Power conversion system with ripple injection and power conversion control method

Abstract

A power conversion system with ripple injection includes an AC-DC converter, a voltage regulator, a DC-DC converter, at least one load, and a first control unit. The AC-DC converter has a first input side and a first output side. The first input side receives AC power and provides input power. The voltage regulator is coupled to the first output side, provides a DC link, and receives a portion of the input power as energy storage power. The at least one DC-DC converter has a second input side and a second output side. The second input side is coupled to the DC link and receives another portion of the input power as output power. The at least one load is coupled to the second output side and receives the output power. The first control unit is coupled to the DC link, the at least one DC-DC converter, and the at least one load. Based on the ripple magnitude of the input power, the first control unit controls the at least one DC-DC converter to adjust the ripple magnitude of the output power, performing ripple injection operation on the at least one load.

Description

Technical Field

[0001] This invention relates to a power conversion system and a power conversion control method, and more particularly to a power conversion system and a power conversion control method with ripple injection. Background Technology

[0002] The input power of a power conversion system includes a DC component and a ripple component. Part of this flows into the capacitors of the DC-Link, and the other part flows into the subsequent battery charger. In traditional methods, the battery charger charges the battery with a constant current, where the output power is constant. This consumes only the DC component of the input power, while all the ripple (AC) component of the input power flows into the capacitors of the DC-Link, resulting in large capacitor voltage ripple and potentially damaging the capacitors. Furthermore, if grid anomalies cause fluctuations in input power that generate excessive voltage ripple on the DC-Link, it can easily trigger overvoltage protection, potentially causing the battery charging (swapping) station to trip.

[0003] Therefore, how to design a power conversion system and power conversion control method, especially a power conversion system and power conversion control method with ripple injection, to solve the problems and technical bottlenecks of the existing technology, is an important research topic for the inventors of this case. Summary of the Invention

[0004] One objective of this invention is to provide a power conversion system with ripple injection, thereby solving the problems of the prior art.

[0005] To achieve the aforementioned objectives, the power conversion system with ripple injection proposed in this invention includes an AC-DC conversion unit, a voltage regulator unit, at least one DC-DC conversion unit, at least one load, and a first control unit. The AC-DC conversion unit has a first input side and a first output side. The first input side is coupled to an AC power source to provide input power. The voltage regulator unit is coupled to the first output side, providing a DC link and receiving a portion of the input power as energy storage power. Each DC-DC conversion unit has a second input side and a second output side. The second input side is coupled to the DC link and receives another portion of the input power as output power. At least one load is coupled to the second output side, correspondingly receiving power from the received output power of the at least one DC-DC conversion unit. The first control unit is coupled to the DC link, the DC-DC conversion units, and the at least one load. Based on the ripple magnitude of the input power, the first control unit controls the at least one DC-DC conversion unit to adjust the ripple magnitude of the output power, performing ripple injection operation on the at least one load.

[0006] In one embodiment, the first control unit initiates a ripple injection operation when it determines that the DC link voltage is greater than or equal to a threshold voltage.

[0007] In one embodiment, at least one DC-DC converter unit collectively and evenly regulates the ripple magnitude of the output power.

[0008] In one embodiment, at least one DC-DC converter operates at a constant current, and a first control unit controls at least one DC-DC converter to perform current ripple injection operation.

[0009] In one embodiment, at least one DC-DC converter operates at a constant voltage, and a first control unit controls the at least one DC-DC converter to perform voltage ripple injection operation.

[0010] In one embodiment, the first control unit determines the power ripple phase angle input to the DC link and initiates a ripple injection operation based on the matching power ripple phase angle.

[0011] In one embodiment, the power conversion system with ripple injection further includes a second control unit. The second control unit is coupled to the AC-DC conversion unit and the DC link, and receives AC power. When the AC power is a three-phase AC power supply, the second control unit controls the three-phase currents flowing into the AC input current of the AC-DC conversion unit to be balanced and evenly distributed.

[0012] In one embodiment, the AC-DC conversion unit is a power factor corrector.

[0013] In one embodiment, the voltage regulator unit is a capacitor.

[0014] In one embodiment, at least one DC-DC conversion unit is a battery charger, and at least one load is a DC battery.

