addition, a control method for a SAR satellite power system according to an embodiment of the present invention comprises: a process of supplying power of a first voltage level charged in the first battery to the second charger; a process of converting power of a first voltage level supplied from the first battery through the second charger into power of a second voltage level to charge the second battery; and a process of converting power of a second voltage level supplied from at least one of the second charger or the second battery into a driving voltage of a second load group through the power conversion and distribution unit and supplying it to the second load group.

[0018] In addition, a control method for a SAR satellite power system according to an embodiment of the present invention comprises: a process of supplying power of a first voltage level charged in the first battery to the second charger; a process of converting power of a first voltage level supplied from the first battery into power of a second voltage level through the second charger to charge the second battery; and a process of converting power of a first voltage level supplied from the first battery into a driving voltage of the first load group and supplying it through the power conversion and distribution unit, and converting power of a second voltage level supplied from either the second charger or the second battery into a driving voltage of the second load group and supplying it to the second load group.

[0019] In addition, a control method for a SAR satellite power system according to an embodiment of the present invention includes the process of supplying power of a second voltage level charged in the second battery; and the process of converting the power of the second voltage level supplied from the second battery into a driving voltage of the second load group through the power conversion and distribution unit and supplying it to the second load group.

[0020] In addition, a control method for a SAR satellite power system according to an embodiment of the present invention comprises: a process of supplying power of a first voltage level charged in the first battery; a process of supplying power of a second voltage level charged in the second battery; and, through the power conversion and distribution unit, converting the power of the first voltage level supplied from the first battery into a driving voltage of the first load group and supplying it, and converting the power of the second voltage level supplied from the second battery into a driving voltage of the second load group and supplying it to the second load group.

[0021] In addition, a control method for a SAR satellite power system according to an embodiment of the present invention comprises: a process of converting power supplied from the solar cell array into power of a first voltage level through the first charger; a process of storing power of a first voltage level supplied from the first charger in a first battery; a process of converting power of a first voltage level supplied from either the first charger or the first battery into power of a second voltage level through the second charger; a process of storing power of a second voltage level supplied from the second charger in the second battery; and, through the power conversion and distribution unit, converting power of a first voltage level supplied from either the first charger or the first battery into a driving voltage of the first load group and supplying it, or converting power of a second voltage level supplied from either the second charger or the second battery into a driving voltage of the second load group and supplying it. Effects of the invention

[0022] As described above, according to an embodiment of the present invention, the following effects can be obtained.

[0023] First, according to the present invention, by configuring the high-voltage (HV) system and the low-voltage (LV) system with separate batteries and / or independent charging paths, the problems of interference between loads and voltage fluctuations that occurred in conventional single-battery-based power structures can be fundamentally resolved. Accordingly, low-power loads, such as platform equipment and sensors, can be operated stably even when missions requiring large power instantaneously, such as high-power SAR radar operation, are performed.

[0024] Second, according to the present invention, power conversion and distribution modules (such as PCDUs) can be independently configured for each battery, thereby individually satisfying power quality requirements for each system. In particular, the reliability of the entire system is improved by maintaining a stable voltage level suitable for high-output pulse loads in high-voltage systems and securing low-noise, low-ripple power required by small electronic equipment in low-voltage systems.

[0025] Third, according to the present invention, the solar cell array configuration can be applied in either a single array or multiple array ways, thereby providing great flexibility in power design. It supports structures ranging from deploying dedicated arrays for high-voltage and low-voltage systems to distributing from a single array to both systems via a charger, enabling optimal configuration according to mission profiles and design requirements.

[0026] Fourth, according to the present invention, the configuration is not limited to two types of batteries but can be easily expanded to a multi-battery system including three or more types of batteries. This provides the advantage of being able to optimize the battery system by subdividing mission-specific power demand in SAR satellites performing long-term missions, and can significantly improve the accuracy of power management and operational efficiency.

[0027] Fifth, according to the present invention, various power flow modes are supported depending on power supply conditions, such as solar power generation periods, eclipse periods, and high-power mission active / inactive periods. In particular, optimized control is possible depending on the situation, such as low-voltage grid assistance using a high-voltage battery during eclipse periods, and prioritizing charging or independent operation of a specific grid during solar power generation periods, thereby maximizing the stability and energy efficiency of the entire power system.

[0028] Sixth, according to the present invention, the battery system can be separated not only by voltage level but also by load characteristics (e.g., high discharge rate required load, low discharge rate required load), thereby enabling flexible response to the requirements of actual satellite equipment. This is effective in minimizing mutual interference between the SAR payload and platform equipment and can improve the precision of power quality management.

[0029] Seventh, according to the present invention, the PCDU can be configured as a single unit or multiple units depending on the design, and the internal converter / switch array can also be subdivided and arranged in modular units, thereby facilitating system implementation and maintenance. In addition, independent operation by system is possible, resulting in excellent fault isolation performance and ensuring structural stability so that a failure in a specific system does not spread to other systems.

