Modular dc transformer and control system
By constructing an autocoupling topology using the self-balancing module and DAB module of the modular DC transformer, the voltage balancing problem of the modular DC transformer is solved, achieving efficient energy transfer, simplifying the control strategy, and improving system efficiency.
Patent Information
- Application Number
- CN202411636552.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-15
- Publication Date
- 2025-12-05
- Estimated Expiration
- 2044-11-15
AI Technical Summary
Existing modular DC transformers face challenges in voltage balancing and have low energy transfer efficiency, especially in high-voltage applications where control strategies become more complex and losses increase.
A modular DC transformer structure is adopted, including a voltage self-balancing module and a DAB module. Through voltage regulation within the self-balancing module and energy transfer between modules, an autocoupling topology is constructed to achieve voltage balance and energy balance between modules.
It reduces the difficulty of voltage balancing, improves energy transmission efficiency, simplifies control strategies, reduces losses, and improves system efficiency.
Smart Images
Figure CN119382498B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of power electronics, and in particular to a modular DC transformer and a control system. BACKGROUND
[0002] With the increasingly prominent energy crisis and environmental problems, the research on renewable energy has gradually become the focus. Among various types of renewable energy, wind resources are abundant, especially offshore wind power with great potential. Therefore, offshore wind power has been widely used, and wind turbines applied to offshore wind power have also been developed on a large scale. Due to the large-scale development of wind turbines, the off-shore distance of wind power plants is gradually increasing, resulting in an increase in the charging current of submarine cables, increasing the operation cost and system loss of the wind power system and reducing the system efficiency. Therefore, the prior art proposes to use a pure DC system (including DC transmission and power collection system) without reactive power loss and frequency stability problem to realize the grid connection of a long-distance wind power plant, improve the efficiency of the system and reduce the system loss.
[0003] In the pure DC system, the DC transformer is a key device for connecting the wind turbine and the medium-voltage collection network, and is used to realize the conversion between different DC voltage levels, with the application demand of high transformation ratio and large capacity. In order to realize high-voltage application, one scheme is to expand the DC / DC converter applied in a low-voltage environment to a medium-high voltage environment through a series connection. However, after the series connection of IGBT in the DC / DC converter, voltage equalization becomes complex and it is difficult to achieve voltage balance. Another scheme is to use a modular multi-level DC transformer such as Buck-MMDCT. Although this scheme avoids the cumbersome problems caused by the series connection of devices, in actual application, it needs to inject an alternating current to realize the energy balance of the sub-modules, which makes the control strategy complex and the loss increases. Therefore, how to construct a new DC transformer to reduce the difficulty of voltage balance and improve the energy transmission efficiency has become a problem to be solved. SUMMARY
[0004] The present application provides a modular DC transformer and a control system for reducing the difficulty of voltage balance and improving the energy transmission efficiency.
[0005] In one aspect, the present application provides a modular DC transformer, comprising: at least two voltage self-balancing modules and at least one DAB module.
[0006] One of the voltage self-balancing modules is used as an input module, a primary port of the input module is connected with a low-voltage side, and a secondary port of the input module is connected with the DAB module in parallel.
[0007] The voltage self-balancing module of the non-input module is used as a transfer module, a primary port of the transfer module is connected in series with a primary port of the input module, and the primary port is used for being connected with a high-voltage side; a secondary port of the transfer module is connected with the DAB module;
[0008] The voltage self-balancing module is used for balancing voltages inside the voltage self-balancing module.
[0009] Optionally, the voltage self-balancing module comprises a voltage balancing component, a first direct-current capacitor, a second direct-current capacitor and an output capacitor.
[0010] The first direct-current capacitor, the second direct-current capacitor and the output capacitor are connected in series in sequence to form the primary port; two ends of the output capacitor are the secondary port.
[0011] The voltage balancing component is connected with two ends of the first direct-current capacitor, two ends of the output capacitor and two ends of the second direct-current capacitor respectively, and is used for balancing voltages of the first direct-current capacitor, the second direct-current capacitor and the output capacitor.
[0012] Optionally, the voltage balancing component comprises a first resonant branch, a second resonant branch, a first half-bridge sub-module, a second half-bridge sub-module and a third half-bridge sub-module.
[0013] The first half-bridge sub-module is connected in parallel with the first direct-current capacitor.
[0014] The second half-bridge sub-module is connected in parallel with the output capacitor.
[0015] The third half-bridge sub-module is connected in parallel with the second direct-current capacitor.
[0016] The first half-bridge sub-module, the second half-bridge sub-module and the third half-bridge sub-module are connected in series.
[0017] The first resonant branch is connected with the first half-bridge sub-module and the second half-bridge sub-module respectively.
[0018] The second resonant branch is connected with the second half-bridge sub-module and the third half-bridge sub-module respectively.
[0019] Optionally, the first resonant branch comprises a first resonant inductor and a first resonant capacitor; one end of the first resonant inductor and one end of the first resonant capacitor are connected in series.
