Electric power system, energy storage system, and operation method

Abstract

An electric power system, an energy storage system, and an operation method. The energy storage system is coupled to a mains supply of the electric power system by means of a power supply bus, and the electric power system comprises a plurality of uninterruptible power supplies coupled to the power supply bus. The energy storage system comprises a power adjustment device, a battery module, a direct-current conversion device, and a first controller; and the direct-current conversion device is correspondingly coupled to a plurality of direct-current buses of the uninterruptible power supplies by means of a plurality of external lines. The first controller controls the power adjustment device to convert alternating-current power on the power supply bus into first direct-current power so as to charge the battery module. When the mains supply fails, the first controller controls the direct-current conversion device to convert the first direct-current power into second direct-current power, and supply the second direct-current power to the direct-current buses respectively by means of the external lines.

Description

Power system, energy storage system and method of operating the same TECHNICAL FIELD

[0001] The present disclosure relates to a power system, an energy storage system and a method of operating the same, in particular to a power system, an energy storage system and a method of operating the same sharing batteries of the energy storage system. BACKGROUND

[0002] With the increase of population and economic development, the global energy demand continues to grow, which puts higher requirements on the energy supply system. Energy storage systems can store excess renewable energy and release it when needed. For users, energy storage is also used to regulate electricity consumption and regulate power to overcome power pressure and electricity consumption regulation and control strategies to save electricity bills.

[0003] When the client's mains power is interrupted or abnormal, the energy storage system can effectively provide the required power for the power grid to maintain power stability, and the key loads in the system are usually equipped with uninterruptible power supply systems (UPS) to avoid the impact of power grid emergencies on equipment and loads. Specifically, the current user power system architecture is shown in FIG. 1. The energy storage system 300 is connected to the power bus AC_Bus to regulate the charging and discharging of the battery module 2 to stabilize the alternating current power Pac on the power bus AC_Bus. On the other hand, the uninterruptible power supply system UPS_S includes a cabinet 400 and a plurality of uninterruptible power supply devices UPS_1-UPS_n, and the cabinet 400 includes accommodation spaces C1-Cn for accommodating the uninterruptible power supply devices UPS_1-UPS_n respectively. Moreover, the accommodation spaces C1-Cn further include battery cabinets Cb_1-Cb_n, and the battery cabinets Cb_1-Cb_n accommodate the batteries B1-Bn of the uninterruptible power supply devices UPS_1-UPS_n respectively.

[0004] When the mains 200 is operating normally, the user's key loads Lc_1-Lc_n are connected by the uninterruptible power supply system UPS_S. Once the mains 200 is interrupted or abnormal, the power of the batteries B1-Bn of the uninterruptible power supply devices UPS_1-UPS_n is converted to provide power for the key loads Lc_1-Lc_n to use electricity. Moreover, once the mains 200 is interrupted or abnormal, the energy storage system 300 provides alternating current power Pac to the power bus AC_Bus through the discharge of the battery module 2 to power the non-critical loads Ln.

[0005] In the existing architecture of FIG. 1, there are two battery systems (i.e., battery modules 2 and batteries B1-Bn) operating independently for the overall client power supply, in the energy storage system 300 and the uninterruptible power supply system UPS_S, respectively, and both are used to maintain power on different paths. The energy storage system 300 mainly adjusts and maintains the AC power Pac on the supply bus AC_Bus through the charging and discharging of the battery modules 2. Conversely, the uninterruptible power supply system UPS_S mainly adjusts and maintains the output power Po_1-Po_n for the power supply of the critical loads Lc_1-Lc_n through the charging and discharging of the batteries B1-Bn. However, the battery systems (i.e., battery modules 2 and batteries B1-Bn) are costly and need to be replaced regularly, resulting in relatively high equipment and operation and maintenance costs for the existing system.

[0006] Therefore, how to design a power system, an energy storage system and an operating method thereof, so that the energy storage system and the uninterruptible power supply system can share the battery modules as a supporting shared resource, is a major issue that the inventors of the present disclosure want to study.

[0007] It is worth mentioning that the background described in FIG. 1 is generally used to represent the prior art of the present disclosure and the relationship before and after the present disclosure. As for the inventor's work described in the background part of FIG. 1, it should not be expressed or implied as a prior art that contradicts the present disclosure, nor is it suitable as prior art at the time of filing.

[0008] SUMMARY

[0009] To solve the above problems, the present disclosure provides an energy storage system to overcome the problems of the prior art. Therefore, the energy storage system of the present disclosure is coupled to the power grid of the power system through the supply bus, and the power system includes a plurality of uninterruptible power supply devices coupled to the supply bus. The energy storage system includes a power regulating device, a battery module, a DC conversion device, and a first controller, and the power regulating device is coupled to the supply bus and the battery module. One end of the DC conversion device is coupled to the battery module, and the other end is coupled to a plurality of DC buses of the uninterruptible power supply devices through a plurality of external lines. The first controller is coupled to the power regulating device and the DC conversion device, and when the power grid is operating normally, the first controller controls the power regulating device to convert the AC power on the supply bus into a first DC power to charge the battery module. When the power grid fails, the first controller controls the DC conversion device to convert the first DC power into a second DC power, and the second DC power is provided to the DC buses through the external lines, respectively.

[0010] To solve the above problems, the present disclosure provides a power system to overcome the problems of the prior art. Therefore, the power system of the present disclosure is coupled to a commercial power supply, and the power system includes a power supply bus, a plurality of uninterruptible power supply devices, and an energy storage system, and the power supply bus receives alternating current power from the commercial power supply. The uninterruptible power supply devices are coupled to the power supply bus, and can be coupled to a plurality of critical loads to supply power to the critical loads by converting the alternating current power into a plurality of output powers accordingly. The energy storage system is coupled to the power supply bus and the uninterruptible power supply devices, and the energy storage system includes a power conditioning device, a battery module, a direct current conversion device, and a first controller. The power conditioning device is coupled to the power supply bus, and the battery module is coupled to the power conditioning device. One end of the direct current conversion device is coupled to the battery module, and the other end is coupled to a plurality of direct current buses of the uninterruptible power supply devices through a plurality of external lines accordingly. The first controller is coupled to the power conditioning device and the direct current conversion device, and when the commercial power supply is normally operating, the first controller controls the power conditioning device to convert the alternating current power into a first direct current power to charge the battery module. When the commercial power supply fails, the first controller controls the direct current conversion device to convert the first direct current power into a second direct current power, and the second direct current power is provided to the direct current buses through the external lines respectively, and the uninterruptible power supply devices provide a plurality of output powers according to the second direct current power accordingly.

