Multi-terminal cooperative multi-stage direct connection power converter

Abstract

The invention discloses a multi-terminal cooperative multi-stage direct connection power converter, which comprises a plurality of stages of BOOST conversion units, each stage of BOOST conversion unit comprises a switching tube, an inductor, a fly-wheel diode and an auxiliary capacitor; wherein the inductors at the input ends of the BOOST conversion units are jointly connected with the positive electrode of a direct-current input power supply; the connection relation of the auxiliary capacitors at the output end is that the negative electrode of the nth-stage auxiliary capacitor is connected to the positive electrode of the (n-1) th-stage auxiliary capacitor, wherein n is an integer greater than 1; the negative electrode of the first-stage auxiliary capacitor is directly connected with the negative electrode of the direct-current input power supply; and the positive electrode of each stage of auxiliary capacitor and the negative electrode of the direct current input power supply form an independent conversion stage output end. According to the invention, multi-stage power parallel output can be realized, the multi-load requirement is met, and meanwhile, flexible distribution and dynamic adjustment of power transmission levels can be realized, so that the range and flexibility of power transmission are expanded.

Description

Technical Field

[0001] This invention relates to the field of power conversion technology, and more specifically to a multi-terminal collaborative multi-stage direct-connected power converter. Background Technology

[0002] In modern power electronic systems such as photovoltaic (PV) power generation, DC-DC power converters are the core components for energy conversion and regulation.

[0003] Currently, traditional photovoltaic systems still widely use single-stage converters based on topologies such as BOOST and BUCK. These traditional structures are simple, but they have inherent limitations: the switching devices are subjected to high current or voltage stress during the boost / buck process, leading to a decrease in efficiency; it is difficult to simultaneously and efficiently adapt to a wide range of input voltages and diverse load requirements; and they lack flexible multi-port output capabilities.

[0004] While multi-stage cascaded or parallel converter structures can expand voltage gain or distribute power to some extent, existing multi-stage solutions are typically complex, have high losses, and are difficult to control. Furthermore, most still adhere to the full-power processing paradigm, with each stage handling all power and failing to fully utilize the potential for partial power processing. Simultaneously, a single converter struggles to meet load demands under various load conditions, increasing investment costs.

[0005] Therefore, how to solve the above problems is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, in order to at least partially solve the above problems, the present invention provides a multi-terminal collaborative multi-stage direct-connect power converter, so as to achieve efficient, flexible, multi-port output power conversion through a multi-stage direct-connect structure.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A multi-terminal collaborative multi-stage direct-connect power converter includes multiple stages of BOOST conversion units; each stage of the BOOST conversion unit includes a switching transistor, an inductor, a freewheeling diode, and an auxiliary capacitor.

[0009] The connections of each component are as follows: the first terminal of all inductors is connected to the positive terminal of the DC input power supply; the second terminal of each inductor is connected to the drain of the corresponding switching transistor and the anode of the corresponding freewheeling diode; the source of each switching transistor is connected to the negative terminal of the DC input power supply; and the cathode of each freewheeling diode is connected to the positive terminal of the corresponding auxiliary capacitor. Simultaneously, the negative terminal of the nth stage auxiliary capacitor is connected to the positive terminal of the (n-1)th stage auxiliary capacitor, where n is an integer greater than 1. The negative terminal of the first stage auxiliary capacitor is directly connected to the negative terminal of the DC input power supply.

[0010] The positive terminal of each auxiliary capacitor and the negative terminal of the DC input power supply form an independent output terminal of the converter stage.

[0011] Furthermore, it also includes an input filter capacitor, the positive terminal of which is connected to the first terminal of all inductors and the negative terminal of the first-stage auxiliary capacitor, and the negative terminal of which is connected to the negative terminal of the DC input power supply.

[0012] Furthermore, a body diode and a parasitic capacitance are connected in parallel between the source and drain of each stage of the switching transistor.

[0013] Furthermore, the startup steps include:

[0014] First, drive the switching transistor of the m-th stage BOOST conversion unit to work, so that its corresponding auxiliary capacitor is charged to the first target voltage, where m is an integer not less than 0;

[0015] Subsequently, the switching transistor of the (m+1)th stage BOOST converter is driven to operate, charging the corresponding auxiliary capacitor; wherein, the input of the (m+1)th stage BOOST converter depends on the first target voltage output by the m-th stage BOOST converter.