[0020] The other end of the first resonant capacitor is connected with the first half-bridge sub-module.
[0021] The other end of the first resonant inductor is connected with the second half-bridge sub-module.
[0022] Optionally, the second resonance branch comprises a second resonance inductor and a second resonance capacitor; one end of the second resonance inductor and one end of the second resonance capacitor are connected in series;
[0023] The other end of the second resonance capacitor is connected with the second half-bridge sub-module;
[0024] The other end of the second resonance inductor is connected with the third half-bridge sub-module.
[0025] Optionally, the first half-bridge sub-module comprises a first semiconductor power switching device and a second semiconductor power switching device;
[0026] The first end of the first semiconductor power switching device is connected with one end of the first direct-current capacitor; the second end of the first semiconductor power switching device is connected with the other end of the first resonance capacitor and the first end of the second semiconductor power switching device respectively;
[0027] The second end of the second semiconductor power switching device is connected with the second half-bridge sub-module and the other end of the first direct-current capacitor respectively.
[0028] Optionally, the second half-bridge sub-module comprises a third semiconductor power switching device and a fourth semiconductor power switching device;
[0029] The first end of the third semiconductor power switching device is connected with one end of the output capacitor and the second end of the second semiconductor power switching device respectively; the second end of the third semiconductor power switching device is connected with the other end of the first resonance inductor, the other end of the second resonance capacitor and the first end of the fourth semiconductor power switching device respectively;
[0030] The second end of the fourth semiconductor power switching device is connected with the third half-bridge sub-module and the other end of the output capacitor respectively.
[0031] Optionally, the third half-bridge sub-module comprises a fifth semiconductor power switching device and a sixth semiconductor power switching device;
[0032] The first end of the fifth semiconductor power switching device is connected with one end of the second direct-current capacitor and the second end of the fourth semiconductor power switching device respectively; the second end of the fifth semiconductor power switching device is connected with the other end of the second resonance inductor and the first end of the sixth semiconductor power switching device respectively;
[0033] The second end of the sixth semiconductor power switching device is connected with the other end of the second direct-current capacitor.
[0034] The application further provides a control system, characterized by comprising a controller and the modular DC transformer as described above.
[0035] The controller is connected with the DAB module and the voltage self-balancing module in the modular DC transformer respectively.
[0036] Optionally, the controller is connected with the first half-bridge submodule, the second half-bridge submodule and the third half-bridge submodule in the voltage self-balancing module.
[0037] The application further provides a modular DC transformer, characterized by comprising at least two voltage self-balancing modules and at least one DAB module; one of the voltage self-balancing modules is used as an input module, a primary port of the input module is connected with a low-voltage side, and a secondary port of the input module is connected with the DAB module in parallel; a voltage self-balancing module that is not the input module is used as a transfer module, a primary port of the transfer module is connected with a primary port of the input module in series and is used for being connected with a high-voltage side, and a secondary port of the transfer module is connected with the DAB module; and the voltage self-balancing module is used for balancing the voltage inside the module.
[0038] As can be seen from the above technical solutions, the application has the following advantages:
[0039] In the application, the voltage self-balancing module has the characteristic of self-balancing, can self-adjust the voltage inside the module, achieves the effect of voltage balancing in the module, and in the application, one of the voltage self-balancing modules is used as an input module, the remaining voltage self-balancing modules are used as transfer modules, a primary port of the input module is connected with a low-voltage side, primary ports of all the voltage self-balancing modules are connected in series in turn and are used for being connected with a high-voltage side, a secondary port of the input module is connected with a DAB module, the DAB module is connected with secondary ports of the transfer modules, so that the topology of the entire DC transformer is formed into a self-coupling structure, energy can be transferred from the secondary port of the input module to other modules, energy balancing between the modules is achieved, and based on the topology provided by the application, energy can be directly transferred between an input stage and the DAB module, and the energy transmission efficiency is improved. As can be seen, the modular DC transformer provided by the application can conveniently achieve voltage balancing, reduces the difficulty of voltage balancing, improves the energy transmission efficiency, and solves the problem of complex voltage balancing of the existing modular DC transformer. BRIEF DESCRIPTION OF DRAWINGS
[0040] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only need to be some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort.
[0041] Figure 1 A structural schematic diagram of a modular DC transformer provided by the embodiment of the present application is shown in the figure.
[0042] Figure 2 A structural schematic diagram of a voltage self-balancing module provided by the embodiment of the present application is shown in the figure.
[0043] Figure 3 Another structural schematic diagram of a modular DC transformer provided by the embodiment of the present application is shown in the figure.
[0044] Figure 4 A principle schematic diagram of a voltage self-balancing module provided by the embodiment of the present application is shown in the figure, in which (a) is a principle schematic diagram of one working mode of the voltage self-balancing module; (b) is a principle schematic diagram of another working mode of the voltage self-balancing module.
