Distributed control of hot-swap control device and method for multiple active bridge transformer submodules

Abstract

This application provides a distributed control device and method for hot-plugging multiple active bridge transformer submodules, comprising: a resistor divider circuit electrically connected to a high-frequency AC bus, used to convert the high-frequency AC bus voltage into a 0-5V divided voltage signal; a voltage comparator electrically connected to the output of the resistor divider circuit, comparing the divided voltage signal with a set reference potential and outputting high and low level digital signals; a DSP controller electrically connected to the voltage comparator, which sets a phase qualification flag when the phase difference between the local counter and the zero-phase reference t0 is less than a phase threshold; and a transformer submodule electrically connected to the DSP controller, which controls an AC relay to close to connect to the high-frequency AC bus when it receives the phase qualification flag from the DSP controller. This invention addresses the problems of related technologies that often employ centralized control, over-reliance on a central controller, and limitations in computing power and flexibility, especially as the number of modules increases.

Description

Technical Field

[0001] This invention relates to the field of DC power distribution network control technology, specifically to a distributed control device and method for hot-plugging multiple active bridge transformer submodules. Background Technology

[0002] Hot-swapping capability allows power modules to be added or removed from a system without shutting it down, significantly improving flexibility and scalability. This has become a common research hotspot in fields such as new energy, data centers, and DC grids. The term "Plug-and-Play" (PnP) originated in computer networks, referring to devices that could operate automatically without manual configuration after being connected. This concept is now being applied to power electronic systems: distributed power sources, energy storage units, or power electronic converters should be able to be connected and powered instantly, like a USB flash drive.

[0003] In DC distribution networks, the Multi-Active-Bridge (MAB) transformer is a typical isolated multi-port DC / DC topology. Traditional solutions rely on a single multi-winding high-frequency transformer to couple all ports. However, the transformer windings are fixed, and the number of ports and voltage levels are difficult to change once the design is finalized, hindering standardization and capacity expansion. To address this, a common high-frequency bus MAB (HFT-MAB) structure has been proposed: the centralized multi-winding transformer is split into multiple standardized dual-winding high-frequency transformers (HFTs). The primary side of each HFT is uniformly connected to a common high-frequency AC bus, while the secondary side can be independently connected to any DC port via an H-bridge. This topology transforms "power coupling" into a "high-frequency bus interface," offering high modularity and naturally suited for hot-swappable operation.

[0004] Related technologies propose a distributed control strategy for MAB (Multi-Module Block): each submodule adaptively adjusts its PWM frequency based solely on local voltage and current information, and the global frequency automatically synchronizes in steady state. Power and frequency exhibit a linear droop relationship, achieving power sharing without communication and capacitor voltage balance. This method lays the control foundation for "plug-and-play," but the authors explicitly point out that "distributed startup / online hot-swapping" remains a gap—existing research assumes all modules are powered on synchronously, but in practical engineering, it is often necessary to put a module into operation or remove it without shutting down the system.

[0005] Related technologies have proposed an "online replacement" scheme for HFT-MAB submodules, which uses redundant modules to replace faulty units and maintain system operation. Essentially, this is close to hot-swapping, but it relies on a central controller for unified scheduling, resulting in complex communication and limited scalability. To date, no in-depth research has been conducted on submodule hot-swapping methods based on high-frequency AC buses and fully distributed control. In summary, research on distributed hot-swapping in HFT-MAB is still in its early stages, but it possesses significant engineering value and development potential.

[0006] Existing HFB-MAB control methods mostly employ centralized control, which, while effectively managing multiple objectives, relies excessively on a central controller. This dependence becomes particularly pronounced with increasing module numbers, leading to limitations in computational power and flexibility. Distributed control methods, by allocating computation to local controllers in each module, effectively improve adaptability, flexibility, and fault tolerance, reducing reliance on a single controller. This facilitates multi-module expansion control of HFB-MAB, requiring the design of a distributed control-based hot-swap submodule control method to achieve smooth system integration, enhance the flexibility and robustness of HFB-MAB, and ensure its reliable operation as an energy exchange hub. However, no literature reports on this area yet, while practical engineering often requires modules to be added or removed without system shutdown. Therefore, the hot-swap submodule method proposed in this patent has significant application potential. Summary of the Invention

[0007] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a distributed control device and method for hot-plugging multiple active bridge transformer submodules. This solves the problem that existing HFB-MAB control methods mostly adopt centralized control, which can effectively manage multiple objectives, but relies excessively on the central controller. In particular, as the number of modules increases, there are problems such as limited computing power and flexibility.

