TWI891353B - Power supply system and control method - Google Patents

Abstract

A control method applied to a power supply system, wherein the power supply system includes at least a first power unit and a second power unit, and the first power unit is configured to provide power to an electric load by power provided by a power supply, the control method includes: detecting a load status of the power supply system; when the load status is determined to be a peak load, generating a trigger signal; and in response to the trigger signal, disabling a first-stage converter in the second power unit, and controlling a energy storage capacitor in the second power unit to provide power to the electric load, wherein the energy storage capacitor is coupled between the first-stage converter and a second-stage converter in the second power.

Description

Power supply system and control method

This disclosure relates to power supply technology, particularly a power supply system and control method.

With the rapid development of the economy and industry, the importance of power supply systems is increasing. Generally speaking, most industrial equipment is driven by direct current (DC). Therefore, a converter is required between the distribution system and the equipment to convert AC power from the grid into DC. Whether the power can remain stable during the transmission and conversion process is a key performance indicator of the power system.

This disclosure relates to a power supply system comprising at least a first power unit and a second power unit. The first power unit is coupled between a power supply and a load to supply power to the load. The second power unit is connected in parallel with the first power unit and coupled between the power supply and the load. The second power unit comprises an energy storage capacitor, a first-stage converter, a first-stage converter, and a processor. The first-stage converter is coupled between the power supply and the energy storage capacitor. The second-stage converter is coupled between the energy storage capacitor and the load. The processor is coupled to the first-stage converter and the second-stage converter. When the second power unit is in standby mode, the processor switches the second power unit to power supply mode in response to a trigger signal. When the second power supply unit is in power supply mode, the processor is used to disable the first-stage converter, and the energy storage capacitor supplies power to the power load through the second-stage converter.

The present disclosure also relates to a control method for a power supply system, wherein the power supply system includes at least a first power unit and a second power unit, and the first power unit is configured to supply power to an electrical load using power from a power supply. The control method includes: detecting a load status of the power supply system; generating a trigger signal when the load status is determined to be a peak load; and in response to the trigger signal, disabling a first-stage converter in the second power unit and controlling an energy storage capacitor in the second power unit to supply power to the electrical load, wherein the energy storage capacitor is coupled between the first-stage converter and the second-stage converter in the second power unit.

Accordingly, by utilizing the energy storage capacitor of the second power unit to discharge during peak loads, the output power of the power supply system can be replenished while also avoiding output current surges.

100: Power supply system

110: First power supply unit

120: Second power supply unit

130: Controller

121: First stage converter

122: Second stage converter

123:Processor

124: Detection Circuit

140: Detection Circuit

400: Power supply system

410A: Power supply unit

410B: Power supply unit

A1-A6: Power supply unit

B1-B6: Power supply unit

C1-C6: Power supply unit

C21: Energy storage capacitor

PW1-PW3: Curve

PL: Power load

PS: Power supply

R1: First column

R2: Second column

R3: Third column

Sd: Detection signal

Sw: trigger signal

S501-S506: Steps

T1: Time point

T2: Time point

Tp: Power cycle

Tx: Reset time

W21: Switching circuit

Figure 1A is a schematic diagram of a power supply system according to some embodiments of the present disclosure.

Figure 1B is a schematic diagram of a second power unit according to some embodiments of the present disclosure.

Figures 2A to 2C are schematic diagrams showing the load and current status of a power supply system according to some embodiments of the present disclosure.

Figures 3A-3B are schematic diagrams of a second power unit according to some embodiments of the present disclosure.

Figures 3C and 3D are schematic diagrams of power supply systems according to some embodiments of the present disclosure.

Figure 4 is a schematic diagram of a power supply system according to other embodiments of the present disclosure.

Figure 5 is a flow chart of a power supply system control method according to some embodiments of the present disclosure.

The following figures illustrate several embodiments of the present invention. For clarity, numerous practical details are included in the following description. However, it should be understood that these practical details are not intended to limit the present invention. In other words, these practical details are not essential to some embodiments of the present invention. Furthermore, to simplify the drawings, some commonly used structures and components are depicted in simplified schematic form.