[0030] Eighth, according to the present invention, a universal and scalable power architecture can be provided that can configure a power system to suit various mission conditions while simultaneously solving problems such as power quality, load separation, power stability, and fault tolerance, which were difficult to resolve in conventional single-battery-based power structures. This provides technical advantages applicable not only to SAR satellites but also to power systems of various spacecraft equipped with high-power payloads. Brief explanation of the drawing

[0031] Figures 1 and 2 are drawings showing the power system of a conventional SAR satellite. FIG. 3 is a diagram showing the power system configuration of a SAR satellite according to the prior art. FIG. 4 is a diagram showing the power system configuration of a SAR satellite according to an embodiment of the present invention. FIG. 5 is a diagram showing a control method for a SAR satellite power system according to a first example of the present invention. FIG. 6 is a diagram showing a control method for a SAR satellite power system according to a second example of the present invention. FIG. 7 is a diagram showing a control method for a SAR satellite power system according to a third example of the present invention. FIG. 8 is a diagram showing a control method for a SAR satellite power system according to the fourth example of the present invention. FIG. 9 is a diagram showing a control method for a SAR satellite power system according to the fifth example of the present invention. FIG. 10 is a diagram showing a control method for a SAR satellite power system according to the 6th example of the present invention. FIG. 11 is a diagram showing a control method for a SAR satellite power system according to the 7th example of the present invention. FIG. 12 is a diagram showing a SAR satellite power system according to Variant Example 1 of the present invention. FIG. 13 is a diagram showing a SAR satellite power system according to Variant Example 2 of the present invention. FIG. 14 is a drawing showing a SAR satellite power system according to Variant Example 3 of the present invention. Specific details for implementing the invention

[0032] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms, and the embodiments of the present invention are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention. In the drawings, like reference numerals refer to like elements.

[0033] Figure 3 is a schematic diagram showing the configuration of a SAR satellite power system according to the prior art.

[0034] Referring to FIG. 3, in a power system of a SAR satellite according to the prior art, power generated from a solar cell array (1) is regulated through a charger (2) and then stored in a single battery (3). The power stored in the single battery (3) is output to a single common power node, and a plurality of power conversion units (4, 5) are connected in a parallel structure to this common power node. Each power conversion unit (4, 5) converts and outputs a common voltage to match the load characteristics in order to supply power to loads (6, 7) with different voltage and power requirements, such as SAR payload loads or platform loads. A conventional SAR satellite power system configured in this way is composed of a single voltage-based structure that forms a single common power node centered on a single battery (3), so that all loads (6, 7) receive the same battery voltage as power from the single battery (3), regardless of the type of load or the voltage requirement. In other words, the characteristic of the prior art is that it adopts a single voltage architecture in which the entire load shares a single voltage bus.

[0035] The SAR satellite power system of the present invention comprises a basic power system consisting of a solar cell array, a high-voltage (HV) battery, a low-voltage (LV) battery, and a dedicated charger for charging each battery. Additionally, the SAR satellite power system is equipped with a Power Conversion and Distribution Unit (PCDU) that performs power conversion and distribution functions. The PCDU may include a converter unit that performs various voltage conversion functions and a switch unit that controls power connections between loads or batteries; if necessary, these components may be arranged in the form of a converter array or a switch array. Through these components, the PCDU plays a key role in converting and supplying power to the voltage level required by each load, or in appropriately connecting and controlling the power flow between batteries and loads.

[0036] FIG. 4 is a schematic diagram illustrating the configuration of a SAR satellite power system according to an embodiment of the present invention, schematically showing the overall configuration in which power generated from a solar cell array (11) is sequentially supplied to a high-voltage battery (13) and a low-voltage battery (15).

[0037] Referring to FIG. 4, power generated from a solar cell array (11) is supplied to a first charger (12). The first charger (12) converts the power supplied from the solar cell array (11) into a voltage and current suitable for charging a high-voltage battery (13) and outputs it. The converted power is branched into a first path supplied to the high-voltage battery (13) and a second path supplied to a second charger (14).

[0038] Power stored in the high-voltage battery (13) through the first path stably secures high-voltage power for driving a load (17, hereinafter referred to as 'high-power load') that requires high-voltage operation, such as a SAR radar transmitter. The output of the high-voltage battery (13) is transmitted to the PCDU (Power Conditioning and Distribution Unit, 16), and the PCDU (16) distributes the power to the high-power load (17) and maintains and adjusts the voltage and current according to the operating characteristics of the load so as to stably supply the high-power pulse required for driving the radar antenna.

