A single-stage multi-path dc access converter and a control method thereof

Abstract

The application provides a single-stage multi-path DC access converter and a control method thereof. In the single-stage multi-path DC access converter, AC sides of each DC side conversion circuit are connected in parallel to a primary winding of a transformer through corresponding impedance elements, the impedance elements can be used to realize power decoupling between the DC side conversion circuits, and thus the energy input or output by multiple DC side conversion circuits can be collectively processed by using one transformer to realize multi-path DC access. Moreover, each DC side conversion circuit is used to realize AC / DC conversion, and the turns ratio of the primary and secondary windings of the transformer can realize corresponding voltage transformation of the primary and secondary windings. The AC side conversion circuit connected to the secondary winding of the transformer can realize AC frequency conversion, and thus single-stage conversion can be realized. Therefore, the single-stage multi-path DC access converter can realize multi-path DC access in the form of single-stage conversion, and thus the conversion efficiency is improved and the cost is reduced.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a single-stage multi-channel DC-DC converter and its control method. Background Technology

[0002] Existing inverters typically employ a two-stage isolated converter, where the DC side of the subsequent DC / AC converter can be easily connected to multiple preceding DC / DC converters (such as...) via a DC bus. Figure 1 As shown in the figure, this enables multiple inputs and improves the overall conversion power.

[0003] However, two-stage isolation converters are complex in structure and inefficient, unlike single-stage high-frequency isolation converters which are simpler and more efficient. Therefore, single-stage high-frequency isolation converters have a wide range of applications in photovoltaic power generation, fuel cell power generation, and other scenarios.

[0004] However, unlike Figure 1 The two-stage isolation converter shown is a single-stage isolation converter without an intermediate bus, which makes it difficult to implement multiple inputs. Therefore, it cannot achieve the high efficiency and low cost of a multi-input converter, which limits the application of single-stage isolation converters to a certain extent. Summary of the Invention

[0005] In view of this, this application provides a single-stage multi-channel DC-DC converter and its control method to achieve multi-channel DC access, improve efficiency and reduce cost.

[0006] To achieve the above objectives, this application provides the following technical solution:

[0007] The first aspect of this application provides a single-stage multi-channel DC-DC converter, comprising: a transformer, an AC-side conversion circuit, at least two DC-side conversion circuits, and corresponding impedance elements thereof; wherein...

[0008] The AC side of each DC-side conversion circuit is connected in parallel to the primary winding of the transformer through its corresponding impedance element.

[0009] The secondary winding of the transformer is connected to the first side of the AC conversion circuit;

[0010] Each of the DC-side conversion circuits is used to invert the DC power it receives, or to rectify the AC power it receives.

[0011] Each of the impedance elements is used to achieve power decoupling between each of the DC-side conversion circuits;

[0012] The AC-side conversion circuit is used for AC frequency conversion.

[0013] Optionally, the impedance element includes: an inductor, or an inductor and a capacitor.

[0014] Optionally, the transformer is a single-phase transformer or a three-phase transformer.

[0015] Optionally, the primary windings of each phase of the three-phase transformer are connected at the same-name terminals to the corresponding phases of the AC side of the DC-side conversion circuit through the corresponding impedance elements, and their other ends are all connected to reference ground.

[0016] Each phase secondary winding of the three-phase transformer is connected at both ends to the corresponding phase on the first side of the AC-side conversion circuit, and the middle taps are connected.

[0017] Optionally, when the transformer is a single-phase transformer, the DC-side conversion circuit is a half-bridge circuit or a full-bridge circuit;

[0018] When the transformer is a three-phase transformer, the DC-side conversion circuit is a three-phase bridge circuit.

[0019] Optionally, the AC-side conversion circuit is either a frequency conversion circuit or a matrix conversion circuit.

[0020] Optionally, when the transformer is a single-phase transformer:

[0021] The AC-side conversion circuit is a half-bridge conversion circuit, with its switch arm and capacitor arm connected in parallel between the two ends of the second side of the AC-side conversion circuit; the switch arm includes two bidirectional switches that serve as the upper and lower half-bridge arms respectively, and the capacitor arm includes two capacitor modules connected in series with the same capacitance; the midpoint of the switch arm and the midpoint of the capacitor arm serve as the two ends of the first side of the AC-side conversion circuit respectively; or,

[0022] The AC-side conversion circuit is a full-bridge conversion circuit, wherein its two switching bridge arms are connected in parallel between the two ends of the second side of the AC-side conversion circuit; the midpoints of the two switching bridge arms respectively serve as the two ends of the first side of the AC-side conversion circuit; or,

[0023] The AC-side conversion circuit is a three-phase bridge conversion circuit, in which the three switch bridge arms are connected in parallel between the two ends of the first side of the AC-side conversion circuit; the midpoints of the three switch bridge arms are respectively used as the ends of the second side of the AC-side conversion circuit.