[0016] This process continues until all levels of BOOST conversion units have started up sequentially from the lowest level to the highest level and entered steady-state operation.

[0017] Furthermore, charging the corresponding auxiliary capacitor includes:

[0018] When the switching transistor is turned on, the electrical energy of the DC input power supply is stored in the inductor; when the switching transistor is turned off, the inductor releases energy and charges the auxiliary capacitor through the freewheeling diode.

[0019] Furthermore, a controller is deployed to monitor the voltage or current at the output of at least one converter stage, generate corresponding drive signals, and independently control the switching state and duty cycle of the corresponding switching transistor to adjust the output voltage of the corresponding BOOST converter stage, thereby achieving closed-loop control.

[0020] Furthermore, when controlling the two-stage BOOST conversion unit, after the converter enters a steady state, the controller can be configured to select any of the following control modes for operation:

[0021] Interleaved control mode: The controller generates two drive signals, wherein the drive signal of the second BOOST conversion unit switch lags behind the drive signal of the first BOOST conversion unit switch by 180°.

[0022] Synchronous control mode: The controller generates two drive signals, and the drive signals of the first BOOST conversion unit switch and the second BOOST conversion unit switch are in phase.

[0023] Furthermore, the converter control method is as follows:

[0024] Monitor the voltage or current of the load;

[0025] Based on the monitoring results, the current flowing through each inductor is independently controlled by adjusting the duty cycle of the corresponding switching transistor. When the duty cycle D > 0.5, the circuit operates in continuous current mode, and when the duty cycle D < 0.5, the circuit operates in discontinuous current mode, thereby stabilizing the voltage at all output terminals.

[0026] As can be seen from the above technical solution, the present invention discloses a multi-terminal collaborative multi-stage direct-connected power converter, which can flexibly cope with various load demands, effectively improve the output efficiency of the converter, and save investment costs. Compared with the prior art, the specific beneficial effects include:

[0027] 1. By controlling the duty cycle of the feedback adjustment switch signal, different levels of power transmission are achieved, ensuring the stability of the output voltage. This enables flexible allocation and dynamic adjustment of power transmission levels, thereby effectively expanding the range and flexibility of power transmission and enabling the converter to achieve optimal performance under different operating conditions.

[0028] 2. By adopting an innovative capacitor series cascade method, the output voltages of multiple BOOST converters are superimposed, thereby greatly improving the overall boost ratio; at the same time, it can effectively avoid the extreme duty cycle required by traditional high-gain converters and significantly reduce the voltage stress on power switching devices.

[0029] 3. The multi-stage direct-connect power converter structure is only a series and parallel connection of components, which simplifies the control difficulty of the system and reduces the development and operation costs.

[0030] 4. By using a multi-stage direct-connection structure and a partial power handling strategy, the voltage and current stress on the switching devices is effectively reduced, and the overall efficiency and reliability of the system are improved. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the dual-end cooperative multi-stage direct-connect power converter topology provided in an embodiment of the present invention;

[0033] Figure 2This is a schematic diagram of the switching cycle of the first-stage BOOST conversion mode of the dual-end cooperative multi-stage direct-connected power converter topology provided in the embodiment of the present invention;

[0034] Figures 3a-3c This is a working mode diagram of the first-stage BOOST conversion mode of the dual-end cooperative multi-stage direct-connected power converter topology provided in the embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram of the switching cycle of the two-stage BOOST conversion mode of the dual-end cooperative multi-stage direct-connected power converter topology provided in the embodiment of the present invention;

[0036] Figures 5a-5c This is a working mode diagram of the two-stage BOOST conversion mode of the dual-end cooperative multi-stage direct-connected power converter topology provided in the embodiment of the present invention;

[0037] Figure 6 This is a control block diagram of a dual-end cooperative multi-stage direct-connected power converter topology system provided in an embodiment of the present invention. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0040] This invention discloses a multi-terminal coordinated multi-stage direct-connected power converter, including a multi-stage BOOST conversion unit; each stage of the BOOST conversion unit includes a switching transistor, an inductor, a freewheeling diode, and an auxiliary capacitor; wherein, a body diode and a parasitic capacitance are connected in parallel between the source and drain of each stage of the switching transistor.