[0011] To solve the above problems, the present disclosure provides an operating method of an energy storage system to overcome the problems of the prior art. Therefore, the energy storage system of the present disclosure is coupled to a commercial power supply of a power system through a power supply bus, and the power system includes a plurality of uninterruptible power supply devices coupled to the power supply bus. The operating method of the energy storage system includes the following steps: (a) detecting whether the commercial power supply fails; (b) controlling a direct current conversion device to convert a first direct current power provided by a battery module into a second direct current power to provide the second direct current power to direct current buses of the uninterruptible power supply devices through a plurality of external lines according to the commercial power supply failing; (c) determining whether the commercial power supply failing belongs to a commercial power supply interruption condition or a commercial power supply abnormal condition; (d) controlling a power conditioning device to convert the first direct current power into alternating current power to provide the alternating current power to the power supply bus according to the commercial power supply failing belonging to the commercial power supply interruption condition; and (e) controlling the power conditioning device to convert the first direct current power into a first compensation power to provide the first compensation power to the power supply bus to compensate for alternating current power provided by the commercial power supply according to the commercial power supply failing belonging to the commercial power supply abnormal condition.

[0012] The main purpose and effect of the present disclosure is to use a shared battery module as a shared resource to support an energy storage system and an uninterruptible power supply system. This is mainly achieved by coupling one end of a direct current conversion device to a battery module, and coupling the other end of the direct current conversion device to an external uninterruptible power supply system through external lines. In this way, the first controller can effectively regulate the first direct current power of the battery module, and the efficiency of the energy storage system can be improved and the electricity bill can be greatly reduced by switching the uninterruptible power supply system, thereby effectively reducing equipment problems and battery maintenance costs.

[0013] For further understanding of the technology, means, and effects of the present disclosure taken to achieve the intended purpose, please refer to the following detailed description of the present disclosure and the accompanying drawings. It is believed that the purpose, features, and characteristics of the present disclosure can be understood in depth and specifically from the above, however, the accompanying drawings are provided for reference and illustration only, and are not intended to limit the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0014] FIG. 1 is a circuit block diagram of a power system of the prior art;

[0015] FIG. 2 is a circuit block diagram of a power system of the present disclosure;

[0016] FIG. 3A is a detailed circuit block diagram of a first embodiment of the power system of the present disclosure;

[0017] FIG. 3B is a detailed circuit block diagram of a second embodiment of the power system of the present disclosure;

[0018] FIG. 4 is a schematic diagram of external line wiring of the present disclosure; and

[0019] FIG. 5 is a flowchart of an operating method of the energy storage system of the present disclosure.

[0020] BRIEF DESCRIPTION OF DRAWINGS 100: power system AC_Bus: power supply bus Br: breaker UPS_S: uninterruptible power supply system UPS_1 ~ UPS_n: uninterruptible power supply device DC_Bus_1 ~ DC_Bus_n: DC bus B1 ~ Bn: battery 20: AC / DC conversion device 22: DC / AC conversion device 24: second controller SW: bypass switch 200: commercial power 300: energy storage system 1: power conditioning device 2: battery module 26: battery 3: DC conversion device 4: first controller Te_1 ~ Te_n: external line L1: power line L2: communication line D1 ~ Dn: unidirectional conduction component 400: cabinet C1 ~ Cn: housing space Cb_1 ~ Cb_n: battery cabinet Pac: AC power Lc_1 ~ Lc_n: critical load Po_1 ~ Po_n: output power Pdc1: first DC power Pdc2: second DC power Pc1: first compensation power Pc2: second compensation power DETAILED DESCRIPTION

[0021] The technical content and detailed description of the present disclosure are described as follows in conjunction with the accompanying drawings:

[0022] Please refer to FIG. 2 for a circuit block diagram of the power system. The power system 100 is coupled with a utility 200 to receive an AC power Pac provided by the utility 200. The power system 100 includes a power bus AC_Bus, a plurality of uninterruptible power supplies UPS_1-UPS_n and an energy storage system 300, and the power bus AC_Bus receives the AC power Pac from the utility 200. The uninterruptible power supplies UPS_1-UPS_n are coupled with the power bus AC_Bus, and the uninterruptible power supplies UPS_1-UPS_n can be coupled with a plurality of critical loads Lc_1-Lc_n to correspondingly convert the AC power Pac into a plurality of output powers Po_1-Po_n to power the critical loads Lc_1-Lc_n. That is, the number of the uninterruptible power supplies UPS_1-UPS_n can be greater than or equal to the number of the critical loads Lc_1-Lc_n. Also, the "correspondingly" can mean that when an output terminal of the uninterruptible power supply UPS_1-UPS_n is coupled with a critical load Lc_1-Lc_n (assuming the uninterruptible power supply UPS_1), the uninterruptible power supply UPS_1 coupled with the critical load Lc_1 can convert the AC power Pac into the output power Po_1 to provide the output power Po_1 to the critical load Lc_1. Under this condition, if the uninterruptible power supplies UPS_n-1-UPS_n are not coupled with the critical loads Lc_n-1-Lc_n, the uninterruptible power supplies UPS_n-1-UPS_n can not provide the output powers Po_n-1-Po_n, and so on.

[0023] The energy storage system 300 is coupled with the power bus AC_Bus and each of the uninterruptible power supplies UPS_1-UPS_n, and the energy storage system 300 includes a power conditioning system 1, a battery module 2, a DC conversion device 3 and a first controller 4. The power conditioning system 1 is coupled with the power bus AC_Bus, and the battery module 2 is coupled with the power conditioning system 1. One end of the DC conversion device 3 is coupled with the battery module 2 and the power conditioning system 1, and the other end of the DC conversion device 3 is correspondingly coupled with a plurality of DC buses DC_Bus_1-DC_Bus_n of the uninterruptible power supplies UPS_1-UPS_n through a plurality of external lines Te_1-T_e_n. That is, each of the uninterruptible power supplies UPS_1-UPS_n has one of the DC buses DC_Bus_1-DC_Bus_n, and the DC conversion device 3 is correspondingly coupled with each of the DC buses DC_Bus_1-DC_Bus_n through each of the external lines Te_1-T_e_n.

[0024] The first controller 4 is coupled with the power conditioning device 1 and the DC conversion device 3 to control the power conversion of the battery module 2. Specifically, the first controller 4 can control the power conditioning device 1 to convert the AC power Pac into the first DC power Pdcl for charging the battery module 2 via the first DC power Pdcl. The first controller 4 can also control the DC conversion device 3 to convert the first DC power Pdcl into the second DC power Pdc2 for providing the second DC power Pdc2 to each of the DC buses DC_Bus_1 ~ DC_Bus_n via the external lines Te_1 ~ Te_n. It is worth mentioning that in an embodiment, the term "power" as mentioned in the present disclosure can refer to voltage, current or power, and if not specifically mentioned, it mainly refers to power, and the relationship between voltage and current can be derived from the "power" and basic electrical principles, which will not be described here.