[0039] The power delivered via the second path is converted by the second charger (14) into voltage and current conditions suitable for charging the low-voltage battery (15). The second charger (14) receives power from the downstream end of the first charger (12) and is responsible for charging the low-voltage system. The charged low-voltage battery (15) stores and supplies power required for loads (18, hereinafter referred to as 'low-power loads') that operate at relatively low voltages, such as platform electronic equipment, sensors, and communication modules. The power provided from the low-voltage battery (15) is also input to the PCDU (16), and the PCDU (16) separates and distributes it into power suitable for the low-power loads (18). In this process, the PCDU (16) blocks voltage interference between the high-voltage system and the low-voltage system and manages each voltage level independently to control the supply of stable power to all loads.

[0040] Through this configuration, the SAR satellite power system according to the embodiment of the present invention has a step-by-step power processing structure in which power from a solar cell array (11) is first converted at a first charger (12), and then power is supplied to a second charger (14) to charge a low-voltage battery (15) while simultaneously charging a high-voltage battery (13). That is, the high-voltage battery (13) and the low-voltage battery (15) are not directly branched in parallel from the solar cell array (11), but rather have a structure in which power is transferred sequentially (step-by-step) centered around the first charger (12). This structure allows the system to operate organically by maintaining electrical separation between the two batteries and distributing the two voltage systems according to their respective load characteristics at the PCDU (16).

[0041] Accordingly, the SAR satellite power system according to an embodiment of the present invention eliminates step-down conversion losses that inevitably occur in conventional single-battery and single-voltage-based structures, and structurally prevents the problem of bus voltage fluctuations occurring during high-output load operation being transmitted to the low-power load side. In addition, by individually providing voltage levels suitable for each load in a SAR satellite environment where voltage and power requirements differ for each load, the efficiency of the entire power system, the stability of power quality, and operational reliability can be significantly improved.

[0042] Hereinafter, a control method for a SAR satellite power system according to an embodiment of the present invention will be described.

[0043] FIG. 5 is a diagram illustrating a control method for a SAR satellite power system according to the first example of the present invention, and explains an operation process in which a low-voltage battery (15) is insufficient in the remaining charge amount when power is not supplied from a solar cell array (11), such as during an eclipse, by using a high-voltage battery (13) to assist the low-voltage system.

[0044] During the solar eclipse period, the output of the solar cell array (11) is reduced or completely cut off, so the first and second chargers (12, 14) can no longer receive sufficient power from the solar cell array (11). Under these conditions, the low-voltage battery (15) continues to consume stored power to drive the low-power load (18), and discharge proceeds over time. Eventually, when the charge of the low-voltage battery (15) drops below a predetermined standard, it reaches a state where it is difficult to stably maintain the low-power load (18) using only the low-voltage battery (15).

[0045] Under these conditions, in the control method according to the first example of the present invention, the high-voltage battery (13) is utilized as an auxiliary power source for the low-voltage system. As shown in FIG. 5, the output of the high-voltage battery (13) is supplied to the second charger (14), and the second charger (14) adjusts it to a voltage and current suitable for charging the low-voltage battery (15). That is, normally, the second charger (14) receives power supplied from the solar cell array (11) to charge the low-voltage battery (15), but in a situation where sunlight is blocked, such as during a solar eclipse, it performs a dual operation of receiving the output of the high-voltage battery (13) as input to charge the low-voltage battery (15).

[0046] Accordingly, the SAR satellite power system according to the embodiment of the present invention can stably maintain the low-voltage system through the high-voltage battery (13) even when the charge of the low-voltage battery (15) is insufficient. This means that even though the high-voltage system and the low-voltage system are physically separated, energy transfer between the two power systems is flexibly achieved through the cooperative control of the PCDU (16) and the second charger (14). This control method can provide the effect of increasing the stability and reliability of the entire power system by enabling the continuous operation of low-power equipment even in harsh environments where external power supply is limited, such as during a solar eclipse.

[0047] FIG. 6 is a diagram illustrating a control method for a SAR satellite power system according to a second example of the present invention. FIG. 6 illustrates an operation process in which a high-voltage battery (13) supplies power to both a high-voltage system and a low-voltage system in a situation where power is not supplied from a solar cell array (11), such as during an eclipse period, similar to FIG. 5.

[0048] Referring to FIG. 6, in the control method according to the second example of the present invention, a high-voltage battery (13) supplies power to both systems, including a high-voltage system and a low-voltage system, during an eclipse. First, the output of the high-voltage battery (13) is supplied to a high-power load (17) through the first converter (power conversion unit) and switch (161) of the PCDU (16). Through this, the high-voltage system can stably supply high power required for the operation of high-power equipment, such as a SAR radar transmitter, just as it normally does. In addition, the output of the high-voltage battery (13) is also supplied to the low-voltage system. To this end, the power output from the high-voltage battery (13) is supplied to a second charger (14). The second charger (14) converts the input power into voltage and current conditions suitable for charging the low-voltage battery (15). The low-voltage battery (15) receives the converted power from the second charger (14) and charges it. And the power from the charged low-voltage battery (15) is stably supplied to the low-power load (18) again through the second converter and switch (162) of the PCDU (16).