[0045] Figure 5 A waveform schematic diagram of a voltage self-balancing module provided by the embodiment of the present application is shown in the figure.
[0046] Figure 6 A simulation waveform schematic diagram of a voltage self-balancing module provided by the embodiment of the present application is shown in the figure.
[0047] Figure 7 Another simulation waveform schematic diagram of a voltage self-balancing module provided by the embodiment of the present application is shown in the figure.
[0048] Figure 8 A structural schematic diagram of a control system provided by the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION
[0049] In order to avoid injecting AC circulating current, the prior art constructs an energy balancing channel structure between the modules of the Buck-MMDCT, which provides an additional control variable for energy balancing, so that the power loop and the energy balancing loop are controlled independently, but this mode needs to multiply the switching devices. In order to avoid increasing too many switching devices, the prior art also proposes to improve the energy channel, use DC capacitors to transmit DC current, and build auxiliary branches between the modules for energy transmission to balance the energy without increasing the number of devices. However, in this scheme, since the energy is still transmitted step by step, the corresponding loss will also be additionally increased, reducing the energy transmission efficiency. Therefore, how to construct a new DC transformer to reduce the difficulty of voltage balancing and improve the energy transmission efficiency has become a problem to be solved.
[0050] To solve the above problems, the embodiment of the present application provides a modular DC transformer and a control system, which are used for reducing the difficulty of voltage balancing and improving energy transmission efficiency.
[0051] In order to make the invention purposes, features and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the following described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.
[0052] Please refer to Figure 1 The present application provides a modular DC transformer, which comprises at least two voltage self-balancing modules 3RSC and at least one DAB module. One voltage self-balancing module 3RSC is used as an input module, the primary port of the input module is connected with a low-voltage side, and the secondary port of the input module is connected in parallel with the DAB module. The voltage self-balancing module 3RSC which is not the input module is used as a transfer module, the primary port of the transfer module is connected in series with the primary port of the input module, and is used for connecting with a high-voltage side. The secondary port of the transfer module is connected with the DAB module. The voltage self-balancing module 3RSC is used for balancing the voltage inside the module.
[0053] It should be noted that the voltage self-balancing module 3RSC is provided with two resonance circuits for balancing the voltage, the output voltage of the secondary port is adjusted, the voltage of the primary port is three times the voltage of the secondary port, so that the voltage inside the module is balanced. The DAB module refers to a dual active bridge (Dual Active Bridge) module, which can realize bidirectional energy transmission and voltage level conversion. The dual active bridge comprises two full-bridge circuits, a high-frequency transformer and a filter capacitor. The two full-bridge circuits are located at the input side and the output side of the high-frequency transformer. The full-bridge circuit located at the input side is used for converting the input DC voltage into an AC voltage. The transformer is used for converting the received AC voltage into an AC voltage of a suitable voltage level at the output side and outputting. The full-bridge circuit located at the output side is used for converting the received AC voltage into a DC voltage output. In the embodiment, the DAB module is used for power interaction between the input module and the transfer module. The low-voltage side is used for providing an input voltage for the modular DC transformer. The modular DC voltage converts the input voltage into a corresponding output voltage and outputs to the high-voltage side.
[0054] In the topology of the embodiment, each voltage self-balancing module 3RSC is provided with a primary port and a secondary port, and both the primary port and the secondary port have two ends. In the embodiment, one of the voltage self-balancing modules 3RSC is taken as an input module, and the remaining voltage self-balancing modules 3RSC are taken as transfer modules.
[0055] As shown in FIG. 1, Figure 1 the embodiment numbers the voltage self-balancing modules 3RSC as 3RSC-0 and 3RSC-x (x = 1, 2, …, n), 3RSC-0 is an input module, and 3RSC-1 to 3RSC-n are transfer modules respectively, wherein n is a positive integer. In the embodiment, the primary port of the input module 3RSC-0 is taken as a low-voltage side input interface, and the two ends thereof are connected with the low-voltage side V dc1 respectively. The primary ports of all the transfer modules 3RSC-1 to 3RSC-n are connected in series, and the one end of the primary port of the transfer module 3RSC-n located away from the input module 3RSC-0 is connected with the high-voltage side V dc2 respectively. Therefore, in the embodiment, the low-voltage side V dc1 and the high-voltage side V dc2 share the primary port of the input module 3RSC-0. The secondary port of the input module 3RSC-0 is connected with one end of a DAB module, and the other end of the DAB module is connected with a transfer module.