[0041] Furthermore, the connection relationships of each device are as follows: the first terminal of all inductors is connected to the positive terminal of the DC input power supply; the second terminal of each inductor is connected to the drain of the corresponding switching transistor and the anode of the corresponding freewheeling diode; the source of each switching transistor is connected to the negative terminal of the DC input power supply; and the cathode of each freewheeling diode is connected to the positive terminal of the corresponding auxiliary capacitor. Simultaneously, the negative terminal of the nth stage auxiliary capacitor is connected to the positive terminal of the (n-1)th stage auxiliary capacitor, where n is an integer greater than 1; the negative terminal of the first stage auxiliary capacitor is directly connected to the negative terminal of the DC input power supply.

[0042] The positive terminal of each auxiliary capacitor and the negative terminal of the DC input power supply form an independent output terminal of the converter stage.

[0043] The converter in this invention has a simple structure, can flexibly cope with various load requirements, and can effectively improve the output efficiency of the converter.

[0044] In some implementations, traditional converters typically employ a full-power processing scheme, meaning that all energy drawn from the power supply must flow 100% through the power converter, undergoing voltage or current level transformation via switching devices before being delivered to the load. While this approach is technically mature, full-power processing results in all energy being subjected to switching losses, making it difficult to further improve system efficiency in high-power applications.

[0045] Therefore, to improve efficiency, this application proposes a partial power transfer strategy, in which the constant portion is transmitted through a direct connection channel without active switching conversion; only the portion of power that changes with operating conditions is dynamically adjusted and transformed. The partial power converter constructed in this way only processes a small portion of the total power, which can significantly reduce switching losses, magnetic component size, and system cost, thereby achieving higher overall efficiency.

[0046] In one specific implementation, an input filter capacitor is provided, the positive terminal of which is connected to the first terminal of all inductors and the negative terminal of the first-stage auxiliary capacitor, and the negative terminal of the input filter capacitor is connected to the negative terminal of the DC input power supply.

[0047] The electrical energy in the input filter capacitor does not need to undergo power conversion and can be directly used to power the load in conjunction with the auxiliary capacitor.

[0048] In one embodiment, the converter startup step of the present invention includes:

[0049] First, drive the switching transistor of the m-th stage BOOST conversion unit to work, so that its corresponding auxiliary capacitor is charged to the first target voltage, where m is an integer not less than 0;

[0050] Subsequently, the switching transistor of the (m+1)th stage BOOST converter is driven to operate, charging the corresponding auxiliary capacitor; wherein, the input of the (m+1)th stage BOOST converter depends on the first target voltage output by the m-th stage BOOST converter.

[0051] This process continues until all levels of BOOST conversion units have started up sequentially from the lowest level to the highest level and entered steady-state operation.

[0052] To further illustrate the implementation process of the converter in this application, a multi-stage direct-connected power converter including two-stage BOOST conversion units will be used as an example. See the attached document for details. Figure 1 .

[0053] Figure 1 The diagram shows a dual-terminal coordinated multi-stage direct-connect power converter. The first-stage BOOST converter unit includes a switching MOSFET Q1, a body diode D1, a parasitic capacitance C1, an auxiliary capacitor CS1, a freewheeling diode D3, and an inductor L1. The second-stage BOOST converter unit includes a switching MOSFET Q2, a body diode D2, a parasitic capacitance C2, an auxiliary capacitor CS2, a freewheeling diode D4, and an inductor L2. The first-stage and second-stage BOOST converter units output in parallel, with resistive loads Rload1 and Rload2 on the output sides, respectively. An input filter capacitor Cin is also included, which is connected in parallel with the DC power supply on the input side.

[0054] In this embodiment, the dual-end cooperative multi-stage direct-connect power converter includes the following two operating modes:

[0055] 1. First-stage BOOST conversion mode: Power is supplied from the power source and enters the filter capacitor C. in Then, by controlling the switching of MOSFET Q1, the current flows from inductor L1 to auxiliary capacitor C. S1 Flow, auxiliary capacitor C S1 When MOSFET Q1 is turned off, the inductor current charges it through the freewheeling diode D3, resulting in a positive voltage; the filter capacitor C... in To achieve stable input voltage;

[0056] 2. Two-stage BOOST conversion mode: Power is supplied by the input capacitor C. in The signal is transmitted via the switching of MOSFET Q2 to inductor L2 and auxiliary capacitor C. S2 Flow, auxiliary capacitor C S2 When MOSFET Q2 is turned off, the inductor current charges it through the freewheeling diode D4, resulting in a positive voltage; the output filter capacitor C... inThis is the input for both the first-stage and second-stage BOOST transformations. The auxiliary capacitor CS1 is the input for the second-stage BOOST transformation, i.e., the auxiliary capacitor C. S1 Auxiliary capacitor C S2 It can be used with the input capacitor C in The output ports are formed; the last two stages of BOOST conversion are output in parallel to supply power to the load, thereby realizing partial power transmission and multi-load requirements.