[0025] Further, the uninterruptible devices UPS_1 ~ UPS_n can be regarded as an overall uninterruptible system UPS_S, and generally, the uninterruptible system UPS_S can be accommodated in the accommodation spaces C1 ~ Cn in the cabinet 400 to accommodate the uninterruptible devices UPS_1 ~ UPS_n. However, in the prior art, each accommodation space C1 ~ Cn must also include a battery cabinet Cb_1 ~ Cb_n to accommodate the batteries B1 ~ Bn (as shown in FIG. 1) for the power conversion of the uninterruptible devices UPS_1 ~ UPS_n. Therefore, the configuration space of the uninterruptible system UPS_S is large, and the configuration cost is relatively high.

[0026] In addition, in the prior art, the energy storage system 300 is mainly used for power regulation on the power supply bus AC_Bus. When there is AC power Pac on the power supply bus AC_Bus, the AC power Pac is used for energy storage, and when there is no AC power Pac on the power supply bus AC_Bus, the power supply bus AC_Bus is discharged. Therefore, in the entire power system 100, the energy storage system 300 is an independent system independent of the uninterruptible system UPS_S and is used for power regulation according to the condition of the power supply bus AC_Bus, and the internal power conversion operation is independent of the internal power conversion operation of the uninterruptible system UPS_S. That is, the energy storage system 300 in the prior art uses an independent cabinet to couple the power supply bus AC_Bus, and in addition to coupling the power supply bus AC_Bus, there is no power-related line coupling other systems.

[0027] Therefore, as in the above architecture, the overall client power consumption has two independently operating battery systems, one in the energy storage system 300 and the other in the uninterruptible power system UPS_S. However, due to the high cost of battery equipment and the need for regular replacement, the equipment and operation and maintenance costs are relatively high. Therefore, the main purpose and effect of the present disclosure is to provide a common battery-based shared battery that can be used in the energy storage system 300 and the uninterruptible power system UPS_S. In this architecture, the battery module 2 is designed as a shared resource of the energy storage system 300 and the uninterruptible power system UPS_S, and is charged and discharged according to the possible situation of the commercial power. In this way, not only the utilization efficiency of the battery module 2 can be improved, but also the equipment and operation and maintenance costs can be significantly reduced, achieving the goal of high efficiency and low cost.

[0028] Specifically, the present disclosure uses the shared battery module 2 as a shared resource to support the energy storage system 300 and the uninterruptible power system UPS_S. It mainly uses one end of the direct current conversion device 3 to couple the battery module 2, and the other end is coupled to the external uninterruptible power system UPS_S through external lines Te_1~Te_n. In this way, the first controller 4 can fully utilize the first direct current power Pdc1 of the battery module 2, and through the uninterruptible power switching of the uninterruptible power system UPS_S, the efficiency of the energy storage system 300 can be effectively improved, the electricity bill can be greatly reduced, and the equipment and battery operation and maintenance costs can be effectively reduced.

[0029] Therefore, as described above, the main feature of the present disclosure is that when the commercial power 200 fails, the first controller 4 can control the direct current conversion device 3 to convert the first direct current power Pdc1 into the second direct current power Pdc2, and provide the second direct current power Pdc2 to the direct current bus DC_Bus_1~DC_Bus_n of the uninterruptible power device UPS_1~UPS_n through the external lines Te_1~Te_n. The uninterruptible power device UPS_1~UPS_n then converts the second direct current power Pdc2 into output power Po_1~Po_n according to whether the backend is coupled to the critical load Lc_1~Lc_n to power the coupled critical load Lc_1~Lc_n. In this way, the uninterruptible power device UPS_1~UPS_n does not need to be additionally configured with a battery B1~Bn (as shown in FIG. 1), so that the entire uninterruptible power system UPS_S can save the space of the battery cabinet Cb_1~Cb_n, or the space of the battery cabinet Cb_1~Cb_n can be further used for other applications. In this way, the equipment and operation and maintenance costs can be significantly reduced, achieving the goal of high efficiency and low cost.

[0030] Further, the power system 100 can further include a non-critical load Ln, and the non-critical load Ln is coupled to the supply bus AC_Bus. Also, the power conditioning device 1 can be a bidirectional power converter with an isolation transformer (not shown). Thus, the power conditioning device 1 can bidirectionally convert the AC power Pac and the first DC power Pdcl to meet the power supply requirements of the power system 100. Also, the isolation transformer can electrically isolate the input and output of the power conditioning device 1 to isolate the power conditioning at the supply bus AC_Bus side from the power conditioning at the battery module 2 side to avoid affecting one side from the abnormality at the other side.

[0031] In another aspect, a circuit breaker Br is included between the supply bus AC_Bus and the utility 200, the uninterruptible power supplies UPS_l-UPS_n, and the energy storage system 300. The circuit breaker Br is mainly automatically operated to open or short circuit according to the voltage and current flowing therethrough, and can also be forced to open by, for example but not limited to, the first controller 4 or the uninterruptible power supplies UPS_l-UPS_n to temporarily shut down the circuit that does not need power supply to avoid additional power consumption.

[0032] Referring to FIG. 3A, which is a detailed circuit block diagram of the first embodiment of the power system of the present disclosure, in combination with FIG. 2. In FIG. 3A, each of the uninterruptible power supplies UPS_l-UPS_n includes an AC / DC conversion device 20, a DC / AC conversion device 22, and a second controller 24, and the AC / DC conversion device 20 is coupled to the supply bus AC_Bus. One end of the DC / AC conversion device 22 is coupled to the AC / DC conversion device 20 through the DC bus DC_Bus_l-DC_Bus_n to which it belongs, and when a critical load Lc_l- Lc_n (assuming the critical load Lc_l) is coupled to the uninterruptible power supply UPS_l-UPS_n (assuming the uninterruptible power supply UPS_l), the critical load Lc_l is coupled to the other end of the DC / AC conversion device 22 of the uninterruptible power supply UPS_l (i.e., the corresponding coupling relationship). The second controller 24 is coupled to the AC / DC conversion device 20 and the DC / AC conversion device 22 to control the power conversion of the AC / DC conversion device 20 and the DC / AC conversion device 22.