[0049] In this way, in the control method according to the second example of the present invention, the high-voltage battery (13) functions as a common power source that simultaneously supports a high-power load (17) and a low-power load (18). Accordingly, both the high-voltage system and the low-voltage system can be operated continuously even when the power supply from the solar cell array (11) is cut off, such as during a solar eclipse. Therefore, power interruption on the low-voltage load side can be effectively prevented, and this can contribute to significantly improving the reliability of the entire satellite power system even under extreme conditions such as a solar eclipse.

[0050] FIG. 7 is a diagram illustrating a control method for a SAR satellite power system according to the third example of the present invention. FIG. 7 describes the operation process of supplying power from a low-voltage battery (15) to a low-power load (18) when the charge of the low-voltage battery (15) is sufficient in a situation where power is not supplied from a solar cell array (11), such as during an eclipse.

[0051] Referring to FIG. 7, in the control method according to the third example of the present invention, the output of the low-voltage battery (15) is controlled to be directly supplied to the low-power load (18) through the second converter and switch (162) of the PCDU (16). At this time, the high-voltage battery (13) does not participate in the operation of the low-voltage system. This means that, as in FIG. 5 and FIG. 6, there is no need to use the high-voltage battery (13) as an auxiliary power source for the low-voltage system, and the power system of the SAR satellite can maintain the operation of the low-power load (18) using only the low-voltage battery (15). In FIG. 7, the path of the first converter and switch (161) and the high-voltage battery (13) is not used, which means that the power required by the low-power load is sufficiently satisfied by the low-voltage battery (15) alone.

[0052] Accordingly, the control method according to the third example of the present invention is one of various modes corresponding to a power shortage situation during an eclipse period, and when the charge state of the low-voltage battery (15) is good, the low-voltage system is operated independently to minimize the consumption of the high-voltage battery (13). Through this, the high-voltage battery (13) can conserve power in preparation for necessary situations (e.g., the situation of FIGS. 5 and FIGS. 6), thereby further improving efficiency and operational stability.

[0053] FIG. 8 is a diagram illustrating a control method for a SAR satellite power system according to the fourth example of the present invention. FIG. 8 describes an operation process in which a high-voltage battery (13) and a low-voltage battery (15) each independently supply power to their corresponding loads (17, 18) while the power supply of the solar cell array (11) is completely cut off, such as during an eclipse.

[0054] Referring to FIG. 8, in the control method according to the fourth example of the present invention, when the charge state of both the high-voltage battery (13) and the low-voltage battery (15) is stable, each voltage system independently supports its own load. As shown in FIG. 8, the output of the high-voltage battery (13) is supplied to a high-power load (17) through the first converter and switch (161) of the PCDU (16). The high-voltage system utilizes the high-voltage battery (13) as a single power source to satisfy the power requirements of high-power loads, such as SAR radar transmitters, and this is the same as the normal operation method. Meanwhile, in the low-voltage system, when the charge amount of the low-voltage battery (15) is sufficient, as shown in FIG. 8, the output of the low-voltage battery (15) is directly supplied to a low-power load (18) through the second converter and switch (162) of the PCDU (16). In this case, the low-voltage battery (15) independently maintains the operation of low-power equipment, and the high-voltage battery (13) does not participate in supplying power to the low-voltage system.

[0055] Accordingly, in the control method according to the fourth example of the present invention, the high-voltage battery (13) and the low-voltage battery (15) each serve as independent power systems and can individually drive the loads corresponding to themselves. Unlike the auxiliary power mode or backup charging mode described in FIGS. 5 and 6, this corresponds to a normal independent operation mode where mutual assistance is not required because the charge state of both batteries is good. This method of operation can provide the advantage of efficiently managing the power of each power system, preventing unnecessary power flow and loss, while stably operating the high-power load (17) and the low-power load (18) without mutual interference. In particular, even in situations where external power is cut off, such as during a solar eclipse, the two power systems can independently maintain their respective loads, which is advantageous for ensuring the stability and reliability of the system.

[0056] FIG. 9 is a drawing illustrating a control method for a SAR satellite power system according to the fifth example of the present invention. FIG. 9 describes a normal operation in which, in a photovoltaic power generation section where sufficient power is generated from a solar cell array (11), a high-voltage battery (13) and a low-voltage battery (15) are simultaneously charged and power is supplied to loads (17, 18) of each voltage system.