[0024] Optionally, when the transformer is a three-phase transformer, the AC side conversion circuit includes: three conversion circuits;

[0025] Each of the two sides of the aforementioned conversion circuit serves as the corresponding phase on both sides of the AC-side conversion circuit.

[0026] Optionally, each of the aforementioned conversion circuits includes: a rectifier bridge and a half-bridge circuit;

[0027] The AC side of the rectifier bridge serves as the first phase of the AC-side conversion circuit, the DC side of the rectifier bridge is connected to both ends of the half-bridge circuit, and the midpoint of the half-bridge circuit serves as the second phase of the AC-side conversion circuit.

[0028] Optionally, the leakage inductance of the transformer is less than a preset value; or,

[0029] It also includes: a resonant capacitor disposed on the primary or secondary side of the transformer; the switching frequency of the switching transistor in the AC-side conversion circuit and each of the DC-side conversion circuits is equal to the resonant frequency of the resonant capacitor and the leakage inductance of the transformer, or is greater than the resonant frequency and the difference between the two is less than a preset difference.

[0030] Optionally, it further includes: an AC-side filter circuit disposed on the second side of the AC-side conversion circuit; and / or,

[0031] Each DC-side filter circuit is respectively set on the DC side of each DC-side conversion circuit.

[0032] A second aspect of this application provides a control method for a single-stage multiplex DC-DC converter, applied to a single-stage multiplex DC-DC converter as described in any of the first aspects above, the control method comprising:

[0033] Obtain the electrical parameters on both sides of the single-stage multi-channel DC-DC converter and determine the power transmission direction required by the single-stage multi-channel DC-DC converter;

[0034] Based on the electrical parameters on both sides and the power transmission direction, determine the switching frequency and inner and outer phase shift angles of the single-stage multi-channel DC-DC converter;

[0035] Based on the switching frequency and the internal and external phase shift angles, control signals for each switch of the single-stage multi-channel DC-DC converter are generated and output to realize phase shift control of the single-stage multi-channel DC-DC converter.

[0036] Optionally, the switching frequency is the frequency at which the primary impedance of the transformer in the single-stage multi-channel DC-DC converter becomes inductive.

[0037] Optionally, the inner and outer phase shift angles include: the inner and outer phase shift angles of each DC-side conversion circuit in the single-stage multi-channel DC-DC converter;

[0038] Each of the aforementioned outward phase shift angles is determined based on the power transmission direction;

[0039] Each of the aforementioned inner phase shift angles and each of the aforementioned outer phase shift angles are independent of each other.

[0040] The single-stage multi-channel DC-DC converter provided in this application connects the AC side of each DC-side conversion circuit to the primary winding of a transformer via corresponding impedance elements. These impedance elements decouple the power between the DC-side conversion circuits, allowing a single transformer to centrally process the energy input or output of multiple DC-side conversion circuits, thus enabling multi-channel DC access. Furthermore, each DC-side conversion circuit performs AC-DC conversion, and the turns ratio of the primary and secondary windings of the transformer determines the corresponding voltage transformation ratio. The AC-side conversion circuit connected to the secondary winding of the transformer can perform AC frequency conversion, thereby achieving single-stage conversion. Therefore, this single-stage multi-channel DC-DC converter can achieve multi-channel DC access in a single-stage conversion configuration, thereby improving conversion efficiency and reducing costs. Attached Figure Description

[0041] 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.

[0042] Figure 1 A schematic diagram of a two-stage isolated multiplexer provided for existing technology;

[0043] Figure 2 This is a schematic diagram of the structure of a single-stage multi-channel DC-DC converter provided in an embodiment of this application;

[0044] Figure 3a A schematic diagram of a DC-side converter circuit provided in an embodiment of this application;

[0045] Figure 3b Another schematic diagram of the DC-side conversion circuit provided in the embodiments of this application;

[0046] Figure 3c Another schematic diagram of the DC-side conversion circuit provided in the embodiments of this application;

[0047] Figure 4a A structural diagram of an AC-side conversion circuit provided in an embodiment of this application;

[0048] Figure 4b Another structural diagram of the AC-side conversion circuit provided in the embodiments of this application;

[0049] Figure 4cAnother structural diagram of the AC-side conversion circuit provided in the embodiments of this application;

[0050] Figure 4d Another structural diagram of the AC-side conversion circuit provided in the embodiments of this application;

[0051] Figure 5 A detailed circuit diagram of a single-stage multi-channel DC-DC converter provided in an embodiment of this application;

[0052] Figure 6 The fundamental equivalent circuit diagram of a single-stage multi-channel DC-DC converter provided in the embodiments of this application;

[0053] Figure 7a A waveform diagram of the drive signal of a single-stage multi-channel DC-DC converter provided in an embodiment of this application during the positive half-cycle of the power grid.