In this document, when an element is referred to as being "connected" or "coupled," it may refer to being "electrically connected" or "electrically coupled." "Connected" or "coupled" may also refer to the coordinated operation or interaction between two or more elements. Furthermore, although terms such as "first," "second," etc. may be used herein to describe different elements, these terms are intended solely to distinguish between elements or operations described using the same technical terms. Unless the context clearly indicates otherwise, these terms are not intended to specifically designate or imply a sequence or order, nor are they intended to limit the present invention.

FIG1A is a schematic diagram of a power supply system 100 according to some embodiments of the present disclosure. In one embodiment, power supply system 100 includes a plurality of power supply units (PS) A1-A6, B1-B6, and C1-C6. Power supply units A1-A6, B1-B6, and C1-C6 are coupled between a power supply source (PS) (e.g., a utility grid) and a power load (PL) (e.g., a machine).

In one embodiment, power units A1-A3, B1-B3, and C1-C3 each constitute a three-phase power supply, corresponding to the three phases UV, W. Power units A4-A6, B4-B6, and C4-C6 constitute another three-phase power supply, also corresponding to the three phases UV, W. However, the present disclosure is not limited to this. In other embodiments, each power unit may also be a single-phase power supply.

Each power unit A1-A6, B1-B6, and C1-C6 can be a power supply, a power conversion circuit, or a similar converter. In one embodiment, the power unit includes an AC-DC converter circuit to convert the AC power provided by the power source PS into DC power of an appropriate voltage, which is then supplied to the power load PL. Since the circuitry and principles of power supplies are well understood by those skilled in the art, they will not be further elaborated here.

Furthermore, depending on the configuration of power supply system 100 (e.g., the rack installation or setup), power units A1-A6, B1-B6, and C1-C6 can be divided into different rows (Rows) R1-R3. In one embodiment, power units A1-A6 in the first row R1 and B1-B6 in the second row R2 are the normal operating power supplies, while power units C1-C6 in the third row R3 are the redundant power supplies. In other words, when power supply system 100 is in a normal load state, power units A1-A6 and B1-B6 supply power to power load PL based on the power provided by supply source PS. When the power supply system 100's power demand increases and reaches a peak load, power units C1-C6 will activate in response to a trigger signal. The detailed operation will be described in the following paragraphs.

It's important to note that the configuration of the backup power supply can be adjusted as needed and is not limited to the configuration shown in Figure 1A. For example, in another embodiment, power units C1-C3 may serve as backup power supplies, while power units C4-C6 serve as normal power supplies. In other embodiments, power units A1-A6 may serve as backup power supplies, while the remaining power units serve as normal power supplies. For ease of explanation, the normal power supply will be referred to as the first power supply unit 110, and the backup power supply will be referred to as the second power supply unit 120.

Figure 1B shows a schematic diagram of a second power supply unit 120 according to the present disclosure. Second power supply unit 120 is connected in parallel to first power supply unit 110. In one embodiment, second power supply unit 120 includes a first-stage converter 121, a second-stage converter 122, a processor 123, and an energy storage capacitor C21. First-stage converter 121 is coupled between power supply PS and energy storage capacitor C21. Furthermore, depending on the type of power supply PS (e.g., DC or AC), first-stage converter 121 can be an AC-DC converter circuit or a DC-DC converter circuit.

The second-stage converter 122 is coupled between an energy storage capacitor C21 and a power load PL. One end of the energy storage capacitor C21 is coupled between the first-stage converter 121 and the second-stage converter 122, and the other end is coupled to a reference potential (e.g., ground).

Processor 123 is coupled to first-stage converter 121 and second-stage converter 122 and can control second power supply unit 120 to operate in either standby mode or power supply mode. When power supply system 100 is in a normal load state (i.e., when the power required by power load PL is within a normal range), second power supply unit 120 operates in standby mode. The power provided by first power supply unit 110 is sufficient to meet the power load PL's requirements. Therefore, processor 123 controls energy storage capacitor C21 to maintain charge and controls second power supply unit 120 to not supply power to power load PL, or controls the power supplied by second power supply unit 120 to be less than a preset value (e.g., extremely low power). Since those skilled in the art understand how to control the power supplied by the second-stage converter, this method will not be further elaborated here.

Continuing from the above, when power supply system 100 is experiencing a peak load and the power provided by first power unit 110 cannot meet the power load PL's requirements, second power unit 120 receives a trigger signal and switches from "standby mode" to "power supply mode." At this point, processor 123 disables first-stage converter 121 and discharges energy storage capacitor C21, allowing power to be supplied to power load PL via second-stage converter 122, thereby sharing the output current required during peak load conditions. This function is referred to herein as "current sharing."