[0033] Further, the second controller 24 can control the AC / DC conversion device 20 to convert the AC power Pac into the second DC power Pdc2, and provide the second DC power Pdc2 to the DC / AC conversion device 22 through the DC bus DC_Bus_1 ~ DC_Bus_n. The second controller 24 can also control the DC / AC conversion device 22 to convert the second DC power Pdc2 into the output power Po_1 ~ Po_n to provide the output power Po_1 ~ Po_n to the critical load Lc_1 ~ Lc_n. Therefore, when the utility 200 is active (representing the AC power Pac is normal), the second controller 24 can control the AC / DC conversion device 20 to convert the AC power Pac into the second DC power Pdc2, and control the DC / AC conversion device 22 to convert the second DC power Pdc2 into the output power Po_1 ~ Po_n to provide the output power Po_1 ~ Po_n to the critical load Lc_1 ~ Lc_n.

[0034] On the contrary, when the utility 200 is inactive (representing the AC power Pac is abnormal), the second controller 24 can disable the AC / DC conversion device 20, and control the DC / AC conversion device 22 to convert the second DC power Pdc2 provided by the DC conversion device 3 into the output power Po_1 ~ Po_n to continuously power the critical load Lc_1 ~ Lc_n. In the prior art of FIG. 1, when the utility 200 is inactive, the second DC power Pdc2 is supplied by the battery B1 ~ Bn inside the UPS 1 ~ UPS_n, or the AC power Pac is first fed to the power bus AC_Bus by the energy storage system 300, and then the AC power Pac provided by the energy storage system 300 is converted by the UPS 1 ~ UPS_n.

[0035] Please refer to FIG. 3B for a detailed circuit block diagram of the second embodiment of the power system of the present disclosure, in combination with FIGS. 2-3A. The difference between FIG. 3B and FIG. 3A is that each of the uninterruptible power supply UPS_1-UPS_n further comprises a bypass switch SW. One end of the bypass switch SW is coupled to the AC / DC conversion device 20 and the power supply bus AC_Bus, and the other end of the bypass switch SW is coupled to the output end of the DC / AC conversion device 22. Moreover, when the commercial power 200 is valid (representing that the AC power Pac is normal), the second controller 24 can first control the AC / DC conversion device 20 to convert the AC power Pac into the second DC power Pdc2, and control the DC / AC conversion device 22 to convert the second DC power Pdc2 into the output power Po_1-Po_n. After confirming that the above operation is normal, the second controller 24 can control the bypass switch SW to be turned on, so that the uninterruptible power supply UPS_1-UPS_n enters the energy-saving mode. Specifically, when the bypass switch SW is turned on, the AC power Pac can be directly provided as the output power Po_1-Po_n to the critical load Lc_1-Lc_n, and the AC / DC conversion device 20 and the DC / AC conversion device 22 do not perform power conversion operations, such as but not limited to being disabled or hibernating, so that they do not consume power substantially (i.e., simply referred to as the energy-saving mode).

[0036] It is worth mentioning that in an embodiment, the operation of FIG. 3B when the commercial power 200 is invalid is similar to that of FIG. 3A, which will not be repeated here. On the other hand, in FIG. 3B, regardless of whether the commercial power 200 is valid or invalid, the AC / DC conversion device 20 only operates when the commercial power 200 is initially received for the first time to confirm whether the AC / DC conversion device 20 is operating normally, and almost does not operate at other times. Therefore, if the uninterruptible power supply UPS_1-UPS_n can exclude the operation of confirming whether the AC / DC conversion device 20 is normal, then the uninterruptible power supply UPS_1-UPS_n applied to the present disclosure can also omit the AC / DC conversion device 20 (represented by a dashed box that can be omitted under the above specific conditions), to achieve the effect of greatly saving the circuit cost.

[0037] In FIGS. 3A, 3B, the energy storage system 300 further comprises a plurality of unidirectional conduction components D1-Dn, and the unidirectional conduction components D1-Dn may, for example but not limited to, be diodes, thyristors, or other directional electronic components. The unidirectional conduction components D1-Dn are respectively connected in series to the external lines Te_1-Ten, and the number of the unidirectional conduction components D1-Dn can be equal to the number of the external lines Te_1-Ten. Among them, the unidirectional conduction components D1-Dn are in the forward direction from the DC conversion device 3 to the uninterruptible power supply UPS_1-UPS_n, so that the power of the DC bus DC_Bus_1-DC_Bus_n cannot be provided to the DC conversion device 3 through the external lines Te_1-Ten.

[0038] In particular, the battery B1-Bn (as shown in FIG. 1) is included in the general uninterruptible power supply UPS_1-UPS_n. When the uninterruptible power supply UPS_1-UPS_n needs to charge the battery B1-Bn, the uninterruptible power supply UPS_1-UPS_n charges the battery B1-Bn by the current from the DC bus DC_Bus_1-DC_Bus_n to the battery B1-Bn. However, the energy storage system 300 of the present disclosure converts the first DC power Pdc1 from the power conditioning device 1 to charge the battery module 2, and the energy storage system 300 and the uninterruptible power supply UPS_1-UPS_n are also independent devices. Therefore, the external line Te_1-Te_n can be connected in series with the unidirectional conduction component D1-Dn to avoid the second DC power Pdc2 on the DC bus DC_Bus_1-DC_Bus_n from being backfilled to the DC conversion device 3.

[0039] In detail, the present disclosure can couple a set of shared battery modules 2 to the energy storage system 300 and the multiple uninterruptible power supplies UPS_1-UPS_n of the uninterruptible power supply system UPS_S through the DC conversion device 3. Since the battery module 2 of the energy storage system 300 is a high DC voltage (for example, but not limited to, 900V-1000V), the DC voltage of the shared battery module 2 belongs to the high DC voltage application of the battery module 2, and the uninterruptible power supply UPS_1-UPS_n is a low DC voltage (for example, but not limited to, 400V-600V) application. Therefore, the battery module 2 can be designed to couple multiple sets of uninterruptible power supplies UPS_1-UPS_n, and protected and prevented from backfilling by the unidirectional conduction component D1-Dn.

[0040] Among them, the unidirectional conduction component D1-Dn uses a diode as the preferred embodiment. The reason is that since the diode does not need to use a controller to provide a control signal for driving, the use of a diode can achieve simple implementation without the need for complex control circuit functions. In addition, the DC conversion device 3 in some circuit architectures (for example, but not limited to, Flyback converter), the output end is usually connected in series with a circuit breaker (not shown in the figure), to avoid providing irregular output power to the load at the back end. Therefore, when the output end of the DC conversion device 3 has a circuit breaker, the unidirectional conduction component D1-Dn can be omitted to save circuit cost.