[0008] To achieve the above-mentioned technical objectives, in a first aspect, the present invention provides a distributed control multi-active bridge transformer submodule hot-swap control device, comprising:

[0009] A resistor voltage divider circuit is electrically connected to the high-frequency AC bus. The resistor voltage divider circuit is used to convert the high-frequency AC bus voltage into a voltage signal after voltage division of 0~5V.

[0010] A voltage comparator is electrically connected to the output terminal of the resistor voltage divider circuit. The voltage comparator is set with a reference voltage. The voltage signal after voltage division is input to the non-inverting input terminal IN+ of the voltage comparator and compared with the set reference potential. The comparator outputs high and low level digital signals.

[0011] The DSP controller is electrically connected to the voltage comparator. The DSP controller performs double-edge sampling on the high and low level digital signals and simultaneously obtains the bus period Tb and the zero-phase reference t0 within one clock cycle. The local PWM period is calibrated in real time with the bus period Tb as feedback. When the phase difference between the local counter and the zero-phase reference t0 is detected to be less than the phase threshold, the phase qualified flag is set.

[0012] The transformer submodule is electrically connected to the DSP controller and to the high-frequency AC bus via an AC relay. When it receives a phase qualification flag from the DSP controller, it controls the AC relay to close to connect to the high-frequency AC bus.

[0013] Compared with the prior art, the beneficial effects of the present invention include:

[0014] This invention proposes a hardware and software integrated solution of "distributed control + hot-plugging", and proposes a "plug-and-play" method for implementing sub-modules based on distributed control of HFB-MAB, which improves the maintainability of HFB-MAB and ensures its operational reliability as an energy exchange hub, and has high engineering value and development potential.

[0015] 1. High reliability:

[0016] Traditional centralized hot-swap strategies rely on a central controller for unified scheduling. If communication is blocked or the main controller is overloaded, the entire bus may lose synchronization. This solution decentralizes the high-frequency pre-synchronization judgment algorithm to the independent DSPs of each submodule. Hot-swap detection and judgment can be completed with only local voltage division sampling and eCAP capture. There is no need for communication between the control modules, which significantly improves the maintainability and operational reliability of the system.

[0017] 2. Low cost and highly versatile:

[0018] This invention requires only voltage divider resistors, a high-speed comparator, and a built-in eCAP in the DSP, without the need for an additional high-speed signal acquisition unit or redundant power supply; the software utilizes the DSP's readily available enhanced capture module functionality, ensuring high compatibility.

[0019] 3. Simple to control:

[0020] While existing online access designs improve system reliability to some extent, their centralized control increases system complexity. This invention, based on distributed control principles, eliminates the need for complex redundant module switching logic, thus simplifying the system's control structure and improving its operability and maintainability.

[0021] According to some embodiments of the present invention, the transformer submodule includes a current source submodule and a voltage source submodule.

[0022] According to some embodiments of the present invention, the current source submodule includes:

[0023] A cascaded H-bridge converter and a high-frequency transformer are interconnected on the high-voltage side of the high-frequency transformer via a high-frequency AC bus. An AC contactor is configured at the connection point between the high-frequency transformer and the high-frequency AC bus. The AC contactor is used to control the access and disconnection of the current source submodule.

[0024] A capacitor C is connected in parallel on the DC side of the H-bridge converter, and a DC contactor and a charging resistor are connected between the capacitor and the DC port.

[0025] The DC terminal of the current source submodule includes: renewable energy, active or passive load, and the external DC terminal is used to inject or absorb active power into the internal module.

[0026] According to some embodiments of the present invention, the voltage source submodule includes:

[0027] A cascaded H-bridge converter and a high-frequency transformer are interconnected on the high-voltage side of the high-frequency transformer via a high-frequency AC bus. An AC contactor is configured at the connection point between the high-frequency transformer and the high-frequency AC bus. The AC contactor is used to control the access and disconnection of the current source submodule.

[0028] A capacitor C is connected in parallel on the DC side of the H-bridge converter, and a DC contactor and a charging resistor are connected between the capacitor and the DC port.

[0029] The DC terminal of the voltage source submodule is powered by a constant voltage source.

[0030] According to some embodiments of the present invention, the DC power supply method of the voltage source submodule includes:

[0031] Energy storage systems, DC microgrids, or PWM rectifiers with DC voltage control.

[0032] According to some embodiments of the present invention, the resistor voltage divider circuit is composed of a voltage divider resistor R1 and an output resistor R2 connected in series, and the voltage signal Uout after voltage division satisfies: Uout = Uac × R2 / (R1+R2), where Uac is the voltage of the high-frequency AC bus.