[0057] Referring to FIG. 9, in the control method according to the fifth example of the present invention, since the solar cell array (11) can sufficiently supply power in the section where solar power generation is possible, the first and second chargers (12, 14) perform normal charging operations. The output power of the solar cell array (11) is input to the first charger (12), and the first charger (12) converts it into a voltage and current suitable for charging the high-voltage battery (13) and supplies it to the high-voltage battery (13). In addition, a portion of the output of the first charger (12) is supplied to the second charger (14), and the second charger (14) converts it into power suitable for charging the low-voltage battery (15) and supplies it to the low-voltage battery (15). The output of the high-voltage battery (13) charged in this way is stably supplied to the high-power load (17) through the first converter and switch (161) of the PCDU (16). In addition, the power from the low-voltage battery (15) charged through the second charger (14) is also supplied to the low-power load (18) through the second converter and switch (162) of the PCDU (16). This control method enables both the high-voltage and low-voltage systems to operate independently and efficiently in the photovoltaic power generation section.

[0058] Thus, the control method according to the fifth example of the present invention provides a normal operating state in which power from the solar cell array (11) can charge and supply the entire system. In this section, power generated from the solar cell array (11) is used to charge the high-voltage battery (13) and the low-voltage battery (15), and stable power is supplied to the high-power load (17) and the low-power load (18). At this time, since the path between the high-voltage system and the low-voltage system is maintained independently, each load (17, 18) can be operated normally without mutual interference. That is, in the section where solar power generation is possible, both the high-voltage battery (13) and the low-voltage battery (15) can be charged, and the high-power load (17) and the low-power load (18) can be driven stably at the same time.

[0059] FIG. 10 is a diagram illustrating a control method for a SAR satellite power system according to the 6th example of the present invention. FIG. 10 illustrates a process of power supply under conditions where power generation is possible for a solar cell array (11), but the high-power load (17) is turned off (inactive) and only the low-voltage system load (18) is operated (active).

[0060] Referring to FIG. 10, power generated from a solar cell array (11) is first supplied to a first charger (12). The first charger (12) converts the input power into voltage and current conditions suitable for charging a high-voltage battery (13) and supplies it to the high-voltage battery (13) for charging. Normally, the first charger (12) and the high-voltage battery (13) can supply power to a high-power load (17) through the first converter and switch (161) of the PCDU (16), but in the situation of FIG. 10, since the high-power load (17) is in an inactive state, power supply to the high-voltage system is cut off. That is, the first converter and switch (161) cut off the power supplied from the first charger (12) to the high-power load (17). Meanwhile, the remaining power from the output of the first charger (12) is distributed to a second charger (14). The second charger (14) converts the power supplied from the first charger (12) into a voltage and current suitable for charging the low-voltage battery (15) and charges the low-voltage battery (15). The power of the low-voltage battery (15) thus charged is supplied to a low-power load (18) through the second converter and switch (162) of the PCDU (16) to drive the low-power load (18).

[0061] Accordingly, the power flow in FIG. 10 is carried out in the order of a solar cell array (11), a first charger (12), a second charger (14), a low-voltage battery (15), a PCDU (16), and a low-power load (18), and the power path to the high-power load (17) is blocked. This is a control method for concentrating power obtained from solar energy on the low-voltage system. Such operating conditions are particularly useful during stages when high-power missions, such as SAR radar transmission, are not performed, for example, in the satellite's standby mode or during low-power mission stages where only communication and measurement equipment are operated. By preventing unnecessary power conversion losses in the high-power system and concentrating the obtained solar energy on charging the low-voltage battery (15) and operating the low-power load, power management efficiency can be maximized.

[0062] FIG. 11 is a diagram illustrating a control method for a SAR satellite power system according to the seventh example of the present invention. FIG. 11 is based on the premise that the solar cell array (11) is generating power normally and both the high-power load (17) and the low-power load (18) are in operation. However, it is distinguished from FIG. 9 and FIG. 10 in that the low-voltage system does not receive solar power and drives the low-power load (18) using power stored in the low-voltage battery (15).

[0063] Referring to FIG. 11, power supplied from the solar cell array (11) is supplied to the first charger (12) and converted to voltage and current conditions suitable for charging the high-voltage battery (13). The output of the high-voltage battery (13) thus charged is delivered to the high-power load (17) through the first converter and switch (161) of the PCDU (16), and the high-power load (17) is driven by receiving stable power from both the solar power and the high-voltage battery (13). Meanwhile, in the low-voltage system, the second charger (14) is deactivated or operates only in a limited manner, or the charge of the low-voltage battery (15) is sufficient so that additional charging is not required. Under these conditions, the low-voltage battery (15) uses the stored power to directly drive the low-power load (18), and the power is converted to the required low-voltage level through the second converter and switch (162) of the PCDU (16) and then stably distributed to each low-power load.