[0054] Figure 7b A waveform diagram of the drive signal of a single-stage multi-channel DC-DC converter provided in an embodiment of this application during the negative half-cycle of the power grid.

[0055] Figure 8 A flowchart of a control method for a single-stage multi-channel DC-DC converter provided in an embodiment of this application;

[0056] Figure 9 Another waveform diagram of the drive signal of the single-stage multi-channel DC-DC converter provided in the embodiments of this application during the positive half-cycle of the power grid. Detailed Implementation

[0057] 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.

[0058] In this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0059] This application provides a single-stage multi-channel DC-DC converter to achieve multi-channel DC access, thereby improving efficiency and reducing costs.

[0060] See Figure 2 The single-stage multi-channel DC-DC converter includes: a transformer T, an AC-side conversion circuit 102, at least two DC-side conversion circuits 101, and their corresponding impedance elements (such as...). Figure 2 Z1 to Zn are shown in the figure; where:

[0061] Each DC-side conversion circuit 101 is composed of power semiconductor devices such as MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) or IGBTs (Insulated Gate Bipolar Transistors) with anti-parallel diodes. Its AC side is connected to the primary winding of transformer T through corresponding impedance elements. Its DC side serves as one DC interface of this single-stage multi-channel DC-DC converter, connecting to a corresponding DC power supply or DC load. Each DC interface can be connected to a DC power supply, a DC load, or a combination thereof, depending on the specific application environment. In practical applications, the DC power supply can be a photovoltaic cell module, a power battery, or a fuel cell, and the DC load can be a charging power battery, etc. Furthermore, each DC-side conversion circuit 101 can also be equipped with a corresponding DC-side filter circuit (not shown in the figure).

[0062] Each impedance element Z1 to Zn can be an inductor, or other forms can be selected, such as an inductor and a capacitor. The inductor and capacitor can be connected in series or in other ways. Moreover, the inductance of each impedance element Z1 to Zn can be the same or different, depending on the specific application environment, and all of these are within the protection scope of this application.

[0063] The transformer T can be a high-frequency transformer, specifically a single-phase transformer (such as...). Figure 2 (As shown in the diagram), it can also be a three-phase transformer, depending on the specific application environment; moreover, its secondary winding is connected to the first side of the AC-side conversion circuit 102; the second side of the AC-side conversion circuit 102 serves as the AC interface of the single-stage multi-channel DC-DC converter, used to connect to an AC source or AC load, which can be the power grid; in practical applications, the second side of the AC-side conversion circuit 102 can be connected to an AC source or AC load through a corresponding AC-side filter circuit 103.

[0064] The specific working principle is as follows:

[0065] During forward power transmission, each DC-side conversion circuit 101 inverts the DC power it receives to generate a square wave voltage. Each square wave voltage is coupled to the primary winding of the high-frequency transformer T through a corresponding impedance element. The impedance elements can decouple the power between the DC-side conversion circuits 101; that is, due to the presence of the impedance elements Z1 to Zn, power decoupling can be achieved between the input DC power supplies. After passing through the high-frequency transformer T, the high-frequency square wave voltage is coupled to the AC-side conversion circuit 102, which then performs AC frequency conversion, such as transmitting AC power according to the frequency required by the power grid or AC load. This achieves the conversion from high-frequency (e.g., 100kHz) AC power to low-frequency (e.g., power frequency 50Hz, 60Hz) AC power, and finally connects to the power grid or AC load through filtering and other circuits.

[0066] Since the AC-side conversion circuit 102 processes power from n inputs (such as... Figure 2 The sum of the power of inputs 1, 2, ..., n shown in the figure is high. Therefore, the AC-side conversion circuit 102 has high voltage and high power. If the MOSFET cannot meet the requirements, high voltage devices such as IGBTs can be selected. In order to improve efficiency, SiC (silicon nitride), GaN (gallium nitride), or a hybrid device composed of IGBT and SiC can also be selected. It depends on the specific application environment and all of them are within the protection scope of this application.

[0067] When power is transmitted in reverse, the AC-side conversion circuit 102 converts the low-frequency AC power from the AC source into high-frequency AC power, which is then transmitted to each DC-side conversion circuit 101 through the transformer T and each impedance element Z1 to Zn. Each DC-side conversion circuit 101 rectifies the AC power it receives and outputs it to each DC load.