[0033] Secondly, the present invention provides a distributed control method for hot-plugging multiple active bridge transformer submodules, applied to a distributed control method for hot-plugging multiple active bridge transformer submodules as described in any one of the first aspects, the method comprising the steps of:

[0034] The voltage divider network samples the high-frequency bus voltage in real time and converts the high-frequency bus voltage into a voltage signal after voltage division from 0 to 5V.

[0035] The high-speed comparator completes the analog-to-digital conversion, inputs the voltage signal after voltage division to the non-inverting input terminal IN+ of the voltage comparator, compares it with the set reference potential, and outputs high and low level digital signals.

[0036] The DSP controller captures both edges, extracts the bus frequency and phase, and generates a zero-phase-difference synchronous control reference.

[0037] Select the hot-swap scheme for the submodule according to the type of transformer submodule, and control the AC relay to close to connect to the high-frequency AC bus.

[0038] According to some embodiments of the present invention, selecting a hot-swap scheme for a submodule based on the transformer submodule type includes the following steps:

[0039] When the transformer submodule is a current source submodule, the hot-swap solution for the current source submodule is as follows:

[0040] Close the AC contactor to precharge the DC capacitor through the uncontrolled rectifier circuit;

[0041] After closing the DC relay and implementing high-frequency pre-synchronization control, connect it to the bus.

[0042] Implement constant voltage control to enter steady-state operation.

[0043] According to some embodiments of the present invention, selecting a hot-swap scheme for a submodule based on the transformer submodule type includes the following steps:

[0044] When the transformer submodule is a voltage source submodule, the hot-swap solution for the voltage source submodule is as follows:

[0045] Connect the DC constant voltage source and close the AC contactor;

[0046] Close the DC relay, first implement zero-power high-frequency pre-synchronization before connecting to the bus, and then gradually change the droop coefficient to smoothly increase the power;

[0047] Implement power droop control to enter steady-state operation.

[0048] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0049] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, wherein the abstract drawings are to be completely consistent with one of the drawings in the specification:

[0050] Figure 1 A structural diagram of a four-module multi-active bridge DC transformer based on distributed control is provided for one embodiment of the present invention;

[0051] Figure 2 (a) VS submodule control block diagram and (b) CS submodule control block diagram are provided for one embodiment of the present invention.

[0052] Figure 3 This is a schematic diagram of a current source submodule provided in one embodiment of the present invention;

[0053] Figure 4 A capacitor charging process diagram provided for one embodiment of the present invention: a) UAC is positive, b) UAC is negative;

[0054] Figure 5 This is a schematic diagram of a voltage source submodule provided in one embodiment of the present invention. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0056] It should be noted that although functional modules are divided in the system diagram and the logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than the module division in the system or the order in the flowchart. The terms "first," "second," etc., in the specification, claims, and the aforementioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0057] Reference Figures 1 to 5 , Figure 1 A structural diagram of a four-module multi-active bridge DC transformer based on distributed control is provided for one embodiment of the present invention; Figure 2 (a) VS submodule control block diagram and (b) CS submodule control block diagram are provided for one embodiment of the present invention. Figure 3 This is a schematic diagram of a current source submodule provided in one embodiment of the present invention; Figure 4 A capacitor charging process diagram provided for one embodiment of the present invention: a) UAC is positive, b) UAC is negative; Figure 5 This is a schematic diagram of a voltage source submodule provided in one embodiment of the present invention.

[0058] In one embodiment, the distributed control multi-active bridge transformer submodule hot-swap control device includes: a resistor voltage divider circuit electrically connected to the high-frequency AC bus, which converts the high-frequency AC bus voltage into a 0~5V divided voltage signal; a voltage comparator electrically connected to the output terminal of the resistor voltage divider circuit, which is set with a reference voltage, inputs the divided voltage signal to the non-inverting input terminal IN+ of the voltage comparator, compares it with the set reference potential, and outputs high and low level digital signals; a DSP controller electrically connected to the voltage comparator, which performs double-edge sampling on the high and low level digital signals, and simultaneously obtains the bus period Tb and the zero-phase reference t0 within one clock cycle; uses the bus period Tb as feedback to calibrate the local PWM period in real time, and sets a phase qualified flag when the phase difference between the local counter and the zero-phase reference t0 is less than the phase threshold; and a transformer submodule electrically connected to the DSP controller and electrically connected to the high-frequency AC bus through an AC relay, which controls the AC relay to close to connect to the high-frequency AC bus when it receives the phase qualified flag from the DSP controller.