[0056] The number of the DAB modules is consistent with the number of the transfer modules. When the number of the DAB modules is multiple, the two ends of the secondary port of the input module 3RSC-0 are led out as a DC bus V bus , and each DAB module is connected to the DC bus V bus , so that the input voltages received by each DAB module are equal. Moreover, since each DAB module is connected with the secondary port of each transfer module one by one, in actual application, the output voltages of each DAB module can be controlled to be equal, so that the voltages of the secondary ports of each transfer module are equal. Since each transfer module has the function of self-balancing, the voltage of the primary port of each transfer module is three times the voltage of the secondary port, so that when the voltages of the secondary ports of each transfer module are equal, the voltages of the primary ports of each transfer module are also equal, thereby realizing the energy balance among the modules. Therefore, the entire topology of the modular DC transformer of the embodiment is a self-coupling structure, so that the energy can be transferred from the secondary port of the input module 3RSC-0 to other modules, realizing the energy balance among the modules, and based on the topology provided by the application, the energy can be directly transferred between the input stage and the DAB module, improving the energy transmission efficiency.
[0057] Based on the multi-module DC transformer provided in the embodiment, in actual application, different voltage transformation ratios can be achieved by changing the number of transmission modules and DAB modules, without injecting AC commutation and complex voltage equalization strategies, and moreover, the voltage self-balancing module 3RSC has the characteristic of self-balancing, so in actual operation, only the output voltage of the DAB module needs to be controlled to achieve overall voltage control. Moreover, in the modular DC transformer constructed in the embodiment, the energy between the modules can be transmitted through the DC bus, the overall transmission loss is small, and the transmission efficiency is high. As can be seen, the modular DC transformer provided in the application can conveniently achieve voltage balancing, reduce the difficulty of voltage balancing, improve the energy transmission efficiency, and solve the problem of complex voltage balancing of the existing modular DC transformer.
[0058] In one specific embodiment, referring to Figure 2 , the voltage self-balancing module comprises a voltage balancing component 21, a first DC capacitor C p0 , a second DC capacitor C n0 and an output capacitor C o0 ;
[0059] The first DC capacitor C p0 , the second DC capacitor C n0 and the output capacitor C o0 are connected in series to form a primary port, and the two ends of the output capacitor C o0 are the secondary port.
[0060] The voltage balancing component 21 is connected to the two ends of the first DC capacitor C p0 , the two ends of the output capacitor C o0 and the two ends of the second DC capacitor C n0 , respectively, for balancing the voltage of the first DC capacitor C p0 , the voltage of the second DC capacitor C n0 and the voltage of the output capacitor C o0 .
[0061] It should be noted that the voltage balancing component 21 and the first DC capacitor C p0 form a resonance circuit, and the voltage balancing component 21 and the second DC capacitor C n0 form another resonance circuit. Among them, the first DC capacitor C p0 and the second DC capacitor C n0 can output electric energy to the voltage balancing component 21, and the voltage balancing component 21 charges the output capacitor C o0 to adjust the voltage at the two ends of the output capacitor C o0 , so that in one cycle, the first DC capacitor C p0 , the second DC capacitor C n0 and the output capacitor C o0The voltage at both ends is stabilized at a preset voltage value, so as to realize voltage balance in the module.
[0062] Specifically, the voltage self-balancing module has two working modes, which are alternately operated in half a cycle. In one working mode, the voltage balancing component 21 and the first DC capacitor C p0 are looped on, the voltage balancing component 21 and the output capacitor C o0 are looped on, wherein the first DC capacitor C p0 outputs electric energy to the voltage balancing component 21, and the voltage balancing component 21 outputs electric energy to the output capacitor C o0 . In another working mode, the voltage balancing component 21 and the second DC capacitor C n0 are looped on, and the resistance balancing component and the output capacitor C o0 are looped on, the second DC capacitor C n0 outputs electric energy to the voltage balancing component 21, and the voltage balancing component 21 outputs electric energy to the output capacitor C o0 .
[0063] In actual application, by outputting a driving signal to the voltage balancing component 21, the corresponding loop is turned on, so that the voltage self-balancing module alternately operates in the two working modes, so as to realize voltage balance among the first DC capacitor C p0 , the second DC capacitor C n0 , and the output capacitor C o0 , and achieve the purpose of voltage balance in the module.
[0064] In one specific embodiment, the voltage balancing component 21 includes a first resonant branch, a second resonant branch, a first half-bridge sub-module, a second half-bridge sub-module, and a third half-bridge sub-module.
[0065] The first half-bridge sub-module is connected in parallel with the first DC capacitor C p0 .
[0066] The second half-bridge sub-module is connected in parallel with the output capacitor C o0 .
[0067] The third half-bridge sub-module is connected in parallel with the second DC capacitor C n0 .
[0068] The first half-bridge sub-module, the second half-bridge sub-module, and the third half-bridge sub-module are connected in series.
[0069] The first resonant branch is connected with the first half-bridge sub-module and the second half-bridge sub-module, respectively.
[0070] The second resonant branch is connected with the second half-bridge sub-module and the third half-bridge sub-module, respectively.
[0071] It should be noted that the first resonant branch and the second resonant branch both adopt LC resonant circuits. The first resonant branch can form a loop with the first half-bridge sub-module, the second half-bridge sub-module and the first DC capacitor C p0 , or form a loop with the first half-bridge sub-module, the second half-bridge sub-module and the output capacitor C o0 . The second resonant branch is the same.