[0068] The single-stage multi-channel DC-DC converter provided in this embodiment has each DC-side conversion circuit 101 connected to the primary winding of transformer T through its corresponding impedance element. The impedance elements Z1 to Zn can achieve power decoupling in hardware, thus eliminating the need for complex control algorithms to achieve software power decoupling. A single transformer T can centrally process the energy input or output of multiple DC-side conversion circuits 101, realizing multi-channel DC access. Moreover, each DC-side conversion circuit 101 is used to realize AC-DC conversion. The turns ratio of the primary and secondary windings of transformer T can realize the corresponding transformation ratio of the primary and secondary voltages. The AC-side conversion circuit 102 connected to the secondary winding of transformer T can perform AC frequency conversion, thus realizing single-stage conversion. Therefore, this single-stage multi-channel DC-DC converter can realize multi-channel DC access in the form of single-stage conversion, thereby improving conversion efficiency.

[0069] In addition, although each impedance element Z1 to Zn is an independent device in this single-stage multi-channel DC-DC converter, the energy of multiple DC-DC inputs can be centrally processed by only one transformer T, which is easy to implement; furthermore, the high-frequency transformer T and the AC-side conversion circuit 102 are centrally designed, which is beneficial for increasing the power of the converter.

[0070] It should be noted that in practical applications, it is not ruled out that another impedance element may be provided between the secondary winding and the AC-side conversion circuit 102; however, for structural and cost considerations, it is preferable not to provide such an impedance element between the secondary winding and the AC-side conversion circuit 102.

[0071] Based on the previous embodiment, this embodiment provides some specific optional implementations of the DC-side conversion circuit 101 and the AC-side conversion circuit 102 in the single-stage multi-channel DC-DC converter, such as:

[0072] When the transformer T is a single-phase transformer, the DC-side conversion circuit 101 can adopt a half-bridge circuit according to the power level (e.g., Figure 3a (as shown) or full-bridge circuit (such as) Figure 3b (As shown).

[0073] When the transformer T is a three-phase transformer, such as Figure 3c As shown, the primary windings of each phase of the three-phase transformer have their corresponding terminals connected to the corresponding AC phase of the DC-side conversion circuit 101 via corresponding impedance elements (inductors are shown as an example in the figure), and their other ends are all connected to reference ground. The secondary windings of each phase of the three-phase transformer T have their two ends connected to the corresponding first phase of the AC-side conversion circuit 102, with their middle taps connected. In this case, the DC-side conversion circuit 101 can also be a three-phase bridge circuit, with the midpoint of each phase bridge arm connected to the corresponding phase primary winding of the transformer T via corresponding impedance elements.

[0074] In practical applications, the DC-side conversion circuit 101 can also adopt other conversion structures that convert DC voltage into high-frequency pulsating voltage. These are just two examples and are not limited to this one.

[0075] The AC-side conversion circuit 102 employs a frequency conversion circuit or a matrix conversion circuit. Furthermore, when the transformer T is a single-phase transformer, the AC-side conversion circuit 102 can specifically employ a hybrid conversion circuit composed of a bidirectional switching bridge arm and a capacitor bridge arm (e.g., ...). Figure 4a (As shown), a converter circuit composed of all bidirectional switching bridge arms can also be used (such as...). Figure 4b and Figure 4c (As shown). In a three-phase AC load application scenario, if the transformer T is a single-phase transformer, then the AC side conversion circuit 102 can be a frequency converter composed of three bidirectional switching bridge arms (e.g., Figure 4c (as shown); if transformer T is a three-phase transformer, then the AC side conversion circuit 102 may include three conversion circuits (such as...). Figure 4d (As shown).

[0076] See Figure 4a The transformer T is a single-phase transformer, and the AC-side conversion circuit 102 is a half-bridge conversion circuit. Its switch arm and capacitor arm are connected in parallel between the two ends of the second side of the AC-side conversion circuit 102. The switch arm includes two bidirectional switches connected in series, wherein the switching transistor S... S1 and S S2 The bidirectional switch formed serves as the upper half-bridge arm, controlled by the switching transistor S. S3 and S S4 The bidirectional switch forms the lower half-bridge arm. This capacitor bridge arm includes two capacitor modules C1 and C2 connected in series with the same capacitance. The midpoints of the switch bridge arm and the capacitor bridge arm serve as the two ends of the first side of the AC-side conversion circuit 102, respectively.