[0059] 1. Common high-frequency bus multi-active bridge DC-DC converter and distributed control principle:

[0060] like Figure 1 The topology is a four-active-bridge DC-FT DC-FT with a common high-frequency bus based on distributed control. Each sub-module consists of an H-bridge converter and a high-frequency transformer (HFT) cascaded together. L is the equivalent leakage inductance of the high-frequency transformer. The HFTs are interconnected on the high-voltage side via a high-frequency AC bus, and an AC contactor acKM is configured at the connection point to control the access and disconnection of the modules. A capacitor C is connected in parallel on the DC side of the H-bridge. Between the capacitor and the DC port are a DC contactor dcKM and a charging resistor. The function of the contactor is to control the connection and charging of the DC side and the external port. The charging resistor can act as a buffer to reduce the transient impact of the current during the charging process on the DC side.

[0061] Based on the characteristics of their DC terminals, the submodules can be divided into voltage source (VS) submodules and current source (CS) submodules. The DC terminal of the VS submodule is powered by a constant voltage source, such as an energy storage system, a DC microgrid, or a PWM rectifier with DC voltage control. Therefore, it does not require DC voltage regulation. The VS submodules collectively form the high-frequency AC bus grid of the DC transformer. The DC terminal of the CS submodule includes connections to renewable energy sources (such as solar photovoltaic and wind turbines), active and passive loads, etc. A certain amount of active power is injected into or absorbed from the DC terminal from external sources; therefore, the load port needs to be able to maintain the DC terminal voltage.

[0062] according to Figure 1 As shown in the diagram, submodules 1 and 2 are VS submodules, and submodules 3 and 4 are CS submodules. To ensure the active power balance of the system, the power of each submodule must satisfy...

[0063]

[0064] And the power transmission between modules x and y satisfies

[0065]

[0066] Where u x , u y L represents the DC-side voltage of modules x and y. xy f is the equivalent inductance between modules x and y. s d is the switching frequency. xy The shift ratio between modules x and y has a value range of (-0.5, +0.5). Meanwhile, for the high-frequency AC bus connected to the sub-module, its voltage expression is...

[0067]

[0068] u hx For the H-bridge AC side voltage of submodule x, see Figure 1 As shown, where M is

[0069]

[0070] Figure 2(a) is a block diagram of the power droop control for the VS submodule of the multi-active bridge transformer. Each VS submodule is controlled by a droop coefficient m. x Determine the power ratio of the steady-state power supply port, and adaptively adjust the module switching frequency f according to equation (5). x .

[0071]

[0072] P x Let P be the instantaneous DC power of submodule x, which is equal to the product of the instantaneous DC voltage and the instantaneous current, i.e., P. x =u x *i x f ref It is the nominal switching frequency, and τ is the time constant of the low-pass filter, used to reduce the measured P x High-frequency ripple. m x It is a proportional gain that is inversely proportional to the power output of each power port. The frequency control output signal f is calculated. x Then, the pulse signal g of the four switching transistors of this submodule is obtained by inputting it into a variable PWM modulation module with a duty cycle of 50%. x1 ~g x4 This enables dynamic adjustment of the phase angle of the high-frequency AC voltage. When the multi-active bridge transformer is in a stable state, the switching frequencies of all sub-modules will be synchronized.

[0073] Figure 2(b) is the control block diagram of the CS submodule. Since the DC terminal voltage of the CS submodule is affected by the external circuit, it is necessary to measure and control the DC voltage at the port. The switching frequency is calculated as shown in equation (6):

[0074]

[0075] Where, k p k i For the proportional and integral gain of the PI controller, u y U is the port voltage of module y. refyf is the voltage reference value. ref f is the nominal switching frequency. y This is the switching frequency of the module.

[0076] In one embodiment, the distributed control method for hot-plugging multiple active bridge transformer submodules is applied to the distributed control device for hot-plugging multiple active bridge transformer submodules as described above. The method includes the following steps: a voltage divider network samples the high-frequency bus voltage in real time and converts the high-frequency bus voltage into a voltage signal after voltage division from 0 to 5V; a high-speed comparator performs analog-to-digital conversion, inputs the voltage signal after voltage division to the non-inverting input terminal IN+ of the voltage comparator, compares it with the set reference potential, and outputs high and low level digital signals; the DSP controller captures both edges, extracts the bus frequency and phase, and generates a zero-phase-difference synchronous frequency control reference; a submodule hot-plugging scheme is selected according to the transformer submodule type, and the AC relay is closed to connect to the high-frequency AC bus.