[0057] In this embodiment, the switching MOSFETs Q1 and Q2 can be controlled by interleaving or synchronous control. In interleaving control mode, the drive signal of Q2 lags behind the drive signal of Q1 by 180°. During the startup phase, Q1 turns on first, inductor L1 stores energy, and Q2 is in the off state. After half a cycle, Q1 turns off and Q2 turns on, and energy is transferred from inductor L1 to auxiliary capacitor C. S2 And on inductor L2; after steady state, since the whole system adopts closed-loop control, the duty cycle of its control signal can change according to the load change. When D<0.5, the circuit operates in discontinuous inductor current (DCM) mode, and when D>0.5, the circuit operates in continuous inductor current (CCM) mode. Stable output can also be obtained by using synchronous control.

[0058] Furthermore, the output modes of the first-level BOOST converter include the following operating modes:

[0059] like Figure 2 As shown, when the multi-stage direct-connect power converter is in the first-stage BOOST output mode, one switching cycle includes three operating modes:

[0060] In the [t0-t1] phase, such as Figure 3a As shown, at time t0, the switching MOSFET Q1 starts to conduct, the inductor current begins to build up, and the capacitor C... in The energy is transferred to inductor L1, and inductor L1 begins to store energy.

[0061] In the [t1-t2] phase, such as Figure 3b As shown, at time t1, MOSFET Q1 is turned off. Since the inductor current cannot change abruptly, the inductor current flows through the freewheeling diode D3 to the auxiliary capacitor C. S1 During charging, energy is released into capacitor C at this point. S1 During this process, the inductor current begins to decrease. At this point, the first stage of boost conversion is complete, realizing the transfer of energy from the power source to the capacitor C. S1 The transmission.

[0062] Phase [t0-t2], such as Figure 3c As shown, in this stage, the auxiliary capacitor C S1 With input capacitor C in The two voltage components superimposed together supply voltage to the load R.load1 It provides energy and enables partial power transmission.

[0063] The output modes of the second-level BOOST converter include the following operating modes:

[0064] like Figure 4 As shown, when the multi-stage direct-connect power converter is in the second-stage BOOST output mode, one switching cycle includes three operating modes:

[0065] In the [t0-t1] phase, such as Figure 5a As shown, at time t0, MOSFET Q2 starts to conduct, the inductor current begins to build up, and the capacitor C... in The energy is transferred from the inductor to the inductor L2, and the inductor L2 begins to store energy.

[0066] In the [t1-t2] phase, such as Figure 5b As shown, at time t1, MOSFET Q2 is turned off. Since the inductor current cannot change abruptly, the inductor current flows through the freewheeling diode D4 to the auxiliary capacitor C. S2 During charging, energy is released into capacitor C at this point. S2 During this process, the inductor current begins to decrease. At this point, the second-stage boost conversion is complete, realizing the transfer of energy from the power source to the capacitor C. S2 The transmission;

[0067] In the [t0-t2] phase, such as Figure 5c As shown, in this stage, the auxiliary capacitor C S1 Auxiliary capacitor C S2 and input capacitor C in The three voltage components superimposed together supply voltage to the load R. load2 It provides energy and enables partial power transmission.

[0068] To further optimize the above technical solution, a controller is deployed to monitor the voltage or current at the output of at least one conversion stage, generate corresponding drive signals, and independently control the switching state and duty cycle of the corresponding switching transistors to adjust the output voltage of the corresponding BOOST conversion stage, thereby achieving closed-loop control.

[0069] Specific reference Figure 6 First, the voltage across the load is sampled and compared with a given value. The error is then calculated and input to the PI controller. The PI controller generates a control signal proportional to the magnitude of the error to limit the amplitude and ensure that it does not exceed the allowable range, thus preventing the converter from being overloaded or damaged.