[0015] The proposed power conversion system with ripple injection achieves the following technical benefits: 1. Ripple injection control compensation in the later stage can prevent damage to the voltage regulator unit (e.g., capacitor) or activate the protection mechanism to protect the capacitor, thus improving the lifespan of the DC link capacitor and reducing maintenance circuit costs; 2. Ripple compensation in the later stage can optimize the three-phase current balance of the front-end PFC circuit, thereby reducing the electromagnetic interference (EMI) effect of the input current and also reducing the damage to the power grid caused by current imbalance.

[0016] Another objective of this invention is to provide a power conversion control method to solve the problems of the prior art.

[0017] To achieve the aforementioned objectives, the power conversion control method proposed in this invention is operated through a power conversion system. The power conversion system includes an AC-DC conversion unit, a voltage regulator unit, at least one DC-DC conversion unit, at least one load, and a first control unit. The AC-DC conversion unit receives AC power and provides input power. The voltage regulator unit provides a DC link and receives a portion of the input power as energy storage power. Each DC-DC conversion unit is coupled to the DC link and receives another portion of the input power as output power. The at least one load correspondingly receives the output power (p) of at least one DC-DC conversion unit. out The power conversion control method includes the following steps: (a) a first control unit obtains the DC link voltage of the DC link; (b) the first control unit selects to perform load control or ripple injection control and load control based on the threshold voltage and the DC link voltage; (c) when the first control unit selects to perform ripple injection control and load control, the first control unit forms a first DC-to-DC control command based on the load demand information and the DC link voltage, wherein the load demand information corresponds to the power required by at least one load to be obtained from at least one DC-to-DC conversion unit; (d) when the first control unit selects to perform only load control, the first control unit forms a second DC-to-DC control command based on the load demand information; (e) at least one DC-to-DC conversion unit obtains power from the self-regulating unit according to the first DC-to-DC control command or the second DC-to-DC control command provided by the first control unit, and performs DC power conversion to supply the power required by at least one load.

[0018] In one embodiment, in step (b), when the first control unit determines that the corresponding DC link voltage is greater than or equal to the threshold voltage, it initiates ripple injection control.

[0019] In one embodiment, at least one DC-DC converter unit collectively and evenly regulates the ripple magnitude of the output power.

[0020] In one embodiment, at least one DC-DC converter operates at a constant current, and a first control unit controls the at least one DC-DC converter to perform current ripple injection control.

[0021] In one embodiment, at least one DC-DC converter operates at a constant voltage, and a first control unit controls the at least one DC-DC converter to perform voltage ripple injection control.

[0022] In one embodiment, the first control unit determines the power ripple phase angle input to the DC link and initiates ripple injection control based on the matching power ripple phase angle.

[0023] In one embodiment, the power conversion system further includes a second control unit. The second control unit is coupled to the AC-DC conversion unit and the DC link, and receives AC power. The power conversion control method includes the step of: (f) when the AC power is a three-phase AC power, the second control unit controls the three-phase currents of the AC input current flowing into the AC-DC conversion unit to be balanced and equalized.

[0024] The proposed power conversion control method achieves the following technical benefits: 1. By using ripple injection control compensation in the subsequent stage, damage to the voltage regulator unit (e.g., capacitor) can be avoided, or the protection mechanism can be activated to protect the capacitor. This can improve the lifespan of the DC link capacitor and reduce maintenance circuit costs. 2. By using ripple compensation in the subsequent stage, the three-phase current balance of the preceding stage PFC circuit can be optimized, thereby reducing the electromagnetic interference (EMI) effect of the input current. On the one hand, it can also reduce the damage to the power grid caused by current imbalance.

[0025] To gain a deeper understanding of the techniques, means, and effects employed by this invention to achieve its intended purpose, please refer to the following detailed description and accompanying drawings. It is believed that the purpose, features, and characteristics of this invention can be understood in a thorough and specific manner from these drawings. However, the drawings are provided for reference and illustration only and are not intended to limit the scope of this invention. Attached Figure Description

[0026] Figure 1 : This is a block diagram of a first embodiment of the power conversion system with ripple injection of the present invention;

[0027] Figure 2 : This is a block diagram of a second embodiment of the power conversion system with ripple injection of the present invention;

[0028] Figure 3 : This is a block diagram of the power conversion system of the present invention, which is used in a battery charging station.