[0077] Select the hot-swap scheme for the transformer submodule based on its type, including the following steps: When the transformer submodule is a current source submodule, the hot-swap scheme for the current source submodule is as follows: Close the AC contactor and precharge the DC capacitor through the uncontrolled rectifier circuit; close the DC relay, implement high-frequency pre-synchronization control, and then connect it to the bus; implement constant voltage control and enter steady-state operation.

[0078] The hot-swap scheme for the transformer submodule is selected according to the type of the transformer submodule, including the following steps: When the transformer submodule is a voltage source submodule, the hot-swap scheme for the voltage source submodule is as follows: the DC side constant voltage source is connected, and the AC contactor is closed; the DC relay is closed, zero-power high-frequency pre-synchronization is first implemented and then connected to the bus, and then the droop coefficient is gradually changed to smoothly increase the power; power droop control is implemented to enter steady-state operation.

[0079] The hot-plugging method for submodules proposed in this patent involves keeping the system's high-frequency AC bus energized and smoothly connecting submodules that are in a shutdown state to the system after pre-charging. The challenge in hot-plugging control of multi-active bridge DC transformers lies in how to quickly achieve high-frequency synchronization, reduce transient impacts during connection, and simultaneously complete precise power allocation across all ports within a short time.

[0080] Specifically, on the one hand, the frequency-adaptive distributed control strategy can achieve precise power allocation, but this method requires high accuracy in voltage and current sampling; on the other hand, by reducing the frequency and phase deviation when submodules are connected, transient impacts can be significantly reduced, and reasonable control parameter design can further improve the system response speed and enhance the stability of the connection process.

[0081] Therefore, this paper proposes a general framework for high-frequency synchronous detection, which is further refined into two hot-plug schemes based on port characteristics: current source type (CS) and voltage source type (VS), as detailed below.

[0082] The general steps for high-frequency synchronization are as follows:

[0083] S1: Voltage divider network samples high-frequency bus voltage in real time;

[0084] S2: The high-speed comparator completes the analog-to-digital conversion and outputs a digital square wave signal;

[0085] S3: eCAP double-edge capture, extracts bus frequency and phase, and generates zero-phase-difference co-frequency control reference.

[0086] The hot-swap solution for the current source submodule is as follows:

[0087] S31: Close the AC contactor to precharge the DC capacitor through the uncontrolled rectifier circuit;

[0088] S32: Close the DC relay and connect to the bus after implementing high-frequency pre-synchronization control;

[0089] S33: Implement constant voltage control and enter steady-state operation.

[0090] The voltage source submodule hot-swap solution is as follows:

[0091] S34: DC side constant voltage source connected, close AC contactor.

[0092] S35: Close the DC relay, first implement zero-power high-frequency pre-synchronization, then connect to the bus, and then gradually change the droop coefficient to smoothly increase the power;

[0093] S36: Implement power droop control and enter steady-state operation.

[0094] 2. Hot-swap control method:

[0095] Related technologies describe the scenario of random access of multiple active bridge submodules under distributed control, which may result in large transient oscillations. This is because the initial phase angle is a random value, and the offset can be very large. As mentioned above, this situation leads to a very large instantaneous value of transmitted energy during access, and the control parameters designed under small-signal analysis may be unsuitable. According to research, there is currently no hot-plugging method for MAB or HFB-MAB based on distributed control. In addition to introducing the hot-plugging method proposed in this patent, the following section will also compare the impact of random access (without hot-plugging control) and the use of hot-plugging control on the system experimentally.

[0096] The hot-plug control method proposed in this patent is for use in HFB-MAB systems under distributed control during operation, so as to enable non-running sub-modules to be smoothly started and connected to the system without causing large transient impacts on running sub-modules.

[0097] As can be seen from the distributed control mechanism, each submodule adopts distributed control, and its control output is a frequency-converted PWM wave with a 50% duty cycle related to the nominal frequency, which is used to drive the H-bridge of the submodule. During the stable operation of the system, the high-frequency bus voltage can be approximated as a square wave with a 50% duty cycle at the corresponding operating frequency. According to equation (2), if there is a large phase shift angle between the conduction signal of the H-bridge forward path and the high-frequency bus voltage when the submodule is put into operation, it will cause a significant instantaneous power exchange between the high-frequency bus and the connected submodule. This transient power impact will not only damage the connected submodule itself, but may also affect other normally operating modules through AC bus coupling, causing voltage and current fluctuations, and even interfering with the overall stability of the system.