[0041] Referring to FIG. 3A and FIG. 3B, when the utility 200 is active, the utility 200 can supply the non-critical load Ln through the supply bus AC_Bus. When the utility 200 is inactive, further operations can be performed according to the cause of the inactivity of the utility 200. Specifically, the inactivity of the utility 200 can be caused by a power outage of the utility 200 or an abnormality of the AC power Pac provided by the utility 200 (e.g. but not limited to, abnormal AC voltage, frequency, etc.). Thus, when the utility 200 is inactive, the first controller 4 can determine whether the inactivity of the utility 200 is caused by a power outage or an abnormality of the utility 200 by detecting the supply bus AC_Bus, and perform corresponding operations. The status of the utility 200 can be detected by a controller other than the first controller 4, such as but not limited to a system controller (not shown) of the power system 100, and then provided to the first controller 4. Thus, the first controller 4 is not limited to detecting the status of the utility 200. Thus, when the utility 200 is inactive, the first controller 4 can control the power conditioning device 1 according to the power outage or the abnormality of the utility 200.

[0042] Specifically, when the inactivity of the utility 200 is caused by a power outage, the first controller 4 can control the power conditioning device 1 to convert the first DC power Pdcl to the AC power Pac to supply the non-critical load Ln. Alternatively, when the inactivity of the utility 200 is caused by a power outage, the first controller 4 can temporarily turn off the breaker Br coupled to the non-critical load Ln to temporarily stop supplying the non-critical load Ln. In this way, the power consumption of the battery module 2 can be reduced, and the time for which the critical loads Lc_1 to Lc_n can be supplied with power by the uninterruptible power supply UPS_1 to UPS_n can be extended.

[0043] On the other hand, when the inactivity of the utility 200 is caused by an abnormality of the utility 200, the first controller 4 can determine the parameter of the AC power Pac on the supply bus AC_Bus that is abnormal (e.g. but not limited to, voltage, current, reactive power, harmonic, etc.) by detecting the supply bus AC_Bus. Then, the first controller 4 can control the power conditioning device 1 to convert the first DC power Pdcl to the first compensation power Pc1, and supply the first compensation power Pc1 to the supply bus AC_Bus to compensate the abnormal AC power Pac to a normal AC power Pac, so as to avoid the risk of the non-critical load Ln being damaged by the abnormal AC power Pac.

[0044] Similarly, since the non-critical load Ln generally does not have a high requirement on the quality of the input source. Therefore, if the utility 200 fails, which is an abnormal condition of the utility, and the non-critical load Ln does not have a high requirement on the quality of the input source, the first controller 4 can also not control the power conditioning device 1 to convert the first direct current power Pdcl into the first compensation power Pc1, so that the uncompensated alternating current power Pac can still supply power to the non-critical load Ln. In this way, the power consumption of the battery module 2 can be saved, and the time for the uninterruptible power supply UPS_1-UPS_n to supply power to the critical load Lc_1-Lc_n can be extended. On the other hand, in order to maintain the continuous operation of the critical load Lc_1-Lc_n, the first controller 4 still controls the direct current conversion device 3 to convert the first direct current power Pdcl into the second direct current power Pdc2.

[0045] The above-mentioned energy storage system 300 can supply power to the non-critical load Ln or provide the first compensation power Pc1 to compensate for the alternating current power Pac, both of which are under the condition that the alternating current power Pac fails, and assuming that the battery capacity of the battery module 2 remains above a certain capacity threshold (for example, but not limited to, above 80% of the battery capacity). However, when the battery capacity of the battery module 2 is insufficient, the first controller 4 can disable the power conditioning device 1 to suspend the supply of power to the non-critical load Ln or the compensation of the alternating current power Pac, so as to avoid excessive consumption of the battery capacity and thus extend the time for the uninterruptible power supply UPS_1-UPS_n to supply power to the critical load Lc_1-Lc_n.

[0046] Similarly, when the utility 200 is valid, the energy storage system 300 can also perform compensation operation on the alternating current power Pac to improve the power quality of the alternating current power Pac. Specifically, when the utility 200 is valid, the first controller 4 can determine whether the battery capacity of the battery module 2 is higher than a first capacity threshold (for example, but not limited to, above 80% of the battery capacity), and according to the battery capacity being higher than the first capacity threshold, control the power conditioning device 1 to convert the first direct current power Pdcl into the second compensation power Pc2 to provide the second compensation power Pc2 to the power bus AC_Bus. The operation of providing the second compensation power Pc2 can adopt the operation mode of F-P, V-Q droop control (frequency-real power, voltage-reactive power), which calculates the corresponding reference active and reactive power by measuring the voltage amplitude and frequency of the distributed power output, to compensate for the alternating current power Pac and further improve the power quality of the alternating current power Pac, thereby stabilizing and improving the working efficiency of the non-critical load Ln.

[0047] Conversely, when the first controller 4 determines that the battery capacity is below the first capacity threshold, then the first controller 4 can no longer provide the second compensation power Pc2, but instead controls the power conditioning device 1 to convert the alternating power Pac inversely to the first direct power Pdcl for charging the battery module 2 to increase the endurance of the battery module 2. In addition, since the utility power 200 is still available, the alternating power Pac can be directly provided to the uninterruptible power supply UPS_l ~ UPS_n without the assistance of the energy storage system 300 (the condition that the energy storage system 300 can assist in power supply will be further described later to avoid confusion, and will not be described here).

[0048] wherein the first compensation power Pc1 is for compensating the non-compliant alternating power Pac, and the second compensation power Pc2 is for further improving the quality of the compliant alternating power Pac. Therefore, the power consumed by the power conditioning device 1 for converting the first compensation power Pc1 is generally larger than that for converting the second compensation power Pc2. In addition, although the specific capacity threshold and the first capacity threshold are taken as an illustrative example of 80% of the battery capacity, the specific capacity threshold and the first capacity threshold can be adjusted according to actual needs, and both can be the same threshold or different thresholds.

[0049] Referring again to FIGS. 3A and 3B, the power system 100 of the present disclosure can further include a peak shaving operation mode. Specifically, the peak shaving operation mode mainly controls the charging and discharging of the battery module 2 according to the time-of-use electricity price, the peak and off-peak periods of electricity consumption, and the like, so as to achieve peak-valley power shifting by charging and discharging of the energy storage system 300. Therefore, during the peak period of electricity consumption or when the electricity price is high, and the battery capacity of the battery module 2 is sufficient, the alternating power Pac obtained from the utility power 200 can be reduced, and the battery capacity can be used as the main power source to save electricity or alternating power Pac consumption. Conversely, during the non-peak period of electricity consumption or when the electricity price is low, the alternating power Pac is used as the power source as much as possible, and the battery capacity is fully charged as soon as possible to extend the time of backup power supply when the utility power 200 fails.