[0029] Figures 4A-4C : This is a waveform diagram illustrating the ripple injection control judgment of the present invention;

[0030] Figure 5 This is a flowchart of the power conversion control method of the present invention.

[0031] Explanation of icon numbers:

[0032] 10: AC-DC conversion unit

[0033] 20: Voltage Regulator Unit

[0034] 30: DC-DC conversion unit

[0035] 40: Load

[0036] 50: First control unit

[0037] 60: Second control unit

[0038] V AC AC power supply

[0039] p in Input power

[0040] p out Output power

[0041] p c Energy storage capacity

[0042] L DC DC link

[0043] v dc DC link voltage

[0044] i dc DC link input current

[0045] v dc,th Threshold voltage

[0046] OVP: Overvoltage protection voltage

[0047] S11~S15: Steps Detailed Implementation

[0048] The technical content and detailed description of the present invention are explained below with reference to the accompanying drawings.

[0049] Please see Figure 1 The diagram shown is a block diagram of a first embodiment of the power conversion system with ripple injection according to the present invention. The power conversion system with ripple injection of the present invention mainly includes an AC-DC conversion unit 10, a voltage regulator unit 20, at least one DC-DC conversion unit 30, at least one load 40, and a first control unit 50. The number of at least one load 40 corresponds to the number of at least one DC-DC conversion unit 30.

[0050] The AC-DC converter 10 has a first input side and a first output side. The first input side receives AC power V. AC Provide input power p in In one application embodiment, the AC power supply V AC It can provide AC power to the power grid, and the AC power supply V AC It can be a three-phase AC power supply or a single-phase AC power supply, as will be explained later. Incidentally, the input power p... inIt is uncontrollable and related to the power supply of the power grid. In addition, in the power conversion application of the present invention, the AC-DC conversion unit 10 serves as a power factor correction unit (or power factor corrector, power factor correction circuit) for power factor correction (PFC).

[0051] The voltage regulator unit 20 is coupled to the first output side of the AC-DC converter unit 10 to provide DC link L. DC (or DC bus), and receives a portion of the input power p in For energy storage power p c This means a portion of the input power p in Energy is stored in the voltage regulator unit 20. In one embodiment, the voltage regulator unit 20 is used as a capacitor for voltage regulation and energy storage.

[0052] Each DC-DC converter 30 has a second input side and a second output side. The second input side is coupled to a DC link L. DC Receive another part of the input power p in For the output power p out In one embodiment, the DC-DC conversion unit 30 is a battery charger, but the invention is not limited thereto. Incidentally, compared to uncontrollable input power p... in Output power p out It is controllable. Because the input power p in Equal to energy storage power p c With output power p out The sum of, therefore, by controlling the output power p out The size of the energy storage capacity p can be adjusted accordingly. c The size, i.e., the energy storage power p c =Input power p in - Output power p out In other words, in order to control the output power p out Then the input power p must be known. in The quantity of input power p is determined by the present invention. in The size of, and further based on the detected input power p in The ripple injection operation is performed based on the ripple size, which will be explained later.

[0053] Based on the aforementioned power conversion system of the present invention, wherein the input power p in It contains ripple components, and when it passes through the voltage regulator unit 20, the input power p in The allocated energy storage power p c With output power p outThese also correspond to components with ripple effects. To achieve better ripple injection compensation, if the output power p is controlled... out The ripple component carried is as close as possible to the input power p. in The ripple component it carries makes the energy storage power p c The ripple component carried can be relatively small, so that the voltage regulator unit 20 is minimally affected by the ripple component, thereby protecting the voltage regulator unit 20 or reducing its loss rate.

[0054] At least one load 40 is coupled to the second output side of the DC-DC converter 30, and correspondingly receives the output power p of at least the DC-DC converter 30. out The power supply. In one embodiment, corresponding to the DC-DC conversion unit 30 is a battery charger, the at least one load 40 is a DC battery (charged by the battery charger), and if there is a plurality of them, the DC batteries are connected in parallel.