[0098] Therefore, for distributed control of multi-active bridge transformers with a common high-frequency bus, one of the challenges in ensuring smooth connection of submodules to the system without affecting operating modules is ensuring that the phase shift angle and frequency of the gate signal in the H-bridge forward path are sufficiently small and consistent with the high-frequency bus voltage at the moment of connection. To achieve this, the hot-plug function needs to perform high-speed sampling of the bus voltage in hardware and extract the bus frequency and phase in real time in software, thereby generating a gate drive signal that is nearly in phase and frequency with the bus.

[0099] 2.1 Hardware Implementation of Hot-Plug Control Method and High-Frequency Synchronization Scheme

[0100] The main hardware involved in the hot-plug control of this patent is as follows: Figure 3 As shown, its main function is to compare the phase difference between the high-frequency AC bus and the PWM signal generated by the DSP of the access module. The specific functions are shown in S1~S3 below. When the frequency of the PWM signal of the switching transistor is close and the phase difference is small, it means that the PWM signal of the module is basically synchronized with the high-frequency bus voltage. This is conducive to the smooth access of the module to the system, avoiding a large impact on the system and maintaining the stable operation of the system.

[0101] The specific method for hot-plug detection is as follows:

[0102] S1: Bus voltage acquisition

[0103] First, the high-frequency AC bus voltage is converted into a 0~5V voltage signal using a resistor voltage divider circuit. The resistor voltage divider circuit is shown in the figure, and it can be equivalent to a series connection of voltage divider resistor R1 and output resistor R2.

[0104] The voltage U after voltage division out It can be represented as:

[0105]

[0106] S2: Analog-to-digital conversion

[0107] The voltage signal (analog signal) after voltage division is input to the non-inverting input terminal IN+ of the voltage comparator and compared with the set reference potential. The comparator outputs a high-level digital signal when the input voltage is greater than the reference potential and a low-level signal when the input voltage is less than the reference potential.

[0108] By converting the high-frequency bus voltage into a square wave digital signal of 0 or 5V and inputting it into the DSP controller, the frequency and phase of the bus voltage can be quickly identified through the enhanced capture module eCAP. See step S3 for the specific working principle.

[0109] S3: Digital Signal Processing

[0110] When the eCAP module of the DSP controller is in capture mode, it can automatically latch a 32-bit time base counter value at each valid edge of the input digital signal, thereby extracting all time attributes: the time difference between two consecutive rising edges gives the signal period, and the time difference between the falling edge and the rising edge within the same period gives the high-level width. Dividing the two gives the duty cycle. Using this mechanism, double-edge sampling of the high-frequency bus voltage digital signal can simultaneously obtain the bus period Tb and the zero-phase reference t0 within one clock cycle. The high-frequency synchronization software algorithm uses Tb as feedback to calibrate the local PWM period in real time. When it detects that the phase difference |Δθ| between the local counter and t0 is less than ε, it immediately sets the "phase qualified" flag and loads the pre-calculated H-bridge forward path duty cycle and period into the PWM generation module in the next cycle, realizing shockless hot-plugging with the same frequency and phase as the bus.

[0111] The above hot-plug detection scheme is applicable to the high-frequency synchronization steps in the current source submodule and voltage source submodule described below.

[0112] 2.2 Hot-swap control scheme for current source submodule

[0113] S31: Close AC relay, DC port capacitor pre-charged.

[0114] The DC side of the CS submodule is connected to an external load, and the bus voltage must be stabilized at a set value during operation. However, before being connected to the system, the internal capacitor voltage is zero. If the AC contactor acKM is closed directly, the huge voltage difference will induce a surge current on the switching transistor, instantly damaging the device. Therefore, a "pre-charge" process is performed first: the full-bridge four transistors S1 to S4 are locked, and an uncontrolled rectifier bridge is formed using the internal diodes VD1 to VD4. The high-frequency bus charges the DC capacitor unidirectionally through the isolation transformer and the diode bridge, forming a "high-frequency bus → transformer → VD1 to VD4 → capacitor" loop. At the same time, the capacitor voltage is controlled by a pre-charge resistor connected in series at the external port (e.g., Figure 3 The external bus voltage is buffered at dcKM to ensure that the voltage difference between the two sides is small enough before the DC contactor closes, thereby reducing the impact of the closing current.

[0115] like Figure 3 The high-frequency bus voltage can be regarded as an AC square wave with a duty cycle of 50%. ac The amplitude is U h The frequency is f, and the period is T = 1 / f. Assume the bus voltage is +U during the positive half-cycle (0 ~ T / 2). h During the negative half-cycle (T / 2~T), it is −U h The DC port capacitor of the unstarted module is C, the transformer turns ratio is n=1:N3, and the diode forward voltage drop is U. f The current flowing through the capacitor is i dc The capacitor voltage is u dc .