[0064] Accordingly, the power flow in FIG. 11 is configured such that the high-voltage system drives a high-power load (17) based on solar power generation and a high-voltage battery (13), while the low-voltage system maintains a low-power load (18) solely through a low-voltage battery (15). This configuration is effectively applied under operating conditions where the charge state of the low-voltage battery (15) is sufficient and the power requirement of the low-power load (18) is not high. Additionally, since the primary targets for solar power supply are concentrated on the high-power load (17) and the high-voltage battery (13), there is an advantage in that the power quality and stability required for performing high-power missions, such as driving a SAR radar antenna, are secured. Consequently, the control method according to FIG. 11 enables the high-voltage system and the low-voltage system to operate separately under operating conditions where solar power generation is possible, thereby allowing both systems to stably support each load without interfering with one another. Through this, the overall energy flow of the power system is optimized, and operational efficiency and reliability can be improved in a SAR satellite environment where high-power and low-power loads are mixed.

[0065] FIG. 12 is a schematic diagram showing a SAR satellite power system according to Variant Example 1 of the present invention.

[0066] Referring to FIG. 12, in Variation 1 of the present invention, first and second solar cell arrays (21, 22) are respectively provided so that two voltage systems can be operated in a completely independent structure. Power generated from the first solar cell array (21) is supplied to the first charger (23), and the first charger (23) converts it to voltage and current conditions required for charging the high-voltage battery (25) and charges the high-voltage battery (25). The output of the charged high-voltage battery (25) is supplied to a high-power load (28) through the PCDU (27). On the other hand, the output of the second solar cell array (22) is supplied to the second charger (24), and the second charger (24) converts the input power to a level suitable for charging the low-voltage battery (26) and charges the low-voltage battery (26). The output of the low-voltage battery (26) is supplied to a low-power load (29) through the PCDU (27). That is, unlike the embodiment shown in FIG. 4, the high-voltage battery (25) and the low-voltage battery (26) do not share the same primary charging path, but are charged independently through separate charging paths from the first and second solar cell arrays (21, 22), respectively. As a result, the high-voltage battery (25) and the low-voltage battery (26) are not electrically affected by each other, and power supply to the high-power load (28) and the low-power load (29) can be maintained completely independently for each voltage system. This configuration provides the advantage of minimizing interference between the two voltage systems and efficiently distributing solar resources according to the power conditions required by each system. In addition, the stability and reliability of the entire satellite power system can be increased by structurally blocking instantaneous power fluctuations occurring in the high-power system from being transmitted to the low-voltage system.

[0067] FIG. 13 is a schematic diagram showing a SAR satellite power system according to Variant Example 2 of the present invention, which adopts a dual PCDU structure unlike the embodiment shown in FIG. 4.

[0068] Referring to FIG. 13, the SAR satellite power system according to Variant 2 of the present invention is structurally different from the embodiment of FIG. 4 or Variant 1 of FIG. 12 in that it implements a fully separated dual power architecture in which the two voltage systems do not share a single PCDU but each have a dedicated PCDU. That is, the power flow leading to the solar cell array (31), the first charger (32), the high-voltage battery (33), the second charger (34), and the low-voltage battery (35) follows the same configuration as the embodiment of FIG. 4. However, in Variant 2, there is a difference in that the high-voltage system and the low-voltage system each undergo power conversion and distribution individually through the high-voltage dedicated first PCDU (36) and the low-voltage dedicated second PCDU (37), which are independent power distribution devices.

[0069] In the high-voltage system, the output of the first charger (32) or the high-voltage battery (33) is supplied to the first PCDU (36) dedicated to the high-voltage system. The first PCDU (36) can be designed with a structure that strengthens electrical isolation between systems to stably distribute the high voltage required for high-power loads (38), such as SAR radar transmitters, and particularly to prevent voltage fluctuations or electronic noise that may occur during high-power pulse load operation from propagating to other systems. On the other hand, the low-voltage system follows a separate, independent flow. Power branched from the output of the first charger (32) is supplied to the second charger (34), converted into a voltage and current suitable for charging the low-voltage battery (35), and charged. The output of the charged low-voltage battery (35) is supplied to the second PCDU (37) dedicated to the low-voltage system. The second PCDU (37) stably distributes the voltage by adjusting it to suit low-power loads (38), such as sensors, computers, and communication devices. In addition, this second PCDU (37) is also configured as a circuit completely independent of the high-voltage system, so power quality can be ensured so that power ripple or high-power pulses generated during high-voltage load operation do not affect low-power equipment.

[0070] FIG. 14 is a schematic diagram showing a SAR satellite power system according to Variant Example 3 of the present invention.

[0071] Referring to FIG. 14, the SAR satellite power system according to Variant Example 3 of the present invention is characterized by a structure in which the high-voltage system and the low-voltage system are operated completely separately, and each voltage system receives power through a different solar cell array and DC-DC converter.