[0055] The first control unit 50 is coupled to the DC link L DC At least one DC-DC converter unit 30 and at least one load 40. The DC link L is detected. DC voltage v dc (i.e., across the DC link L) DC The voltage on the DC link and the input current i dc (i.e., flowing into DC link L) DC The current), and by calculating the product of the two, the (detected) input power p can be determined. in The magnitude, i.e., the input power p in =Voltage v dc ×current i dc Among them, the input power p in The calculation can be performed directly within the first control unit 50, or the calculation can be performed by an external computing unit and the result of the power calculation can be provided to the first control unit 50. Therefore, the first control unit 50 calculates the power based on the input power p. in The ripple magnitude, i.e., the input power p in The magnitude of the AC component determines the ripple injection operation of the DC-DC converter 30 onto at least one load 40. Therefore, the first control unit 50 first determines the ripple injection operation based on the input power p. in The ripple size determines whether to initiate (execute) the ripple injection operation. If the ripple injection operation needs to be executed, the amount of ripple power to be injected is then determined, as explained below.

[0056] Output power p out Output power including DC component Output power of AC component The output power of the DC component Power is supplied to at least one load 40, while the output power of the AC component is... Used to provide compensation for ripple injection.

[0057] Furthermore, due to the output power of the AC component It can be viewed as a sine wave, therefore its magnitude can vary with positive and negative values. Therefore, the first control unit 50 needs to further determine the input to the DC link L. DC Input power p in The phase angle of the ripple component allows ripple injection to be initiated based on the matching power ripple phase angle. In other words, if there is no input power p in By determining the phase angle of the ripple component and initiating ripple injection control under appropriate phase angle conditions, the energy storage power p will be increased. c Increase (e.g., when the input power p) in Controlled output power p (positive value) out When it is negative, it will cause the energy storage power p c (If the voltage is increased), the voltage regulator unit 20 will be damaged by ripple components, which conflicts with the spirit of the present invention to protect it. Therefore, starting ripple injection control under a suitable phase angle relationship will optimize the effect of ripple injection control.

[0058] Please see Figure 2 The diagram shown is a block diagram of a second embodiment of the power conversion system with ripple injection of the present invention. The power conversion system with ripple injection of the present invention further includes a second control unit 60. The second control unit 60 is coupled to the AC-DC conversion unit 10 and the DC link L. DC Receive AC power V AC AC power supply V AC When the power supply is a three-phase AC power source, the second control unit 60 controls the three-phase currents flowing into the AC-DC conversion unit 10 to be balanced and equalized. Therefore, by controlling the three-phase currents to be equal, the electromagnetic interference (EMI) effect of the input current can be reduced, and the damage to the power grid caused by current imbalance can also be minimized. If the AC power supply V... AC If it is a single-phase AC power supply, then the second control unit 60 is not required to perform current averaging control.

[0059] Please see Figure 3 As shown, it is a block diagram of the power conversion system of the present invention, which is used as a battery charging station. Figure 3 One portion shown (i.e., the portion involving the three-phase PFC) is used for balancing and sharing the three-phase current that controls the AC input current flowing into the AC-DC conversion unit 10, while the other portion (i.e., the portion involving the battery charger) is used for ripple injection compensation control.

[0060] In the three-phase PFC section: The three-phase voltage at the grid and mains terminals is detected. ), and use amplitude detection to calculate the amplitude of the three-phase voltage ( The phase angle of the power grid is obtained by using a phase-locked loop to lock the grid voltage. ). Detecting DC link voltage ( The average value of the three-phase voltage is calculated using the average voltage calculation. Command to generate appropriate DC power using DC regulation ( To stabilize the average value of the three-phase voltage ( Using DC power commands ( ), grid voltage amplitude ( ), and grid phase angle ( ) is used as input, and the current command is calculated using current balance control. This ensures that the three-phase currents are the same.

[0061] Detecting the three-phase current input to the power grid ( ) as feedback, with current command ( The feedback value is subtracted and input to the PID control for error amplification feedback control. The control signal is transmitted to the PWM module and amplified by the driver to drive the three-phase PFC circuit. At this time, the PFC will draw appropriate power from the grid to compensate for the energy required by the battery charger to charge the DC battery, thereby stabilizing the average voltage of the DC-Link.