[0072] Specifically, in one working mode, the first resonant branch, the first half-bridge sub-module, the second half-bridge sub-module and the first DC capacitor C p0 form a loop, so that the first DC capacitor C p0 outputs electric energy to the first resonant branch, and the second resonant branch, the second half-bridge sub-module, the third half-bridge sub-module and the output capacitor C o0 form a loop, so that the second resonant branch outputs electric energy to the output capacitor C o0 . In another working mode, the first resonant branch, the first half-bridge sub-module, the second half-bridge sub-module and the output capacitor C o0 form a loop, so that the first resonant branch outputs electric energy to the output capacitor C o0 , and the second resonant branch, the second half-bridge sub-module, the third half-bridge sub-module and the second DC capacitor C n0 form a loop, so that the second DC capacitor C n0 outputs electric energy to the second resonant branch.
[0073] In one specific embodiment, referring to Figure 3 , the first resonant branch includes a first resonant inductor L rp0 and a first resonant capacitor C rp0 ; one end of the first resonant inductor L rp0 and one end of the first resonant capacitor C rp0 are connected in series;
[0074] the other end of the first resonant capacitor C rp0 is connected with the first half-bridge sub-module;
[0075] the other end of the first resonant inductor L rp0 is connected with the second half-bridge sub-module.
[0076] Further, the second resonant branch includes a second resonant inductor L rn0 and a second resonant capacitor C rn0 ; one end of the second resonant inductor L rn0 and one end of the second resonant capacitor C rn0 are connected in series;
[0077] the other end of the second resonant capacitor C rn0 is connected with the second half-bridge sub-module;
[0078] Second resonant inductor L rn0 The other end is connected to the third half-bridge submodule.
[0079] Furthermore, the first half-bridge sub-module includes a first semiconductor power switching device S. 01 Second semiconductor power switching device S 02 ;
[0080] First semiconductor power switching device S 01 The first terminal is connected to the first DC capacitor C. p0 One end is connected; the first semiconductor power switch device S 01 The second end is connected to the first resonant capacitor C. rp0 At the other end, the second semiconductor power switch device S 02 The first end is connected;
[0081] Second semiconductor power switching device S 02 The second end is connected to the second half-bridge submodule and the first DC capacitor C, respectively. p0 The other end is connected.
[0082] Furthermore, the second half-bridge submodule includes a third semiconductor power switching device S. 03 and the fourth semiconductor power switching device S 04 ;
[0083] Third semiconductor power switching device S 03 The first terminal is connected to the output capacitor C. o0 One end, the second semiconductor power switch device S 02 The second terminal is connected; the third semiconductor power switch device S 03 The second end is connected to the first resonant inductor L. rp0 The other end, the second resonant capacitor C rn0 At the other end, the fourth semiconductor power switch device S 04 The first end is connected;
[0084] Fourth semiconductor power switching device S 04 The second terminal is connected to the third half-bridge submodule and the output capacitor C, respectively. o0 The other end is connected.
[0085] Furthermore, the third half-bridge submodule includes a fifth semiconductor power switch device S. 05 and the sixth semiconductor power switching device S 06 ;
[0086] Fifth semiconductor power switching device S 05 The first terminal is connected to the second DC capacitor C. n0 One end, the fourth semiconductor power switch device S04 The second terminal is connected; the fifth semiconductor power switch device S 05 The second end is connected to the second resonant inductor L. rn0 At the other end, the sixth semiconductor power switch device S 06 The first end is connected;
[0087] Sixth Semiconductor Power Switching Device S 06 The second terminal is connected to the second DC capacitor C. n0 The other end is connected.
[0088] This embodiment uses the structure of the input module as an example to illustrate the internal structure of the voltage self-balancing module as follows.
[0089] like Figure 3 As shown, the first resonant capacitor C rp0 and the first resonant inductor L rp0 Series connection, and the first resonant capacitor C rp0 Connected to the first semiconductor power switch device S 01 Second semiconductor power switching device S 02 At the connection point, the first resonant inductor L rp0 Connected to the third semiconductor power switch S 03 and the fourth semiconductor power switching device S 04 At the connection point, the second resonant capacitor C rn0 With the second resonant inductor L rn0 Series connection, and the second resonant capacitor C rn0 Respectively with the first resonant inductor L rp0 Third semiconductor power switching device S 03 and the fourth semiconductor power switching device S 04 The connection point is the second resonant inductor L. rn0 Connected to the fifth semiconductor power switch device S 05 and the sixth semiconductor power switching device S 06 The connection point. First semiconductor power switching device S 01 Second semiconductor power switching device S 02 After being connected in series with the first DC capacitor C p0 Parallel connection, third semiconductor power switching device S 03 and the fourth semiconductor power switching device S 04 After being connected in series with the output capacitor C o0 Parallel connection, fifth semiconductor power switching device S 05 and the sixth semiconductor power switching device S 06 After being connected in series with the second DC capacitor C n0 Parallel connection, and the second semiconductor power switch S 02 and third semiconductor power switching device S03 in series, the fourth semiconductor power switch device S 04 with the fifth semiconductor power switch device S 05 in series.