[0072] The high-voltage system is configured independently through the first solar cell array (41) and the first DC-DC converter (43). Power supplied from the first solar cell array (41) is converted into a voltage and current suitable for charging the high-voltage battery (45) by the first DC-DC converter (43) and then charged into the high-voltage battery (45). Subsequently, the output of the high-voltage battery (45) is supplied to the first PCDU (47), and the second PCDU (47) stably distributes the high voltage required for the high-power load (49). Looking at the low-voltage system, power output from the second solar cell array (42) is input into the second DC-DC converter (44). The second DC-DC converter (44) converts the solar cell output into voltage and current conditions suitable for charging the low-voltage battery (46), and the converted power is charged into the low-voltage battery (46). Afterwards, the output of the low-voltage battery (46) is supplied to the second PCDU (48), and the second PCDU (48) converts and distributes the voltage to a voltage suitable for low-power loads (50), such as sensors, computers, and communication devices.

[0073] The power system of the SAR satellite presented in the present invention has been described based on the embodiments and variations shown in FIGS. 2 and FIGS. 12 to 14, but this is merely a representative configuration to aid understanding, and the actual implementation can be expanded in various forms. For example, the PCDU, which performs power conversion and distribution, may be referred to by various names such as Power Conditioning and Distribution Unit, Power Supply Unit (PSU), Power Conditioning System (PCS), and Power Conversion System (PCS) depending on the design or manufacturing environment, and is not limited to these specific names. Furthermore, while the embodiment shown in FIG. 4 illustrates a form in which power is supplied from a single solar cell array to high-voltage and low-voltage systems, in actual application, it is possible to configure separate solar cell arrays corresponding to each voltage system as in Variation Examples 1 and 3, or to use multiple arrays in parallel to optimize power generation conditions.

[0074] The PCDU can also be composed of a single unit or multiple units, and may adopt a form that is completely separated by system (e.g., a redundant configuration of a high-voltage PCDU and a low-voltage PCDU) or a distributed structure modularized by load group, as shown in Variants 2 and 3. Furthermore, although the interior of the PCDU is depicted as an integrated block as in FIG. 4, the actual hardware configuration can be divided into smaller units, such as a converter module responsible for voltage conversion and a switch array module that controls the power path between the battery and the load. Although the load is also simplified in the drawing as load groups by voltage system, the actual load groups can be subdivided into various components such as sensors, electronic equipment, and communication equipment that require various input voltage levels (e.g., 5V, 12V, 24V, etc.), and some equipment operates by directly receiving the battery voltage. These loads can be classified and operated into high-voltage battery-based load groups and low-voltage battery-based load groups depending on the required power characteristics.

[0075] Meanwhile, the terms 'high-voltage battery' and 'low-voltage battery' in this specification do not imply a distinction based solely on voltage levels. Batteries may be classified according to the discharge characteristics required by a specific load (e.g., a load requiring a high discharge rate or a load requiring a relatively low discharge rate), and accordingly, power systems can be implemented in various ways with a structure combining two or more types of batteries. Therefore, the present invention lies not in voltage levels, but in battery combinations and multi-system-based power architectures optimized for load characteristics and mission operating conditions. Furthermore, for convenience of explanation, this specification has focused on two batteries (high-voltage and low-voltage); however, in actual systems, it can be expanded to a multi-battery structure including three or more batteries, and configurations combining multiple PCDUs or multiple solar cell arrays can also be applied using the same principle. In addition, the power flow control modes described through the drawings above (e.g., photovoltaic power generation section, solar eclipse section, high-power load active state, low-power centered operation state, etc.) are merely representative examples. In actual operation, there may be many more power flow scenarios depending on various variables such as solar power generation status, load mission cycle, battery charge status, thermal or operational constraints, and all such combinations and control methods are included within the scope of the present invention.

[0076] In the foregoing, preferred embodiments of the present invention have been described and illustrated using specific terms, but such terms are intended solely to clarify the invention, and it is obvious that various modifications and changes may be made to the embodiments and terms described without departing from the technical spirit and scope of the following claims. Such modified embodiments should not be understood separately from the spirit and scope of the present invention, but should be considered to fall within the scope of the claims of the present invention. Explanation of the symbols

[0077] 1, 11, 31: Solar cell array 2 : Charger 3 : Battery 4, 5: Power conversion unit 6, 7 : Subordinate 12, 23, 32: First charger 13, 25, 33: High-voltage battery 14, 24, 34: 2nd charger 15, 26, 35: Low voltage battery 16, 27 : PCDU 17, 28, 38, 45, 49: High-power loads 18, 29, 39, 46, 50: Low-power load 21, 41: First solar cell array 22, 42: Second solar cell array 43: 1st DC-DC Converter 44: 2nd DC-DC Converter 47 : 1st PCDU 48 : 2nd PCDU