[0050] Further, the first controller 4 can set a certain period according to, for example, but not limited to, a peak period of electricity consumption or a condition of higher electricity price, and the first controller 4 can determine whether the battery capacity of the battery module 2 is higher than a second capacity threshold (for example, but not limited to, 50% of the battery capacity or above) in the certain period. When the first controller 4 determines that the battery capacity is higher than the second capacity threshold in the certain period, it means that the battery capacity is still sufficient. Therefore, the first controller 4 controls the DC conversion device 3 to convert the first DC power Pdcl to the second DC power Pdc2, so as to reduce the AC power Pac obtained from the commercial power 200. On the other hand, the operation of the energy storage system 300 to feed or compensate the power bus AC_Bus can be selectively performed according to the setting of the first controller 4, which operates as described above and will not be repeated here.

[0051] On the contrary, when the first controller 4 determines that the battery capacity is lower than the second capacity threshold in the certain period, it means that the battery capacity is insufficient and may not be able to support the backup power for a sufficient long time under a sudden condition. Therefore, the first controller 4 disables the DC conversion device 3, and can selectively convert the AC power Pac to charge the battery module 2 by the power conditioning device 1, or maintain the battery capacity at the second capacity threshold (which can be set by the user).

[0052] In the certain period and when the battery capacity of the battery module 2 is higher than the second capacity threshold, the power system 100 can selectively supply the critical loads Lc_1~Lc_n and / or the non-critical loads Ln by the energy storage system 300 alone, so as to completely not obtain the AC power Pac. Alternatively, the power system 100 can selectively supply the critical loads Lc_1~Lc_n by the energy storage system 300 and the outage devices UPS_1~UPS_n together, and supply the non-critical loads Ln by the energy storage system 300 and the AC power Pac together. In this way, the AC power Pac consumed by the power system 100 can be easily adjusted to avoid the condition that the AC power Pac consumed by the power system 100 exceeds the preset upper limit value in the certain period.

[0053] In another aspect, when the power demand is not at the peak period or when the electricity price is low (i.e. not at the specific period), the power system 100 can obtain the power source from the AC power Pac as much as possible and charge the battery module 2 as fast as possible. Therefore, the first controller 4 disables the DC conversion device 3 and controls the power conditioning device 1 to convert the AC power Pac to charge the battery module 2 to prolong the backup power time of the energy storage system 300. In short, whether the specific period is set or not, the power supply, charging and compensation power operations of the energy storage system 300 are determined by the first controller 4 and the corresponding control is performed accordingly. As can be inferred from the foregoing, further elaboration is not necessary. In addition, although the second capacity threshold is taken as an illustrative example of 50% of the battery capacity, the second capacity threshold can be adjusted according to actual needs, or even adjusted in conjunction with the first capacity threshold, and further elaboration is not necessary. Since the AC power Pac obtained from the utility power 200 needs to be reduced as much as possible during the peak period of power demand or when the electricity price is high, the second capacity threshold is generally set lower than the first capacity threshold, but is not limited thereto.

[0054] Please refer to FIG. 3A and FIG. 3B again. The battery module 2 further comprises a plurality of batteries 26, and the batteries 26 can form the battery module 2 by being connected in series or in parallel with each other. The first controller 4 can detect the voltage, current, available capacity and other parameters of each battery 26 in the battery module 2 through, for example but not limited to, a battery management system (not shown in the figure), and regulate each battery 26 according to the parameters of each battery 26 and the power demand of the power conditioning device 1 and the DC conversion device 3. When the available capacity of a certain battery 26 is insufficient (for example but not limited to, lower than the low capacity threshold), the first controller 4 can individually disable this battery 26 through the battery management system, so that the disabled battery 26 waits for the opportunity scheduled by the first controller 4 for the power conditioning device 1 to charge it. After the first controller 4 integrates the available capacities of all the batteries 26, the battery capacity of the entire battery module 2 can be calculated, and the regulation is performed according to the difference between the battery capacity and the specific capacity threshold, the first capacity threshold or the second capacity threshold.

[0055] Please refer to FIG. 4 for an external line connection diagram of the present disclosure, and also refer to FIGS. 2-3B. In FIG. 4, the external line Te_1-Ten includes a power line L1 for transmitting power and a communication line L2 for communication. The communication line L2 is coupled to the first controller 4 and the second controller 24, and the first controller 4 and the second controller 24 transmit information to each other through the communication line L2, so that each other knows information such as but not limited to parameters detected by the first DC power Pdc1, the second DC power Pdc2, and a specific period, parameters preset by each controller to each other, and operating states of each internal device. In this way, the mutual operation of the energy storage system 300 and the UPS_S can be more compatible, so as to further improve the operation efficiency of the power system 100.

[0056] Specifically, in the operation of the conventional backup power supply of the UPS_1-UPS_n, the operation mode of the UPS_1-UPS_n will not be changed by the command (or information) of the energy storage system 300. However, when the external line Te_1-Ten includes the communication line L2 so that the first controller 4 and the second controller 24 can communicate with each other, the second controller 24 can control the AC / DC converter 20 and the DC / AC converter 22 according to the current operation of the energy storage system 300 to cooperate with the current operation of the energy storage system 300. For example, in the conventional UPS_1-UPS_n, the second controller 24 only controls the AC / DC converter 20, the DC / AC converter 22, and the bypass switch SW to supply power to the critical load Lc_1-Lc_n according to whether the commercial power 200 is effective, and has nothing to do with the operation mode of peak shaving and valley filling.

[0057] However, when the commercial power 200 is effective and the battery module 2 can supply power to the outside if the battery capacity is higher than the second capacity threshold in a specific period, the first controller 4 can control the DC converter 3 to convert the first DC power Pdc1 to the second DC power Pdc2. At this time, if the external line Te_1-Ten includes the communication line L2 so that the first controller 4 and the second controller 24 can communicate with each other, the second controller 24 can know through the communication line L2 that the operation of the DC converter 3 is to provide the second DC power Pdc2, and whether the second DC power Pdc2 can meet the demand of the operation of the critical load Lc_1-Lc_n. Therefore, the second controller 24 can disable the AC / DC converter 20, or even turn off the bypass switch SW, to save the power consumption of the UPS_1-UPS_n.

[0058] It is worth mentioning that in one embodiment, the external lines Te_1~Te_n can only include the power line L1 without the communication line L2. The second controller 24 can detect whether the external lines Te_1~Te_n provide the second direct current power Pdc2 by detecting the external lines Te_1~Te_n, and the specific period can be preset in the second controller 24 in a set manner, so that the power consumption of the uninterruptible power supply UPS_1~UPS_n can be saved without the communication line L2. In addition, if the power system 100 does not have the peak shaving operation (i.e. the specific period is not set), the external lines Te_1~Te_n can also only include the power line L1 and only perform simple power transmission.