[0062] In the battery charger section: This battery charging (swapping) station has n battery chargers and n rechargeable batteries. Each battery charger is a buck-type circuit, implemented using a buck converter. The voltage at the battery terminals is detected. ) and charging current ( To understand the status of the xth rechargeable battery, a constant current command is used to determine the magnitude of the constant current charging current.

[0063] The charging current command provided by the constant current command ( ), and the magnitude of the ripple current provided by the host (main controller, host) terminal ( ), phase angle ( The final charging current command is determined by the total current command. ). Charge current command ( ) and feedback charging current ( The difference is subtracted and sent to the PID control for error amplification. The control signal is then sent to the PWM module, where it is amplified to drive the buck converter (step-down converter) to output an appropriate charging current to charge the battery.

[0064] The host (main controller, host) detects the DC link voltage. ) and the current injected into the DC-Link by PFC ( ), and use power calculation to calculate its power ( The phase angle of the power ripple is calculated using power ripple phase calculation. Set the phase angle of the ripple current. The phase angle of the power ripple () Similarly, in this way, the battery charger can effectively transfer the power ripple injected into the DC-Link to the subsequent stage by injecting ripple current, thereby reducing the DC-Link voltage ripple.

[0065] The phase angle of the ripple current is converted using a digital-to-analog converter. Transmitted to each battery charger. Detect DC-DC link voltage ( ) and use ripple calculations to determine the magnitude of its voltage ripple ( Set the threshold for the DC link voltage. ), and use the voltage ripple command to calculate the appropriate voltage ripple magnitude ( ). The voltage ripple size ( ) and voltage ripple magnitude ( Subtracting the two, we get the error () ).

[0066] In the current ripple command, if the error ( A negative value indicates that the DC link voltage has not yet exceeded the threshold. At this time, there is no need to reduce the ripple voltage, so the magnitude of the ripple current ( Set the error to 0. A positive value indicates excessive voltage ripple, causing the DC link voltage to exceed the threshold. At this point, a PID controller will be used to control the error. Magnify to obtain the desired result. This allows the DC link voltage to be below the threshold ( ).

[0067] Because the battery charger charges the battery with a constant current, the ripple current cannot be too large. Therefore, it utilizes... With limitation, for Set an upper limit ( When calculated Greater than Then the final ripple current command will be limited to Finally, through communication... It is then sent to each battery charger.

[0068] See also Figures 4A-4C This is a waveform diagram for the ripple injection control judgment of the present invention. Figure 4A The voltage v shown dc For the DC link L DC The magnitude of the voltage ripple. In this embodiment, the voltage v dc Compared with the overvoltage protection voltage OVP, once the voltage v dc Reaching or exceeding the overvoltage protection voltage OVP will trigger overvoltage protection, causing the system to shut down. One embodiment of this invention for determining the timing of ripple injection can use voltage v... dc With threshold voltage v dc,th Comparison: When voltage v dc Greater than or equal to the threshold voltage v dc,th When the voltage is low, ripple injection compensation is activated; otherwise, if the voltage is low... dc Less than the threshold voltage v dc,th When this happens, ripple injection compensation stops. (Coordination) Figure 4B and Figure 4C As shown, when the voltage v dc Greater than or equal to the threshold voltage v dc,th At that time, ripple injection compensation is activated, therefore the voltage v dc It will gradually decrease, meaning the voltage v dc voltage greater than the threshold voltage v dc,th The smaller the part (e.g.) Figure 4B (As shown). At this time, due to the voltage v dc Still greater than or equal to the threshold voltage v dc,th Therefore, the ripple injection compensation operation continues until the voltage v dc Less than the threshold voltage v dc,th When this happens, ripple injection compensation is stopped (e.g.) Figure 4C (As shown).

[0069] Taking the application of a battery charger (i.e., at least one DC-DC converter 30) and a DC battery (i.e., at least one load 40) as an example, the number of battery chargers and DC batteries is usually multiple. Therefore, in ripple injection control, these DC-DC converters 30 collectively and evenly regulate the output power p. out The magnitude of the ripple. Furthermore, since the realization of ripple injection compensation is related to the conversion power that the DC-DC converter 30 can provide (i.e., ripple injection compensation is limited by the maximum output power of each DC-DC converter 30), ripple injection compensation performed under the limitation of the maximum output power of the DC-DC converter 30 can be continuously performed, as long as the voltage v is ensured. dc The system will not reach or exceed the overvoltage protection voltage (OVP) to prevent system shutdown.