[0070] Furthermore, a fixed-frequency triangular wave signal is generated by a triangular wave generator as the carrier wave for pulse width modulation. Then, the limited control signal is compared with the triangular wave to generate a PWM signal. The larger the control signal, the larger the PWM duty cycle, thereby adjusting the on-time of the switching transistor and thus adjusting the output voltage.

[0071] In this application, the drive information controls the power switch, which affects the output voltage. The output voltage is sampled again and fed back to the PI controller to form a closed-loop control, continuously correcting the error and stabilizing the output voltage at the given value.

[0072] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0073] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A multi-terminal collaborative multi-stage direct-connected power converter, characterized in that, It includes a multi-stage BOOST conversion unit; each stage of the BOOST conversion unit includes a switching transistor, an inductor, a freewheeling diode and an auxiliary capacitor; The connections of each component are as follows: the first terminal of all inductors is connected to the positive terminal of the DC input power supply; the second terminal of each inductor is connected to the drain of the corresponding switching transistor and the anode of the corresponding freewheeling diode; the source of each switching transistor is connected to the negative terminal of the DC input power supply; and the cathode of each freewheeling diode is connected to the positive terminal of the corresponding auxiliary capacitor. Simultaneously, the negative terminal of the nth stage auxiliary capacitor is connected to the positive terminal of the (n-1)th stage auxiliary capacitor, where n is an integer greater than 1. The negative terminal of the first stage auxiliary capacitor is directly connected to the negative terminal of the DC input power supply. The positive terminal of each auxiliary capacitor and the negative terminal of the DC input power supply form an independent output terminal of the converter stage.

2. The multi-terminal coordinated multi-stage direct-connected power converter according to claim 1, characterized in that, It also includes an input filter capacitor, the positive terminal of which is connected to the first terminal of all inductors and the negative terminal of the first-stage auxiliary capacitor, and the negative terminal of which is connected to the negative terminal of the DC input power supply.

3. The multi-terminal coordinated multi-stage direct-connected power converter according to claim 1, characterized in that, A body diode and parasitic capacitance are connected in parallel between the source and drain of each stage of the switching transistor.

4. The multi-terminal coordinated multi-stage direct-connected power converter according to claim 1, characterized in that, The startup steps include: First, drive the switching transistor of the m-th stage BOOST conversion unit to work, so that its corresponding auxiliary capacitor is charged to the first target voltage, where m is an integer not less than 0; Subsequently, the switching transistor of the (m+1)th stage BOOST converter is driven to operate, charging the corresponding auxiliary capacitor; wherein, the input of the (m+1)th stage BOOST converter depends on the first target voltage output by the m-th stage BOOST converter. This process continues until all levels of BOOST conversion units have started up sequentially from the lowest level to the highest level and entered steady-state operation.

5. The multi-terminal coordinated multi-stage direct-connected power converter according to claim 4, characterized in that, Charging the corresponding auxiliary capacitor includes: When the switching transistor is turned on, the electrical energy of the DC input power supply is stored in the inductor; when the switching transistor is turned off, the inductor releases energy and charges the auxiliary capacitor through the freewheeling diode.

6. The multi-terminal coordinated multi-stage direct-connected power converter according to claim 1, characterized in that, A controller is deployed to monitor the voltage or current at the output of at least one converter stage, generate corresponding drive signals, and independently control the switching state and duty cycle of the corresponding switching transistor to adjust the output voltage of the corresponding BOOST converter stage, thereby achieving closed-loop control.

7. The multi-terminal coordinated multi-stage direct-connected power converter according to claim 6, characterized in that, When controlling the two-stage BOOST converter unit, after the converter enters a steady state, the controller can be configured to operate in any of the following control modes: Interleaved control mode: The controller generates two drive signals, wherein the drive signal of the second BOOST conversion unit switch lags behind the drive signal of the first BOOST conversion unit switch by 180°. Synchronous control mode: The controller generates two drive signals, and the drive signals of the first BOOST conversion unit switch and the second BOOST conversion unit switch are in phase.

8. The multi-terminal coordinated multi-stage direct-connected power converter according to claim 6, characterized in that, The converter control method is as follows: Monitor the voltage or current of the load; Based on the monitoring results, the current flowing through each inductor is independently controlled by adjusting the duty cycle of the corresponding switching transistor. When the duty cycle D > 0.5, the circuit operates in continuous current mode, and when the duty cycle D < 0.5, the circuit operates in discontinuous current mode, thereby stabilizing the voltage at all output terminals.

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