[0116] like Figure 4 From 0 to T / 2, the current flows through VD1 and VD4 to form a rectified current. From T / 2 to T, the current flows through VD2 and VD3 to form a rectified current. In both the positive and negative half-cycles, the current charges the capacitor after being rectified by the diodes. The capacitor voltage u... dc As it gradually increases over time, it can be expressed as:

[0117]

[0118] Capacitor current can be expressed as

[0119]

[0120] The simultaneous equations yield the following results:

[0121]

[0122] We can solve for:

[0123]

[0124] At the start of charging, the capacitor voltage u dc0 Initially zero, the capacitor voltage gradually increases as charging progresses. Due to uncontrolled rectification, the capacitor voltage will eventually approach U. h / n-2U f .

[0125] S32: Connection of DC contactor and high-frequency pre-synchronization control

[0126] After the DC capacitor is pre-charged, the DC relay is closed, and the controller enters the "high-frequency pre-synchronization" stage (see steps S31-S33 for the working principle). S33: Connection complete.

[0127] Immediately after pre-synchronization, a constant voltage closed loop is engaged to achieve seamless connection of the CS submodule to the common high-frequency bus, thus ending the hot-plugging process.

[0128] 2.4 Voltage Source Submodule Hot-Swapping Control Scheme

[0129] S34: DC side constant voltage source connected, AC contactor closed.

[0130] Unlike the current source (CS) submodule, the voltage source (VS) submodule connects to a constant voltage source (energy storage, DC microgrid, or voltage-controlled PWM rectifier) ​​on its DC side. It does not require further DC voltage regulation and instead supports the high-frequency AC bus voltage along with other VS submodules. Before connection, a stable and voltage-matched constant voltage source must be connected in parallel on the DC side. Its value should be equal to or slightly higher than "high-frequency bus voltage amplitude × transformer turns ratio". The reason is as follows:

[0131] After the AC contactor is closed (as shown in Figure 5 acKM2), S1 to S4 remain locked, and the busbar charges the capacitor through the uncontrolled rectifier formed by VD1 to VD4. Since there is a pre-charging resistor in series between the capacitor and the external port, the voltage difference between the constant voltage source at the external port and the DC side of the H bridge will all fall on the resistor and the capacitor.

[0132] If the external voltage is lower than the matching voltage, the uncontrolled rectifier will conduct in the forward direction. The greater the voltage difference, the greater the diode current. The constant voltage source will be forced to absorb power, which may trigger the protection.

[0133] If the external voltage is higher than the matching voltage, the diode reverse blocks, there is no return path, the current is zero, and the power cannot be returned.

[0134] Therefore, before connecting, the constant voltage source voltage should be adjusted to be equal to or slightly higher than "high frequency bus voltage amplitude × transformer turns ratio" to ensure that the diode is always turned off with zero current.

[0135] S35: DC relay, zero-power high-frequency pre-synchronization connection, and smooth power regulation.

[0136] Unlike the CS submodule, the VS submodule adopts distributed droop control. Each VS submodule supports the high-frequency bus voltage and distributes power equally according to capacity ratio. Therefore, special attention should be paid to the power structure redistribution when a new VS submodule is connected to prevent its instantaneous high power demand from causing drastic adjustments in the other VS submodules. As can be seen from equation (5), the droop coefficient m is inversely proportional to the port output power. In order to suppress the connection impact to zero, the m of the module to be connected is temporarily increased first, so that its reference power approaches zero. After pre-synchronization and closing, m is slowly restored to the rated value according to the predetermined slope to achieve a seamless transition of "zero power connection and smooth power adjustment".

[0137] S36: Connection complete

[0138] After pre-synchronization is completed, the droop coefficient is gradually adjusted to the rated value to achieve seamless connection of VS submodules to the common high-frequency bus and smooth adjustment of the power structure between each VS submodule, thus ending the hot-plugging process.

[0139] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the above embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of the present invention.