[0090] wherein the first semiconductor power switch device S 01 to the sixth semiconductor power switch device S 06 can be divided into two groups, one group being the first semiconductor power switch device S 01 , the third semiconductor power switch device S 03 , the fifth semiconductor power switch device S 05 and the sixth semiconductor power switch device S 06 ; the other group being the second semiconductor power switch device S 02 , the fourth semiconductor power switch device S 04 , the sixth semiconductor power switch device S 06 . The two groups of semiconductor power switch devices are turned on in turn with a time of T s / 2, wherein T s is the time of one switching cycle of the semiconductor power switch device. Therefore, the whole working process of the input module can be divided into two working modes, as shown in Figure 4 . The corresponding turn-on pulse and the voltage and current waveforms of the resonant circuit are shown in Figure 5 .
[0091] Mode 1: when in [0-T s / 2], t=0, the first semiconductor power switch device S 01 , the third semiconductor power switch device S 03 , the fifth semiconductor power switch device S 05 are turned on, and the corresponding working circuit is shown in Figure 4 (a). The first resonant inductor L rp0 , the first resonant capacitor C rp0 , the first semiconductor power switch device S 01 , the first DC capacitor C p0 , the third semiconductor power switch device S 03 form a resonant circuit p. The second resonant capacitor C rn0 , the third semiconductor power switch device S 03 , the output capacitor C o0 , the fifth semiconductor power switch device S 05 , the second resonant inductor L rn0 form a resonant circuit n.
[0092] wherein the resonant circuit p absorbs energy from the first DC capacitor C p0 , so that the resonant current i rp0The resonance changes from zero and the voltage v rp0 of the resonance capacitor C rp0 increases from the minimum value. The resonance circuit n releases energy to the output capacitor C o0 so that the resonance current i rn0 also changes from zero and reverses the resonance and the voltage v rn0 of the resonance capacitor C rn0 decreases from the maximum value. When the present mode ends, the resonance current i rp0 and i rn0 both return to 0, the voltage v rp0 of the resonance capacitor C rp0 increases to the maximum value, and the voltage v rn0 of the resonance capacitor C rn0 decreases to the minimum value. The expressions of the current and the voltage during the whole mode are:
[0093]
[0094]
[0095] where t0 is the mode starting time, ω rp0 and ω rn0 are the resonance frequencies of the resonance circuit p and the resonance circuit n respectively, v cp0 is the voltage of the first DC capacitor C p0 , and v cn0 is the voltage of the second DC capacitor C n0 .
[0096] Mode two: when in [T s / 2-T s ], t=T s / 2, the second semiconductor power switch device S 02 , the fourth semiconductor power switch device S 04 , and the sixth semiconductor power switch device S 06 are turned on, and the corresponding working circuit is as shown in Figure 4 (b). The first resonance inductor L rp0 , the first resonance capacitor C rp0 , the second semiconductor power switch device S 02 , the output capacitor C o0 , and the fourth semiconductor power switch device S 04 constitute the resonance circuit p. The second resonance capacitor C rn0 , the fourth semiconductor power switch device S 04 , the second DC capacitor C n0 , the sixth semiconductor power switch device S 06 , and the second resonance inductor L rn0 constitute the resonance circuit n.
[0097] The output capacitor C of the resonant circuit p-direction o0 Release energy to make the resonant current i in the circuit... rp0 Starting from zero, the voltage v of the resonant capacitor changes in reverse resonance. rp0 It begins to decay from its maximum value. The resonant circuit n originates from the DC capacitor C. n0 Absorb energy to make the resonant current i rn0 Starting from zero, the resonant capacitance C changes. n0 voltage v rn0 The minimum value begins to increase. At the end of this mode, the resonant current i... rp0 and i rn0 All return to 0, resonant capacitance C rp0 voltage v rp0 The attenuation reaches its minimum value, while the resonant capacitance C n0 voltage v rn0 Increase to the maximum value.
[0098] Based on the above analysis, it can be seen that the characteristics of resonance cause the voltages of the three DC capacitors to automatically equalize, therefore the voltage V at the primary port... dc1 It is a secondary port V bus Three times that. Similarly, Figure 4 The topology is extended to a multi-module topology, that is, for Figure 3 Any 3RSC-x module (x=1,2,……n) exhibits resonant characteristics such that the primary port voltage V0 dcx All are three times the secondary port voltage. Figure 3 In this configuration, each DAB module is connected in parallel to the output capacitor C of 3RSC-0. o0 At this location, the input voltage is V. bus This voltage, after being transformed by DAB-x, becomes the voltage at the secondary port of 3RSC-x, which is C. ox The voltage. Due to the resonant characteristics of each 3RSC module, C in steady state px With C nx The voltages are all related to C ox Equal. Therefore, controlling the output voltage of DAB-x to be equal can achieve the same voltage across the primary and secondary sides of 3RSC-x. Furthermore, the entire topology has an autocoupling structure, thus allowing some energy to flow from the DC bus V. bus The energy transferred from the DAB is distributed to other 3RSC modules to achieve energy balance between modules. Therefore, by controlling the energy transferred from the DAB, the voltage of other 3RSC modules can be controlled, thereby achieving overall voltage balance.