[0077] See Figure 4b The transformer T is a single-phase transformer, and the AC-side conversion circuit 102 is a full-bridge conversion circuit. Both of its two switching arms are connected in parallel with a capacitor module C3 between the two ends of the second side of the AC-side conversion circuit 102. Each switching arm includes two bidirectional switches connected in series; in one switching arm, the bidirectional switch composed of switching transistors Ss1 and Ss2 forms the upper half-bridge arm, and the bidirectional switch composed of switching transistors Ss3 and Ss4 forms the lower half-bridge arm; in the other switching arm, the bidirectional switch composed of switching transistors Ss1' and Ss2' forms the upper half-bridge arm, and the bidirectional switch composed of switching transistors Ss3' and Ss4' forms the lower half-bridge arm. The midpoints of the two switching arms are respectively the two ends of the first side of the AC-side conversion circuit 102. The capacitor module C3 belongs to... Figure 2 The AC side filter circuit 103 shown is illustrated.

[0078] See Figure 4cThe transformer T is a single-phase transformer, and the AC-side conversion circuit 102 is a three-phase bridge conversion circuit, with its three switch arms connected in parallel between the two ends of the first side of the AC-side conversion circuit 102. Each switch arm includes two bidirectional switches connected in series; in one switch arm, the bidirectional switch composed of switches Ss1 and Ss2 is the upper half-bridge arm, and the bidirectional switch composed of switches Ss3 and Ss4 is the lower half-bridge arm; in another switch arm, the bidirectional switch composed of switches Ss1' and Ss2' is the upper half-bridge arm, and the bidirectional switch composed of switches Ss3' and Ss4' is the lower half-bridge arm; in the third switch arm, the bidirectional switch composed of switches Ss1" and Ss2" is the upper half-bridge arm, and the bidirectional switch composed of switches Ss3" and Ss4" is the lower half-bridge arm. The midpoints of the three switch bridge arms serve as the second terminals of the AC-side conversion circuit 102; furthermore, each pair of terminals on the second side of the AC-side conversion circuit 102 is connected to corresponding capacitor modules C5 to C7, all of which belong to... Figure 2 The AC side filter circuit 103 shown is illustrated.

[0079] See Figure 4d At this point, the transformer T is a three-phase transformer, and the AC-side conversion circuit 102 includes: three conversion circuits; the two sides of each conversion circuit respectively serve as the corresponding phases on both sides of the AC-side conversion circuit 102. In practical applications, each conversion circuit can be configured as follows: Figure 4d As shown, it includes: a rectifier bridge 201 and a half-bridge circuit 202. The AC side of the rectifier bridge 201 serves as the first phase of the AC-side conversion circuit 102. The DC side of the rectifier bridge 201 is connected to both ends of the half-bridge circuit 202. The midpoint of the half-bridge circuit 202 serves as the second phase of the AC-side conversion circuit 102. Specifically, in one conversion circuit, the AC side of its rectifier bridge 201 serves as the first phase A of the AC-side conversion circuit 102, and the midpoint of its half-bridge circuit 202 serves as the second phase A of the AC-side conversion circuit 102; in another conversion circuit, the AC side of its rectifier bridge 201 serves as the first phase B of the AC-side conversion circuit 102, and the midpoint of its half-bridge circuit 202 serves as the second phase B of the AC-side conversion circuit 102; in a third conversion circuit, the AC side of its rectifier bridge 201 serves as the first phase C of the AC-side conversion circuit 102, and the midpoint of its half-bridge circuit 202 serves as the second phase C of the AC-side conversion circuit 102. Each rectifier bridge 201 can be... Figure 4d The rectifier bridge shown can be composed of diodes; it can also be a full-bridge structure composed of controllable semiconductor switches such as MOSFETs or IGBTs to achieve bidirectional energy transfer; it depends on the specific application environment, and all of them are within the protection scope of this application.

[0080] In practical applications, the aforementioned capacitor modules can be single capacitors or multiple capacitors connected in series or parallel; the choice depends on the specific application environment, and all are within the scope of protection of this application. Furthermore, Figures 4a to 4d These are just a few optional topologies for the AC-side conversion circuit 102, and are not limited to them. In practical applications, various forms of matrix conversion circuits can also be used to achieve adaptive connections with corresponding AC sources or AC loads.

[0081] Figure 5 Taking a 4-input converter as an example, this diagram illustrates a converter with an H-bridge structure on the primary side and a hybrid circuit consisting of switching bridge arms and capacitor bridge arms on the secondary side. Each H-bridge is connected via an inductor (such as an inductor acting as an impedance element). Figure 5 The inductors L1 to L4 shown are coupled to the transformer T, wherein each inductor L1 to L4 can be designed to have the same inductance; the capacitor modules C1 and C2 are designed to have the same capacitance.