In some embodiments, second power unit 120 further includes a switching circuit W21. Switching circuit W21 is coupled to first-stage converter 121, thereby coupling first-stage converter 121 to power supply PS via switching circuit W21. Processor 123 controls switching circuit W21 to turn it on or off, thereby enabling or disabling first-stage converter 121. In other embodiments, processor 123 may directly control a switch within first-stage converter 121 to enable or disable first-stage converter 121. Similarly, processor 123 may control second-stage converter 122 in a similar manner.

Accordingly, when the power load PL requests more power from the power supply system 100, the power supply system 100 can activate the second power unit 120 to output power using the energy pre-stored in the energy storage capacitor C21, thereby meeting the additional power demand. Because the second power unit 120 is powered by internal power (energy storage capacitor C21) in "power supply mode," it does not need to request a higher current from the power supply PS. This prevents current surges in the power supply system 100, which could damage internal components of the power supply system 100.

In one embodiment, the circuit structure of the first power unit 110 can be identical to that of the second power unit 120. In another embodiment, the first power unit 110 can include the first-stage converter 121 and the second-stage converter 122 shown in FIG. 1B , and can also include an energy storage capacitor C21, but not the switching circuit W21. As those skilled in the art will appreciate various implementations of the power unit, they will not be further described here.

Figures 2A-2C illustrate the load and current states of a power supply system according to some embodiments of the present disclosure. Figure 2A shows the state of a power supply (second power unit 120) without backup. Referring to Figure 2A, the first waveform at the top represents the power demand of the power load PL, the second waveform represents the operating power of each power unit, and the third waveform represents the current waveform supplied by the power supply PS to the power supply system 100. As can be seen from the diagram, between time points T1 and T2, the power demand of the power load PL suddenly increases, representing a "peak load." To increase output power, the first power unit 110 increases its operating power, but this action requires a higher current from the power supply PS. As shown in the current waveform in Figure 2A, a current surge will occur at this time, potentially damaging components within the power supply system 100.

Figure 2B is a state diagram of an embodiment of the present disclosure, in which the power supply system 100 has a second power unit 120 as a backup. As shown in the second waveform diagram of Figure 2B, in the "normal load" state, the power supply system 100 only outputs power through the first power unit 110, while the second power unit 120 remains in standby mode. In standby mode, the second power unit 120 does not provide power, or the power supply is much less than that of the first power unit 110 (as shown in Figure 2B, curve PW3 is much less than curves PW1 and PW2). At time points T1-T2, when the power supply system 100 is in a "peak load", the second power unit 120 is activated and supplies power to the power load PL through the energy storage capacitor C21. Accordingly, no current surge will occur between the power supply PS and the first power unit 110/second power unit 120, and the power supply requirements of peak loads can be met.

Referring to Figure 2B , in one embodiment, while the second power supply unit 120 is supplying power to the power load PL via the energy storage capacitor C21 and the second-stage converter 122, if the processor 123 receives a standby signal, it indicates that the load status of the power supply system 100 has returned to "normal load." At this point, the processor 123 controls the energy storage capacitor C21 to stop discharging, returning the second power supply unit 120 to standby mode. In some embodiments, the processor 123 may enable the first-stage converter 121 or turn on the switch circuit W21 to charge the energy storage capacitor C21 with power from the supply power source PS. In addition, the processor 123 can simultaneously disable the second-stage converter 122 or change the operating frequency of the second-stage converter 122 to ensure that the second power supply unit 120 returns to the standby mode.

When the second power supply unit 120 returns to standby mode, the processor 123 first controls the energy storage capacitor C21 to stop discharging (e.g., disabling or changing the operating state of the second-stage converter 122). Simultaneously, the processor 123 starts counting. After the standby mode is restored and a reset time Tx (e.g., one power cycle) has elapsed, the processor 123 enables the first-stage converter 121 and charges the energy storage capacitor C21 using power from the supply power source PS.

Figure 2C shows another embodiment of the present disclosure, in which the power supply system 100 includes a second power supply unit 120 for backup. Figure 2C differs from Figure 2B in the method for charging the energy storage capacitor C21. In this embodiment, when the second power supply unit 120 returns to standby mode, the processor 123 simultaneously controls the energy storage capacitor C21 to stop discharging and enables the first-stage converter 121 to charge the energy storage capacitor C21 with power from the supply power source PS for a charging period.