[0070] Incidentally, for power supply applications with different load types, if at least the DC-DC converter 30 operates at a constant current, the first control unit 50 controls the at least DC-DC converter 30 to perform current ripple injection control. Furthermore, if at least the DC-DC converter 30 operates at a constant voltage, the first control unit 50 controls the at least DC-DC converter 30 to perform voltage ripple injection control. Therefore, the ripple injection compensation control provided by this invention can include both current ripple injection compensation control and voltage ripple injection compensation control, depending on the load type of the power supply.

[0071] Please see Figure 5 The diagram shows a flowchart of the power conversion control method of the present invention. The power conversion control method of the present invention is operated by a power conversion system. The main architecture of the power conversion system can be found above and will not be repeated here. The power conversion control method includes the following steps: First, the first control unit obtains the DC link voltage of the DC link (S11). Then, the first control unit selects to perform load control or ripple injection control and load control based on the threshold voltage and the DC link voltage (S12). If the first control unit selects only to perform load control, ripple injection control is not performed, which is the power conversion performed by the power conversion system to supply power to at least one load 40. If the first control unit selects to perform both ripple injection control and load control simultaneously, it means that in addition to performing power conversion for supplying power to at least one load 40, the power conversion system also performs ripple injection control for the protection provided by the voltage regulator unit 20.

[0072] When the first control unit 50 selects to execute ripple injection control and load control, the first control unit 50 generates a first DC-to-DC control command based on the load demand information provided by at least one load 40 (e.g., the power supply required by at least one load 40) and the DC link voltage. The load demand information corresponds to the power required by at least one load 40 to be obtained from at least one DC-to-DC conversion unit 30 (S13).

[0073] When the first control unit 50 selects to perform only load control, the first control unit 50 generates a second DC-to-DC control command based on the load demand information (S14).

[0074] Finally, at least one DC-DC conversion unit 30 obtains power from the self-regulating unit 20 according to the first DC-to-DC control command or the second DC-to-DC control command provided by the first control unit 50, and performs DC power conversion to supply the power required by at least one load 40 (S15).

[0075] In summary, the present invention has the following features and advantages:

[0076] 1. Ripple injection control compensation in the subsequent stage can prevent damage to the voltage regulator unit (such as capacitor) or activate the protection mechanism to protect the capacitor, thus improving the life of the DC link capacitor and reducing maintenance circuit costs.

[0077] 2. By using ripple compensation in the subsequent stage, the three-phase current balance of the preceding PFC circuit can be optimized, thereby reducing the electromagnetic interference (EMI) effect of the input current. This can also reduce the damage to the power grid caused by current imbalance.

[0078] The above description is merely a detailed description and accompanying drawings of preferred embodiments of the present invention. However, the features of the present invention are not limited thereto and are not intended to limit the present invention. The scope of the present invention should be determined by the following claims. All embodiments that conform to the spirit of the claims and similar variations thereof should be included in the scope of the present invention. Any variations or modifications that can be easily conceived by those skilled in the art within the field of the present invention can be covered by the following claims.

Claims

1. A power conversion system with ripple injection, comprising: An AC-DC converter unit has a first input side and a first output side, wherein the first input side receives an AC power supply and provides an input power; A voltage regulator unit is coupled to the first output side, provides a DC link, and receives a portion of the input power as a stored energy power. At least one DC-DC converter unit, each of the DC-DC converter units having a second input side and a second output side, the second input side being coupled to the DC link and receiving another portion of the input power as an output power; At least one load, coupled to the second output side, correspondingly receives power from the output power of the at least one DC-DC converter unit; and A first control unit is coupled to the DC link, the at least one DC-DC converter unit, and the at least one load; wherein The first control unit controls the at least one DC-DC converter in the subsequent stage to adjust the ripple magnitude of the output power according to the ripple magnitude of the input power, and performs ripple injection operation on the at least one load; wherein the ripple component carried by the output power is close to the ripple component carried by the input power.

2. The power conversion system with ripple injection according to claim 1, wherein the first control unit initiates the ripple injection operation when it determines that the DC link voltage is greater than or equal to the threshold voltage.