[0059] Therefore, according to the above-mentioned operations of the energy storage system 300, the operation method of the energy storage system shown in FIG. 5 can be summarized for the normal operation of the commercial power 200 or the possible accident situation. Specifically, in step S100 and step S200 of FIG. 5, it is detected whether the commercial power fails. And after the commercial power 200 fails, the operations of step S120 and step S220 are performed to control the direct current conversion device 3 to convert the first direct current power Pdc1 into the second direct current power Pdc2, and the second direct current power Pdc2 is provided to the direct current bus DC_Bus_1~DC_Bus_n of the uninterruptible power supply UPS_1~UPS_n through the plurality of external lines Te_1~Te_n, respectively.

[0060] Further, in step (S100), it is determined whether the utility interruption condition occurs. When the utility interruption condition occurs, the battery module power supply is switched (S120). At this time, the first controller 4 controls the DC conversion device 3 to convert the first DC power Pdcl to the second DC power Pdc2. After step (S120), the black start is performed to provide the AC power to the power supply bus (S140). At this time, the first controller 4 controls the power conditioning device 1 to convert the first DC power Pdcl to the AC power Pac to provide the AC power Pac to the power supply bus AC_Bus. Finally, the utility is detected to be valid and switched to the energy saving mode (S300). When the utility 200 is detected to be valid (representing the AC power Pac is normal), the second controller 24 can first control the AC / DC conversion device 20 to convert the AC power Pac to the second DC power Pdc2, and control the DC / AC conversion device 22 to convert the second DC power Pdc2 to the output power Po_l ~ Po_n. After confirming that the above operation is normal, the second controller 24 can control the bypass switch SW to be turned on, so that the UPS 1 ~ UPS_n enters the energy saving mode. In addition, if the UPS 1 ~ UPS_n omits the AC / DC conversion device 20, the second controller 24 can directly control the bypass switch SW to be turned on, so that the UPS 1 ~ UPS_n enters the energy saving mode. After step (S300), it can return to step (S100) to continuously detect the condition of the utility 200.

[0061] Similarly, in step (S200), it is determined whether the utility abnormal condition occurs. When the utility abnormal condition occurs, the battery module power supply is also switched (S220). And after step (S220), the first compensation power is provided to the power supply bus (S240). At this time, the first controller 4 controls the power conditioning device 1 to convert the first DC power Pdcl to the first compensation power Pc1 to provide the first compensation power Pc1 to the power supply bus AC_Bus to compensate the non-standard AC power Pac to the standard AC power Pac, avoiding the non-standard AC power Pac provided to the non-critical load Ln to cause the risk of the non-critical load Ln to fail. And after step (S240), when the utility 200 is restored to be valid, step (S300) is entered, and step (S100) is returned to continuously detect the condition of the utility 200. Wherein, the judgment order of steps (S100) and (S200) can be mutually adjusted, which does not affect the operation process of the energy storage system 300.

[0062] In another aspect, after steps (S100) and (S200), the utility 200 is active, and the process proceeds to step (S400) to determine whether the battery capacity of the battery module is above a first capacity threshold. When the battery capacity of the battery module 2 is below the first capacity threshold, the uninterruptible power system enters the economy mode, and the power conditioning device charges the battery module (S600). When the first controller 4 determines that the battery capacity is below the first capacity threshold, the first controller 4 can control the power conditioning device 1 to convert the AC power Pac to the first DC power Pdcl to charge the battery module 2 to increase the endurance of the battery module 2. In addition, since the utility 200 is still active, the AC power Pac can be directly provided to the uninterruptible power systems UPS_l-UPS_n without the assistance of the energy storage system 300, and the uninterruptible power systems UPS_l-UPS_n can turn on the bypass switches SW to enter the economy mode.

[0063] Conversely, when the battery capacity of the battery module 2 is above the first capacity threshold, the second compensation power is provided to the bus (S420). At this time, the first controller 4 can control the power conditioning device 1 to convert the first DC power Pdcl to the second compensation power Pc2 to provide the second compensation power Pc2 to the bus AC_Bus. Then, the peak shaving operation is performed (S440). At this time, the first controller 4 controls the DC conversion device 3 to convert the first DC power Pdcl to the second DC power Pdc2 to reduce the AC power Pac obtained from the utility 200 for a certain period of time.

[0064] After step (S440), it is determined whether any battery of the battery module is disabled (S460). Since the available capacity of each battery 26 in the battery module 2 is not the same, during the process of step (S440) to consume the battery capacity of the battery module 2 to power the critical loads Lc_l-Lc_n and / or the non-critical loads Ln, there can be some batteries 26 whose available capacity is insufficient (i.e., below the low capacity threshold) and are disabled. Therefore, the first controller 4 determines whether any battery 26 is disabled. When no battery 26 is disabled, the process can return to step (S100) to continuously detect the status of the utility 200. Conversely, when any battery 26 is disabled, the battery capacity of the entire battery module is calculated based on the available capacity of the remaining batteries (S480). And the power conditioning device is controlled to charge the disabled battery according to the schedule (S500). When the available capacity of a battery 26 is insufficient (e.g., but not limited to, below the low capacity threshold), the first controller 4 can individually disable the battery 26 through the battery management system, and the disabled battery 26 waits for the opportunity for the first controller 4 to schedule the power conditioning device 1 to charge it. And after step (S500), the process can return to step (S100) to continuously detect the status of the utility 200.

[0065] In summary, the above-mentioned architecture and system context, the present disclosure uses a shared battery for the design and operation mode of the energy storage system 300 and the uninterruptible power supply system UPS_S. Compared with the current two sets of independent operation of the battery module of the energy storage system 300 and the battery B1-Bn of the uninterruptible power supply system UPS_S, the present disclosure brings obvious cost benefits and optimizes the user's electricity consumption effect and saves money. The dual role of the shared battery in the energy storage system 300 not only maximizes the utilization efficiency of the battery module 2, but also significantly reduces the equipment and operation cost, achieving the best balance between economy and efficiency, not only ensuring the stable operation of the client power system 100, but also laying a solid foundation for the development of future smart energy systems. It is worth mentioning that in an embodiment, the detailed operation method not described in Figure 5 can be combined with the detailed operation recorded in Figures 2-3B, so those skilled in the art can reasonably infer that in addition to the preferred embodiment of the present disclosure in Figure 5, the operation method of the energy storage system is feasible.

[0066] However, the above-mentioned is only a detailed description of the preferred embodiment of the present disclosure and the accompanying drawings, but the features of the present disclosure are not limited thereto, and are not intended to limit the present disclosure. The scope of the present disclosure should be based on the scope of the following claims, and any embodiments similar to the spirit and scope of the claims of the present disclosure should be included in the scope of the present disclosure. Any changes or modifications within the scope of the present disclosure can be covered by the patent scope of the present case.