If the power supply PS provides AC power, the charging time can be multiple power cycles Tp. In other words, the processor 123 sets the subsequent multiple power cycles Tp as the charging time, thereby charging the energy storage capacitor C21 with the power provided by the power supply PS. A "power cycle" is the current cycle during which the power supply PS provides AC power to the power supply system 100 (as shown by the label Tp in Figure 2C). On the other hand, if the power supply PS provides DC power, the charging time can be a preset fixed period of time.

As mentioned above, in some embodiments, during the charging period (e.g., multiple power cycles) after resuming standby mode, the processor 123 controls the charging current of the energy storage capacitor C21. In other words, the processor 123 charges the energy storage capacitor C21 at a fixed/preset current value and fully charges the energy storage capacitor C21 within the set charging time (e.g., three power cycles).

As previously described, the second power unit 120 enters standby mode and power supply mode in response to the standby signal and the trigger signal, respectively. In one embodiment, the second power unit 120 remains in standby mode until it receives the trigger signal. In standby mode, the processor 123 enables the first-stage converter 121 to charge the energy storage capacitor C21 with power from the supply power source PS, ensuring sufficient power in the energy storage capacitor C21 when the second power unit 120 switches to power supply mode.

The following describes different ways of generating a "trigger signal" in various embodiments of the present disclosure. Figure 3A shows a schematic diagram of the second power unit 120 according to some embodiments of the present disclosure. In one embodiment, the second power unit 120 further includes a detection circuit 124. The detection circuit 124 is coupled to the processor 123 and the output line of the second power unit 120. The detection circuit 124 is used to detect the electrical signal on the output line of the second power unit 120 to obtain (e.g., determine or calculate) the slew rate of the first power unit. The slew rate can reflect the load status of the power supply system 100.

As mentioned above, in one embodiment, detection circuit 124 provides the detected slew rate as a detection signal Sd to processor 123, allowing processor 123 to determine whether the slew rate is greater than a peak threshold. If the slew rate is greater than the peak threshold, it indicates that the power supply system 100 is experiencing a peak load. In this case, processor 123 will automatically generate a trigger signal. In other embodiments, detection circuit 124 may independently determine whether the slew rate is greater than the peak threshold. Only if the slew rate is greater than the peak threshold will detection circuit 124 generate detection signal Sd and transmit it to processor 123. In other words, detection signal Sd can serve as a trigger signal.

In other embodiments, the trigger signal may be generated based on a change in the output current of the first power supply unit 110 or a load prediction signal. Please refer to Figures 1A and 3B , where Figure 3B is a schematic diagram of a second power supply unit 120 according to another embodiment of the present disclosure. In this embodiment, the power supply system 100 further includes a controller 130. The controller 130 is coupled to the first power unit 110, the second power unit 120, and the power load PL, respectively. It is used to detect output current changes of the first power unit 110 (e.g., by detecting the output line of the first power unit 110) or to obtain a load prediction signal (e.g., by detecting a signal input to the power load PL). The controller 130 generates a trigger signal Sw and provides the trigger signal Sw to the processor 123 of the second power unit 120.

As shown in Figure 1A , when the power supply system 100 supplies power to the power load PL, it simultaneously transmits output power information as a detection signal Sd to each power unit 110/120 and/or provides it to the controller 130. Therefore, the processor 123 of the second power unit 120 or the controller 130 can use the detection signal Sd to determine changes in the output current of the first power unit 110 and generate/acquire the trigger signal Sw.

In another embodiment, the controller 130 can also monitor the operating status of the power load PL to obtain a load prediction signal and provide a trigger signal Sw to the second power unit 120 when the load prediction signal is greater than a preset value.

Figure 3C is a schematic diagram of a power supply system according to another embodiment of the present disclosure. In this embodiment, power supply system 100 includes a detection circuit 140. Detection circuit 140 is coupled between power units 110 and 120 and a power load PL. Detection circuit 140 detects the slew rate of first power unit 110 and provides a detection signal Sd to controller 130. Based on detection signal Sd, controller 130 determines whether the slew rate is greater than a peak threshold and generates a trigger signal Sw to second power unit 120.