[0082] It is worth noting that, Figure 5 Llk in the transformer T is the leakage inductance. Through proper design of the transformer T, the leakage inductance Llk can be minimized, for example, by making it less than a certain preset value, so as to reduce its impact on power transmission.

[0083] Alternatively, in practical applications, a capacitor can be connected in series with the transformer T. This capacitor serves as a resonant capacitor and can be located on either the primary or secondary side of the transformer T. Specifically, it can be located between the primary winding of the transformer T and each impedance element, or between the secondary winding of the transformer T and the AC-side conversion circuit 102. Furthermore, by setting the switching frequencies of the switching transistors in the AC-side conversion circuit 102 and each DC-side conversion circuit 101 to be near the resonant frequency of the leakage inductance Llk and this resonant capacitor, the influence of the leakage inductance Llk on power transmission can be reduced. Specifically, the switching frequency can be set to be equal to the resonant frequency or slightly greater than the resonant frequency, with the difference between the two being less than a preset difference. This depends on the specific application environment and is within the scope of protection of this application.

[0084] Figure 6 Taking a 4-channel input as an example, it is shown Figure 2 and Figure 5 The fundamental equivalent circuit of the circuit structure shown is as follows, where, It is the fundamental equivalent voltage of the high-frequency pulsating voltage of any bridge arm. It is the fundamental voltage of the power grid. It is the output current of any DC-side converter circuit 101. ω is the input current of the AC-side conversion circuit 102, w is the angular frequency of the switching transistor in the circuit, Lx' (x = 1, 2, 3, 4) is the equivalent inductance of any impedance element connected to the DC-side conversion circuit 101 after conversion, and C1 is the equivalent capacitance of the AC side of the single-stage multi-channel DC-DC converter. This equivalent capacitance can be derived from the capacitor bridge arm in Figure 4, or from the capacitor connected in series with the AC-side conversion circuit 102 for impedance adjustment.

[0085] Depend on Figure 6 It can be seen that adjustment to and The phase between the two points can determine the amount of power transferred from each branch to the grid. Therefore, the circuit can adopt fixed-frequency phase-shift control, that is, the control strategy of the AC-side conversion circuit 102 and each DC-side conversion circuit 101 can be a fixed-frequency phase-shift control strategy. Furthermore, the operating frequency of each semiconductor device, that is, each switching transistor in the AC-side conversion circuit 102 and each DC-side conversion circuit 101, should be selected to make the primary impedance of the transformer T inductive, so as to provide conditions for the device ZVS (Zero Voltage Switch).

[0086] Figure 5 Taking the DC-side converter circuit 101 as a full-bridge circuit and the AC-side converter circuit 102 including a switching bridge arm and a capacitor bridge arm as an example, in this case:

[0087] The switching transistors in each DC-side conversion circuit 101 and AC-side conversion circuit 102 are driven with a 50% duty cycle, and a certain dead time is set between the complementary drive signals.

[0088] In each DC-side converter circuit 101, the switching transistors of the upper and lower half-arms of each bridge arm operate complementaryly, and the drive signals of the switching transistors of different half-arms in different bridge arms differ by an inward phase shift angle. (See also...) Figure 7a and Figure 7b Taking input 1 as an example, its switching transistors Sp11 and Sp12 work in a complementary manner, and its switching transistors Sp13 and Sp14 work in a complementary manner. The drive signal of the switching transistor Sp11 leads the drive signal of the switching transistor Sp14 by an angle β.

[0089] In the AC-side conversion circuit 102, when the instantaneous value of the grid voltage is greater than zero, the diodes of the upper half-bridge arm (Ss1) pointing towards the grid and the diodes of the lower half-bridge arm (Ss3) pointing towards the secondary winding operate complementaryly, while the other switches are directly connected. When the instantaneous value of the grid voltage is less than zero, the diodes of the upper half-bridge arm (Ss2) pointing towards the secondary winding and the diodes of the lower half-bridge arm (Ss4) pointing towards the grid operate complementaryly, while the other switches are directly connected. Furthermore, the drive signals of the switches in each DC-side conversion circuit 101 differ from the drive signals of the switches in the AC-side conversion circuit 102 by an external phase shift angle. Taking input 1 as an example, when the grid voltage is positive, switches Ss1 and Ss3 operate complementaryly, switches Ss2 and Ss4 are always on, and the drive signal of switch Sp11 leads the drive signal of switch Ss1 by an angle α (signal waveform as shown). Figure 7a (As shown); When the mains voltage is negative, switches Ss2 and Ss4 work complementaryly, switches Ss1 and Ss3 are always on, and the drive signal of switch Sp11 leads the drive signal of switch Ss4 by an angle α (signal waveform as shown). Figure 7b (As shown). Figure 7a and Figure 7b In the diagram, V1 is the output voltage of the DC-side converter circuit 101 corresponding to input 1. g i is the secondary voltage of transformer T. res It is the current in transformer T.