3. The power conversion system with ripple injection according to claim 2, wherein the at least one DC-DC conversion unit jointly and evenly regulates the ripple magnitude of the output power.

4. The power conversion system with ripple injection according to claim 1, wherein the at least DC-DC conversion unit operates at constant current, and the first control unit controls the at least DC-DC conversion unit to perform current ripple injection operation.

5. The power conversion system with ripple injection according to claim 1, wherein the at least DC-DC conversion unit operates at a constant voltage, and the first control unit controls the at least DC-DC conversion unit to perform voltage ripple injection operation.

6. The power conversion system with ripple injection according to claim 1, wherein the first control unit determines the power ripple phase angle input to the DC link and initiates the ripple injection operation according to the matching power ripple phase angle.

7. The power conversion system with ripple injection according to claim 1, further comprising: The second control unit is coupled to the AC-DC conversion unit and the DC link, and receives the AC power supply. wherein When the AC power supply is a three-phase AC power supply, the second control unit controls the three-phase current of the AC input current flowing into the AC-DC conversion unit to be balanced and equalized.

8. The power conversion system with ripple injection according to claim 1, wherein the AC-DC conversion unit is a power factor corrector.

9. The power conversion system with ripple injection according to claim 1, wherein the voltage regulation unit is a capacitor.

10. The power conversion system with ripple injection according to claim 1, wherein the at least one DC-DC conversion unit is a battery charger and the at least one load is a DC battery.

11. A power conversion control method, operated by a power conversion system, wherein the power conversion system comprises: An AC-DC converter unit receives AC power and provides input power. The voltage regulator unit provides a DC link and receives a portion of the input power as energy storage power. At least one DC-DC converter unit, each of the DC-DC converter units being coupled to the DC link, receiving another portion of the input power as output power; At least one load correspondingly receives power from the output power of the at least one DC-DC conversion unit; as well as The first control unit controls the at least one DC-DC converter in the subsequent stage to adjust the ripple magnitude of the output power according to the ripple magnitude of the input power, and performs ripple injection operation on the at least one load; wherein the ripple component carried by the output power is close to the ripple component carried by the input power. The power conversion control method includes the following steps: (a) The first control unit obtains the DC link voltage of the DC link; (b) The first control unit selects to perform load control or ripple injection control and load control based on the threshold voltage and the DC link voltage. (c) When the first control unit selects to execute the ripple injection control and the load control, the first control unit forms a first DC-to-DC control command based on the load demand information and the DC link voltage, wherein the load demand information corresponds to the power required by the at least one load to be obtained from the at least one DC-to-DC conversion unit. (d) When the first control unit selects to execute only the load control, the first control unit generates a second DC-to-DC control command based on the load demand information; and (e) The at least one DC-DC conversion unit obtains power from the voltage regulator unit according to the first DC-to-DC control command or the second DC-to-DC control command provided by the first control unit, and performs DC power conversion to supply the power required by the at least one load.

12. The power conversion control method according to claim 11, wherein in step (b), when the first control unit determines that the corresponding DC link voltage is greater than or equal to the threshold voltage, the ripple injection control is initiated.

13. The power conversion control method according to claim 12, wherein the at least one DC-DC conversion unit jointly and evenly adjusts the ripple magnitude of the output power.

14. The power conversion control method according to claim 11, wherein the at least DC-DC conversion unit operates at a constant current, and the first control unit controls the at least DC-DC conversion unit to perform current ripple injection control.

15. The power conversion control method according to claim 11, wherein the at least DC-DC conversion unit operates at a constant voltage, and the first control unit controls the at least DC-DC conversion unit to perform voltage ripple injection control.

16. The power conversion control method according to claim 11, wherein the first control unit determines the power ripple phase angle input to the DC link, and initiates the ripple injection control according to the matching power ripple phase angle.

17. The power conversion control method according to claim 11, wherein the power conversion system further comprises: The second control unit is coupled to the AC-DC conversion unit and the DC link, and receives the AC power supply. wherein The power conversion control method includes the following steps: (f) When the AC power supply is a three-phase AC power supply, the second control unit controls the three-phase current of the AC input current flowing into the AC-DC conversion unit to be balanced and equalized.

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