Figure 3D is a schematic diagram of a power supply system according to another embodiment of the present disclosure. In this embodiment, the first power unit 110 includes a detection circuit 140. The detection circuit 140 is used to detect the slew rate of the first power unit to generate a detection signal Sd. If the first power unit 110 determines that the slew rate is greater than a peak threshold (e.g., via an internal processor or by the detection circuit), it indicates that the power supply system 100 is experiencing a peak load. In this case, the detection circuit 140 generates a trigger signal Sw to the second power unit 120.

In other embodiments, the detection circuit 140 directly transmits the detection signal Sd to the second power unit 120. After receiving the detection signal Sd, the second power unit 120 independently determines whether the slew rate is greater than the peak threshold. If the slew rate is greater than the peak threshold, the second power unit 120 generates the trigger signal Sw.

Figure 4 shows a schematic diagram of a power supply system 400 according to other embodiments of the present disclosure. Power supply system 400 includes multiple power supply units 410A and 410B, which are connected in parallel. In one embodiment, power supply unit 410A serves as the normal power supply, while power supply unit 410B serves as the backup power supply. However, the number of power supply units 410A and 410B can be adjusted as needed.

FIG5 is a flow chart of a power supply system control method according to some embodiments of the present disclosure. Please refer to FIG5A, FIG5B, and FIG5B in conjunction with FIG5A. In step S501, the power supply system 100 (e.g., the processor 123 or the controller 130) continuously detects the load status of the power supply system 100.

In step S502, the power supply system 100 determines whether the load status is a peak load. If the load status is not a peak load but a normal load, the second power supply unit 120 will be maintained in standby mode.

If the load condition is a peak load, the power supply system 100 generates a trigger signal Sw in step S503. As described in the previous embodiment, the trigger signal Sw can be provided by the controller 130 to the processor 123 of the second power unit 120, or provided by the detection circuit 124 to the processor 123, or generated by the processor 123 based on the received detection signal Sd.

In step S504, in response to the trigger signal Sw, the second power supply unit 120 switches from the standby mode to the power supply mode. At this point, the processor 123 disables the first-stage converter 121 and controls the energy storage capacitor C21 to discharge in order to supply power to the power load PL.

In step S505, while the second power supply unit 120 is in power supply mode, the power supply system 100 (e.g., the processor 123 or the controller 130) continues to detect the load status of the power supply system 100 and determines whether the load status is still a peak load.

If the load status changes to a normal load, in step S506, the power supply system 100 generates a standby signal to switch the second power unit 120 from the power supply mode back to the standby mode. Similar to the generation of the trigger signal Sw, the standby signal can be provided by the controller 130 to the processor 123 of the second power unit 120, or by the detection circuit 124 to the processor 123, or generated by the processor 123 based on the received detection signal Sd.

When the second power supply unit 120 switches back to standby mode from power supply mode, the processor 123 controls the energy storage capacitor C21 to stop discharging and charges the energy storage capacitor C21 with power provided by the power supply PS. As previously described, in one embodiment, when charging the energy storage capacitor C21, the processor 123 may time a reset time before enabling the first-stage converter 121 in the second power supply unit 120 to charge the energy storage capacitor C21 with power provided by the power supply PS. In other embodiments, when charging the energy storage capacitor C21, the processor 123 may control the current value of the energy storage capacitor C21 to a set current value, and evenly charge the energy storage capacitor C21 during a subsequent charging period (e.g., multiple power cycles Tp).

By discharging the energy storage capacitor C21 in the backup second power unit 120, the power supply system 100 can directly replenish the required output power during peak loads without requiring additional current from the power supply PS. Consequently, the power supply system 100 will not generate current surges during peak loads, ensuring a stable power supply while preventing damage to internal components caused by current surges.

The various elements, method steps, or technical features in the aforementioned embodiments may be combined with each other and are not limited to the order of description or presentation in the figures in this disclosure.

Although the present disclosure has been described above in terms of implementation, it is not intended to limit the present disclosure. Anyone skilled in the art may make various modifications and improvements without departing from the spirit and scope of the present disclosure. Therefore, the scope of protection of the present disclosure shall be determined by the scope of the attached patent application.