[0090] The drive signal logic for inputs 2 to 4 is the same as that for input 1, but the specific values ​​of α and β for each input are independent of each other, that is, each inner phase shift angle and each outer phase shift angle are independent of each other. Each input uses two control degrees of freedom (α and β angles) for control because by combining the two control degrees of freedom, the effective value of the bridge arm output current can be reduced when transmitting the same power, thereby optimizing the conduction loss.

[0091] Another embodiment of this application provides a control method for a single-stage multiplex DC-DC converter, which is applied to the single-stage multiplex DC-DC converter as described in any of the above embodiments. This control method is as follows: Figure 8 As shown, it specifically includes:

[0092] S101. Obtain the electrical parameters on both sides of the single-stage multi-channel DC-DC converter and determine the power transmission direction required by the single-stage multi-channel DC-DC converter.

[0093] The electrical parameters on both sides include at least one of the voltage, current and power on both sides of the single-stage multi-channel DC-DC converter, depending on the specific application environment.

[0094] The power transfer directions required by the single-stage multi-channel DC access converter include: the forward transfer direction when power is inverted from its DC interface to its AC interface, and the reverse transfer direction when power is rectified from its AC interface to its DC interface.

[0095] S102. Determine the switching frequency and internal and external phase-shift angles of the single-stage multi-channel DC access converter according to the electrical parameters on both sides and the power transfer direction.

[0096] After determining the switching frequency, the action period Ts of each switching tube in the single-stage multi-channel DC access converter can be determined.

[0097] Among them, the switching frequency is preferably: the frequency that makes the primary impedance of the transformer in the single-stage multi-channel DC access converter inductive, thereby providing conditions for ZVS of the device.

[0098] The internal and external phase-shift angles include: the internal phase-shift angle (i.e., β described in the above embodiment) and the external phase-shift angle (i.e., α described in the above embodiment) of each DC-side conversion circuit in the single-stage multi-channel DC access converter; each external phase-shift angle is determined according to the power transfer direction. Still taking the case where the input 1 in Figure 5 is positive for the grid voltage as an example, see Figure 9 , by adjusting the leading and lagging of the external phase-shift angle α, the power transfer direction can be controlled. When the power area S1 > S2, the topology realizes forward power transfer; when the power area S1 > S2, the topology realizes forward power transfer; when the power area S1 < S2, the topology realizes reverse power transfer; Figure 9 In p , V1 is the output voltage of the DC-side conversion circuit 101 corresponding to the input 1, V k is the primary voltage of the transformer T, i

[0099] Moreover, each internal phase-shift angle and each external phase-shift angle are independent of each other.

[0100] S103. Generate and output control signals for each switching tube of the single-stage multi-channel DC access converter according to the switching frequency and internal and external phase-shift angles, and realize the phase-shift control of the single-stage multi-channel DC access converter.

[0101] This control method can realize the phase-shift control of the single-stage multi-channel DC access converter. The specific principle of this phase-shift control can be seen in the above embodiment and will not be elaborated here; moreover, by making each internal phase-shift angle and each external phase-shift angle independent of each other, this control method can also optimize the conduction loss.

[0102] Similar or identical parts between the various embodiments in this specification can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the description of the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment solution according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0103] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0104] The features described above regarding the disclosed embodiments can be substituted for or combined with each other to enable those skilled in the art to implement 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 can 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 single-stage multi-path dc access converter, characterized by, The application relates to a power conversion system comprising: a transformer, an alternating current side conversion circuit, at least two direct current side conversion circuits and their corresponding impedance elements; wherein, the alternating current side of each of the direct current side conversion circuits is connected in parallel to the primary winding of the transformer through its corresponding impedance element; the impedance element comprises an inductor or an inductor and a capacitor; the secondary winding of the transformer is connected to the first side of the alternating current side conversion circuit; each of the direct current side conversion circuits is used for inverting the direct current received by itself or rectifying the alternating current received by itself; each of the impedance elements is used for power decoupling between each of the direct current side conversion circuits; the alternating current side conversion circuit is used for alternating current frequency conversion.

2. The single-stage multi-way DC access converter of claim 1, wherein, The transformer is a single-phase transformer or a three-phase transformer.