Claims

1. An energy storage system coupled to an AC power grid via an AC power bus, the AC power grid comprising a plurality of uninterruptible power supplies coupled to the AC power bus, the energy storage system comprising: a power conditioning device coupled to the AC power bus; a battery module coupled to the power conditioning device; a DC conversion device coupled at one end to the battery module and at another end to a plurality of DC buses of the plurality of uninterruptible power supplies via a plurality of external lines; and a first controller coupled to the power conditioning device and the DC conversion device, the first controller controlling the power conditioning device to convert AC power from the AC power bus to first DC power to charge the battery module when the AC power grid is operating normally; wherein the first controller controls the DC conversion device to convert the first DC power to second DC power and provide the second DC power to the plurality of DC buses via the plurality of external lines when the AC power grid fails.

2. The energy storage system of claim 1, wherein the AC power grid further comprises a non-critical load coupled to the AC power bus, the first controller determining whether the AC power grid failure is an AC power interruption condition or an AC power anomaly condition when the AC power grid fails, and controlling the power conditioning device according to the AC power interruption condition or the AC power anomaly condition.

3. The energy storage system of claim 2, wherein the first controller controls the power conditioning device to convert the first DC power to the AC power to power the non-critical load when the AC power grid failure is the AC power interruption condition.

4. The energy storage system of claim 2, wherein the first controller controls the power conditioning device to convert the first DC power to first compensation power to provide the first compensation power to the AC power bus to compensate for the AC power provided by the AC power grid when the AC power grid failure is the AC power anomaly condition.

5. The energy storage system of claim 1, wherein the first controller determines whether a battery capacity of the battery module is above a first capacity threshold when the AC power grid is operating, and controls the power conditioning device to convert the first DC power to second compensation power to provide the second compensation power to the AC power bus to compensate for the AC power provided by the AC power grid when the battery capacity is above the first capacity threshold.

6. The energy storage system of claim 5, wherein the first controller disables the DC conversion device and controls the power conditioning device to convert the AC power to the first DC power when the first controller determines that the battery capacity is below the first capacity threshold.

7. The energy storage system of claim 5, wherein the first controller sets a particular time period, and controls the DC conversion device to convert the first DC power to the second DC power according to the battery capacity being above a second capacity threshold at the particular time period. ​ ​ ​ ​ ​ ​ 8. The energy storage system of claim 5, wherein the battery module comprises: a plurality of batteries forming the battery module in series or in parallel with each other; wherein the first controller detects a plurality of available capacities of the plurality of batteries, and calculates the battery capacity of the battery module according to the plurality of available capacities.

9. The energy storage system of claim 1, further comprising: a plurality of unidirectional conducting components connected in series to the plurality of external lines, respectively; wherein the plurality of unidirectional conducting components are forward- connected from the DC conversion device to the plurality of uninterruptible devices.

10. A power system coupled to a utility, and comprising: a power supply bus receiving alternating power from the utility; a plurality of uninterruptible devices coupled to the power supply bus and couplable to a plurality of critical loads for powering the plurality of critical loads correspondingly by converting the alternating power into a plurality of output powers; and an energy storage system coupled to the power supply bus and the plurality of uninterruptible devices, and comprising: a power conditioning device coupled to the power supply bus; a battery module coupled to the power conditioning device; a DC conversion device having one end coupled to the battery module and the other end coupled to a plurality of DC buses of the plurality of uninterruptible devices through a plurality of external lines, respectively; and a first controller coupled to the power conditioning device and the DC conversion device, and controlling the power conditioning device to convert the alternating power into a first DC power for charging the battery module when the utility is in operation; wherein when the utility is failed, the first controller controls the DC conversion device to convert the first DC power into a second DC power, and to provide the second DC power to the plurality of DC buses through the plurality of external lines, respectively, and the plurality of uninterruptible devices correspondingly provide the plurality of output powers according to the second DC power.

11. The power system of claim 10, wherein the plurality of uninterruptible devices each comprises: an AC / DC conversion device coupled to the power supply bus; a DC / AC conversion device coupled to the AC / DC conversion device through a DC bus of the plurality of DC buses and correspondingly coupled to a critical load of the plurality of critical loads; and a second controller coupled to the AC / DC conversion device and the DC / AC conversion device; wherein when the utility is failed, the second controller disables the AC / DC conversion device, and controls the DC / AC conversion device to convert the second DC power into an output power of the plurality of output powers.

12. The power system of claim 11, wherein the plurality of uninterruptible devices each further comprises: a bypass switch having one end coupled to the AC / DC conversion device and the power supply bus, and the other end coupled to an output terminal of the DC / AC conversion device.

13. The power system of claim 12, wherein when the utility is valid, the second controller controls the bypass switch to be turned on for providing the alternating power as the output power. ​ 14. The power system of claim 12, wherein the second controller communicates with the first controller to learn a specific time period set by the first controller for the first DC power, and the second controller disables the AC / DC conversion device or turns off the bypass switch when the AC power is active and in the specific time period, the DC conversion device provides the second DC power.

15. A method for operating an energy storage system coupled to an AC power of a power system through a power bus, and the power system includes a plurality of uninterruptible power supplies coupled to the power bus, the method comprising: detecting whether the AC power is failed; controlling a DC conversion device to convert a first DC power provided by a battery module to a second DC power for providing the second DC power to a plurality of DC buses of the plurality of uninterruptible power supplies through a plurality of external lines according to the AC power is failed; determining whether the AC power failure is an AC power interruption condition or an AC power abnormal condition; controlling a power conditioning device to convert the first DC power to an AC power for providing the AC power to the power bus according to the AC power failure is the AC power interruption condition; and controlling the power conditioning device to convert the first DC power to a first compensation power for providing the first compensation power to the power bus to compensate the AC power provided by the AC power according to the AC power failure is the AC power abnormal condition.

16. The method of claim 15, further comprising: determining whether a battery capacity of the battery module is higher than a first capacity threshold according to the AC power is active; controlling the power conditioning device to convert the first DC power to a second compensation power for providing the second compensation power to the power bus to compensate the AC power provided by the AC power according to the battery capacity is higher than the first capacity threshold; and disabling a DC conversion device according to the battery capacity is lower than the first capacity threshold, and controlling the power conditioning device to convert the AC power to the first DC power.

17. The method of claim 16, further comprising: setting a specific time period; and controlling the DC conversion device to convert the first DC power to the second DC power according to the battery capacity is higher than a second capacity threshold in the specific time period.

18. The method of claim 16, further comprising: determining whether at least one battery of a plurality of batteries in the battery module is disabled; calculating the battery capacity of the battery module according to available capacities of remaining batteries when the at least one battery is disabled; controlling the power conditioning device to charge the at least one battery according to a schedule. ​

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