S501-S506: Steps

Claims (20)

A power supply system includes: at least one first power supply unit coupled between a power supply and a power load to supply power to the power load; and a second power supply unit connected in parallel with the at least one first power supply unit and coupled between the power supply and the power load, wherein the second power supply unit includes: an energy storage capacitor; a first-stage converter coupled between the power supply and the energy storage capacitor; a second-stage converter coupled between the energy storage capacitor and the power load; and a processor coupled to the first-stage converter and the second-stage converter; when the second power supply unit is in a standby mode, the processor switches the second power supply unit to a power supply mode in response to a trigger signal; When the second power unit is in the power supply mode, the processor is configured to disable the first-stage converter, and the energy storage capacitor supplies power to the power load via the second-stage converter. The power supply system as described in claim 1, wherein before the processor receives the trigger signal, the processor is used to enable the first-stage converter and charge the energy storage capacitor with power provided by the supply power. The power supply system as described in claim 1, wherein when the energy storage capacitor supplies power to the power load through the second-stage converter and the processor receives a standby signal, the processor is used to control the energy storage capacitor to stop discharging so that the second power unit returns to the standby mode. The power supply system as described in claim 3, wherein when the second power supply unit resumes the standby mode, the processor is used to enable the first-stage converter again after a reset time to charge the energy storage capacitor using the power provided by the supply power. The power supply system as described in claim 3, wherein after the second power supply unit resumes the standby mode, the processor is used to charge the energy storage capacitor through the power provided by the supply power in subsequent multiple power cycles. The power supply system as described in claim 5, wherein in the subsequent power cycles, the second power unit charges the energy storage capacitor with a set current value. The power supply system as described in claim 1, wherein when the second power unit is in the standby mode, the energy storage capacitor stops discharging, and the second power unit does not supply power to the power load, or the power supply of the second power unit is less than a preset value. The power supply system of claim 1, wherein the second power unit further comprises: A detection circuit coupled to the processor and configured to detect at least one slew rate of the at least one first power unit and to determine whether the at least one slew rate exceeds a peak threshold. The power supply system as described in claim 1, wherein the trigger signal is generated based on an output current change or a load prediction signal of the at least one first power unit. The power supply system as described in claim 9 further includes: a controller coupled to the at least one first power unit, the second power unit and the power load, for obtaining the output current change of the at least one first power unit, or obtaining the load prediction signal to generate the trigger signal. A control method is provided for a power supply system, wherein the power supply system includes at least a first power unit and a second power unit, and the at least one first power unit is configured to supply power to an electrical load using power from a power supply. The control method comprises: detecting a load state of the power supply system; When the load state is determined to be a peak load, generating a trigger signal; and In response to the trigger signal, disabling a first-stage converter in the second power unit and controlling an energy storage capacitor in the second power unit to supply power to the electrical load, wherein the energy storage capacitor is coupled between the first-stage converter and a second-stage converter in the second power unit. The control method as described in claim 11 further includes: when it is determined that the load state does not belong to the peak load, enabling the first-stage converter and charging the energy storage capacitor through the power provided by the power supply. The control method as described in claim 11 further includes: when the energy storage capacitor supplies power to the power load and the second power unit receives a standby signal, controlling the energy storage capacitor to stop discharging so that the second power unit switches from a power supply mode to a standby mode. The control method of claim 13 further comprises: When the second power supply unit switches from the power supply mode to the standby mode, after a reset time, enabling the first-stage converter to charge the energy storage capacitor using the power provided by the power supply. The control method of claim 13 further comprises: When the second power unit switches from the power supply mode to the standby mode, charging the energy storage capacitor with power provided by the power supply during a plurality of subsequent power cycles. The control method of claim 15, wherein the method for charging the energy storage capacitor further comprises: In subsequent power cycles, charging the energy storage capacitor at a set current value. A control method as described in claim 13, wherein when the second power unit is in the standby mode, the energy storage capacitor stops discharging, and the second power unit does not supply power to the power load, or the power supply of the second power unit is less than a preset value. The control method of claim 11 further comprises: Detecting at least one slew rate of the at least one first power unit via a detection circuit; and Generating the trigger signal when the at least one slew rate exceeds a peak threshold. The control method as described in claim 11, wherein the trigger signal is generated based on an output current change or a load prediction signal of the at least one first power unit. The control method of claim 19 further comprises: obtaining the output current change of the at least one first power unit or the load prediction signal via a controller, wherein the controller is coupled to the at least one first power unit, the second power unit, and the power load.