[0099] In one example, the first semiconductor power switch device S 01 To the sixth semiconductor power switching device S 06IGBT tube can be selected. The first end of the first semiconductor power switch device S 01 , the first end of the second semiconductor power switch device S 02 , the first end of the third semiconductor power switch device S 03 , the first end of the fourth semiconductor power switch device S 04 , the first end of the fifth semiconductor power switch device S 05 , and the first end of the sixth semiconductor power switch device S 06 are all collector electrodes. The second end of the first semiconductor power switch device S 01 , the second end of the second semiconductor power switch device S 02 , the second end of the third semiconductor power switch device S 03 , the second end of the fourth semiconductor power switch device S 04 , the second end of the fifth semiconductor power switch device S 05 , and the second end of the sixth semiconductor power switch device S 06 are all emitter electrodes.
[0100] In order to further illustrate the effects achieved by the modular DC transformer provided by the embodiments of the present application, the following will be described in combination with a simulation application example as follows.
[0101] In this application example, simulation software (such as MATLAB / Simulink) is used, based on the topology structure of the modular DC transformer provided by the above embodiments, a corresponding simulation model is built, and the simulation model is experimentally verified. The simulation parameters are shown in Table 1, and there are 5 voltage self-balancing modules 3RSC.
[0102] The input voltage is set to 6kV, the output voltage is set to 35kV, the transmission power is set to 5MW, and the switching frequency of each semiconductor power switch device is set to 10kHz. In each voltage self-balancing module, the values of the first DC capacitor C p0 , the second DC capacitor C n0 , and the output capacitor C o0 are all 1mF, the values of the first resonant capacitor C rp0 and the second resonant capacitor C rn0 are all 50uF, and the values of the first resonant inductor L rp0 and the second resonant inductor L rn0 are all 20uH.
[0103] Table 1 Simulation parameters of DC transformer
[0104]
[0105] Figure 6 The simulation waveforms of the 3RSC-0 module connected to the input side are shown, irp0 and i rn0 are the current waveforms of the resonance circuit p and the resonance circuit n respectively, v rp0 and v rn0 are the voltage waveforms of the first resonance capacitor C rp0 and the second resonance capacitor C rn0 , v Co0 , v Cp0 , v Cn0 are the voltages of the output capacitor, the first DC capacitor and the second DC capacitor in the 3RSC-0 module respectively. Figure 6 It can be seen that the waveforms of i rp0 and i rn0 are complementary, and energy is transferred to the output capacitor C 0x in turn, and the voltages of the output capacitor, the first DC capacitor and the second DC capacitor are all stabilized at 2kV, proving that the voltage self-balancing module 3RSC has good voltage self-balancing capability.
[0106] In the Figure 7 , V i1 ~V i4 are the primary side voltages of the four modules 3RSC-1~3RSC-4, and it can be seen that the primary side voltages of V i1 ~V i4 are all stabilized at 7.25kV. In this topology, the voltage sum of the primary side voltages of all the 3RSC modules is 7.25x4+6=35kV, that is, the high-voltage side voltage V dc2 achieves an output of 35kV.
[0107] It can be known from the above analysis that in the modular DC transformer provided by the embodiment of the application, voltage automatic balancing can be achieved in the voltage self-balancing module, and voltage balancing between modules can be achieved between the transfer modules, so that the modular DC transformer provided by the application can conveniently achieve voltage balancing, reduces the difficulty of voltage balancing, improves the energy transmission efficiency, and solves the problem of complex voltage balancing existing in the existing modular DC transformer.
[0108] Referring to Figure 8 , the embodiment of the application further provides a control system, which comprises a controller 1 and a modular DC transformer 2 as any one of the above embodiments.
[0109] The controller 1 is connected with the DAB module 23 and the voltage self-balancing module 22 in the modular DC transformer 2 respectively.
[0110] It should be noted that the controller 1 is connected with the switching devices in the full bridge of the DAB module 23, for controlling the on-off of the switching devices in the DAB module 23. In actual application, the controller 1 can output control signals to the DAB module 23 and the voltage self-balancing module 22 respectively, so as to adjust the output voltage of the DAB module 23 and the working mode of the voltage self-balancing module 22.
[0111] In one specific embodiment, the controller 1 is connected with the first half-bridge sub-module, the second half-bridge sub-module and the third half-bridge sub-module in the voltage self-balancing module 22.