[0140] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A distributed control multi-active bridge transformer submodule hot-swap control device, characterized in that, include: A resistor voltage divider circuit is electrically connected to the high-frequency AC bus. The resistor voltage divider circuit is used to convert the high-frequency AC bus voltage into a voltage signal after voltage division of 0~5V. A voltage comparator is electrically connected to the output terminal of the resistor voltage divider circuit. The voltage comparator is set with a reference voltage. The voltage signal after voltage division is input to the non-inverting input terminal IN+ of the voltage comparator and compared with the set reference potential. The comparator outputs high and low level digital signals. The DSP controller is electrically connected to the voltage comparator. The DSP controller performs double-edge sampling on the high and low level digital signals and simultaneously obtains the bus period Tb and the zero-phase reference t0 within one clock cycle. The local PWM period is calibrated in real time with the bus period Tb as feedback. When the phase difference between the local counter and the zero-phase reference t0 is less than the phase threshold, the phase qualified flag is set. The transformer submodule is electrically connected to the DSP controller and to the high-frequency AC bus via an AC relay. When it receives a phase qualification flag from the DSP controller, it controls the AC relay to close to connect to the high-frequency AC bus.

2. The distributed control multi-active bridge transformer submodule hot-swap control device according to claim 1, characterized in that, The transformer submodule includes a current source submodule and a voltage source submodule.

3. The distributed control multi-active bridge transformer submodule hot-swap control device according to claim 2, characterized in that, The current source submodule includes: A cascaded H-bridge converter and a high-frequency transformer are interconnected on the high-voltage side of the high-frequency transformer via a high-frequency AC bus. An AC contactor is configured at the connection point between the high-frequency transformer and the high-frequency AC bus. The AC contactor is used to control the access and disconnection of the current source submodule. A capacitor C is connected in parallel on the DC side of the H-bridge converter, and a DC contactor and a charging resistor are connected between the capacitor and the DC port. The DC terminal of the current source submodule includes: renewable energy, active or passive load, and the external DC terminal is used to inject or absorb active power into the internal module.

4. The distributed control multi-active bridge transformer submodule hot-swap control device according to claim 3, characterized in that, The voltage source submodule includes: A cascaded H-bridge converter and a high-frequency transformer are interconnected on the high-voltage side of the high-frequency transformer via a high-frequency AC bus. An AC contactor is configured at the connection point between the high-frequency transformer and the high-frequency AC bus. The AC contactor is used to control the access and disconnection of the current source submodule. A capacitor C is connected in parallel on the DC side of the H-bridge converter, and a DC contactor and a charging resistor are connected between the capacitor and the DC port. The DC terminal of the voltage source submodule is powered by a constant voltage source.

5. The distributed control multi-active bridge transformer submodule hot-swap control device according to claim 4, characterized in that, The DC power supply method of the voltage source submodule includes: Energy storage systems, DC microgrids, or PWM rectifiers with DC voltage control.

6. The distributed control multi-active bridge transformer submodule hot-swap control device according to claim 1, characterized in that, The voltage divider circuit consists of a voltage divider resistor R1 and an output resistor R2 connected in series. The voltage signal Uout after voltage division satisfies: Uout = Uac × R2 / (R1+R2), where Uac is the voltage of the high-frequency AC bus.

7. A distributed control method for hot-plugging multiple active bridge transformer submodules, characterized in that, The method, applied to the distributed control multi-active bridge transformer submodule hot-swap control device as described in any one of claims 1 to 6, comprises the following steps: The voltage divider network samples the high-frequency bus voltage in real time and converts the high-frequency bus voltage into a voltage signal after voltage division from 0 to 5V. The high-speed comparator completes the analog-to-digital conversion, inputs the voltage signal after voltage division to the non-inverting input terminal IN+ of the voltage comparator, compares it with the set reference potential, and outputs high and low level digital signals. The DSP controller captures both edges, extracts the bus frequency and phase, and generates a zero-phase-difference synchronous control reference. Select the hot-swap scheme for the submodule according to the type of transformer submodule, and control the AC relay to close to connect to the high-frequency AC bus.

8. The distributed control method for hot-plugging multiple active bridge transformer submodules according to claim 7, characterized in that, Selecting a hot-swap solution for the submodule based on its type includes the following steps: When the transformer submodule is a current source submodule, the hot-swap solution for the current source submodule is as follows: Close the AC contactor to precharge the DC capacitor through the uncontrolled rectifier circuit; After closing the DC relay and implementing high-frequency pre-synchronization control, connect it to the bus. Implement constant voltage control to enter steady-state operation.

9. The distributed control method for hot-plugging multiple active bridge transformer submodules according to claim 7, characterized in that, Selecting a hot-swap solution for the submodule based on its type includes the following steps: When the transformer submodule is a voltage source submodule, the hot-swap solution for the voltage source submodule is as follows: Connect the DC constant voltage source and close the AC contactor; Close the DC relay, first implement zero-power high-frequency pre-synchronization before connecting to the bus, and then gradually change the droop coefficient to smoothly increase the power; Implement power droop control to enter steady-state operation.

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