Claims

Claim 1 A SAR satellite power system comprising: a first charger that converts power supplied from a solar cell array into power of a first voltage level; a first battery that stores power of a first voltage level supplied from the first charger; a second charger that converts power of a first voltage level supplied from either the first charger or the first battery into power of a second voltage level; a second battery that stores power of a second voltage level supplied from the second charger; and a power conversion and distribution unit that converts power of a first voltage level supplied from either the first charger or the first battery into a driving voltage of a first load group and supplies it, and converts power of a second voltage level supplied from either the second charger or the second battery into a driving voltage of a second load group and supplies it. Claim 2 A SAR satellite power system comprising: a first charger that converts power supplied from a first solar cell array into power of a first voltage level; a first battery that stores power of a first voltage level supplied from the first charger; a second charger that converts power supplied from a second solar cell array into power of a second voltage level; a second battery that stores power of a second voltage level supplied from the second charger; and a power conversion and distribution unit that converts power of a first voltage level supplied from either the first charger or the first battery into a driving voltage of a first load group and supplies it, and converts power of a second voltage level supplied from either the second charger or the second battery into a driving voltage of a second load group and supplies it. Claim 3 A SAR satellite power system comprising: a first charger that converts power supplied from a solar cell array into power of a first voltage level; a first battery that stores power of a first voltage level supplied from the first charger; a second charger that converts power of a first voltage level supplied from either the first charger or the first battery into power of a second voltage level; a second battery that stores power of a second voltage level supplied from the second charger; a first power conversion and distribution unit that converts power of a first voltage level supplied from either the first charger or the first battery into a driving voltage of a first load group and supplies it; and a second power conversion and distribution unit that converts power of a second voltage level supplied from either the second charger or the second battery into a driving voltage of a second load group and supplies it. Claim 4 A SAR satellite power system comprising: a first DC-DC converter that converts power supplied from a first solar cell array into power of a first voltage level; a first battery that stores power of a first voltage level supplied from the first DC-DC converter; a second DC-DC converter that converts power supplied from a second solar cell array into power of a second voltage level; a second battery that stores power of a second voltage level supplied from the second DC-DC converter; a first power conversion and distribution unit that converts power of a first voltage level supplied from either the first DC-DC converter or the first battery into a driving voltage of a first load group and supplies it; and a second power conversion and distribution unit that converts power of a second voltage level supplied from either the second DC-DC converter or the second battery into a driving voltage of a second load group and supplies it. Claim 5 A SAR satellite power system according to any one of claims 1 to 4, wherein the power of the second voltage level is a power of a voltage level lower than the power of the first voltage level. Claim 6 A SAR satellite power system according to any one of claims 1 to 4, wherein the first battery has a higher discharge rate than the second battery. Claim 7 A SAR satellite power system according to any one of claims 1 to 4, wherein the first load group includes a load requiring a higher discharge rate than the second load group, and the second load group includes a load requiring a lower discharge rate than the first load group. Claim 8 A method for controlling a SAR satellite power system according to claim 1, comprising: a process of supplying power of a first voltage level charged in a first battery to a second charger; a process of converting power of a first voltage level supplied from the first battery through the second charger into power of a second voltage level to charge the second battery; and a process of converting power of a second voltage level supplied from at least one of the second charger or the second battery into a driving voltage of a second load group through the power conversion and distribution unit and supplying it to the second load group. Claim 9 A method for controlling a SAR satellite power system according to claim 1, comprising: a process of supplying power of a first voltage level charged in a first battery to a second charger; a process of converting power of a first voltage level supplied from the first battery into power of a second voltage level through the second charger to charge the second battery; and a process of converting power of a first voltage level supplied from the first battery into a driving voltage of the first load group and supplying it through the power conversion and distribution unit, and converting power of a second voltage level supplied from either the second charger or the second battery into a driving voltage of the second load group and supplying it to the second load group. Claim 10 A method for controlling a SAR satellite power system according to claim 1, comprising: a process of supplying power of a second voltage level charged in a second battery; and a process of converting power of a second voltage level supplied from the second battery into a driving voltage of a second load group through a power conversion and distribution unit and supplying it to the second load group. Claim 11 A method for controlling a SAR satellite power system according to claim 1, comprising: a process of supplying power of a first voltage level charged in a first battery; a process of supplying power of a second voltage level charged in a second battery; and, through the power conversion and distribution unit, converting power of a first voltage level supplied from the first battery into a driving voltage of a first load group and supplying it, and converting power of a second voltage level supplied from the second battery into a driving voltage of a second load group and supplying it to the second load group; a method for controlling a SAR satellite power system. Claim 12 A method for controlling a SAR satellite power system according to claim 1, comprising: a process of converting power supplied from a solar cell array into power of a first voltage level through a first charger; a process of storing power of a first voltage level supplied from the first charger in a first battery; a process of converting power of a first voltage level supplied from either the first charger or the first battery into power of a second voltage level through a second charger; a process of storing power of a second voltage level supplied from the second charger in the second battery; and a process of converting power of a first voltage level supplied from either the first charger or the first battery into a driving voltage of the first load group and supplying it, or converting power of a second voltage level supplied from either the second charger or the second battery into a driving voltage of the second load group and supplying it through the power conversion and distribution unit.

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