3. The single-stage multi-way dc access converter of claim 2, wherein, For the three-phase transformer, the same end of each phase primary winding is connected to the corresponding phase of the alternating current side of each of the direct current side conversion circuits through each corresponding impedance element, and the other end is connected to a reference ground; the two ends of each phase secondary winding of the three-phase transformer are connected to the corresponding phase of the first side of the alternating current side conversion circuit through the intermediate tap.

4. The single-stage multi-way dc access converter of claim 1, wherein, When the transformer is a single-phase transformer, the direct current side conversion circuit is a half-bridge circuit or a full-bridge circuit; When the transformer is a three-phase transformer, the direct current side conversion circuit is a three-phase bridge circuit.

5. The single-stage multi-way dc access converter of any one of claims 1 to 4, wherein, The alternating current side conversion circuit is a cycle conversion circuit or a matrix conversion circuit.

6. The single-stage multi-way dc access converter of claim 5, wherein, When the transformer is a single-phase transformer: the alternating current side conversion circuit is a half-bridge conversion circuit, the switching bridge arm and the capacitor bridge arm of which are connected in parallel between the two ends of the second side of the alternating current side conversion circuit; the switching bridge arm comprises two bidirectional switches serving as upper and lower half-bridge arms, and the capacitor bridge arm comprises two capacitor modules connected in series and having the same capacity; the midpoint of the switching bridge arm and the midpoint of the capacitor bridge arm serve as the two ends of the first side of the alternating current side conversion circuit, respectively; or, the alternating current side conversion circuit is a full-bridge conversion circuit, and the two switching bridge arms thereof are connected in parallel between the two ends of the second side of the alternating current side conversion circuit; the midpoints of the two switching bridge arms serve as the two ends of the first side of the alternating current side conversion circuit, respectively; or, the alternating current side conversion circuit is a three-phase bridge conversion circuit, and the three switching bridge arms thereof are connected in parallel between the two ends of the first side of the alternating current side conversion circuit; the midpoints of the three switching bridge arms serve as each end of the second side of the alternating current side conversion circuit, respectively.

7. The single-stage multiway dc access converter of claim 5, wherein, When the transformer is a three-phase transformer, the alternating current side conversion circuit comprises three conversion circuits; the two sides of each of the conversion circuits serve as the corresponding phase of the two sides of the alternating current side conversion circuit, respectively.

8. The single-stage multiway dc access converter of claim 7, wherein, each of the conversion circuits comprises a rectifier bridge and a half-bridge circuit; the alternating current side of the rectifier bridge serves as the corresponding phase of the first side of the alternating current side conversion circuit, the direct current side of the rectifier bridge is connected to the two ends of the half-bridge circuit, and the midpoint of the half-bridge circuit serves as the corresponding phase of the second side of the alternating current side conversion circuit.

9. The single-stage multi-way dc access converter of any one of claims 1 to 4, wherein, The leakage inductance of the transformer is less than a preset value; or, Further comprising: a resonance capacitor arranged at the primary side or the secondary side of the transformer, and a switching frequency of the switch tube in the AC side conversion circuit and each of the DC side conversion circuits, which is equal to a resonance frequency of the resonance capacitor and a leakage inductance of the transformer, or greater than the resonance frequency and the difference between them is less than a preset difference.

10. The single-stage multi-way dc access converter of any one of claims 1 to 4, wherein, Further comprising: an AC side filter circuit arranged at the second side of the AC side conversion circuit; and / or, each DC side filter circuit arranged at the DC side of each of the DC side conversion circuits.

11. A control method of a single-stage multi-path DC access converter, characterized by, The control method is applied to the single-stage multi-path DC access converter as claimed in any one of claims 1 to 10, and the control method comprises: obtaining electrical parameters of both sides of the single-stage multi-path DC access converter and determining a power transmission direction required by the single-stage multi-path DC access converter; determining a switching frequency and an inner and outer phase shift angle of the single-stage multi-path DC access converter according to the electrical parameters of both sides and the power transmission direction; generating and outputting control signals for each switch tube of the single-stage multi-path DC access converter according to the switching frequency and the inner and outer phase shift angle, so as to realize phase shift control of the single-stage multi-path DC access converter.

12. The control method of the single-stage multiway DC access converter according to claim 11, characterized by, The switching frequency is a frequency that makes the impedance of the primary side of the transformer in the single-stage multi-path DC access converter inductive.

13. The control method of a single-stage multiway DC access converter according to claim 11 or 12, characterized by, The inner and outer phase shift angles include an inner phase shift angle and an outer phase shift angle of each DC side conversion circuit in the single-stage multi-path DC access converter; Each of the outer phase shift angles is determined according to the power transmission direction; Each of the inner phase shift angles and each of the outer phase shift angles are independent of each other.

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