[0112] It should be noted that in actual application, the controller 1 is connected with the control terminals of the semiconductor power switching devices in the first half-bridge sub-module to the third half-bridge sub-module, so that the semiconductor power switching devices can be alternately turned on by outputting driving signals to the control terminals of the semiconductor power switching devices, so that the voltage self-balancing module alternately operates in the two working modes.
[0113] When the semiconductor power switching devices are IGBT tubes, the control terminals of the semiconductor power switching devices are gates.
[0114] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described system, device and unit can refer to the corresponding processes in the foregoing method embodiments, which will not be described here.
[0115] The terms "first", "second", "third", "fourth" and the like in the description of the application and the above drawings, if any, are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion.
[0116] It should also be noted that in the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.
[0117] The above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalent features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims
1. A modular DC transformer, characterized by The voltage self-balancing module comprises at least two voltage self-balancing modules and at least one DAB module; One of the voltage self-balancing modules is used as an input module, and a primary port of the input module is connected to a low-voltage side, and a secondary port of the input module is connected to the DAB module in parallel; A voltage self-balancing module other than the input module is used as a transfer module, a primary port of the transfer module is connected to a primary port of the input module in series, and is used to be connected to a high-voltage side; and a secondary port of the transfer module is connected to the DAB module; The voltage self-balancing module is used to balance the voltage inside the voltage self-balancing module; The voltage self-balancing module comprises a voltage balancing component, a first DC capacitor, a second DC capacitor and an output capacitor; The first DC capacitor, the second DC capacitor and the output capacitor are connected in series to form the primary port, and two ends of the output capacitor are the secondary port; The voltage balancing component is connected to two ends of the first DC capacitor, two ends of the output capacitor and two ends of the second DC capacitor respectively, and is used to balance the voltage of the first DC capacitor, the voltage of the second DC capacitor and the voltage of the output capacitor; The voltage balancing component comprises a first resonant branch, a second resonant branch, a first half-bridge sub-module, a second half-bridge sub-module and a third half-bridge sub-module; The first half-bridge sub-module is connected to the first DC capacitor in parallel; The second half-bridge sub-module is connected to the output capacitor in parallel; The third half-bridge sub-module is connected to the second DC capacitor in parallel; The first half-bridge sub-module, the second half-bridge sub-module and the third half-bridge sub-module are connected in series; The first resonant branch is connected to the first half-bridge sub-module and the second half-bridge sub-module respectively; The second resonant branch is connected to the second half-bridge sub-module and the third half-bridge sub-module respectively.
2. The modular DC transformer of claim 1, wherein, The first resonant branch comprises a first resonant inductor and a first resonant capacitor, and one end of the first resonant inductor and one end of the first resonant capacitor are connected in series; The other end of the first resonant capacitor is connected to the first half-bridge sub-module; The other end of the first resonant inductor is connected to the second half-bridge sub-module.
3. The modular DC transformer of claim 2, wherein, The second resonant branch comprises a second resonant inductor and a second resonant capacitor, and one end of the second resonant inductor and one end of the second resonant capacitor are connected in series; The other end of the second resonant capacitor is connected to the second half-bridge sub-module; The other end of the second resonant inductor is connected to the third half-bridge sub-module.
4. The modular DC transformer of claim 3, wherein, The first half-bridge sub-module comprises a first semiconductor power switching device and a second semiconductor power switching device; The first end of the first semiconductor power switching device is connected to one end of the first DC capacitor, and the second end of the first semiconductor power switching device is connected to the other end of the first resonant capacitor and the first end of the second semiconductor power switching device respectively; The second end of the second semiconductor power switching device is connected to the second half-bridge sub-module and the other end of the first DC capacitor respectively.
5. The modular DC transformer of claim 4, wherein, The second half-bridge sub-module comprises a third semiconductor power switching device and a fourth semiconductor power switching device; The first end of the third semiconductor power switch device is connected with one end of the output capacitor and the second end of the second semiconductor power switch device respectively; the second end of the third semiconductor power switch device is connected with the other end of the first resonant inductor, the other end of the second resonant capacitor and the first end of the fourth semiconductor power switch device respectively; The second end of the fourth semiconductor power switch device is connected with the third half-bridge sub-module and the other end of the output capacitor respectively.
6. The modular DC transformer of claim 5, wherein, The third half-bridge sub-module comprises a fifth semiconductor power switch device and a sixth semiconductor power switch device; The first end of the fifth semiconductor power switch device is connected with one end of the second DC capacitor and the second end of the fourth semiconductor power switch device respectively; the second end of the fifth semiconductor power switch device is connected with the other end of the second resonant inductor and the first end of the sixth semiconductor power switch device respectively; The second end of the sixth semiconductor power switch device is connected with the other end of the second DC capacitor.
7. A control system characterized by, The controller is connected with the DAB module and the voltage self-balancing module in the modular DC transformer. The controller is connected with the first half-bridge sub-module, the second half-bridge sub-module and the third half-bridge sub-module in the voltage self-balancing module.
8. The control system of claim 7, wherein,